DOE announces breakthrough in residential cold climate heat pump technology
energy.gov
energy.gov
The claims are pretty amazing. High efficiency, efficient over a wide range of temperature difference, high temperature differences possible.
The operating principle is totally different. It is based on acoustic waves. Not using phase-changes but just the ideal gas law (pressure and temperature are proportional). I tried to get my head around it, and I got it with a standing sound wave. But they use a traveling wave, for which I could not find explanations I understood.
The general idea is "lower air pressure and move gas to cold side so the gas heats up" followed by "raise air pressure and move gas to warm side so the gas cools down". That means the low pressure needs to be low enough that the gas gets colder than the cold side, and the high pressure needs to be high enough that the gas gets hotter than the hot side. Luckily that is 'just' a matter of amplitude of the sound wave. I think this is how they achieve their wide range of efficient temperature deltas.
That wide range is the main difference with a phase-change based unit. The phase change happens at a much more difficult to change temperature.
And, even from the perspective of field theory, aren't fields defined by the type of waves moving through them?
I don't think the fields are defined by their waves, but specific fields have specific wave patterns/types
In phase change systems, the 'hot side' and 'cold side' are all at the same temperature, which means any gradient in whatever you are heating/cooling is lost energy.
This sounds like Maxwell's Demon, where the work required to prevent the system from reaching thermodynamic equilibrium is equal to or greater than the extra energy. How does this differ from that?
But we aren't after kinetic energy, or work. We are after heat.
Your idea of 'kinetic energy of the object as a whole' is probably quite close.
If only we'd painted these roofs with white reflective roof paint (~92% reflection). We would have removed ~8kW of heating from such roofs! And then, maybe, we wouldn't have to pump all that energy into air-conditioning. So the surrounding air would be cooler, less noise would be heard from air conditioning, less energy would be spent. And the cost? 4 gallons of white reflective paint and a couple of hours of work, painting the roof...
I think the US is fairly unique in that regard. I’m so used to our houses here that the idea of using shingles made of asphalt just seems bizarre to me.
Asphalt tiles are fairly cheap, and that's a good thing. It's the labor that makes up most of the cost of a roof.
I'm trying to get up the nerve to shingle my four bedroom home, and it's not the cost of materials I'm worried about. It's my body.
My fear with global warming measures is the poor, and middle class, will be required to bear the brunt of the preventative measures.
I guess the race is on to develop a 50 year life expectancy, but reasonably priced, white shingle? They might be out there? I really haven't researched them.
If anyone knows a cheap roofing contractor in the Bay Area, please divulge?
Twenty years ago I had a estimate of $25,000. I think that's too much now. I'm a ex General Contractor.
They'll also bear the brunt of the effects of global warming, and those will be worse.
We should try to make environmental programs as equitable as possible. But first and foremost we need to do them!
I see a lot of virtue signaling out there.
Most of us can't afford a electric vechicle, and those federal credits seemed to just go to people whom could afford any vechicle.
I can't even afford the smog check, and registration, on my 4 banger toyota. A Truck I've keep going 20 years. It uses very little gas. (My vechicle has always been tuned up properly. I thought by now we would have had free smog checks for the poor? In CA we have a low income deal that was enacted when CA decided to require smog checks. It's so complicated most people don't use the "gift". You need to bring your car to a mechanic in order to get any money back. Shade Tree mechanics are out of luck.
My point is the corporations/government will pass any Global Warning measures down to us.
We are already tapped out.
If we are really serious about Global Warming lets go after the wealthy boys first. Take away their private jets.
And enough with their Globalization. If they can make a product that dosen't need to be shipped long distances, have them make it here.
I'm a Democrat, and winced when Biden pretty much gave a FY to the oil companies in order to sound Progressive. I knew at the time, the poor can't afford to pay more for gas, and natural gas.
Now--I don't blame the president for this spike in gas prices, but I would have rather have him say this is a big problem, and we can't just do away with oil.
Be it my PG&E bill that just seems to go up, and the $6.69 gas at my Chevron station, the poor are already paying to much of their income on a complex problem. (My gas station raised their prices the minute they started talking about inflation, and the Russia sanctions. It is pure greed. They made a record profits in the past few years.
Sorry about my rant. I just don't like being squeezed so much, while my wealthy neighbors buy crap from Amazon, and think they are doing their part by driving a Tesla.
So, fear not, a couple more years and you will be smog exempt.
While I'm on my soap box; Neusome (a guy I went to high school with (Redwood, and voted most Fashionable, a liberal Marin county boy) has a bill on his desk that would do away with fees associated with Parking Tickets. As of today, he has not signed off on it. The only reason I can think of is he's getting more middle of the road for a run at the big office?
These extra fees and fines are not fair to the poor. A parking ticket in SF is running $80 bucks without fines. $5-6 an hour if you find the right spot. Neusome knows this personally.
He barely graduated from Redwood High School, and dropped out of college due to some nebulous learning disability. He opened some coke dens in SF, and a few Bootjack liquor stores with family money. The SF bars went up in flames because they were poorly managed. Oh yea, his cousin Brendan has a DUI that disappeared? I might write a book on this guy one day. While I seem pissed, he's better than the alternatives.
