16th December 2011
This has been the year when solar energy, particularly photovoltaic panels, hit the roof. Well, not for us actually – we have been driving passive solar energy up the wall. The feeding frenzy in the UK is now drawing to a close and, as you can see from the picture below, take up has risen radically in the last few weeks. Three households on this small estate have installed solar panels – approximately 16 m² on each roof.
It will be interesting to see what happens now that subsidies have been cut. Obviously installing photovoltaics is no longer the investment opportunity it was. Spending £12,000 on solar panels provided a good rate of return (10%) compared to other government-backed investments such as premium bonds (around 1%).
Initially the cost of having solar panels put on the roof will fall as installers enter into a vicious price war – which many, no doubt, will not survive. There is also some talk of a slowdown in the Chinese economy, which could see photovoltaic panels dumped onto the world market at bargain basement prices. Even at their current prices solar panels made in China are causing problems for US and German manufacturers.
So now we will see how many people install solar panels because they are an effective way of reducing electricity bills and, perhaps, find out what price photovoltaic panels have to be pitched to make this happen.
Anyone who has been following progress with our passive solar energy system will know it has performed well recently. Last weekend and two days during this week were no exception. Today has been the first day of near zero daytime temperatures and, unfortunately, it has also been overcast. However, last year, the shortest day was both one of the sunniest and coldest of the winter and results were impressive. This year with the automatic controls for the fans we are hoping for a repeat performance once the cold frosty weather sets in.
There is an interesting comparison which can be drawn between the wall mounted passive solar system and the roof top solar panels people have been rushing to install. If the southwest facing gable of the house in the picture above was glazed (see our pilot system pictured below) then the energy captured by this one house would exceed the total energy captured by all the solar panels on the three houses on the estate. This is mainly due to the orientation of the system – nearer 90° to the winter sun. This week we have been seeing 400 watts/m² of the sun’s energy reaching the wall behind the glazing.
As we are pumping air through the pilot system there is the opportunity to get a large amount of the 6kw/h away: giving us greater efficiency than the roof mounted solar panels. While we are comparing electrical and heat energy systems here it is, bearing in mind the minimal cost of the passive solar space heating system, a good way of making a dent in the 40 kwh/day we use on heating our homes during the winter
Have a good weekend – Peter Kruger
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