In January 2015, I posted an update of my attempts to make my home more energy efficient. So far, I have concentrated on insulation, and monitoring the effects. This link describes the progress.
This summer (2016), I decided to try out an idea mention by another member, Donald. The idea was that you could make a solar thermal panel by painting a central heating radiator black, and putting it in a double glazed, insulated box. That is what I have done using a 20 year old central heating panel left over from when I removed my central heating several years ago.
This is a graph of the temperature produced by the panel from the end of July to the end of August (2016). The graph mid-line is 50 degrees Celsius. Continuous live temperatures from the panel can be seen here:- https://personal.xively.com/feeds/940955947
The panel is connected to a towel rail in the bathroom, and heats the rail by thermo-cycling, no pump would be required, except……
The towel rail cannot dissipate all the heat produced by the panel on hot days, and eventually, when the temperature passes 70, stagnation occurs, thermo-cycling stops and the towel rail cools down. To combat this effect on hot days, there is an Arduino sensing the panel temperature. When the temperature hits 70, the Arduino sends a signal to turn the pump on, which restarts the circulation.
What I am mostly interested in, is how the panel will perform during the autumn, winter and spring periods. When the results are in, I will be able to decide if it is worth adding additional panels to heat my hot water cylinder.
Update November 2016: The panel is not producing any usable heat now. I have drained the system and switched the towel rail back to electric mode.