High Solar Fraction Heating and Cooling System Based on Liquid Desiccants

This paper details modeling and simulation results for a new solar thermal collector system that is intended to meet all of a building's major thermal loads (space heating, water heating, and space cooling). The system consists of evacuated tube collectors, a combined sensiblethermochemical energy storage tank, and two membrane devices: an air conditioner and a heat pump. These devices use liquid desiccant to cool and dehumidify in the summer and heat in the winter. We focus on the winter heat pumping. We used the simulation framework TRNSYS to show that for a high-efficiency home in Boulder, Colorado, a liquid desiccant system reduces the tank volume by more than half compared to a conventional solar thermal system. These advantages come from heat pumping to extend the range of the sensible storage and release of stored chemical energy in the heat of mixing. Preliminary cost estimates indicate sufficient promise to justify further study.