What are the actual impediments to this no-brainer?
https://www.theguardian.com/environment/2023/feb/23/recapturing-excess-heat-could-power-most-of-europe-say-experts

Political, sure, but technically it's that waste heat, no matter how 'much' there is of it, is no use unless its temperature is high enough at the point of delivery to its re-use location.

What role for heat pumps in uplifting that temp a little, rather than uplifting the temp of stone-cold natural/environmental sources by a lot more?
Even re-using waste heat another time again, with modest heat-pump augmentation?

No use should be supplied with heat hotter than necessary, and that includes fossil fuel that burns very hot (e.g. CH boiler) only to supply a tepid heat requirement (CH rads). All that re-use potential squandered.

The impediment is the UK's cultural aversion to district heating. It's common in far Northern lands such as Sweden, Denmark and Aberdeenshire.

Its interesting that the proposed sources of waste heat are now from supermarket fridges and the aircon in IT companies - in the past, people thought about waste heat from power station cooling towers and factory chimneys, which tend to be far from people's homes.

The Aberdeen district heat operator found that residential heat is mainly needed in the evenings, the network is difficult to balance the rest of the day. They have connected up some schools and swimming pools to spread the load out across the day.

Same timing problem would apply for pumping heat from offices and shops into homes, and also winter/summer heating/aircon balance. It is possible to store heat in tanks of water or even underground, but that means more ⁰C of heat pumping needed.

The enabler for the Aberdeen system was groups of large tower blocks of flats owned by a single landlord (the council), each block already had a hot water heating system, it just took some pipes under the road to join them together and that was the nucleus of the system. IDK if ownership is different in other places.

I like interseasonal storage, and yes it is going well apart from being completely ignored. Surprising that it works when they have-30C every winter and yet manage to heat using stored solar energy

It must be possible to make it work here too.

Posted By: WillInAberdeenIronically the Alberta scheme is using fresh, use-once-and-discard, high-exergy solar photons, whereas the Aberdeen scheme is reusing low-temperature waste heat that was already used by CHP generators. But the Alberta scheme is absolutely zero carbon, whereas the Aberdeen scheme involves burning gas in CHP generators which would otherwise not be running. So which is the greenest approach?

That's a rhetorical question, no? Obviously a gas-powered anything is the wrong appoach.

How much would the quantity of waste heat be reduced if insulation and processes were improved?
Would it not be far more economical to capture the waste heat and use it at its source? (Rather than incur the capital costs of transferring it)
If it is used for domestic consumers , does the cost of transferring this waste heat outweigh its worth? Surely better to use the capital expenditure to insulate homes properly.
What happens when the provision of this heat is interrupted, heating systems designed for higher input temps struggle or have to be overspecced in the first place.
Where as a consumer can choose how they maintain/repair their own heating system this ability is lost when you’re reliant on district schemes, which with their “management costs” and need to satisfy all demands the scheme owners are either expensive or scimp and eventually go awry. The social housing schemes with district heating systems that have failed due to insufficient reserves to renew systems when the time comes and how do you provide energy for the shutdowns etc.?

Posted By: WillInAberdeenA related example: the Aberdeen heat network is connecting into the municipal waste incinerator plant. Some people argue it will be good to recycle waste into heat for homes. Other people argue it is good not to produce so much waste in the first place, and monetising it as heat is an incentive to just carry on wasting stuff.

Incinerating waste seems like the best of a bunch of bad solutions to the waste problem at the moment, so making use of the heat it generates is a good idea - some schemes use it to generate electricity I believe. (e.g. https://www.suffolkrecycling.org.uk/learning-zone/where-rubbish-goes ) Whether that is better or worse than using it to heat homes I suppose depends on the area (what do they do with the heat in summer?). If making use of the heat generates incentives to create more waste then those incentive schemes are set up wrong and need to be changed.

Posted By: fostertomNo use should be supplied with heat hotter than necessary, and that includes fossil fuel that burns very hot (e.g. CH boiler) only to supply a tepid heat requirement (CH rads). All that re-use potential squandered.

