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Thread: Heat Pump Question

  1. #91
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    Quote Originally Posted by kzb View Post
    Actually 20 minutes after I wrote that, I realised that in that equation the only energy is coming from the compressor. If that equation was correct, there could be no heat pumping. Getting back to expanding the compressed cooled air will cool it below the temperature it started with, that still seems to imply heat must be pumped somehow.

    Also I don't know if phase change is essential. You still have to do work on the vapour to turn it into a liquid.
    Yes but you can liquify at quite low pressue and near constant temperature. Then the heat released was taken from outside by the evaporator heat exchanger, an extra component with no equivalent in a simple compressor. Modern heat pumps also de-ice themselves in air types.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by profloater View Post
    Yes sure, but as you say, not effective for home heating. A Stirling engine is heat made to work at near Carnot, , not work to heat.
    If you have compressed air, yes, you can get work or indeed cryogenic cooling. These examples are heaters or coolers but not heat pumps. Heat pump is a very particular description with COP over 1, otherwise you can get heating with COP equals 1.
    in the compressor example we assume an electric motor and if you have that, you can do other electrically powered tasks. If your primary source is a fuel, you might use a compressor for convenience rather than burning for heat. You can make a heat pump work fired by gas for example, but it is still using latent heat.
    Well look at this ! Any comment?

    https://thermopedia.com/content/837/

    Quote (my bold):

    <<Air-Cycle Heat Pumps
    Consider a system in which both heating and cooling are needed simultaneously. Perhaps a restaurant wants to heat 20C incoming city water up to 82 C for dishwashing. Simultaneously, they would like to air-condition the kitchen. Assume that the outside air temperature is 25C. If outside air at atmospheric pressure is compared with a 1.8:1 pressure ratio, the discharge temperature will be about 89C. This is sufficient to heat the water to the required temperature using an appropriate heat exchanger. In heating the water, the compressed air is cooled to a lower temperature. If the compressed air is now expanded in the turbine back to atmospheric pressure, it will discharge at a temperature substantially below freezing–assuming that the air was dry and no condensation occurred. This is well below the temperature required for air conditioning and so the air will be mixed with room air before being discharged. The air remains breathable as there is no lubricating oil in the system to contaminate it. It is difficult to present a comparison with conventional equipment because the air cycle heat pump is not yet in production and it must be matched against a wide range of combinations of heating and cooling equipment. COP heating values, however, of between 1.9 and 3.6 are expected.>>

  3. #93
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    Quote Originally Posted by kzb View Post
    ...assuming that the air was dry and no condensation occurred.
    Which of course, it won't be. Contaminants including water are an issue with open-cycle systems that a closed circuit heat recovery chiller doesn't have to deal with. I think you need 2:1 to get 89C, not 1.8:1.

    Working with a gas without phase change, you need bulky ductwork instead of a little pipe. My back of the napkin scribble is 350 mm duct on the low pressure section for just 10 LPM of water heating and ~44 kW of heat transfer. Plus a huge heat exchanger to get enough surface area to transfer from the working fluid (air) to the water. Again, no laws of physics broken, just not a solution that will be competitive with the systems that already exist.

    The thermodynamic performance limit on the system described is a COP of 5.25 (again, ignoring condensation), so yes I would guess it would be technically feasible to build a real system with a COP of 3.6 if cost and size were unlimited.

  4. #94
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    Quote Originally Posted by kzb View Post
    Well look at this ! Any comment?

    https://thermopedia.com/content/837/

    Quote (my bold):

