Different flavours of heat pump and ventilation
Discussion
I came across this recently:
https://www.qvantum.com/uk/qvantum-qe/
It's a heat pump, which takes its heat from air it pumps out of your home, and stores the heat in a water cylinder.
It seems to me it might go some way to answering the common objections to heat pumps, like 'it takes all week to heat the house from cool', while also addressing ventilation issues.
I'm considering buying a place where this might be a good idea.
Alternatively some sort of MVHR with a heat pump between the two sides has been on my mind.
Which is sort of the same thing as ducted aircon really.
I'm also considering 'cheating' by retaining an oil boiler and/or a wood burner with back boiler, so the heat pump only needs to work well 'most of the time' not during blizzards or big freeze events that make the news.
I've also been talking to someone who's had a GSHP for 20-odd years and wouldn't want anything else.
Any experience or thoughts to share?
https://www.qvantum.com/uk/qvantum-qe/
It's a heat pump, which takes its heat from air it pumps out of your home, and stores the heat in a water cylinder.
It seems to me it might go some way to answering the common objections to heat pumps, like 'it takes all week to heat the house from cool', while also addressing ventilation issues.
I'm considering buying a place where this might be a good idea.
Alternatively some sort of MVHR with a heat pump between the two sides has been on my mind.
Which is sort of the same thing as ducted aircon really.
I'm also considering 'cheating' by retaining an oil boiler and/or a wood burner with back boiler, so the heat pump only needs to work well 'most of the time' not during blizzards or big freeze events that make the news.
I've also been talking to someone who's had a GSHP for 20-odd years and wouldn't want anything else.
Any experience or thoughts to share?
OutInTheShed said:
It's a heat pump, which takes its heat from air it pumps out of your home, and stores the heat in a water cylinder.
It seems to me it might go some way to answering the common objections to heat pumps, like 'it takes all week to heat the house from cool', while also addressing ventilation issues.
I'm considering buying a place where this might be a good idea.
It sounds like a fancy MVHR: most of them already utilise any heat which is "pumped out of your home". This particular sales blurb sounds like snake-oil to me. There's no such thing as free energy, and in this country it's rare to have surplus heat indoors to use.It seems to me it might go some way to answering the common objections to heat pumps, like 'it takes all week to heat the house from cool', while also addressing ventilation issues.
I'm considering buying a place where this might be a good idea.
Fit MVHR if you'd like, but don't over-complicate it. Then consider ASHP/GSHP depending upon your preference.
(I have GSHP and ASHPs, so have some experience of them).
Simpo Two said:
OutInTheShed said:
It's a heat pump, which takes its heat from air it pumps out of your home, and stores the heat in a water cylinder.
Let me run that by again... it pumps heat out of my house, stores it, then pumps it back in...You can do the same sort of thing to recover heat from waste water.
Simpo Two said:
OutInTheShed said:
It's a heat pump, which takes its heat from air it pumps out of your home, and stores the heat in a water cylinder.
Let me run that by again... it pumps heat out of my house, stores it, then pumps it back in...There are variations of these things.
The attraction is, you're not trying to extract heat from cold air outdoors, with the risk of creating a lot of frost.
There are also 'heat stores' which can be anything from a big tank of water up to complex chemical stuff.
Some of the appeal is that it might run on solar or off peak electricity, without needing a big battery.
But I'm coming from considering a cottage that will need some serious care to deal with damp as well as cold.
OutInTheShed said:
I understand that it takes stale air from your bathroom for instance at say 18degC, cools it to say 4 degC, shoves the cold air out the door and puts the heat into water at up to 60degC.
There are variations of these things.
The attraction is, you're not trying to extract heat from cold air outdoors, with the risk of creating a lot of frost.
There are also 'heat stores' which can be anything from a big tank of water up to complex chemical stuff.
Some of the appeal is that it might run on solar or off peak electricity, without needing a big battery.
But I'm coming from considering a cottage that will need some serious care to deal with damp as well as cold.
What does the extracted warm air get replaced with? Drawn in cold air?There are variations of these things.
The attraction is, you're not trying to extract heat from cold air outdoors, with the risk of creating a lot of frost.
There are also 'heat stores' which can be anything from a big tank of water up to complex chemical stuff.
Some of the appeal is that it might run on solar or off peak electricity, without needing a big battery.