If he wasn't born wealthy, he would be in the Embarcadero in SF with a needle stuck in his arm.
Government will pass climate change measures on to those that squeal the quietest.
Globalization is not the cause of climate change, it's a natural effect of economics as our technology and capabilities improve.
No one is saying to do away with oil, but that also means that oil companies don't have a social license to extract excessive profit. So tax them.
I once knew a handyman that swore by painting over black membrane roofs with some sort of white rubber patch paint. It was probably a terrible idea, but I wonder if such a product exists for asphalt roofs.
Make sure you invest in a proper safety harness, they're not that expensive and even if I really hope you won't need it you'll be very happy you did that in case you do...
On the days when there is an inversion in the atmosphere, the hot air stays trapped. People have to run ACs in their houses, stores and offices. And that results in even more heat routed to the place, with ACs units, literally pumping energy from the solar arrays somewhere in the desert into the city.
So effectively, in the suburban area there is an opportunity to change our average solar reflectance by ~32% [(90% - 10%) * 40%]. If we just abandon the idea that a good house should look like a house in Normandy and have a black roof.
[edit: I've opened a section of sat map (in Sunnyvale, near Reed Ave/Sequoia Dr.) and estimated roof/street/backyard/front-yard by area, for a lot of 2 houses and adjacent street. The numbers above are from that estimate. Heat and noise of ACs is somewhat local (urban heat island effect, etc), so that local estimate is what counts. It is not surprising that we can have 40% roofs. Land is expensive in the suburb like that.]
As per: https://en.m.wikipedia.org/wiki/Reflective_surfaces_(climate... - "If all urban, flat roofs in warm climates were whitened, the resulting 10% increase in global reflectivity would offset the warming effect of 24 gigatonnes of greenhouse gas emissions, or equivalent to taking 300 million cars off the road for 20 years. So it seems, there is not only local/urban heat island effect, but even some global effect. To put this into perspective, Tesla sold 2 million vehicles. No idea, if the Wiki numbers are correct...
Even if houses were 50% of the land area, they take up a miniscule amount of air volume. Also, hot air floats up, so there is little chance you could feel the heat from an AC outside. On the other hand, if the earth is hot because you have few trees, you will feel it everywhere when walking on a sidewalk.
In Europe at least it’s common knowledge that you need to have trees and greenery everywhere to make heat bearable outside. If you replace trees and grass with concrete you get an island of heat that will be unbearable during summer to walk through.
edit: thermal camera image of a walkway with trees in summer https://images.app.goo.gl/m2XN7rqodavDcwoE9
Much cooler temperatures (13°C) are found just a few feet below ground. (Memorable to those who've visited 'root cellars.) Before long those mysterious 'underground cities' in Anatolia may not seem so mysterious. It's a low-cost, low-tech, zero-energy solution, used by native communities in many regions of the world.
When the London metro was built (over a century ago), the clay was at 14 degrees C. But over time, it heated up from all the power dissipated by the metro system. Now it is around 20 to 25 degrees C and doesn't really act as a heat sink anymore. The same happened in the NY subway.
So soil can act as a great heat sink for a while, but not forever. I suspect the same would happen if you'd put a modern city underground and relied on the temperature of the soil instead of pumping heat out somehow.
This is an old school carpentry trope and yet I've never actually seen any statistical evidence indicating that roofs over vaulted ceilings which are directly insulated must be replaced more often than non-vaulted.
And nearly every roof ive worked on that had curled shingles lacked proper roof ventilation. That isn't direct evidence, but ive never seen curled shingles on a well ventilated roof either and the only common factor in curled shingles is heat buildup in the attic/roof cavity.
An unconditioned attic is not so great because it’s difficult or impossible to do a good job of avoiding leakage into the living space. Also, any mechanical equipment in the attic would like to be in conditioned space.
P.S. - If you look into the white paint thing more carefully you'll be rather disappointed.
Given it's a once off cost it seems like this should be doable.
I take your point, I’m doing it anyway.
But, I was also considering having a 10kW battery to store that energy and to have a backup power, like Tesla Powerwall - $10k. And then there was work to install, permits, my time. Overall my estimate was, realistically it'd be ~$25k. Maybe I was wrong.
On my house I have two sections of roof that are flat/horizontal. Roof is pretty thin there and although there is insulation, on hot days ceiling was getting worm in the 2 rooms under these sections. I also was hoping that an extra layer of solar would insulate my roof a bit more. So I wouldn't have to run AC that much. So the hope was to stop wasting annoying $400 on AC in the hottest months. But the cost of installing solar felt prohibitive. So I've made a quick calculation and spent $100 on the reflective roof paint instead...
5kWh battery thing for $1,500: https://signaturesolar.com/eg4-lifepower4-lithium-battery-48...
Growatt 3kW Stackable Off-Grid Inverter for $700: https://signaturesolar.com/growatt-48v-3kw-150vdc-stackable-...
Solar panels are $2-$3 per watt depending where you live. 4x300watt panels is just the ticket, depending where you are and whether you can get a 30% tax credit that's about $2000.
Whole thing all together would be about $5000. It would generate about $1 of electricity a day. Would eventually pay for itself over its lifetime if you don't mind faffing about with it to get started.
