UK Heat Pump/Exchanger Heating. - Page 1
Forum section: electronics / general

author: paulca
author_rank: Super Contributor
timestamp: March 14, 2019, 08:52:15 am
content: So this has happened (I know not technically 'renewable'):https://www.bbc.co.uk/news/science-environment-47559920So, 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-pumpsAlso, I'm 100% certain in the dead of winter if I stuff a probe into my garden it will NOT be 11-12*C.

author: george80
author_rank: Regular Contributor
timestamp: March 14, 2019, 09:48:14 am
content: 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.QuoteAnd there you have it. Why not crunch the real numbers for yourself and see what the real story is before doing anything?

author: paulca
author_rank: Super Contributor
timestamp: March 14, 2019, 12:52:59 pm
content: Quote from: george80 on March 14, 2019, 09:48:14 amNot 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.

author: MarkR42
author_rank: Regular Contributor
timestamp: March 14, 2019, 01:18:47 pm
content: Quote from: paulca on March 14, 2019, 08:52:15 amNo 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.

author: gmb42
author_rank: Frequent Contributor
timestamp: March 14, 2019, 01:38:52 pm
content: For current generation info seegridwatch, oriamkate.

author: paulca
author_rank: Super Contributor
timestamp: March 14, 2019, 01:51:58 pm
content: Quote from: MarkR42 on March 14, 2019, 01:18:47 pmYes, apologies, I meant to update that. I believe it's currently about 37% gas, 15% renewables, 15% nukes, the remainder coal, imports, biomass, solarEDIT: 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.

author: madires
author_rank: Super Contributor
timestamp: March 14, 2019, 02:18:45 pm
content: A condensing boiler plus solar collectors could be interesting too.

author: paulca
author_rank: Super Contributor
timestamp: March 14, 2019, 02:32:06 pm
content: Quote from: madires on March 14, 2019, 02:18:45 pmYes. 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.

author: Photon939
author_rank: Regular Contributor
timestamp: March 14, 2019, 02:54:19 pm
content: 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.

author: paulca
author_rank: Super Contributor
timestamp: March 14, 2019, 03:01:20 pm
content: Quote from: Photon939 on March 14, 2019, 02:54:19 pmBut 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.

author: Photon939
author_rank: Regular Contributor
timestamp: March 14, 2019, 03:33:17 pm
content: 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.

author: jmelson
author_rank: Super Contributor
timestamp: March 14, 2019, 07:23:40 pm
content: Quote from: MarkR42 on March 14, 2019, 01:18:47 pmHuh? 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

author: Neilm
author_rank: Super Contributor
timestamp: March 14, 2019, 07:49:41 pm
content: Quote from: jmelson on March 14, 2019, 07:23:40 pmThere 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

author: paulca
author_rank: Super Contributor
timestamp: March 14, 2019, 08:15:52 pm
content: Quote from: Photon939 on March 14, 2019, 03:33:17 pmRight 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.

author: kaz911
author_rank: Super Contributor
timestamp: March 14, 2019, 09:58:35 pm
content: The stats are clearElectricity increase in cost every year at about 5%Gas increases about 1.5% / yearAbove 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.

author: apis
author_rank: Super Contributor
timestamp: March 15, 2019, 09:58:14 pm
content: Quote from: paulca on March 14, 2019, 08:52:15 amThe 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.

author: george80
author_rank: Regular Contributor
timestamp: March 16, 2019, 04:58:04 am
content: 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.

author: james_s
author_rank: Super Contributor
timestamp: March 16, 2019, 07:08:31 am
content: Quote from: paulca on March 14, 2019, 08:15:52 pmRefrigerant 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.

author: Towger
author_rank: Super Contributor
timestamp: March 16, 2019, 08:11:03 am
content: 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.

author: george80
author_rank: Regular Contributor
timestamp: March 16, 2019, 09:24:29 am
content: Quote from: Towger on March 16, 2019, 08:11:03 amWhile 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.

author: f4eru
author_rank: Super Contributor
timestamp: March 16, 2019, 09:36:24 am
content: QuoteThe 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)

author: f4eru
author_rank: Super Contributor
timestamp: March 16, 2019, 09:41:40 am
content: QuoteThat's often the case with older houses. But on 15-25 Years, it often pays back.QuoteDepends 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.

author: Towger
author_rank: Super Contributor
timestamp: March 16, 2019, 10:03:15 am
content: 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.

