UK Heat Pump/Exchanger Heating.

[paulca]

So this has happened (I know not technically 'renewable'):
https://www.bbc.co.uk/news/science-environment-47559920

So, please be gentle as I'm only learning about this stuff.  The stuff I have read suggests these are NOT a good replacement for gas as the cost savings are actually negative for natural gas heating systems and cost more to run.  Of course the primary aim of this is to appear to be "lower carbon", however ... in the UK our electricity is mostly generated from coal.  So while the domestic home's direct carbon foot print might lower the overall carbon footprint may well rise due to grid/transmission loses etc.

On the heating systems.  I would guess my gas boiler system produces something like 12kW of heat into the water.  This can either be used to produce hot running water out of the tap at 80*C or water circulating the radiators are 90*C.  This means that to have a shower I need to run the boiler for about 5 minutes while I am in the shower.   With a heat exchanger system, which is incapable, to my understanding of producing water at anything like that temperature I would need an immersion heater which would typically be 7kW and need to be left on for an hour or longer to produce enough water so the water does not run cold in the shower.  So less efficient in real practical terms by a factor of 2 or more.

To heat my house after it has sat cooling for a whole day takes about 30 minutes.  In the dead of winter my heating runs for about 3 hours a day.  A heat exchanger system generally needs to run 24/7 as it only produces low level heating and radiators of 30*C or so.  I'm a little sketchy here so do correct me kindly.  The compressors in air-conditioner units, which to my understanding is just a heat pump backwards are usually around 2.5kW, so the heat exchanger will use 1/3rd that of the gas boiler, but need to run for a much, much longer time.

So less direct carbon, but most likely a much higher carbon foot print overall.

The smell of BS is also very high when sites suggest that water with anti-freeze can be used in ground loop heat exchangers.  So no state-change endothermic heat is captured... is this really is the case?  Therefore the only actual heat produced is from the compressor.  I cannot see how, without the stated endothermic heat capture through evaporation that a ground loop can do anything but heat the garden up and make the system even worse.  All I can assume is that these sites are incorrect and it is indeed state change refrigerant which is evaporated through the ground loop.... which in winter will freeze the soil and kill the grass eventually, just like office air con units in winter running in heat mode get covered in frost and ice.
Example: https://www.cse.org.uk/advice/renewable-energy/ground-source-heat-pumps
Also, I'm 100% certain in the dead of winter if I stuff a probe into my garden it will NOT be 11-12*C.

[george80]

It’s part of a bid by Philip Hammond to address the concerns of children protesting about climate change.

Ahhh fluck me!  |

Because children know so much about climate change don't they?
Every thing they are indoctrinated to think by gubbermint schools for close minded thinking they attend.

So less direct carbon, but most likely a much higher carbon foot print overall.

And there you have it. Why not crunch the real numbers for yourself and see what the real story is before doing anything?

[paulca]

And there you have it. Why not crunch the real numbers for yourself and see what the real story is before doing anything?

Not easy to do.  Well not in the short term.  Some data might be easy to come by, like power consumption of a typical heat exchanger system, but others are less easy to get/calculate.  Eg.  U values of heating systems and houses versus true power output of the system.  That and already the web is swamped by so called "Sustainable" power companies offering to install these thing with often poor or completely fictional data on their sites.

[MarkR42]

however ... in the UK our electricity is mostly generated from coal. 

No it isn't.

The balance is about 40% gas, 20% nukes, and the rest split between renewables, imports (mostly France's nukes) and a few percent coal / biomass.

[gmb42]

For current generation info see gridwatch, or iamkate.

[paulca]

however ... in the UK our electricity is mostly generated from coal. 

No it isn't.

The balance is about 40% gas, 20% nukes, and the rest split between renewables, imports (mostly France's nukes) and a few percent coal / biomass.

Yes, apologies, I meant to update that.  I believe it's currently about 37% gas, 15% renewables, 15% nukes, the remainder coal, imports, biomass, solar

EDIT: Of course on a calm cold night the 15% from renewables will be made up with coal and gas.  Nukes tend to be run flat out as they are cheap.

[madires]

A condensing boiler plus solar collectors could be interesting too.

[paulca]

A condensing boiler plus solar collectors could be interesting too.

Yes.  But I can't help but think of the heat flow diagram.

We insulate our houses to keep them temperature stable, then we run solar panels to produce electricity to pump heat from outside the house inside the house.  Seems a little ironic.  Not saying it's wrong, just sounds wrong.  Granted it can be -10*C outside and still sunny enough to max out the roof panels.

Anyway, thinking more about this, here's my thoughts currently.

