Solar Photovoltaic (panels). These have really become very popular all over the place and many farmers are covering their barns with these and one sees fields of them in places.
These are panels of silicon semiconductor solar cells which generate electricity when light falls on them. There are various technologies but the principle is the same. The “array” of panels are arranged in “strings” – several panels connected in series – and produce direct current (DC). This is not what we need in a house or to feed back into the mains supply, so the output from the string(s) is taken to a clever box called an inverter. This turns the variable DC output from the panels into alternating current (AC) at the mains voltage. If you are not using all the output yourself, the voltage rises a little and current flows back into the mains – out of the house rather than into the house. There’s a meter to measure all the power produced by the system (whether you use it or not) and it’s on this that the payment under the Feed-in-Tariff (FiT) is made.
There was a lot of encouragement from the government to install this – they provide a payback for the capital cost of the installation. Over the last not so very many years, the cost of the panels has fallen considerably – they’re being made in their millions – and the
FiT has also fallen – it was around 36p per kWh then it fell to 21p, then to 14p and now I understand it’s about 12p. Looked at as a financial product I see it as an annuity. You put up your money and you get an indexed-linked (and slightly weather-related!) return for the next 20 years. See elsewhere in this blog for how the system here has performed.
This probably not the place to argue about the rights and wrongs of this renewable technology. Suffice it to say that the panels only produce power when it’s sunny. So I’m using the mains supply as a battery – I draw power from the mains when I need it and put power into the electricity grid when I don’t. When I do need power there has to be a power station running to supply it. So at night, for example, the electricity grid either needs to have substantial power storage (something they have but need to have very much more of) or the grid still needs to have just as many power stations as there always were – they just get used less in sunny weather. The point here is that there are now two sets of equipment keeping us all in electricity.