In order to achieve the goals of the Paris Climate Agreement, global climate neutrality must be achieved before 2050. Cities play a crucial role in this, with over 50% of the world's population living in cities and this figure rising, while cities are responsible for 80% of greenhouse gas emissions [1]. The European Union supports the development of climate-neutral cities as part of the Strategic Energy Technology Plan (SET Plan) and has set itself the goal of implementing 100 Positive Energy Districts (PEDs) in Europe by 2025 [2]. To achieve this goal, the Action 3.2 Implementation Plan "Towards Positive Energy Districts for Sustainable Urbanization" was developed. It defines PEDs as energy-efficient districts that have net zero CO2 emissions and work toward local surplus production of renewable energy (RE) on an annual basis. These are also intended to help improve the quality of life in European cities, achieve the COP21 targets, and make Europe a global role model.
Districts are also an important field of research from the perspective of the federal government, as highlighted in the 7th Energy Research Program: "In addition to the development of individual building technologies and building-integrated renewable energy generation systems, the systemic interaction between buildings and with the energy infrastructure is gaining in importance. This applies both to highly densified urban districts [...] and to rural regions, where the decentralized use of locally and temporarily available renewable energies can relieve the burden on distribution networks" (page 23 in [3]). Thus, Germany also recognizes the need to develop climate-neutral districts that have a positive impact on the overarching energy systems. However, the European PED objective has not yet been adopted as a separate concept in Germany; instead, the general goal of CO2 or climate neutrality in districts has been pursued. This also makes it unclear whether these are comparable approaches under different names or different concepts. There is therefore a need to examine the compatibility of the concepts for the development of sustainable districts in Germany and other European countries and, where appropriate, to harmonize them in order to jointly achieve the most efficient, rapid, and successful spread of climate-neutral districts.
There is currently no suitable English translation for the term PED. The term "plus-energy district" would severely limit its applicability if the meaning of "plus-energy building" were to be transferred to the district level, as this would mean that more energy is generated than consumed in the district. However, this is only possible with a relatively low energy demand density, i.e., in highly efficient buildings with a small number of floors and large roof areas. Typical districts in medium-sized and large cities with large apartment buildings, commercial and industrial facilities can only meet this criterion in exceptional cases. In the opinion of the project consortium, however, PED status should be achievable by all districts if they are highly efficient in terms of their structural design, population density, and use, utilize a large proportion of their existing local renewable energy potential, and have a smart energy system with sector coupling, storage, and intelligent energy management in order to be as useful as possible to the upstream power grid.
The PED-urban project aimed to develop the theoretical foundations for PEDs, demonstrate them in the practical development of one climate-neutral district, and thus test their practical suitability. PED-urban therefore focuses on the questions of which energy system an urban district can use to optimally meet the PED criteria to be defined and how this can be efficiently planned, implemented, and operated. To this end, methods and tools for energy concept development and digital planning, as well as for optimized operation and monitoring, are being further developed and evaluated in practical use.
As part of the project, one urban districts will receive scientific support and guidance in its energy development to become a climate-neutral district in the sense of a PED. Advanced planning methods will be used to improve district planning. In the spirit of a real-world laboratory, feedback from project developers (municipal and private), energy suppliers, property owners, users, and residents will be used to optimize the definitions, methods, and tools and make them practical. The project aims to demonstrate the extent to which the PED concept for urban districts represents a practical and helpful objective and to provide general recommendations for the implementation and optimized operation of PEDs in urban districts.
The demonstration district is the Waldsee district in Freiburg, which is a typical existing district in a medium-sized city, primarily consisting of residential buildings. The city of Freiburg has set itself the goal of developing the Waldsee district into a climate-neutral district. One focus of the city's activities is on informing and motivating building owners and residents. The PED-urban project complements this initiative with detailed energy planning and social science support.