Energy & Buildings
SOLAR THERMAL
Solar thermal is a big step to take towards reducing your carbon footprint. If you haven't already, it would probably make a bigger difference to ensure that your house insulation (loft and cavity wall) is maximised. This will almost certainly make significantly more energy and cost savings than by going for solar thermal (and it's cheaper).
There are two main types of system available. Each has advantages and disadvantages and adherents and detractors. You can spend lots of time researching (I did) but in the end you'll have to make a personal choice. There isn't one type that is obviously better than the other. Go to Green Business Forum to see a discussion on the various merits of each.
Direct system (Solar Twin)
This is the simplest system. Water is circulated directly from and back into your water tank. On the way it goes through the
heating panel mounted on the roof. It can be fitted directly into your existing hot water system (no new tank needed) and it
is powered by a small PV (solar photovoltaic) pump. To find out more, see
Solar Twin. NB, This diagram doesn't show a coil from another heat
source (boiler) but you will normally have one as well.
Below is the layout of a basic system that circulates a coolant/antifreeze through a preheating coil in your hot water tank. By preheating the water in the tank you then expend less fuel (oil/gas/electricity) bringing it up to the final temperature. In the summer, you could expect a system like this to provide most, if not all, of your hot water (depending on your needs and the weather). Most homes would need a new twin-coil tank but strangely, this doesn't seem to make it more expensive than the above system. It is run by an electric pump using mains electricity but you've probably already switched to a green electricity supplier if you're considering solar thermal anyway.
If you are considering this system there are two possible types of collector, flat panel and evacuated tube. There is a slight improvement in efficiency using evacuated tubes but, some think, more to go wrong and less aesthetic.
Evacuated tubes Flat panel
I had a solar thermal system fitted at the beginning of August and it's rained ever since.
Actually that isn't quite true and on the few sunny days we've had, I have monitored the digital readout and it really does make a significant difference. It also works to a lesser extent on bright but cloudy days.
One of the things I needed to resolve before I decided to make the investment (you can expect to pay between £3500 and £5000 for equipment and installation), was the payback period.
Experts may say between 7 and 12 years at current energy prices (and depending on the weather!). This may seem like a long time for a hefty investment to start paying dividends BUT why ask the question?
Do you think in terms of the payback period when buying a new washing machine? A pair of trousers? A car? Why does this question apply to solar thermal and no other purchase we are thinking of? I think the question started out as providing a reason for going ahead with an installation IT DOES HAVE A PAYBACK PERIOD. Unfortunately it's easy to start thinking of that as the only reason for installing solar thermal and thinking that it's a long time to wait to get your money back. It is unhelpful to fall into this mind set, there are more important reasons for doing it (you're standing on one of them and you may have several others running around making a lot of noise and mess!).