author: paulca
author_rank: Super Contributor
timestamp: March 16, 2019, 10:29:43 am
content: 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.

author: george80
author_rank: Regular Contributor
timestamp: March 16, 2019, 11:07:46 am
content: Quote from: paulca on March 16, 2019, 10:29:43 amHahaha!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.

author: paulca
author_rank: Super Contributor
timestamp: March 16, 2019, 12:52:56 pm
content: So electrical powered heating of any form... He's a few indicative numbers based on a bit of research into power plants and electrical grids.For every 100 units of energy you extract from fuel at a power plant, be that oil, coal or nuclear, only approximately 30-40 are converted to electrical power. This means that a 1GW power plant is actually producing closer to 3GW of heat energy. Some indicative figures here:https://www.brighthubengineering.com/power-plants/72369-compare-the-efficiency-of-different-power-plants/Of those 30-40 units, up to 10%, are lost through the electrical grid. (Based onhttps://data.worldbank.org/indicator/eg.elc.loss.zs)So having taken the (often fossil fuel based) hit of releasing 1GW of heat, you only end up with around 300MW reaching homes. Even if the heating system is 100% efficient, your overall efficiency is 30% or so.Conversely, burning the fuel and using the heat directly as the primary product of the system the efficiencies are far, far higher with the only losses I can think of are the heat absorbed into the boiler system, the electrical power for pumps et al and loses through chimneys. I'd poke a finger in the air and say at least 60-70% efficient. Although, one would need to account for the energy requirements to supply that fuel to the homes rather than to a single power plant.

author: apis
author_rank: Super Contributor
timestamp: March 16, 2019, 12:59:57 pm
content: Quote from: george80 on March 16, 2019, 04:58:04 amHere it's about 7-8°C below ground. In many parts of the world, it was (and still is) common to build a root cellar, i.e. a room a below ground level, which would have had a good temperature for refrigeration. But as you noticed, how effective it will be depends on where you live.If you start going really deep the temperature starts rising again, about 2-4°C per 100 m, so at 3 km depth you can be at above boiling temperature of water (at sea level pressure). But near the surface (below 1-2 meter) the temperature will be close to the yearly average.

author: george80
author_rank: Regular Contributor
timestamp: March 16, 2019, 02:11:53 pm
content: Quote from: paulca on March 16, 2019, 12:52:56 pmThe spa Boiler I am going to use in gas form at least is very High efficency, 85% from memory. Won't change much with Oil.It was a while ago since I did it and would have to check the vid but from memory I think I was able to burn 20-30Kw worth of oil using a 12V Bilge blower pulling 4A. For this I'll call it 12W Max.I'll use an electric fuel pump also 12v Which from memory is 3A intermittent as it's a pulse type pump. 36wControllers etc wouldn't even be 1A so 12W.Fan for house, 18w, Circ pump, probably 30W solar pump.Call it 120w as over kill. For this electrical input I'll be getting 5Kw+ out of the burner with the oil. Not a bad result.If I run it 10hrs a day, 1.2 Kwh or what 2 solar panels will easily produce and then some through winters days.Oil is roughly 10Kw/h L , I reckon 3 Kwh average output, 4L day should allow for inefficiency and desired output.Geez, had to recheck that, seems so low. Probably because I am more used to playing with burners cranking out 200-600KW worth of heat. Call it 5L day for the hell of it, 35 Wk, 12 weeks say, 420L.And here I am thinking I'd need a couple of IBC's.This is going to be more economical than I ever thought!Thats the thing with liquid fuels, there is so much energy in them compared to electricity.Last year my main 9KW array made 15000Kwh. That's 1.5 IBC's worth of oil. I could pick that up in a day, weekend at the outset.To put it in another perspective, a LARGE car battery holds about 1Kwh of power. Imagine the space 1500 of the things would take up! Oil, 1.5 Cu m. batteries, 157.5 Cu m.Oil would weigh about 1.275 ton. Car batteries, about 375 Tons !!Going to get a HE so I can run the domestic hot water feed through that with the output from the oil heater on the other side to preheat the domestic hot water. that should in itself take quite a few KW off the hot water demand. I calculated on a full tank there would be about 4 Kw of energy needed just to bring the incoming water from the winter temps to the same temp it enters in summer.If I can bump the hot water input to even 40oC, will save a lot of power right there.Other alternative is I have a lot of roof left and a lot of smaller panels so if i can find a suitable electric HWS, I might just hook it to a stand alone array and pre heat the water that way. Won't need to get up to full temp , any increase will lessen the load off the main heater.

