Thermoelectric energy storage system and method for storing thermoelectric energy

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.

Description

RELATED APPLICATIONS[0001]This application claims priority as a continuation application under 35 U.S.C. §120 to PCT / EP2009 / 058475, which was filed as an International Application on Jul. 6, 2009, designating the U.S., and which claims priority to European Application 08160520.6 filed in Europe on Jul. 16, 2008. The entire contents of these applications are hereby incorporated by reference in their entireties.FIELD[0002]The present disclosure relates generally to the storage of electric energy. More particularly, the present disclosure relates to a system and method for storing electric energy in the form of thermal energy in a 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...

AI Technical Summary

Benefits of technology

[0011]An exemplary embodiment provides a thermoelectric energy storage system for providing thermal energy to a thermodynamic machine for generating electricity. The exemplary system includes a heat exchanger, and a hot storage unit which is connected to the heat exchanger and which contains a thermal storage medium. The exemplary system also includes a working fluid circuit configured to circulate a working fluid through the heat exchanger for heat transfer with the thermal storage medium contained in the hot storage unit. The working fluid circuit is also configured to minimize a temperature difference between the working fluid and the thermal storage medium in the hot storage unit during heat transfer.

Problems solved by technology

All electric energy storage technologies inherently have a limited round-trip efficiency.

The rest of the electrical energy is lost.

The efficiency of thermoelectric energy storage is limited for various reasons rooted in the second law of thermodynamics.

Firstly, the conversion of heat to mechanical work is limited to the Carnot efficiency.

Secondly, the coefficient of performance of any heat pump declines with increased temperature difference between the input level and the output level.

Thirdly, any heat flow from a working fluid to a thermal storage and vice versa requires a temperature difference in order to happen.

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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