A Review of Worldwide Strategies for Promoting High-Temperature Heat Pumps

Abstract

This paper provides a comprehensive overview of policies and incentives aimed at promoting high-temperature heat pumps (HTHPs) globally. It examines the various strategies employed by different countries to encourage the adoption of HTHPs, highlighting both the opportunities and the barriers encountered in these efforts. The analysis includes a review of financial incentives, regulatory measures, and technological initiatives designed to facilitate the integration of HTHPs into industrial applications. By describing different approaches across regions, this paper identifies best practices and potential pitfalls, offering a nuanced understanding of how different policy frameworks impact the deployment of HTHPs. Additionally, this paper explores the technological challenges that influence the effectiveness of these policies. The findings underscore the critical role of supportive policies in overcoming technical and economic barriers, ultimately fostering the widespread use of HTHPs as a viable solution for reducing industrial emissions and advancing global decarbonization goals. Furthermore, utilizing electricity from renewable energy sources (RESs), HTHPs can also contribute to grid stability by reducing electricity peaks. This aspect enhances the integration of RESs into the energy mix, creating a more resilient grid and optimizing energy consumption patterns in industrial applications.

1. Introduction

1.1. Setting the Context

Over the decades, numerous studies have documented the environmental impacts of climate change, including rising sea levels, increasing temperatures, more extreme weather events, and a higher incidence of droughts, flooding, and wildfires. These changes have led to significant health consequences for humans. Environmental alterations have been linked to a rise in infectious diseases, respiratory disorders, heat-related illnesses and deaths, undernutrition due to food insecurity, and adverse health outcomes stemming from increased sociopolitical tension and conflicts [1].

Furthermore, reducing dependence on fossil fuels is essential to mitigate global political and economic instability caused by their uneven geographical distribution. Many regions rich in fossil resources are also conflict zones, increasing the insecurity of supply for countries lacking energy independence. This reliance leads to fluctuations in fuel prices, destabilizing economies and political balances worldwide. For instance, in August 2022, the European Union (EU) experienced an unprecedented spike in gas prices, with increases of 1000% compared to previous decades. Over the past ten years, average gas prices ranged from 5 to 35 EUR/MWh, but in August 2022, Title Transfer Facility (TTF) derivative prices soared to a record high of 300 EUR/MWh, adversely affecting the EU economy [2].

However, the market price of fossil fuels does not fully account for the costs associated with their consumption. Due to this aspect, many national and subnational jurisdictions have implemented mechanisms to price pollutant emissions, aiming to address this discrepancy [3]. By implementing emissions pricing mechanisms, the cost of using polluting fuels increases, making them less attractive compared to greener alternatives. This approach ensures that the cost of emissions is directly attributed to the emitter. In 2022, this principle highlighted a troubling trend. Emissions reached a record high of 53.8 Gt CO₂eq, approximately 1.4% more than in 2021, making it the year with the highest level of recorded emissions. Around two-thirds of these emissions originated from just six countries: China (29.2%), the United States (11.2%), India (7.3%), the EU27 (6.7%), Russia (4.8%), and Brazil (2.4%), as shown in Figure 1a.

Figure 1b illustrates these emissions, highlighting that CO₂ is the predominant contaminant emitted by the six countries, except for Brazil, where methane accounts for about 51% of total emissions. Globally, CO₂ constitutes 71.6% of total emissions, followed by methane (CH₄) at 21%, nitrous oxide (N₂O) at 4.8%, and fluorinated gases (F-gases) at 2.6% [4,5].

Many jurisdictions, both national and subnational, have introduced carbon pricing measures to incentivize progress toward established decarbonization goals. The most widespread mechanisms are the Emission Trading System (ETS), adopted by 37 jurisdictions, and the carbon tax (CT), also implemented by 37 jurisdictions [3].

In both cases, the product’s cost increases as the emissions from its production rise. The ETS mechanism, known as “cap and trade”, involves setting a maximum limit, or “cap”, on the total amount of greenhouse (GHG) gases that covered installations and aircraft operators can emit. This cap is gradually reduced over time, and it is quantified in terms of emission allowances, with each allowance representing the right to emit one metric ton of carbon dioxide equivalent (CO₂eq). Companies within the system must surrender enough allowances annually to cover their emissions completely. Failure to do so results in significant fines. Additionally, within the system, it is also allowed to trade emissions allowances such that if a company reduces its emissions below its allocated allowances, it can either save the surplus for future use or sell them to other entities [6].

Alternatively, a CT directly taxes either the GHG emissions produced or the fuels responsible for emitting these gases when burned, correlating with the emissions generated. As a result, goods and services with higher GHG emissions during their production are subject to a higher carbon tax [7].

Presently, approximately 12 Gt of CO₂eq fall under a carbon pricing framework, constituting roughly 23% of total global emissions and yielding a collective revenue of USD 97 billion. Specifically, 18% of these emissions are governed by an ETS, generating USD 67 billion in revenue, while the remaining 5% are subject to a CT, resulting in USD 30 billion in revenue [7].

Therefore, it is imperative to implement measures facilitating a swift transition away from fossil fuels as the primary energy source and to effectively decarbonize various sectors of human activities from multiple perspectives. Since the inaugural World Climate Conference (WCC) in 1979, international efforts have been dedicated to addressing the environmental consequences of human activities and devising collaborative strategies to mitigate and halt these impacts. A significant milestone in this trajectory was the 1987 Montreal Protocol, ratified by 197 United Nations (UN) Member States. This landmark agreement aimed to regulate approximately 100 chemicals responsible for depleting the atmospheric ozone layer, facilitating its natural restoration. The successful outcomes of the measures enacted underscored the potential of concerted global political efforts in effecting substantial changes to address pressing environmental challenges [8].

Subsequently, in 1988, the establishment of the Intergovernmental Panel on Climate Change (IPCC) further advanced the scientific understanding of climate change. Building on this momentum, the UN Conference on Environment and Development, commonly known as the Earth Summit, convened in 1992, paving the way for the creation of the UN Framework Convention on Climate Change (UNFCCC) [8]. By the year’s end, 158 nations had pledged their commitment to the UNFCCC, which officially came into effect in March 1994. This landmark agreement laid the foundation for annual Conferences of the Parties (COPs), with the inaugural gathering held in 1995 in Berlin. During the third COP in 1997, the Kyoto Protocol was formulated, marking the world’s inaugural international treaty aimed at curbing global warming emissions. This legally binding accord obligated developed nations to set emission reduction targets. Specifically, industrialized countries were required to collectively reduce their GHG emissions to 5 percent below 1990 levels within a span of 10 to 15 years.

It is noteworthy that, at the time of the protocol’s inception, India and China were not classified as industrialized nations due to their pre-boom economic status, exempting them from its mandates [8].

The implementation of the Kyoto Protocol spanned nearly a decade, effectively coming into force in 2005. While some regions, like the EU, successfully met the protocol’s objectives, achieving desired reductions in carbon emissions, others fell short. Unfortunately, the progress made by numerous countries was counteracted by the escalating emissions from nations like the United States (US) and China, where regulatory frameworks regarding pollution were less stringent during that period. The deteriorating environmental conditions, coupled with economic and political shifts in countries such as India and China, underscored the need for a revised agreement. This new accord drew upon the principles of the Kyoto Protocol but also adapted to the evolving global landscape [8].

The UNFCCC Durban Platform for Enhanced Action of 2011 established the necessity to draft a new and updated agreement by 2015 to address climate change, including developing countries such as China and India.

In 2015, the Paris Agreement emerged as a pivotal milestone in global climate action. This legally binding international treaty, effective since November 2016 and ratified by 195 Parties, sets forth long-term objectives to steer nations toward substantial reductions in global GHG emissions. It aims to keep the increase in global temperature well below 2 °C above pre-industrial levels, with efforts to limit the increase to 1.5 °C. Central to the Paris Agreement are provisions for periodic assessments of collective progress and the provision of financial support to developing countries for climate mitigation, resilience building, and adaptation. This framework lays the groundwork for concerted efforts towards a net-zero emissions future, a cornerstone for achieving Sustainable Development Goals (SDGs). Operating on a five-year cycle, the agreement mandates countries to update their national climate action plans, known as Nationally Determined Contributions (NDCs), every five years. These NDCs outline specific emission reduction measures and resilience-building strategies tailored to each country’s circumstances [9,10].

Figure 2 offers a timeline showing international treaties based on the will of global political powers to address climate change.

The objectives and deadlines imposed differ from one state to another, mirroring the variations in international agreements. Generally, countries with developing economies are afforded a wider and less stringent timeframe.

Table 1. Decarbonization targets of some emitters over the world. Self-elaboration based on [11,12,13,14,15,16,17,18].

Country	Short-Term Decarbonization Goal	Long-Term Decarbonization Goal
Australia	- 43% from 2005 levels by 2030 [11]	Net-zero emissions by 2050 [11]
Canada	- 40% from 2005 levels by 2030 [13]	Net-zero emissions by 2050 [13]
China	- CO2 peak carbon emissions by 2030 [14]	Net-zero emissions by 2060 [14]
EU	- 40% from 1990 levels by 2030 [15,16]	Net-zero emissions by 2050 [15,16]
India	- 45% from 2005 levels by 2030 [17]	Net-zero emissions by 2070 [17]
Japan	- 46% from 2013 levels by 2030 [18]	Net-zero emissions by 2050 [18]
US	- 50–52% from 2005 levels by 2030 [12]	Net-zero emissions by 2050 [12]

illustrates the decarbonization objectives of some of the most emitting states.

A particular importance is given to the necessity of decarbonizing the world’s electricity system. This is critical for addressing climate change and ensuring access to clean and affordable electricity for everyone, in line with SDG 7. Achieving this goal requires a significant increase in the use of renewable energy sources (RESs) in electricity grids. Responding to the urgent need for rapid decarbonization across the global economy, a coalition of energy buyers, suppliers, governments, system operators, solution providers, investors, and other stakeholders has come together to promote 24/7 Carbon-free Energy (CFE). This approach ensures that every kilowatt-hour of electricity consumed is matched by carbon-free sources every hour of every day [19].

In this perspective, in the Climate Ambition Summit convened by the UN Secretary-General in 2023, a Climate Action Acceleration Agenda (CAAA) was presented which aimed to accelerate the set of actions requested by various leaders for a drastic reduction in GHG emissions, trying to bring forward the net-zero deadlines to 2040 for developed countries and 2050 for emerging countries, and to present energy transition plans with tangible actions by 2035 for developed countries and 2040 for developing countries. Also, the Organization for Economic Cooperation and Development (OECD) countries must accomplish the coal phase out by 2030, while the rest of the world should achieve it by 2040. The CAAA, above all, calls for accelerating the decarbonization of sectors such as shipping, aviation, and industry, in particular the steel, cement, and aluminum industries while pressing to reallocate fossil fuel subsidies toward renewable energy initiatives. This shift is vital for fostering the growth of sustainable energy sources, which can play a significant role in meeting net-zero targets [10,20].

In particular, electricity is projected to become the dominant energy carrier, potentially accounting for over 50% of TFEC by 2050, driven by the enhanced deployment of RESs, improved energy efficiency, and further electrification across various sectors. In the buildings sector, heating and cooling technologies, particularly HPs, are promising for further electrification based on carbon-free electricity. In 2022, global HP installations grew by 11%, with a notable 38% increase in Europe. In the U.S., annual sales of HPs surpassed those of fossil gas furnaces for the first time. In the industrial sector, electrification is primarily focused on lower-temperature heat applications, showing slower deployment [21,22]. Therefore, IHPs are key elements to meet decarbonization goals for the industry sector while helping to increase the share of RES electricity into the grid. Nevertheless, the integration of renewables and IHPs are still facing important challenges in some sectors.

