Thermoelectric Generator Applications in Buildings: A Review

Abstract

With growing concerns about building energy consumption, thermoelectric generators (TEGs) have attracted significant attention for their potential to generate clean, green, and sustainable power. This comprehensive review explores the applications of thermoelectric generators (TEGs) in building systems, focusing on recent advancements from 2013 to 2024. The study examines TEG integration in building envelopes, including façades, walls, windows, and roofs, as well as non-integrated applications for waste heat recovery and HVAC systems. Key findings highlight the potential of TEGs in energy harvesting and thermal management, with façade-integrated systems generating up to 100.0 mW/m² and hybrid LCPV/T-TEG systems achieving overall efficiencies of 57.03%. The review also identifies critical parameters affecting TEG performance, such as solar intensity, thermoelectric arm length, and PCM melting temperature. Despite promising results, challenges remain in improving overall system efficiency, cost-effectiveness, and scalability. Future research directions include developing more efficient thermoelectric materials, optimizing system designs for various climatic conditions, and exploring integration with smart building management systems. This review provides valuable insights for researchers and practitioners working towards more energy-efficient and sustainable building designs using TEG technology.

1. Introduction

The building industry plays an important role in economic advancement and the worldwide emission of greenhouse gases. With an increasing population comes an increased adoption and use of energy-consuming gadgets as well as improved living standards in developing countries, which contribute to rising energy consumption in buildings. According to the International Energy Agency (IEA)’s Tracking Clean Energy Progress 2023 report, the building industry accounted for 34% of global energy consumption and 37% of energy sector emissions in 2022. Of these emissions, 9% were direct emissions from buildings, 18% were primarily due to electricity use in buildings, and the remaining 10% were from the production of building materials and the construction industry [1].

It is projected that the energy consumption in buildings will experience a significant increase of 46–73% by 2050 compared to the level of 128 EJ recorded in 2019 if there is no implementation of additional climate policies [2]. Along with the upward trend in building energy consumption, there is an unavoidable downward trend in the supply of fossil fuels needed to run society [3]. To address the shortage of traditional energy sources, several studies, supported by organizations such as the Intergovernmental Panel on Climate Change (IPCC) [4], the International Energy Agency (IEA) [1], and the United Nations Environment Programme (UNEP) [5], have been conducted to find more sustainable solutions, concepts, and new passive–active technologies for buildings.

Recently, thermoelectric devices (TEDs) have emerged as effective alternatives for waste energy recovery, heat pumping, and cooling applications, and the concept of employing thermoelectric devices to generate green, clean power in the building industry has received much interest. The evolution of thermoelectric devices (TEDs) in building applications has seen substantial progress, marked by several key studies that have collectively advanced the technology. The pioneering work by Xu et al. (2007) laid the foundation with the introduction of an active building envelope (ABE) that integrated photovoltaic cells with solid-state thermoelectric modules (TEMs), setting a new direction for energy-efficient building designs [6]. This concept was rapidly tested in real-world conditions, as evidenced by their outdoor testing room established within a year [7]. Following this, Guillott et al. (2009) advanced the practical application of TEDs by developing a compact thermoelectric cooling device specifically for small-scale buildings, highlighting the potential for TEDs in enhancing occupant comfort [8].

In parallel, Ibáñez-Puy et al. (2009) made strides with their active façade system, which incorporated thermoelectric HVAC systems into building designs, demonstrating the feasibility of integrating TEDs into conventional HVAC systems [9]. The work by Liu et al. (2010), which introduced an active façade with TEMs and a heat sink, was particularly significant as it focused on controlling heat flux within building walls, further refining the role of TEDs in building thermal management [10].

A significant application concept occurred in 2018 when Ibañez-Puy et al. developed the ventilated active thermoelectric envelope (VATE), the first of its kind to integrate heating and cooling units into an active façade. This innovation was rigorously tested and analyzed, showcasing the envelope’s performance and potential for wider adoption [11]. Zuazua-Ros et al. (2018) refined this technology by presenting a modular VATE prototype, indicating a move towards scalable and customizable TED applications [12].

The refinement of VATE continued with Martín-Gómez et al. (2021), who addressed the issue of thermal bridges, a critical challenge in thermoelectric applications, thereby improving the overall efficiency of TED systems [13]. Zhao et al. (2020) introduced a novel approach by combining thermoelectric cooling with radiative sky cooling (RSC-TEC), which demonstrated significant energy-saving potential in a residential setting [14]. The work of Su et al. (2020) further expanded this concept by developing a hybrid envelope system (TEC-RSC) that not only reduced the thermoelectric load but also improved space cooling efficiency, marking a significant advancement in passive–active cooling strategies for buildings [15]. These studies showed the great potential, challenges, and advantages of incorporating thermoelectric devices in residential buildings, forming the foundation for the development of new prototypes and sustainable building solutions.

When extensively analyzing the potential of thermoelectric devices in residential buildings, it is crucial to explore their core component: the thermoelectric generator (TEG). First, a TEG is an energy harvesting system that directly converts temperature differences into electrical power through the Seebeck effect, where a voltage is generated across two different materials due to the temperature gradient between them [16].

A TEG is composed of multiple thermoelectric (TE) modules, each of which contains a parallel thermal and series electrical connection between a P-type and an N-type semiconductor [17]. TEGs are characterized by their compactness and reliability [18]. TEGs can operate for a prolonged period (reaching 30 years) while remaining soundless and free from any mechanical components. Moreover, because of their capability and advantages, TEGs are increasingly being considered for building energy systems, particularly for their integration with renewable energy sources and/or phase change materials (PCMs), waste heat recovery, and geothermal energy utilization. These applications highlight the versatility and potential of TEGs in enhancing the sustainability and energy efficiency of buildings. Particularly noteworthy is the integration of TEGs into various building elements, such as walls, windows, roofs, and other surfaces. This transformative approach effectively converts building components into active energy harvesting systems, representing a promising path toward achieving self-sufficiency in energy generation within the built environment.

While numerous review papers provide an overview of thermoelectric generator (TEG) applications in energy harvesting, most of these papers cover the evolution of application systems and a broad range of application areas, including the automotive industry, industrial waste heat recovery, aerospace, biomedical devices, renewable energy systems, consumer electronics, the military, and building construction [19,20,21,22,23,24,25]. Despite the increasing interest in thermoelectric energy harvesting, very few publications have thoroughly reviewed TEG applications in the building energy sector. The first notable review [26] focuses on thermoelectric materials used in construction, particularly cement- and concrete-based composites, as well as other TE materials and devices with potential in building components like windows and walls. The second review [27] examines control methods and key factors affecting thermoelectric systems across various fields but excludes thermoelectric generators and materials. In contrast, this research uniquely emphasizes the integration of TEGs into building envelopes and HVAC systems, addressing a specific gap by focusing exclusively on their architectural applications and their potential to enhance energy efficiency in buildings, extending beyond the scope of existing TED applications.

