Solar Heating panel

[Abdullah1986]

Dear All,

I need to know for solar heating panels, is there technology available that could help control the temperature??

[Tesla]

Hi Abdullah
There are many technologies available for control of the temperature. The main method is via controlling the flow rate. Two main methods are to use valves to divert or restrict, the other is via variable speed if a pump is installed to move the fluid. Another method is by moving the panels toward or away from the sun.
It depends on the size and cost of the installed system. I worked on a new hotel which used a large amount of panels for domestic hot water. Also seen many articles about using a small photovoltaic cell to power the pump to provide proportionate flow rate to the solar input. In Ausi we can get a magazine called Renew published by the Alternate Technology Association. They have a web site. They also produce and sell many good books on the subject.

[Brian_UK]

You could have a heat dump circuit to waste excess heat.

Or you could arrange automatic covers to shade the panels when required.

[Rerseldergo]

hey. great to be here, not sure if this is the right place to post this

[MikeHolm]

Look up RESOL.com for a controller. All solar systems need to have a proper and designed storage volume/ m2 of collector absorber area and for DHW the general rule of thumb is 50-100L of storage. If you use less, be prepared to have glycol temperatures (assuming you are using antifreeze) which will stay at elevated temps (140C+) for long periods of time. The result will be the need to change glycol every couple of years or the PH of the system will be quite acidic.

The other accepted options include having a dump load or a second, less important load to switch to. Assuming it is a pressurized system the expansion tank MUST be big and it must take into consideration both the massive swings in temp (200C at times) and the fact that the entire collector area can change to steam, pushing the rest of the liquid into the balance of the system (expansion tank).

If you have a drainback system, there will be no need to control other than shutting off the pump at the correct time.

[dfaz]

domestic hot water is calculated by the number of people occupying the property 50 litres per person plus 50,ie 3persons @50litres +50=200litre store .A 200 litre store would require aprox 4square meters of flat plate or three evacuated tube panels (18 tubes)aprox 3.4m square gross apature.More water storage requires larger panels up to a point if the system reaches temperature and goes into stagnation(boils and turns to gas)the system canot run if you then run off the hot water untill the system cools at night,so if you do oversize your panels build a heat dump into the system to lose heat on high radiation days,secon solar will advise you as far as expansion vessell controls etc and are good to deal with.
hope this helps.

Dave