A gas/oil boiler is capable of producing huge amounts of heat over short periods of time.  This facilitates that you can leave your house to go cold during the night when you are wrapped up in bed or during the day when you are out.  It only takes your boiler 30-60 minutes to heat the house back up.  So you can literally leave the boiler off for long periods in the day.

A heat exchanger system cannot produce a large amount of heat over a short period of time and so you can't reasonably leave them off for long periods during the day when you are out or at night.  To do so would require hours and hours for the system to warm the house back up.  Thus they are usually recommended to be run constantly.

I believe that this, unless there is another way to mitigate it, will result in larger fuel bills for most homes, especially if they are not A-Class insulated.

[Photon939]

It's better to think about heat pumps when you think about absolute temperature. It may be -10C outside but that is still 263K. It may be cold but there is still plenty of heat around.

A heat pump allows you to capture heat at colder temperatures by forcing liquid refrigerant to boil at that ambient temperature, causing the refrigerant temperature to drop and absorb heat. Then once it goes through a compressor that heat can be released by condensing it back to a liquid at a much higher pressure, resulting in useful temperatures.

In your example when you talk about a ground source heat pump; the source of heat is the ground, not the compressor (although it does generate some amount of heat).

If the ground is 5C then the heat pump can cool the antifreeze to say -5C which can then extract heat from the ground. This heat then gets released into the house after compression causes the temperature and pressure to increase.

[paulca]

In your example when you talk about a ground source heat pump; the source of heat is the ground, not the compressor (although it does generate some amount of heat).

If the ground is 5C then the heat pump can cool the antifreeze to say -5C which can then extract heat from the ground. This heat then gets released into the house after compression causes the temperature and pressure to increase.

But there has to be a state change or evaporative cycle.  You can't compress liquids.  You can put them under pressure, but that's not the same thing.  Also Boyles law applies to gases... does the same apply to liquid under pressure?

Anyway, with water+antifreeze you can't get them to boil to adsorb heat so the only heat you can source from the ground is heat that is above the temperature of the heating system.  So if the heating fluid is 10*C and the ground is 5*C heat will glow OUT of the heating system into the ground.

Again with an evapourative cycle it is the boiling of the fluid which absorbs the heat.  Like ether in your hand cools it.  Or a deodorant can becomes cold or, in extremes, frosted when you discharge it.

[Photon939]

In a ground source heat pump you have three separate fluid loops: air in your house that flows through the air handler, the refrigerant circuit inside the heat pump itself and then the ground loop filled the antifreeze.

The phase change happens inside the heat pump unit refrigerant cycle. Refrigerant boils at a low temperature and pressure on one side while it condenses back into a liquid at the high temperature and pressure side. The sides are reversible for cooling in the summer.

[jmelson]

The balance is about 40% gas, 20% nukes, and the rest split between renewables, imports (mostly France's nukes) and a few percent coal / biomass.

Huh?  I'm in the US, but how do they get serious amounts of power from France to the UK?  Do they have cables run through the chunnel?
I can't imagine burying HV cables across the channel, that seems like a real engineering project that I would have heard of.

Love to know how they do this!

Jon

[Neilm]

Huh?  I'm in the US, but how do they get serious amounts of power from France to the UK?  Do they have cables run through the chunnel?
I can't imagine burying HV cables across the channel, that seems like a real engineering project that I would have heard of.

There are undersea cables going under the channel. It is a high voltage DC system I pass the UK end at Sellinge as I go to work. It is not a buried cable as I know that the cables were damaged by an anchor a few years ago. https://en.wikipedia.org/wiki/HVDC_Cross-Channel

[paulca]

In a ground source heat pump you have three separate fluid loops: air in your house that flows through the air handler, the refrigerant circuit inside the heat pump itself and then the ground loop filled the antifreeze.

Right okay.  Got it.  So the heat pump unit cools the outside loop potentially below freezing, pumps it through the relatively warm ground.

I can only assume the logic behind adding an extra heat exchange circuit is just to avoid pumping refrigerant through the garden.

[kaz911]

The stats are clear

Electricity increase in cost every year at about 5%
Gas increases about 1.5% / year

Above a rough figures.  Last year until this year in the UK - electricity went up about 15+% and Gas 5% - so this year has been expensive compared to last year.

But if you go to electric heating you can be sure that it will be much much more expensive than Gas in very short time - even using heat pumps. I'm using heatpump in my office ONLY because it does not have Underfloor heating like the rest of my house (water based + modern Intergas condensing boiler with "predictive" Honeywell Evohome controller)

I did the heat pump calculations when i replaced my Gas boiler in Nov '18 - and ONLY if I factored in the government kickbacks would heat-pump heating be a slight financial benefit. And the kickback have limits - and might get removed. But after about 5-6 years of Electricity cost increases - the benefit would be negative financially.

