What is Concentrated Solar Power?
Concentrated solar power uses mirrors to focus sunlight in order to collect heat, create steam and generate electricity. A renewable alternative to power stations that burn fossil fuel for the same process, concentrated solar collector fields are becoming more common around the world.
In many cases, the heat generated by concentrated solar power can also be stored using a thermal energy storage system. This means electricity generation and supply can continue when sunlight is not available and can still be provided to customers at peak times.
There are 4 main types of solar concentrator and each works in a slightly different way:
Power Tower Concentrators
Power tower concentrators, also known as central receivers, use flat mirrors to focus sunlight onto a central tower receiver. This in turn heats a liquid, usually molten salt, which creates steam for use in electricity generation. The mirrors surround the central receiver in a circular shape and are controlled by computer to move on two axes ensuring that they collect and focus the sunlight effectively.
This type of system uses a mirrored dish which is often made up of smaller mirrors and formed into a satellite-dish shape that concentrates sunlight onto a receiver. Unlike the other types of solar concentrators, dish systems don't work by heating water for steam. Instead the receiver is integrated with a combustion engine that has tubes of hydrogen or helium gas. These gases are heated to high temperatures, causing them to expand inside of cylinders, powering pistons which turn an electricity generator.
Curved, u-shaped mirrors are used in parabolic trough systems. They have an oil filled receiver tube running along the centre and as this absorbs the concentrated energy, it reaches an extremely high temperature. This oil is then used to heat water, creating steam which drives a turbine power system and generates electricity. The mirror troughs track the suns movement from East to West, collecting an optimum amount of sunlight throughout the day.
Linear Fresnel Concentrators
Linear solar concentrators work in a similar way to parabolic troughs, except they use a series of flat mirrors in long parallel rows instead of curved mirrors. These mirrors focus sunlight onto tubes of fluid that reach high temperatures, producing steam for use in electricity generation.
This video by the U.S Department of Energy has more useful information about solar concentrators and how they operate.