author: f4eru
author_rank: Super Contributor
timestamp: March 16, 2019, 06:23:52 pm
content: QuoteYep.Direct flame heating at home is much more efficient that resistive electrical, due to the bad efficiency of power stations.Flame at home is approx. on par with heat pump if the electricity comes from only fossil.

author: coppice
author_rank: Super Contributor
timestamp: March 16, 2019, 11:57:14 pm
content: Quote from: george80 on March 16, 2019, 11:07:46 amIf you are in place with high temperatures in the summer, double glazing can be a problem. The greenhouse effect in the warm weather can incur more energy usage to cool the place than it saves in the cold weather. Various glass coatings can help reduce the greenhouse effect, but they can't eliminate the problem. If you are in a place where the summers are not hot enough to demand air conditioning, double (or triple) glazing is always a win.In a few hot places, like Southern China, lots of new homes have double glazing, required by the building regulations. Its not for thermal insulation, though. Its for noise reduction in homes near highways.

author: james_s
author_rank: Super Contributor
timestamp: March 17, 2019, 01:33:21 am
content: I assume double glazing is double pane windows? As far as I know they have been a universal requirement in the USA since the mid 70s, I've seen a few old houses without them but most have been upgraded by now due to the substantial energy savings. In a warm climate it probably wouldn't matter as much but here houses with single pane windows feel cold and drafty.

author: paulca
author_rank: Super Contributor
timestamp: March 17, 2019, 11:50:23 am
content: Yeah, double or even tripple glazed windows have two (or three) pains with a gap in the middle, can't remember if it's just air or a vacuum.

author: paulca
author_rank: Super Contributor
timestamp: March 17, 2019, 12:09:18 pm
content: Quote from: f4eru on March 16, 2019, 06:23:52 pmThe worst bit about the UK's plans is that it intends to replace gas with heat pumps. Which when you read a bit of several charity energy advice websites and the like, none say it is a good replacement for gas. Few even mention oil heating. They say the primary target is to replace coal heating and electric storage heaters.

author: Towger
author_rank: Super Contributor
timestamp: March 17, 2019, 04:12:47 pm
content: Quote from: paulca on March 17, 2019, 12:09:18 pmThat makes as much sense as Brexit. The house needs to be build to extremely high insulation standards and even still they are not great.

author: richard.cs
author_rank: Super Contributor
timestamp: March 17, 2019, 05:52:07 pm
content: Quote from: paulca on March 16, 2019, 12:52:56 pmNo argument there. Mid 30s are pretty typical except for combined cycle gas turbines which can be significantly over 50%QuoteIn my part of the world it's closer to 7% but I'll use your numbers. 10% loss on 40% is 36%, 10% on 30% is 27%. And for reference a 54% efficiency CCGT power plant with 7% loss would be 52%QuoteGiven the above 30% seems a little low, 40% would be perhaps more typical in areas where a significant amount of generation is from gas. In any case this discussion is about heat pumps which have a typical coefficient of performance around 3, varying depending on the inside and outside temperatures. 2 kW of heat is moved from outside to inside for each 1 kW used to move it, and 2+1 kW is dissipated inside. With 30% fuel-electricity that would give 90% heating efficiency, and with a more typical 40% fuel-electricity it would give 120%. Those numbers are sounding pretty good to me. More so when not all of the input to the grid is from burning fuel.*For optimum performance the temperature difference should be minimised, so higher COP is achieved with ground source systems (warmer outside heat source) and heated-air or heated-floor inside (lower heat pump output temperature compared with wet radiators).* Right now the total fuel-burning contribution to the UK grid is 1% coal, 35% combined-cycle gas, and 5% wood. A further 14% is from nuclear, but then "burning" uranium at home and using the heat directly is not a practical option for most of us.

author: james_s
author_rank: Super Contributor
timestamp: March 17, 2019, 07:33:55 pm
content: Quote from: paulca on March 17, 2019, 12:09:18 pmThat depends on the cost of gas and electricity. Here in the Northwest USA heat pumps work great, my mom's house has one in tandem with the gas furnace that was present when she moved there. I've set it up so the heat pump is used down to an outside temperature of around 30F at which point it switches over to the gas furnace which serves as the air handler for both systems. Even a pure heat pump is somewhat cheaper to run year round here as the climate is mild. Gas is around $1 per Therm (100k btu/hr IIRC) and electricity is approximately $0.08 per kWh.