    <<Air-Cycle Heat Pumps
    Consider a system in which both heating and cooling are needed simultaneously. Perhaps a restaurant wants to heat 20C incoming city water up to 82 C for dishwashing. Simultaneously, they would like to air-condition the kitchen. Assume that the outside air temperature is 25C. If outside air at atmospheric pressure is compared with a 1.8:1 pressure ratio, the discharge temperature will be about 89C. This is sufficient to heat the water to the required temperature using an appropriate heat exchanger. In heating the water, the compressed air is cooled to a lower temperature. If the compressed air is now expanded in the turbine back to atmospheric pressure, it will discharge at a temperature substantially below freezing–assuming that the air was dry and no condensation occurred. This is well below the temperature required for air conditioning and so the air will be mixed with room air before being discharged. The air remains breathable as there is no lubricating oil in the system to contaminate it. It is difficult to present a comparison with conventional equipment because the air cycle heat pump is not yet in production and it must be matched against a wide range of combinations of heating and cooling equipment. COP heating values, however, of between 1.9 and 3.6 are expected.>>
    The wrong part is that the compressed air is released into the kitchen. The net effect is heating even though the compressed air is cooled, although not by much. Remember in this scheme the compressed air is used to heat hot water so it is not cooled much and not much heat is added to the water. He says 80 c in the worked example so the compressed air is above 80 when released. The work done on the air is turned into heat in the kitchen, not cooling. It is a false scheme.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  5. #95
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    The specific heat of air is about 1 versus water at 4.2 kJ/kgK. But the density of air is about 800 times less. So imagine the ratio of air to water to get hot water in volume terms. It is in thousands. Before when venting to atmos you wasted the work done now you get it back as heat in the confined space. So net heating maybe nearly a cop of 1 but never higher. And the kitchen just gets hotter from the outside 25 c air. Pointless when water can be heated directly at 100% and conventional aircon will cool the kitchen.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by profloater View Post
    The wrong part is that the compressed air is released into the kitchen. The net effect is heating even though the compressed air is cooled, although not by much. Remember in this scheme the compressed air is used to heat hot water so it is not cooled much and not much heat is added to the water. He says 80 c in the worked example so the compressed air is above 80 when released. The work done on the air is turned into heat in the kitchen, not cooling. It is a false scheme.
    In a counter flow heat exchanger, you can (and quite often do) get your hot fluid leaving temperature below the cold fluid leaving temperature. So before it is expanded, the air will be a little warmer than the incoming water temperature, maybe 25C (I see 0.5C approaches in real-world heat recovery HXs, though that is for liquid-liquid plate and frame units). The net effect is heat transfer from the kitchen into the the dish washing water along with the work to run the compressor. That's why the COP is >1. The air is no longer compressed when it is released since it has been expanded back across a turbine, it is back to 1 bar and somewhere around -20C. Again, there's nothing wrong with the physics here, it just isn't a practical heat pump.

  7. #97
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    Quote Originally Posted by VQkr View Post
    In a counter flow heat exchanger, you can (and quite often do) get your hot fluid leaving temperature below the cold fluid leaving temperature. So before it is expanded, the air will be a little warmer than the incoming water temperature, maybe 25C (I see 0.5C approaches in real-world heat recovery HXs, though that is for liquid-liquid plate and frame units). The net effect is heat transfer from the kitchen into the the dish washing water along with the work to run the compressor. That's why the COP is >1. The air is no longer compressed when it is released since it has been expanded back across a turbine, it is back to 1 bar and somewhere around -20C. Again, there's nothing wrong with the physics here, it just isn't a practical heat pump.
    Ok what is the turbine doing? If that work can assist the compressor you edge the COP upwards towards 1, never more without vapours. What is the air to air exchanger doing? Previously you vented the air indoors. Now you vent hot air from the compressor to heat incoming air. That’s fine but it is not a heat pump. You have a glorified heater working a little less effectively that a simple resistance water heater and no useful cooling of the kitchen. All this is why vapour cycles were invented to replace bringing blocks of ice indoors, and ice stores, which were the previous generation. Compressors were invented to make useful high pressure air.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  8. #98
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    Here is the basic problem.. you cannot raise the T of heat without doing work. You can get heat from work, but not all the heat can be turned back to work. To get a heat pump where you push the T up, you must use latent heat or you just have a heater. Scheming without latent heat is like inventing a perpetual motion machine.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  9. #99
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    Quote Originally Posted by profloater View Post
    Ok what is the turbine doing?
    Air cycle systems typically employ turbines instead of an expansion valve because the energy otherwise lost in expansion "back work" is relatively high compared to systems with phase change; on the order of 50%.

    If that work can assist the compressor you edge the COP upwards towards 1, never more without vapours.
    Incorrect. Phase change isn't magic, though it does allow much denser heat transfer.

    What is the air to air exchanger doing?
    There is no air-air HX in the system described. There is a air-liquid HX, used to heat the dishwashing water.

    Now you vent hot air from the compressor to heat incoming air.
    No.

