Solar collectors to heat storage during the day

mousebndr · Sep 23, 2012

Hi guys

Now is getting into spring I am reminded of the hot day cold night scenario, we are getting a lot of sun on our corrugated iron roof so I am starting to wonder how to get that heat into my storage tank.

I have 4000L of pressurized storage at about 1-2 bar.

Is it conceivable that a big solar collector could heat the water up? Can I get temps as high as 80C going in?

I was thinking maybe getting one of those pool heater kits that go on roof but maybe there is a better option.

How to you plump it in so that you get frost protection, ie you pump the water out of the collectors at night or in the snow

sebring · Sep 23, 2012

builditsolar.com has some good ideas if you want to build your own

mousebndr · Sep 23, 2012

sebring said:
builditsolar.com has some good ideas if you want to build your own

Thanks, been looking over those but they all seem to be for small DHW systems which got me wondering - do these systems scale to cater for a large hearing system?

peakbagger · Sep 23, 2012

Conventional flat plate collectors only do a 80 deg F (27 deg C ) max temperature rise over the ambient temperature outside. Therefore going for 80 deg C (176 deg F) is outside the limit of flat plates unless the outside temp is quite high. Evacuated tube type collectors can supply higher temperature water (they can boil) but they need more surface area than an equivalent flat plate. They are also a lot more expensive per btu collected. I expect it would be quite expensive to put in enough collectors to heat up 4000 liters (1056 gallons), but then again it really depends on your demand.

Realize that in the summer you will have to either cover the panels over or install a heat dump on the panels as overheating the glycol makes it deteriorate quickly.

Unless you have a government grant I would expect the econmics would work out.

mousebndr · Sep 23, 2012

peakbagger said:
Conventional flat plate collectors only do a 80 deg F (27 deg C ) max temperature rise over the ambient temperature outside. Therefore going for 80 deg C (176 deg F) is outside the limit of flat plates unless the outside temp is quite high. Evacuated tube type collectors can supply higher temperature water (they can boil) but they need more surface area than an equivalent flat plate. They are also a lot more expensive per btu collected. I expect it would be quite expensive to put in enough collectors to heat up 4000 liters (1056 gallons), but then again it really depends on your demand.

Realize that in the summer you will have to either cover the panels over or install a heat dump on the panels as overheating the glycol makes it deteriorate quickly.

Unless you have a government grant I would expect the econmics would work out.

Knew there would be a catch somewhere

Are there any calculators to tell you how many evac tubes you would need?

Mushroom Man · Sep 23, 2012

mousebndr said:
Hi guys

Now is getting into spring I am reminded of the hot day cold night scenario, we are getting a lot of sun on our corrugated iron roof so I am starting to wonder how to get that heat into my storage tank.

I have 4000L of pressurized storage at about 1-2 bar.

Is it conceivable that a big solar collector could heat the water up? Can I get temps as high as 80C going in?

I was thinking maybe getting one of those pool heater kits that go on roof but maybe there is a better option.

How to you plump it in so that you get frost protection, ie you pump the water out of the collectors at night or in the snow

I was intrigued by this site's idea (http://www.builditsolar.com/Projects/SpaceHeating/Thomason/Solar_Heat.pdf) for DHW and heating during winter. The idea of processing less biofuel is appealing and the incremental costs wouldn't be too bad if the solar worked as well for me as it did for the customs house in the article. Rather than a black paint on steel, I'd be tempted to use black polyester felt which has the effect of increasing the surface area in contact with the water. A polycarbonate (from a greenhouse supplier) over the felt would retain the heat as a substitute for glass. While evaporated tube in winter heats to higher temperatures, the cost would be high for an application like space heating; whereas this style of flat plate may have sufficient output due to the large surface area of the collector.

mousebndr · Sep 24, 2012

Mushroom Man said:
I was intrigued by this site's idea (http://www.builditsolar.com/Projects/SpaceHeating/Thomason/Solar_Heat.pdf) for DHW and heating during winter. The idea of processing less biofuel is appealing and the incremental costs wouldn't be too bad if the solar worked as well for me as it did for the customs house in the article. Rather than a black paint on steel, I'd be tempted to use black polyester felt which has the effect of increasing the surface area in contact with the water. A polycarbonate (from a greenhouse supplier) over the felt would retain the heat as a substitute for glass. While evaporated tube in winter heats to higher temperatures, the cost would be high for an application like space heating; whereas this style of flat plate may have sufficient output due to the large surface area of the collector.

I wonder how high their temps get. Might be worth throwing some black pipe on the roof and seeing how hot it takes and how long I suppose.

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Solar collectors to heat storage during the day

mousebndr

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sebring

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peakbagger

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