We have very deliberately oversized our solar thermal installation to try and provide 100% of our hot water and heating demand purely from our 44 sq metres of TiSUn flat plate collectors dumping hot water into our two TiSUN Proclean 1500 litre stratified hot water thermal stores.
Firstly, we worked on a principal that a family of 6 may consume up to 300 litres of hot water per day for washing and cleaning - storing 3000 litres of hot water approximates to about 7-8 days worth of hot water storage.
This means we can afford for our solar panels to be ineffective for about 7 days on the trot, which of course with our foggy, cloudy days can easily happen in the UK. After I have paid for the initial capital cost of the equipment their is effectively NO running costs - the day light necessary to heat the water in the panels being 100% FREE. The main issue as I see to us not using more Solar thermal systems, is the lack of hot water storage most of our solar systems come with - typically 200-300 litre tanks. This means at most there is ony about 1 days worth of hot water storage. In the winter months when we need our hot water the most for our heating as well as our hot water needs, we have the last amount of storage. With an average cost of a ground source heat pump with either boreholes or slinkies fully installed being about £20,000 - its seems to make most sense spending your money on a larger thermal store to store more hot water days and more solar panels to make use of the smaller amount of available daylight - then put in an immersion heater for your short falls, placed on a timer on an Economy & tariff.
Once again if you can minimise your heating demand for the property (or take it down to ZERO which we have done) then all the hot water in your thermal store is available for your hot water needs.
There are some interesting thermal stores in the market mainly from Germany and the Scandinavian countries, here are a few others to investigate and make your own decusions on. Future advances in the latest
