Development of Residential Gas Engine CHP System 'COREMO' Optimized for Cold Regions and Its Evaluation on Environmental Performance

摘要

Recently, residential CHP systems using gas engines or fuel cells have been introduced into the market for the purpose of energy conservation in Japan. Meanwhile, in Hokkaido, as a cold region, energy consumption in the household sector is about 1.5 times compared with the national average. Under such circumstances, AISIN SEIKI Co., Ltd. and Hokkaido Gas Co., Ltd. developed a residential gas engine CHP system "COREMO" optimized for cold regions and the system has been on sale since 2011. COREMO has three good points compared with conventional residential gas engine CHP systems. Firstly, it needs small indoor space for installation. Secondly, the operation method of the system is load following, while conventional system converts surplus electricity into heat. Thirdly, a high efficiency condensing boiler is used as backup. The exhaust heat of COREMO is used only for heating, while exhaust heat of general system is used for hot-water supply. The engine operates only when heating is required and electricity demand is over a certain value, so a hot-water tank for heat reserving which requires a large indoor space is unnecessary. The operation method of the engine is load following in order to keep high efficiency. When engine's power generation is insufficient, commercial power is used. Hotwater supply and heating that cannot be covered by engine's exhaust heat are supplied by a condensing boiler which has small-scale and high efficiency. In the case of common residence in Sapporo which is the largest city in Hokkaido, COREMO reduces 40% of purchased electricity and 1 ton of CO2 annually, and effects by introduction of the system are better than conventional type as previously reported in IGRC 2011. Heat generation efficiency at rated operation reaches 64.0%LHV increasing of 5.0 points from the previous system. The dimension of the system is W700 x D400 x H1,018 and it achieves 22% volume downsizing. Two useful functions have been added to the 2013 model COREMO. One is the power supply during blackout. If a blackout occurs when COREMO is operating, it keeps generating and supplies 750W of electricity to the condensing boiler and the emergency plug. The other is that the exhaust heat is used to reheat the bath, so it operates even in summer. These improvements reduce another 70 kg-CO_2 emissions. 19 units of COREMO have been installed to residences at a town block, which is named "Eco Town North 48", in Sapporo, and we conducted measurements in order to confirm effects by introduction of the system. The exhaust heat from COREMO is used not only for panel heater and floor heating but also preheating for ventilation. COREMO cuts 73% of purchased electricity of the town block at the peak of electricity demand. Compared with the conventional system (commercial power + non-condensing boiler), the amount of CO2 reduction reached an average of about 1.1 tons/year, and energy costs, which includes electricity and gas, were decreased by 60,400 yen (US$628 on Dec. 6th, 2013) annually.