[cgufus]

I'm not sure I understand the principle.

A heat pump achieves a COP (coefficient of performance) of approx. 3-4 (e.g. by investing 1 kWh of electricity, a heat pump generates 3-4 kWh of heat by extracting from the surroundings, air or sole, 2-3 kWh). In this example, by pre-heating the air, you supply the heat pump with ~0.9 kWh of thermal energy (the miner will convert 900 watt directly to heat I would assume). So instead of 1 kWh of electricity consumption from the heatpump, you have 1 kWh of electricity for the heat pump, plus 0.9 kWh for the mining, and you end up with a bit more than 3-4 kWh (since the COP of a heat pump increases if the source temperature is higher).

So in a nuthsell: before: in 1 kWh, out 3-4 kWh after: in 1.9 kWh, out 3.5 - 4.5 kWh

so you lose 0.4 kWh?

[shoo_pl]

On principle, yes. There are quirks - the COP is different for lower temperatures, and becomes 1:1 at around 5F (-15C). So preheating the air could improve the effectiveness at low temperatures, and I am guessing it might look like this:

- before: 1kWh in, 1kWh out - after: 1.9kWh in, > 1.9kWh out

However, if it was that simple, I suppose heat pump manufactures would include a pre-heating as built-in feature.

It's very likely that he reduced the energy consumption of heat pump by 50%, but at the same time he uses more than those 50% for mining and has a negative total result that is being offset by the profit from mining itself. Which probably nice for him, but not really for environment :)

[throw0101a]

> There are quirks - the COP is different for lower temperatures, and becomes 1:1 at around 5F (-15C).

It depends on the unit. Some (Mitsubishi FE12NA) have a COP of 1.75 even at -10F / -20C. See Table 6:

* https://www.nrel.gov/docs/fy11osti/52175.pdf

[cgufus]

The used coolant mainly infleunces these numbers.

check chart on: https://www.researchgate.net/figure/Coefficient-of-performan...

[bdcs]

IIRC my thermodynamics classes correctly, the heater would be optimally placed on the hot effluent out of the heat exchanger (HE) going into the house. This is because the COP is improved (similarly to heating the cold side) because the hot side of the HE doesn't need to be as hot to get to the same T, but also the HE doesn't need to move the heat through it, increasing efficiency. (COP decreases with increasing heat flux [Q] in practice.) For well-mixed air in a house (a poor assumption), this is the same as throwing the miners in a closet. I would suggest to the author to move the miners to the hot side the HE going into the house's rooms. Simulation or measurements (over the course of a week, not just instantaneous measurements) would be helpful here .

If I were a HVAC company with WiFi thermostats, I would look into including miners in heating solutions.

[elgaard]

Heat pumps have thermostats so they do not run at max all the time.

So if the heat pump without the miner use 1 kW to heat to room temperature it would need less than 1 kW with the miner to heat to the same room temperature. Plus as you say the COP increases.

So it could be that 5 degC to 22 degC requires 3 kW but the heat pump can do it with 1 kW (COP=3).

The miner use 0.9 kW to heat the the outside air to 11 degC. It would take 2.1 Kw to heat from that to 22 degC. But the heat pump now has a COP of 4 so it can do it with 0.5 kW.

So you lose 0.4 kW but gain bitcoins.

Or you could say that you get 2.25 as many BTC for the same electricity cost.