author: richard.cs
author_rank: Super Contributor
timestamp: March 17, 2019, 08:35:56 pm
content: Quote from: james_s on March 17, 2019, 07:33:55 pmIndeed it does, and the effect is calculable. If you compare a modern condensing gas boiler with an efficiency around 90% with a heat pump with a coefficient of performance around 3, then if the electricity:gas price ratio for a given amount of energy exceeds 3/0.9=3.3 then gas heating is cheaper. Prices per kWh in the UK are around £0.124 and £0.028 for electricity and gas respectively, so a ratio of 4.4. Here gas works out cheaper than a heat pump (with these COP and efficiency assumptions).You can turn this on it's head and calculate the COP you need to achieve to break even. COPmin= PriceE/PriceG* EfficiencyGWith the numbers above you get a minimum COP of 3.95.I am struggling to find measured real-world data for domestic style heat pumps, the COP I have used is a bit of a guess really. This:https://www.researchgate.net/figure/Average-heating-coefficient-of-performance-for-air-and-ground-source-heat-pumps-left-and_fig7_255759857suggests 3.3-3.9 for air source at space heating temperatures (40 C hot side) and 4.5-5.4 for ground source where the cold side is significantly warmer. That would make ground-source cheaper than gas with current UK prices.

author: paulca
author_rank: Super Contributor
timestamp: March 18, 2019, 06:09:55 am
content: Quote from: james_s on March 17, 2019, 07:33:55 pmI think this is the nub of the problem. It's cheap to carry on as we are. If you give people cheap fuel bills they will burn whatever and at the same time cry about Big Oil ruining the planet. If you make it cheap and profitable for big energy companies they will burn lorry loads of grannies to make money.Of course attempts at costing environmental damage (carbon tax et al) have typically been exploited but at least it's trying. Although, generally, in the UK anyway, those taxes get levelled at the consumer, not the energy companies.

author: paulca
author_rank: Super Contributor
timestamp: March 18, 2019, 06:15:03 am
content: Quote from: richard.cs on March 17, 2019, 05:52:07 pmNot sure about the 2+1kW as I'm fairly sure the compressors are usually mounted outside due to noise and space. A lot of the energy from the compression is doubtless lost.But fair enough. What about the issue with "idle time"? During the work week, I can leave my heating off for 8 hours a day when I'm out and 7 hours at night when I'm asleep. Only because I can heat the house in under 30 minutes when I switch it back on. If I went for a heat pump solution I can't really do this anymore. I would need to leave it running almost constant to keep the heat in the house. It's too early in the am here for me to crunch those numbers, I'll maybe try later.

author: richard.cs
author_rank: Super Contributor
timestamp: March 18, 2019, 10:14:31 am
content: Quote from: paulca on March 18, 2019, 06:15:03 amMost of that 1 is mechanical energy that is transferred into the working fluid, not motor inefficiency. Often the refrigerant is the motor coolant so much of the motor losses end up inside too.QuoteYes, clearly if you can heat with much higher power then you can heat only when occupied. Your unoccupied temperature is then lower and you loose less heat in that time because of the lower delta-T. This depends a lot on occupation patterns, insulation, etc. so will be quite variable.I suspect however that the effect is quite small, my house when unheated falls perhaps 1-2 C in about 10 hours when I am at work with a delta to the outside of around 15-20 C. This means that the delta-T and therefore the heat flux out of my house is only about 10% lower than it would have been had I heated the house during that time.

author: awallin
author_rank: Frequent Contributor
timestamp: March 18, 2019, 06:01:18 pm
content: Quote from: richard.cs on March 17, 2019, 08:35:56 pmhere up North where we need a lot of heating in the winter they say the COP also depends on what kind of heat you want the pump to deliver.If you have 'normal' water-filled radiators where the pump heats the radiator-water then it needs to be up to +50C in the winter when it's -10..-20C outside. ground-source COPs maybe in the 3-4 range.OTOH many new homes are built with water-circulating floor-heating where the water in the floor only needs to be heated to maybe +25..+35C to keep that same +22C room-temperature in the winter. ground source COPs in the 4-5 range (?).

