Performance characteristics of a gas engine driven Stirling heat pump

This paper describes recent results in a project at KUBOTA to develop an efficient CFC-free multifunctional heat supply system. A heat pump in the system is a gas engine driven Stirling heat pump. The heat pump is mainly driven by engine shaft power and is partially assisted by thermal power from the engine exhaust heat. By proportioning two energy sources to match the heat balance of the driving engine, this heat-assisted Stirling heat pump can be supplied with the maximum share of the original energy fueling the engine and can be operated at the most efficient point. The authors have developed a system heat pump composed of 6 cylinders, the doubled E-3 prototype. This prototype uses helium gas as a working gas and is constructed as two sets of three-cylinder machines, each a combination of two Stirling sub-systems (one a power producer and one a heat pump). Design and performance simulations of the prototype are presented in conjunction with the driving engine characteristics. This heat supply system is expected to produce cooling and heating water at high COP. Developing the system will provide a CFC-free thermal utilization system technology that satisfies both wide heat demands and various fuel systems.