After this section, the methodology employed for conducting the review is presented in Section 2. Following that, Section 3 provides a fundamental introduction to thermoelectricity and an overview of the various types of TE materials. In Section 4, the multiple applications in different domains of the buildings are discussed. The outcomes and conclusion are outlined in Section 5 and Section 6.

2. Methodology

To explore the current state of TEG integration strategies in buildings and assess their performance, challenges, and potential applications, the process begins by identifying the core concepts of the topic, such as “thermoelectric generators” and “building integration.” Synonyms and related terms like “TEG”, “thermal energy conversion”, and “sustainable building” are then considered. Specific applications and contexts, including “building envelopes” and “HVAC systems”, are added to the list. Keywords are combined using Boolean operators (AND, OR) to refine the search. These keywords cover a comprehensive range of topics, including specific technologies like “thermoelectric wall”, “solar thermoelectric generator”, “TEG façade integration”, “thermoelectric waste heat recovery”, and “smart window”, as well as broader concepts like “net-zero building”, “green building”, and “energy-efficient buildings”. The results are analyzed to ensure comprehensive coverage of the relevant literature. The search for relevant documents was conducted using the Scopus, Google Scholar, and Web of Science databases, ensuring comprehensive coverage of available studies. This study focuses on documents published after 2010 and includes a wide range of scholarly works, such as review articles, technical reports, conference papers, books, theses, and research papers.

The selection process for eligible documents followed certain criteria. First, the study prioritizes research where TEGs are integrated into building envelopes or used for building energy harvesting. Studies focusing on thermoelectric materials, such as cement composites, or other thermoelectric devices, like TECs, were excluded to maintain the specific focus on TEG applications. Similarly, studies that discuss applications of other TE devices in buildings are also excluded, as the primary focus is on the application of TEGs in buildings. Second, the study emphasizes emerging technologies that show promising research outcomes. This indicates that the review prioritizes recent advancements in the field, giving more weight to studies conducted within the last five years. This ensures that the most up-to-date findings are included in the analysis. After applying these filtering criteria, this study selected 16 research papers that met the specified requirements for inclusion in the review.

3. Thermoelectricity and Thermoelectric Generators

The thermoelectric effect is based on the principles of the Seebeck, Peltier, and Thomson effects. In 1821, Seebeck [28] discovered a phenomenon in which a temperature difference at the junction of two different semiconductors generates an electric voltage, causing electrons to move and creating an electric field. The Seebeck coefficient (α) is the amount of voltage generated when there is a temperature gradient ($∆T$) across a material. For metals, this is regarded as being very low, at approximately 0 mV/K, but semiconductor materials are thought to have a much higher value, between 100 mV/K and 300 mV/K [29]. The Seebeck coefficient (α) is defined as

$$\propto ={\displaystyle \frac{∆V}{∆T}}$$

(1)

where $∆$V is the voltage variation in V and $∆$T is the temperature difference in K.

In 1834, the opposite of the Seebeck effect was discovered by Peltier [30]. The effect is named after Peltier and is a phenomenon where an electric current flowing through a junction of two different conductive materials can either absorb or release heat depending on the current direction, resulting in a temperature difference across the junction. This effect is used in thermoelectric coolers to create cooling or heating by controlling the direction of the electric current. According to Peltier, the heat absorbed at the junction (Q_c) is the product of the Peltier coefficient ($\pi )$ and the electric current flowing through the junction (I).

$${\mathrm{Q}}_{\mathrm{c}}=\pi ·I$$

(2)

In 1851, William Thomson discovered the Thomson effect, which is the generation of reversible heat when electrical current passes through a circuit composed of a conductive material that has a temperature difference along its length [31]. In 1909, the figure of merit (ZT) was calculated by Altenkirch [32], where a dimensionless ZT is closely related to the thermoelectric efficiency of TE materials. The ZT value should be as high as possible to ensure that any material is an effective thermoelectric material. The dimensionless ZT is defined as

$$ZT={\displaystyle \frac{{\mathsf{\alpha }}^2\sigma }{k}}T$$

(3)

where α is the Seebeck coefficient, σ is the electrical conductivity, K is thermal conductivity, and T is the absolute temperature. Prior to 1990, most researchers tried to find better thermoelectric materials, but their ZT value was always limited [33] due to the inherent trade-off between improving electrical conductivity and controlling thermal conductivity. The invention of thermoelectric modules in 1959 led to the present generation of thermoelectric modules and materials [34]. The TEG module is a model that integrates the Seebeck effect and the Fourier law of heat conduction to achieve heat regulation and energy transformation. It consists of multiple thermoelectric joints connected in series to increase the output voltage and in parallel to increase the output current [21]. Each junction consists of a p-type material and an N-Type material that are connected in series, grouped in pairs, and surrounded by a ceramic cover. To facilitate their electrical connection in series and their thermal connection in parallel, these junctions are connected using copper conductors. The approximate efficiency of a TEG can be defined as

$${\eta }_{TE,max}={\displaystyle \frac{∆T}{T_h}}{\displaystyle \frac{\sqrt{1+ZT}}{\left(\sqrt{1+ZT}\right)+\frac{T_c}{T_h}}}$$

(4)

where $∆T$ is the difference between the temperature on the warm side ($T_h$) and the cold side ($T_c)$ and the ZT is accessed at the mean temperature of the hot and cold side temperatures.

4. Case Studies of TEG Installations

The first part of this section focuses on presenting the most recent research and studies on the installation of TEGs in building envelopes and different building sections such as façades, walls, windows, and roofs. The second part focuses on non-integrated TEG applications for waste heat recovery, ventilation, and air-conditioning systems inside the building.

4.1. TEG Applications in the Building Envelope

4.1.1. Façade

Thermoelectric generators (TEGs) in building façades represent a promising yet underexplored area for energy harvesting and thermal management. Between 2013 and 2023, while seven studies [9,35,36,37,38,39,40] focused on thermoelectric energy harvesting in building façades, most focused on Peltier cells rather than TEGs. Only two studies conducted experimental investigations directly related to TEG applications in façades. This limited body of research highlights the current state of TEG applications in façades and underscores the need for further exploration to fully realize the potential of this technology in building energy systems.