> On my house I have two sections of roof that are flat/horizontal. Roof is pretty thin there and although there is insulation, on hot days ceiling was getting worm in the 2 rooms under these sections. I also was hoping that an extra layer of solar would insulate my roof a bit more.
It will be slightly cooler underneath it.
After those 14 years, you “make” an annual non-compounded 7% ROI (again in 2022 dollars).
Spending some of that money on insulation and sticking the rest in a savings account somewhere is a much wiser bet.
Every time I do the calculations, it’s money loss.
If you want to install them for environmental reasons, great. But don’t kid yourself that’s is a great investment. It’s not. Putting the money into an S&P 500 index fund for 14 years is a better investment. It will double about twice in that time.
As for why do it, well, a right sized system allows you to be independent from the utility company so if monthly financing for it falls to the same ball park you're paying for electricity already you've simply locked in a rate and hedged against further price hikes.
If I was paying on average $99/mo to PG&E or whomever I'd eyeball a $12,000 system financed over 10 years. That would get you about 20kWh storage and enough panels to keep it full which may or may not be enough for your house.
That crossover point obviously varies from house to house and what's available to you locally. I think it makes a lot of sense for new houses, that way they might avoid a potentially very costly hookup to the grid which in some locations is tens of thousands of dollars in itself.
Remember to take 23% off for the federal tax credit.
> But, I was also considering having a 10kW battery to store that energy and to have a backup power, like Tesla Powerwall - $10k.
That's a not-so-small detail, accounting for $18.5k of the bid! A battery is also pretty unhelpful for reducing the A/C portion of your electric bill, especially since most traditional A/Cs require more than the 20A that the Enphase 10kWh battery can output and will pretty quickly drain any home backup battery that could support that current demand.
> So I've made a quick calculation and spent $100 on the reflective roof paint instead...
$100 in reflective roof paint, while a great measure to take, isn't going to reduce A/C electricity usage more than PV, which has the added benefit of offsetting your other electricity usage when you are not in the cooling season.
It can definitely run our 60+ amp HVAC system, but not overnight. (We didn't buy it for that, but it's nice that we don't even notice our frequent, short outages until enphase and pg&e email us...)
I read the national average recently spiked up to $3.10, thanks to the Biden administration's mishandling of Trump's China Tariffs.
We have about 2.5 watt hours of battery per watt of solar panel, which seems about right around here. (The battery is fully charged by the end of day about 95% of the time.)
Your quote has 6.6 Wh/W, and the PV bit is small, so fixed costs are also biting you.
Edit: we have electric heat, and you probably don't. Our worst case days are cold and cloudy, so perhaps the battery sizing makes sense, though if you want AC at night, you'll want enough solar panels to charge the battery and run the AC.
However, it was not trouble free:
The time of day scheduling feature is useless. Once or twice a month it gets stuck in "lower temp" mode. The app reports kWh used and displays alerts, which is nice. Otherwise, there's no reason to give it WiFi access.
Pay for the leak detector option. It's relatively cheap, but not included for some reason.
You're likely to have condensation issues unless you use a good installer, or do it yourself and follow directions.
The power lead on ours wore through due to vibration too, so pick someone that's experienced/conscientious enough to route wires carefully.
My dad gets about 6 kWh daily during the summer from an 1140 Wp PV array. 45° latitude, 1250 W/m² yearly insolation.
Also, don't unferestimate painting a roof. I recently had my ~400m^2 roof painted, and the final bill was 50k ZAR (~3k USD), and this is in a country with dirt cheap manual labour costs. It's a very labour intensive operation if done properly.
1 - https://www.sustainable.co.za/collections/grid-tied-solar-po...
I'm almost certain that putting the money that they cost into making my home more efficient in the first place, by doing things like sealing leaks, upgrading the insulation, and, yes, making the roof a lighter color, would have reduced our energy consumption by more than the amount that the PVs are generating.
The PVs absorb a lot of thermal energy, too, more than the shingles themselves do. So they make the roof hot. You can actually feel the difference inside the house - the rooms that are underneath the solar panels get warmer in the summer than the ones that aren't. So some amount of that electricity we're generating would seem to just be undoing the effects of the PVs on the house's thermal situation. There's still a net benefit, but probably because we're people who are inclined to accept that summer is hot in the first place. Trying to keep those rooms at or below 80F/26C might be an expensive endeavor.
Also, I've discovered that one does not simply have a roof leak fixed when there are solar panels on the roof, because they are in the way. So maintenance has been rather more expensive than I expected.
In general, I'm sanguine about solar as a renewable option. I'm just increasingly inclined to believe it's better implemented as an industrial technology, and that homeowners probably have better options for greening their houses.
I've found this to be interesting going back as far as middle school, where we're taught renewable energy sources like solar panels can help reduce global warming by replacing greenhouse gas emitting alternatives. Yet fundamentally, they are designed to turn the only external source of energy our planet receives (sun light) into heat and other forms of energy that will eventually become heat rather than reflecting it back out into space (albeit through the atmosphere). Seems so backwards to me.
https://eoimages.gsfc.nasa.gov/images/imagerecords/85000/854...
How does a steam turbine work? By heat: we burn things to get heat, and use steam to turn it into work which..turns it into heat.
