Simulation of Combined Solar Thermal, Heat Pump, Ice Storage and Waste Water Heat Recovery Systems. Design Criteria and Parametric Studies

摘要

Combined solar thermal and heat pump systems have attracted interest in the last decade in order to increase the share of renewable energies in space heating and domestic hot water preparation applications. Among many system concepts that combine heat pumps and solar thermal collectors, ice storage based concepts are analyzed here. Waste water heat recovery (WWHR) is an interesting option in these systems because ice storages are operated with low temperatures most of the year. Almost any waste heat that is recovered in winter can be used to regenerate the ice storage, i.e. to melt the ice. The goal of this paper is to provide design criteria for sizing these type of systems for single family houses demands and to analyze several WWHR integrations. System performance was investigated studying the effects of heat exchanger area in the ice storage, size and type of collector (covered and uncovered both with selective coating), size of ice storage and different waste water heat recovery devices. Simulations presented here show that uncovered collectors perform better than covered collectors except for large sized systems where auxiliary electrical back-up is not necessary. When the auxiliary back-up is not needed, the use of direct heat from the collectorf field to cover the heating demand is usually of benefit. Waste water heat recovery systems are found to significantly increase the system performance, especially when waste water can be stored in a tank. The system performance can increase from 4 to 20% if a waste water storage is used and around 2 % using a drainwater heat recovery system, depending on system design and building demands.