    ...All this is why vapour cycles were invented to replace bringing blocks of ice indoors, and ice stores, which were the previous generation. Compressors were invented to make useful high pressure air.
    I would have to look up the history of refrigeration to see whether vapour refrigerant systems or absorption chillers came first. The former, of course, also uses a compressor. But no, vapour cycles are used because they were and are a much more practical way efficiently chilling something from ambient to cool but not cryo temperatures. You are looking at a choice of a particular technology selected for practical reasons and thinking incorrectly that that has implications on the underlying physics.

    Quote Originally Posted by profloater View Post
    Here is the basic problem. You cannot raise the T of heat without doing work.
    Correct.

    You can get heat from work, but not all the heat can be turned back to work.
    Correct.

    To get a heat pump where you push the T up, you must use latent heat or you just have a heater.
    Incorrect. As already explained, air cycle systems are not only theoretically possible but are technically feasible, and in broad actual use where they make sense to use. It is silly of you to argue something that is commercially available, is impossible.

    Scheming without latent heat is like inventing a perpetual motion machine.
    Incorrect. Air cycle systems are limited by the same Carnot efficiency as a refrigerant cycle. No one here is discussing anything that violates the laws of thermodynamics.

  10. #100
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    Quote Originally Posted by profloater View Post
    The wrong part is that the compressed air is released into the kitchen. The net effect is heating even though the compressed air is cooled, although not by much. Remember in this scheme the compressed air is used to heat hot water so it is not cooled much and not much heat is added to the water. He says 80 c in the worked example so the compressed air is above 80 when released. The work done on the air is turned into heat in the kitchen, not cooling. It is a false scheme.
    It sounds like it could be a nifty piece of kit to me. You don't have to direct the cold air into the kitchen, if you want heating only you would direct the cold air outside the building. In hot weather you can have hot water and cooled rooms by directing the cold air to the inside.



    Now I know the correct term to search for, I've found this:

    https://www.fluidmechanics.co.uk/nea...mp-technology/

    ...a technology that improves the energy efficiency of heat pumps by 50% or more while eliminating the need to use gases with a high global warming potential

    Quotes:

    By applying the near isothermal technology to the Stirling cycle, it is possible to make a heat pump which has similar heating/cooling capacity to the vapour compressor cycle while being significantly more energy efficient.

    ....for example when the external temperature is -5 oC the existing technology will provide a COP of 2.1, the near isothermal heat pump will be 3.8 and the theoretical maximum is 6.4.


    Assuming this isn't a scam, I think you must be incorrect that having a refrigerant liquid/vapour cycle is fundamentally necessary for the thermodynamics of a heat pump.

  11. #101
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    Quote Originally Posted by kzb View Post
    It sounds like it could be a nifty piece of kit to me. You don't have to direct the cold air into the kitchen, if you want heating only you would direct the cold air outside the building. In hot weather you can have hot water and cooled rooms by directing the cold air to the inside.



    Now I know the correct term to search for, I've found this:

    https://www.fluidmechanics.co.uk/nea...mp-technology/

    ...a technology that improves the energy efficiency of heat pumps by 50% or more while eliminating the need to use gases with a high global warming potential

    Quotes:

    By applying the near isothermal technology to the Stirling cycle, it is possible to make a heat pump which has similar heating/cooling capacity to the vapour compressor cycle while being significantly more energy efficient.

    ....for example when the external temperature is -5 oC the existing technology will provide a COP of 2.1, the near isothermal heat pump will be 3.8 and the theoretical maximum is 6.4.


    Assuming this isn't a scam, I think you must be incorrect that having a refrigerant liquid/vapour cycle is fundamentally necessary for the thermodynamics of a heat pump.
    Meh. An enormous amount of time and research has been put into making chillers and heat pumps efficient; I am skeptical that a guy in his garage is going to come up with something that is, all things considered, much better. For example, a new Daikin WMC water-cooled industrial chiller operates at an EER of 6.0 at AHRI conditions, which is 71% of the thermodynamic limit of 8.43 for those conditions. That is a real machine in full production today and that number is a lab-certified performance that includes motor efficiency and operates in a practical, economical cost and footprint. So his expectation of 50-60% of Carnot efficiency is plausible (not a kooky claim; in fact he seems like a guy I'd enjoy having a beer with), but likely not high enough to make up for the disadvantages (particularly cost and power density).

