First Test of the Greenhouse

[Yorkshire Kris]

Well temperature inside the greenhouse did eventually start to fall and the max/min inside the greenhouse read a high of 27.2 and a low of 8.9 so I assume that the heat sink eventually ran out of 'fuel'.

As Kristen says, ground source heating is a good method and the heatsink will benefit from the surrounding ground temps so I am hoping that won't ever fall below the 5c mark in winter and have a cooling effect in summer (although that's not important as I remove the panels).

I'm not really looking forward to colder weather or shorter days but I should be able to draw more conclusions once the conditions deteriorate, Over all things look promising at the moment.

I'm pretty certain that a heater will be required to keep above freezing during the coldest days and nights in mid winter. Saying that, you system will be cheap to run as its keeps the heat for so long following sunny days.

[GoggleboxUK]

Yes Kris, I agree.

Today has been a lot less sunny and it's currently only 16c in there so it will be interesting to see what sort of effect it has on tonights low.

I think once the surrounding oaks lose their leaves it will get more light but obviously the sun will be less strong too.

[Adrian]

All sounds interesting ....but....keeping a high temperature now means nothing, my greenhouse went down to 4c but at that nothing gets damaged, as you have already mentioned, when we are getting winter daytime temps of below 10c, below 5c or just above freezing then this system will surely have no benefit at all and they are the times you are going to need heat.
I'll watch with interest as the winter takes hold but at the moment I cant see it doing anything benificial that will make it better than my set up of a 2kw fan heater.

[GoggleboxUK]

Ade the idea is that I can have the heater on and the pumps running so the heat will go into the sink that way.

That stored heat is slow release and costs nothing but the alternative is to heat a space that immediately starts to lose heat and so the efficiency of the fan heater at maintaining a 5c minimum costs much more.

It's all theoretical, time will tell I suppose. It could end up being just backache and cost I didn't need but, on the other hand, it could make a tidy saving in leccy bills each year.

[Adrian]

I wish you well with it and in no way am I knocking it.
How do the pumps work then ? how are you pulling heat down into the ground ?
If you are running pumps and heaters then I wonder what the cost difference will be opposed to straight fan heater, as you say time will tell.

[GoggleboxUK]

They are just bog standard inline extractor fans Ade, they pull the air straight down a 4" duct pipe then a 90 degree angle takes it across the length of the greenhouse at a depth of 3ft.

This 15ft long pipe at the base of the gravel has lots of small holes drilled along the top where warm air escapes into the gravel pit. There's then another 90 degree angle that joins a pipe to bring the air that hasn't escaped back up at the opposite side of the greenhouse and so creating airflow right the way through the internal area.

Not to scale:

[Adrian]

Thanks for the explanation, you have a big greenhouse then if the pipe is 15 foot long.
I was thinking small like my 8x6 that I heat.

[tropicalwon]

They are just bog standard inline extractor fans Ade, they pull the air straight down a 4" duct pipe then a 90 degree angle takes it across the length of the greenhouse at a depth of 3ft.

This 15ft long pipe at the base of the gravel has lots of small holes drilled along the top where warm air escapes into the gravel pit. There's then another 90 degree angle that joins a pipe to bring the air that hasn't escaped back up at the opposite side of the greenhouse and so creating airflow right the way through the internal area.

Not to scale:

Great idea and diagram .............
It's like the solar panel, 12v battery & fan incorporated in 4" pipe method .(Link provides diagram of setup)
This can also be adapted into your arrangement

http://www.reuk.co.uk/OtherImages/green ... system.jpg

[GoggleboxUK]

That's the diagram I based the concept on TW, I was going to use computer fans and a solar panel but, as I wanted electric running to the greenhouse for heaters, I decided to go the extractor route.

Ade, my internal space is 15 x 4 ft so only slightly bigger than your 8x6

[tropicalwon]

That's the diagram I based the concept on TW, I was going to use computer fans and a solar panel but, as I wanted electric running to the greenhouse for heaters, I decided to go the extractor route.

[GREVILLE]

Can certainly see the logic in this arrangement.

Back in the 1980's a friend of mine in the States was promoting bungalow structures built with insulated concrete bedded on a deep foundation of uninsulated concrete full of air ducts opening inside the home. A thermostatically controlled heating arrangement would heat up this underfloor heat sink with fans gently circulating the air from the ducts into the home, in effect a giant storage radiator brick.

The process was reversed in summer as, without the heat, the fans would encourage the cooled down concrete below ground to blow in cooler air through the ducts. The result would be cheaper heating and air-conditioning bills.

The idea did work in the few homes that were built this way but was never a success as no one had a taste for the concrete structures needed for this to work.

Should work well, in theory, but you might need to build another 15 foot house heated conventionally to make a comparison to see off any scoffers

[Dave Brown]

This might also be interesting to those looking to passively heat http://www.hardytropicals.co.uk/forum/v ... 97&p=76588

[Kristen]

How did the heat store perform over the Winter GB?

Did it only give you benefit in Autumn / Spring? or better/worse than that?

[GoggleboxUK]

It was tricky to tell really seeing as we had such a very mild winter here.

Saying that, I had the heater set to frost free and, according to the electricity consumption figures, there must not have been many occasions where it actually kicked in because, considering the fans run on electricity, there was barely a difference from the year before over that quarter.

I think perhaps the cold spring, and the warm consitions in there, may have led to a bit of rot in the Ensetes and such plants as there were some high temperatures in there and that led to me watering when perhaps I shouldn't given that we had a cold spell after it.

My overall conclusion is that it HAS worked although I think I need a proper winter to get any real usuable data back to analyse the effectiveness.

Not that I'm in any rush for a real winter.

[Kristen]

Thanks GB