Data pertaining to various sectors of pollutant emissions reveal that the power industry, transportation, and industrial combustion sectors are the primary contributors to emissions, accounting for 38.08%, 20.68%, and 16.97% of total emissions, respectively. Together, these sectors are responsible for over two-thirds of overall CO₂ emissions. Following these sectors are building (8.88%), processes (8.38%), fuel exploitation (6.57%), agriculture (0.39%), and waste (0.04%), as depicted in Figure 3.

1.2. State of Art

High-temperature heat pumps (HTHPs) and large-scale heat pumps (HPs) are gaining traction in industrial process heating and district heating applications, and as a critical component in incorporating RESs into the electricity supply system. As a consequence, many studies focus on the integration of these devices in industrial processes, as well as their effect on the electricity grid and the possibilities to upgrade waste heat. Fischer et al. highlighted that HPs are crucial for integrating RESs into the grid, significantly enhancing wind power adoption by reducing grid electricity needs by up to 95%, mitigating feed-in-peaks, and improving self-consumption of PV electricity by 30–65% through real-time adjustments and variable speed technology [23]. Similarly, the study carried out by Bloess et al. emphasizes that HPs improve wind power generation and introduction to the grid [24]. The advantages of integrating a DC HP in an AC-DC distribution network have been reported by Charalambous et al., highlighting that this approach, which connects PVs, batteries, and DC loads in a historical building in Cyprus, achieved over 85% RES usage and notably reduced imported energy [25]. On the other hand, Yilin Li et al. investigate the operational strategy of a DC inverter HP system in an office building equipped with a PV power system, analyzing PV power fluctuations and demand-side load characteristics [26]. The study carried out by Maruf et al. explores different HP configurations, covering aspects such as design, operation, recent advancements, and application potentials, to provide comprehensive insights into HP technology [27]. Similarly, Arpagaus et al. present a study on HTHPs, where they reviewed the market and application potentials in detail, providing a first classification of HTHPs [28], while Marina et al. focus on the analysis of the EU HTHPs’ potential market, with special attention given to the food and beverage, chemical, and refining sectors [29].

Hamid et al. consolidated the data about HTHPs available in the literature; providing a review on recent advances in the technology [30]. In the study conducted by Walden et al., a new methodology for designing and sizing industrial HPs (IHPs) using annual process data is introduced, considering the time average model, the pinch analysis, and thermo-economic optimization [31]. Sadjjadi et al. review the approaches of the IHP system in smart grids, highlighting their strengths and potential for energy flexibility [32].

Wu et al. address the inefficiencies of the current waste-heat recovery methods in industrial parks with multiple heat sources and loads by developing an HP-centric network system and a two-stage optimization model for waste-heat utilization. The approach combines waste heat with HP combinations and users, showing a significant decrease in the energy consumption [33].

Thiel et al. state that HTHPs are a key technology in the decarbonization of industry, thus not neglecting to discuss the barriers that hinder the deployment of IHPs in this sector [34]. Sorknæs et al. examine the role of industry electrification within various 100% RES system scenarios, concluding that direct electrification of industrial process heat is generally preferable [35]. Lechtenböhmer et al. dedicate their attention specifically to the importance of electrifying the energy-intensive basic materials industry [36].

As the main potential for IHPs is represented by their application in industrial sub-sectors where the majority of processes require low-to-medium temperature heat, many studies around the world focus on the analysis of the HP technologies in those sub-sectors, like the food and beverage, pulp and paper, and chemicals sub-sectors. For instance, Zuberi et al. focus on the United States of America (USA) food manufacturing industry, revealing that electrifying process heat through HTHPs could save 325 PJ of energy and 31 MtCO₂ by 2050, but at a very high cost [37], while, Flórez-Orrego et al. depict the eventual effects of the integration of HTHPs into industrial processes of ammonia plants and pump mills [38].

1.3. Contribution

This study aims to provide a comprehensive examination of the regulatory frameworks and policy initiatives driving the advancement of HPs globally, comparing decarbonization objectives and environmental policies across selected nations, with a specific emphasis on their utilization in the industrial sector. It underscores the significant heterogeneity in objectives, deadlines, and incentive policies for these technologies. Furthermore, it highlights the lack of dedicated regulatory structures for HTHPs in most examined states, along with the scarcity of publicly available data on the installed capacity of IHPs. Addressing persistent obstacles, this study suggests potential remedies.

This paper fills a notable gap in the scholarly literature by consolidating dispersed data from academic, sector-specific, and policy-oriented sources to offer a concise review of current policy initiatives promoting HPs at a global scale, particularly in the industrial sector. This essential update to the knowledge base aims to raise awareness of the critical need for developing policies and regulatory frameworks to facilitate the widespread adoption of this decarbonization technology.

The manuscript is organized as follows: Section 1 establishes the context by outlining the current environmental goals of major emitting countries and identifying gaps in the existing literature. Section 2 provides a comprehensive overview of the importance of decarbonizing the industrial sector, particularly focusing on how low-to-medium heat demand can be met using power-to-heat (P2H) technology such as HPs. Section 3 delves into HP technology, highlighting its main characteristics, advantages, and barriers. Section 4 reviews relevant policies in some of the world’s largest emitting countries. Section 5 offers a brief analysis on possible ways to tackle the barriers to the spread of IHPs. Finally, Section 6 offers concluding remarks, summarizing key findings and their implications for future policy and technological advancements.

2. The Decarbonization of the Industrial Sector

2.1. Electrification of Industrial Heat Demand

The industrial sector stands out as one of the most energy-intensive and polluting sectors in many economies worldwide. A significant portion of its final energy consumption is dedicated to process heating, typically heavily relying on fossil fuels. Consequently, this reliance significantly contributes to GHG emissions. According to the data, in 2022 alone, the industrial sector accounted for nearly a quarter of the total CO₂ emissions from the global energy system, and its main energy source is represented by fossil fuels [39,40].

This global trend is also evident at the national level. For instance, in the USA, industry represents over 32% of total energy consumption. A significant portion of on-site industrial energy use, accounting for 51%, is attributed to the generation and utilization of process heat. This sector thus becomes a key focus for energy and CO₂ emissions reduction efforts. Presently, less than 5% of the energy used for process heat generation comes from electricity, with the majority sourced from fossil fuels [41].

Similarly, in the EU, the industrial sector accounts for approximately 26% of the region’s total final energy consumption (TFC). Fossil fuels, particularly oil and petroleum products (approximately 35%), electricity (approximately 23%), and natural gas (NG) (approximately 23%), are the primary sources of energy for this sector [42,43]. In India, the industrial sector stands out as the largest consumer of energy, comprising 42% of the nation’s TFC [44]. This pattern persists across other countries as well. In China, for instance, the industry sector accounts for a substantial 49% of TFC, with heat being the primary end-use application, constituting approximately 60% of energy demand [45].

Therefore, decarbonizing the industrial sector worldwide is crucial to reach the desired reduction in overall emissions. Process heat, specifically, accounts for the majority of industrial energy consumption, representing up to 50–70% of the total [46]. Prioritizing the decarbonization of process heating and improving energy efficiency is essential for industries striving to meet their climate objectives by 2030 and beyond [47].

The development of new technologies enabling zero-carbon heat production through electrification offers a promising avenue for significantly reducing sectoral emissions. However, decarbonizing the industry sector poses unique challenges due to its diverse range of processes and substantial heat demand, which vary widely in terms of required temperatures and desired outcomes (e.g., simple heat exchange or specific chemical reactions) [48]. Consequently, no single technology can electrify heating applications across this spectrum. In this context, P2H technologies emerge as a crucial element for sectoral decarbonization through electrification. These technologies involve the conversion of electrical energy into heat, primarily for use in the built environment or industrial processes [27].

Generally speaking, industry electrification can be achieved through two methods: direct and indirect electrification. Direct electrification involves producing heat using electric boilers and HPs, while indirect electrification entails generating electricity-based fuels for burning in boilers or similar systems [35].

Electrification could also benefit power systems by reducing peak demand fluctuations. As renewables’ share in the power mix increases, surplus wind or solar power can be utilized with low-cost electric devices like resistors in boilers or tanks, enhancing grid flexibility and occasionally reducing CO₂ emissions. Additionally, short-duration heat storage can increase flexibility and facilitate greater renewable power uptake by industry, aiding in variability management. In the context of industry electrification, aligning with the transformation of the national electricity system is imperative, particularly in the transition to 100% renewable-based electrification. Such a shift entails a departure from the conventional system reliant on dispatchable thermal power plants and the concept of “base load” in favor of a system accommodating variable renewables [49].

Energy-intensive processing industries have the potential to become flexible “swing consumers”, using electricity to produce materials (power-to-products) rather than reducing excess solar and wind energy. For example, producing hydrogen for various industrial processes on demand could become a major flexible load in the future power system. This shift in economic thinking would also influence the geographic locations of these industries. Traditionally, they have been located near raw material sources or energy supplies. In a future dominated by RES, these industries might instead move closer to sources of renewable electricity [36].

Furthermore, the process of electrification and the broader transformation of the electricity system entail technological changes and cost considerations that must be carefully evaluated. To achieve viability, any zero-carbon heating technology must effectively meet the end user’s heat demand at a competitive cost. Heat demand is influenced by two primary factors: temperature and load. For instance, industrial processes like steelmaking and cement production require temperatures that can exceed 1400 °C. Industrial heat, typically fueled by cheap coal and NG in certain regions, often represents a relatively inexpensive energy source compared to residential retail electricity prices. Despite the decreasing costs of renewable electricity, many industrial electricity tariffs remain high, resulting in electrified heating—especially without the use of HPs—often costing two to three times more than fossil-based heat generation [36].

To bridge this cost gap, electrified heating technologies must significantly improve in efficiency, and HP technologies are precious allies for this purpose. These systems can achieve a thermal energy output per unit of electricity input (MWhth/MWhe) greater than 1, thereby offsetting the higher operating costs associated with electricity. However, achieving this efficiency gain at a low capital cost is essential for competitiveness. Moreover, traditional fuel sources possess the capability to generate flame temperatures well beyond what is required for industrial processes. The affordability and high performance of modern carbon-based heat generation, which stem from decades of scientific and engineering advancements, pose a substantial challenge for the development of economically competitive decarbonized alternatives [34].

2.2. Low-to-Medium-Temperature Heat Processes

Numerous industrial sub-sectors depend heavily on processes that require heat and direct combustion. The demand for heat within the industry is highly diverse, characterized by a wide range of temperature requirements and varied applications. This diversity stems from the different needs across sub-sectors, whether it is for simple heat exchange or for more intensive processes that require direct combustion. For instance, the temperature requirements can vary significantly—from lower temperatures needed for processes like food processing to extremely high temperatures exceeding 1400 °C necessary for steelmaking and cement production. That is, industrial operating temperatures are dictated by different industrial processes, and they can be generally classified as follows [50]:

-

Ultra-low (<100 °C);

-

Low (<200 °C);

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Medium (200–500 °C);

-

High (>500 °C).

