System modeling and building energy simulations of gas engine driven heat pump

Abstract

To improve the system performance of a gas engine driven heat pump system, an analytical modeling and experimental study has been made by using a desiccant system in cooling operation (particularly in high-humidity operations) and suction line waste heat recovery to augment heating capacity and efficiency. The overall performance of a gas engine driven heat pump system has been simulated with a detailed vapor compression heat pump system design model. The modeling includes (1) a gas engine driven heat pump cycle without any performance improvements (suction liquid heat exchange and heat recovery) as a baseline (both in cooling and heating mode), (2) a gas engine driven heat pump cycle in cooling mode with a desiccant system regenerated by waste heat from the engine incorporated, and (3) a gas engine driven heat pump cycle in heating mode with heat recovery (recovered heat from engine). According to the system modeling results, by using the desiccant system, the sensible heat ratio can be lowered to 40%. The waste heat of the gas engine can boost the space heating efficiency by 25% at rated operating conditions. In addtion, using EnergyPlus, building energy simulations have been conducted to assess annual energy consumptions of the gas engine driven heat pump in 16 U.S. cities, and the performances are compared to a baseline unit that has a electrically driven air conditioner with the seasonal coefficient of performance of 4.1 for space cooling and a gas furnace with 90% fuel efficiency for space heating.