Numerical investigations of long-term thermal performance of a large water pit heat storage

• Annual thermal performance of PTES in Dronninglund, Denmark monitored and analyzed. Trnsys model the developed validated against measurement 2015. The annual charged discharged energy were predicted with a deviation < ±4%. Ratio heat loss from cover, sides bottom respectively 60%, 38%, 2%. Influence soil types diffuser positions on investigated. Water pit storage is an effective long-term storage. Experimental theoretical investigations 60,000 m 3 water was carried out aim to study its performance. Experimentally, detailed measurements analyzed monitor behavior store, including flow rates, temperatures inlet outlet flow, stratification store surrounding at four different depths. Theoretically, simulation based Type 343 (ICEPIT) TRNSYS. calculated compared measurements. used investigate influence properties arrangement store. result show that predicts well Over whole year, average temperature differed within ±4.7 K measured values. are 12,787 MWh 11,957 respectively. between experiment did not exceed efficiency reached 90% second year operation. ground consistent ones Measured 1392 MWh. As elucidated by model, cover contributed 60% loss, while sidewall 38% 2% significant. For surrounded dry soil, can reach 90%, for wet sandy gravel, decreases 7%. Change height middle inlet/outlet could slightly improve 1%. restrains focus areas further pointed out. findings paper give good reference researchers, designers consultants planning solar heating plant large