Thermodynamic Performance of a Brayton Pumped Heat Energy Storage System: Influence of Internal and External Irreversibilities

Abstract

A model for a pumped thermal energy storage system is presented. It is based on a Brayton cycle working successively as a heat pump and a heat engine. All the main irreversibility sources expected in real plants are considered: external losses arising from the heat transfer between the working fluid and the thermal reservoirs, internal losses coming from pressure decays, and losses in the turbomachinery. Temperatures considered for the numerical analysis are adequate for solid thermal reservoirs, such as a packed bed. Special emphasis is paid to the combination of parameters and variables that lead to physically acceptable configurations. Maximum values of efficiencies, including round-trip efficiency, are obtained and analyzed, and optimal design intervals are provided. Round-trip efficiencies of around 0.4, or even larger, are predicted. The analysis indicates that the physical region, where the coupled system can operate, strongly depends on the irreversibility parameters. In this way, maximum values of power output, efficiency, round-trip efficiency, and pumped heat might lay outside the physical region. In that case, the upper values are considered. The sensitivity analysis of these maxima shows that changes in the expander/turbine and the efficiencies of the compressors affect the most with respect to a selected design point. In the case of the expander, these drops are mostly due to a decrease in the area of the physical operation region.

Optimal Energy-Storage Configuration for Microgrids Based on SOH Estimation and Deep Q-Network

“…Energy storage is an important part of microgrids needed to realize multi-energy coupling, which can realize the transfer of energy across time periods. It can not only maintain the balance of energy supply and demand, smooth the output of new energy, and restrain the fluctuation of renewable energy power, but also play an important role in improving power quality, safe and reliable operation, and cost-effective coordination [4]. Compared with other storage technologies, battery energy storage has the advantages of a small footprint, no geographical restrictions, and a fast response speed.…”