author: richard.cs
author_rank: Super Contributor
timestamp: March 18, 2019, 06:47:51 pm
content: Yes, those numbers sound believable, and a clear demonstration of why heat pumps are best when coupled to underfloor heating or to warm air circulation - conventional water filled radiators just have too little surface area so need to be hotter, although I suppose they could be oversized if you were designing for a heat pump. It does mean heat pumps may be a poor choice to retrofit in place of a gas boiler unless that boiler was already heating floors.My house has a relatively inefficient non-condensing gas boiler and a plumbing arrangement that was obsolete the day it was installed (sometime in the 1970s). "Single pipe" heating isinteresting, a single loop of pipe from the boiler and back with radiators tapped off it such that they are in parallel to a short length of pipe. The boiler and pump keep the loop of pipe hot, and the radiators thermosiphon off the loop - the pump alone cannot force any significant flow through them. Each radiator on the loop is larger than the one before because of the dropping temperature, but the first one is tiny and means I have to keep the boiler outlet temperature right up to keep that room from getting too cold. It's not inherently a bad system, but I don't think they really got the ratio of radiator sizes right on mine.

author: paulca
author_rank: Super Contributor
timestamp: March 22, 2019, 08:31:08 am
content: I am buying a house which has a similar heating system. What is worse than how the radiator circuit is fed is how the hot water system works. Before those single pipe can get to the radiator they are first pumped through an exchanger coil in the hot tank in the "hot press" cupboard. So whether you wanted hot water or not you are still exchanging the heat into it. The hot tanks are insulated, but that doesn't go very far.If you DO want hot water, even to wash the dishes you have three choices, use the kettle, run the heating for 45 minutes to an hour to heat the hot tank (as well as the radiator circuit which would be a waste in summer) or turn the immersion heater on for at least 20 minutes and I'm sure some of that leaks into the radiator circuit in the water and copper piping.Currently I live in an appartment build in 2004 to high insulation standards with a gas combi boiler which can heat hot water and radiators completely separately. Hot water is instant and only runs the boiler when the tap/shower is on.I am already planning to upgrade the new house built in the 1970s, to a gas fired combi boiler, but at a cost of £3,000-5,000, in addition to renewing the insulation standard.

author: richard.cs
author_rank: Super Contributor
timestamp: March 22, 2019, 09:23:19 am
content: Quote from: paulca on March 22, 2019, 08:31:08 amThat system is very unusual (at least in the UK), are you totally sure that's how it's plumbed? Much more common is having the hot water tank thermosiphon off the boiler then have the radiators in parallel with it but pumped. You get either hot water or hot water and radiators, but can't do heating without hot water. By the '70s single-pipe was nearly dead, mine is oddball enough, something like yours is pretty much unheard of, especially post-war.You could almost certainly rearrange the plumbing to allow independent control of hot water and heating for much lower cost than a new boiler, I suspect easily sub-£1000.

author: paulca
author_rank: Super Contributor
timestamp: March 22, 2019, 03:02:45 pm
content: Yea, fairly sure it has a single pipe in and single pipe out. You may be right the hot tank might be in parallel but I'm pretty certain it only has a single "ON/OFF" function for the boiler, although I haven't checked that closely.Other houses I have lived in with oil fired heating have been the same, just an ON/OFF for radiators and hot water. Was the same for coal fired heating in the 80s.If I managed to get my offer accepted I'll know more, but I fully intent to modernise the energy rating and heating in the house to gas fired combi system. Looks like with government incentives it could be much cheaper than the worst case 2-3k.

author: richard.cs
author_rank: Super Contributor
timestamp: March 22, 2019, 04:56:37 pm
content: Quote from: paulca on March 22, 2019, 03:02:45 pmSure, although combis are not the best solution for everyone, depending on the house and the usage patterns.Back on topic for this thread you could even have a heat pump, especially if you're ripping everything out and re-plumbing anyway. The economics depend a lot on what you expect the relative prices of electricity and gas to do in the future, a few posts back we got numbers for current UK prices that make it slightly cheaper to run ground-source heat pumps than gas boilers especially when coupled to underfloor heating.

author: paulca
author_rank: Super Contributor
timestamp: March 22, 2019, 05:12:23 pm
content: Quote from: richard.cs on March 22, 2019, 04:56:37 pmI expect due to the age of the house (even with improved insulation) the ROI on the heat pump might not be viable. Unless as you suggest the government start ramping up the price of gas, which is plausible in the next decade.

