Concentrated Solar Power

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Concentrated Solar Power

An Analysis on Solar Thermal Power and its Application

Hassan Almutawa and Chavis Sabin

Abstract

Concentrated Solar Power (CSP) is a renewable energy source that converts the radiation from the Sun into thermal energy. CSP plants collect solar energy throughout the day and can continue to provide electricity for up to six hours after dark using thermal storage. CSP plants can only be built in arid flat areas with a high annual solar radiation rating. Many countries can benefit from CSP including oil dependent countries like Saudi Arabia and third world countries like Kenya.

Introduction

Concentrated Solar Power (CSP), also known as solar thermal power is a renewable energy source that uses the Sun’s radiation to produce electricity. There are three different types of CSP plants. One type is a parabolic trough where long curved mirrors pivot to concentrate sunlight onto tubes filled with a heat transfer fluid, generally oil and water, whose steam moves a power generating turbine [1]. The second type is a dish -engine combination. Mirrored dishes (resembling those for satellite television) track the sun and concentrate its heat onto a power-generating unit that has an engine powered by a heat-responsive fluid [1]. The third type is known as a power tower system that consists of a field of mirrors that focus sunlight onto a tower which contains a solar receiver containing heat transfer fluid, such as water or molten salt.

Design and Operation of CSP

CSPs operate by converting solar radiation to thermal energy, and then convert thermal energy to electricity. Figure 1 shows the general steps towards converting solar radiation to electricity.

Fig. 1 How power tower CSP’s convert solar energy into electricity

1. Solar radiation is reflected off of mirrors known as heliostats which are software-controlled to follow the Sun throughout the day. The angles of the heliostats are set to direct the solar radiation to a central focal point which is occupied by a thermal receiver. 2. The thermal receiver uses the solar radiation to heat up a transfer fluid, usually water, oil, or a molten salt compound. In the case of water or oil, the fluid is converted to hi pressure steam which is either stored in a pressure tank or used to turn a steam powered turbine. If the receiver uses a molten salt compound, which can trap thermal energy for long periods, the compound will be placed in a storage tank then put through a heat exchanger to transfer the heat to water to create steam. The steam is then used to turn a turbine engine. 3. The turbine converts steam to electricity which is added to the power grid. The thermal heat that is not used is stored in thermal energy storages. 4. The thermal storage stores molten salt that has been heated by the solar receiver. The storage can store thermal energy for up to six hours. The stored thermal energy can maintain electrical output during peak hours or after dark. 5. The grid takes the electricity generated by the turbine and distributes to homes and businesses.

Location and Installation of CSP

The Concentrated Solar Power (CSP) is a method of electric generation fueled primarily by the heat of the sun. This specific type of solar energy types requires a solar radiation of at least (5.5 kWh/m2/day) [2]. Therefore, effective CSP works and functions best in hotter regions, such as the Southwestern region of the U.S., Sahara Desert in Africa, and Australia. In fact, these regions today have the highest potential capacity for CSP in the world, around (740 megawatts) of the total global generating capacity. Furthermore, in addition to the solar radiation required, CSP requires arid, flat lands in order to be efficient and effective and, as well, as a part of the installation’s requirements. According to the U.S. Department of Energy (2008), an installation of a one power tower system (10 megawatts) of CSP calls for (500 acres) of smooth flat...
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