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Why does no one seem to use peltier elements to heat small greenhouses? (feddit.org)

submitted 1 week ago* (last edited 1 week ago) by viertesauge@feddit.org to c/gardening@lemmy.world

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Genuine question. When I look up options for heating greenhouses its either propane, kerosene or electricity. So if you dont want to use fossil energy for any reason, why not use peltier elements which would boil down to resistive heating and moving heat from the outside to the inside?

Is it because they dont last in the weather? Or because they require a DC source? (couldnt you simply move the PSU inside the greenhouse and use any conversion losses as additional heating?) Or maybe its because you would have to possibly cut a hole in your greenhouse walls so that the peltiers cold side is actually on the outside?

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[+] plantfanatic@sh.itjust.works -6 points 1 week ago* (last edited 1 week ago) (2 children)

No, you’re using 100w to move 100w. You can’t ever have more efficiency than you put in.

What would you be cooling to get the heat? If it’s cold outside at night, there’s nothing go take heat from either. You would need a way to store it during the hot day.

[–] viertesauge@feddit.org 9 points 1 week ago

its a heatpump, of couse I will have more Watts in heat on one side than i put in as electricity

[–] bizarroland@lemmy.world 6 points 1 week ago* (last edited 1 week ago)

This is not correct.

Heat pumps are capable of being more than "100% efficient" because they are tapping into an external heat source, the electricity that is being used to operate the device is not the entire sum of the energy available to the device.

Once you step out to the greater picture of the electricity + the available environmental energy, then it returns to equilibrium, but when you're only calculating wattage and the electricity required to operate it, then you can get up to four times the amount of heat output per watt of electricity used with a properly designed system compared to a resistive element.