Solar Energy Explained
Solar energy involves capturing and harnessing the sun’s energy. There are three main ways of doing this:
solar design ensures that a building's form and fabric captures the
sun's energy and reduces the need for artificial light and heating.
• Active solar water heating converts solar radiation into heat, which can be used directly or stored.
• Solar photovoltaic (PV) panels or solar cells convert daylight into electricity.
How it works
Passive solar design involves the application of design principles (such as south-facing windows) to make sure that excess heat loss is avoided and solar radiation is captured, in order to minimise the need for heating and lighting. The reverse is also true, so that minimising the capture of solar radiation, coupled with the use of natural ventilation, helps to reduce dependency on mechanical systems such as air conditioning.
Active solar water heating uses collectors, usually on the roof of a building, to capture and store the sun’s heat via water storage systems. The collectors provide heat to a fluid that circulates to a water tank. The heat is primarily used for heating water in domestic dwellings, industrial facilities and commercial buildings. This includes the growing market for solar swimming pool heaters.
The average home will spend 27% of its total energy bill on water heating and with the average household now spending between £1000 and £1500 annually on carbon fuel and electricity, a solar thermal system can save between £200 and £400 and much, much, more as prices increase - your household hot water costs could reduce by 60%.
A Solar Water System can pay back the investment in 8 years.
Solar photovoltaics (PVs) convert energy from daylight into electricity using a semiconductor material such as silicon. When light hits the semiconductor, the energy in the light is absorbed, ‘exciting’ the electrons in the semiconductor so that they break free from their atoms. This allows the electrons to flow through the semiconductor material (in a similar manner to a normal electrical circuit) producing electricity.
There are a number of PV technologies, including polycrystalline, monocrystalline and thin-film. Solar PV cells can be arranged in panels on a building’s roof or walls, and can often directly feed electricity into the building. With the latest PV technology, cells can also be integrated into the roof tiles themselves.
Groups of solar PV cells can be added together to provide increasing levels of power. This can range from small, kilowatt-sized solar panels for use in domestic households, to larger arrays, which function as separate solar power plants feeding power directly into the electricity grid.
Solar energy is only produced during the day and also varies in output
due to cloud cover. In the case of small-scale solar PV systems, batteries
or other forms of electricity storage can be used to store the electricity
for periods when the output is low but the demand is high. For solar
thermal systems, the hot water can be stored for a limited period of
time in well-insulated water tanks.
A new generation of collectors
The Compound Parabolic Concentrator (CPC) vacuum tube collectors are able to achieve the highest possible yields, taking advantage of even the weakest light beams. They are able to collect considerably more solar energy than traditional flat collectors when there are less hours of direct sunlight.
Each year we get about 4380 hours of light. Only some of this light is in the form of direct sunshine, known as beam radiation. The CPC panels are designed to work not only in direct sunshine but also in the light levels experienced on a very cloudy day, this kind of light is referred to as diffuse radiation The tube collectors capture and absorb the sun's radiation.
Heat from the tubes is then conducted to the fluid flowing through them. The hot fluid from the collector is circulated via flexible tubes by a pump through to a copper coil inside the insulated tank.
The coil conducts the heat and the resulting hot water flows from the outlet valve, and is delivered to wherever it is needed throughout the house.