Allotment Gardening Advice Help Chat

Chatting => Design and Construction => Topic started by: Islandman on April 28, 2019, 13:57

Title: Solar greenhouse heaters
Post by: Islandman on April 28, 2019, 13:57
Hi,
With the advance in solar panel technology has anybody used it to power a greenhouse heater if so with what and how did you do it, or does anybody know of any company who make and supply said item.
Happy gardening!
Title: Re: Solar greenhouse heaters
Post by: TonyB. on April 28, 2019, 14:22
Given that they would be needed in the less clement months, would think small wind generators as seen on sailing boats, charging a leisure battery, would be a better solution. No idea if they exist though. Interesting idea though.
Title: Re: Solar greenhouse heaters
Post by: hasbeans on April 28, 2019, 20:56
There are lots of interesting diy designs out there for passive solar heating using heat sinks (car radiators are one option) and solar powered fans/pumps, not sure how effective they are especially with the hours of sunlight we get when the heat is required.  Probably still more efficient though than trying to turn light into heat using photovoltaic panels.
Title: Re: Solar greenhouse heaters
Post by: sospan on May 08, 2019, 12:28
It is one of my projects for the end of the year. 

I currently have an existing solar system with a panel, controller, storage battery and inverter that takes 12v to 240v. 

I have been looking for a 12v  fan heater from something like a caravan. However, most caravan heaters seem to be designed for 240v hook ups and haven't managed to find a 12v one yet - apart from car screen demisters

Another option would be to go down the 240v and run a conventional heater off the invertor. Although I imagine the power would drain out before the end of the night.

The good thing is that even in Winter solar panels will top up on cloudy days
Title: Re: Solar greenhouse heaters
Post by: Didiaskew on May 28, 2019, 07:36
I've tried the same thing without any success the trouble is for an average sized greenhouse you need between 2 and 3 kw of heating for my polytunnel its more like 6kw even at 2000w that rules out a 12v heater as the max available is around 300w if you use 12v panels and an inverter to 230 the inverter is expensive and you can't store the 230 in batteries, if you use dc photovoltaic panels and an dc/ac inverter a 3kw kit costs around 4K needs a 230v supply to power the inverter and you still can't store the generated power.

It's a good idea in theory but in practice it's just not viable as heating is such a power hungry aplication.
Title: Re: Solar greenhouse heaters
Post by: jezza on August 24, 2019, 20:35
hello when I worked at a market garden in 1984 we put up a new greenhouse that had solar panels built into the roof it looked like clear glass but with small wires in it( every one that saw it thought it was strengthened glass) which connected to a controller that ran the big heaters don't know if the company still makes them  jezza