This manuscript focuses on the demand for low-to-medium-temperature heat, a significant portion of the overall energy requirement in the industrial sector, where HTHPs can be suitable. On average, this category accounts for approximately 44% of the final energy consumption dedicated to industry [51]. Notably, about 80% of this low-to-medium-temperature heat demand is concentrated within G-20 countries [50].

For instance, in the EU, a study estimated the total heat demand for industrial processes and space heating in the EU28+3 to be 2315.6 TWh. Approximately 39% of this demand, or 759.3 TWh, is attributed to process heat requirements up to 200 °C [29].

In China, the use of low-to-medium-temperature heat is widespread in light industries. These sectors represent over a third of China’s industrial heat consumption but account for more than three-quarters of heat consumption below 200 °C. The potential for HPs to meet this demand is significant, with estimates suggesting a capacity of 175–280 GW, sufficient to cover about 15% of the current heat demand in these industries [45]. In Australia, around 48% of process heat is utilized at temperatures below 250 °C. This indicates a substantial opportunity for low-temperature heat to play a crucial role in reducing industrial energy consumption and emissions [52]. In the USA, almost 45% of the total industrial heat demand required by processes is under 200 °C [41].

However, assessing the potential use of HTHPs in some regions is challenging due to a lack of detailed data on the thermal ranges of industrial processes. For instance, comprehensive global data on low-to-medium-temperature heat demand for the Indian industry are not readily available in the literature. While specific data for certain sub-sectors, such as paper mills, do exist, there is a general gap in information for broader industrial applications [53,54]. A similar lack of data was also identified for Canada, Russia, Brazil, and Japan, which are among the largest global emitters. This data gap poses a significant barrier to the adoption of HTHPs, as their implementation requires a thorough understanding of an industry’s thermal demand, both in terms of the power and temperature range. To address this issue, this paper provides an estimated range of heat demand for low-to-medium-temperature industrial processes in countries where such data are not readily available in the literature. We base these estimates on the premise that approximately 50–70% of a country’s total industrial energy consumption is dedicated to process heat [46].

Figure 4 illustrates the demand for low-temperature industrial heat in some of the world’s major emitters. In cases where direct data were not available in the literature, an estimated value was determined based on the available information, to offer insight into the potential significance of this thermal range within industrial energy consumption. It stands out that, at least from a theoretical point of view, HTHPs have a huge potential all over the world.

In particular, low-to-medium-temperature processes dominate the heat demand in sectors such as mining, food and beverage, tobacco, pulp and paper, machinery, and transport equipment manufacturing. On the other hand, high-temperature processes account for a significant portion of the heat demand in sectors including chemical, non-metallic minerals, and basic metals production [46].

The meat processing industry, for instance, involves processes such as blood drying, dehairing, and edible and inedible rendering that need steam at around 120 °C. In the dairy industry, processes like pasteurization and evaporation could benefit from the implementation of IHPs. Similarly, in the textile industry, various operations including washing, bleaching, steaming, and printing could potentially utilize HTHPs [60].

The food, pulp and paper, and chemical industries collectively show significant potential for utilizing HTHPs. Currently, commercially available HTHPs are effective for processes such as drying, pre-heating, boiling, and pasteurization, handling temperatures up to 100 °C. Furthermore, ongoing advancements indicate that HTHPs capable of achieving even higher temperatures are expected to become technologically feasible in the near future [27].

Figure 5 illustrates several processes within these sub-sectors that necessitate heat at low-to-medium temperatures.

Within this temperature range, the potential adoption of HTHPs offers a pathway for industries to achieve net-zero emissions and transition to 100% renewable energy sources (RESs). This potential stems from the ability to power heat pumps with RESs such as geothermal heat or electricity generated from renewables. The utilization of RES-driven IHPs in this thermal range holds promise for reducing pollutants and advancing sustainability efforts within the industry [61].

Already established for supplying heat at temperatures below 100°C, IHPs are actively being integrated into industrial operations. As fuel costs and carbon taxes evolve, HTHPs are increasingly viable even for applications requiring temperatures exceeding 100 °C [47].

The maturity of HP technology for ultra-low-heat applications (up to 100 °C) presents a credible opportunity for near-term action, potentially electrifying up to 11% of global heat demand [50].

This factor could play a pivotal role in advancing the adoption of this technology within the industrial sector. Particularly noteworthy is the commitment of over 400 RE100 companies to transition to ‘100% renewable’ energy sources. Among these companies are prominent international giants primarily originating from the USA and EU, such as Ikea, BMW Group, Coca-Cola, General Motors, H&M, Heathrow, Hewlett Packard, Lego, Microsoft, Nestlé, Nike, Philips, Telefonica, Tetra Pak, and Unilever. Additionally, there is representation from companies in China (e.g., Broad Group), India (e.g., Tata Motors), and Japan (e.g., Ricoh), albeit in smaller numbers. However, it is worth noting that in 2015, 60% of the renewable power procured by RE100 companies was through the purchase of renewable certificates, with another 35% secured via green contracts or tariffs with utilities [49].

3. Heat Pumps: Technological Principles, Challenges, and Potential

3.1. Physical Principle

An HP is a P2H technology that transfers heat from one or more low-temperature sources (T_source) to one or more high-temperature sinks (T_sink) with the aid of an external energy source [27]. The working principle of an HP is schematically illustrated in Figure 6.

Essentially, they are designed to move thermal energy against the natural heat gradient, absorbing heat from a cold reservoir and discharging it to a hot one [37].

HPs are generally characterized by high performance because they operate based on energy transfer rather than energy generation or conversion. Unlike boilers, which convert the chemical energy of fuel through combustion to produce thermal energy, they move existing heat from one place to another, making them more efficient than conventional boilers. Different types of HPs are categorized based on their energy input. In this context, we primarily focus on electrically driven vapor compression HPs, which are the most common type and use electrical energy to transfer a lower-temperature thermal source heat to a higher-temperature environment. An electrically driven HP uses a compressor to move a refrigerant through a refrigeration cycle and heat exchangers, one to extract heat from the source and the other to deliver heat to the sink. In buildings, the heat is distributed using forced air or hydronic systems, such as radiators or under-floor heating. Additionally, many HPs can provide space cooling in the summer, in addition to heating in the winter. In industrial applications, these devices are used to supply hot air, water, or steam, or to directly heat materials. Large-scale HPs used in commercial or industrial settings, or in district heating networks, require higher input temperatures than residential units. These higher temperatures can be sourced from waste heat generated by industrial processes, data centers, or wastewater, representing a further advantage of the use of these devices [37,62,63].

An energy and exergetic analysis is available in the Appendix A at the end of the manuscript for readers who wish to deepen their understanding of this aspect related to HPs.

HPs provide more energy in the form of heat than the amount of energy input they consume [49]. For instance, a typical household HP has a COP of around four, meaning the energy output Q_H is four times the electrical energy input W. This makes modern HPs up to five times more energy efficient than gas boilers [63].

The external energy required to operate an HP depends on the temperature increase (T_lift) needed for the low-quality heat. The higher the value of T_lift, the greater the amount of energy input W needed to achieve it, resulting in a lower COP [62].

The efficiency of an HP largely depends on its heat source. In winter, the ground and external water sources are usually warmer than the ambient air, so ground-source and water-source HPs use less electricity and achieve a higher COP compared to air-source HPs. This is especially true in cold climates, where defrosting the outdoor components of air-source HPs can consume additional energy, therefore lowering the COP. However, ground-source HPs are more expensive to install due to the need for an underground heat exchanger, such as a deep vertical borehole or a large network of pipes buried at least one meter underground. Connecting a water-source HP to a nearby river, groundwater, or wastewater source can also be costly. As a result, ground-source and water-source HPs are generally less common than air-source pumps. Globally, almost 85% of all HPs sold for buildings are air-source, as they are easier to install. Many of these are air-to-air units, although air-to-water (or hydronic) units are becoming more common in regions where heating is a priority [63].

Regarding its use in the industrial field, it must be considered that the optimal placement and integration of an IHP in an industrial plant can be determined through pinch analysis. This technique minimizes the energy demand of industrial processes by identifying potential heat recovery between hot and cold streams and optimizing unit operations. Pinch analysis involves developing composite curves that combine the profiles of available heat sources (hot composite curve) and heat sinks (cold composite curve). The extent of overlap between these curves indicates the potential for heat integration. The point where the hot and cold composite curves come closest to each other is known as the “pinch point”. Above the pinch point, there is a heat deficit, and below it, there is a heat surplus. Optimally, an HTHP should be placed where it can transfer heat from below the pinch point to above it, achieving a higher T_lift. However, it is important to note that the greater the T_lift, the lower the COP, and the higher the capital and operational costs of the IHP [37].

3.2. Strengths and Barriers

IHPs offer several advantages to the industrial sector, such as a long annual operating time, maximizing their utility and return on investment. Additionally, they are designed as large units with a small distance between the heat source and the heat sink, which reduces thermal losses. IHPs are also highly efficient because the production of waste heat and the demand for heat often occur simultaneously, ensuring that the heat generated is immediately utilized, further enhancing their operational efficiency [62].

Due to their efficiency, IHPs can help in reducing the energy CP demand associated with many industrial processes. For example, in the USA food industry, studies estimate potential energy savings of 280 PJ per year in 2021 and around 325 PJ per year by 2050 from electrifying processes like meat processing, beer production, vegetable and fruit canning, and cane sugar refining. The heat demand for vegetable and fruit canning can be entirely met by IHPs. Moreover, HPs are an excellent technology for providing flexibility to the power system while delivering efficient heating and cooling solutions. The installation is generally easy, and they require minimal maintenance while guaranteeing high safety standards [27].

However, transitioning to HP technologies is not straightforward. Several factors can discourage or complicate the adoption of this technology. High upfront capital costs and long payback periods—typically four to five years or more—pose significant barriers to the adoption of HTHPs [34,64].

For example, replacing a 2 MW steam boiler with a 2 MW HP could cost five to eight times more than installing a new boiler, with a payback period likely exceeding five years. However, it is also important to note that an HP of 500 kW or smaller may be sufficient when replacing a steam system, potentially lowering both the initial investment and payback time [65].

Furthermore, the viability of an electric solution hinges on the relative prices of electricity versus the fuel it would replace, along with any necessary changes to the electricity infrastructure to increase supply. Currently, the electricity-to-fuel cost ratio remains too high, necessitating efforts to enhance the competitiveness of HP technologies [62].

A crucial element to take into account is the need to redesign the industrial processes in order to adapt the heat generation and its distribution to the processes in a new way that enables the integration of P2H technologies as well as the enhancement of the recuperation of industrial waste heat. Therefore, assessing the available excess heat resources is essential for effectively integrating IHPs into a process. However, the quantity and quality of excess heat in an industrial plant are highly dependent on the specific site. The degree of process heat integration is influenced by a variety of techno-economic factors unique to each plant, such as the volume and temperature of excess heat and its alternative uses, plant complexity, space limitations, energy costs, and external agreements. Due to these unique site-specific factors, creating generalized composite curves for an industrial process and estimating pinch temperatures from these curves involve a high degree of uncertainty. Consequently, the IHP integration design based on generalized data may not be optimal for every individual plant, creating challenges because the commonly available data are typically generalized [37,66,67].

In addition to the importance of integrating sensors and systems to collect as much data as possible at a local level, it is important to generate knowledge about the industrial processes and IHP technology integration. To effectively raise awareness of the available options and to make informed selections among them, a high level of expertise in system design, process integration, and planning is essential. Design software for process integration and system design is crucial at this stage [62].

