The solar panels are up, and on a not-very-sunny day got the water in the domestic cylinder up from 22 to 40 degrees, an 18°C rise, requiring 20°C of additional heating to get the cylinder to its operating temperature.
The temperature rise in the cylinder would have been greater, as the panel exit temperature was 61°C, but the long feed pipes from the loft to the cylinder are not yet insulated.
But it got me thinking.
At the moment, the two panels are plumbed in parallel.
If there is not enough sun to heat the panel working fluid above 60°C on a particular day, would it be advantageous to switch the panels to a series configuration. It would only take a couple of three port valves.
I think it would, and that it would almost double the temperature rise in the working fluid. A friend of mine disagrees and reckons it will make little or no difference.
Does anyone out there know the answer?
And can any one explain it using an electrical analogy so that I can understand without having another go at thermodynamics?
If you can settle this argument, please comment at the bottom of this page, or to firstname.lastname@example.org
It also occurs to me that a variable speed pump would help here, the installation is fixed speed, with a feedback loop to throttle back the pump until the panel exit temperature is regulated to the required temperature.
Do people do this?