    If you want a heat pump that is super-efficient without using environmentally damaging refrigerants, check out ammonia systems (R-717). The drawback is ammonia is fine for the environment but really bad for the human lung.

    ETA: simultaneous heating and cooling, though, is something that indeed comes up constantly in commercial applications in temperate climates. Mitsubishi HVRF systems are an example of a currently available product designed to move heat around this way. So the air-cycle heat pump would need to compete with products already on the market.
    Last edited by VQkr; 2021-Apr-08 at 08:27 PM.

  12. #102
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    Quote Originally Posted by VQkr View Post
    Which of course, it won't be. Contaminants including water are an issue with open-cycle systems that a closed circuit heat recovery chiller doesn't have to deal with. I think you need 2:1 to get 89C, not 1.8:1.

    Working with a gas without phase change, you need bulky ductwork instead of a little pipe. My back of the napkin scribble is 350 mm duct on the low pressure section for just 10 LPM of water heating and ~44 kW of heat transfer. Plus a huge heat exchanger to get enough surface area to transfer from the working fluid (air) to the water. Again, no laws of physics broken, just not a solution that will be competitive with the systems that already exist.

    The thermodynamic performance limit on the system described is a COP of 5.25 (again, ignoring condensation), so yes I would guess it would be technically feasible to build a real system with a COP of 3.6 if cost and size were unlimited.
    In Britain, people seem to be prescribed 11kW, or perhaps 18kW heat pumps for larger houses. Not 44kW.

    My condensing gas boiler is nominally 30kW and 92% efficient. It has no trouble keeping us warm even in the cold weather we had this January. 11kW would have been miserable but there was no need for 44kW. I also think we are back to hot water storage cylinders with heat pumps, not on-demand, so no need for 10L per minute.

    After 2030 we are not allowed to replace a broken gas boiler, we have to have electric heating, which means a heat pump. With current technology it is terribly expensive both to install and run.

  13. 2021-Apr-08, 08:35 PM

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    Quote Originally Posted by kzb View Post
    In Britain, people seem to be prescribed 11kW, or perhaps 18kW heat pumps for larger houses. Not 44kW.

    My condensing gas boiler is nominally 30kW and 92% efficient. It has no trouble keeping us warm even in the cold weather we had this January. 11kW would have been miserable but there was no need for 44kW. I also think we are back to hot water storage cylinders with heat pumps, not on-demand, so no need for 10L per minute.

    After 2030 we are not allowed to replace a broken gas boiler, we have to have electric heating, which means a heat pump. With current technology it is terribly expensive both to install and run.
    Yes, natural gas is being phased out in parts of the USA as well, for example California (regulations here tend to be fragmented by state). The environmental reasons for phasing out natural gas are sound, but it is indeed a challenge because a boiler is much cheaper to manufacture than a heat pump.

    I was arbitrarily choosing a nice round flow rate number for a commercial kitchen dish washer; obviously it would scale if you are heating a house instead. My professional experience is with commercial and light industrial systems, so a 500 kW chiller would be quite small.

    You are having heat pump problems not because the technology doesn't exist already, but because residential systems tend to focus on first cost rather than efficiency or performance.

  15. #104
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    Yes the stirling cycle is different from using a compressor. The important difference is the two heat exchangers, one of which absorbs heat from the cold source. Compression then heats that so that the hot heat exchanger can deliver into the hotter space. It can theoretically have a high COP although complicated to get in practice, but there has been major progress. It is true this cycle allows a pure gas to be the working fluid.

    When I insisted on latent heat I was referring to the “simple” compressor idea which has no cold source heat exchanger. To use a simple compressor and pressure release cycle, you must have vapour.

    The stirling closed cycle uses two pistons and a heat store or regenerator. At first it had to be a slow engine and the compression done by a linear motor to move one piston. It is a true heat pump because the heat exchanges can be large and allowed to absorb heat with small temperature difference. In theory isothermally although a true isotherm is not practically possible.

    So ideally there is a hot exchanger and a cold exchanger, and when some heat has been absorbed in the cold exchanger you push it doing work with one piston, heating the working gas up by compression and into the hot exchanger. There you wait while it transfers heat , finally expanding again to get the cooling below the T of the cold source.