Also, the limitations of the power network are a significant, often overlooked barrier to the broader application of HTHPs that should not be underestimated. Intensive electrification of the heating industry will significantly impact electrical distribution systems, historically designed for lower demands. For instance, in the UK, HPs’ adoption could increase peak power consumption by up to 14%, potentially requiring network strengthening and impacting the economic sustainability of HP integration. Overloading and voltage stability issues could arise with higher HP penetration, highlighting the need for further research into the relationship between RES and peak electricity demand and new strategies to manage peak-to-average demand ratios [30].

Furthermore, the technology readiness level (TRL) of some HTHPs is relatively low compared to more mature fossil-based technologies like boilers. Low-temperature electric HPs (<90 °C), electric boilers (both resistance and electrode types), and electric resistance heaters are well-established technologies and are fully ready for deployment (TRL 9). However, for HPs with output temperatures over 90 °C, the TRL decreases as the temperature increases, ranging from 9 at <90 °C to as low as 3 at <160 °C [27].

The adoption of HTHPs is also significantly hampered by public acceptance and understanding issues. These issues often stem from unfounded concerns, misconceptions, factual inaccuracies, and negative experiences with HTHP reliability. Even in highly developed societies, there is sometimes a lack of public awareness regarding the financial and environmental benefits of integrating HTHPs. For instance, noise pollution from HTHPs can raise public concerns and hinder adoption. To address this, noise levels are often managed using noise barriers. Despite their net positive environmental impact, HTHPs face environmental challenges such as land subsidence and water pollution, which affect their integration into industrial processes [30].

A major barrier to consider is also the policy uncertainty to clear heat decarbonization pathways and the adoption of new technologies, including HTHPs. Many countries lack specific policies tailored to HTHPs, opting instead for broad, one-size-fits-all heating policies. This generalized approach is often ineffective in reducing carbon emissions. A cross-country analysis within the EU demonstrates that the absence of clear legal and regulatory frameworks impedes technological progress. The economic and fiscal design for low-carbon heating systems significantly varies depending on the end-use and heating technology employed. Furthermore, inadequate financing for HP research and development (R&D) negatively impacts the economic viability and acceptance of these technologies [30].

This aspect gains even more importance considering that energy-intensive industries face international competition, making it challenging to impose regulations without risking job losses and industry relocation [68].

Eventually, due to the higher sink temperature and the bigger T_lift between the cold reservoir and the hot reservoir, IHPs present technical barriers that do not exist for household HPs. In fact, HPs operating between 150 °C and 200 °C need special refrigerants and compressors, technologies that are still in the early prototype stages [63].

In fact, the lack of suitable refrigerants that can effectively operate within the desired temperature range is a major challenge, and, additionally, there is a shortage of experimental and demonstration plants, limiting opportunities for testing and refining HTHP technology. Managing compressor discharge temperatures presents a formidable challenge. Achieving higher sink temperatures without compromising lubrication oil integrity or encountering material issues is a complex task. Incorporating additional components to manage oil in the compressor adds to system complexity and costs. The development of oil-free compressors or self-lubricating solutions is essential. However, such advancements often come with higher equipment costs or may not be suitable for commercial use [30].

All the strong points as well as the barriers associated to the HTHPs are schematically reported in Figure 7.

4. The Promotion of IHPs over the World

Despite all the challenges, the adoption of HPs is experiencing an upsurge in certain markets. For instance, in Europe, IHP sales are witnessing rapid growth, surpassing 2500 units in 2022 from a mere 600 units in 2016. Similarly, in Japan, the number of installed IHP systems exceeded 6000 by 2020. In China, although the IHP sector is still emerging, there are notable early examples. These include the Hongjitang brewery, which utilizes a 216 kW HP to produce steam at 120 °C and a grain dryer developed by the Chinese Academy of Science, employing a 650 kW HP to supply hot air at 70 °C [45].

Here follow the measures implemented by various countries to promote the adoption of HTHPs, which include the enactment of specialized regulations and the funding of research initiatives.

4.1. Australia

In Australia, efforts to promote the adoption of HTHPs in industrial settings are gaining traction as part of the broader push towards decarbonization and energy efficiency. The Climate Change Authority has identified HP importation as a key indicator of decarbonization progress in the built environment [69].

Given that Australian industry accounts for a significant portion of the nation’s energy consumption, with 52% of it attributed to process heat, valued at approximately AUD 8 billion annually, there is a pressing need to transition towards more efficient technologies for industrial heat production. Currently, the predominant sources of heat in Australia are gas combustion followed by coal. To meet decarbonization targets and increase energy productivity cost-effectively, Australian businesses are encouraged to adopt technologies that can efficiently provide industrial heat while integrating renewable energy generation. Notably, there are already available, proven IHPs and thermal battery technologies that offer reliable energy supply and flexibility to maximize the benefits of renewable energy and demand response strategies. Australia has taken concrete steps to facilitate the adoption of HP technology. For instance, the launch of the Heat Pump Estimator, an online estimation tool, assists businesses in appropriately sizing HPs to replace gas boilers, thus reducing energy costs and advancing decarbonization efforts to achieve net-zero targets [65,70].

In New South Wales (NSW), the Net Zero Manufacturing Initiative is a significant effort aimed at providing up to AUD 275 million in funding across three programs: the Clean Technology Innovation, the Low Carbon Product Manufacturing, and the Renewable Manufacturing programs. These initiatives aim to accelerate R&D and commercialization of emerging clean technologies and expand local manufacturing capacity for low-carbon products and materials. By supporting the development of innovative technologies such as HTHPs to a market-ready level, this initiative contributes to increasing industrial efficiency, decarbonization, and the adoption of renewable energy in the industrial sector [71].

The government is actively investing in initiatives to reduce emissions and enhance the resilience of high-emitting industries, allocating AUD 305 million in grant funding for this purpose. This funding supports key objectives outlined in the High Emitting Industries (HEI) initiative, which aims to decarbonize high-emission facilities, accelerate transformation projects, and foster prosperity in a zero-emissions economy [72].

HEI is a focal point of the Net Zero Industry and Innovation Program (NZIIP), a flagship program designed to help NSW achieve a 50% reduction in emissions (compared to 2005 levels) by 2030 and reach net zero emissions by 2050. This program is a cornerstone of the Net Zero Plan Stage 1: 2020–2030, aiming to provide over AUD 1 billion to support and collaborate with industries in reducing emissions and thriving in a low-carbon environment [73].

Under the Net Zero Industry and Innovation Investment Plan 2022–2024, various funding opportunities are available for industry. These include the following:

• AUD 305 million allocated for abatement projects at high-emitting manufacturing and mining facilities;
• AUD 55 million earmarked for the establishment of clean manufacturing precincts in the Hunter and Illawarra regions, along with support for their infrastructure and supply chains;
• An additional AUD 300 million dedicated to new low-carbon industry foundations.

Australia has implemented a comprehensive suite of programs and initiatives to reduce emissions across businesses, industries, and among consumers. A key component of this strategy is the Emissions Reduction Fund (ERF), which provides financial incentives for organizations and individuals to adopt new practices and technologies aimed at reducing emissions and storing carbon. By promoting innovative approaches to emission reduction and carbon storage, the ERF encourages stakeholders to actively engage in sustainable practices in Australia’s climate change strategies [69].

Another significant initiative is Climate Active, a program that incentivizes Australian businesses to achieve carbon neutrality. By offering the Climate Active Carbon Neutral Standard certification, the program recognizes and rewards businesses that implement sustainability practices and work diligently to reduce their carbon footprint. This not only promotes environmental responsibility but also enhances the marketability of participating businesses as eco-friendly.

The Renewable Energy Target (RET) scheme is another crucial element of Australia’s climate change strategy. It aims to reduce emissions by increasing electricity generation from RESs. By incentivizing the shift towards cleaner energy, the RET scheme contributes significantly to the overall efforts to lower GHG emissions, supporting the transition to a more sustainable energy sector [69].

Additionally, the Australian Carbon Credit Unit (ACCU) Scheme supports projects that prevent the release of GHG emissions or remove and sequester carbon from the atmosphere. This scheme encompasses a wide range of activities, including the adoption of new technologies, equipment upgrades, changes in land or business practices, and vegetation management strategies focused on carbon storage. By facilitating these projects, the ACCU Scheme plays a vital role in enhancing Australia’s carbon sequestration capabilities and reducing its overall carbon footprint [69].

Eligible projects span various sectors, including vegetation management, agriculture, forestry, energy consumption, waste management, transport, and industrial processes. Participants in these projects earn ACCUs for every ton of carbon dioxide equivalent (tCO₂-e) emissions stored or avoided. These ACCUs can be sold to private sector buyers and governments, generating income for project participants and furthering emission reduction efforts. The Australian Government also purchases ACCUs through carbon abatement contracts, supporting emission reduction initiatives through programs like the Powering the Regions Fund. Despite the effort, there is an absence of a comprehensive framework for decarbonizing manufacturing and industrial sectors in Australia that contrasts with existing initiatives for low-energy buildings. However, there is potential to accelerate the adoption of HPs in industry as part of a broader decarbonization strategy. Looking to examples from overseas, particularly New Zealand’s strategy for reducing emissions from process heat, could inform the development of such a framework [67].

Table 2. Australian regulations and initiatives to boost the development of decarbonizing technologies such as HTHPs. Self-elaboration based on [65,67,68,69,70,71,72,73].

Promotion Programs	Characteristics	Investment	Reference
Heat Pump Estimator	Online estimation tool to assist businesses in correctly sizing HPs	-	[65,70]
Net-Zero Manufacturing Initiative	It consists of the Clean Technology Innovation, the Low Carbon Product Manufacturing, and the Renewable Manufacturing programs. It aims to accelerate and develop innovative technologies	AUD 275 million	[71]
High Emitting Industries	It aims to decarbonize facilities and promote a zero-emissions economy	AUD 305 million	[72]
Net-Zero Plan Stage 1, 2020–2030	It collaborates with industries toward the path of decarbonization	AUD 1 billion	[73]
Emission Reduction Fund	It gives financial incentives to adopt measures to reduce emissions and storage carbon	Depending on each case.	[69]
Climate Active, with the Climate Active Carbon Neutral Certification	The program rewards businesses that integrate sustainability practices and reduce their carbon footprint	-	[69]
Renewable Energy Target	It promotes electricity production from RESs	-	[69]
Australian Carbon Credit Unit Scheme	It offers support to projects that prevent GHG emissions or remove and store carbon from the atmosphere	-	[69]
Power the Regions Fund	It supports the Australian Carbon Credit Unit Scheme	-	[67]

schematically reports all the Australian initiatives directly and indirectly useful for the promotion of HTHPs.

4.2. Canada

The Government of Canada has committed to ambitious climate action goals, targeting a near-term reduction in emissions of 40–45% by 2030 and achieving a net-zero economy by 2050. To support these objectives, the CAD 8 billion Net Zero Accelerator (NZA) initiative was established, administered through the Strategic Innovation Fund (SIF). The NZA aims to accelerate GHG emission reduction efforts, attract investments, and promote sustainable economic growth by focusing on decarbonizing high-emitting sectors and facilitating the transition of established industries to a net-zero economy, and it is structured around three main pillars [74].

The first pillar, the Decarbonization of Large Emitters, supports major industrial sectors in reducing their GHG footprint. The second pillar, Industrial Transformation, invests in ensuring that existing industrial sectors remain competitive in a net-zero global economy. The third pillar, Clean Technology and Battery Ecosystem Development, aims to capitalize on emerging clean economy opportunities by establishing Canada as a global leader in clean technology and promoting the development of a domestic battery ecosystem [74].

