The hunt for the most efficient heat pump in the world

A new generation of engineers has realized they can push heat pumps to the limit.

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[Haravikk]

A lot of British installations use an outdoor air coil and an indoor water (or water/glycol) filled buffer tank, then circulate warm water through the house's existing radiators. The most common complaint I see about these is that, because water is circulating at perhaps 35°C instead of the 50-70°C of a flame-fired system, you get a lot less heat per unit surface area of radiator in the house..... thus, you either end up with cold rooms, or else you need to replace the radiators with better ones. Other than that, they seem to work very well.

There have been a lot of advances in heat-pumps able to deliver hotter temperatures, which these COP 5+ units might be capable of? I'm hoping so, as we desperately need efficient units that can deliver higher temperatures for this to be truly viable in the UK.

That's because the other big issue in UK housing is how shit our insulation typically is, as well as a lot of housing stock having flat roofs that can only comfortably fit two or three inches of insulation (allowing for an air gap), which makes for pretty poor heat retention. Not to mention flat roofs being an absolutely insane idea in a country that's raining 90% of the time, yet we're still f'ing building them.

I know for my own home, my current gas boiler targets a 55ºC return temperature (heat of the water returning to the boiler through the radiator loop) so it heats at around 60-65ºC, and a lot of newer gas boilers in the UK do the same. But with the amount of insulation in my house that's only just enough to get it to a comfortable (19-20ºC or so) temperature throughout. And that's after I've added extra insulation everywhere that it's possible to (under the cladding, extra loft insulation, cavities etc. etc.). Only options we have left would be insulation under the ground floor, or deepening the wall and roof cavities somehow, but each of these is quoted well above my price range because the foundations and floors are difficult for various reasons (so ground floor insulation that might only be a couple of grand quickly becomes way more), and deepening the wall and roof cavities are both extremely difficult as well.

If a heat pump can deliver a similar temperature of water for heating though, that might be good enough? Tough to say – the UK has been building shit houses for 50+ years, and even new housing is pretty pathetic, as one the first thing the Tories did when they got into power in 2010 was rip up massive chunks of the building regulations. They gave the usual BS about rules stifling competition, even though if everyone is required to build to a higher standard of insulation then there's no way for it to harm competition, whereas (funnily enough) getting rid of the rule makes it really hard for manufacturers of well-insulated homes to compete since they can't compete on price against cheaply made prefab boxes with paper thin walls.

Going to be interesting to see if a Labour government will do a better job but I'm not holding my breath at the moment (despite very much wanting the Tories out) as they've gone out of their way to avoid pledging any really large sums in investment into anything, they're still showing what looks like an austerity platform. And that's how we end up with houses from the 2020's having exactly the same problems as ones from the 70's like mine.

/rant

 

[Haravikk]

I don't have any experience with A2W systems, but the hotter you need the water, the lower the efficiency, and if you need to pump hot water through radiators designed for Nat Gas heated water (55C?), I can see issues. [...] A passive radiator sitting at 30C doesn't do much.

Yeah, this is why the woeful state of home insulation in the UK is such a concern; 30-35ºC radiators should work fine in a very well insulated home, where the goal is to maintain a steady temperature, but in most UK homes you'll be losing that heat faster than it can build up. I know mine will, as 55-60ºC in the radiators seems to be about the minimum that can keep my house comfortable (particularly in windy weather, rather than cold specifically, but good luck figuring out why!).

This is why we have groups like Insulate Britain glueing themselves to roads and shit, but instead of accepting that people don't generally want to glue themselves to roads, so maybe they have a point worth acknowledging, we've had successive governments trying to have them classified as terrorists – because people who want governments to solve problems and invest in the future are definitely equivalent to people who want to mass murder other people.

I live in Scotland so I alternate pretty hard between wanting to fix these problems thanks to my natural democratic socialist inclinations, to either being tempted by independence (despite knowing it'll be a disaster that will do nothing to help) or burning everything to the ground when my more nihilist side comes out.