**1. Introduction**

The increase in the energy consumption, the intensification of global warming and policies to reduce the need of fossil fuels have created interest in renewable energy sources (RES). The 2015 Paris Agreement has put more emphasis on international efforts to reduce carbon dioxide (CO2) emissions [1]. According to the International energy agency (IEA), the use of RES has increased significantly in recent decades. For instance, photovoltaic (PV) energy generation increased from 91 GWh in 1990 to 554,382 GWh in 2018 and wind energy has increased from 3880 GWh in 1990 to 1,273,409 GWh in 2018 [2]. According to IEA, around 26% of the global energy was provided through RES in 2018 [2]. With plans to increase the share of the RES by 32% in the European Union (EU) by 2030 [3] and to further reduce CO<sup>2</sup> emissions by 80% by 2050 [4], it is expected that the share of RES will increase on a yearly basis. However, the challenge still remains on the variability of the RES generation, which could result in putting pressure on the grid and ultimately,

**Citation:** Hedman, Å.; Rehman, H.U.; Gabaldón, A.; Bisello, A.; Albert-Seifried, V.; Zhang, X.; Guarino, F.; Grynning, S.; Eicker, U.; Neumann, H.-M.; et al. IEA EBC Annex83 Positive Energy Districts. *Buildings* **2021**, *11*, 130. https:// doi.org/10.3390/buildings11030130

Academic Editors:

Matheos Santamouris, Ambrose Dodoo, Ravi Srinivasan and Paulo Santos

Received: 31 December 2020 Accepted: 16 March 2021 Published: 20 March 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

in compromising the stability of the grid. Thus, power grids and energy systems have to be designed in a way that can regard such issues and challenges.

#### *1.1. Impact of Buildings and Districts on Greenhouse Gas Emissions*

An important sector that contributes significantly towards climate change and global warming is the building sector. Buildings account for 30–40% of global final energy consumption [5] and nearly 40% of the global CO<sup>2</sup> emissions. In the last decade, policies such as the Directive on Energy Performance of Buildings (EPBD) have been introduced to address the issue, aiming to decarbonize the building stock by 2050 and to reach nearly zero energy buildings (NZEBs) [6]. In 2009 ambitious energy and climate targets were set for 2020 (20% greenhouse gas emission reduction, 20% increase in efficiency and 20% increase renewable energy). After ten years, the EU in general is on track to achieve these targets, showing that GDP can be increased while reducing carbon emissions. In fact, by 2017 the EU's greenhouse gas (GHG) emissions decreased by 21.7% compared to the 1990 GHG emission levels [7]. In Canada, the residential sector is responsible for 16.6% of the energy consumption and 12.9% of GHG emissions [8]. Between 1990 and 2016, the residential sectors emissions have been reduced by 30.2 Mt CO<sup>2</sup> (27% of total) [8] through enhancing building codes, applying minimum energy performance standards for appliances, improving energy monitoring systems and home retrofits. Under the Paris Agreement, Canada committed to reducing its GHG emissions up to 30% below the 2005 level by 2030 [8]. Moreover, Canada announced a plan to set Canada on a net-zero emissions pathway by 2050. Canada's 2030 GHG emissions target is 511 Mt CO<sup>2</sup> eq, given a 2015 level of 815 Mt CO<sup>2</sup> eq [8]. Between nine principal sectors, buildings are committed to a 47 Mt CO<sup>2</sup> eq reduction [8]. The key priorities are increasing clean electricity, developing and implementing greener buildings and communities, and developing and implementing nature-based climate solutions.

The 2015 Paris Agreement has put more emphasis on international efforts to reduce CO<sup>2</sup> emissions, where urban areas with a 70% share of global emissions have a key role. Accordingly, the United Nations (UN) Sustainable Development Goals include as goal 11 "sustainable cities and communities" with the aim of supporting the transition towards low-carbon cities, in a general framework which also points towards, e.g., climate action, affordability, and clean energy. In 2015, when the Paris agreement was signed, the EU planned to move further ahead and reduce greenhouse gas emissions by 40% by 2030. In order to tackle this challenge and to lead the global energy transition, the EU Commission proposed in 2016 a set of new and ambitious rules known as the Clean energy package for all Europeans [5]. Therefore, to reach the emission reduction goals it is important to focus both at the energy systems level and at the buildings or district level.

