Photovoltaic solar panels, which generate electricity, have been rapidly spreading over Dorset rooftops in the last couple of years. Solar thermal systems seem less popular for some reason, but make perfect energy and financial sense if you have a south- or near-south-facing roof.
Solar thermal is like having a radiator on the roof that works in reverse – instead of taking heat from the hot water cylinder and distributing it into the internal space of the house, it takes heat from the sun on the roof and concentrates it into the hot water cylinder. In fact, you can make a DIY version with an old radiator painted black and placed in a sunny spot. There are some technicial issues with this, and it’s nowhere near as efficient as a modern purpose-built system, but on the other hand it is nearly free! (By the same token, you can make a solar shower with just a very long hosepipe and a shower head, but that’s a different story!)
A well-installed system should provide 60–70% of annual domestic hot water requirements. Simpler to install than photovoltaics, the installer drills the fixings through the slates or tiles into the rafters, sealing the holes afterwards. Inside the house there is a pump, temperature sensors and a controller that stops heat being removed from the cylinder when it is cold outside. You will probably also need a new hot water cylinder with an extra coil inside. It is important to calculate the size of the installation correctly – larger isn’t necessarily better, as the system may overheat if it generates more heat than can be absorbed by the water in the cylinder. For this reason, it is important to pick an experienced local installer. Once installed, your hot water is effectively free for about eight months of the year for at least 20 years into the future. You can turn your boiler off altogether over the summer months, making major savings on gas or heating oil.
The Renewable Heat Incentive currently provides a grant of £300 towards solar thermal installation costs, and a new grant is likely to be announced in the next few months that, similar to the feed-in tariff, will make payments for the heat generated, paying back the cost of installation in around 7 years.
So, with the cost of heating oil, gas and electricity steadily climbing, solar thermal makes sense on financial as well as environmental grounds, and there is plenty of time to get it installed before the sun finally returns in the spring.
For more information and the options available see our section on Solar Energy.