District energy system is facing on the risk of climate change. IPCC alarmed that the mean temperature would be rise by up to 4 °C by the end of the 21st century if there is no effort to reduce greenhouse gas emission in the fourth report. Japanese government has published weather prediction data called “Database for Policy Decision-Making for Future Climate Change” (hereafter d4PDF) to be utilized for study regarding to global warming.
This study aims to predict the effect of CGS (cogeneration system) and thermal storage after a mean temperature increase of 4°C (hereafter 4°C-Rise) with d4PDF and ENEPRO21, focused on the DHC system of Minatomirai 21 Area (hereafter MM21). In order to carry out this, this study utilized the data of the predicted heating and cooling demand of MM21 Area from the previous study: “Analysis of Influence of Climate Change on Demand and System of Heating and Cooling Predicted by d4PDF”. And the three scenarios were set up which were the Basic System Cases, the Thermal Storage Cases, and the CGS Cases.
As a result of simulation of the Basic System Cases, this study predicts what the amounts of annual primary energy consumption and CO2 emission will rise up 103.5%～103.8% and 103.7%～104.0% after 4°C-Rise. COP will increase from 0.98 to 1.01. The make-up water, the cooling water flow rate of cooling tower, and the waste heat will go up to 129.9%～132.0%, 162.3%～164.6%, and 163.5%～164.1% respectively. In average temperature, the effect of the thermal storage is that the amount of annual primary energy consumption and CO2 emission decreases by 0.6% and COP increases by 0.01. The amount of make-up water, cooling water flow rate of cooling tower, and the waste heat decrease by 6.0％, 6.2%, and 7.0% respectively. In the temperature after 4°C-Rise, the primary energy will go down 0.8～1.2% and COP will go up 0.01～0.02. The amount of make-up water, cooling water flow rate of cooling tower, and waste heat will be reduced by 5.7％～7.5%, 5.3%～7.6%, and 6.2%～8.2%. In conclusion, the effect of thermal storage in the temperature after 4°C-Rise is greater than in average temperature. As an effect of CGS, the primary energy saving rates in the temperature of average year and the temperature after 4°C-Rise are 33.48% and 32.38%, based on theoretical electro-thermal ratio. Compared with the results of ENEPRO21 simulation, in the average temperature, CGS reduces the primary energy consumption by 20.4%. And COP rise by 0.24. The amount of CO2 emission decreases by 22.3%. However, the amounts of make-up water waste heat increase by 16.4% and by 47.1%. In the temperature after 4°C-Rise, the effect of CGS is that the primary energy consumption will go down 20.8%. And COP will go up by 0.24. CO2 emission will decrease by 22.7%. The amount of make-up water will grow by 8.4%. The amount of waste heat will increase by 31.8%. To sum up, the effects of CGS in the temperature of average year and the temperature after 4°C-Rise are predicted to be on a similar level.
