Thermoelectric energy storage system having an internal heat exchanger and method for storing thermoelectric energy

Abstract

Exemplary embodiments are directed to a thermoelectric energy storage system (TEES) and method for converting electrical energy into thermal energy to be stored and converted back to electrical energy with an improved round-trip efficiency are disclosed. The TEES includes a working fluid circuit for circulating a working fluid through a first heat exchanger and a second 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 coupled to a cold storage tank via the first heat exchanger. The arrangement maximizes the work performed by the cycle during charging and discharging for a given maximum pressure and maximum temperature of the working fluid.

Description

RELATED APPLICATION(S)[0001]This application claims priority as a continuation application under 35 U.S.C. §120 to PCT / EP2010 / 065217, which was filed as an International Application on Oct. 11, 2010 designating the U.S., and which claims priority to European Application 09172831.1 filed in Europe on Oct. 13, 2009. The entire contents of these applications are hereby incorporated by reference in their entireties.FIELD[0002]The present disclosure relates generally to thermoelectric energy, such as, the storage of electric energy and particularly to a system and method for storing electric energy in the form of thermal energy in thermal energy storage.BACKGROUND INFORMATION[0003]Base load generators such as nuclear power plants and generators with stochastic, intermittent energy sources such as wind turbines and solar panels, generate excess electrical power during times of low power demand. Large-scale electrical energy storage systems are a means of diverting this excess energy to ti...

AI Technical Summary

Benefits of technology

[0030]In the thermal storage medium is a liquid, such as water, for example, and the working fluid of the exemplary embodiments described herein can include, for example, carbon dioxide.

[0038]In yet another exemplary embodiment, at least one section of a charging cycle or a discharging cycle is performed transcritically.

[0032]In an exemplary embodiment disclosed herein, during the discharging cycle, the second heat exchanger includes; a first input from a pump connected to a first output leading to the first heat exchanger, and a second input from a thermodynamic machine connected to a second output leading to a condenser.

[0040]Advantageously, exemplary embodiments of the present disclosure minimize the amount of heat energy specified for the adjustment of storage medium temperatures for charging and discharging, thereby minimizing the size of the thermal storage specified.

[0041]Exemplary embodiments disclosed herein maximize the work performed by the cycle during charging and discharging for a given maximum pressure and maximum temperature of the working fluid at point IV, FIG. 4 in the cycle. Advantageously, this maximizes the round-trip efficiency of the system.

[0042]Further advantages of the exemplary embodiments can be obtained through the high power density of the system.

Problems solved by technology

It is important to point out that known electric energy storage technologies inherently have a limited round-trip efficiency.

The rest of the electrical energy is lost.

The roundtrip efficiency of the TEES system is limited for various reasons due to the second law of thermodynamics.

Secondly, the conversion of heat to mechanical work in a heat engine is limited by the Carnot efficiency.

This fact inevitably degrades the temperature level and thus the capability of the heat to do work.

However, all these applications are distinct from TEES systems because they are not concerned with heat for the exclusive purpose of storing electricity.

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