Posted By: WillInAberdeenIronically the Alberta scheme is using fresh, use-once-and-discard, high-exergy solar photons

Yes, with as-delivered 'temperature' of zillions of degrees K! And trust you to term it 'exergy'. We can say same of electricity delivered as fuel - is capable of being transformed to heat at any high or low temperature you like. I guess my statement applies to energy delivered as heat.

I agree with Tom's direction of travel that the Alberta photons could have been used to make PV electricity, which has many potential uses, hence very high exergy (or low, depending on your sign convention). That PV could (eg) be used to run one of those fusion experiments that generate zillions of degrees K. Which the waste heat from CHP could not. So a lot of exergy is wasted by using ST or PV for space heating, instead of using waste heat or ambient heat.

I agree with DJH's direction of travel that using solar thermal is greener than propping up gas-fired generators by selling their waste heat (the fallacy of recycling). There are plenty of solar photons to go round.

Exergy is loosely defined as the "usefulness" of a source of energy, eg a kWh of electricity has more uses than a kWh of lukewarm water. "Usefulness" requires a value judgement about what is "useful" to you. The scientific definition of exergy is based on ability to do work (eg lift heavy weights etc) but we might feel it is more useful to have warm homes without climate change.

Edit: the OP article got confused between the amount of waste heat available (its energy) and its usefulness (exergy) eg "London’s excess heat equated to 9.5 TWh a year, roughly the amount of heat required to heat 790,000 households". In reality, most of London's waste heat is emitted as slightly warmed air, which is useless for heating households.

Posted By: WillInAberdeena lot of exergy is wasted by using ST or PV for space heating, instead of using waste heat or ambient heat

Yes that's it - I'm a bit rusty, prob 10yrs since my need to learn about this.

Posted By: djhas exemplified by Drake Landing, heat pumps can make it useful

DL does that? V little talk of this. Think of it as a better 'free' heat source to pump up from, that any of the big3 'natural' or environmental pumpable heat sinks, air-source, water or ground-source.

No heatpumps at DL, is why they need to collect fresh unused high-exergy photons to get their store up to 70⁰C + in the summer, with the thermal losses that entails.

That's also the problem with waste heat - it needs to be transported from source to consumer, and stored to match supply time to demand. Both of which need high-ish temperatures, so more thermal losses, and/or poorer heatpump CoPs, and/or.the waste heat isn't hot enough to be useful.

DL could perhaps get the same effect by using PV to collect those photons, to power a heatpump to put some summer ambient heat into a store at say 40⁰C, then in the winter they could heatpump from that up to 70⁰ for distribution. Or make their fortunes using their electricity to power server farms and pizza ovens in their basements, with free waste heat as well. Or they could just run individual heatpumps per house through the winter. Many horses, and lots of courses.



There is less need for interseasonal electricity storage, as the main consumers are emerging as electrified transport and industry, which are not seasonal like heating is. Likewise, PV and wind naturally cover each other's off-season. Storage is mainly needed within-day, and for a few weeks of anticyclones.


Just popping back to the sunlight temperature thing - it turns out it doesn't matter whether sunlight is at 5k⁰C , or 1 zillion ⁰C . The Carnot efficiency of extracting work from either of those temperatures, is fairly close to 100%. So sunlight can be turned into electricity to make fusion-temperature plasma, theoretically with minimal waste. And without upsetting the 2nd Law, which was bothering me earlier. Whereas most waste heat has Carnot efficiencies ~10%, so isnt useful for work.

It's the temperature 'swing' that determines deltaT/size/capacity. Looks like DL heat their store to about 70⁰C and draw it back down to 50⁰C again each year, can't go any colder or hotter as no heatpump. So DeltaT=20⁰C worth of capacity.

Alternative would be to heat it to 40⁰C and draw it back down to 20⁰C by heatpump -> same storage capacity but with less thermal losses. Or go even hotter and colder to achieve same capacity with fewer boreholes, but worse CoP. Horses courses etc.