author: IanB
author_rank: Super Contributor
timestamp: March 22, 2019, 05:26:00 pm
content: Quote from: paulca on March 22, 2019, 03:02:45 pmA system I am familiar with has separate timers and on/off controls for heating and for hot water. There is a circulating pump followed by diverter valves to feed the output from the boiler either to the radiators, or to the hot water tank, or to both. Obviously in the summer you don't want the radiators on, so the system can provide hot water alone without heating. There are also thermostats for the house and for the hot water, so even if the hot water is "on" by the timer, the tank thermostat will turn off the water heating when there is no demand for hot water. The boiler only runs when there is either hot water demand, or heating demand, or both.

author: IanB
author_rank: Super Contributor
timestamp: March 22, 2019, 05:30:15 pm
content: Quote from: paulca on March 22, 2019, 08:31:08 amThat's a new one on me. I've never heard it called that before. It's always been the airing cupboard.

author: nctnico
author_rank: Super Contributor
timestamp: March 22, 2019, 05:40:16 pm
content: Quote from: paulca on March 16, 2019, 12:52:56 pmAs usual thinking in terms on efficiency isn't getting people anywhere.The trick of a heat pump is that it moves more energy than it consumes. This is specified as the COP value. For example: if you put 1kW of energy into a heat pump with a COP of 2.5 you'll get 2.5kW worth of heat moved using that 1kW of electricity. For an electric heater you'd have to burn 2.5kW/0.4 (power plant efficiency)=6.25kW worth of fuel (gas/coal/whatever). A gas boiler needs to burn around 2.5kW/0.95=26kW worth of fuel. Using the heat pump you have to burn 1kW/0.4=2.5kW worth of fuel. And that is where the savings are coming from when using heat pumps. In theory. In practise you'll have to be very careful to check whether a heat pump delivers the COP value in the operating temperature range you need it the most. Quite often the name plate COP value is the most optimal one. The example also shows that you'll need a heat pump with a COP well over 3 over the entire operating temperature range to make a significant difference in CO2 output.

author: paulca
author_rank: Super Contributor
timestamp: March 22, 2019, 05:54:56 pm
content: Quote from: nctnico on March 22, 2019, 05:40:16 pmYes and at 30% efficiency at the generation/distribution end that works out as 75% net "efficiency". Still less efficient than a gas boiler, though not be much.

author: james_s
author_rank: Super Contributor
timestamp: March 22, 2019, 06:09:57 pm
content: There are significant losses in transporting the gas too, although I have no idea what the actual numbers add up to. Natural gas pipelines use large gas turbine powered compressors which burn some of the gas in order to compress the remaining gas into the pipeline. The LM1500 is one such popular engine, developing around 15,000 horsepower so not an insignificant amount of fuel burn.

author: apis
author_rank: Super Contributor
timestamp: March 22, 2019, 06:31:29 pm
content: The pipelines are the most efficient part of the transportation chain from the source which is typicallyimportedfrom far away.LNG isn't as good as it might seem(compared to oil) when it comes to greenhouse gas reductions if you consider the whole production and supply chain because there is a lot of leakage of methane which is a much more potent greenhouse gas than CO2.(And whenever you burn something you also get air-pollution, more the more inefficient which usually isn't as good at small scale).

author: nctnico
author_rank: Super Contributor
timestamp: March 22, 2019, 06:44:04 pm
content: Quote from: paulca on March 22, 2019, 05:54:56 pmI don't think this shifting of numbers adds anything to the discussion. I already wrote that a COP of 2.5 isn't going to beat a gas boiler by a great margin. The bottom line is that heat pumps can move more energy than they consume. Whether that leads to a reduction of CO2 and costs depends entirely on the situation.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 22, 2019, 10:50:55 pm
content: Quote from: paulca on March 22, 2019, 05:54:56 pmThere have been attempts at making gas powered heat pumps, the problem is that the absorption cycle is very inefficient compared to electric heat pumps, plus it uses highly toxic ammonia as the refrigerant. Running an electric heat pump from a generator ends up with similar efficiency and much more flexibility, and then you can recover the waste heat from the engine to get way ahead in overall efficiency for heating. Or use the heat to run a desiccant cycle dehumidifier during the summer.