One study (Figure 1) was conducted by Huang et al. [39] in 2023, which focused on the power generation performance of a novel solar ventilation façade wall integrated with a thermoelectric generator and a thermoelectric harvesting panel (SVF-TEHP), as shown in Figure 1. The system comprised glass, an air channel, and a TEHP with 127 pairs of p-type and n-type semiconductors connected in series. The study evaluated surface temperature changes, thermal–electrical properties under solar intensities, and the effects of channel height, air channel width, and TEHP thickness on system performance. It also compares SVF-TEHP, SVF, and CW and predicts the relationship between cooling load and TEHP output power. The study revealed a complex interplay between thermal insulation and power generation capabilities. At peak solar intensity (900 W/m²), the system demonstrated an optimal output power of 0.37 mW, showcasing its potential for energy harvesting. However, this was accompanied by a substantial increase in interior wall temperature, highlighting the challenge of heat management at high intensities. A key finding was the impact of thermoelectric arm length on system performance, with longer arms significantly improving both thermal and electrical performance. The study also provided promising economic analysis, suggesting a payback period of less than one year under optimal conditions. These results underscore the potential of SVF-TEHP systems for improving building energy efficiency, particularly in regions with high solar intensity.

The other study [40] was an experimental study using TEG modules on various types of building façades under different solar heating conditions, as shown in Figure 2. The TEG modules were applied to both typical structural facades (RC walls and curtain walls) and non-structural facades (cement mortar blocks, detached planks, and mPCM honeycomb wallboards) to observe their performance and energy generation potential at different temperatures. The TEG module employed in this study comprised eight TEG cells connected in series, positioned between two copper plates, as shown in Figure 2a,b.

The results showed that applying TEGs to a typical structural façade using a 25 cm thick reinforced concrete wall achieved a peak electricity generation of 100.0 mW/m². This finding demonstrates the potential for meaningful energy harvesting in real-world applications. For non-structural façades, the study highlighted the benefits of integrating TEGs with phase change materials (PCMs). The TEG attached to a 2.5 cm thick microencapsulated PCM honeycomb board showed the highest energy ratio when considering indoor heat gain. This suggests that combining TEGs with thermal storage materials can enhance overall system performance. The study also provided valuable comparative data, showing that TEG façades can significantly outperform conventional wall systems in terms of thermal insulation. These experimental results validate the potential of TEG façades for both energy harvesting and thermal management in buildings, while also highlighting the importance of façade design and material selection in optimizing performance.

Both studies highlight several key parameters that significantly influence the performance of thermoelectric generator (TEG) façades. Solar intensity emerges as a critical factor, with both studies demonstrating improved power generation and thermal management at higher intensities. Huang et al.’s [39] simulations showed that increasing solar intensity from 100 W/m² to 900 W/m² led to a 26.1 °C rise in interior wall temperature, emphasizing the challenge of heat management at high intensities. The studies also underscored the importance of TEG design parameters, particularly the length of the thermoelectric arm. Huang et al. [39] found that increasing TEHP thickness from 4.3 mm to 10.3 mm resulted in a 71.93% increase in electrical efficiency. Similarly, Win et al. [40] observed that the configuration of the façade, such as the use of reinforced concrete or the integration of phase change materials (PCMs), significantly impacted performance. These findings suggest that optimizing both environmental conditions and system design is crucial for maximizing the dual benefits of power generation and thermal management in TEG façades.

4.1.2. Walls

Ko and Jeong [41] investigated the potential of an energy generation system by combining TEGs, PCMs, and building-integrated photovoltaic (BIPV) panels, as shown in Figure 3. The proposed BIPV-TEG-PCM system aims to harvest additional electricity output through the Seebeck effect by reducing solar cell temperatures. The researchers determined the optimal melting temperature and PCM thickness to maximize annual electricity generation based on calculations for 12 design days per month in a MATLAB simulation. This system utilized a PCM with a melting temperature of 35 °C and a thickness of 30 mm, which were both optimized for maximum energy output, leading to a 1.09% increase in annual energy generation compared to a standard BIPV system. Furthermore, the system exhibited seasonal improvements ranging from 0.91% to 3.16%, with the highest gains observed in winter. Theoretically, the proposed system holds the potential to increase energy generation by 4.47%, which can be achieved by minimizing thermal resistance and enhancing the thermoelectric generator’s performance.

Building on these findings, Kang et al. (2023) [42] enhanced the design by incorporating microencapsulated PCM (mPCM) and heat pipes, as shown in Figure 4. This iteration aimed to address practical issues such as leakage problem of previous design and improve heat transfer efficiency. The system demonstrated efficiency improvements of 2% in intermediate seasons and 2.5% in summer compared to conventional PV panels. In this study, a key innovation was the use of mPCM, which prevented leakage and improved long-term stability. The addition of heat pipes enhanced heat dissipation, which is crucial for maintaining the temperature difference across the TEG.

The 2024 study by Kang et al. [43] further refined the system by optimizing for five climate regions. This design considered additional parameters such as heat-fin spacing and TEG spacing. The study recommended maintaining mPCM phase change temperatures within 20–40 °C for hot and humid climates and determining optimal heat-fin spacing (≥200 mm) and TEG spacing (≥205 mm) for hot and humid conditions. Notably, in the latest 2024 research, PCM was less beneficial in colder, drier climates, highlighting the importance of climate-specific system designs.

In comparing these studies, Ko and Jeong’s [41] initial design demonstrated a modest but significant 1.09% increase in annual energy generation through optimized PCM properties, highlighting the system’s potential in reducing solar cell temperatures and improving efficiency. Kang et al. [42] enhanced this concept by incorporating microencapsulated PCM (mPCM) and heat pipes, addressing practical issues like leakage and heat transfer, and achieving further efficiency gains in various climates. The subsequent refinement in 2024 by Kang et al. [43] tailored the system to specific climate regions, underscoring the importance of climate-specific designs and revealing that PCM effectiveness varies significantly across different environments. Although the observed performance improvements are relatively modest, the potential for continuous power generation and enhanced PV efficiency makes the BIPV-TEG-PCM system a compelling area for future research, particularly in optimizing TEG efficiency, heat transfer mechanisms, and long-term durability for broader, cost-effective application.

Hong et al. [44] introduced a novel solar thermoelectric wall system with phase change material (STEW-PCM), as shown in Figure 5, designed to improve energy generation and indoor climate control in subtropical regions. The system, integrating a thermoelectric module with phase change materials (PCMs) and a concrete wall, demonstrated promising results, generating up to 24.62 V/m² during the day and 16.31 V/m² at night, sufficient to power small devices continuously. The optimization of PCM parameters, including melting temperatures and thickness, effectively balanced thermal regulation and electrical output. However, the study also highlighted key challenges, such as a relatively low energy conversion efficiency utilizing less than 25% of solar radiation and a high levelized cost of electricity (LCOE) of 35.37 c$/kJ, indicating the need for further refinement. Additionally, the system’s performance showed significant seasonal variation, pointing to its sensitivity to climatic conditions. While the STEW-PCM system offers substantial environmental benefits, including reduced cooling loads and CO₂ emissions, further research is necessary to enhance efficiency, reduce costs, and adapt the technology for broader climate applicability to fully realize its potential as a sustainable building-integrated energy solution.