[apis]

Also, I'm 100% certain in the dead of winter if I stuff a probe into my garden it will NOT be 11-12*C.

The temperature 1-2 meters below ground level will be the yearly average temperature where you live. Around London Wikipedia claims it's 11-13*C. However, if you pump a lot of cold mass through the ground it will cool it down so it's not easy to determine how much energy you can get long term.

[george80]

Here the ground temp BELOW 2m is 18oC.
I actually thought that was universal.  The lower you go the better apparently. Not sure it gets warmer but probably you have a better buffer on top.

I asked a mate whom is experienced in all sorts of AC and refrigeration about these heat pumps in cold weather. I pointed out many promote working below freezing.  He said they will but most are using resistance heating by then and until the point that kicks in, their efficiency plummets to what it is at 5o or so which makes sense.

I think his summation was best. If it was so good, he'd have it.  Which I have no doubt he would because he is a man that just buys the best of everything and within reason can afford it.
I asked him about hot water service heat pumps.  His reply was simply " I would not help you in any way to make such a mistake" .
He recounted how he installed a bunch of the things at a swimming centre after he warned them against it. Of course winter comes and the things take all day to recover instead of the hours they were supposed to.

Pretty simple to me, if he wouldn't have one, I don't need to know any more about them.

[james_s]

I can only assume the logic behind adding an extra heat exchange circuit is just to avoid pumping refrigerant through the garden.

Refrigerant is expensive, the pipes to contain refrigerant at the necessary pressures are expensive, it would cost a fortune to snake copper refrigeration plumbing around in the ground and then if you ever had a leak you'd lose your refrigerant charge and likely contaminate the system. By using a separate loop and a heat exchanger the refrigerant can all be contained within the main unit, the ground loop can be installed by anyone without needing to be a refrigeration tech and it can use cheap plastic pipe. If it leaks it's easy to patch and flush without messing with the refrigeration system.

[Towger]

A large number of ground/air source heating systems were installed into new houses here 10+ years ago.  From what I have seen and heard you are correct in your conclusions. 

Except for shows which can have instant 9/10/12kw heaters, so little energy is wasted.

The the problem with the heaters is they  use large amounts of electricity when cold,   are very expensive to install and replace.  They also require well insulated houses with active air systems. 

The current thinking appears to be aim for passive house heating, ditching the heat source system and spending the money saved on extra insulation.  Keeping the air exchange system (they work, are simple and relatively cheap).  Then you can heat the house with a small gas boiler and/or solid fuel stove.

Wood pellet boilers were also a green alternative from a few years back, but they are temperamental and appear to have fallen out of favour.

The real kicker to heat source systems is the replacement/maintance cost, vs a new traditional boiler for ~2k every 15 years or so.

[george80]

The current thinking appears to be aim for passive house heating, ditching the heat source system and spending the money saved on extra insulation. 

While that makes perfect logical sense for new homes, to a point, it's not as simple or cheap as often made out for established homes.
I have double roof insulation here and the next thing to do to insulate the place would be to double glaze all the windows and doors.
With 9 doors and 40 something windows, that would cost tens of thousands easily. It has been suggested this could be done over time but on further thought i'm not sure how worthwhile that would be. What you saved in one part of the house you'd loose on another.

In any case, it is cheaper for me by far to heat ( and certainly cool) the place than it is to insulate it.  With the solar I have I'm looking at about $1200 a year in power costs, $00 of that is the unavoidable " Supply charge" that I'll get hit for even if I don't use a watt of power.  That leaves my $800 a year.  even if my insulation upgrade " only" cost $8J, that's still a 10 yr pay back and I doubt I'll still be here then so why pay for some to save? And NO, it will not increase the property value one single bit here.  the new kitchen and bathroom will but solar, double glazing etc is NOT an advantage here.

As far as the new homes go, I have to wonder about that.
They are built so cheap and flimsy these days I very much wonder how many new home buyers would be looking to spend more than the possibly could? Perhaps the small section of the mature home builders would but the majority of homes are sold to 1st home buyers here and they are robbing peter to pay paul as it is.
When they can't afford furniture to sit on or curtains, I doubt long term savings with insulation is high on their priority list.

There are minimum standards here for home insulation but I doubt many places have extra money put into them to improve that.

[f4eru]

The current thinking appears to be aim for passive house heating, ditching the heat source system and spending the money saved on extra insulation.  Keeping the air exchange system (they work, are simple and relatively cheap).  Then you can heat the house with a small gas boiler and/or solid fuel stove.