author: james_s
author_rank: Super Contributor
timestamp: March 22, 2019, 11:06:42 pm
content: The idea of running an electric heat pump from a generator never occurred to me. When the goal is to make heat, an internal combustion engine burning natural gas could be quite efficient. A liquid cooled engine would make it easy to extract the heat and move it indoors where you want it, with some of the electricity produced powering a heat pump to get additional heat into the house. Maintenance of a piston engine would likely kill the overall practicality of the project other than for emergency use and small gas turbines while requiring much less maintenance are far more expensive and tend to be inefficient outside of a very narrow band near full throttle.As far as natural gas being imported, that depends on where you are. Here in the US we produce quite a bit of the gas we consume. Obviously the further you are from the source, the less efficient it will be, that applies to any fuel.

author: coppice
author_rank: Super Contributor
timestamp: March 22, 2019, 11:39:04 pm
content: Quote from: NiHaoMike on March 22, 2019, 10:50:55 pmThere are commercial methane powered heat pumps with claim a COP of 2.5 to 3. These don't use ammonia, but I am not clear what they do use.

author: nctnico
author_rank: Super Contributor
timestamp: March 22, 2019, 11:43:47 pm
content: Quote from: james_s on March 22, 2019, 11:06:42 pmLet me stop you right there. These systems aren't fantasies but already widely used to heat large (apartments) buildings and companies. A gas turbine drives a generator to produce electricity (which feeds back into the grid or for whatever electricity is needed) and the residual heat is used for heating. The economics are very favourable. This also works on a large (city wide) scale. For example: my own home is heated from residual heat from a power plant for over 2 decades already. Cost wise it doesn't make sense for me to get an electric heat pump.

author: apis
author_rank: Super Contributor
timestamp: March 22, 2019, 11:44:14 pm
content: I just mean you have to look at the entire life-cycle if you want to compare environmental impact. In car-fuel terms, a well-to-wheel analysis.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 23, 2019, 01:12:19 am
content: Quote from: coppice on March 22, 2019, 11:39:04 pmI wouldn't be surprised if they're just electric heat pumps combined with generators. Or maybe fuel cells.

author: IanB
author_rank: Super Contributor
timestamp: March 23, 2019, 01:18:53 am
content: Quote from: james_s on March 22, 2019, 11:06:42 pmWhy go through the extra steps of generating electricity to run a motor to drive a compressor, when the compressor could be driven directly by the gas engine and avoid the whole generator/motor piece?

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 23, 2019, 02:14:35 am
content: Quote from: IanB on March 23, 2019, 01:18:53 amEasier said than done to seal the refrigerant inside, there's a reason why hermetic compressors have been the norm for decades.

author: wraper
author_rank: Unknown
timestamp: March 23, 2019, 02:20:43 am
content: Quote from: IanB on March 23, 2019, 01:18:53 amRefrigerants are extremely leaky. They will happily leak through any seal.

author: james_s
author_rank: Super Contributor
timestamp: March 23, 2019, 03:43:24 am
content: Well they do make semi-hermetic compressors that are belt driven, I've seen them used in very large refrigeration systems like AC units for shopping malls and movie theaters or huge walk-in freezers like you'd find in a meat packing plant.The reason for using electricity is that it is assumed that the electricity would do other things, like power the electric loads in the house including the fan in the air handler.

author: george80
author_rank: Regular Contributor
timestamp: March 23, 2019, 03:40:48 pm
content: Quote from: NiHaoMike on March 23, 2019, 02:14:35 amQuote from: wraper on March 23, 2019, 02:20:43 amOh FFS!Where do people come up with this shit??What the hell do you think is under the bonnet of every car and has been in at least some for 50 Freaking years?A belt driven Refrigeration compressor for the AC.The seals last just fine and by law in about every country are not allowed to leak refrigerant into the atmosphere.I have set up car AC systems driven by a small Diesel engine. Just took the system out the car, extended the High and Low side Pipes with copper which I used normal AC line insulation for and put a thermostat on the evaporator to cut the compressor as the normal cut out for icing was controlled by the cars computer and another inline for internal temp control. This was also hooked to the engine through a solenoid on the engine so it went to idle when the AC clutch cut out. The signal went through a 10 sec relay to the clutch so the engine had time to come back up to revs before the compressor load dropped back in. Cutout was instant.As I have done with all my vehicles, Instead of R134a I used regular LPG. Works like a charm and is cold as Charity. ( and I'll wait for the comments on that!Instead of charging by weight as normal with refrigerants I charged by pressure ( around half on 134a) but it's easy to " tune" by measuring the outlet temp from the evaporator as would normally be checked anyway. Add in plenty of oil and all is good.A decent size vehicle AC has about the same BTU capacity as a mid size domestic split system so they are far from weak.For heating all that would need to be done would be to put the condenser in the home and put the evaporator outside. Could use the normal coils just reverse positioning to make packaging easier.It would be a waste not to put in a normal reversing valve from a domestic AC which are readily available as spare parts so the unit could heat in winter and cool in summer.The advantage of an engine driven AC as a heat pump would be you could direct the cooling air and exhaust through the evaporator coils to bump the efficiency hugely. Instead of that 30% energy as heat being wasted, it could now be utilized going back to the Home or space. This would be a massive benefit in very cold temps below about 5 oC as it would allow the unit to operate on a much more efficient curve and prevent Icing problems of the evaporator. As the evaporator is not size specific, One could get a larger Condenser off a domestic unit which would allow better heat transfer still though larger surface area and allow the use of a lower powered fan if that was needed at all. Exhaust gas and sealing and ducting the Inlet side of the air cooled engine so as to set ap a positive pressure exhausting through the condenser would probably be more than enough.As said, large commercial AC compressors are nearly all belt driven over a certain capacity and are usually reciprocating Piston types in multi cylinder configurations. Been used for years and give many years of service without leakage which is almost always from the pipes and joints when they do occur.It really would be best if people did know what they were talking about before they proved their ignorance.