4.1.3. Windows

The integration of TEGs onto window surfaces is explored in this section. The conventional application of TEGs to window glass is restrained by their lack of transparency in typical TEGs. To avoid diminishing the window’s architectural attractiveness, some researchers designed a TE system inside the window frame or on the outer corner of the window.

Indab et al. [45] placed TEGs directly on the window frame surface and conducted an experiment in a real-life environment, as shown in Figure 6. Their system used a harvesting circuit made up of a DC-DC boost converter, a power bank, and twelve TEGs, exposed to ambient air on one side and cooled by air conditioning on the other. The results showed that the highest voltage output of 0.61 W was achieved at approximately 2 p.m. when there was the highest temperature difference between the indoor and outdoor test rooms. This finding highlights the importance of considering temperature variations in TEG system design for windows. However, this approach may present challenges in terms of appearance and durability, as the TEGs are more exposed to environmental factors.

In contrast, Lin et al. [46] developed a novel TEG system entirely contained within a window frame, utilizing the temperature gradient between the indoor and outdoor environments. Their design incorporated a thermally optimized connector to efficiently direct heat from the window frame to the TEG surfaces, as shown in Figure 7. This approach resulted in a power output of 1.5 mW under a 6 °C temperature difference. The key innovation in their design was the use of a three-bridge internal structure for the thermal connector, which balanced heat transfer efficiency with minimal additional weight. This compromise was necessary because while a solid thermal connector would maximize heat transfer, it would also significantly increase the window’s weight and cost. Their energy equilibrium analysis demonstrated that with proper engineering, this system could achieve self-powered operation in various climates, addressing the long-standing issue of battery life in wireless sensor networks for smart buildings.

Both studies used aluminum as a window frame material, and the use of aluminum material introduces both opportunities and challenges for TEG integration. Aluminum’s high thermal conductivity allows for efficient heat transfer to the TEG hot side, potentially improving power generation. However, this same property can also lead to increased heat loss from the building interior in cold climates if not properly insulated. Therefore, further research on novel frame designs that balance thermal, electrical, and structural requirements could lead to optimized window-integrated TEG systems. Both studies underscore the potential of window-integrated TEGs for energy harvesting in buildings, but they also reveal the complex trade-offs between power output, system integration, and practical implementation that must be carefully balanced in future designs.

4.1.4. Roofs

The integration of thermoelectric generators (TEGs) into building roofs presents an innovative approach to harvesting solar energy, as demonstrated by the studies of Ilahi et al. (2015) [47] and Tong and Yang (2022) [48]. These works offer contrasting yet complementary perspectives on the challenges and potential of roof-based TEG systems.

Ilahi et al.’s study [47], focusing on Pakistan’s climate, proposes a relatively straightforward TEG integration method using a glazed glass insulation layer, as shown in Figure 8. This approach is particularly relevant for regions with high solar irradiance, where roof temperatures can reach 45–50 °C during summer. That design aims to maximize the temperature differential between the sun-exposed surface and the air-conditioned interior, which is crucial for TEG efficiency. However, the study’s reliance on air conditioning to maintain the cold side temperature raises questions about the system’s net energy benefit. While the authors estimate a potential power generation of 40 kWh per m² for summer months, this figure seems optimistic and may not account for the energy consumed by air conditioning or potential heat gain through the roof.

In contrast, as illustrated in Figure 9, Tong and Yang’s research [48] presents another approach, utilizing Al-Si alloy tiles as the heat-absorbing medium. That study developed deeper into the material science aspects, exploring how the thickness, shape, and composition of the tiles affect heat transfer and energy storage. The research highlights the importance of optimizing tile design and material selection for enhancing solar energy utilization in building applications. The research found that the plane tile model with a 3 × 3 arrangement of heat sink bosses offers a balanced approach, optimizing both heat absorption and transfer efficiency. The use of an Al-Si alloy is particularly intriguing due to its high thermal conductivity and specific heat capacity, potentially offering superior performance compared to traditional roofing materials. The results indicated that the ideal thickness of the Al–Si alloy sample combined with a heat sink boss was determined to be 10 mm to achieve maximum heat transfer efficiency. When applied practically, a 500 × 500 × 5 mm tile with nine evenly distributed 50 × 50 × 5 mm TEG modules can generate 163.8 mW of electricity. With 10 such tiles, a total power output of 1.64 W is achieved. However, the observed energy loss during experiments highlights a common challenge in scaling theoretical models to real-world applications. This underscores the need for ongoing refinement in material composition, heat sink design, and system integration to enhance efficiency and make TEG tiles a more practical and cost-effective solution.

Both studies highlight the critical role of temperature differentials in TEG performance. However, they approach challenges differently. Ilahi et al. [47] rely on the natural temperature gradient between the roof and air-conditioned interiors, which may not be applicable in all building types or climates. Tong and Yang’s approach of optimizing the tile design for heat absorption and transfer offers a more universally applicable solution, though it results in lower power output estimates [48]. A key limitation in both studies is the relatively low conversion efficiency of current TEG technology. Future research in this field must prioritize the development of more efficient thermoelectric materials suitable for the temperature ranges encountered in roofing applications.

4.2. Non-Integrated Thermoelectric Generator Applications

4.2.1. Energy Harvesting from Waste Heat or Temperature Gradients in Buildings

A TEG can also be used to generate energy by capturing temperature gradients or waste heat inside a building, and the harvested energy can power low-power applications, e.g., wireless network sensors and nodes in buildings. In 2013, Wang et al. [49] made significant strides in thermoelectric energy harvesting for building energy management (BEM) wireless sensor networks (WSNs). As shown in Figure 10, the thermoelectric energy harvester comprised a TEG, charge pump, switching regulator, and DC/DC converter, representing a comprehensive approach to energy conversion and management. Specifically, the system was evaluated for hot side temperatures ranging from 60 °C to 80 °C, with corresponding TEG output voltages of approximately 0.25 V to 0.45 V. Notably, the device achieved a 25% end-to-end conversion efficiency across a wide range of input conditions. The authors demonstrated that their harvester could power WSN modules with a 1.7% duty cycle when placed on a typical wall-mounted heater at 60 °C surface temperature, surpassing the required duty cycle for many BEM applications. This achievement was particularly significant given the challenges of harvesting energy from the relatively small temperature differentials typically found in buildings. However, the study’s focus on higher temperature sources (60 °C and above) raises questions about the system’s performance on more common, lower-temperature surfaces in buildings. Additionally, while the efficiency was impressive for thermoelectric systems of that time, it still highlighted the need for further improvements to compete with other energy harvesting technologies. Future work could explore the system’s performance at lower temperatures that are more representative of typical building surfaces, as well as strategies for miniaturization to enhance practical deployment potential.

