I thought it would be interesting to see if the manufacturers claims were valid so i started measuring the temperature of the incoming air into the Solarventi and the temperature as it emerged into the room.

Although the dehumidification effect is extremely effective, I found that the incoming air temperature was only being raised by between 8 and 11 degrees C versus the promised 15 degrees and promptly called the supplier. They asked a few questions and then provided the following explanation. Attempted summary:

If the fan is unregulated and the solar cell is brand new then it will whir away at a fair old rate due to higher voltage 13+ V being generated - which it does - regardless of the temperature you want. When the solar cell settles in, the voltage that it generates drops a little back to 12 volts. However that still did not explain to me why i was not getting the claimed maximum 15 degree uplift.

Again the explanation was that if the airflow in the device can be slowed down then the full uplift is achievable under ideal sunny conditions. The two alternatives that emerged were that i wait for the solar cell to settle in which is what i am doing. When it is settled in it will generate less power and the unit will perform to spec. The alternative is to buy a regulator which is apparently supplied as standard on the larger Solarventi units. It is not an expensive item about £25 but could be important for full control of the device in some circumstances. Anyway I thought i would wait and see before getting one. With the current heatwave the air is quite warm enough and the unit is performing well - my girlfriend is going to put the washing in that room to dry now. I still haven't wired up the off switch that was provided for the device.