Your own statement is arguing against using energy in the first place, yet trying to frame it as a "renewable energy" problem as though the 60% of energy in gasoline isn't being thrown off into the environment, and 30-50% of energy in coal isn't the same, or as if literally every last bit of that - all of it because of the laws of thermodynamics - isn't eventually turned into heat.
Total estimate energy consumption per year [1] is about 14420 TWh as of 2021. The total solar energy we would've received in that same year [2] is 1,515,480,000 TWh. Or 0.00095%.
The amount of thermal emission from human activity on Earth is negligible. The idea that the amount of solar panels to power human civilization would have any non-local effect on the temperature of the planet is absurd.
[1] https://en.wikipedia.org/wiki/World_energy_supply_and_consum...
Meanwhile, 100% of the energy that a solar panel receives (and radiates some back as heat) would have hit the earth anyway.
This is why carbon neutrality is the focus and not just purely energy usage.
A better argument for solar panels is that per kwh of useful energy, a solar panel traps less solar energy (in kwh) than the CO2 produced by coal or gas or w/e. But I've never see this particular argument made and therefore couldn't even guess at HOW much better a solar panel is than coal and HOW much worse it is than nuclear or geothermal (which could actually be net energy loss for earth, by dispersing some thermal energy locked deep within the earth out to space).
It's not a better argument because the solar panel doesn't "trap" the energy. At most it borrows it, eventually it will radiate back out if allowed to do so, just as it would if it were absorbed by a rock. Humans do not occupy enough of the surface of this planet to make a dent in that.
The thing that will keep it from radiating back out is greenhouse gases in the atmosphere. And unlike some brief capture of energy, the greenhouse cycle is essentially a chain reaction.
In a land of mostly dark roofs it's probably a net positive.
Even if we did one of those megasolar projects people like to talk about like paneling the whole Sahara or Mojave, we would still only be absorbing a tiny amount of the petawatts per second the sun is constantly bombarding the planet with, much of it being absorbed by plants, the ocean, darker rocks, etc.
Our solar panels just don't hit the scale that the melting ice caps do, and the only thing we can do to stop that is reduce the flow of new ghgs into the atmosphere.
I can't think of a single one.
That’s even before thinking about the effect from CO₂ or methane from gas fugitive emissions.
The earth has the ability to radiate away quite considerable amounts of heat luckily, and solar produces considerably less waste heat than thermal. So solar and wind can only make things better.
Minimising waste heat is of course good, which is why energy efficiency is so important, and heat pumps are doubly so - because they are extremely efficient, but also because they don’t produce as much heat but transfer most of it!
I've actually read the opposite: most PVs don't sit directly on the roof, but rather a few inches above it. And that air gap further limits the amount of solar energy that makes it onto the roof and into the attic.
Air Conditioning Off The Grid: http://forums.bajanomad.com/viewthread.php?tid=97584
To make solar worthwhile we did an energy audit so we also replaced windows, got new siding and installed new doors. Energy efficiency doesn’t have to be mutually exclusive. I got a bigger rebate from the city with proof of energy audit.
as far as roof repairs… why would solar matter and why so many roof repairs? I’ve been through tropical storms, down pours and many a hail storm and not a single problem and my roof is 23 years old..
I could never go back. I charge my Tesla at home and my electric bill averages about 70 a month over a year after solar. That’s less than a weeks worth of gas for my Jeep.
year 6 on panels and 0 maintenance with a 20 year guarantee on efficiency and install warranty if i had problems i’d call my installer for service.
Unfortunately, we are losing some of this cumulative knowledge due to it not being documented, and due to the looks of alternatives (although the grey buildings in the US are as ugly as it can get)
> The rad thing to do in my area of california is to paint your white washed spanish style home mud brown or ozzy osbourne black.
(see Millan Millan's papers like https://academic.oup.com/bioscience/article/69/2/143/5254231 , can link to some other newer stuff if desired)
(Please don't take this as a rhetorical "this is why X solution doesn't work" -- I'm no expert here and am just curious where all that reflected heat/energy goes!)
The fact that it reached the roof in the first place means the atmosphere is transparent to it. So with a white roof, the wavelengths being reflected are the same ones being received, it'll reflect right back through the atmosphere and back into space. Effectively it just increases the Earth's albedo a tiny bit.
Any wavelengths which were gonna heat the air by absorption, were absorbed on the way in and didn't reach the roof in the first place.
HOWEVER.
In the case of dark/black roofs, the heat DOES stay in the vicinity of the house, at least for a while. The radiation was absorbed by the roof, and now two main things happen to it:
One, the hot roof heats the nearby air by convection. This is the main contributor to the "urban heat island" effect. Eventually this warmed air mass will affect weather patterns, but even before that, it just makes the place feel hot.
Two, the hot roof emits its own radiation, in a whole range of wavelengths determined by its absolute temperature, according to Planck's law. This includes infrared wavelengths that the atmosphere is not transparent to (the absorption region between 5 and 8 microns), so that radiation IS absorbed by the atmosphere and heats it as well. And just like convective transfer above, the warmed air contributes to heat-island and weather effects, etc.
