Abstract: A system and method are provided for storing electric energy in the form of thermal energy. A thermoelectric energy storage system includes a working fluid circuit for circulating a working fluid through a heat exchanger, and a thermal storage medium circuit for circulating a thermal storage medium. The thermal storage medium circuit includes at least one hot storage tank, an intermediate temperature storage tank, and a cold storage tank connected together via the heat exchanger. A proportion of the storage medium is redirected to or from the intermediate storage tank from or to the hot or cold storage tank, joining another proportion which flows directly between the cold and hot storage tank.

Abstract: An exemplary system and method for storing and retrieving energy in a thermoelectric energy storage system is disclosed. The thermoelectric energy storage system includes a working fluid that is circulated through a first and second heat exchanger, and a thermal storage medium that is circulated through the first heat exchanger. The second heat exchanger is in connection with a first thermal bath during a charging cycle and with a second thermal bath during a discharging cycle. In this way roundtrip efficiency is improved through minimizing the temperature difference between the first thermal bath and the hot storage tank during charging, and maximizing the temperature difference between the second thermal bath and the hot storage tank during discharging.

Abstract: A system and method for thermoelectric energy storage are disclosed. A thermoelectric energy storage system can include a heat exchanger which contains a thermal storage medium, and a working fluid circuit for circulating a working fluid through the heat exchanger for heat transfer with the thermal storage medium. The working fluid undergoes transcritical cooling during the charging and transcritical heating during the discharging cycle as it exchanges heat with the thermal storage medium. Improved roundtrip efficiency can be achieved through minimizing the maximum temperature difference (?Tmax) between the working fluid and the thermal storage medium during operating cycles.

Abstract: A system and method are provided for thermoelectric energy storage. A thermoelectric energy storage system having at least one hot storage unit is provided. In an exemplary embodiment, each hot storage unit includes a hot tank and a cold tank connected via a heat exchanger and containing a thermal storage medium. The thermoelectric energy storage system also includes a working fluid circuit for circulating working fluid through each heat exchanger for heat transfer with the thermal storage medium. Improved roundtrip efficiency is achieved by minimizing the temperature difference between the working fluid and the thermal storage medium in each heat exchanger during heat transfer. Exemplary embodiments realize this improved roundtrip efficiency through modification of thermal storage media parameters.