    The OP scheme which has been the subject, is an open cycle trying to get the work done to make heat with COP over 1.

    The stirling cycle is a genuine heat pump and does not need latent heat to work. Or it is a motor capable of operating with small temperature differences close to the Carnot limit. You are right that I should have mentioned it although practical heat pump domestic heaters are not yet economically comparable to latent heat systems.
    In theory they can do better at COP than latent heat, but that requires comparison of which refrigerant to use, and how to reduce the cost of the sliding pistons and linear motors.
    They tend to be slow as I described and when you speed them up, you lose the difference between hot and cold exchangers.

    These stirling cycle schemes are not easy DIY projects but I am sure there is potential for mass production .
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by profloater View Post
    To use a simple compressor and pressure release cycle, you must have vapour.
    You can keep repeating this but you'll be incorrect every time. Google "air cycle" or pick up a textbook; this is basic stuff. Air cycle heat pumps can be open or closed; either way COP as a heat pump will be >1 unless you have significant amounts heat being wasted through insulation somewhere or something like that. Whether the cold side heat flow is across a HX or mass flow with physical mixing is irrelevant.

    The kitchen heat recovery example linked by the OP was not "trying to get the work done to make heat with COP over 1.", it was pumping heat from the kitchen into the the dishwasher water. With a COP >1.

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    Quote Originally Posted by VQkr View Post
    Yes, natural gas is being phased out in parts of the USA as well, for example California (regulations here tend to be fragmented by state). The environmental reasons for phasing out natural gas are sound, but it is indeed a challenge because a boiler is much cheaper to manufacture than a heat pump.

    I was arbitrarily choosing a nice round flow rate number for a commercial kitchen dish washer; obviously it would scale if you are heating a house instead. My professional experience is with commercial and light industrial systems, so a 500 kW chiller would be quite small.

    You are having heat pump problems not because the technology doesn't exist already, but because residential systems tend to focus on first cost rather than efficiency or performance.
    I can see heat pumps being quite sufficient in the California climate. In areas with harsher winter conditions not so good. The performance and efficiency drops off just when you need it the most, when it is cold outside. It's never really cold in California so you will get a good COP. A bit frustrating that we can only get good heating when it's not cold.

    Looking at what I pay for gas versus electric (i.e fuel costs only), the COP break-even point is 5.44. It would need to be even higher than this if capital cost is included. I don't see any domestic heat pump on the market which claims a COP approaching this. It's a pity because the theoretical COP is obviously quite high and exceeds 5.44 even at minus 5 degrees.

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    Quote Originally Posted by kzb View Post
    I can see heat pumps being quite sufficient in the California climate.
    Depends which California climate we are talking about. It has sixteen climate zones, that vary from subtropical to arid desert to mountains to temperate to marine. For example, the average daily December low for Redding is 2.4C (it is 2.7C for London and 2.3C for Sheffield).

    Looking at what I pay for gas versus electric...
    To satisfy my curiosity, would you be willing to share approximately what you do pay for each?

  19. #108
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    Quote Originally Posted by VQkr View Post
    You can keep repeating this but you'll be incorrect every time. Google "air cycle" or pick up a textbook; this is basic stuff. Air cycle heat pumps can be open or closed; either way COP as a heat pump will be >1 unless you have significant amounts heat being wasted through insulation somewhere or something like that. Whether the cold side heat flow is across a HX or mass flow with physical mixing is irrelevant.

    The kitchen heat recovery example linked by the OP was not "trying to get the work done to make heat with COP over 1.", it was pumping heat from the kitchen into the the dishwasher water. With a COP >1.
    You are right, but to switch from vapour cycle to an air cycle you use a reverse Brayton cycle in which the expansion phase does useful work. The scale of the machinery increases for any given heat output. The normal cycle uses a turbine to drive a compressor and in reverse the shaft of the turbine contributes some of the work of compression. So where a Stirling cycle takes heat in at constant volume, the Reverse Brayton takes heat in at constant Pressure. In both internal heat exchange, Called regeneration is also used to reduce the net work.This is possible in the atmosphere as an open cycle. By using compression nearer to isothermal, the work in is less and by using the expansion work, the net work in is also less.
    So an air cycle device has to be larger and more complex than a vapour cycle device, for the same heat output. The justification then is freedom from refrigerants that , if released form their closed cycle, can damage the ozone layer or contribute to global warming.
    Edit addition: the OP compresser idea with venting is still not a heat pump with useful COP, I regret not thinking to mention reverse Stirling cycles or reverse Brayton cycles because, as you say, these do not need latent heat. But these have moved a long way from the idea of just compressing air and releasing it.
    Last edited by profloater; 2021-Apr-09 at 10:46 AM.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by VQkr View Post
    Depends which California climate we are talking about. It has sixteen climate zones, that vary from subtropical to arid desert to mountains to temperate to marine. For example, the average daily December low for Redding is 2.4C (it is 2.7C for London and 2.3C for Sheffield).