(The phenomenon of a hot object emitting its own radiation is why thermal cameras work, by the way. And if you get the object even hotter, the Planckian locus shifts into our visible range and you get an object that is "red hot", or even hotter still and it's "white hot", etc. This is why the "whiteness" of lightbulbs is expressed in Kelvin, that's the temperature of an object that would glow the same color as the bulb emits. The "warm white" and "cool white" are misnomers; the so-called "cool" color represents a much hotter blackbody source.)
What is the basis for this? Intuitively (I am no expert) it seems more likely that the amount of thermal energy produced would be a function of the distance light travels through a medium and the amount of energy carried by the light in the first place. So I would expect that the "inbound" light would produce more thermal absorption energy than the reflected "outbound" light, but it wouldn't arbitrarily all be absorbed on the way in.
Reality seems to be more complicated: https://www.sciencedirect.com/science/article/abs/pii/096016...
Yes, some wavelengths are absorbed very weakly, and some are scattered rather than absorbed. But these represent a tiny fraction of the spectrum, the nuance would've overcomplicated the post, and they don't change the result much.
For wavelengths that are not absorbed, they can be reflected back out just as easily as they came in. For wavelengths that're strongly absorbed, they heat the first parts of the atmosphere they encounter, and this is why the thermosphere is called that.
For those few wavelengths that're weakly absorbed, yes they produce some heating on the way in, and if you reflect them back out, they do produce some heating on the way out. But as you've said, because the intensity of the radiation is decreasing along the whole path, the "outbound" contribution is weak indeed. It turns out to be basically a rounding-error in the thermal contribution, which is overwhelmingly dominated by blackbody absorption and re-emission, which often does produce wavelengths that're strongly absorbed. On a perfectly-white planet (or snow-covered region), you might have to start caring about weakly-absorbed wavelengths, but for most types of ground cover, other effects swamp it.
Those are no longer legal. Title 24 requires a “cool roof” *
When I had my roof re-covered a couple of years ago the roofer apologized and said he had to use a light color. Which wasn’t a problem for me so no apology was needed.
* https://coolcalifornia.arb.ca.gov/cool-roofs-codes-and-stand...
We hadn't thought about it, and would likely have opted for a lighter roof, had someone pointed it out to us.
Now that said, it would still be better for our communities to reflect this energy back out into space to reduce environmental heating. Houses in my area at solar noon have almost half a megawatt of heating potential. By municipal code they are not allowed a roof reflectivity of more than 40%.
I had been thinking of the reflectivity benefit rather than the reduction in air comditioning.
I'm in the UK and in the process of installing underfloor insulation in a house built around 1890. It is a flooboards-up job involving a windproof one way moisture permeable membrane above the joists, with hygroscopic insulation on top, and then a vapour control barrier on top of that, with all edges of layers taped to the joists where possible, all holes for wires, pipes etc. sealed with tape, and finally membranes brought up to wall behind the skirting boards. It's going to cost around £1k for a room of about 25m2. We have double glazing, the walls aren't particularly cold in winter, and the roof is insulated. I'm convinced most of our cold is coming through the floor and I reckon this job (along with the rest of the house in time, ugh) will make a huge difference.
But I'm having to do it myself because there are literally no specialist fitters where I live, and there are no government incentives that I am aware of. Why aren't the government going hell-for-leather for insulation etc.?
The release goes on to say they expect commercialization and deployment in 2024.
"Coefficient of performance" is a better term.
So the ">100%" comes from the fact that you're spending less thermal energy than you are moving?
Even electric heat alone is 100% efficient no incomplete combustion or degradation over time. Efficient bu much more expensive than just moving heat already in the air.
Ground-source are better for now since they are moving heat from a relatively consistent source the Earth. It's about 15C to 25C one meter down where the ground-source heat pump lines are run.
Generating vs moving heat I think is misunderstood by people or really more likely they just don't care. As long as the bill is low!
Running a steam turbine by pushing water down a borehole to come into contact with a high-temp (>100°C) source has been done; it's not perpetual motion. Energy pumping the water is << energy output from the steam produced. It's solar energy that's being used, ultimately.
The 300% efficiency means if you had 1 Watt you could use it to power a fan and coolant lines to move heat. Or use 1 Watt to generate heat and then once made to move that heat.
The moving of heat already existing in the air (or in the ground) is more efficient than generating the heat and then moving it.
If someone asks: "how efficient is this heat pump at heating my house?" And you start digressing about how that's the wrong question to ask you'll be giving them an impression opposite reality, which is for most people: it will use less electric energy than heat energy it puts into your house, almost all the time.
I think a COP of 2 at 5°F (-15°C) is pretty good.
My new car can do 100% driving!
Surely not engineering way of thinking but that's a common heat pump metric for ordinary people.
I live in the Netherlands that has one of the highest use of rooftop solar and generally energy conscious government and people. I bought a house recently and while doing some changes before moving in, my top priority was to get rid of Gas for heating and replace it with an all electric solution and supplement the power by as many solar panels as possible. As good as my intent is, I literally have €25K in the bank waiting to be spent for this, and the government gives a subsidy for essentially halving the cost of a heat pump, I could not get one until day mid next year!!! It is such a disappointment.
