Capacities for Heat Pump Combined Heating and Cooling Systems with Energy Storage for Greenhouses in Japan

Abstract

Water to water heat pumps for heating and cooling with a geothermal source and two storages, (one for cool and one for warm), have been compared to dedicated systems with a single storage for either heating or cooling. Four locations have been considered for one common, relatively energy efficient greenhouse type. These systems have very similar capacity for either heating or cooling as a single storage system for either heating or cooling alone. Adding a second storage enables the same heat pump and heat exchanger system to provide similar levels of heating and cooling as separate systems would. Also a system with only two larger storages but no geothermal source can meet some of the cooling needs and most or even all of the heating need if the cooling set points are low enough. All of the systems increase the number of hours the greenhouse can be kept closed without ventilation.