Numerical Investigation of a Large-Scale Water Pit Heat Storage
Abstract
Large scale water pit heat storage (PTES) is a key component to increase the efficiency of solar thermal utilization. Based on the 1535-1301 model, this paper presents a two-dimensional simulation of the annual thermal performance of PTES using TRNSYS. This model encrypts the soil grid according to the water pit layers to improve the accuracy of heat loss calculation. The accuracy of the model is verified by comparing it with measured data from a solar plant in Dronninglund, Denmark. The results show that the average difference between the model and the measured data is approximately 2.5%. In addition, the temperature prediction error and numerical diffusion of each layer become smaller as the number of stratification increases. The stratification coefficient averages about 200 for summer charging and decrease to 100 for winter discharging, indicating that stratification is more pronounced in summer and mixing is higher in winter. The actual charging and discharging energies are 11,868 MWh and 11,250 MWh per year, respectively, with a total heat loss of 1,157 MWh. This PTES numerical model can be used for solar thermal system simulation to increase the calculation accuracy.