What happens to solar systems in very cold weather?

It has been the United Kingdom’s coldest night of the winter, and in some places in Scotland temperatures have fallen to twenty degrees below freezing. How, in these conditions, will thermal solar systems respond?

The picture shows a Genersys thermal solar installation in Slovakia. The lower parts of the soalr panels are covered with ice, die to shading, but the upper parts are ice free and the system is delivering useful heat in the middle of a Slovakian winter.

Solar panels are usually mounted on the roof. The roof is (or should be) insulated from the rest of the house so that in cold weather your heating system does not waste energy heating up the roof. The roof, in these conditions is the coldest part of the building by a large margin and is usually made from materials that get cold easily and stay cold. The solar panels will be exposed to below freezing conditions and will also fall in temperature to below freezing. Inside the solar panels are pipes filled with heat transfer fluid. If the fluid freezes in these very low temperatures the pipe inside the panels will burst and the panels rendered useless.

This potential problem is overcome by using a special anti-freeze agent in the heat transfer fluid. The solar thermal industry has been using for many years a food safe polypropylene glycol as anti freeze. The concentration of the glycol can be varied, so that in places where the temperatures may reach a few degrees below freezing a ten or twenty percent solution may be safe enough, but in most temperate and central European places we recommend a 40% solution, which will protect the panels to at least minus thirty degrees Celsius.

So solar systems will be protected from frost damage, and some of them will actually give a modest performance in very cold conditions. Flat plate panels will reflect modest amounts of heat back up through the glass which will be enough to create a film of water immediately on the glass, from which snow and ice will slide.

Most flat plates will work in temperatures of up to minus ten Celsius and in day light snow conditions they will work better than you might expect, because of the amounts of light that will be reflect off the snow on to the panels.

If you have got a good quality solar thermal panel installed by an installer who knows his or her job, your system will cope with whatever the vagaries of the British weather can deliver.

3 Responses

  1. Robert

    Do the panels work in the Ifra red spectrum even in darker conditions or are they working on a sealed vaccum system like one of my freinds sysytems in Austrailia.

    He said his have a small vaccum ball at the end of each tubes which capture the heat and transfer it along another sealed tube, he says his entire water heating bill for the years, when he has to top up with the grid in the colder season was less than a tenner for the whole year, now thats what I call fullternative.

    Have you heard of the project that a german company is looking into, building a solar coplex in the hooter parts of spain and transferring the power using the existing grid to other countries including Germany ?

    • Solar panesl in Australia will perform better than most other places. they all work across the infra red spectrum and with our vacuum panels you can find them picking up radiation at night (though not enough to be useful, only measurable!

  2. […] What happens to solar systems in very cold weather … – Jan 09, 2010 · Robert. Do the panels work in the Ifra red spectrum even in darker conditions or are they working on a sealed vaccum system like one of my freinds …… […]

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