Projects funded by the NZA initiative are aligned with Canada’s broader climate strategy, including the 2030 Emissions Reduction Plan and the Canadian Net-Zero Emissions Accountability Act. These initiatives aim to reduce GHG emissions across various sectors, including heavy industry and manufacturing, which significantly contribute to Canada’s emissions profile. A particular focus is on reducing direct emissions from residential, commercial, and institutional buildings. The 2030 Emissions Reduction Plan specifically aims to lower CO₂ emissions from these buildings to 53 Mt by 2030, representing a 37% reduction compared to 2005 levels [74].

By providing funding and support for transformative projects, the NZA initiative seeks to drive innovation, economic growth, and job creation while advancing Canada’s climate goals [75].

Existing policies, such as carbon pricing and consumer rebates, play a crucial role in making HPs the most cost-effective option for heating. It is imperative for governments to continue to enhance these policies to encourage the widespread adoption of HPs. In British Columbia, programs like the Oil to Heat Pump Affordability (OHPA) initiative provide substantial rebates of up to CAD 16,000 for low- and middle-income households looking to transition from oil heating to high-efficiency HPs. This transition aligns with the region’s goal of promoting electrification for a more sustainable and resilient future. Additionally, the expanded HP program in British Columbia offers significant savings on home energy costs [76].

For homeowners currently relying on oil heating, the OHPA program offers an upfront payment of up to CAD 16,000 to support the switch to energy-efficient HPs. This not only leads to substantial savings on heating bills but also contributes to reducing GHG emissions. The Canadian government has also developed a Heat Pump Calculator to help individuals estimate costs and climate pollution based on their specific circumstances. In the industrial sector, the Canadian government has implemented measures to support industries in adopting clean technology as part of their journey towards achieving net-zero emissions, such as HTHPs. Initiatives include developing a carbon capture, utilization, and storage (CCUS) strategy, introducing investment tax credits to incentivize technology development and adoption, and investing in expanding the Industrial Energy Management System. These efforts aim to facilitate ISO 50001 [77] certification, provide support for energy managers, offer cohort-based training, conduct audits, and promote energy efficiency-focused retrofits for key projects. Despite those initiatives, there is an imbalance between the measures used to promote HP adoption in the residential sector and those adopted to boost HTHPs in industry [13,76,78].

All the initiatives mentioned above are reported in

Table 3. Canadian regulation and initiatives to boost the development of decarbonizing technologies such as HTHPs. Self-elaboration based on [74,75,76,78].

Promotion Programs	Characteristics	Investment	Reference
Net-Zero Accelerator, administered through the Strategic Innovation Fund	It aims to accelerate GHG emissions efforts. It is based on three pillars: the Decarbonization of Large Emitters, Industrial Transformation, and Clean Technology and Battery Ecosystem Development	CAD 8 billion	[74]
2030 Emissions Reduction Plan	It promotes GHG reduction across various sectors. It aims to lower CO2 from building to 53 Mt by 2030	-	[75]
Canadian Net-Zero Emissions Accountability Act	It shares the same goals as the 2030 Emissions Reduction Plan, providing funds to reach decarbonization across different sectors	-	[74]
Oil to Heat Pump Affordability	It provides subsides to low-and-middle income households to switch from oil heating to HPs	Up to CAD 16,000	[76]
Heat Pump Calculator	It is a tool provided by the Canadian Government to help individuals to evaluate the effect of the adoption of an HP in their specific circumstances	- -	[13,76,78]

.

4.3. China

China’s National Energy Conservation Law was originally enacted in 1997 and first amended in 2007. The primary objective of this law is to reduce energy consumption across all sectors by promoting energy efficiency. It emphasizes both economic and social development while highlighting the economic benefits of improved energy efficiency. Additionally, the law incorporates a strategy to integrate energy conservation and efficiency into broader national economic and social planning efforts. Further amendments made in 2016 were designed to enhance these provisions and strengthen the overall framework for energy conservation [79].

Regarding the industrial sector, the law outlines a series of measures aimed at optimizing energy use and focusing on the efficient exploitation and use of energy resources. To achieve this, the State Council, along with provincial, autonomous regional, and municipal governments, is committed to promoting adjustments in the industrial structure. This includes encouraging energy-saving practices and enhancing overall energy consumption patterns [80].

In particular, policy specifically targeting energy-intensive industries such as electric power, iron and steel, nonferrous metals, building materials, petroleum processing, chemical, and coal industries are implemented to drive technical innovations that enhance energy conservation and encourage industrial enterprises to adopt highly efficient and energy-saving equipment. It also promotes the use of CHP generation, the utilization of residual heat and pressure, the adoption of clean coal technologies, and the implementation of advanced energy monitoring and control systems. Finally, the law prohibits the construction of new coal-fired or gasoline-fired generating units and new coal-fired thermal power generating units. This prohibition underscores a strong commitment to reducing reliance on fossil fuels and promoting cleaner energy sources [80].

Later, the 2013 the Renewable Energy Law, enacted in 2005 and amended in 2009, underwent further implementation improvements. The Renewable Energy Law establishes a solid framework for promoting renewable energy in China, covering wind, solar, water, biomass, geothermal, and ocean energy, but excluding the low-efficiency combustion of straw, firewood, and dejects. It designates renewable energy as a priority for energy development and includes it in the national high-tech industrial development program. The State Council oversees the implementation and management of renewable energy, setting medium- and long-term targets and national plans in coordination with regional and local governments. This law mandates that renewable power generation projects obtain administrative permits, with open tendering for multiple applications [81].

Approved projects are guaranteed grid connections, and their output can be sold to grid companies at prices set by the State Council’s price authorities. Grid operators can recover associated costs through their selling prices. Additionally, producers of gas and heat from RESs that meet urban pipeline standards are assured access to these pipelines. By providing a comprehensive regulatory environment, this law creates a robust foundation for deploying HPs and other renewable energy technologies [81].

Since 2011, China’s Five-Year Plans have started to prioritize the transformation of the heating sector, initially focusing on reforming the metering system in northern urban areas. The focus then expanded to include energy-saving measures, emissions reductions, and the utilization of clean energy [82].

China’s heating policies, introduced in 2013, initially aimed to improve air quality, especially in the north. By 2017, the focus expanded to clean and low-carbon heating, promoting a fuel shift from coal to gas and electricity. Policies included clean winter heating strategies and the replacement of coal in households in specific regions by 2020. Since 2020, policies have encouraged the use of waste heat, HPs, clean biomass, RESs, and CHP generation [45].

The 14th Five-Year Plan (2021–2025) set targets for improving energy and carbon intensity per unit GDP by 13.5% and 18%, respectively. In 2020, China announced goals to peak carbon emissions by 2030 and achieve carbon neutrality by 2060, followed by sectoral blueprints, including a plan for the buildings sector aiming for an electrification rate of 55% by 2025 and 65% by 2030. Action plans for industry promote energy savings and decarbonization [14].

The “Plan for Carbon Peak Action by 2030” includes heating considerations for the Hot Summer Cold Winter (HSCW) zone, promoting the integration of industrial waste heat and renewable energy into urban heating systems, and phasing out coal-fired boilers. HPs in Chinese buildings have a combined capacity of over 250 GW, expected to grow to 1400 GW by 2050 in the Announced Pledges Scenario (APS). China is projected to remain a top HP market, accounting for more than 25% of global sales and capacity by 2050, and, in particular in the HSCW area, air-to-air HPs are expected to dominate the market by 2050 [83].

In Beijing, gas boilers for space heating are banned in new public buildings, and the installation of HPs or hybrid systems is required [45].

Table 4. Regulations and initiatives to boost the development of decarbonizing technologies such as HPs in China. Self-elaboration based on [45,79,80,81,82,83].

Promotion Programs	Characteristics	Investment	Reference
National Energy Conversation Law	The primary goal is to reduce energy consumption across all sectors. It also incorporates a strategy to integrate energy conservation and efficiency in all sectors of the economy. The Law implemented specific policies to target energy-intensive industries. It also forbids the construction of new coal-fired thermal generation units	-	[79]
Renewable Energy Law	It establishes a regulatory framework to promote RESs in China. It guarantees support to projects that implement RESs	-	[81]
China’s Five Years Plan 2011–2015	It specifically prioritizes the transformation of the heating sector	-	[82]
The 14th China’s Five Years Plan 2021–2025	It sets targets to improve energy intensity by 13.5% per unit GDP and the carbon intensity per unit GDP by 18%	-	[84]
The Plan for Carbon Peak Action	It promotes the integration of industrial waste heat and RESs in the urban heating systems. It contains heating recommendations for the HSCW zone	-	[83]

recaps the main measures adopted in China to boost decarbonization and innovative technology.

4.4. Japan

In Japan, the Ministry of Economy, Trade, and Industry, in collaboration with various ministries and agencies, has outlined Japan’s ambitious yet realistic “Green Growth Strategy through Achieving Carbon Neutrality in 2050”. This comprehensive strategy identifies 14 promising fields and provides action plans focusing on both industrial and energy policies to foster growth within these sectors. Japan’s commitment to achieving carbon neutrality by 2050 is underscored by this strategy, which aligns all policies to support companies’ efforts toward this goal [84].

Specifically, the Green Growth Strategy comprises a series of industrial policies designed to drive significant transformation across various sectors. Many companies will need to fundamentally change their business models and strategies, presenting an opportunity to lead in a new era of sustainable development. The government’s role is to fully support private enterprises in their forward-looking initiatives, including bold investments in innovation. For sectors beyond electricity—such as industrial, transport, commercial, and residential—the primary strategy will be electrification. In horticultural facilities, the goal is to completely eliminate fossil fuel use by 2050. This will be achieved through the development of ultra-efficient technologies for heat storage, transfer, and dissipation, high-speed heating-type HPs, and the utilization of industrial waste heat. Additionally, on-site demonstrations will help reduce the cost of new technologies, while ultra-precise environmental control facilities will be developed to achieve RE100 [84].

Japan’s Long-term Strategy under the Paris Agreement for the industry plans to use electrification technologies such as HPs and electric heating to decarbonize low-temperature heat demand and improve energy efficiency [85].

In order to further improve energy efficiency in the industrial sector, Japan will review the index and the target values of the Benchmark Program. Furthermore, the Energy Efficiency Technological Strategies promote both the development and the introduction of technologies with high energy efficiency such as IHPs. The Green Innovation Fund is one of the financial means through which the country is financing and promoting the decarbonization of the industry while safeguarding its competitiveness. In parallel, Japan is also boosting the reinforcement of the electricity grid and the consequent development of the market with the Electricity Business Act [86]. It also aims to vastly use HPs in the building sector to improve the energy efficiency of the heat supply [87].

Furthermore, the country estimates to save about 251 Mt CO₂ emissions using HP technologies by 2050. In particular, it foresees a CO₂ emissions reduction for the industrial sector by means of IHPs of 48% by 2050 [85].

The HTHP industry in Japan is robust, with 24 manufacturers specializing in IHPs. Notably, four companies focus specifically on HTHPs capable of supplying temperatures of 100 °C or higher. These HTHPs find diverse applications across industries such as cleaning, drying, distillation, and concentration [88].