Al Musleh et al. [50] conducted a comprehensive study on thermoelectric generator (TEG) characterization for building applications in extreme hot climates, focusing on extra-low temperature differences. Their approach combined experimental measurements with numerical modeling to evaluate the performance of energy harvesting blocks as shown in Figure 11, in the unique environmental conditions of the United Arab Emirates. The researchers developed a novel experimental setup and a corresponding COMSOL Multiphysics model to simulate TEG behavior under various conditions. Notably, they achieved a peak electrical efficiency of 5.2% for their TEG system at a normal solar irradiance of 1000 W/m², which is an impressive figure for non-concentrated TEG systems. Additionally, they demonstrated that their energy harvesting block could produce 22 mW of matched load output at a temperature difference of just 10 °C. This performance is particularly noteworthy given the challenges of harvesting energy at such low temperature gradients. The authors also provided a valuable analysis of the impact of various design parameters, such as TEG material properties and heat management strategies, on overall system efficiency. While these results are promising, it is important to note that real-world performance may vary due to fluctuating environmental conditions and long-term degradation effects, which need further investigation. Additionally, the economic viability of implementing such systems at scale in buildings remains an open question that future studies should address. The study’s findings are significant not only for demonstrating the potential of TEG technology in challenging environmental conditions but also for providing concrete data on system performance under low-temperature-gradient conditions, which could inform future research and development efforts in this field.

Byon and Jeong’s study [51] makes significant progress in building-integrated energy harvesting through their innovative thermoelectric generator-based block that incorporates phase change materials (PCMs), as shown in Figure 12. The findings of annual electricity generation at 2.1 kWh/m², with average power and voltage outputs of 0.03 W and 0.3 V, respectively, highlight the system’s potential for continuous, low-maintenance operation, especially given its passive design that leverages waste heat from building walls. While these outputs might initially appear modest, the real value lies in the system’s ability to utilize waste heat from building walls. The integration of PCM for thermal management is particularly noteworthy, addressing the intermittent nature of waste heat availability. Importantly, the study provides valuable long-term performance data, which are often missing in similar research and provide a concrete basis for comparison with other energy harvesting technologies. However, future work should explore the system’s scalability, economic viability, and potential optimizations for various climatic conditions. While the study represents a significant step forward, further research is needed to enhance power output and explore integration with building management systems to fully realize the technology’s potential in contributing to more energy-efficient buildings.

In a study conducted by Ko et al. [52], three types of energy harvesting blocks with thermoelectric generators and phase change materials with different melting temperatures (26 °C, 38 °C, and 47 °C) were explored under the climate conditions of Seoul. The innovative energy harvesting block design, as shown in Figure 13, features an inner envelope with a TEG-integrated heat sink that efficiently channels solar radiation to the PCM, maximizing the temperature differential across the TEG surfaces and consequently enhancing electricity generation through two series-connected TEGs within each dimension. The configuration with a 26 °C melting temperature exhibited a striking 46.5% and 66.5% increase in estimated annual energy generation compared to the 38 °C and 47 °C configurations, respectively, emphasizing the crucial role of PCM selection in optimizing TEG systems. However, while the 26 °C PCM proved highly effective in Seoul’s specific climate, its performance may not be as favorable in other regions with different temperature profiles. The study’s approach of testing multiple PCM configurations provides valuable insights into system optimization, but future research could benefit from exploring an even wider range of melting temperatures and considering the impact of factors such as PCM thermal conductivity and latent heat capacity. This research makes a significant contribution to the field by highlighting the potential for substantial efficiency gains through careful PCM selection in TEG-based energy harvesting systems.

Chen et al. [53] proposed an innovative low-concentration photovoltaic/thermal–thermoelectric generator (LCPV/T-TEG) hybrid system, utilizing a compound parabolic concentrator, double-glazing PV panel, and microchannel heat pipe array, as shown in Figure 14. A key feature of this design was the strategic placement of the TEG on the cold side of the heat pipe array, serving dual purposes of cooling the LCPV/T system and generating additional electricity. This configuration demonstrated remarkable outcomes, achieving a daily average overall efficiency of 57.03%, with thermal, PV, and TEG efficiencies of 45.0%, 11.8%, and 0.23%, respectively. Additionally, the authors’ outdoor experiments in Beijing provided valuable real-world validation of the system’s performance.

Building upon this concept, Zhang et al. [54] further explored the potential of integrating TEGs with LCPV/T systems. As shown in Figure 15, Zhang et al. directly connected 40 series-connected TEGs to the LCPV/T collector, prioritizing electrical output from the PV component with TEGs playing a supplementary role. While the overall architecture was similar to Chen et al.’s work, Zhang et al. focused on optimizing the system for domestic hot water production, achieving temperatures up to 52.96 °C in summer conditions. The electrical performance was notable, with a daily average power output of 436.13 W at 14.34% efficiency. However, the contribution from the TEG module was relatively modest, generating an additional 1.68 W or 0.385% of the total electrical output.

Comparing these two studies reveals an interesting trade-off in system design and performance. Chen et al.’s approach prioritized overall system efficiency through careful thermal management, resulting in a lower but more balanced contribution from each component [53]. In contrast, Zhang et al. [54] optimized their system for higher electrical output from the PV component, with the TEG playing a more supplementary role. This difference highlights the importance of system integration and the need to carefully consider the intended application when designing hybrid energy harvesting systems. Future research could explore optimizing the balance between these approaches, potentially through advanced control strategies or innovative thermal management techniques, to further enhance the viability of LCPV/T-TEG systems for building energy applications.

Lv et al. [55] developed a high-performance STEG system that consists of thermoelectric generators, solar selective absorbers, and a heat pipe evacuated tubular collector, as shown in Figure 16. The experiment underwent a comprehensive optimization process that encompassed the selection of thermoelectric materials, improving the optical and thermal efficiency of the solar selective absorber, enhancing heat management, and ensuring effective device integration. Experimental results demonstrated a significant enhancement in the electrical efficiency of the STEG unit, achieving 7.17% under a solar irradiance of 1032 W/m² and 5.2% under a solar irradiance of 1021 W/m². However, this raises concerns about the long-term stability and degradation of these materials under high temperatures in real-world conditions. While the controlled environment results are promising, it would be crucial to conduct extended testing under varying weather conditions to assess durability and longevity. Additionally, the economic feasibility of using these high-performance materials in large-scale production remains uncertain. The authors’ suggestion of a potential cost below USD 1/W by incorporating waste heat utilization is intriguing but requires further validation through detailed cost analysis and scale-up studies.

