Other Solar Technologies

Concentrating Solar Power

Concentrating solar power (CSP) is a large-scale solar thermal-electric technology that makes use of different kinds of mirror configuration to convert the sun's energy into high-temperature heat. The heat energy is then used to generate electricity in a steam-turbine-driven electricity generator.

Major types of CSP technologies

There are three major types of CSP technologies: (a) Trough System; (b) Dish/Engine System; and (c) Power Tower.

(a) Trough System

This system uses parabolic trough-shaped mirrors to focus sunlight onto a receiver tube that carries a heat transfer fluid. This fluid is heated up and is pumped through a series of heat exchangers to raise steam for a conventional steam-turbine-driven electric generator. The parabolic trough technology is a well-proven solar thermal electric technology.

(Source: Sandia National Laboratories Energy Photo Database)

(b) Dish/Engine System

The main parts of a dish/engine system are the solar concentrator and the power conversion unit. The concentrator (or the dish) collects the solar energy coming directly from the sun and focuses it on a small area. The dish structure tracks the sun continuously. The power conversion unit consists of two parts, the thermal receiver and engine/generator. The thermal receiver absorbs the concentrated beam of solar energy, converts it to heat either in the form of hot air or hot water, and transfers the heat to the engine/generator. The engine/generator system is the subsystem that takes the heat from the thermal receiver and uses it to produce electricity. The most common type of heat engine used in dish/engine systems is the Stirling engine.

(Above source: Sandia National Laboratories Energy Photo Database)

(c) Power Tower

This technology uses an array of sun-tracking mirrors (heliostats) to focus sunlight onto a central receiver mounted on top of a tower. A heat transfer fluid heated in the receiver is used to generate steam, which, in turn, is used in a conventional turbine-generator to produce electricity. Power towers developed in the 1980's utilized steam as the heat transfer fluid. The more recent power towers use molten nitrate salt as the heat transfer fluid due to its superior energy storage and heat transfer capabilities.

(Source: Sandia National Laboratories Energy Photo Database)

Small concentrating solar devices

A number of small concentrating solar devices are available in the market. Such devices have not been used nor tested for suitability for use in Hong Kong, China. Examples of some of these devices are given below only for illustration purpose. Strictly speaking, some of these devices are not CSP as we defined above, but instead are concentrating photovoltaic devices because solar cell instead of heat transfer fluid is used to receive the concentrated sunlight.

• This link will open in a new windowThis web page has hyperlinks which may transfer you to third-party website.SunFlower is a concentrating photovoltaic device currently under development and testing. The unit consists of 25 numbers of 1-foot by 1-foot mirrors attached to and moved together by an undercarriage controlled by two motors. The receiver mounted above the mirror array is approximately the size of one mirror and contains a collection of small solar cells that are wired together to produce electricity.
• This link will open in a new windowThis web page has hyperlinks which may transfer you to third-party website.Sun Oven is a simple solar cooking device.

Applicability in Hong Kong

The amount of power generated by CSP depends on the direct sunlight at the site. In Hong Kong, China, a large proportion of the solar radiation is diffuse rather than direct. The annual proportion of the direct beam component of sunlight is less than 50%, which is relatively low, suggesting that solar concentrator technology is unlikely to be effective for Hong Kong, China.