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Solar Parabolic Dishes - National Grid Power Generation and Domestic Hot Water Heating

written by: •edited by: Lamar Stonecypher•updated: 3/10/2010

Solar parabolic dishes are normally used in domestic water heating, but in the last decade have become more popular in the generation of power for the grid using renewable energy. The thermal energy is converted to kinetic energy being used to power a heat engine driving an electrical generator

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    Introduction to Solar Parabolic Dishes for Domestic and Grid Applications

    A parabolic solar dish is one of several solar energy devices which use Concentrated Solar Power (CSP) to produce renewable energy in the form of thermal energy which is normally used to heat domestic water systems. This thermal energy is now also being used to drive a Sterling heat engine, converting the thermal energy to kinetic energy and driving an electrical power generator.

    Large numbers of these power units are linked up to form a formidable sized power plant, which supplies electricity to the national grid.

    This is another article in my series on renewable energy, and is a follow-up to a previous article on Solar Parabolic Dish Operation.

    We shall recap how a solar parabolic dish works, then examine its domestic and industrial applications, having a look at how a heat engine is powered and how domestic heating systems are supplied with thermal energy.

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    Working Principles of a CSP Solar Parabolic Dish

    This type of solar energy is a form of renewable energy known as Concentrated Solar Power (CSP)

    Basically the solar parabolic dish is the shape of a paraboloid, which is mirrored on its inner surface so when solar light strikes the dish it is reflected to a central focal point. This is supported directly above centre of the dish and regardless of where the light strikes the dish, it is reflected to this central focal point.

    Positioned at the focal point is a thermal heat absorber which collects the heat from the concentrated reflected light, using this heat to run a Sterling engine to produce electricity. This thermal energy can also be used to heat domestic water systems, using a heat exchanger to transfer the solar dish output to the hot water system of the house.

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    Components of a Solar Parabolic Dish

    Depending on the physical size and the required thermal energy output, the dish can be installed in the garden, on a flat roof, or on a gable end of a building.

    The larger dishes however are quite bulky because of the solar tracking mechanism and the size and weight of the absorber and the water heating component.

    We shall therefore look at the components of a solar parabolic dish which is installed in the garden grounds.

    Support Frame

    This is usually fabricated from steel tubular sections, and incorporates the lateral and tilting solar tracking mechanism which follows the path of the sun across the sky. The support frame can be secured to a concrete pad or brick up-stands by high tensile foundation bolts, facing south.

    The Solar Parabolic Dish

    A latticed steel column supports the central focus point absorber and thermal energy component. This support is fixed the rear of the dish at its north edge, so as not to block any incoming solar light. It is bolted at the base of this column to the main tubular supports frame.

    Solar Tracking Device

    The tracking mechanisms, which can be electrically, pneumatically, or hydraulically operated, are connected to the dish support frame by adjustable arms for optimum primary settings and bolted to the main frame supports.

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    Domestic Application of a Solar Parabolic Dish

    The thermal energy produced by a solar dish can be used to produce domestic electricity or provide a means of heating a house's hot water system. We shall examine the domestic hot water supply system.

    The absorber contains a nest of coils which usually contain a mixture of water and antifreeze. This is circulated through the coils into a heat exchanger.

    Even in a small domestic sized dish thermal energy can produce temperatures of up to 150οC, sufficient to raise steam. This heat is transferred to the domestic hot water system via the heat exchanger, with the cooled condensed water being pumped back to the absorber coils.

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    Grid Application of a Solar Parabolic Dish

    The thermal energy produced by the solar dish is supplied to a Sterling Heat Engine. The absorber contains a nest of coils which usually contain a heating medium such as hydrogen gas being heated and expanding with a resultant rise in pressure. The gas is then supplied to the hot side of the Sterling engine which converts the thermal energy to kinetic energy, enabling it to drive an electrical power generator.

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    Domestic and Grid Systems

    CSP Solar DishDomestic Solar Dish System DrawingSolar Dish Grid System Layout