Ji and Lv [56] addressed the challenge of combining RSC and thermoelectric generators and proposed a simple, cost-effective RSC-TE system, as shown in Figure 17. The RSC-TE system was developed using a modified TiO₂/PMMA radiative cooling film, a commercial TEG, and an aluminum heat sink, and the performance of the RSC-TE system was investigated during nighttime operation. The authors investigate several key parameters affecting system performance, including the temperature difference across the TEG (2.3–3.2 °C), environmental conditions, and radiative cooler design. The analysis of these parameters provides valuable insights for system optimization. For instance, the study found that the system performs better in autumn, likely due to more favorable environmental conditions. The impact of wind speed on convective heat transfer is also examined, though humidity effects could have been explored further. However, the overall conversion efficiency remains low, highlighting the challenges of harvesting energy from small temperature gradients.

4.2.2. HVAC Systems

Cai et al. [57] introduced an innovative thermoelectric ventilation (TEV) system powered by a concentrated PV-TE generator (CPV-TEG). The CPV-TEG system, which directly converts solar energy into electricity, is shown in Figure 18. Their research demonstrated that the CPV-TEG system could produce up to 154 W of power at a maximum concentration ratio of 5, with a notable 14% increase in power output achieved by strategically positioning the TE generator behind the panels. This setup effectively met the energy requirements of the TEV system for both cooling and heating modes, particularly when input currents were kept below 2.5 A for cooling and 2.8 A for heating. The study also highlighted the system’s efficiency in different seasonal conditions, with energy and exergy efficiencies of 1.67% and 0.24% in winter heating mode, significantly outperforming those in summer cooling mode. While these findings underscore the system’s strong potential for winter applications, the lower efficiency in summer raises important considerations for optimizing performance in regions with high cooling demands. Further research could focus on enhancing the system’s summer efficiency, possibly through improved thermal management or the use of materials better suited to high-temperature conditions. Additionally, exploring the economic feasibility of scaling up this technology for widespread implementation will be crucial for its broader adoption. Overall, Cai et al.’s work represents a significant advancement in the development of energy-efficient building systems, with promising applications across different climates and seasons.

To provide a detailed comparison of the conversion efficiency across various thermoelectric generator (TEG) applications,

Table 1. Comparison of conversion efficiency: integrated vs. non-integrated TEG applications.

Integration Type	Study/Reference	Conversion Efficiency	Observations
Integrated	Huang et al. (2023) [39]	0.0324%	Very low efficiency in solar ventilated façade application; requires significant improvement for practical use.
Integrated	Win et al. (2023) [40]	Up to 100.0 mW/m2 (power density); specific conversion efficiency not calculated.	High power density on reinforced concrete façades; highlights potential for structural materials.
Integrated	Ko and Jeong (2023) [41]	1.09% annual energy increase; potential overall increase of 4.47% with PCM optimization.	Moderate efficiency increase in BIPV-TEG-PCM systems; efficiency varies with seasons, optimized for winter.
Integrated	Hong et al. (2023) [42]	<25% energy conversion; specific efficiency depends on solar radiance and PCM performance.	Low energy conversion efficiency in solar thermoelectric walls with PCM; practical deployment needs improvement.
Integrated	Lin et al. (2023) [45]	1.5 mW power output under 6 °C temperature difference; specific conversion efficiency not calculated.	Limited power generation in window frame applications; useful for low-power smart sensor applications.
Integrated	Tong and Yang (2022) [48]	7.17% electrical efficiency under 1032 W/m2 solar irradiance; 5.2% under 1021 W/m2 solar irradiance.	Relatively high efficiency for roof-based STEG systems; promising for specific high solar irradiance regions.
Non-Integrated	Wang et al. (2013) [49]	25% end-to-end conversion efficiency for waste heat recovery in wireless sensor networks.	High efficiency in waste heat recovery; effective for building management systems.
Non-Integrated	Al Musleh et al. (2023) [50]	5.2% peak electrical efficiency; 22 mW output at 10 °C temperature difference.	Moderate efficiency for energy harvesting blocks in extreme hot climates; effective under low-temperature gradients.
Non-Integrated	Byon and Jeong (2023) [51]	2.1 kWh/m2 annual energy generation; average power output of 0.03 W; average voltage of 0.3 V.	Moderate power generation in PCM-integrated blocks; continuous energy harvesting potential from waste heat.
Non-Integrated	Ko et al. (2023) [52]	46.5% annual energy increase with optimized PCM (26 °C melting temperature) compared to other configurations.	Significant efficiency gain with proper PCM selection; efficiency is highly dependent on local climate conditions.
Non-Integrated	Chen et al. (2023) [53]	57.03% overall system efficiency (thermal efficiency 45.0%, PV efficiency 11.8%, TEG efficiency 0.23%).	Very high overall efficiency in LCPV/T-TEG hybrid system; TEG contributes modestly compared to other components.
Non-Integrated	Zhang et al. (2023) [54]	14.34% (PV efficiency); TEG contributed 0.385% of total energy output in optimized LCPV/T-TEG system.	High PV efficiency; TEG plays a supplementary role with minimal contribution.
Non-Integrated	Lv et al. (2023) [55]	7.17% electrical efficiency under 1032 W/m2 solar irradiance; 5.2% under 1021 W/m2 solar irradiance.	High efficiency for roof-based systems; concerns about long-term material stability under real-world conditions.
Non-Integrated	Ji and Lv (2023) [56]	Low efficiency; open circuit voltage of 87 mV with a 2.3–3.2 °C temperature difference.	Low efficiency in RSC-TEG systems; suitable for small temperature gradients but needs significant optimization.
Non-Integrated	Cai et al. (2023) [57]	1.67% energy efficiency in winter heating mode; 0.24% exergy efficiency.	Low efficiency in CPV-TEG systems for HVAC; better performance in winter than summer.

summarizes key findings from both integrated and non-integrated systems. The table highlights differences in conversion efficiency and observations, illustrating the strengths and limitations of each approach. This comparative analysis underscores the varying effectiveness of TEG applications depending on integration and non-integration methods.