#### *1.2. Near and Net Zero Energy Building/District Concepts*

Different NZEB, net zero energy or even zero energy building (ZEB) concepts have been developed and implemented in the building sector all over the world. According to the ZEB definition, "the building can be considered as ZEB after showing through actual measurements that the energy delivered to the building is less than or equal to the onsite renewable exported energy" [9]. Similarly, according to Article 2 of the Energy Performance of Building Directive (EPBD), the Nearly Zero Energy Building (NZEB) concept states that "'nearly zero-energy building' means a building that has a very high energy performance, as determined in accordance with Annex I. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby'" [10]. A similar concept exists in the United States of America (USA) that is called net ZEB [11] it states that annually a building uses less or equal energy generated from the renewable energy on a primary energy basis. Similarly, concepts exists in other places [12] such as net zero energy (NZE) housing in Canada [13], zero emission building in Australia [14] and in Korea [15], etc. However, ZEBs or Nearly Zero Energy Building (NZEBs) mostly relate to

individual building scales and do not consider the interaction with other energy consumers and producers. Nevertheless, ZEBs and NZEBs have recently received high academic and political interest around the world, as shown in Figure 1 [10,16–20]. Figure 1, x-axis shows the publication year, and the y-axis shows the cumulative number of documents published each year at the global level, for the keyword. The search is carried out using the keywords such as "nearly zero energy building", "zero energy building", "zero energy districts", "positive energy buildings" and "positive energy districts". The search is carried out from 1990 onwards until 2020 on Scopus [21]. It can be observed that interest and research are increasing each year for the ZEBs and NZEBs at the global level. Furthermore, since 2018, the positive energy district (PED) concept has come into the scene globally. mostly relate to individual building scales and do not consider the interaction with other energy consumers and producers. Nevertheless, ZEBs and NZEBs have recently received high academic and political interest around the world, as shown in Figure 1 [10,16–20]. Figure 1, x-axis shows the publication year, and the y-axis shows the cumulative number of documents published each year at the global level, for the keyword. The search is carried out using the keywords such as "nearly zero energy building", "zero energy building", "zero energy districts", "positive energy buildings" and "positive energy districts". The search is carried out from 1990 onwards until 2020 on Scopus [21]. It can be observed that interest and research are increasing each year for the ZEBs and NZEBs at the global level. Furthermore, since 2018, the positive energy district (PED) concept has come into the scene globally.

renewable sources, including energy from renewable sources produced on-site or nearby'" [10]. A similar concept exists in the United States of America (USA) that is called net ZEB [11] it states that annually a building uses less or equal energy generated from the renewable energy on a primary energy basis. Similarly, concepts exists in other places [12] such as net zero energy (NZE) housing in Canada [13], zero emission building in Australia [14] and in Korea [15], etc. However, ZEBs or Nearly Zero Energy Building (NZEBs)

*Buildings* **2021**, *11*, x FOR PEER REVIEW 3 of 18

**Figure 1.** Cumulative number of documents published each year on the "Nearly Zero Energy Building", "Zero Energy Building", "Zero Energy Districts", "Positive Energy Buildings" and "Positive Energy Districts" according to Scopus at the global level [21]. **Figure 1.** Cumulative number of documents published each year on the "Nearly Zero Energy Building", "Zero Energy Building", "Zero Energy Districts", "Positive Energy Buildings" and "Positive Energy Districts" according to Scopus at the global level [21].

