The parabolic solar thermal concentrator

This is another option for sun-drenched locations which focuses the radiation to produce intense heat - up to 800°C. A version in the United States links this to a unique helium-based Stirling engine. The concentrator mirrors produce about 30 kW of reflective power to the heat pipe receiver which is linked to the engine. The engine operates on the basis that the heat vaporises liquid sodium in its receiver at the focal point of the dish. Condensation of the sodium on the heater tubes raises the temperature of an internal helium circuit. The expanding helium drives pistons which in turn drive an alternator to produce electricity (Figure 4.2).

An alternative solar concentrator built by the Australian National University uses a computer to enable it to track the sun with extreme accuracy. This system produces superheated steam in a solar boiler at the focal point. The steam is piped to a four cylinder expansion engine that drives a 65 kVA generator.

One spin-off from this technology is a demonstration scheme which has attached 18 solar thermal power dishes to an existing coal fired steam turbine power station producing the equivalent of 2.6 MW for the grid which saves some 4500 tonnes/year of CO2. The development

Concentrator Solar Parabolic

potential is to use the waste heat from the system for co-generation. In hot dry climates an ideal application for this system is in desalination.

A variation of this principle is the SunDish Tower System of STM Power in the USA, which uses a unique type of Stirling engine with integral electricity generation within the sealed chamber (see p. 91).

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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