Any one considered an Acoustic Heat Pump? The two brands that I am aware off are
AIUI these pumps are more effective than the heat pumps that are available at the moment and they can generate hotter water.
Very interesting, but I couldn’t see any actual quoted COP or SCOPs, just claims that they were superior.
Tim
I read an article in the printed Telegraph a few days ago. This is something similar I have just found but still no COP:
It sounds interesting, but to note that high temperature hot water heat pumps are already available and well used in Japan under the name EcoCute. However the problem is throttling them *down*. When you're heating water you always want it at 60C (or more, they run them at 90C), so that's 50C of temp rise. When it's for domestic heating, there comes a day in March you want a little bit of heat but not very much, which means the heat pump is running at a much lower percentage of it's peak capacity. CO2 heat pumps (at present) don't go low enough.
I don't know anything about helium but it remains to be seen how it will pan out with these kind of effects. It sounds like it's 5-10 years away from mass adoption (probably 10 if you don't want to be an early adopter and want to see how the longevity looks like).
My concern is this kind of article is actually a delaying tactic: a better (computer|car|aircraft|<product>) is always going to be on the horizon, but that shouldn't stop you buying what is available today. In 10 years you can then see whether this tech has panned out or not. That's better than sticking with a horse while waiting for jet planes.
Theo
In general oil fired domestic boilers are either off or on, they don't modulate. Could the same not be rue of heat pumps?
The government wants to stop the replacement of oil boilers from 2026 which leaves me with the problem of having to think about what to do - if I live long enough. The Ecocute which I did not know about looks interesting.
You can, but you lose efficiency that way. You can think of a heat pump like a car cruising down the road. Ideally you want to keep it at a constant speed (heat output). If you want to drive at 30mph, you don't drive at 70mph then slam on the brakes and stop for a while, then floor the accelerator and redline it back to 70mph.
You can mitigate that cycling to some extent by putting the heat into a buffer tank so the cycling is very infrequent (if you want 10% output, run at 100% output for one hour into the tank, then don't run for 9 hours), but for domestic heating that would be too big a tank for most houses to have space for.
Do you live in a particularly difficult to heat property? If your house is average (cavity walls, not a mansion) one of today's heat pumps will likely be fine.
If your house is poorly insulated, that is the thing to fix before worrying about what kind of heating to have. It'll pay back the investment with any kind of heating, and it'll mean you can fit a smaller and cheaper unit.
Theo
Some oil boilers do modulate.
The answer might be to use biofuel. AKA (modified) cooking oil.
There's no room for bigger radiators, nor is it feasible to improve the insulation of our Listed house. That's why it's marked as "EPC Exempt"
Andy
Wot, not even ones with extra panels and fins? Thickness of radiators is rarely a constraint.
Tim
Most of my rads are double convectors and a couple triples. I have always designed using double convectors in most rooms as I dont want to compromise wall usage and furniture siting more than necessary. So for me increasing the convection area of rads in most of my rooms would be very difficult especially in the kitchen diner which already relies on a kickspace fan convector for cold spells!
Buy a spare boiler at the end of 2025, and have it ready for when you need to fit a new one :-)
With domestic heating you can use the same trick used by under floor heating mixers. You mix the hot flow with the cold return of the heating loop, using a thermostatic blending valve and a pump for that loop.
You can also add weather compensation into the equation for better seasonal comfort and energy use reduction.
That doesn't really help the problem of the unit being unable to modulate down far enough. You can mix down the heat output if it's too hot, but there is a certain minimum flow rate. If you throttle that by mixing it down, the heat has nowhere to go and the unit has to shut down. Unless you have a large buffer to smooth it out, that's the cause of inefficient short cycling.
You'd likely find the same effect if you fitted a 100kW gas boiler (it probably can't modulate down to 1% output on a spring day), although there the start/stop process doesn't affect efficiency so much so cycling isn't such an issue.
Theo
This is a general problem though - you need to size the boiler (or whatever) to match the heating load. Yes modulation range (or "turn down ratio" if you prefer) can go some way to achieving that match, but you don't want 24kW where the house will never need more than 10kW in the depths of winter.
Indeed, if the sizing bit is done right, then dropping the flow temperature is doable. If the sizing is wrong, the you can't easily fix that, other than with a huge thermal store as you suggest.
Which is where we came in... the Japanese CO2 heat pumps that are designed to produce a tank of 90C hot water from cold are not very efficient at producing a trickle of 30C radiator water on a mild spring day. They would be fine to fill a swimming pool to 30C by mixing down, but too big in a domestic heating situation. That's outside of their modulation range.
Theo
But it could heat a thermal store, which then has stratification tappings and other means of providing 50+C water to showers and taps and a cooler flow for underfloor heating.
Not every home has space easily available for a thermal store let alone one big enough for heating as well as hot water.
Well there is a surprise, not one size fits all!
True, but ideal for those with underused cellars. Apparently such a thermal store is a next Big Idea according to an environmental scientist I know.
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