#### *1.3. Reasons for Positive Energy District (PED) Solutions Instead of Building Level and ZEB Soultions* ZEB or NZEB buildings do not only consume, but also produce energy onsite. The *1.3. Reasons for Positive Energy District (PED) Solutions Instead of Building Level and ZEB Soultions*

energy grids have to be designed in a way that allows consuming from the grid and injecting energy from RES to the grid, which can be applied to all types of grids: district heating and cooling networks (DHCN), natural gas grids, and/or power grids. Regarding power grids, bi-directional grids are needed to solve the issue of flexibility. If such issues are not considered, curtailment of the excess energy produced by buildings will be needed to avoid frequency and grid issues. For instance, in Germany [22] and in Belgium [23], the excess Photovoltaic (PV) generation has a power restriction on the export to the grid. When it comes to heat, buildings can be heated by DHCN, but it does not always allow export and production of heat by buildings (only if substations allow prosumers). In cases where this is technically possible, the financial compensation for exported heat is low. In some countries, buildings are just heated by means of an on-site generation system that consumes from the natural gas grid. However, in the future it is expected that an RES ZEB or NZEB buildings do not only consume, but also produce energy onsite. The energy grids have to be designed in a way that allows consuming from the grid and injecting energy from RES to the grid, which can be applied to all types of grids: district heating and cooling networks (DHCN), natural gas grids, and/or power grids. Regarding power grids, bi-directional grids are needed to solve the issue of flexibility. If such issues are not considered, curtailment of the excess energy produced by buildings will be needed to avoid frequency and grid issues. For instance, in Germany [22] and in Belgium [23], the excess Photovoltaic (PV) generation has a power restriction on the export to the grid. When it comes to heat, buildings can be heated by DHCN, but it does not always allow export and production of heat by buildings (only if substations allow prosumers). In cases where this is technically possible, the financial compensation for exported heat is low. In some countries, buildings are just heated by means of an on-site generation system that consumes from the natural gas grid. However, in the future it is expected that an RES transition would occur in DHCN with the introduction of electrical heating systems (e.g., heat pumps) and prosumers, as well as the injection of hydrogen in natural gas grids. Utilizing waste heat streams from buildings and selling the waste heat to the DHCN is expected to grow [24,25]. Another aspect raised in the building sector is the inclusion of electro mobility within buildings and districts, such as a charging station for an electric-vehicle (EV). However, although the transport and mobility sector contributes 27% of the emissions in Europe, the NZEB/ZEB concepts [26] and EPB certificates (such as the ISO52000) usually omit the

EV load in the calculation process. Nevertheless, the transport and mobility sector are becoming increasingly important factors in the energy supply of populated districts, since the share of EVs is increasing rapidly at the global level. In fact, it is expected that by 2030, EV usage will increase to 44 million cars globally [27]. Many cities around the world are thus already including electrification of mobility in their city plans [28]. These EVs would increase the demand and load on the grids and they can also be used as peak savings with batteries. Other aspects, such as building mass and energy storage, have to be included in future energy systems [29]. Energy storage can provide needed flexibility and resilience to buildings [30]. All the above-mentioned issues and challenges call for large changes and renovation of the grids and energy systems so that all the issues can be addressed in an integrated and holistic way. These changes are needed at the district level rather than at the building level. Moreover, the aspects on better coordination between sectors (energy, building, mobility, etc.) and better integration of technologies (e.g., RES, EVs and other NZEB technologies) are other reasons to move from the building to the district level [31].

Various studies on buildings, smart grids and intelligent buildings have been carried out [32–34]. The flexibility and use of new technologies such as RES and storage can be increased by focusing at the district level, rather than at the building level. The research and testing of solutions are already moving from the building level to the district level. This would not only provide technically feasible solutions but also economically viable ones [35]. For example, the district energy refurbishment approach, already tested in some EU projects, leans on a set of innovative system integration activities at the district level and is geared to make the targeted district model robustly scalable and replicable and to maximize the multiple benefits creation [36,37]. Moreover, this would solve the grid and building-related emissions issues at a larger level. However, although the building level research on such topics has become well-structured in the past few years, the district level or, in particular, the positive energy district (PED) field is quite new, and it is developing on academic, scientific and business levels with time [38] as also shown in Figure 1.