5. Discussions and Future Research Directions

Thermoelectric generators (TEGs) have demonstrated considerable potential when integrated into various building components, including façades, windows, roofs, and HVAC systems. For example, façade-integrated TEG systems have been shown to generate up to 100.0 mW/m² of electricity [40], while TEGs installed in window frames can produce 1.5 mW under a 6 °C temperature difference [46]. Roof-based TEG systems have also exhibited promising results, with potential outputs reaching up to 163.8 mW per tile [48], underscoring the versatility of TEGs in enhancing energy efficiency across different building structures.

Beyond integrated applications, TEGs have shown potential in harvesting energy from waste heat sources within buildings. Certain non-integrated TEG systems have achieved an impressive 25% end-to-end conversion efficiency, suitable for powering wireless sensor networks [49], while others have reached a peak electrical efficiency of 5.2% under normal solar irradiance [50]. Additionally, the integration of TEGs with other technologies has yielded particularly promising outcomes. For instance, hybrid systems that combine TEGs with concentrated photovoltaic thermal (LCPV/T) technology have achieved overall efficiencies of up to 57.03% [53]. The incorporation of phase change materials (PCMs) with TEGs has further improved performance and thermal management [51,52], demonstrating the potential for synergistic benefits when combining TEGs with complementary technologies.

Based on the studies, the performance of TEG systems in building applications is influenced by several critical parameters. Solar intensity is a key factor, especially when TEGs are integrated into buildings, as higher intensities typically lead to improved power generation. However, this also introduces challenges in heat management. For instance, increasing solar intensity from 100 W/m² to 900 W/m² resulted in a 26.1 °C rise in interior wall temperature, highlighting the necessity of effective thermal management strategies to prevent overheating [39]. The length and thickness of thermoelectric arms in TEG systems also play a significant role in electrical efficiency. Research has shown that increasing the thickness of thermoelectric heat pumps (TEHPs) from 4.3 mm to 10.3 mm can result in a 71.93% increase in electrical efficiency, demonstrating the importance of carefully designing these components to enhance performance [39]. Similarly, the configuration of heat sinks is critical for the effectiveness of TEG systems. Optimal heat-fin spacing (≥200 mm) and TEG spacing (≥205 mm) have been identified for hot and humid conditions, ensuring that heat is effectively dissipated and overall system efficiency is improved [43].

Material selection is another crucial factor, particularly in the heat-absorbing medium of TEG systems. For example, Al-Si alloy tiles have shown promise, with an ideal thickness of 5 mm achieving maximum heat transfer efficiency [48]. The appropriate selection of materials can significantly enhance both the thermal conductivity and electrical output of TEG systems. The integration of PCMs with TEGs is also vital, as the melting temperature of the PCMs plays a pivotal role in system performance. For instance, using a PCM with a melting temperature of 26 °C led to a 46.5% increase in annual energy generation compared to a PCM with a higher melting temperature of 38 °C [52], suggesting that selecting PCMs with appropriate phase change temperatures tailored to the local climate can greatly enhance TEG efficiency. The TEGs with PCM in this study are limited to the used PCM, the geometric configuration, and the chosen parameter ranges. In-depth investigations into the behavior of PCM in practical applications are needed. In hybrid systems such as LCPV/T-TEG, the concentration ratio, which determines the amount of sunlight focused on the TEGs, is a critical parameter. A maximum concentration ratio of 5 has been found to produce up to 154 W of power, emphasizing the importance of optimizing this parameter to maximize energy generation [57].

Lastly, environmental conditions such as ambient temperature, wind speed, and humidity significantly impact TEG performance. Studies have shown that TEG systems often perform better in autumn due to more favorable environmental conditions, underlining the importance of designing systems that are specific to the climate in which they will be used [50,56].

Overall, while the studies reviewed provide valuable insights into the performance of TEGs in various building applications, they also highlight the need for continued research and development to overcome the challenges of efficiency, cost, and integration.

Future Research Directions

Given the insights from the current studies, several areas of future research are recommended to advance the application of TEGs in building environments:

1. Efficiency Improvements: Despite advancements, the overall efficiency of TEG systems remains relatively low. Future research should focus on developing more efficient thermoelectric materials tailored for building applications and optimizing system designs to maximize temperature differentials and heat transfer [53,54].

2. Cost-Effectiveness: The economic viability of TEG systems is a major challenge. Reducing manufacturing costs and conducting comprehensive life-cycle cost analyses are essential to demonstrate the long-term benefits of TEG technology in building applications [51].

3. Integration and Scalability: As TEG technology transitions from laboratory research to real-world applications, challenges related to system integration and scalability must be addressed. This includes developing standardized methods for integrating TEGs into building components [39,46] and investigating large-scale system performance in various climatic conditions [50,56].

4. Environmental Impact: The long-term environmental impact of TEG systems, including their carbon footprint, requires further study. It is crucial to assess the sustainability of TEGs in comparison to other renewable energy technologies [44].

5. Smart Building Integration: Future research should explore how TEG systems can be integrated with smart building management systems to optimize overall energy performance, contributing to more intelligent and efficient building designs [49].

6. Climate-Specific Designs: The performance of TEG systems is highly dependent on environmental conditions, such as solar intensity, ambient temperature, and wind speed [39,40,41,42,43,44,45,46,47,48]. Future studies should explore climate-specific designs that can optimize TEG performance for different geographic regions [50,56].

7. Long-term Performance and Durability: Many current studies focus on short-term performance metrics. Future research should investigate the long-term durability and performance of TEG systems, particularly in real-life conditions where factors such as weathering and material degradation could impact efficiency.

8. Hybrid System Optimization: For hybrid systems combining TEGs with other energy technologies, further research is needed to optimize the balance between different energy generation components. This could involve developing advanced control strategies and exploring innovative thermal management techniques [53,54,55,56].

In summary, the integration of thermoelectric generators (TEGs) in building applications presents significant opportunities and challenges, as highlighted in the various case studies discussed.

Table 2. Summary of key findings from TEG applications in building systems.

