Heating my greenhouse

Hi all just joined the forum after reading a good few posts and think it amazing
Got my plots last year and built my shed and sorted my rain water harvesting out my next step is the green house I'm planning a 8x24 as below made from reclaimed Perspex sheets I'm planning on sectioning it off into 3 (8x8) each and making double glazed units out of the Perspex for the roof and front part of the centre section in the hope the outer sections will help insulate in the winter? I have a good soler set up running pumps lights etc but I'm looking for a renewable way of heating it my ideas so far
Get an old fridge/freezer and use it as a heat exchanger with either the exchanger in the centre part using a fan blowing across it or
Make a new exchanger and put it into a recycled hot water tank filled with oil (heats up quicker than water) and then pump that oil into radiators for heating using a inverter to power
Other options would be get a oil filled radiator and convert the element to a 12v dc one
I've done loads of research but can't seam to find anything on which will be more efficient and effective
Sorry for the essay hoping for ideas thoughts and suggestions
Thanks all

 

If you are trying to build a heat pump to transfer heat from (say) ground to greenhouse, then it works optimally when temperatures are close. Otherwise the heat pump can use a significant amount of energy. Are you expecting your solar power system to power the pump for the heat exchanger? Don't think it'll produce enough oomph when you need it in the cool spring and skies cloudy.

 

No was planning on putting the cooling part on the outside then the heat exchanger in one of the way mentioned my solar system will easily power it it's only around 150w drain my system is running around 1k with a mppt controller and 6 110a/h leisure batteries but in the winter when the heating will be used it's only around 70% efficient otherwise I would have thought about using a fan heater

 

Take it you'll be insulating all the non perspects bit?

 

Yep it will all be insulted probably with kingspan

 

That's rather rude and disrespectful of them!

 

Confused as to what you mean lol

 

@Notty1975 you wrote that "it will all be insulted probably with kingspan"

Think @Scrungee was just saying having kingspan insult your greenhouse would be really horrid of them!

Hopefully they will be insulating it instead!

 

Omg didn't even notice that lol heads not quite been with it been busy on the land putting a fence up

 

@Scrungee naughty boy. No trolling

You need a spanking!

 

@Notty1975 loving your fencing - some great ideas and plans you have - busy, busy you'll be but excellent start for next years growing season

 

Hi,

Have you got the perspex sheets ? How thick are they ?

Having seen a friend trying to replace some glass with 3mm perspex on a greenhouse with standard 2ft sheets you could see they flexed to such a degree that they were almost coming out of the retaining clips.

Looking at your pictures it seems you are going for 3ft panels, so you may need additional struts to prevent bowing and allow a much wider rebate at the edges to hold it securely.

If you can get 10mm twinwall polycarbonate its much stiffer and has high insulation properties.

For your heating, so many green ways to do it, but would suggest in one of your sections where you house your best plants, that you uses a main electric 1 to 2kw fan heater and a good electronic thermostat thats set to 3 or 4 deg c so you ensure its kept frost free.

 

The Perspex is 6mm thick and will make sure the rebate is quite deep it's not going to be held in with clips there's going to be beading holding it in
As for the heating the fan heater I think would put a lot of strain on my solar setup but have been doing a good bit of research and think I'm going to go down the jean pein method as there are 4x4ft cubed compost bins right next to the greenhouse so should be able to keep nice and warm

 

4x4 is fairly small for a Jean Pain method ... I do hope it works though and will look forward to seeing updates and pics of your project.

 

It is a bit small but am currently trying it with a rad in my shed and the compost is running around 65c it has been for 2 weeks now it's doing a good job I think I may have to put fresh compost in more frequently that's all which is not a bad thing plenty of good compost plus free heating win win