#### *1.4. Positive Energy District (PED) Concepts, Aims and Connection with Zero Energy Concepts and International Energy Agency Energy in Building and Communiy (IEA EBC) Annexs*

A PED can be generally described as a district within a city that generates more energy than it consumes on an annual basis [39]. The aim of PED is not only to generate surplus energy, but rather to minimize the impact on the centralized grid by promoting higher self-consumption and self-sufficiency. The PED should offer options to increase the onsite load matching by allowing the integration of long and short-term storage and smart controls for improving the energy flexibility. This district level concept and its impact on flexibility, RES and storage integration are still in early stages globally, as shown in Figure 1. Therefore, a holistic approach is needed to define, develop, model and validate the PED concept in order to consolidate the PEDs. Moreover, as shown in Figure 2, the past research focus has been mainly on the ZEBs, intelligent buildings, energy efficiency, NZEB, RES, etc., at the global level. Therefore, Annex 83 will provide the needed platform to discuss and create a framework of PEDs considering the different urban contexts of the globe. According to the solar district heating database [40], there are approximately 195 pilot cases of different capacities of solar-based district heating systems operating in Europe. However, there is currently no insight into how the PEDs and their use in the future districts and cities would be able to provide the consumer-centric, bi-directional grids and districts that are emission-free and flexible. The PEDs can utilize the benefits of the building thermal mass, different typologies of energy storages, RES, electric mobility, demand side management, and flexibility options [30,41–43]. The district can also provide the advantage of shifting the demand, based on the functionality of the various buildings present in the district and this may assist in improving the energy flexibility at the building [44] and grid levels [45]. International Energy Agency Energy in Buildings and Communities (IEA EBC) Annex 83- Positive Energy Districts was developed to provide research contributions towards these fields, based on the outcomes of other IEA Annexes such as Annex 51 [46], Annex 60 [47], Annex 64 [48], Annex 67 [34], and Annex 73 [49].

[49].

**Figure 2.** The keywords used globally in the literature according to Scopus [21]. **Figure 2.** The keywords used globally in the literature according to Scopus [21].

The PED concept introduces an opportunity to develop a framework that introduces energy positivity on a district level, with clear guidelines for grid interaction, energy storage and renewable integration for both buildings and Electric Vehicles (EVs). The main principle of a PED is to create a district within the city that is capable of producing higher energy than it consumes, it is flexible to respond to the energy market situation and in addition to this, it contributes by improving the quality of life and wellbeing of the residents. The PED concept introduces an opportunity to develop a framework that introduces energy positivity on a district level, with clear guidelines for grid interaction, energy storage and renewable integration for both buildings and Electric Vehicles (EVs). The main principle of a PED is to create a district within the city that is capable of producing higher energy than it consumes, it is flexible to respond to the energy market situation and in addition to this, it contributes by improving the quality of life and wellbeing of the residents.

in the future districts and cities would be able to provide the consumer-centric, bi-directional grids and districts that are emission-free and flexible. The PEDs can utilize the benefits of the building thermal mass, different typologies of energy storages, RES, electric mobility, demand side management, and flexibility options [30,41–43]. The district can also provide the advantage of shifting the demand, based on the functionality of the various buildings present in the district and this may assist in improving the energy flexibility at the building [44] and grid levels [45]. International Energy Agency Energy in Buildings and Communities (IEA EBC) Annex 83- Positive Energy Districts was developed to provide research contributions towards these fields, based on the outcomes of other IEA Annexes such as Annex 51 [46], Annex 60 [47], Annex 64 [48], Annex 67 [34], and Annex 73

