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Comment by ZeroGravitas | Hacker News Reader

One of the most amazing triumphs/failures of capitalism, is the ability to fend off competitors with even a mildly long payback period for decades.

It boggles my mind that modern democracies like Germany or the UK could have ignored heat pumps for so long.

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Because it isn't mildly long. It's either very long or infinite, anywhere where gas is ~ 1/3 the cost of electricity per kWh. COP of 3 at a 3:1 price ratio for electricity to gas = 1.

Which itself makes sense if you use gas as the RELIABLE source of kWh. You need to burn ~ 3kWh of primary energy in gas to deliver 1 kWh to the household, so 3:1 makes sense, and the RELIABLE source of kWh is the price setter because a failure of the grid is literally an existential crisis, something the "agile" private sector companies aren't liable for.

An auxiliary annoyance in the UK is that reversible pumps aren't renewable for government grants. This is ostensibly to discourage aircon, but rather silly, since there are few easier green power problems today than "satisfy a demand that is almost perfectly correlated with high insolation".

FYI as a type the largest suppliers are gas, solar, then nuclear - of which nearly half is being pulled from France, an amount that for some reason isn't always counted by some people.

In many EU countries that cost difference is a policy failure:

> Italy, Spain, the United Kingdom, Belgium and Germany. All five countries overtax electricity — in three cases by more than 200% — and undertax oil and fossil gas while not taxing wood use at all. Only in Italy is the tax rate on heating oil close to the value of the environmental costs caused by its use.

https://www.raponline.org/knowledge-center/aligning-heating-...

But going from first principles Renewable Energy Without the Hot Air could run the numbers back when it was written in 2008 and show this was a good move: https://www.withouthotair.com/c21/page_151.shtml

> Let me spell this out. Heat pumps are superior in efficiency to condensing boilers, even if the heat pumps are powered by electricity from a power station burning natural gas.

> you need to burn ~3kWh of primary energy in gas to deliver 1 kWh to the household

Is that so? I thought electric generation from natural gas was at least 80% efficient - and transmission losses maybe can pull that as far down as 66% - but not down to 1/3.

I think they are referring to the COP of a heat pump as at least 3, whereas natural gas appliances by definition must be below 1.

A large percentage of homes in the UK are not and cannot reasonably be insulated well enough for heat pumps to work.

I don't quite understand why I can't just run a heat pump 2-3x more powerful, but apparently that's not the done thing.

This would be more convincing a reason if the new builds over the last couple of decades had been fitted with good insulation and heat pumps.

Since they dragged their heels on that low hanging fruit, I'll suggest they've not really even tried to make it work elsewhere.

(There have been some improvements so I don't want to get carried away, but there's also estimates of many Billions wasted by not doing what was obviously a good idea at the time).

Also, recent real world experience suggests more older buildings than you think will work. Britain doesn't get that cold for that long and modern heatpumps and insulation techniques are pretty good.

The problem lies in the radiators. Heat pumps can not "lift" the temperature more than 30-40 degrees Celsius without getting inefficient. So at -5°C outside, you can only warm water up to 35°C. At this temperature, your old radiator doesn't transfer enough energy from the 35°C warm water to the 20°C room. You would need to either heavily insulate your house or replace the radiators.

Can you elaborate on the insulation part? My understanding is that if you have a poorly insulated house you just need more heat energy to keep it warm, I.e. a larger heat pump.

That's my logical understanding as well. I'm wondering whether it just ends up being significantly more expensive than gas heating so no-one talks about it.

A heat pump is much more effective if you only have a small temperature difference [0]. If your house is well insulated and you have underfloor heating, you can heat your house with 40°C (sorry for European units) water to keep it warm inside. If you have poor insulation and small heating elements, you need much hotter water (>60°C).

A heat pump can have a carnot efficiency (theoretically achievable efficiency) of >10 to warm water from 20 to 40 degrees, but only ~5 if you have to heat it from 20 to 60 degrees (not sure about the numbers, but you get the idea).

[0]: https://energyeducation.ca/encyclopedia/Carnot_efficiency

> it just ends up being significantly more expensive than gas heating

Bingo.

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