The 'exploding' demand for giant heat pumps | Hacker News Reader

The 'exploding' demand for giant heat pumps

bbc.co.uk

15 pointsmoreati17 comments

TIL "district heating" (a heat distribution system) is a thing. It does make sense to use waste heat from industrial processes to heat homes.

I'm not a thermodynamics expert, but I think you probably need some density of heat sinks so it only really works in cities.

I wonder if in the summer, it could work in reverse? I speculate there are two options for summer operation: (a) a centralized AC plant sends cold fluid into the pipes, or (b) a decentralized AC heats hot fluid.

With option (a) I suppose it's not very backward compatible with a heat-only system, if you have a bunch of customers who built their factory expecting "this pipe will always be hot" they might have a bad time if you make it cold half the year. With option (b) it's more backward compatible but I think customers might not like it. I'm pretty sure AC gets less efficient based on temperature gradient so pumping AC into a heat transportation pipe would be more expensive for customers (electricity, wear-and tear on AC, takes longer to get to the commanded temperature when you reduce the set-point). So you'd have an incentive to unhook your AC from the system and just send heat into the air instead.

The newer generations also do cooling, via two pipes, some details here:

https://5gdhc.eu/5gdhc-in-short/

As far as I know something similar is used in Finland, but not with the industrial processes.

Some apartments dig a deep hole into the ground, and pump the heat up during the winter, pump the heat down during the summer.

maalämpöpumppu

That kind of service is starting to be provided. As a separate network, mostly for office buildings. Not having to build or maintain AC can be cheaper and waste heat can be centrally moved to heating or even storage. As during summer you still need quite hot water from faucets.

The article seems a bit obsessed with the size of individual units.

Latest generation district heating systems distribute the heat pumps around the system for greater efficiency.

Big units might be the simple option for upgrading older systems from fossil fuels but they can probably do better with a little planning.

The Vienna system they are talking about specifically needs to concentrate the heat pumps at the source of the waste water. I read some article about it in the local news and it was a ridiculously small investment for the amount of households it will serve. Because the waste water contains so much heat it will be a very cheap heat source operationally. I was actually shocked they’d rather burn gas given that is possible but either it just recently became so lucrative with higher COP or Putin just paid off too many people. I think half of Austrias ex politicians worked for some Russian entity or another before the Ukraine war

A couple of figures that seem sorely missing from this article: what's the COP (coefficient of performance) of these heat pumps? And they talk of some temperature rise, but what's the temperature drop in the water they're going to dump back into the sea or into the river?

Without these it's impossible to understand the environmental viability of these projects when compared to fossil fuels.

So are these a significant improvement or just PR pieces for the suppliers? Give us the figures!

I'm curious about the environmental effects of harvesting heat from the environment. Given that hurricanes are driven by extreme sea surface energy, it would stand to reason that harvesting enormous amounts of excess energy in natural systems across a large enough area would be useful. Harvesting in too localized of an area could cause ecological problems.

All the heat that is taken by heat pump from the environment, is returned as waste heat/leaks nearby. In case of district heating, it's 10 kilometers away at most. That isn't going to affect balance of anything much.

I think it's a valid cavil; you take heat from the sea but emit it to the ground and atmosphere. The respective deltas may or may not be negligible.

So far, we were noticeably heating the oceans up and this should stop.

The main advantage of these systems is that they can be used for cooling too.

The main disadvantages are that they require enormous amounts of co-ordination socially and you pretty much have to run the 24/7 (and then store heat which is wasteful). You also need a heat source (normally a large body of water) nearby.

District heating infrastructure can't be used for cooling without upgrade. But that's a solvable technical problem.

Having high density housing with proper social co-ordination involved is not a bad thing. That it has to be run 24/7 means it can be more efficient that something that turns on/off all the time. Also, large thermal storage is much cheaper than many small ones and allows to better leverage changing electricity supply from renewables.

The problem is it will HAVE to run 24/7.

I like the idea of social co-ordination, but these days it is incredibly hard to actually do. :(

That varies with culture. District heating is more common in Europe than America.

I sometimes think of the USA as a machine for converting noble ideals into intractable problems.

>In this installation, the heat pumps' CO2 refrigerant will absorb a small amount of heat from seawater. Compressors boost the temperature of the CO2 and the system can then transfer this heat,

accurate reporting , as ever , from the BBC

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