The PED conceptual framework will be in line with the nearly or net zero energy building/district concept. The detailed conceptual framework will be planned and designed in this Annex 83. The framework has to be designed in such a way that it can accommodate and consider the local challenges, urban context and regulations, etc. This will provide a basis to analyze various PEDs in different geographical locations. Annex 83 will focus and support the research and development of the PED concept, principles, and frameworks, while keeping the global perspective. The PED conceptual framework will be in line with the nearly or net zero energy building/district concept. The detailed conceptual framework will be planned and designed in this Annex 83. The framework has to be designed in such a way that it can accommodate and consider the local challenges, urban context and regulations, etc. This will provide a basis to analyze various PEDs in different geographical locations. Annex 83 will focus and support the research and development of the PED concept, principles, and frameworks, while keeping the global perspective.

#### *1.5. Challenges, Opportunites, and Global Perspectives Towards PEDs 1.5. Challenges, Opportunites, and Global Perspectives towards PEDs*

The PED includes all types of buildings present in the district environment and are connected with the energy grid. PED is a growing concept within the research community at the global level in order to create carbon neutral cities for the future. This Annex is one The PED includes all types of buildings present in the district environment and are connected with the energy grid. PED is a growing concept within the research community at the global level in order to create carbon neutral cities for the future. This Annex is one of the first initiatives that aims to coordinate such research on PEDs at the global level. The PED concept may have its limitations depending on the location, local regulations, technology and urban contexts. For example, Denmark's regulations force buildings to be connected to the green district heating network (which will be imports for the PED), leading to higher investments to achieve a positive balance. At the same time, Denmark allows the creation of district heating cooperatives, allowing them to lower the prices of the user [50]. The prosumer regulations are also different within the European Union (EU). While Spain's self-consumption regulation makes the balance on a monthly basis, Latvia does so on a yearly basis and both of them do not reimburse users if the exported energy exceeds their electricity consumption. The Netherlands make the balance yearly, reimbursing prosumers for their exports at the end of the year [51]. Spain and Latvia limit the installed capacity per each user (except if they form a cooperative) while the

Netherlands enable the concepts of aggregators, virtual power plants or peer-to-peer energy exchange. Looking to global contexts, China has very large regions, and not all of them are connected by means of an electric grid [52], which can mean that it is harder in some contexts to apply PEDs. A potential solution to this may be micro-grids with self-sufficient districts (also known as energy islands in some of the literature). The focus of Annex 83 is on the development of the PED concept and its application at the global level, therefore this Annex involves researchers and experts from around the world (i.e., from Europe, USA, Canada, China, Australia, Japan, United Kingdom, South Korea, Turkey etc.) to include the global perspective and challenges as discussed above.

In order to reach the PED, the district first requires higher energy-efficient buildings, secondly the use of carbon free energy renewable energy sources to meet the remaining demand and thirdly cascading local energy flows by making use of any surpluses. Better and smarter controls are needed to match the demand and supply locally and also to minimize the liability on the grid and maximize the effectiveness of PED on the grid. Moreover, since the objective is also to go beyond the fulfillment of a mere mathematical positive energy balance, a wide spectrum of initiatives and parallel objectives are included in the definition of PEDs including social concerns, inclusiveness, solutions to energy poverty, spatial and civic planning of the person building in addition to district wide considerations on the transportation networks and design optimization.

The intrinsic multi-dimensional nature of the design of PEDs requires the contemporary involvement on different levels: mathematical and energy modeling, social, environmental, economic performance assessment, interaction with stakeholders, diffusion of know-how in the territory investigated and creation of PEDs are able to spark the diffusion of these concepts on large scales.

The transition towards carbon neutral districts require multisector and multidimensional solutions. It embraces a synchronized and parallel development of instrumental technologies, public perceptions of building energy technologies, new economic paradigms, assessment approaches, and tailored business models. In this case cities can provide and act as a living lab to facilitate and incubate new technologies and solutions. This is needed in order to co-design all-inclusive packages of citizen's centric carbon-free energy solutions. A common platform is needed to facilitate such collaborations and Annex 83 will focus on providing it with the ultimate aim to generate opportunities for creating such interdisciplinary solutions. Table 1 shows some of the practical application of PEDs or zero energy concepts available.


