Thermoelectric energy storage system with an intermediate storage tank and method for storing thermoelectric energy

An energy storage system having a charging cycle for providing thermal energy to a thermal storage, and a discharging cycle for generating electricity by retrieving the thermal energy from the thermal storage, the energy storage system comprising:

• a heat exchanger;
• a working fluid circuit for circulating a working fluid through said heat exchanger;
• a thermal storage medium circuit for circulating a thermal storage medium, the thermal storage medium circuit having at least one hot storage tank, one intermediate temperature storage tank and one cold storage tank connected together via the heat exchanger;
• means for joining or dividing a stream of thermal storage medium;
• and
• wherein the heat exchanger is divided into a first section and a second section and the thermal storage medium flows through both the first section and the second section, and wherein the means for joining or dividing a stream of thermal storage medium comprise a stream splitter located between the first section and second section of the heat exchanger.

An energy storage system having a charging cycle for providing thermal energy to a thermal storage, and a discharging cycle for generating electricity by retrieving the thermal energy from the thermal storage, the energy storage system comprising:

• a heat exchanger;
• a working fluid circuit for circulating a working fluid through said heat exchanger;
• a thermal storage medium circuit for circulating a thermal storage medium, the thermal storage medium circuit having at least one hot storage tank, one intermediate temperature storage tank and one cold storage tank connected together via the heat exchanger;
• means for joining or dividing a stream of thermal storage medium;
• and
• wherein the energy storage system converts electricity into heat and stores said heat in the charging cycle.

A method for storing and retrieving energy in an energy storage system, comprising:

• charging the system by heating a thermal storage medium, wherein the charging comprises:
• the thermal storage medium circulates between a hot storage tank, an intermediate storage tank and a cold storage tank connected together via a heat exchanger, wherein
• some proportion of thermal storage medium from the cold storage tank is split off and directed to the intermediate storage tank after passing through some part of the heat exchanger, or
• a portion of thermal storage medium from the intermediate storage tank is combined with thermal storage medium from the cold storage tank before passing through some other part of the heat exchanger;
• and
• discharging the system by heating a working fluid in a working fluid circuit with heat from the thermal storage medium, and expanding the working fluid through a thermodynamic machine.

A method for storing and retrieving energy in an energy storage system, comprising:

• charging the system in a charging cycle, wherein the charging comprises:
• the thermal storage medium circulates between a hot storage tank, an intermediate storage tank and a cold storage tank connected together via a heat exchanger, wherein
• all the thermal storage medium from the cold storage tank is routed to the intermediate storage tank after a first heat exchanger section of the heat exchanger, and then a portion of the thermal storage medium is piped out of the intermediate storage tank and fed into a second heat exchanger section of the heat exchanger and subsequently to the hot storage tank;
• and
• discharging the system by heating a working fluid in a working fluid circuit with heat from the thermal storage medium, and expanding the working fluid through a thermodynamic machine.