Application	TEG Form	TEG Design	Output Power	Key Findings	Ref
Structural and Non-Structural Façades	Integrated into various structural/non-structural façades	TEG modules on RC walls, hollow copper curtain walls, cement mortar blocks, aluminum honeycomb structures	100.0 mW/m2 (RC wall), 48.0 mW/m2 (curtain wall), 62.3 mW/m2 (mortar block), 61.3 mW/m² (PCM honeycomb board)	High power generation for structural façades; non-structural façades show significant power with balanced energy and thermal management	[39]
Solar Ventilated Façade (SVF-TEHP)	Integrated into Solar Ventilated Façade	TEHP in solar ventilated channels; varied channel width and thermoelectric arm lengths	0.37 mW at 900 W/m2 (SVF-TEHP), 0.231 mW at 70 mm width, 0.640 mW at 8 mm arm length	<1 year payback; increased interior wall temperature at high intensities; channel width and arm length impact performance	[40]
BIPV-TEG-PCM System	Integrated with BIPV System and PCM	TEGs with PCM (35 °C melting temperature, 30 mm thickness) to reduce solar cell temperatures and harvest additional electricity	1.09% increase in annual energy generation; seasonal improvements 0.91% to 3.16% (highest in winter)	Potential 4.47% energy increase by minimizing thermal resistance	[41]
Heat Pipe-Assisted BIPV-TEG-PCM System	Integrated with BIPV, PCM, and Heat Pipe	Enhanced BIPV-TEG-PCM with microencapsulated PCM (mPCM) and heat pipes	Efficiency improvements of 2% in intermediate seasons, 2.5% in summer	Improved long-term stability and heat transfer; addresses leakage issues	[42]
Climate-Specific BIPV-TEG-PCM System	Integrated with BIPV and PCM	Optimized for 5 climate regions; TEG spacing ≥205 mm, heat-fin spacing ≥200 mm	Performance varies by climate; PCM less beneficial in colder, drier climates	Recommended mPCM temps 20–40 °C for hot, humid climates; highlights climate-specific design needs	[43]
Solar Thermoelectric Wall with PCM (STEW-PCM)	Integrated into Building Wall with PCM	TEG with concrete wall and PCM for energy generation and climate control in subtropical regions	Up to 24.62 V/m2 (daytime); 16.31 V/m2 (nighttime)	Low energy conversion (<25% of solar radiation), high LCOE (35.37 c$/kJ)	[44]
TEG on Window Frame	On window frame surface	12 TEGs on window frame with harvesting circuit, DC-DC boost converter, power bank; cooled by AC on one side	0.61 W at peak (2 p.m.)	Highest voltage at peak temperature difference; exposed to environmental factors affecting durability and apparance	[45]
TEG Inside Window Frame	Fully contained within window frame	Thermally optimized connector, three-bridge internal structure	1.5 mW under 6 °C temperature difference	Novel design balances heat transfer efficiency with minimal weight; self-powered for smart building sensors	[46]
TEG with Glazed Glass Insulation	Integrated into rooftop with glazed glass insulation	Uses temperature differential between sun-exposed surface and AC interior	Estimated 40 kWh/m² for summer months	Potential in high solar regions; concerns about net energy benefit due to AC reliance	[47]
TEG with Al-Si Alloy Roof Tiles	Integrated into Al-Si alloy roof tiles	TEGs with Al-Si alloy tiles (10 mm total thickness), 3 × 3 arrangement of heat sink bosses	1.64 W with 10 tiles	Al-Si tiles superior in heat storage/transfer; energy loss in real-world applications needs refinement	[48]
Thermoelectric Energy Harvesting for BEM	In BEM wireless sensor networks	TEG, charge pump, switching regulator, DC/DC converter for high-temperature surfaces (60–80 °C)	0.25 V to 0.45 V; 25% end-to-end conversion efficiency	Achieved 1.7% duty cycle, surpassing BEM requirements; low-temperature performance remains uncertain	[49]
TEG in Extreme Hot Climates	For building applications in extreme hot climates	Experimental measurements with numerical modeling for low temp differences (10 °C)	22 mW at 10 °C difference; peak electrical efficiency 5.2%	Notable for low temp gradient energy harvesting; challenges in scaling to real-world applications	[50]
PCM-Integrated TEG Block	In building walls with PCM	TEG with PCM for passive cooling, using waste heat from walls	2.1 kWh/m2 annually; average power 0.03 W, average voltage 0.3 V	Continuous, low-maintenance power for digital circuits; PCM crucial for heat management and energy harvesting	[51]
Energy Harvesting Block with TEGs and PCM	In energy harvesting blocks with TEGs and PCM	TEG-integrated heat sink with PCM layers (26 °C, 38 °C, 47 °C melting temps)	46.5% increase in annual energy with 26 °C PCM compared to 38 °C PCM	Significant efficiency gains with optimized PCM selection for specific climates	[52]
LCPV/T-TEG Hybrid System	In low-concentration PV/thermal (LCPV/T) system	Compound parabolic concentrator, double-glazing PV panel, microchannel heat pipe array	Daily average overall efficiency: 57.03% (thermal 45.0%, PV 11.8%, TEG 0.23%)	High overall efficiency: TEG contribution modest compared to PV and thermal components	[53]
LCPV/T-TEG System Optimization	In LCPV/T system with focus on domestic hot water production	40 series-connected TEGs directly on LCPV/T collector	Daily average output 436.13 W; TEG contribution 1.68 W (0.385% of total)	Optimized for higher PV output; TEG plays supplementary role	[54]
High-Performance STEG System	With solar absorbers and heat pipe evacuated tubular collector	Optimized TE materials, solar selective absorbers, heat management	Electrical efficiency 7.17% at 1032 W/m2; 5.2% at 1021 W/m2	Significant electrical efficiency enhancement; concerns about long-term stability and economics	[55]
RSC-TEG System	With radiative cooling and TEG	Modified TiO2/PMMA radiative cooling film, commercial TEG, aluminum heat sink	Open circuit voltage 87 mV (2.3–3.2 °C difference); max ΔT 3.19 °C, UTEG 115.82 mV in optimal conditions	Better performance in autumn; challenges in small temperature gradient energy harvesting	[56]
Thermoelectric Ventilation System	With Concentrated Photovoltaic (CPV) System	CPV-TEG behind panels, max concentration ratio 5; converts solar energy for HVAC	Power output 58.85–154.29 W depending on the concentration ratio 1.0–5.0	14% power increase by strategic TEG positioning; 1.67% energy efficiency, 0.24% exergy efficiency in winter heating; outperforms summer cooling	[57]

below summarizes the critical findings from different TEG installations, providing a clear and comparative overview of TEG form, design, output power, and key findings in studies related to building energy systems.

6. Conclusions

In summary, this review provides a comprehensive analysis of recent developments in thermoelectric generator (TEG) applications for buildings. The results indicate that TEG integration shows promise for improving sustainability and energy efficiency in the built environment. Integrating TEGs into façade, wall, window, and roof integrations demonstrates the potential for electricity generation, although further optimization is necessary to enhance performance. Non-integrated TEGs also effectively harvest waste heat and solar energy for power generation. However, challenges remain regarding efficiency limits, costs, material constraints, and system design optimization. While TEGs present a viable emission-free technology for buildings, continued research and development are important to unlock their full potential. Key areas for future work include advancing the materials used in thermoelectric systems, refining innovative designs, integrating systems, and conducting real-life condition studies. With concerted efforts to address current obstacles, TEGs can play an increasingly valuable role in building energy systems and contribute to a greener, low-carbon future.