NT-87-03-5 -- Natural Gas I.C. Engine-Driven Heat Pumps

The natural gas heat pump concept offers significant advantages in efficiency over any other natural gas heating/cooling system. Compared to current high efficiency condensing furnaces, gas heat pumps offer practical savings on the order of 50%. The most mature concept available to achieve this high efficiency is the natural gas I.C. engine heat pump system. Several hundred of these systems are operating in western Europe. Only one is known to have operated in the U.S. for several years, and it is the focus of this paper.

An I.C. engine water-to-water heat pump package designed for heating only was obtained from West Germany in 1980. It was modified, instrumented, and integrated into a residential central air heating/cooling system to provide total space conditioning for a 3200 ft² (320²) residence in Atlanta, GA. The system has been supplying 100% of the space heating and cooling since June 1981 and domestic hot water starting in January 1982.

The seasonal heating and cooling outputs and gas consumption have been monitored. The resulting seasonal heating and cooling coefficients of performance were 1.47 and 0.57 respectively. These demonstrated field efficiencies are approximately double those of conventional gas furnaces and approximately 50% higher than those of conventional absorption air conditioning.

This paper presents details of (1) the heat pump components, (2) system design, (3) controls, (4) instrumentation, (5) seasonal performance, (6) transient performance, (7) noise levels, and (8) maintenance and reliability.

Units: I-P