Japan’s commitment to HTHP technology extends to R&D initiatives spearheaded by the Ministry of Economy, Trade, and Industry. Additionally, Japan’s Central Research Institute of Electric Power Industry is actively engaged in advancing research on steam and HTHPs. Their establishment of an environmental test facility underscores Japan’s dedication to enhancing HP performance, with the ultimate goal of expanding their widespread adoption [67].

The New Energy and Industrial Technology Development Organization (NEDO), the national R&D agency that creates innovation by promoting technological development necessary for the realization of a sustainable society, is promoting many R&D Projects on HTHPs. The NEDO has been instrumental in advancing the development of HTHP technologies through a series of national R&D projects. These initiatives have involved several key players in the industry, including Fuji Electric, Mayekawa, and MHI Thermal Systems. Each company has contributed to the progress in HP technology, addressing various temperature ranges and applications. Fuji Electric participated in NEDO’s national R&D projects with a focus on developing a 150 °C steam supply HP. This project spanned from the Japanese fiscal year 2016 to fiscal year 2018. During this period, Fuji Electric aimed to enhance the efficiency and reliability of HPs capable of supplying steam at high temperatures, which are crucial for industrial processes that require significant thermal energy [89,90].

Mayekawa has been involved in multiple phases of NEDO’s HP projects. Initially, from fiscal year 2009 to fiscal year 2012, Mayekawa worked on a project to develop a 150 °C steam supply HP. This early endeavor laid the groundwork for subsequent advancements in HP technology [86,90].

Following this, Mayekawa engaged in another project from fiscal year 2013 to fiscal year 2022, which focused on the development of an HP capable of supplying steam at 180 °C. This later project aimed to address the challenges associated with higher temperature requirements and larger temperature differentials, thus broadening the scope and application of HP technology in industrial settings [47,90].

Eventually, MHI Thermal Systems also made significant contributions to the development of HTHPs under NEDO’s projects. From 2013 to 2022, MHI Thermal Systems worked on two key projects. The first involved the development of an HP capable of supplying steam at 160 °C, and the second focused on a more advanced system capable of delivering steam at 200 °C. Both projects targeted a large T_lift and sought to enhance the performance and application range of HPs in industrial processes requiring high thermal energy output [47,90].

Japan’s energy efficiency policy plays a crucial role in promoting the adoption of HTHPs in the industrial sector. A significant aspect of this policy is the Energy Conservation Grand Prize Award, established in 1990. This award recognizes outstanding energy conservation products and activities resulting from technological advancements made by private companies. Additionally, the Minister of the Environment’s Award for Climate Action honors individuals or groups that have made substantial contributions to combating global warming. These initiatives collectively encourage innovation and the implementation of energy-efficient technologies in industry.

Japan is also involved in the USA–Japan Climate Partnership, which focuses on three pillars:

• Implementing the Paris Agreement and achieving 2030 targets NDCs;
• Developing, deploying, and innovating clean energy technologies;
• Supporting decarbonization efforts in other countries, especially in the Indo-Pacific.

This partnership emphasizes enhancing cooperation on renewable energy, energy storage, smart grids, energy efficiency, hydrogen, carbon capture and storage, industrial decarbonization, and advanced nuclear power, as well as promoting climate-friendly infrastructure [91,92].

The most relevant initiatives and regulations present in Japan are reported in

Table 5. Regulations and initiatives to boost the development of decarbonizing technologies such as HPs in Japan. Self-elaboration based on [47,67,84,85,86,87,88,89,90,91,92].

Promotion Programs	Characteristics	Investment	Reference
Green Growth Strategy	It provides action plans and energy policy for the sustainable evolution of 14 promising fields, including the industrial sector	-	[85]
Japan’s Long-Term Strategy under the Paris Agreement	It oversees the use of electrification technologies such as HPs and electric heating to decarbonize low-temperature heat demand, while improving the overall efficiency	-	[86]
Energy Efficiency Technological Strategies	It promotes both the development and the implementation of highly efficient technologies like HTHPs	-	[87]
Green Innovation Fund	A financial instrument to promote industry decarbonization without harming competitiveness	-	[87]
Electricity Business Act	A tool to reinforce the national electricity grid aiming to support the use of HPs in the building sector	-	[87]
The New Energy and Industrial Technology Development Organization (NEDO)	National R&D agency promoting many research projects on HTHPs. It involves many key industrial partners	-	[90]
Energy Conservation Grand Prize Award	It recognizes outstanding energy conservation products ad activities across all the sectors	-	[93]
Award for Climate Action	It rewards individuals or groups that have significantly contributed to coping with climate change	-	[93]
USA–Japan Climate Partnership	It consists of three pillars: the implementation of the Paris Agreement; development, deployment, and innovation in clean energy technologies; supporting decarbonization actions in other countries, especially in the Indo-Pacific area	-	[92]

.

4.5. EU

A variety of directives such as the Energy Performance of Buildings Directive (EPBD), the revised Renewable Energy Directive (RED), and the Energy Efficiency Directive (EED) aim to promote HPs in the EU, particularly for domestic use [93,94].

In particular, the EPBD requires Member States to develop long-term energy renovation strategies for buildings, aiming for an 80% to 95% reduction in CO₂ emissions by 2050, with HPs identified as a high-efficiency alternative to fossil fuel-based heating systems. It is supported in its purpose by the revised RED that highlights HPs as crucial for renewable heating and cooling, utilizing sources like ambient and geothermal energy and facilitating waste heat use from sectors including data centers [93,94].

The EED states that when calculating the share of renewable energy within a district heating system, all heat provided to the network by HPs qualifies as renewable energy, and it also establishes that the evaluation of waste heat utilization must consider HPs together with other heat-to-power technologies [95].

The revision of the Energy Taxation Directive, on the other hand, aims to make HPs more attractive from a taxation perspective by reducing the difference between electricity and gas, reducing the VAT for energy-efficient technology, and taxing fossil fuels [96].

Other tools, like the Next Generation EU and REPowerEU, collectively support HP implementation in households, by providing funds to support a greener economy after the COVID19 pandemic and by boosting the annual sales of HPs, respectively [97,98].

The European Commission has scheduled its Heat Pump Action Plan (HPAP) to release after the EU elections in June 2024. The HPAP aims to accelerate HP market adoption, outlining actions such as partnerships, communication, skills development, legislation, and financing. The Heat Pump Accelerator, involving industry, governments, and non-governmental organizations (NGOs), proposes solutions to HP sector challenges, including regulations to mandate HP use in industrial processes and prohibit fossil fuel-based solutions for industrial heat up to 200 °C [59,99].

For the industrial sector, the Net-Zero Industry Act wants to amplify clean technologies’ production in the EU by attracting investments and simplifying the regulatory framework, and, together with the Green Deal Industrial Plan that aims to accelerate the deployment of innovative and sustainable technologies, it represents a pillar for decarbonizing EU industry and encouraging the transition to HPs [100,101].

Apart from the regulative initiatives, EU funding instruments play a crucial role in supporting HP technology development and deployment across various stages, from low-TRL breakthroughs to large-scale implementation and skills development. These projects often view HPs as integral to larger systems, including industrial applications. The European Investment Bank (EIB) is a significant global financier for climate action, supporting small- and medium-sized enterprises through the European Investment Fund (EIF), which commits EUR 250 million to mobilize EUR 2.5 billion for climate action investments [102].

Additionally, the EIB supports the REPowerEU plan with up to EUR 30 billion over five years for renewables, energy efficiency, grids, storage, and breakthrough technologies.

EU support for Research, Development, and Innovation (RD&I) in HPs is facilitated by the European Research Council (ERC), Horizon Europe Programme (HEP), and Marie Skłodowska-Curie Actions (MSCA) [102].

These funding instruments collectively enhance the performance and cost-effectiveness of HPs, particularly in the industrial sector, by demonstrating technical feasibility and supporting large-scale deployment through specific R&D projects.

Several EU countries are carrying out a variety of projects to phase out fossil boilers and promote the use of HPs across various sectors. For instance, in Austria, the DryFiciency Project aims to enhance energy efficiency in European industries by recovering waste heat for process heat streams up to 160 °C. It involves three vapor compression HTHPs demonstrated in industrial settings [103].

France is developing a full-scale transcritical IHP demonstrator for a paper facility within the TRANSPAC Project [104].

Norway is also very active in the HP R&D field, especially with its HighEFF Research Center that collaborates on advancing HTHPs across sectors like metal production and food processing and is leading many innovative projects to demonstrate the reliability and viability of the use of HTHPs in industrial applications [105].

These initiatives highlight the diverse and collaborative efforts across Europe to enhance the deployment of HTHPs, aiming to reduce energy consumption, improve efficiency, and transition to more sustainable energy systems.

Table 6. Regulations and initiatives to boost the development of decarbonizing technologies both in the residential and in the industrial sector in the EU. Self-elaboration based on [59,93,94,95,96,97,98,99,100,101,102,103,104,105].

Promotion Programs	Characteristics	Investment	Reference
Energy Performance of Building Directive (EPBD)	It offers a long-term energy renovation strategy for buildings, targeting a 80% to 95% reduction in CO2 emissions by 2050, with HPs identified as a high-efficiency alternative to fossil fuel-based heating systems. It also supports initiatives to increase awareness and knowledge about HPs among consumers, professionals, and policymakers.	-	[94]
Revised Renewable Energy Directive (RED)	It indicates HPs as a pivotal technology for renewable heating and cooling.	-	[95]
Energy Efficiency Directive (EED)	It states that when calculating the share of renewable energy within a district heating system, all heat provided to the network by HPs qualifies as renewable energy, and it establishes that the evaluation of waste heat utilization must consider HPs together with other heat-to-power technologies.	-	[96]
Revised Energy Taxation Directive	It offers guidelines to align between gas and electricity prices, by reducing the VAT for energy-efficient technology while taxing fossil fuels.	-	[97]
Next Generation EU	It provides funds for the EU’s recovery post-COVID-19 pandemic, supporting a greener economy based on efficient technologies, such as HPs.	-	[98]
REPowerEU	The main goal is boosting the annual sales of HPs.	It will receive up to EUR 30 billion over five years from the EIB + EUR 20 million from the Recovery and Resilience Facility Plan (RRF)	[99]
Heat Pump Action Plan (HPAP)	To be released after the EU elections in June 2024, it aims to accelerate HP market adoption, outlining actions such as partnerships, communication, skills development, legislation, and financing.	-	[100]
Heat Pump Accelerator	A cross-sectoral initiative that proposes solutions to HP sector challenges, including regulations to mandate HP use in industrial processes and to prohibit fossil fuel-based solutions for industrial heat up to 200 °C.	-	[100]
Net-Zero Industry Act	It aims to amplify clean technologies’ production in the EU by attracting investments and simplifying the regulatory framework.	-	[101]
Green Deal Industrial Plan	Its main goal is to accelerate the deployment of innovative and sustainable technologies, encouraging the transition to HPs.	-	[102]
The European Investment Fund (EIF) within the European Investment Bank (EIB)	The EIF is the main tool used by the EIB to finance EU actions and initiatives to tackle climate change.	EUR 250 million + funds to REPowerEU	[103]
The Recovery and Resilience Facility Plan (RRF)	The RRF is a tool designed to support the green transition in the industrial sector, giving funding to programs aiming to overcome the barriers hindering HP diffusion in the EU industry. It also gives support to the REPowerEU.	EUR 225 billion	[103]
Just Transition Mechanism (JTM) with the Just Transition Fund (JTF)	Its main goal is to face the lack of expertise on innovative technologies by financing training courses to generate the knowledge needed in a green, sustainable industry.	EUR 3 billion	[103]
The Innovation Fund, the InvestEU Fund, and the Strategic Technologies for Europe Platform (STEP)	All of them are designed to incentivize the transition to a clean-energy-based industry by promoting R&D and pilot projects.	Total of EUR 222.2 billion (Innovation Fund: EUR 40 billion + InvestEU: EUR 26.2 billion + STEP: EUR 160 billion)	[103]
LIFE Programme Clean Energy Transition (CET), within the LIFE Programme	The LIFE Programme CET includes funding to roll-out HPs in the building sector with the LIFE 2023 CET HEATPUMPS segment.	EUR 1 billion	[103]
European Research Council (ERC), Horizon Europe Programme (HEP), and Marie-Sklodowska-Curie Actions (MSCA)	These programs’ goal is to finance R&D projects in many fields, comprising innovative alternative like HTHPs.	Total of EUR 118.1 billion (ERC: EUR 16 billion + HEP: EUR 95.5 billion + MSCA: EUR 6.6 billion)	[103]

offers a summary of the EU initiatives enhancing the development and the deployment of HPs both in the building and in the industry sector.

