Solar PV
How does it work?
Solar PV or photovoltaic panels (photo=light, voltaic= electricity) is the name given to the method which converts the sun’s energy into electrical energy. Simply put, it is the reaction between the light energy and the silicon semi-conductors (solar cells) on the panels that causes electrons to become dislodged causing them to flow thus creating DC voltage/electricity.
PV panels consists of a number of cells which are connected (in series or parallel format depending on application) together in order to provide a sufficient DC end voltage. This can be used to either charge a number of batteries on a stand alone (off grid) system via a regulator, or wired to an inverter that converts the incoming DC voltage into AC so that it can be used within the home or building or sold back to the main grid network as part of the feed in tariff (FIT) scheme. For larger commercial organisations or businesses there is also alternative schemes such as renewable obligation certificates (ROCS) which can also be utilised.
In the UK we receive between 0.5 to 5 (winter-summer) kWh per square metre per day from the sun . The latest quality solar panels available offer an efficiency which converts around 14% of this energy into usable DC voltage electricity. A common misconception is that lots of hot sunny days are required to make the panels work; our panels will still give significant output even on cloudy days. In actual fact high temperatures (anything above 25°C typically) increase the cells electrical resistance, dropping the overall panel voltage and resultant efficiency. So hotter does not necessarily mean better.
A perfect installation would see the panels mounted facing South with month by month adjustment of their angle to track the sun as it’s height in the sky alters through the year. This is not always practical however so an inclined roof offers a good compromise. Flat roof installations will be mounted on adjustable frames to suit the application. Solar tracking devices can be additionally added to these installations to track the suns progress as mentioned above.