Allotment Gardening Advice Help Chat
Chatting => Equipment Shed => Topic started by: Max4 on May 01, 2016, 18:39
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Hoping for a bit of advice, been using a double paraffin heater in the greenhouse over the past few weeks (bought from Halls) but I'm completely fed up with it. No matter how much I mess about with the wick and flame it smokes like crazy, my greenhouse now looks like its got smoked glass.
Looking to next year and I'm considering a solar panel on my shed to run power to the GH and then an electric heater on a simple thermostat. Been searching the net and found these
http://www.beamled.com/100w-panel-kit-adjustable-frame-10amp-controller-5m-extension-cables.html
Anyone any experience of Biard products, are they any good and are there any issues I haven't considered.
Thanks Guys
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The panel you linked to will at its rated maximum (i.e. in very bright sunshine pointing directly at the sun) generate 100W. That is equivalent to 1/10th of a single bar electric fire. You will then need to store that electricity until you want t use it, assuming you don't want to heat the greenhouse when the sun is shining brightly.
Assuming you are going to use a car battery, if you can fully charge an average car battery (40Ah) during one day. It would run a 1kW heater (one bar electric fire) for about 30 mins. It will be drawing about 80A which would cause the battery to 'melt down'. A larger size 'leisure battery' will be huge in size and expense.
These figures are just rough 'back of a fag packet' estimates. The losses due to the panel not pointing directly at the sun, clouds, power losses charging a battery, cable losses etc make solar electric heating really not practical.
Your best bet would be to try to harness the heat from the sun rather than trying to generate electricity. I have a prototype solar hot water heating system in a greenhouse and have enough problems supplying enough solar/battery power to keep the pump (3A) running for a few days (1 min/15 mins during daylight hours). My batteries are reclaimed (knackered) but it is indicative of the problems you might encounter.
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I would go for a solar water heating system, allowing it to warm up a tank of water that could act as a thermal mass and radiate heat through the night. the biggest problem is that the time of year you want the heat is also the worst time for collecting energy through a solar system, in the summer when there is plenty of free solar energy - you dont need to heat the greenhouse.
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So we need a MUCH bigger tank, heat it up for the summer and save it for the winter. ;)
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Ok it's a bit expensive to put together if you are buying new (approx £150.00) |But this is a simple set up that I used on my narrow boat.
X 2 electric scooter batteries 12 v 1 solar car battery charger 1 in car electric fan heater and a 12 v thermostat.
Even during the cold dark winter days my bedroom was lovely and warm of an evening. I ran this constantly and never had a problem with battery life.
You could up grade to deep cycle batteries and a bigger solar charger if you required more than one heater.
I now use the same system to power a halogen light when on a long weekend beach fishing.
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Thanks Guys, looks like its back to the drawing board
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We have PV panels on the house roof and very successful they are. They produce about one third of our power. It is not surprising, therefore, that I have considered solar power in the yard having found paraffin as reliable as you have. The worry I have with solar in the yard is that as has been shown I would need such a big array that it would be highly visible to the various nefarious characters dotted about the place. I plumped for gas which is clean and effiecient and totally reliable. It is more expensive to run but the initial outlay is way smaller than solar.
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Don't want to teach you to suck eggs but be careful of carbon monoxide if you work in the greenhouse with the heater on.
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I couldn't agree more Trikidiki, just think of those youngsters in Greece. Lighting the heater is always the last job in the greenhouse and turning it off the first.
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Don't worry hasn't been lit up until last thing (apart from the 10 mins trying to get it to stop smoking) and then out first thing.
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We use solar power to run our off-grid house and I wouldn't in a million years consider using it for heating purposes in winter: as Oakridge says, you'd need a lot of panels, and if you were talking mission critical, which a greenhouse is, as you can't let it get cold or everything dies, then you would also need some hefty batteries to store the electricity for night-time use or to cover you for periods of cloudy weather. Panel prices have come down dramatically, but batteries are getting ever more expensive.
I notice on the site you link to, Max4, they seem to specialise in lighting. Nothing about heating that I could see.
Shedmeister, how were you charging the batteries? I ask because you talk about a solar charger but you don't mention panels. And what did you do when you got a few cloudy days?
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While looking at power for the house recently we investigated air source heat pumps which looked very good indeed. They generate a water temperature of about 35C which would be ideal for greenhouse heating and still work in low temperatures. The snag for us was that the do not work with an existing domestic boiler and are best suited to underfloor heating. Our boiler is 3 years old and the house is 100 years old. Grown source heat pumps are not suitable for us because the land is full of rocks so excavation would be a right pain. The other thing we have looked at is small scale wind generation - about 1 metre diameter, they are quite expensive.
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We use solar power to run our off-grid house and I wouldn't in a million years consider using it for heating purposes in winter: as Oakridge says, you'd need a lot of panels, and if you were talking mission critical, which a greenhouse is, as you can't let it get cold or everything dies, then you would also need some hefty batteries to store the electricity for night-time use or to cover you for periods of cloudy weather. Panel prices have come down dramatically, but batteries are getting ever more expensive.
I notice on the site you link to, Max4, they seem to specialise in lighting. Nothing about heating that I could see.
Shedmeister, how were you charging the batteries? I ask because you talk about a solar charger but you don't mention panels. And what did you do when you got a few cloudy days?
I bought 2 12v solar trickle chargers from Maplins. They come ready to connect straight to the battery. the kit contains panels and all the electronics. The reason for two :D :D Cloudy days.
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I bought 2 12v solar trickle chargers from Maplins. They come ready to connect straight to the battery. the kit contains panels and all the electronics. The reason for two :D :D Cloudy days.
Are they these?
http://www.maplin.co.uk/p/solar-powered-12v-15w-battery-charger-n31cx
I'm amazed the batteries can store enough power to provide heating. Bearing in mind that Max4 is looking to heat a greenhouse, which presumably doesn't have that much insulation, how many hours of heating to you reckon he or she would get off a set-up like yours and do you reckon the system could get a greenhouse warm enough to make much difference? I'm sure a lot of people would be interested if this really did work.
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I do not know how well this system would work in a greenhouse and instead of the scooter batteries he would probably need a deep cycle / domestic battery. On a full charge these can run the entire lighting system on a 60' boat for a good 24 hours. The heater itself is a low power and set to 15 degrees via the stat would probably last a lot longer. There is also the option for wind generation also used on a lot of live aboard narrow boats
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Thanks, shedmeister. Having read your reply, I remain sceptical your set-up would heat a greenhouse to a useful temperature or for sufficient time. Shame though, as I was hoping to be proved wrong.
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I had considered wind power, our site is on a hill and is generally windy. The pluses would be consistent power without reliance on the sun but I'm concerned about the maintenance factor. I'll admit that I don't have a lot of experience but generally anything with moving parts is going to need fixing/replacing every so often. Also its a lot more intrusive so I'm not sure what the reaction of the other plot holders would be.
The other option I'm considering is putting the paraffin heater in a small house alongside the GH then piping the hot air through and venting outside. Would need to keep an eye on the soot to make sure it doesn't buildup too much.
Anyone any thoughts/experience on either option. Luckily its warmed up so I have the luxury of time to get a solution in place for next year.
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I seem to remember that old fashioned greenhouses were built onto south facing walls (the wall acts as a thermal trap - holding the heat, some had a hot air system which was basically a fireplace on the end wall with the flues running along under the floor (or at least under the raised growing benches). the fire was lit at nightfall and once again the flues held the heat for the remainder of the night after the fire died back.