4.6. USA

There have been various USA-based policies to encourage the spread of HPs. While initially this mainly affected domestic HPs, recently, numerous initiatives have been undertaken to encourage IHPs. In the context of building regulations and initiatives, several important documents and regulations have been issued to promote the use of HPs and to improve energy efficiency. These include the following:

• Initiative for Better Energy, Emissions, and Equity (E3 Initiative): this initiative encourages the use of HPs in cold climates. It was further strengthened by the Residential Cold Climate Heat Pumps Technology Challenge introduced in December 2021 [106];
• Japan–USA Clean Energy Partnership: this partnership aims to accelerate the adoption of HPs in domestic and local markets, fostering a collaborative approach between Japan and the USA to promote clean energy technologies [91];
• ICEE HOT (Installing Clean Efficiency Energy Hastens Our Transition) Act: enacted in May 2022, this act provides discounts for distributors and manufacturers of heat pumps, HP water heaters, and HP clothes dryers made in the USA, incentivizing the production of these energy-efficient appliances [107];
• HEATR (Heating Efficiency and Affordability through Tax Relief): this legislation offers tax incentives to manufacturers to increase the production of HPs and phase out inefficient air conditioners (ACs), promoting more efficient heating solutions [108];
• Defense Production Act Invocation: in June 2022, the Defense Production Act was invoked to boost the manufacturing of key energy technologies, including HPs, ensuring a stronger focus on energy independence and technological advancement [109];
• Inflation Reduction Act: this act includes provisions to support energy efficiency and the adoption of renewable energy technologies, contributing to a broader strategy to reduce inflation through sustainable practices [110];
• New Efficiency Ratings for AC and Heat Pumps: effective January 2023, new efficiency ratings for ACs and HPs were introduced, setting higher standards for energy performance and encouraging the use of more efficient cooling and heating systems [111].

These initiatives and regulations collectively aim to enhance energy efficiency, reduce emissions, and support the transition to cleaner energy technologies in the building sector.

Numerous recent initiatives have aimed to bolster the development and utilization of HP technology, specifically in the industrial sector. This focus is particularly significant in light of the imperative to decarbonize industries, aligning with the USA environmental goals.

The Biden Administration has set ambitious targets, including achieving 100% carbon pollution-free electricity by 2035 and net-zero GHG emissions by 2050. These objectives are outlined in Executive Order 14008 [112], which presents pathways toward a net-zero economy by 2050. The industrial decarbonization strategy in the USA aligns with the Justice40 Initiative, which ensures that at least 40% of the benefits from federal climate and clean energy investments reach disadvantaged communities [113]. The Industrial Decarbonization Roadmap provides a cohesive technical approach, focusing on four key pillars: energy efficiency; industrial electrification; low-carbon fuels, feedstocks, and energy sources; and CCUS [114].

One crucial aspect of industrial electrification involves the adoption of HTHPs. The USA’s Department of Energy (DOE) has allocated significant funding to accelerate domestic manufacturing of HPs, leveraging President Biden’s Inflation Reduction Act and the Defense Production Act (DPA) [115,116]. These investments not only promote energy efficiency but also support the Justice40 Initiative’s goals.

Moreover, research initiatives led by institutions like Purdue University aim to develop HTHP technology capable of significantly reducing energy use and GHG emissions in various industrial applications [117].

The DOE’s Industrial Efficiency and Decarbonization Office, through its roadmap, funds projects to reduce the industrial carbon footprint, facilitating the transition to a net-zero emissions economy. Its decarbonization efforts span across multiple sectors, including chemicals, iron and steel, food and beverage, cement and concrete, and paper and forest products. These projects focus on enhancing energy efficiency, developing clean technologies, and reducing emissions. Through collaborations between universities, national laboratories, and companies, the USA is advancing toward a cleaner, more sustainable industrial sector. The DOE’s commitment to industrial decarbonization is further evident in programs like the Technologies for Industrial Emissions Reduction Development (TIEReD) program and the Industrial Demonstrations Program. These initiatives aim to invest in transformative technologies and support their demonstration and deployment, driving progress toward a decarbonized industrial sector [118].

The USA is also financing several R&D projects to demonstrate the economic and technical feasibility of HTHPs, as well as to overcome relevant barriers related to technical aspects. Some of the most interesting ones aim to boost cross-sector decarbonization technologies [118].

For instance, Siemens Energy, Inc. will collaborate with Dow Chemical to advance the design of modular HP systems featuring a two-stage hermetic solution for centrifugal compressors. These modular compressors are designed to prevent refrigerant leakage and offer a smaller footprint compared to conventional compressors. By replacing fossil fuel combustion, these HPs can help decarbonize process steam. The final assembly aims for a COP of 2.56 and a design life of 20 years [118,119].

Thar Energy LLC and its partners aim to replace gas-fired industrial boilers with a supercritical CO₂-based HTHP system that integrates into existing manufacturing infrastructure. The project will develop key components, including a high-temperature ionic liquid piston compressor, two energy recovery devices, and a compact heat exchanger for superior performance. This approach overcomes critical technological barriers to high efficiency using supercritical CO₂. The goal is to achieve a 40% reduction in energy intensity using low global warming potential refrigerants [118,119].

Oak Ridge National Laboratory (ORNL) will lead a team to develop an IHP system capable of achieving 200n °C sink temperatures. The project addresses system-level design considerations to maintain efficiency while raising sink temperatures, including waste-heat recovery technology. The goal is to enable the electrification of high-heat industrial processes. The team will demonstrate a cascading HP system using low global warming potential (GWP) refrigerants in transcritical cycles, enhanced efficiency via expansion work recovery devices, and advanced artificial intelligence (AI) process control. By the project’s end, they will test a 20 kW prototype [118,119].

Also, many universities are involved in HTHP-related R&D projects. Purdue University will lead a team to enhance IHPs by developing an internally cooled screw compressor capable of providing higher temperature heat. These HPs offer a highly energy-efficient alternative to fossil fuel combustion, delivering zero-carbon heat when powered by clean energy sources. The project involves additive manufacturing of a screw compressor, researching stable refrigerants and lubricants with low GWP, and optimizing the integration of heat exchangers, thermal storage, and HP systems into industrial processes. An interdisciplinary team will address the lubricant, energy storage, and heat exchanger design for the compressor technology [118,119].

The University of Maryland and its partners will enhance HTHPs to provide continuous, zero-carbon heat for processes exceeding 200 °C. To improve existing HP technology, the team will implement a novel injection system using isopropanol refrigerant combined with an efficient heat exchanger system. This approach, utilizing a near-saturation cycle process with multi-stage compression, aims to achieve high efficiency at 200 °C with a T_lift of 100 °C [118,119].

Some projects specifically target decarbonization in USA sub-sectors, such as the pulp and paper industry and the food and beverage industry. For instance, the Texas A&M Engineering Experiment Station, in collaboration with the University of Pennsylvania, University of Virginia, and other partners, is leading a project to reduce energy use and carbon emissions in the food and beverage industry’s drying processes. The team is researching, developing, and demonstrating a high-performance hybrid desiccant-wheel HP system. This system will integrate dehumidification, low-cost sensors, data assimilation, and model-free predictive controls to optimize the food drying process. The goal is to lower energy costs and carbon emissions while ensuring food quality [118,119].

For the decarbonization of the pulp and paper industry, the University of Maryland is developing a multi-effect drying system that reuses energy multiple times to heat air for the drying process. This technology could enable waste to be repurposed as feedstock for chemical production or as a fuel source for other facilities, significantly reducing primary energy needs and increasing energy efficiency. Powered by an electric HP using a low-GWP refrigerant, this system is expected to cut energy consumption and CO₂ emissions by over 70% compared to traditional fuel-burning kilns. When powered by zero-carbon electricity, these HPs can eliminate fossil fuel combustion for heat in many industrial applications [118,119].

Micro Nano Technologies, in collaboration with the University of Florida, the Gas Technology Institute, and other partners, is developing and field-testing a potentially zero-carbon, energy-efficient drying technique for lumber production. They aim to design and manufacture a full-scale absorption HP that addresses the cost, size, efficiency, and operational limitations of current technology. This HP could reduce energy consumption and carbon intensity by over 60% compared to conventional dryers and by 20% relative to state-of-the-art electric HPs. When combined with zero-carbon heat sources like geothermal or concentrated solar power, absorption HPs could eliminate GHG emissions in industrial drying processes [118,119].

Table 7. Regulations and initiatives to boost the development of decarbonizing technologies both in the residential and in the industrial sector in the USA. Self-elaboration based on [91,106,107,108,109,110,111,112,113,114,115,116,117,118,119].

Promotion Programs	Characteristics	Investment	Reference
Initiative for Better Energy, Emissions, and Equity (E3 Initiative), strengthened by the Residential Cold Climate Heat Pumps Technology Challenge	It encourages the use of HPs in cold climates	-	[107]
USA–Japan Climate Partnership	It consists of three pillars: implementation of the Paris Agreement; development of, deployment of, and innovation in clean energy technologies; support decarbonization actions in other countries, especially in the Indo-Pacific area	-	[92]
Installing Clean Efficiency Energy Hastens Our Transition (ICEE) Act	It provides discounts for distributors and manufacturers of HPs, HP water heaters, and HP clothes dryers made in the USA, incentivizing the production of these energy-efficient appliances	-	[108]
Heating Efficiency and Affordability through Tax Relief (HEATR)	It provides tax incentives to manufacturers to increase HP production	-	[109]
Defense Production Act Invocation	The main target is to enhance key technology manufacturing, including HPs	-	[110]
Inflation Reduction Act	It supports energy efficiency and RES technology adoption	-	[111]
New Efficiency Rating for AC and HPs	It defines a new efficiency rating for AC and HP systems	-	[112]
The Industrial Decarbonization Roadmap	It offers guidelines to follow to decarbonize industry, based on four pillars: energy efficiency; industrial electrification; low-carbon fuels, feedstocks, and energy systems; CCUS	-	[115]
The DOE’s Industrial Efficiency and Decarbonization Office	It gives funds to projects that aim to reduce the industrial carbon footprint	-	[116]
The Technologies for Industrial Emission Reduction Development (TIEReD) and the Industrial Demonstration Program	They are tools to invest in transformative technologies, boosting their development and deployment in the industrial sector	USD 135 million	[119]

offers a summary of the regulations and initiatives for the promotion of HPs in the USA.

