Optimal integration of solar collectors to Carnot battery system with regenerators

It is very important to improve energy conversion efficiency in energy utilization. In practical application, the power supply and consumption cannot be perfectly matched, some extra power remains in the power grid. In this paper, models of Basic Carnot battery and Carnot battery with regenerators are constructed, which realize the peak load shifting of the power grid, and the utilization of low-temperature heat and solar energy. The thermodynamic and economic performances of the Basic Carnot battery and Carnot battery with regenerators are obtained, and the multi-objective optimization is carried out by TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution). Furthermore, the optimal solutions of the Basic Carnot battery and the Carnot battery with regenerators are compared. The results indicate that there are optimal cold reservoir and hot reservoir temperatures for both the Basic Carnot battery and the Carnot battery with regenerators, which maximize the round-trip efficiency and minimize the levelized cost of storage (LCOS). As the area of the trough solar collector increases, the round-trip efficiency of the system increases gradually. At the lowest LCOS target, the area of the trough solar collector has little effect on the LCOS. When the same working fluid combination is used in considered two systems, the round-trip efficiency of the Carnot battery with regenerators is higher. When the working fluid combination of R245fa-R1234ze is used in the two systems, the LCOS of the Basic Carnot battery is lower than that of the Carnot battery with regenerators. For the other two working fluid combinations, the corresponding LCOS size relationship is the opposite. By comparing six optimal solutions of the Basic Carnot battery and the Carnot battery with regenerators with three working fluid combinations, it’s found that the optimal design is the Carnot battery with regenerators using a working fluid combination of R245fa-R601. The LCOS and the round-trip efficiency of the system under optimal design are 0.168 $/kWh and 454.14%, respectively.