**Table 1.** Positive and Zero Energy Concept application across the world including ZEBs and NZEBs.


**Table 1.** *Cont.*

<sup>1</sup> O = In Operation, P = In planning stage, I = In implementation stage, <sup>2</sup> ST = Solar thermal, PV = photovoltaic panels, PVT = photovoltaicthermal hybrid panels, W = wind turbine, MW = Micro-wind turbine, DHN = District heating network, GDN = Geothermal district network, SH = Social Housing, PH = Passive House, NZEB = Nearly zero energy building, REB = Retrofitted efficient buildings, BE = Bioenergy, WP = Wave power, GB = Geothermal boreholes, ES = Electric storage, EM = e-mobility (cars/bykes), WH = Waste Heat, MG = Micro grid, HP = Heat pumps, CHP = Cogeneration heat-power unit, CE = Circular economy perspective, STES = Seasonal thermal energy storage.

#### *1.6. Aim and Scope of This Article*

The aim of this article is to show the benefits and importance of scientific global level cooperation on the topic of PEDs. This article lays down and presents all the activities planned under each task and the objective of each tasks/subtasks under the proposed Annex 83 platform at the global level. This article provides an introduction to readers about the activities that are planned and in progress in IEA EBC Annex 83. It presents and provides for the Annex 83 project plan. Moreover, it introduces the current global interest of researchers in PEDs. This Annex will be conducted at the global level, in order to include a global perspective to the PEDs, as the topic is novel and requires a global collaboration.

The activities and tasks have recently started in Annex 83 from November 2020 and will continue up until the end of 2024. Under the planned Annex, all the outcomes, findings, new tools, and results will be presented and disseminated on various platforms and in scientific journals, reports, and books. As Annex 83 will progress for the next four years, all the challenges, such as climactic, geographical, regulatory framework, boundary conditions, stakeholders, technological approaches, as well as findings, will be disseminated. A flexible working definition of PED, case studies, development of methodologies, and tools will also be provided and discussed under the Annex.

#### **2. IEA ECB Annex83 Positive Energy Districts: Objectives of the Annex**

The International Energy Agency (IEA) has established an Implementing Agreement on Energy in Buildings and Communities (EBC). The function of the EBC program is to undertake research and provide an international focus for buildings and districts energy efficiency. Tasks are undertaken through a series of "Annexes", so called because they are legally established as annexes to the EBC Implementing Agreement. (https://www.ieaebc.org/ebc/about, accessed date: 20 November 2020).

The largest benefits arising from participation in EBC are those gained by national programmes, such as leverage of R&D resources, technology transfer, training and capacitybuilding. Countries lacking knowledge can benefit from the experiences of those with more expertise, thereby avoiding duplicated research efforts (https://www.iea-ebc.org/ ebc/about, accessed date: 20 November 2020).

The IEA EBC Research strategy states as an objective the following: "the creation of holistic solution sets for district level systems taking into account energy grids, overall performance, business models, engagement of stakeholders, and transport energy system implications". Annex 83, Positive Energy District answers directly this objective (https: //www.iea-ebc.org/strategy, accessed date: 20 November 2020).

The international cooperation between research institutions from different parts of the world brings many opportunities. Sharing of experiences between different climate regions, cultures and economic systems enables researchers to develop globally sustainable solutions that are implementable around the world. The overall knowhow and understanding, not only on PEDs, but on society and city development, is increased by an active inclusion of a wide range of stakeholders.

#### *2.1. Objectives*

The aim of Annex 83 is to develop an in-depth framework for the devising of PEDs including analyzing the technologies, planning tools and the planning and decision-making processes related to positive energy districts. Experience and data to be used in the Annex will be gained from demonstration cases.

Annex 83 aims to enhance the cooperation of PED development at an international level through collaboration within the initiatives of the IEA. The main objectives of Annex 83 are:

