Physical Design Of A Pumped Thermal Electricity System Based On Molten Salt/cold Storage Medium

The pumped thermal electricity storage system has the advantages of high energy storage efficiency and low cost.Compared with other large energy storage technologies,such as pumped storage and compressed air energy storage,it can be installed in any geographical location and can meet the energy storage needs of any capacity.The system can be used to overcome instability of renewable energy and excessive power gap in regional peak-hollow power utilization,therefore,it has good development prospects.The traditional pumped thermal electricity storage system uses argon gas and sand as the fluid medium and energy storage medium.Under normal circumstances,the system has high working temperature and relatively low energy storage density,which greatly limits its practicability.In order to solve these problems,a new type of pumped thermal electricity storage system is proposed by using encapsuled phase change material and air as energy storage medium and working medium,respectively.The system includes six main devices:compressor,turbine,heat storage tank,cold storage tank and two heat exchangers.It has the characteristics of high cycle efficiency and high energy storage density,and also solves the harsh working conditions in the traditional pumped thermal electricity storage system.In this paper,the thermodynamic analysis and work process analysis of the system are carried out to verify whether it can achieve the above research objectives.Finally,the actual economic feasibility of the system is verified by cost analysis.In order to achieve the research goals,this paper has carried out the following research work.(?)Analysis of the packed bed in the system:investigating the common model of the bed-filled material,analyzing the heat transfer performance of the bed model by numerical simulation.The correctness of the model is verified by the experiment.(?)Analysis of other important devices in the system:The thermodynamic and working model of heat exchangers,compressors and turbines was investigated and determined.(?)In order to determine whether the new system can complete the research purpose,the paper proposes an 40MWh PTES,and carries out thermodynamics and work analysis.Further parameter analysis was carried out to study the effects of different parameters on system performance.(?)In order to verify the economic feasibility of the system,the cost analysis model of the system was investigated and determined,.The research results show that the unit energy storage density of the new system reaches 271.8kW·h/m~3;the heat storage efficiency in a single charge and discharge process is 55.1%;the heat storage efficiency in the cycle charge and discharge process is 26.9%,and the round-trip efficiency is 69.1%;Through the specific charging process analysis,the charging time is 55%longer than that of the non-phase-change material as the energy storage medium system;the unit's unit energy storage cost is 115$/kWh,which is economically feasible.In summary,the new system proposed in this paper has certain practicability in the field of energy storage.