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Hello guys,
In your expert opionins, could an ASHP be used to heat a greenhouse? The one in question was previously connected to an oil boiler, this fed two 4" steel pipes which run the entire length of the greenhouse (approx 25meters!!) and then return on themselves and go back to the boiler ( reduced to 1.1/2 tappings)
Would an ASHP be man enough!?? Im thinking of the volume of water in these pipes must be massive!
Thoughts!???
Like any heat source or cooling source, to be effective, they need to be sized to match the heat loss or gain.
If you can provide us with the amount of heat loss from the greenhouse (kW) at the worst outdoor winter conditions, then we might be able to answer your question.
There is a lot of science to this business but not a lot of guessing. To be of any help to you we need information to work with.
Do you have access to anyone that can provide some numbers?
ASHP's can be connected in tandem to provide varying duties so it just might be possible. 4" pipes sound like a big system though
Any idea what the duty of the oil boiler was?
Afraid not, the oil boiler was removed many years ago!
My calculations suggest there is approx 800 litres of water to be heated in 100 meters of 4" pipework!?? Does this sound right, or have i messed up there!?
The heat loss of a greenhouse, where does one start with u values on that!??
Volume of water or size of piping is not the issue. Its the temperature of the water thats critical. If these 4" pipes are currently carrying 60-70C water then you will never match that duty with an ASHP. Your heat emitter would need to be much larger and work at a lower temp.Quote:
Originally Posted by pentium
You'd need to find the U value of the glass, the indoor temp you expect and the minimum outdoor temp.Quote:
Originally Posted by pentium
Tbh unless you have scope to fit a ufh system to this greenhouse then this would be a non runner imo. You can't put more heat emitters at height as this will restrict sunlight, so heating from the bottom up with the storage a screed would provide is the only way this will work.
We designed something like this for mushroom tunnels a few years back, the project didn't progress, but that was how we had planned on doing it
I suppose one question is, how hot do you want this greenhouse?
OK, look on the ends of the piping and see if there are any steam traps present. Many many systems in old green houses did use steam to keep the piping to a minimum so if this is/was the case you could be looking at replacing 100-105C heating temps. Some were changed from the steam to high temp water and there might be some evidence of the change.
K value of glass is 1.05 W/mC
"U" value of typical single glazing with metal frames, approx 20% framing could easily be between 5.0 and 6.7 W/m2C in severe conditions. Standard glass is 6 mmm I think where as greenhouse glass is 4mm.
Gives some idea for a rough calc.
Q = area x U x dt
Then there will be the vent rate to consider which could be quite high.
Question to ask is the heating required for frost protection during cold spells or to be a heated house for growing exotics etc.
Is a green house not the same as a conservatory:D:D:D
I have an excel spreadsheet for a heat load calculation for green houses..Can i attach it somehow, i have tried but nothing happened
So long as it is not above the forum limits for attachments, Just reply to a post and then scroll down to 'Manage Attachments'Quote:
Originally Posted by MilosBog
Don have an idea ...it just refuses to attach the file..
in Short, homogeneous losses are standard U*DT*A and than this value must be multiplied with some correction factors . One factor is F1=1.12 and i dont have an idea what is about, the Buderus guys have told me. The second factor is F2=1/111662.531*Atot+0.8560445 .
So than we have a transmision heat loss
Qtr=F1*F2*U*DT*A.
Infiltration losses-how many air is to be changed and some values are here
Construction SystemAir Exchanges/ Hour 1.
New construction, glass or fiberglass 0.75 to 1.5 2.
New construction, double layer PE 0.50 to 1.0 3.
Old construcyion, glass, good maintenance 1.00 to 2.0 4.
Old construction, glass, poor condition 2.00 to 4.0
The total loads are sum of infiltration loads and transmission.
Maybe if the water content is enough,sufficient amount of energy can be stored..Please check firstly the load, and next what could be done. In my case i have had a problem with the soil, the constant soil temperature had to be maintained so PEX pipes where installed. Than the heat output was non constant due to the moisture of the soil.....
Yeah this could be done with an air source heat pump but like all of the other posts the capacity required and the flow temp for design is required. The main problem with the site would be that the power supply is most likely not going to be big enough.
Have you thought about a Rotex solar boiler to take advantage of the solar gain during the day? How much power is on site?
The majority of plants grown in greenhouses thrive best at temperatures between 50 and 85 degrees Fahrenheit. Depending on the style, geographic location and desired interior atmosphere of the greenhouse
Some other things to consider
Insulating a greenhouse is simple.Adding insulation to a greenhouse is an inexpensive way to help maintain a steady temperature throughout the year; insulation becomes especially important in winter, when heating a greenhouse can become very costly. Use bubble wrap and silver-lined insulation to get the best results when insulating the interior portion of your greenhouse. Put insulation around the exterior portion of the greenhouse to add extra warmth to the building and help give it a constant temperature, no matter what the season.You can also tape bubble wrap to windows in addition, I found this study at
http://cat.inist.fr/?aModele=afficheN&cpsidt=15780008
.