Heat pumps outsold gas furnaces in 2023 | Hacker News Reader

Heat pumps outsold gas furnaces in 2023

distilled.earth

38 pointsjseliger11 comments

Crazy idea: gas powered heat pump. Instead of just burning gas right into a heat exchanger as a furnace does, it burns it in an engine which turns the heat pump compressor. The house receives all of the heat transferred by the pump as well as the exhaust heat.

It's essentially the same thing that would be happening if you had a grid burning natural gas for electricity powering an electric heat pump, only it all happens locally and the exhaust heat is utilized. It's also similar to a "micro combined heat and power" system, with the power going directly into a heat pump.

EDIT: just discovered there's a smarter/simpler way to make a gas-powered heat pump: https://www.energy.gov/energysaver/absorption-heat-pumps.

The point is to get away from gas, you do the opposite with a gas powered heat pump. Sure you'll have gas peakers for the foreseeable future but that's very different from a gas line into every home.

The point is not to get away from gas.

One point is to use energy efficiently.

Cogeneration facilities convert gas to electricity fairly efficiently, and then a heat pump is several x more efficient than just burning the gas in your home.

Also there is cost, which can be less with a heat pump.

Tax the pollution and let The Hand sort it out

Grid scale CCGT are way more efficient than small gas heaters. And you don't have to do gas distribution.

https://en.m.wikipedia.org/wiki/Combined_cycle_power_plant

I doubt we'll ever see numbers like this for water heaters even with the 30% tax credit until manufacturers catch up to seemingly the only company that figured out how to make them not suck https://www.intellihot.com. Like it's so simple it's infuriating they basically don't exist.

All it is is a regular air heat pump but instead of heating a tank of water it heats a tank of water/glycol mix which can store a lot more energy. The heat is then transferred to the water in your pipes via a heat exchanger. It's not technically infinite hot water like electric/gas tankless but it seems really hard to run out.

Glycol has a much lower heat capacity than water, I don't get why adding that to water would increase the capacity to store energy? It's usually added as an anti-freezing agent to protect the pipes or to prevent fouling

They probably run it very hot since the computer controller can prevent scalding.

If the glycol elevates the boiling point, you could store energy above 100 C. The human-safe temperatures on a normal water heater must be closer to 50 or 60 C. Room temperature is about 20? I imagine if you more than double your temperature difference, you might more than quadruple your energy storage, that might offset the lower heat capacity of the glycol.

Sort of like high-voltage power lines being able to use thinner wires but requiring thicker insulation (meters of air) so they don't kill anyone.

User 15457345234 pointed out that you could just pressurize the water. But building a steam pressure vessel requires a weight-safety tradeoff. Maybe a mixture that boils hotter is cheaper overall than safely containing steam pressure.

That's a good point I hadn't even thought about it. It seems the property they want is the higher boiling point but I don't know enough about heat storage to know why they consider that a win compared to pure water.

A glycol/water mix is almost always chosen primarily because of the anticorrosion purposes and freezing point alteration.

If you have a racing car you run pure water with a bit of 'wetter' (a surfactant) in the cooling system as it gives you the highest thermal capacity / cm^3 ratio. If you want to increase the boiling point (to run a smaller heat exchanger) that's most trivially achieved through pressurisation.

Hmm I wonder too. Most energy storage systems store a lot of energy when a phase change is involved. for instance ice at 32F -> water 32F is 80 calories.

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