But I'm coming from considering a cottage that will need some serious care to deal with damp as well as cold.
That's the problem that MHVR is intended to solve: scavenge heat from the exhaust and heat the incoming air.
Been looking at them recently and some of them claim 95%+ efficiency as well as doing things like 1) night time cooling (drawing in cold air and not heating it); and 2) cold recovery (to actively cool incoming air using cold scavenged from exhaust) in the summer / if you have aircon and the ambient inside is lower than outside.
We have a thermal store on our ASHP: couple of hundred litres that acts as a buffer to prevent the ASHP cycling too much. It's also possible, but we haven't done it on this one, to hook up evacuated tube solar to the same buffer tank in order to further reduce the ASHP demand.
Exhaust air heat recovery pumps have been around for ages with my first experience of them probably 20 years ago!
The developer I was working with at the time ended up paying the purchasers compensation as the electricity consumption was WAY in excess of the figures stated in the sales literature.
A bit of user error contributed to the problem; however, if I were to specify one now it would be within apartments only.
The developer I was working with at the time ended up paying the purchasers compensation as the electricity consumption was WAY in excess of the figures stated in the sales literature.
A bit of user error contributed to the problem; however, if I were to specify one now it would be within apartments only.
LooneyTunes said:
OutInTheShed said:
I understand that it takes stale air from your bathroom for instance at say 18degC, cools it to say 4 degC, shoves the cold air out the door and puts the heat into water at up to 60degC.
There are variations of these things.
The attraction is, you're not trying to extract heat from cold air outdoors, with the risk of creating a lot of frost.
There are also 'heat stores' which can be anything from a big tank of water up to complex chemical stuff.
Some of the appeal is that it might run on solar or off peak electricity, without needing a big battery.
But I'm coming from considering a cottage that will need some serious care to deal with damp as well as cold.
What does the extracted warm air get replaced with? Drawn in cold air?There are variations of these things.
The attraction is, you're not trying to extract heat from cold air outdoors, with the risk of creating a lot of frost.
There are also 'heat stores' which can be anything from a big tank of water up to complex chemical stuff.
Some of the appeal is that it might run on solar or off peak electricity, without needing a big battery.
But I'm coming from considering a cottage that will need some serious care to deal with damp as well as cold.
That's the problem that MHVR is intended to solve: scavenge heat from the exhaust and heat the incoming air.
Been looking at them recently and some of them claim 95%+ efficiency as well as doing things like 1) night time cooling (drawing in cold air and not heating it); and 2) cold recovery (to actively cool incoming air using cold scavenged from exhaust) in the summer / if you have aircon and the ambient inside is lower than outside.
We have a thermal store on our ASHP: couple of hundred litres that acts as a buffer to prevent the ASHP cycling too much. It's also possible, but we haven't done it on this one, to hook up evacuated tube solar to the same buffer tank in order to further reduce the ASHP demand.
The problem with MVHR in much of the UK is that outdoors is not hugely colder than indoors much of the time. You can use a lot of high cost electricity to recovery a modest amount of low value heat. Plus, the hardware is very expensive for what it is, although it has got cheaper compared to 10 years ago.
It's also hard to retrofit in many homes.
Some people of course simply use reversed aircon for heating, but it seems wrong to need two sets of fans for aircon and HR.
People sell PIV systems with dumb resistive heaters, it makes sense to me to have a heat pump combined with PIV.
The cheapest heating if we get this project will be burning wood, but I want a decent level of heating which comes on at the push of a button or at the whim of a microprocessor.
I know of a refurb/self-build locally which has a system of thermal storage, the idea being to store whatever heat is cheapest or most convenient.
OutInTheShed said:
paralla said:
The specs are very light on power consumption data but it recommends a 35A fuse (at 230V) and has 5kW of immersion heaters which will keep you in the poor house.
I'm seeing 5kW of immersion heaters connected to at least 10kW of solar panels...paralla said:
10kW of solar panel s is about 50 square meters of solar panels. 10kW of solar panels is enough to make any sort of electric heating system cost effective to run.
