Colin putting in one of the glass

Colin's Solar water heater

Our good friends Chris and Beata last winter moved into an ecological house with installed solar panels. They had been very pleased with them, and Chris said, "Installing them would make a nice project for you." And so it was. I did some research and bought the "budget" system from Navitron. It cost £855, including discracefully, £127 The heat pipe entering the manifold

of VAT to the government. Grants of £400 are possible, but not if you do it yourself. In fact you must use an "accredited installer" who has to pay for accreditation. One such UK company, Apricos, charge £3199 for a comparable system. The Navitron system has Chinese made vacuum tube collectors, but the rest is built in the UK at Rutland. The collectors are like long thermos flasks and heat up to very high temperatures in the sunshine even when it is really cold outside. No water circulates inside them. Instead a "heat pipe" of sealed copper tube filled with high pressure liquid which evaporates and condenses to transfer the heat. The setup at 116 New Road

The heat-exchanger in the immersion heater socket

The solar heat exchanger fits into the immersion heater flange of the hot water tank, so that no new tank is needed. The picture shows the hot-water tank in our airing cupboard. Thin 10mm diameter copper tubing runs through a central heating pump up into the loft of our bungalow. We have an ideal south-facing gable roof above the lounge, and the pipes ran across the loft and into the collector. The system included a 3 bar pressuriser system which gives improved efficiency. The bleed valve in the loft

The most tricky bit turned out to be drilling the holes in the tiles to take the two 15mm diameter water pipes. Several tiles were broken and we were so lucky to find replacements on a chance visit to the tip! Another tricky bit was leak testing. The system has 20 or so compression joints and a similar number of "solder ring" joints. The solder joints gave no trouble, but several of the compression joints leaked, sometimes at embarrassing times and places, like just before a concert on the top of the roof under the insulation! Usually simple tightening did the trick. The pressure system

On 17/10/8, about two months after I had taken delivery - but including two holidays, the system worked OK. The graph shows the temperatures on the roof, and in the tank during the day. The simple controller switches on the pump when the temperature difference between these two temperatures exceeds 6C. It was on most of the day and raised the water temperature by about 9C at about 2C per hour while the sun shone! The weather was sunny in the morning, but large clouds came at around 2.00pm as shown, and it was mostly cloudy after about 4.00pm. The first day of successful operation