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Question:

servamatic solar water heaterHi I have a garden pond (approx 700g) which I need to keep as warm as poss (in UK) – I have made a simple water heater to test the principle of solar heating. Its an aluminium frame (about 1m square) with a coil of garden hose sprayed black & polycarb cover. It works by a 12V pump & a differential thermostat, i.e as soon as the temp in the heater is a few degrees warmer than the pond, the pump circulates until the heater has filled with cool water.Its already struggling to get the pond to a reasonable temp (20C) even on a good sunny day. Does anybody have any suggestions on making a more efficient heater before I start re-inventing the wheel (is there a FAQ?)servamatic solar water heater The main questions I have are – how much effect does pipe diameter & material have & what improvement will I get by tracking the sun horizontally & vertically.

Response:

servamatic solar water heater – Hide quoted text — Show quoted text -servamatic solar water heater Hi I have a garden pond (approx 700g) which I need to keep as warm as poss (in UK) – I have made a simple water heater to test the principle of solar heating. Its an aluminium frame (about 1m square) with a coil of garden hose sprayed black & polycarb cover. It works by a 12V pump & a differential thermostat, i.e as soon as the temp in the heater is a few degrees warmer than the pond, the pump circulates until the heater has filled with cool water.Its already struggling to get the pond to a reasonable temp (20C) even on a good sunny day. Does anybody have any suggestions on making a more efficient heater before I start re-inventing the wheel (is there a FAQ?servamatic solar water heater) The main questions I have are – how much effect does pipe diameter & material have & what improvement will I get by tracking the sun horizontally & vertically.

I’ll take this one.servamatic solar water heater Depending on the type of mount you probably only need to track in one axis. Since this project is for a pond I assume it will mostly be used in the warm season. It’s easy to get from 150% to 200% of the non tracked version. Since the temperature rise is low a concentrator is not required.

Duane —     Home of the $35 Solar Tracker      Receiver

Response:

I have a garden pond (approx 700g) which I need to keep as warm as poss (in UK)

Your main problem is size, or rather, servamatic solar water heaterlack of it. Tracking will typically buy you 30-40% at most – and it’s a real pain with a water collector. Doubling the size of the collector will get you 100% and no need to try to move a water-filled collector. If you go to www.dejanews.com (which is now actually somewhere less memorable on google) and do an advanced group search in this group, there’s another chap in the UK who has done quite a bit of experimenting in the past year or two, perhaps for a swimming pool rather than a pond.servamatic solar water heater For pond heating (inherently low temperature) the upside of plastic being cheap (so you can have more collector area at similar cost) more than offsets any improvement from metal (which is mostly seen at higher temperatures, anyway) – also you don’t kill any fish, etc. you have in the pond with stray metal corrosion products. — Cats, Coffee, Chocolate…vices to live by

Response:

- Hide quoted text — Show quoted text – Hi I have a garden pond (approx 700g) which I need to keep as warm as poss (in UK) – I have made a simple water heater to test the principle of solar heating. Its an aluminium frame (about 1m square) with a coil of garden hose sprayed black & polycarb cover. It works by a 12V pump & a differential thermostat, i.e as soon as the temp in the heater is a few degrees warmer than the pond, the pump circulates until the heater has filled with cool water.Its already struggling to get the pond to a reasonable temp (20C) even on a good sunny day.servamatic solar water heater Does anybody have any suggestions on making a more efficient heater before I start re-inventing the wheel (is there a FAQ?) The main questions I have are – how much effect does pipe diameter & material have & what improvement will I get by tracking the sun horizontally & vertically.

A garden hose can be a good insulator, depending of what material it’s made of, and keep the heat out. I suggest you use soft copper metal tubing painted black instead. Your efficiency should go up by about 40% at least. If you covered this tube with a glass covering, you could double your efficiency, from the trapped heat under the glass. You do not have to track the sun, if your panel is properly oriented, and is large enough.