What will those 10kw of solar panels contribute midwinter when the heating demand is by far the greatest? Not something I have personal experience of but a friend has a huge array that generates massive surplus during the spring and summer but barely covers his background usage in winter despite his heating being oil and firewood powered. Snow and Rocks said:
paralla said:
10kW of solar panel s is about 50 square meters of solar panels. 10kW of solar panels is enough to make any sort of electric heating system cost effective to run.
What will those 10kw of solar panels contribute midwinter when the heating demand is by far the greatest? Not something I have personal experience of but a friend has a huge array that generates massive surplus during the spring and summer but barely covers his background usage in winter despite his heating being oil and firewood powered. ATG said:
Simpo Two said:
OutInTheShed said:
It's a heat pump, which takes its heat from air it pumps out of your home, and stores the heat in a water cylinder.
Let me run that by again... it pumps heat out of my house, stores it, then pumps it back in...You can do the same sort of thing to recover heat from waste water.
Recovering heat from waste bathwater is a nice idea but how big is the gadget to do it, how big is it and how many baths does it take to pay back? That's the thing about these eco schemes - theoretically great but few stack up in reality.
A heat recovery system extracts heat from outgoing air and uses a heat exchanger to pre warm incoming air.
Trying to heat water with it to any meaningful amount sounds like a fools errand.
I made a shower waste water heat recovery ‘system’ from a 2m length of 42mm and 35mm copper pipes and fittings I had lying around. Mounted vertically, shower waste water goes down inside the 35mm pipe and the cold feed comes up the 42mm that’s soldered around it with reduction tees either end to seal it.
It works - you can definitely feel the difference in cold feed temps - but in terms of money saving I’d guess it’s closer to pennies per year rather than pounds. Add the cost to buy the bits and… err.. probably not worth bothering.
OutInTheShed said:
I think there is potential for this to work at 200 or 300% efficiency.
I'm still building my knowledge of ASHP and MHVR but that doesn't sound like the full picture to me.When you look at ASHP, the COP you see that gives >100% efficiency is based on the input electrical energy consumed. The ambient heat that input energy causes to be sequestered by the unit is "free" ambient heat in the environment. In practical terms, the source of ambient heat is almost limitless.
If you were looking at 200-300% efficiency whilst using exhaust heat then presumably they're applying the same logic, basing it on ambient heat (scavenged this time from the exhaust) being free? If so, that would seem to over simplify things because that exhaust heat could be used for other purposes (traditional MHVR) and is only available in finite volumes.
What you really need, and the manufacturer should have/be able to supply, is a proper comparison between their system and more normal ones? I'd be really intrigued to see what they can come up with.
LooneyTunes said:
OutInTheShed said:
I think there is potential for this to work at 200 or 300% efficiency.
I'm still building my knowledge of ASHP and MHVR but that doesn't sound like the full picture to me.When you look at ASHP, the COP you see that gives >100% efficiency is based on the input electrical energy consumed. The ambient heat that input energy causes to be sequestered by the unit is "free" ambient heat in the environment. In practical terms, the source of ambient heat is almost limitless.
If you were looking at 200-300% efficiency whilst using exhaust heat then presumably they're applying the same logic, basing it on ambient heat (scavenged this time from the exhaust) being free? If so, that would seem to over simplify things because that exhaust heat could be used for other purposes (traditional MHVR) and is only available in finite volumes.
What you really need, and the manufacturer should have/be able to supply, is a proper comparison between their system and more normal ones? I'd be really intrigued to see what they can come up with.
I want a diagram showing quantities of air and their temperatures and where they are going.
paralla said:
Even 50 square meters of solar panels won t contribute much at all in the dead of winter when heat is needed the most. That s where the 35A fuse comes in and it draws 5kW from the grid and keeps you in the poor house.
I would need to understand how much heat is used in each month and how much solar power can be generated in each month.I don't have stats to hand, but consider most people use some heating 8 months of the year.
It might be possible to cover say 80% for two of those months, 60% for another two and 20% for the worst two.
So you might halve your oil use. You'd have ample free electricity for aircon in the summer.
Aiming for zero is a big ask.
I'm also coming at it from an angle of needing to do something about airflow to avoid 'manky auld cottage' syndrome.
Trying to look at combined solutions to address all of the problems.
FWIW, your 50sqm of panels might be 10kW or more. 10kW might yield 300kWh in January That's maybe 900kWh of heat, saving 100 litres of oil.
If you can get any cheap electricity from the grid, better still?
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