The global promotion of HTHPs showcases both shared objectives and diverse strategies, shaped by regional priorities, energy landscapes, and industrial demands. Generally, most countries recognize the crucial role of HTHPs in decarbonizing industry and lowering energy costs. However, the intensity of support, focus on specific sectors, and mechanisms for promoting these technologies vary significantly. A notable commonality among many countries, including Australia, Japan, and the EU, is the acknowledgment of the necessity for industrial decarbonization. All these regions understand the importance of transitioning high-emission industries, such as steel manufacturing, chemicals, and cement production, to cleaner alternatives like HTHPs. This need is particularly urgent in energy-intensive sectors that require substantial high-temperature heat. As a result, these regions are aligning their energy policies to facilitate this transition by supporting R&D, funding innovative projects, and promoting energy-efficient technologies through specific incentives. While the overarching goals are similar, the support mechanisms differ. Australia, for instance, has adopted a targeted, programmatic approach by funding industry-specific innovations and providing tools such as the Heat Pump Estimator, which helps businesses replace conventional gas boilers with heat pumps. In contrast, Japan has developed a robust ecosystem for HTHPs, characterized by substantial government support for R&D and the promotion of private industry innovation. The presence of specialized manufacturers and a clear focus on industrial applications in Japan indicate a more advanced market for HTHPs compared to other countries. This distinction is evident in the establishment of dedicated national R&D programs, partnerships among industry leaders, and the promotion of specific high-temperature heat pumps for industrial processes. On the other hand, the EU’s approach encompasses multi-faceted initiatives that address both residential and industrial applications. The EU’s Heat Pump Action Plan and forthcoming legislation aim to create a supportive environment for large-scale adoption, targeting both the domestic sector and industrial applications. These policies are expected to encourage both supply-side innovations and demand-side incentives, facilitating a more efficient transition to HTHPs for both industry and households. Notably, the EU’s regulatory efforts are complemented by funding mechanisms that support pilot projects and promote collaboration between industry players and research institutions. In contrast, regions such as Canada and the U.S. have concentrated more on residential heat pumps, particularly in areas where space heating and cooling are significant energy demands. These countries have been successful in promoting low- to medium-temperature heat pumps; however, HTHPs for industrial use are less emphasized in their policy frameworks. For example, Canada has made progress with residential rebates and incentives aimed at transitioning from oil-based heating systems to heat pumps, but it lacks robust support for the adoption of IHPs. This approach stands in contrast to the more industrial-focused strategies seen in Japan and Australia. Similarly, while the U.S. has several initiatives that support residential HP adoption, it has only recently begun to increase its focus on promoting IHPs, indicating an evolving policy direction towards higher-temperature applications. China’s strategy for energy efficiency, although strong, differs notably from that of the other regions, as it currently lacks a dedicated policy promoting HTHPs. Instead, Chinese policies target broader industrial decarbonization through the implementation of energy-saving technologies, without specifically prioritizing HTHPs. This approach reflects the country’s more generalized strategy for industrial energy reform, which includes the promotion of clean coal technologies and CHP systems, rather than direct support for HP technology. However, given China’s drive towards cleaner energy and industrial modernization, the indirect support for energy-efficient technologies could eventually create an environment conducive to the adoption of HTHPs in the future. In summary, while there is a global effort to promote high-temperature HPs aimed at decarbonizing industry and reducing energy consumption, the strategies employed vary significantly in focus and implementation. Countries like Japan and Australia lead with highly targeted industrial policies that drive research and development (R&D) as well as the commercialization of HTHPs. The EU supports both the residential and industrial sectors through a broad framework of regulations and funding. In contrast, Canada and the U.S. have strong residential HP adoption but are still developing strategies for industrial-scale applications. Lastly, China’s more generalized energy efficiency policies, while beneficial, do not yet prioritize HTHPs, reflecting a different approach to industrial decarbonization. These differences illustrate the varying economic structures, energy challenges, and technological capabilities of each region, highlighting the complexity of global efforts to promote energy-efficient HP technologies.

5. Brief Analysis

The potential of HPs to drive decarbonization and meet the goals of the Paris Agreement is widely recognized. A critical factor in the race to decarbonize is undoubtedly time. The global targets are highly ambitious, with a pressing need to achieve them swiftly. For centuries, humanity has depended on fossil fuels to meet heating needs, both domestically and industrially. This reliance has not only shaped a global economy predominantly based on fossil energy but has also fostered extensive technical expertise in exploiting these resources over more environmentally friendly alternatives.

Decarbonizing through electrification, therefore, requires a profound transformation—not only in how we generate and supply heat but also in our social and economic structures. This shift must be accompanied by a significant change in mindset to achieve the desired outcomes, presenting numerous challenges along the way.

Beyond the described barriers, a significant challenge lies in the heterogeneity of political, economic, and industrial contexts worldwide. Implementing HTHPs cannot rely on a single solution that fits all industries or meets the diverse demand for low-to-medium-temperature heat. The required heat and methods of delivery vary significantly depending on the industrial sector, specific processes, and the availability of in situ resources. Thus, HTHP applications require customized configurations on a case-by-case basis.

Furthermore, the need for tailored solutions extends beyond technical considerations to encompass measures promoting this technology. Creating a regulatory framework that establishes IHPs as a key technology for global industrial decarbonization must consider the economic and social characteristics of each country. Promotional measures suitable for highly developed countries may be entirely unsuitable for developing nations. In developed countries with established industrial infrastructures, strategies should focus on converting existing industries into decarbonized ones through robust incentives.

Examples include recognizing heat generated by HPs as “sustainable heat” with reward systems similar to Japan’s Award for Climate Action and the Energy Conservation Grand Prize Award. Economic incentives could also reward fuel savings achieved through IHP adoption, such as through financial remuneration or cost reductions under current carbon pricing systems. Additionally, tax breaks can encourage companies to switch from fossil fuel-based technologies to HTHPs. However, stricter penalties for non-compliance with decarbonization goals should be approached with caution. Such measures could undermine industrial competitiveness in certain regions and potentially drive industries to relocate to countries with more lenient tax regimes, leading to significant social and economic repercussions. For countries with developing industries, the focus should be on establishing decarbonized sectors from the outset, incorporating high-efficiency technologies and primarily utilizing RESs. This approach can lead to a highly digitalized industry with efficient data collection systems, both general and local. Achieving this from the beginning can be easier than retrofitting existing industries, which involves substantial modifications to industrial processes, heat supply methods, and machinery, resulting in high investment costs.

While theoretically straightforward, creating an “a priori” decarbonized industrial sector presents practical challenges due to the higher initial investment costs compared to traditional fossil-based industries. This requires advanced technologies, highly skilled personnel, and the capacity to manage longer payback periods. Therefore, substantial and well-defined political and legislative support is crucial from the start. However, these aspects often pose significant barriers to the adoption of HTHPs and other highly energy-efficient technologies.

The concept of energy efficiency must also be contextualized to local characteristics. For instance, in a country where thermal demand is typically met with coal-fired boilers, switching to NG boilers would be a significant efficiency improvement, even though it is not a fully decarbonized option. Standardizing certain concepts and enhancing international collaborations would help create standard “decarbonization processes” for specific industrial activities, such as pasteurization in the food industry, without compromising the final product quality. Standardization and collaboration are more feasible in nascent industries than in established ones.

6. Conclusions

HTHPs offer a significant opportunity for reducing emissions and enhancing energy efficiency in industrial processes worldwide. However, their deployment faces substantial techno-economic barriers. To overcome these challenges, a coordinated and multifaceted approach involving all stakeholders—governments, utilities, manufacturers, and industry professionals—is essential.

Governments play a pivotal role in accelerating the adoption of HTHPs by providing financial incentives such as subsidies, grants, and tax credits. These measures can lower the initial investment barriers and make the transition to HTHPs financially attractive for industrial plants. Additionally, government policies should mandate the integration of HTHPs in industrial energy plans, creating a regulatory environment that favors clean energy technologies.

Utilities must ensure that the electricity grid infrastructure is capable of reliably supporting the increased demand from electrified industrial systems. This includes investing in grid upgrades and implementing smart grid technologies to manage the load efficiently. Reliable electricity supply is crucial for the consistent operation of HTHPs, which are central to decarbonizing industrial heat demand.

Manufacturers of HTHPs need to collaborate closely with industrial plants to identify specific heat requirements that can be met by their technology. Customizing solutions to fit the unique needs of different industries will be key to demonstrating the practical benefits of HTHPs. Manufacturers should also engage in continuous R&D to enhance the efficiency and applicability of HTHPs across various industrial processes.

A comprehensive strategy for deploying HTHPs should include planning, piloting, and demonstrating these systems in existing industrial sites. Pilot projects can showcase the technical feasibility and economic benefits of HTHPs, providing valuable data and building confidence among potential adopters. Ongoing R&D should be supported to explore new applications and improve the performance of HTHPs, ensuring they can meet the diverse needs of the industrial sector.

Upskilling the workforce is another critical component of this transition. Engineers, construction professionals, and energy service providers need specialized training to effectively integrate HTHP technology into manufacturing processes. Government-supported training programs and certifications can help build a pool of skilled professionals ready to implement and maintain HTHP systems. This will address the ‘chicken and egg’ paradox where demand for HTHPs is low due to a lack of trained professionals and vice versa.

Regulatory frameworks must also evolve to support the adoption of HTHPs. Establishing minimum standards for performance, safety, and quality will build trust in the technology. Additionally, regulations should encourage the phase-out of the most carbon-intensive technologies and promote the use of HTHPs as a cleaner alternative. These standards should be dynamic, keeping pace with technological advancements and cost reductions.

Integrating HTHPs with RESs can further amplify their environmental benefits. By combining HTHPs with renewable electricity, industries can achieve near-zero emissions from their heating processes. Smart energy management systems, thermal storage solutions, and load flexibility measures can optimize the operation of HTHPs, reducing operating costs and enhancing grid stability.

Legislators are encouraged to develop industry-specific electrification roadmaps that outline clear pathways for transitioning to HTHPs. These roadmaps should consider the unique heat demands and constraints of different sectors, providing tailored solutions and policy support. Establishing robust standards and regulations will ensure the safe and efficient deployment of HTHPs, while ongoing R&D will drive innovation and expand their applicability.

Financial incentives should not only cover the initial investment but also address the increased operating costs associated with electrification. Grants, co-investment schemes, and mechanisms for demonstrating emissions reductions can encourage early adoption and scaling up. Public–private partnerships (PPPs) can facilitate the collaboration needed to advance HTHP technology, sharing risks and accelerating commercialization.

Workforce development initiatives should focus on training existing and future professionals in the installation, operation, and maintenance of HTHP systems. Educational programs must align with industry needs, ensuring that the workforce is equipped to handle the challenges and opportunities presented by industrial electrification.

By fostering cross-sectoral collaboration, governments can create platforms for knowledge sharing and partnership among industry players, power companies, technology providers, researchers, and policymakers. These platforms will facilitate the exchange of best practices, promote the co-development of technologies, and help align stakeholder interests.

In conclusion, deploying HTHPs in industrial settings requires a coordinated effort from all stakeholders. By implementing comprehensive policies, supporting R&D, upskilling the workforce, and fostering collaboration, legislators can create a robust foundation for the widespread adoption of HTHPs. This will not only reduce emissions and enhance energy efficiency but also drive innovation and economic growth in the clean energy sector.