Abstract:

A thermoelectric energy storage (TEES) system stores electricity in thermal form and the thermal energy converts back to electricity by a Brayton cycle, Rankine cycle or other power cycles during the discharge period. Various working fluids coupled with heat and cold storage mediums have been studied extensively and the use of CO2 as the working fluid is a hot topic in TEES system. This paper first explains the principle of TEES system and examines the effects of thermal integration between the working fluid and the heat and cold storage mediums as well as the isentropic efficiency of turbomachinery on the system round trip efficiency. Applications of different working fluids are then discussed including water, air, argon, ammonia and organic chemicals, and the focus is on systems with CO2 as the working fluid, including system design, system performance study and optimizations, and system realization. Finally, the TEES system is compared with compressed air energy storage (CAES) technology. It is concluded that the TEES not only is independent on the geographical conditions and the use of fossil fuels, but also has a large storage capacity, a long life span, a low capital cost and a high round trip efficiency.

Key words: thermoelectric energy storage, carbon dioxide, Brayton cycle, Rankine cycle