The intent is in the right place to encourage people to buy heat pumps, people are also willing. However, the chip shortage, and the insane labour crisis of qualified people who could install this is making the end result unattainable.
My wish is for the European Union to use any emergency powers it has to subsidise/mandate/beg the companies to mass manufacture heat pumps and solve the installation problem- train more people on this trade for free? Make it tax free to earn money by working as a heat pump installer? Anything…
Now, there is added incentive in the form of the need to get rid of Russian Gas. The time is now. Heat pumps already makes economic sense, it helps with climate goals, it boosts economy. I wish things happen sooner than later.
That said, there are environmental concerns about geothermals at scale (see the earthquake in Landau). Not sure how much of it carries over to residential heat pumps, though.
Here in the UK we've had nothing like that and seem to be going the other way with things like fuel duty cuts.
Another issue here at least is that it seems financially better to pair standard heating with battery storage than invest in a heat pump.
> …
> My wish is for the European Union to use any emergency powers it has to subsidise/mandate/beg the companies to mass manufacture heat pumps and solve the installation problem.
Can’t speak to other governments, but earlier this month the US invoked the Defense Production Act to do exactly this:
https://www.scientificamerican.com/article/biden-order-will-...
This isn't a technology breakthrough, this is a DOE policy/partnership/funding "breakthrough".
> The prototype delivers 100% heating at 5°F at double the efficiency, and 70% to 80% heating at -5°F and -10°F. DOE’s Oak Ridge National Laboratory validated the performance and efficiency of Lennox’s prototype.
Usually when people talk about efficiency of heat pumps they are comparing to electrical resistance heating (which is 100% efficient). If that's what they mean then they are saying 200% efficient at 5℉, which is not as good as Mitsubishi, which is better than 200% at 0℉.
But in the first paragraph they say:
> The U.S. Department of Energy (DOE) today announced that American heat pump manufacturer Lennox International became the first partner in the U.S. Department of Energy’s (DOE’s) Residential Cold Climate Heat Pump Technology Challenge to develop a next-generation electric heat pump that can more effectively heat homes in northern climates relative to today’s models.
It could be that they are stating efficiency compared to current heat pumps, not compared to resistance heating, in which case they would be claiming quite a bit higher efficiency than Mitsubishi, which would certainly justify calling it a breakthrough.
Another possibility is that what they could be claiming as the breakthrough is the 100% heating at 5℉ part. The Mitsubishi cold weather heat pumps start losing capacity below 23℉, falling from 100% at 23℉ to 76% at -13℉.
I don't think that would be as big a breakthrough as double the efficiency of current heat pumps, because it wouldn't make it so heat pumps are feasible in climates too cold for Mitsubishi. But it would make it so that in places you can use a heat pump you might not need as big of a heat pump with the new technology as you would need with a Mitsubishi. That could lower up front cost making converting from something else to a heat pump more feasible for many.
--> EDIT: Or maybe not... they seem to offer forced-air too. <--
The DOE challenge is for ducted systems. Their site[2] says:
> The Challenge is currently focused on residential, centrally ducted, electric-only HPs.
The DOE challenge also has other requirements[3] that I don't know if the Mitsubishi systems satisfy. It requires certain levels of efficiency and "grid interactivity" (meaning Energy Star "demand response"[4] where your utility can temporarily tweak your thermostat settings).
---
[1] https://www.mitsubishicomfort.com/residential/new-products
[2] https://www.energy.gov/eere/buildings/cchp-technology-challe...
[3] https://www.energy.gov/sites/default/files/2021-10/bto-cchp-...
[4] https://www.energystar.gov/sites/default/files/ENERGY%20STAR...
I'd say rip the ducts out and just use split systems but I imagine other people have thought about that and figured it's not the best way to go. (or at last not in the US)
When cross shopping the Mitsubishi vs Trane, the Mitsubishi was miles ahead. I didn’t even get the most cold weather efficient option (not needed for my climate).
https://www.mitsubishicomfort.com/residential/products/ducte...
And that says it's compatible with some "hyper-heat" outdoor units. So apparently they do offer both.
https://www.mitsubishicomfort.com/find-a-contractor
I see a few in Portland and several in nearby zip codes. Hopefully one can work for you. There are different tiers of “diamond” so you can compare if the difference matters to you.
One thing that’s a bit different is the air handler and outside compressor run on one circuit (mine is a 3 ton unit). So there’s a power line between the 2 units. That threw off our city inspector. But it works out nice since I now have an extra 20A breaker free :)
For example this is the Carrier Infinity 24 we are considering. https://d1049ui2fjityy.cloudfront.net/userfiles/inriver/docu...
Catalog:
https://mylinkdrive.com/viewPdf?srcUrl=http://enter.mehvac.c...
pocket guide:
https://mylinkdrive.com/viewPdf?srcUrl=http://enter.mehvac.c...
It’s a slightly older model as we had height restrictions to work around. This prevented us from getting a newer or hyper heat model. IIRC ours had good efficiency into the 20F range which was plenty for us.
In comparison, the Trane dropped efficiency at 50F and needed heat strips at that temp (so pretty crap).
Double the efficiency of what? All existing technology or something else? Do they simply mean the COP is 2.0?