Response:

Thanks for the replies – the cost & simplicity advantages of plastic over copper was mainly what I was looking at. I don’t really want to make it much bigger for aesthetic purposes. I think the mark 2 may use 25mm plastic pipe. Will the polycarb cover improve or degrade it – I assumed it would give a ‘greenhouse effect’  - but other ‘bare’ black plastic objects seem to get much warmer than the metal parts of the panel covered by the plastic sheet. I may experiment with a homemade tracker at a later date. Thanks Neil

Response:

HI Neil Had you considered using an old central heating radiator as a collector.servamatic solar water heater Not ideal for domestic hot water heaters (fairly slow to heat up) – but pretty easy to try out….. I made one of these many years ago – seem to remember that I had two old rads – total of about 3m-squared – in a home-made ‘cold frame’ – and it produced startlingly hot water! I’m not sure about using plastic tube – don’t know how good it is at insulation – Another way (very low-tech) is black-painted  iron / steel roof-sheeting in a cold-frame – with water running down the ‘valleys’, Collect it in standard plastic gutter at the bottom end – and distribute it in some way (Cu pipe with holes in it ?) at the top end. Fit your temperature sensor to the sheeting. Crude but effective <g Have fun Adrian Suffolk UK

Response:

Had you considered using an old central heating radiator as a collector…

I started alt.solar.thermal for “PRACTICAL uses of the sun’s heatservamatic solar water heater.” Maybe we need another group for impractical uses, eg systems with very low efficiency

Response:

Thanks Adrian Ive got an old radiator & was my 1st thought – but then I started to worry about the effect the rust on the pond – plants, fish etc. & it will rust because you’re pumping air enriched water through it. Nick – surely any hombrew use of the suns energy is a PRACTICAL use – especially if the alternative is to use electricity or burn fossil fuels to get the heat. regards Neil

Response:

- Hide quoted text — Show quoted text -servamatic solar water heater Hi I have a garden pond (approx 700g) which I need to keep as warm as poss (in UK) – I have made a simple water heater to test the principle of solar heating. Its an aluminium frame (about 1m square) with a coil of garden hose sprayed black & polycarb cover. It works by a 12V pump & a differential thermostat, i.e as soon as the temp in the heater is a few degrees warmer than the pond, the pump circulates until the heater has filled with cool water.Its already struggling to get the pond to a reasonable temp (20C) even on a good sunny day. Does anybody have any suggestions on making a more efficient heater before I start re-inventing the wheel (is there a FAQ?) The main questions I have are – how much effect does pipe diameter & material have & what improvement will I get by tracking the sun horizontally & vertically. Thanks Neil

Needs to be way bigger – not just twice the size. Nick W made one that worked well, see the newsgroup. Plastic hose coiled, polythene sheet cover is all thats needed. The temp rise is so low its pointless using anything better.servamatic solar water heater A big foil reflector may be a cheaper way to add more heat than more piping. Spacing the pipes out by about half to one pipe dia helps a bit as well, each pipe gets more sun when the sun angle is lower. NT

Response:

Had you considered using an old central heating radiator as a collector..servamatic solar water heater. I started alt.solar.thermal for “PRACTICAL uses of the sun’s heat.” Maybe we need another group for impractical uses, eg systems with very low efficiency

But super cheap systems. Flat steel panel radiators work quite well, and they are very cheap. As they are ferrous you need a heat exchanger.

Response:

…Flat steel panel radiators work quite well, and they are very cheap.

Please tell us more, using numbers. What do they cost, for what size? servamatic solar water heater How would you glaze them and estimate their solar collection efficiency? As they are ferrous you need a heat exchanger.

What kind? How much would it cost? What’s its efficiency?

Response:

…Flat steel panel radiators work quite well, and they are very cheap.servamatic solar water heater Please tell us more, using numbers. What do they cost, for what size? How would you glaze them and estimate their solar collection efficiency?

Who cares. The roof is big, so lots of space, and the radiators are cheap and work well. You can pick them up used for free. If you want highly efficient solar collectors to collect as much solar gain as possible in a limited roof area then get thermomax panels and pay the earth. As they are ferrous you need a heat exchanger. servamatic solar water heater What kind? How much would it cost? What’s its efficiency?

A cheap indirect internal coiled cylinder is available very cheap, about 80 GBP, well in the UK anyway.  I know of one solar system using cheap panels radiators and an indirect cylinder  that has been going for about 25 years. Only one pump has bee replaced in that time.  It requires 1 litre of inhibitor about every 3 to 4 years which cost about

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