author: james_s
author_rank: Super Contributor
timestamp: March 23, 2019, 04:24:58 pm
content: Car AC systems are notoriously leaky, in every car I've ever owned the AC system was dead by the time I got it and I had to replace some seals and recharge it. If it goes 10 years without leaking out the refrigerant charge you're doing pretty well. That's not to say refrigerant is particularly leaky stuff, but it is a gas at atmospheric conditions, is pressurized in the system and there isn't a whole lot of it in a typical car AC system. You typically have at least half a dozen fittings and a seal on the compressor shaft so there are ample opportunities for leaks to form.Fully hermetic systems on the other hand very rarely leak at all, I've seen it twice, once in a domestic heat pump where the discharge line from the compressor was contacting a bracket and vibration eventually wore a small hole. The other was a refrigerated air dryer on an industrial compressor where the high side over-pressure switch came apart and dumped the charge.

author: nctnico
author_rank: Super Contributor
timestamp: March 24, 2019, 12:42:47 am
content: Quote from: james_s on March 23, 2019, 04:24:58 pmExactly! On every car I have owned so far the AC needed refilling every 4 to 5 years due to lack of refrigerant (which obviously leaked away somehow).

author: george80
author_rank: Regular Contributor
timestamp: March 24, 2019, 11:31:34 am
content: Quote from: nctnico on March 24, 2019, 12:42:47 amDo you even know what point you are trying to argue here?

author: ahbushnell
author_rank: Frequent Contributor
timestamp: March 24, 2019, 04:29:14 pm
content: Quote from: george80 on March 24, 2019, 11:31:34 amWe have determined that AC systems leak.

author: george80
author_rank: Regular Contributor
timestamp: March 24, 2019, 08:30:19 pm
content: Quote from: ahbushnell on March 24, 2019, 04:29:14 pmBut not where from.The claim was made that Refrigerant leaks from and could not be contained by seals.That is complete and utter BS.Car systems I used as an example leak from a number of places and the seals of the compressor are vary rare ones. They have many joints and are subject to a LOT of vibration. It has been well known for years that AC compressors should be operated regularly but there will be those that neglect such Maintenance and then use that improper operation to claim that something is faulty.For those looking for an argument, look up the facts and then come argue, don't think because that's the opinion you have it's fact.Lots of hermetic systems leak and run out of gas too because it's not the compressor type that is the problem, it's the Joints in the pipe and everything else attached.

author: nimish
author_rank: Regular Contributor
timestamp: April 05, 2019, 12:09:27 am
content: Quote from: paulca on March 22, 2019, 05:54:56 pm30% efficiency? CCGTs get 60%. Thermal coal plants are dead and dying due to fixed costs + immense pollution. Coupled with renewable power (90+%, effectively) which gets cheaper over time, it's a no-brainer for anyone who isn't already gas connected to switch.Distribution losses are ~10%.Heat pumps, for the UK climate, are the right choice. Gas is a dangerous anachronism.

author: grifftech
author_rank: Frequent Contributor
timestamp: April 05, 2019, 03:10:49 pm
content: the gap between the paines of glass is often air or argon