A repair person goofed the settings last January, and I didn't notice the furnace wasn't kicking in until the end of February. My electric bill went from $150-ish for Feb 2021 to $450-ish for Feb 2022.
Thats because typically each appliance is tested at optimal conditions (eg. water flow rates). Then, in a real deployment, every parameter differs a little from optimal (eg. the water may circulate slower than expected because you have longer pipes around your home than the lab ones, and your hot water tank is hotter than expected because you like it set hot, and your airflow is less than expected because the filter is a bit blocked, etc.). Each knocks a few percentage points off the efficiency, but the overall impact can be dramatic.
We really need 'smarter' heating systems which can detect and correct for such things. For example, water and air pumps which measure temperatures and flow rates of air/water, and adjust speeds up and down to maintain the optimal efficiency point.
If anyone else is confused by this, it's because Lennox is headquartered in Texas.
As to whether or not thermo-acoustic technology could work, that's a good question.
Perhaps you were thinking of the absorption chiller that keeps the Ice Museum at the resort cold. That's a separate system.
So, 2 EER (2x of resistive heat) at 5F, 1.8 at -5F and 1.6 at -10F? Is that right? Seems awkwardly worded.
Yes (or double of previous model as another commentator points out-- hard to say).
> 1.8 at -5F and 1.6 at -10F?
They've not told us the efficiency-- just that it provides 70-80% of nameplate amount of heating at those temperatures.
They could choose the lowest temperature, find it's power input, then fix it at that amount. But at low temperatures the concern is usually less "efficiency" and more "am I going to freeze to death", because in most of the cold areas temperatures aren't usually that cold for that long (though in others it definitely is, and if you're running at 1.6 COP for a significant amount of time, you're better off with more insulation than a heat pump).
A COP of 2 @ 5F isn't a "breakthrough" vs. the first commercially available model I could find numbers for, and a COP of 1.5 at -10F seems implausible:
https://www.nordicghp.com/2017/01/heat-pump-effective-temper...
Honestly though, this press release is so poorly written, I wouldn't trust the numbers match up to anything.
It seems to me a lot of the barriers to adoption in the US are lack of awareness from consumers and widespread support from installers. The equipment for a heat pump shouldn’t be much more expensive then an air conditioner since they share so many parts, but that isn’t the case in practice.
I think government regulations that encourage heat pumps manufacturing and installation are part of the solution. For examples, Biden administration recently issued orders to use the Defense Production Act to produce heat pumps [0] or NYC banning new natural gas hook ups for heating [1].
The other part of heat pumps adoption is making them exciting for consumers. It feels like if you get the right combo of all of that, heat pumps could be the next electric vehicle.
I only recently learned about heat pumps and found it difficult to understand how they worked and potential benefits. Towards that end, I started hacking on this tool for others to get that info: https://www.heatpumpswork.com
[0] https://www.whitehouse.gov/briefing-room/presidential-action...
[1] https://www.theverge.com/2021/12/15/22837799/new-york-city-b...
is this an announcement of a breakthrough or a challenge to find a breakthrough?
> The prototype delivers 100% heating at 5°F at double the efficiency, and 70% to 80% heating at -5°F and -10°F. DOE’s Oak Ridge National Laboratory validated the performance and efficiency of Lennox’s prototype.
> Lennox is one of nine manufacturers competing in the CCHP Technology Challenge. Its product and others that meet the CCHP Technology Challenge will undergo trials in cold climate regions over the next two years to demonstrate performance, efficiency, and comfort when applied in the field throughout a winter. Deployment and commercialization are planned for 2024.
Gree has a system that claims to have full heat down to -31, so I'd say just keep researching and you'll probably be fine.
Doing a quick search, they're using 'standard' R410A refrigerant (PDF):
* https://www.greecomfort.com/assets/our-products/multi-plus-u...
the same as everyone else. It seems just that they though it worth the engineering effort to push a little further than most other companies.
See anything with the label "For Extreme Conditions":
In my case, the 99% design temperature is high single digits Fahrenheit. For the 3.5 days/year colder than that, the plan is to have the house “coast” on thermal mass.
That’s for cases where the ambient temp is below design (where the heater can make heat but just no longer enough to keep up with the building heat loss), not for when it’s below a cutoff (where the heater shuts off entirely). In my case, that’s so far below design temp that I’d expect to never see it. (We hit -9°F in 2016 and would have to go all the way back to 1943 to find a low of -14°F.) If it happened, thermal mass would start to carry us with electric space heating keeping the house from totally freezing.
I'm planning on getting rid of it altogether and doing the heat pump(s) most of the year, the wood stoves in winter and reclaiming a lot of headroom in the basement and an entire utility room that the furnace currently takes up.
But, if you’re willing to wait or pay extra for the efficiency gains, you might be even better off getting set up with a ground source heat pump now. The install cost is more up front, but because ground temperature is higher than air temperature in winter and lower than air temperature in summer, the differential you need to pump in or out is a lot less, and therefore much more efficient. I don’t think any air to air heat pump in the next 20 years will be as efficient as a ground to air system you could install now. The air to air systems just have lower up front install costs.
Edit: it’s 26% this year and 22% next year.
