Investigation On A Solar Heating System With Seasonal Energy Storage For Greenhouse

A solar heating system with underground seasonal energy storage forgreenhouse applications was proposed, which charged solar thermalenergy into borehole region in summer and extracted in winter forgreenhouse space heating. Both experimental analyses and optimizationwere performed based on a demonstration project.First, the experimental setup of the seasonal energy storage systemwas built and performances were tested on different conditions. Theexperimental result showed that the temperature in greenhouse can be1.3oC~3.1oC lower than ambient temperature in a summer day, whoseaverage temperature was31.1oC. By the use of seasonal energy storagesystem, the temperature in greenhouse can be7.9~9.9oC higher thanambient in a cloudy winter day, whose average temperature was5.3oC.And in a sunny winter day, greenhouse can be9.6~12.6oC higher thanambient.Secondly, a TRNSYS model of the solar heating system withunderground seasonal energy storage was built. After adding an newcomponent which is programmed by FORTRAN, the model could change operation mode among tank storage mode, tank heating mode andboreholes heating mode.What is more, simulation and optimization were carried out. Afteranalyzing the load of greenhouse, it was founded that cooling load can bereduce32%by the use of exterior gladding and heating load can bereduce37%by the use of wet curtain. When the optimization ofparameters was finished, the solar fraction of the solar heating systemwith underground seasonal energy storage can reached73.1%, which was19.3%percentages higher than the old system. And based on theoptimized parameters, the storage tank could afford632.7GJ thermalenergy and a part of244.9GJ was delivered to greenhouse directly byheating pipes. The remaining387.8GJ energy was charged into boreholesand storage in soil and103.4GJ was extracted in winter for greenhousespace heating.