    To satisfy my curiosity, would you be willing to share approximately what you do pay for each?

    Redding looks like it is the California equivalent of Fort William. London and Sheffield together make up nearly a quarter of the entire UK population. Better population-weighted comparison would be LA and Sacramento. Don't get me started on London either, it has a very significant urban heat island effect, and it is where the decisions are made to inflict heat pumps on the rest of us.

    Gas 2.57p/kWh Electric 15.2p/kWh including the 5% VAT.

    At UK/US$ = 1.374 (I've just looked this up on xe.com) that is 3.53 cents/kWh for gas and 20.9 cents/kWh for electric.

    Can you share what these are in California?

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    Quote Originally Posted by kzb View Post
    Redding looks like it is the California equivalent of Fort William. London and Sheffield together make up nearly a quarter of the entire UK population. Better population-weighted comparison would be LA and Sacramento. Don't get me started on London either, it has a very significant urban heat island effect, and it is where the decisions are made to inflict heat pumps on the rest of us.

    Gas 2.57p/kWh Electric 15.2p/kWh including the 5% VAT.

    At UK/US$ = 1.374 (I've just looked this up on xe.com) that is 3.53 cents/kWh for gas and 20.9 cents/kWh for electric.

    Can you share what these are in California?
    Yup, CA's population is centered in sunny LA, man.

    Los Angeles Prices:
    $0.219 / kWh electric
    $0.047 / kWh gas

    Portland, Oregon Prices (possibly a better analogue for GB's climate):
    $0.134 / kWh electric
    $0.035 / kWh gas

  22. #111
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    Quote Originally Posted by VQkr View Post
    Yup, CA's population is centered in sunny LA, man.

    Los Angeles Prices:
    $0.219 / kWh electric
    $0.047 / kWh gas

    Portland, Oregon Prices (possibly a better analogue for GB's climate):
    $0.134 / kWh electric
    $0.035 / kWh gas
    So in LA the break-even COP is 5.1 assuming a gas boiler efficiency of 92%.

    In Portland it is only 4.2.

    Maybe in these climates these COPs are achievable, but from what I've seen I doubt it.

    I suppose we should take into account that air conditioning in LA is likely a bigger consideration than heating, and since there are reversible models of heat pumps, that would be a big point in their favour.

    In cooler climates we really need better COPs than we have now. That gas-cycle model looks very attractive from that point of view.

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    Quote Originally Posted by kzb View Post
    I suppose we should take into account that air conditioning in LA is likely a bigger consideration than heating, and since there are reversible models of heat pumps, that would be a big point in their favour.
    Yes, LA is warmer than Sacramento, sometimes with very warm winter weather (I can’t remember exactly when, but I was there once when it was over 90F in the winter then came home to 40s/50s) but Sacramento also has a fairly short winter. For instance today is to get over 80F (27C). Pretty much everyone in large parts of California has an air conditioner (there are some coastal and mountain areas that don’t get too warm most of the time but are the exception) so it isn’t that big a stretch to install a heat pump instead. It is simply a case where a natural gas heater has typically been seen as cheaper to run and to do a better job for heating.

    By the way, I’m hearing more about geothermal or ground source heat pumps, since most places the temperature underground is much more stable and benign, reducing both heating and cooling costs over air source heat pumps. Here it actually is likely to be more useful for reducing cooling costs.

    Unfortunately, installation is expensive, but getting better with more companies having drilling equipment they use to drill down and install the piping. It can be cheaper for new construction, and some places are starting to build community pipe systems to be shared by multiple houses in new development.

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    The Leif Ericson Cruiser

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