Heat recovery from local resources is shown to be a promising solution to reduce the carbon footprint of district heating. Supermarkets equipped with a CO2 refrigeration system and a geothermal storage offer a larger heating capacity, compared to traditional solutions. While district heat could benefit from this higher heat recovery availability, supermarkets could generate an income from a capacity that would be otherwise unused. For the first time, this study applies a detailed modelling approach considering both sides of such a synergy. The objective is to assess the techno-economic and environmental impact of a coordinated control strategy. Since the heat recovery from the supermarket consumes additional electricity, power-to-heat is implemented as a solution to reduce the overall CO2 emissions. This is demonstrated by scenarios simulated for a district in Stockholm. Hourly electricity CO2 intensity and prices are implemented as signals to prioritize either the district heating central supply or heat recovery. By boosting the use of electricity when cleaner, a CO2 intensity-driven control show the potential of reducing the carbon footprint of the district (−9.4%). A control based on prices, instead, is more convenient economically both for the district (−1.4% heat cost) and for the supermarket (−32% operational cost).

Decarbonizing the district heating sector is a key measure to achieve the 2040 net-zero emissions target for Stockholm City. One significant question to answer is to find out the locations of all the clean non-fossil fuel heat sources that could be used for district heating within the city?s administrative boundary, and to evaluate how much heat could be extracted from these heat sources. This paper maps out both the geolocations and the technical potentials of the clean non-fossil fuel heat sources for densely populated Stockholm City region, using Geographical Information System based integrative-analysis method. The mapping achieves 1-meter highresolution and provides integrated open datasets to overcome the data availability issue. The mapping results show that a great number of clean and non-fossil fuel heat sources are available for district heating in Stockholm City. By fully unlocking the potentials of these heat sources, around 7054 GWh heat energy is estimated to be possibly exploited per year, which could cover 100% of the existing district heating energy requirement in Stockholm City. The potential share of each mapped heat source is: water bodies 48.3%, data centers 45.4%, supermarkets 4.5%, underground subway stations 0.8%, sewage plants 0.5%, shallow geothermal 0.3% and ice rinks 0.2%. A total of 9 heat sources clusters are identified, which could be prioritized for clean heating energy exploitation. By using the high-resolution mapping, the district heating utilities could plan the capacity in a forward looking way according to the local heat source availability. The method pipeline developed in this study could be recommended to other cities with district heating needs and assist their clean district heating transition roadmap design.

The planning of energy infrastructures in new districts often follows the practice adopted for the rest of the city. In Stockholm, district heating is a common solution for multi-apartment neighborhoods. Recently, because of an average clean electricity mix, heat pumps have gained interest. However, European studies suggest to limit the reliance on electrification to avoid an extreme demand increase. Thus, an effort is required to improve the environmental impact of alternative options. This study proposes waste heat recovery in low temperature networks as a promising solution. By means of a techno-economic and environmental analysis, this option is compared to domestic heat pumps. A new approach is proposed to combine a district level perspective with simulation tools able to capture sector-coupling interactions. Scenarios, for a real neighborhood, assess waste heat recovery potential and electricity grid loading status. Results show that a waste heat recovery capacity equal to 10% of the peak load can reduce fossil fuel use of 40%. Local grid limitations are shown to be a bottleneck for the feasibility of domestic heat pumps. Their heat generation cost is 28% higher than for district heating. The carbon footprint is strongly dependent on the emission factor of the electricity mix (+11%/-24%).