Date of Graduation

8-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Civil Engineering

Advisor

William M. Hale

Committee Member

Ernest Heymsfield

Second Committee Member

Panneer Selvam

Third Committee Member

Rick Couvillion

Keywords

Applied sciences, Energy storage, High-performance concrete, Solar power plants, Thermal energy

Abstract

In recent years, due to rising energy costs as well as an increased awareness of the environmental effects of greenhouse gas emissions produced through traditional forms of energy production, there is great interest in developing alternative sources of energy. One of the most viable alternative energy sources is solar energy. In particular, concentrating solar power (CSP) technologies have been identified as an option for meeting utility needs in the U.S. Southwest. These systems are required to produce electricity not only during periods of high solar radiation but also during times of reduced radiation due to cloud cover, and even extend production to periods during the night. In order to achieve this goal, CSP plants must incorporate a thermal energy storage (TES) system from which energy can be sourced when needed. Besides the integration of a TES sub-system, another area where CSP technologies can be improved is in the development and use of heat transfer fluids (HTF) that can remain stable at temperatures up to and in excess of 1112oF (600oC).

This research explores the use of concrete as a TES storage medium for CSP technologies, specifically, parabolic trough power plants. Concrete is relatively inexpensive and the costs/ kWhthermal of energy based on the concretes used in this research could be less than $1. Researchers using concrete as a TES storage medium have achieved maximum operating temperatures of 752oF (400oC) with a 6-hour storage capacity. The operating temperature limit of 752oF (400oC) is dictated by the limitations of the concrete when exposed to elevated temperatures and by the stability of the heat transfer fluid at these temperatures. By exposing various concrete types to different heating regimens and subsequently measuring their thermo-mechanical properties, this research has identified concrete that can withstand temperatures up to 1112oF (600oC) for deployment as a TES medium. The benefits derived from using concretes that are resistant to higher temperatures are an increase in the operating efficiency of the CSP plant, an increase in the number of storage hours and a significant reduction in both the storage cost and the unit cost of solar generated electricity.

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