20 September 2011
This paper discusses the capacities of CO2 as a refrigerant that recovers
geothermal heat and waste heat from storage tanks. The CO2 allows heat exchange through latent heat. Thus, it increases the exchanger duty per unit length of a heat collection pipe,
which drastically reduces the heat pump installation cost and running cost. In this study, authors created pilot versions of an air conditioning system using geothermal heat and a cold
and hot water production system using waste heat from a storage tank with CO2. Authors evaluated their performance and electricity consumption. As a result, the air conditioning system showed about the same air conditioning abilities as a system with propylene glycol,
which was installed for comparison when the installed length of the heat recovery pipe was one-third to one-half, and the electricity consumption was one-half with the CO2. Meanwhile, the cold and hot water production system that used waste heat from a storage tank
recovered as much as one to nine kilowatts of heat capacity per meter of a heat collection pipe when the CO2 was used.