The problem is you cannot just "ditch the heat source system", it does not work, you need a heating system to cover the house when it's not sunny in winter.
But a typical Passivhaus (which is a certified low energy house) can often heat directly the air in the recirculating air exchange system. Then you save money because this makes one less system to install (no water based heaters to spread through the house)

Typically, a Passivhaus needs an average of 1-3 kW of heating power during cold sunless days, depending on temperature, location, size, use....
It's very small compared to older houses, so you can either use, for 2.3 kW bad day average:

1) A wood burning (chips, pellets, or log) appliance with storage, that burns with 18kW for 6h every second day (my configuration), with 90% efficiency ( if really optimum)
2) A 8kW gas burner without storage, running for 1/4 of the time. The thermal mass of hte house is the (cheaper) storage medium here between firing cycles (90% efficiency achievable also)
3) a 2,5 kW heat generating heat pump running nearly all the time (typical COP of 2.5 on a bad day, means it consumes 1kW of electricity)

[f4eru]

In any case, it is cheaper for me by far to heat

That's often the case with older houses. But on 15-25 Years, it often pays back.

They are built so cheap and flimsy these days I very much wonder how many new home buyers

Depends wildly on the region. Here in Europe, laws are now in place in some of the big countries to make sure that new homes are low in energy consumption, so it is mandatory, and standards are improved gradually.

[Towger]

Building insulation standards here are very high, the problem is the lack of official inspections to insure builders are not taking short cuts.  It is not possible to retro fit an existing house to current standards here, unless the house is effective rebuilt.  I have seen it done, but it is cheaper to knock and rebuild.

Double glazing is the norm here and most existing houses have been upgraded years ago.  300mm of insulation in the roofs etc.  The problem is the walls, so the government gives grants to add external or internal insulation etc.  Still it will not get up to new build standards.

[paulca]

My apartment is in a small building built around 2004.  It's well insulated both in the roof, walls (cavity wall insulation) and double glazing all round.  The floor is solid concrete beam and slab due to it being commercial premises below.  In winter it's great, fairly cheap to heat.  In fact the heating is practically switched off from May through to October just run for 15 minutes morning and evening to "maintain" it.

However as it's not "next gen" in summer there is a problem.  It's not uncommon on a sunny day for the interior to get up over 30*C and I have recorded 38*C in my bedroom which is verging on unsafe.  This is with or without the windows open.

So in winter I run my gas boiler, in summer I run a 2.5kW air conditioner, usually in the bedroom, but I often leave it on during the day with the door open to allow the cool air to pour down the stairs.  (Yes, 2 floor apartment).

While it feels wrong the best approach is to shut all the curtains on hot days and put the black out blinds down on the skylights.

[george80]

  It's not uncommon on a sunny day for the interior to get up over 30*C and I have recorded 38*C in my bedroom which is verging on unsafe. 

Hahaha!

Do you know how many days we had here in the 40's on the trot? At least 2 weeks worth non stop with a month of here and there cooler days. Didn't even put the AC on till it hit 35.  30 Was a cool change here only a month or so ago.
We are coming into winter now and where I am, we will get a few weeks down to zero with the occasional Minus morning temps. We got a bunch of -5's last winter and that was bad.

In some places that would be a warm winter. Mate in canada has been sending me pics of the snow Piled half way up his garage door.
I don't know how anyone could live in frozen hell holes like that but I guess they couldn't imagine living  in flaming hells like I take for granted.

We have insulation standards here too but I think they would be pretty poor in comparison to a lot of places. Double glazing is VERY rare here, Maybe a bit more popular down south where it's colder but still not typical by any stretch.

I'm in the process of building an oil burning heater to offset our heating/ power bills this winter.  Basing it on a 100KW spa heater. Probably only need to run at about 3Kw most of the time but will be interesting to see how it averages out.
I want to keep the place itself warm, not just the air.  I think if you don't heat soak the place, the walls, furniture, floors etc you are never really warm. If I ever built there would be a lot of things I'd do, hydronicaly or maybe electric floors would be one thing.
We are redoing the kitchen and I saw something at the tile place so might look into that to see if it's remotely affordable.

If I had a bit more suitable space, I'd like to put an IBC in the house full of heated water so there was a thermal mass slowly radiating heat all the time similar to an old russian stove.  by the same token the water could be cooled with a refrigerated system especially at night when temps were cooler and into the mornings. The heat really kicks in after lunch time here, Generally if you are out the direct sun the air temps aren't too bad but that sun sure fries you.