Would it work??

[johnmac]

Quite possible a stupid idea... But hey ho!

I have a 8.5ft x 12.5ft greenhouse outside. Currently, it's in full sun and 18oC.

My house, heating off, is currently 9oC.

Would it be possible to pump air from the greenhouse into the house? Would it heat the house and what would it cost?!?

There's been days, such as today when it's sunny outside with a freezing wind...

Probably utter daftness, but just wondered!

[guydewdney]

not a dissimilar idea to a "trombe wall".

http://www.ask.com/wiki/Trombe_wall

[billi]

I do it on nice days  

http://www.navitron.org.uk/forum/index.php/topic,2188.45.html

Now i have taken out  the Fan off my kitchen hood and blow warm air in

But sure mine its a bit bigger and has a dark wall

Billi

[EccentricAnomaly]

I think it's an excellent idea assuming you don't mind that it'll cause your greenhouse to be cooler; in particular, it'll store less heat during the day so be cooler the following night.

On the other hand, the amount of energy you're likely to collect will be pretty small. Consider how long it'll take your greenhouse to warm up again after you've done an airchange and how little heat there is in the air: about 1.3 kJ/(m³·K) so a cubic metre of air holds about the same amount of energy as a quarter of a litre of water for the same temperature difference.

I think it's a much better idea than a Trombe wall. In general, making the solar collector thermally lightweight so that the energy from any short bursts of sunshine can be squirrelled away quickly is a good idea. Trombe walls are thermally heavyweight with the idea that the energy is stored in the collector which probably works fine in sunny climates (S of France, New Mexico) where you can store a lot of heat during the day and it's nice to release it in the evening. By contrast, in Britain it'll probably result in most of the heat being radiated back out again before it's used.

This might be a good place to start looking for ideas:

http://www.builditsolar.com/Projects/SpaceHeating/solar_barn_project.htm

If you want to try with the greenhouse then I'd suggest improving its solar heat absorbing characteristics: perhaps some lightweight black material hanging up on the north side, for example.

[dhaslam]

A greenhouse isn't an ideal way to collect heat from the sun  because there isn't a  dark surface to collect the heat.      A sheet of  black painted Correx will reach about 80C  in full sun at this time of the year.    Fairly easy to make  as in the  video below.   It needs a fairly powerful fan  but not  the 6.25 HP motor in the video.      The Navitron  warm air heaters would be better again and would also work in fairly dull weather as well.

www.youtube.com/watch?v=cGjCzfftMgc

[Stefan (S.T.E.F.)]

Where can I find this navitron air heater thingy ?
Don't seem to find it in the shop. Maybe I am not looking properly ?

[EccentricAnomaly]

Where can I find this navitron air heater thingy ?
Don't seem to find it in the shop. Maybe I am not looking properly ?

Weirdly, they're hidden on the hot water panel page:

http://www.navitron.org.uk/product.php?proID=115

SFG20 towards the bottom of the page. Better than a locked filing cabinet in the basement with a sign saying "beware of the tiger" but not much.

[johnmac]

Thanks all for the replies!!

Daft, but not lunacy!

It's got me thinking. There are sunny days in the winter when the sun gives out a decent bit of heat when out of the wind, or like today when you stand in my greenhouse, which hit 22oC on Monday!!!

What would be my options to trap heat and use it to heat the house?!? The cheaper the better!! Or in the winter is it just not possible/reliable enough??

Thanks for the info so far! Some great reading.

[Stefan (S.T.E.F.)]

Navitron did a good job of hiding that panel !
Not a bad idea for my polytunnel (that I still need to build....). Might extend the season for growing up here even further.

There are many home made versions on youtube to experiment with first if you want to see if it's viable for contributing to heating the house...

[billi]

22°  is not a lot  , just for an experiment i would  cover the north wall with something Black

Billi

[Stefan (S.T.E.F.)]

No, it's not a lot if you have to transport the air from the greenhouse to the house. Still, it's 13°C more than his house was... so experimenting with a hot air panel might be worth it... in the meantime take a good book and a comfy chair to the greenhouse...

[billi]

....   i have over 60° some days during winter autumn spring in my poly tunnel  , so why should i buy a solarpanel  for my tunnel , when a good designed tunnel is a panel itself ?

PS my tunnel costed 350 Euro 

Billi

[baker]

its a good idea
to transport the energy from the poly tunnel
you can use a hrv unit with 60 c you will get a very high cop
just need to watch the temperature / hp pressure, to get a unit to work at 80 may be a challenge
baker

[Stefan (S.T.E.F.)]

....   i have over 60° some days during winter autumn spring in my poly tunnel  , so why should i buy a solarpanel  for my tunnel , when a good designed tunnel is a panel itself ?

PS my tunnel costed 350 Euro 

Billi

Well, yes, but you are hardly in the north highlands.... also I would want to heat the soil with it, not the air... or I could just extract the hot air from the top of the tunnel to heat the soil... all ideas to play with when I have more time on my hands.

So maybe the OP should put a polytunnel right next to his house and extract hot air from there and blow it into his house ? Could work....

[Ivan]

The big thing to watch out for is that, due to the very low heat capacity of air, it is easily cooled during transportation. In solar circuits, it's not unusual to lose 25%+ in transit over 10m or less. If you're working with air, even with a lot of insulation, you'll probably lose the greater part of the energy between the greenhouse and the house, unless your greenhouse (like Billi's) is adjacent to the house, in which case losses are negligible.