Heated polytunnel

[JMCKG]

There is a proposal to heat our community polytunnel over the winter, keeping the internal temperature at 7C. What could we grow that we cannot at present?

[Bacchus]

The problem is not solely heat but also light. Will you also have growlights?

[JMCKG]

The problem is not solely heat but also light. Will you also have growlights?

No growlights will be fitted. The average temperature for our area is 5c during the winter months. I just don’t see any advantage in spending money on this, even if we manage to get say 10c average, what difference will it make to what we can grow?

[Deano's "Diggin It"]

The 10c temperature would be ideal if you could sustain it, and would allow you to grow a multitude of sins!

But like Bac as said, light levels need to be included!

So yeah! Like yourself! Think this is a "No Brainer"

[veggiechicken]

What is the community polytunnel used for now, during winter?
Average temp of 5C is, presumably, not night temperatures? That's when the damage is done!

[JMCKG]

Not used very much during winter. Some store geraniums etc. I grow winter onions, some grow xmas potatoes. That’s about it.
5C is average from October to March, so yes will mostly be lower during night.
Got to say my winter onions outside look better at moment, could be due to more light ?

[4Shoes]

How big is the polytunnel? Does it have side vents? Is it well sealed?

Perhaps heat a smaller area or build a mini polytunnel is the answer

Would a 3kw heater make much of a difference?

3kw typical running costs here (6hrs / day)
https://www.sust-it.net/heating-energy-calculator.php

[JMCKG]

How big is the polytunnel? Does it have side vents? Is it well sealed?

Perhaps heat a smaller area or build a mini polytunnel is the answer

Would a 3kw heater make much of a difference?

3kw typical running costs here (6hrs / day)
https://www.sust-it.net/heating-energy-calculator.php

It’s 30ft x 12ft Firts Polytunnel. There’s is no electricity on site, proposal is 1kw wind turbine. I think it’s a waste of time and money raising the temperature by 2-3C, just looking for facts.
What can we grow at 8-9C that cannot be grown at 5C in the winter. I know about lack of light but our committee don’t seem to have taken that into account.

[sandfields]

Given a capacity factor of 25% - 40% for domestic scale turbines, the idea of running a 3Kw heater with a 1 Kw turbine sounds about the reverse of what's possible. Even then you'd need some pretty expensive storage facilities. Wouldn't you be better off with propane, and using the electricity for some led lighting?

Mind you, a massive great hot bed wouldn't be a bad idea, as done by Sara Backmo https://www.youtube.com/watch?v=k3O-cGHXc78

Looks a good communal project too.

[4Shoes]

It’s 30ft x 12ft Firts Polytunnel. There’s is no electricity on site, proposal is 1kw wind turbine. I think it’s a waste of time and money raising the temperature by 2-3C, just looking for facts.
What can we grow at 8-9C that cannot be grown at 5C in the winter. I know about lack of light but our committee don’t seem to have taken that into account.

Ok a 12 x 30 has an area of 360 sq feet.... if it is 8' high, it would take a 1kw heater 17.8 minutes with no heat loss to increase temperature by 10 Deg C. or 9 mins for 5 Dec C.

The Wind turbine will need to be lower then 10m to get round planning and any trees or tall buildings will reduce amount of power generated. Then you need a battery pack and an inverter or 12V heaters to make use of the power
.

Everything is possible, but it is a cost\benefit\Effort Triangle

Have not looked at the video, but a big hot bed with mini pollytunnel cover may give similar benefits, and could be made from some blue pipe, pallets, fresh horse muck and plastic

[JMCKG]

Thanks for all the replies. Glad to say the proposal will not be going ahead, Council have refused planning permission.