In this study, we first analyzed the effect of heat interchange between multiple plants in a real-world district heating and cooling (DHC) system and confirmed the improvement in energy efficiency. The two target plants (East Plant and West Plant) were large, with a total floor area of approximately 150,000 m², and had thermal storage tanks that enabled rated operation of the heat source equipment (centrifugal chillers with variable frequency drives and heat recovery chillers). It was confirmed that the overall efficiency could be improved by increasing the operation of the heat recovery chillers and avoiding ultra-low load operation through heat interchange. Next, we used simulation to study the conditions for effective heat interchange between plants in the DHC system. It was confirmed that when there is a difference in the efficiency of heat source equipment between plants, such as when the year of completion of construction is significantly different, efficiency can be improved by transferring heat from a plant with high efficiency to one with low efficiency. It was also confirmed that if the building usages (load patterns) are different, higher efficiency operation is possible by appropriately consolidating the load to one of the plants. It was also confirmed that the use of heat interchange can increase the operating ratio of more efficient heat source equipment in systems with thermal storage tanks, thereby improving the COP of the entire plant. As the increase in transfer power of pumps due to heat interchange was only 0.1%, it is considered that using high-efficiency heat source equipment was beneficial. The heat interchange between plants in the DHC system can also contribute to improving the supply reliability because it expands the range of possible responses to load fluctuations caused by heat source equipment malfunctions and changes in customer usage.

At high humidity, odor diffuses from wastewater storage tanks installed outdoors. Deodorization performance could be decreased for water vapor adsorbed to the activated carbon. This study attempted to reduce the amount of water vapor adsorption to the activated carbon by using an electric heater. Hydrogen sulfide, the main odorous substance emitted from wastewater storage tanks installed outdoors at a business site in the Kanto region, was treated by activated carbon with electric heater. When the temperature rise was set to 5° C, the concentration of hydrogen sulfide after passing through activated carbon was 0.7 ppm or less while it exceeded 10 ppm before passing through the activated carbon. This confirms that the required deodorizing performance was obtained.