Although not directly caused by the recent hot weather, we have been working on two very different solutions to overheating in solar thermal systems. The high tech device that looks like an air-conditioning unit is a fan cooled radiator fitted as part of an oversized domestic system designed to contribute to the space heating requirements in spring and summer. In the height of this summer’s mini heatwave, the collector would be boiling away on the roof (a condition known as stagnation) if the cylinder was already full of piping hot water. A motorised valve opens, the 4kW heat dump switches on and the manifold, pipework and glycol are quickly cooled down to a safe level. At the low tech end of the spectrum we designed a small heat dump for a client who’s system only occasionally stagnated but who could see that it was not very beneficial for the system to do it. He improved upon our idea of putting the radiator in the loft by suggesting that it went outside, on a north facing wall, just below the eaves. He not only suggested the position, he painted the radiator and welded up some substantial brackets to support it on the wall which was an enormous help to us. The 1.5kW ‘output’ of the radiator is enough to quench the collector’s enthusiasm for generating heat and worked surprisingly quickly in a recent test.
The obvious difference between the two approaches is price, with the fan assisted unit costing far more than the radiator. Both systems work well and the trick is to do the calculations to see what level of dissipation is required – before the problem arrises. There are a huge number of variants in between these two examples and, spurred on by the lovely weather, we’re looking forward to designing yet more inventive solutions to fit each customers particular requirements.