Evaluation of Energy Use in District Heating and Cooling Plant Using Sewage and One Using Air as Heat Source

Abstract

The efficiency of energy usage of a district heating and cooling plant using sewage water as heat source and sink, was evaluated by investigating the data of the district heat demand and energy supply to the plant, which were collected at the Koraku -1 Chome plant in Tokyo central region.
Through analyzing these data, it was clarified that the overall COPs of the plant were 3.17 for cooling and 2.65 for heating.
COP was then compared with that of another plant using air as heat source and sink. The overall COPs of this plant which were calculated according to the atmospheric temperature, were 2.54 for cooling in summer and 2.28 for heating in winter.
The differences in COPs were due to the temperature differences between sewage water and air.
As a result for COP differences, the district heating and cooling plant using sewage water could be more energy saving, up to 20% for cooling in summer and 14% for heating in winter, compared with the counterpart plant that uses air as heat source and sink.