Hot Thermal Energy Storage Research Articles

Experimental Study on Performance of a Solar Thermal-Driven Vapor Absorption System Integrated with Hot Thermal Energy Storage for Milk Chilling

Abstract Solar-powered vapor absorption system has proven to be a feasible and viable cooling source. However, most reported installations for milk chilling applications are equipped with an auxiliary heater that consumes significant electricity/gas, making it economically unviable. In this study, the experimental investigation of the performance of a solar-powered vapor absorption chiller has been reported for milk chilling applications as per standard ISO 5708 – 2 II. It has been identified that the performance of the vapor absorption chiller is quite uncertain and underperforming while operated with the heat directly fed through the evacuated tube compound parabolic concentrator solar field due to diurnal and seasonal variations of solar radiation intensity. Therefore, a hot thermal energy storage integration has been studied and analyzed in this study. The performance of the vapor absorption chiller has improved significantly with the use of hot thermal energy storage in the solar circuit as the coefficient of performance of the vapor absorption chiller improved up to 0.4, which was earlier around 0.25. Further, hot thermal energy storage provides better thermal management to increase the productivity and performance of the vapor absorption chiller, and the cooling time for the first milking is 2 hours and 45 minutes. The energy efficiency ratio has a maximum value of 6.1 with an average of 4.3, whereas the thermal COP has an average of 0.35 and a maximum value of 0.52 when run with thermal energy storage alone.

Effect of multi-tank thermal energy storage, recuperator effectiveness, and solar receiver conductance on the performance of a concentrated solar supercritical CO2-based power plant operating under different seasonal conditions

Renewable energy technologies based on solar energy concentration are important alternatives to supply the rising energy demand in the world and to mitigate the negative environmental impact caused by the extensive use of fossil-fuels. In this work, a thermodynamic model based on energy and exergy analyses is developed to study the transient behavior of a Concentrated Solar Power (CSP) supercritical CO2 plant operating under different seasonal conditions. The system analyzed is composed of a central receiver, hot and cold thermal energy storage units, heat exchangers, a recuperator, and three-stage compression and expansion subsystems with intercoolers between compressors and reheaters between turbines, respectively. From the exergy analysis, the recuperator, the hot thermal energy storage, and the solar receiver were identified as the main sources for exergy destruction with more than 70.0% of the total lost work in the plant. These components offer an important potential to improve the system performance via design optimization. With reference parameters, the system reaches efficiencies of about 18.3%. These efficiencies are increased with a combination of improved design parameters, reaching values of between 26.0% and 29.4%, depending on the season, which are relatively good for CSP plants.