2016 Feb

Electricity: Concentrated Solar Power

February 26, 2016

Solar Thermal Energy

Did you ever try concentrating sun’s rays using a lens. If you haven’t yet you should do it now. Sun’s rays can be concentrated and have enough power to burn a piece of paper. This is simple experiment to suggest that concentration of solar radiation generates large amounts of heat. This heat can be tamed to produce electricity. Solar power generation is often considered to be synonymous with photovoltaics. But there are alternate, less popular, still under-research methods that can employed to generate electricity from solar radiation. We shall discuss one such method called as concentrated solar power.

Concentrated solar power is also called as concentrated solar thermal. In a typical thermal power plant turbines are rotated by the force imparted on them with the help of pressurised steam. Concentrated solar power is used to generate the pressurised steam, in this mode of power generation, hence the name concentrated solar thermal. In a typical concentrated solar power plant, a special type of oil is heated to very high temperatures which then heats water and generates steam. Heating of oil is done by flowing oil in pipelines that are flanked on one side by a huge concave mirror. Using the same laws of reflection that we learnt in our JC Physics tuition classes, the concave mirror focuses the radiation of sun towards the centre of the imaginary sphere that can be formed using the radius of curvature of the mirror. Exactly at this point of focus, the pipeline carrying oil is placed. In the advanced systems, these concave mirrors move like the head of a sunflower directed towards the sun at any given time of the day. These concave mirrors focus the sun’s radiation onto the pipeline and heats up the oil in it.

The mirrors are placed like a farm along the length of the pipeline. The oil thus heated by mirrors moves to heat exchange chamber. Here, the heat energy from oil is transferred to water. In the process, water gets converted to steam. The steam generated has high pressure and is used to move the large turbines. Similar to the generation of electricity from wind energy where rotation of turbines by wind resulted in current and voltage difference, the rotation of turbines by steam also generates electricity. The steam is then moved to a chamber where it is cooled and condensed to water which then enters the further cycle of steam generation. Unlike photovoltaics where solar panels can be placed on the rooftop to generate electricity, this method of electricity generation is centralised and cannot be done at household level.

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