Gas cogeneration systems use city gas as fuel to power engines, turbines and fuel cells to generate electricity, and heat which is utilized to produce steam and hot water. Gas cogeneration systems are used for a variety of purposes, including production process in factories, supplying hot water and steam in hotels and hospitals, heating and air conditioning of buildings, and heated swimming pools.
　Gas cogeneration systems achieve high total energy efficiency of 70% to 90%, and excel in energy and cost saving performance. After the Great East Japan Earthquake,
distributed generation, including gas cogeneration, was required to assume additional social roles as “energy security facilities” and as “a supply of electricity for the utilities’ electricity supply system.” From now on, it is necessary to build a disaster-resistant energy system, and it is important to identify how to mix gas cogeneration systems and renewable energies, such as photovoltaic energy, with the existing large-scale, centralized power generation system.