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Producing Your Hot Water Using The Power Of The Sun

We wanted to reduce our gas consumption, the heating is not on during the warmer months but the boiler was still active producing hot water. When we had our new efficient gas condensing boiler installed we also replaced our hot water tank with one that was suitable for solar panels - looking ahead and making life easier, which means lower installation costs. As Good Energy [Link] customers we were directed to Freesource Energy for their solar hot water system.

Solar thermal systems can provide all domestic hot water needs in the summer and around 25% during the less warm and sunny months, overall providing 50 - 60% of a home's hot water requirements for washing and bathing over the year.  Sunshine at any time of year will heat the water, and warm weather even when it is cloudy will also produce hot water. At the moment Good Energy are also paying us around £70 a year to produce our hot water as part of their HotROC scheme, this is in addition to what we save on our hot water bills.  We received a grant of £400 from the Low Carbon Buildings Programme; this was the maximum grant towards the cost of installation at the time.

The key thing is to allow the sun to heat the water to its full potential, and only turn on the gas if needed to give it a boost. Even in the winter the solar thermal system will take the chill off the water in the tank, so there is less for the gas boiler to do.  When we had our system installed in November 2008 and were amazed that even in that dull, cool month it was making the most of the sun.

Our house was not an ideal choice for installing a solar technology; it is at the north end of our road and has a roughly east-west facing roof.  We had collected data from June 2006 – January 2007 on the incidence of sun on our roof during the day and related this to sunrise and sunset times.  This was used by Good Energy and Freesource Energy to assess the suitability of our roof, together with Freesource Energy’s own measurements of roof orientation and presence of trees and other buildings.

We could have obtained maximum hot water from our solar by having panels on both the east and west facing roofs, and possibly by using evacuated tubes instead of flat plate panels.  However, this would have been much more costly and would have required a more complicated system to separately operate the two sets of panels.  With two sets of panels, if one panel had the sun on it and was bringing heat into the hot water tank, the other panel out of the sun should not also be feeding into the hot water tank as it would be at a lower temperature.  Therefore, we decided on two flat plate panels on our east facing roof; it was not due east but had some south orientation and so sun was on it from the early morning until the afternoon.

Once it was installed we found ourselves checking the monitor every day to see how long it had been operating for.  We would also monitor the hot water tank sensor and the panel sensor and watch the temperature on the panel rise until it transferred heat into the hot water tank.  They do say that having solar hot water puts you in touch with what is happening with the sun and how much energy it takes to produce your hot water.  Over a year later we are not monitoring it so avidly but we do still feel a connection to the sun and an awareness of how much hot water we are getting from our panels.  Certainly we are running our boiler a lot less and turn it off for the summer, only turning it back on to boost our hot water during cloudy cool periods.  Even in the winter we use the boiler less than previously as the hot water is boosted by sunny days.