Natural refrigerants in heat pumps upgrading waste heat for district heating in Finland
Stanisor, Darius (2025)
Kandidaatintyö
2025
School of Energy Systems, Energiatekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2025051545254
https://urn.fi/URN:NBN:fi-fe2025051545254
Tiivistelmä
As the pressure of climate change increases, countries are looking to decarbonize their systems. Finland's energy industry is its largest polluter, and district heating (DH) its most popular residential heating solution. As DH remains largely fossil-fueled, lower environmental impact alternatives are being considered. One option is replacing DH power plants with heat pumps using industrial waste heat, but the environmental effects of the refrigerants used in the heat pump cycle also need to be considered in order to ensure sustainable operation. Natural refrigerants are the strongest contender for this position.
This study defined a cascade heat pump model and employed an iterative optimization algorithm to assess the performance of various refrigerant combinations across a range of heat source and heat sink temperatures. The heat source was an industrial waste heat stream and the heat sink was a Finnish DH supply line. The most common types of industrial streams in Finland containing waste heat that can be used for upgrading into district heat were found to come from the pulp and paper industry and food and beverage industry, with the selected temperature between 10 and 65°C. The typical Finnish district heat supply line temperature was found to range from 65 to 115°C.
The results showed that the decrease in performance when changing a synthetic refrigerant like R245fa with a natural refrigerant such as R600 is practically negligible, while achieving a significant reduction in global warming potential (GWP). Water (R718), ammonia (R717), and n-butane (R600) were the best performing natural refrigerants for the chosen system.
This study defined a cascade heat pump model and employed an iterative optimization algorithm to assess the performance of various refrigerant combinations across a range of heat source and heat sink temperatures. The heat source was an industrial waste heat stream and the heat sink was a Finnish DH supply line. The most common types of industrial streams in Finland containing waste heat that can be used for upgrading into district heat were found to come from the pulp and paper industry and food and beverage industry, with the selected temperature between 10 and 65°C. The typical Finnish district heat supply line temperature was found to range from 65 to 115°C.
The results showed that the decrease in performance when changing a synthetic refrigerant like R245fa with a natural refrigerant such as R600 is practically negligible, while achieving a significant reduction in global warming potential (GWP). Water (R718), ammonia (R717), and n-butane (R600) were the best performing natural refrigerants for the chosen system.