Thermoelectric Energy Storage Using Auxiliary Solar Thermal and Geothermal Energy

Abstract

Multi-megawatt thermoelectric energy storage (TEES) based on thermodynamic cycles is a promising alternative to pumped-storage hydroelectricity (PSH) and compressed air energy storage (CAES) systems. The size and cost of energy storage are the main advantages of this technology as it generally uses inexpensive energy storage materials and does not require high-pressure tanks or rare geographic terrain, but the round trip electric efficiency of this technology remains low compared to its competitors. In this context, the objective of this article is to study and simulate a TEES system. A TEES system converts electrical energy to thermal energy by means of an electric heater uses joule heating effect, the system storage this thermal energy in solar salt. Stored thermal energy is converted into electrical energy by a thermal engine uses the organic Rankine cycle (ORC). An auxiliary energy source is integrated with the organic Rankine cycle to improve the round trip electric efficiency of the system. Auxiliary energy source can be solar thermal and geothermal at an average temperature between 100 and 140 °C, which is used to evaporate the working fluid to saturation. The steam is then superheated by stored thermal energy. The superheated steam expands in a turbine producing a good amount of energy compared to the saturated steam expansion. Methanol (CH3OH) has been used as a working fluid because its boiling point is less than 100 °C at the atmospheric pressure.