Liquid metal thermal storage system

Abstract

Embodiments of this invention relate generally to high temperature thermal energy storage, and more specifically, to the use of the latent heat of fusion of melting and solidifying metals to receive from and provide heat to a gaseous medium. Embodiments of this invention are also known as the Liquid Metal Thermal Storage system or LIMETS. Also described are methods of containing the storage material, heat transfer means, and choices of metals and alloys for thermal storage materials.

Description

CLAIM OF PRIORITY[0001]This application claims benefit of U.S. Provisional Application No. 61 / 276,269, filed Sep. 10, 2009, which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]The use of solar thermal power for generating electricity on a utility scale is having a resurgence of interest in light of global warming issues caused largely by the release of carbon dioxide, methane, and absorbing particulates in the atmosphere and to the increasing of fossil fuels. The use of concentrated solar energy to heat a working fluid to a high temperature to operate Rankin, Brayton, and Sterling cycle engines to provide mechanical power to operate a generator for utility scale electric power production offers an attractive alternative to the use of fossil fuels. However, utilities are generally requesting that power production facilities provide dispachable power on the order of 75% of the year. Since the sun is only above the horizon 50% of the time on a yea...

AI Technical Summary

Benefits of technology

[0018]There are several advantages to this form of latent heat storage. First, most of the heat is released at a constant temperature which allows a gas turbine to operate at its design point. This is a consideration as off-design operation of gas turbines can significantly lower their conversion efficiency. Charging the thermal storage is accomplished by the gas at any reasonable temperature above the melting point of the metal. Because all suitable metals and alloys contract on melting there is no reason for metals to break their containing tubes or storage containers. The high thermal conductivity of the metal in both liquid and solid form provides excellent heat transfer within the metal. This avoids problems encountered in using liquid salts or alkali metals wherein low conductivity regions of the solid and solidifying material slow the release of heat.

Problems solved by technology

In latent heat storage systems using high temperature salts, there are restrictions in the heat flow into and out of the storage material due to the low conductivity of salt.

Thus the combination of the low conductivity of the salt and the curtailment of convection due to the immobility of the salt presents obstacles to the utilization of this type of latent heat storage system.

Oils break down at temperatures above about 400° C. Most thermal storage systems using salt operate below about 570° C. No effective means have been found to store steam at the pressures and temperatures required to run efficient Rankin cycle engines.

Storing high temperature gas is not a realistic energy storage option.

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