One tip from my install, is to go with single zone units. I did a multi-zone and the way the control system works is kind of weird. They also don't have as good of a turndown ratio[0] as smaller/single zone systems, making it less efficient.
Overall I'm happy with it though.
Or I could upgrade from oil to gas for $14K (to an 82% efficiency boiler). I have a strong incentive to do this since the cost of heating with gas will be 1/3.5 compared with heating with oil.
I think these are insane prices, but that's what contractors get around here. There is a $10K incentive for the heat pumps, but it requires a home inspection and probable upgrade of the insulation. IMHO, the incentive is not enough- it needs to make the heat pumps the cheapest option.
As far as fuel costs, the gas would definitely be cheaper. The electricity comes from gas (especially in the middle of the winter). The price is more because you are paying someone to convert the gas to electricity. The efficiency of getting the heat from gas via electricity is only a little more with heat pumps (when accounting for generation and transmission loss and much higher heat pump efficiency).
Maybe in the future the electric supply will be greener, but it isn't today. They are trying to build a HVDC line from Boston to Quebec for more hydropower, but Maine and NH are not allowing it due to NIMBY (a referendum in Maine, financed by gas companies, killed it).
So we could have had efficiency 10 years ago instead of today?
Water source heat pumps are easier installations but require houses sited near a specific type of fresh water source that does not fully ice over in the winter or dry up in the summer.
Heat pump is better than burning fossil fuels, but we also stop needing to treat system after system like it’s a bottomless well. We did that with real wells, then rivers, then the sky, then the ocean, then carbon dioxide and next up will be ground heat.
There was a house last year that I think people were complaining about on Reddit, giant house out I’m the woods, all glass walls and heat pumps, labeled as green. It’s not a green building if you are 2x as efficient as fossil fuels but your house needs four times the BTUs of a reasonable design and 6 times a green one.
Twice as efficient and half the heat loss is green. Blowing the surplus is not.
When you do have land, your horizontal space now is also being used up by a septic system.
It's great if you can do it, but on the whole I suspect ground source is always going to be an expensive and difficult proposition for most people.
That's like one month of heat for free. A welcome respite, but hardly revolutionary. Slashing emissions is awesome though.
(None of those details can be inferred from the press release.)
My house was built in 2000 with a regular AC unit for the main floor and heat pump for the 2nd floor, both Payne, a builder grade of Carrier. The inside coil went first, at the 9-yr mark with a 10-yr warranty, so I did get a new coil at no expense but it cost $600 to install it.
A couple years later, the outside heat pump went out, and because of the system's age (about 11 years), they recommended replacing the furnace and heat pump.
A couple year later, the main floor furnace exhaust gas blower mechanism went out, and again, the outside unit was replaced because it was 14 years old.
In contrast, my previous house had an American Standard AC and furnace that was installed in 1970 when the house was built. I had to replace the furnace blower motor one year - about $500 I think - but the original AC and furnace were working like a champ when I sold the house in 2003.
In summary, you aren't getting 20 years out of any modern, shitty system anymore. They're designed to fail after 10 years. You might get lucky and have something fail after 9 years; then you'll only have to pay for labor. But because there are 2 major independent components, the outside compressor and inside furnace, it's unlikely they'll both fail within the warranty.
My AC guy told me the main reason they fail is because the new coils are made of very thin aluminum and so fail sooner than the old systems. If a coil fails, either in the furnace or the outside condenser, you're screwed. They can sometimes fix them, but good luck with that. Most HVAC dealers don't want to bother doing that; they just want to sell a new system.
(Tbh, I recently did a high level analysis of a heat pump in a temperate climate, and in light of climbing fuel bills and the potential for low price electricity from renewables at low demand plus batteries, heat pumps start to make a lot of sense. You need to think about using them differently to gas though)
Sure the "efficiency" is improving but it's mainly tricks for turning it on/off at better times. I know there are some U-shaped ones now, but it's just a slightly different styling.
Edit: two commenters pointed out examples of air conditioners which are 77 lbs and 56 lbs. As a comparison, the OSHA recommended lifting weight is 50 lbs. I would love to see someone apply Apple's obsession with thinner, lighter, "revolutionary new design" to ACs.
https://www.homedepot.com/p/Toshiba-14-000-BTU-12-000-BTU-DO...
[1] https://www.midea.com/us/air-conditioners/window-air-conditi...
No affiliation to Midea just a satisfied customer.
I have one in a room on the far end of the house that the main AC can't reach, it helps reduce power usage since I can keep the rest of the house warmer.
Edit: it might also be an issue of diminishing returns of better efficiency compared to how difficult it is to produce and maintain a better unit. Thermodynamics can be a pain like that.
EDIT: Oh lol, the unit we got was actually one of those Midea ones linked in a sibling comment.
The First Law of Thermodymamics.
Heat is work and work is heat
The Second Law of Thermodymamics:
Heat cannot of itself pass from one body to a hotter body
Heat won't pass from a cooler to a hotter
You can try it if you like but you far better not-a
'Cos the cold in the cooler will get hotter as a rule-a
'Cos the hotter body's heat will pass to the cooler
Heat is work and work is heat and work is heat and heat is work
Heat will pass by conduction and
Heat will pass by convection and
Heat will pass by radiation
And that's a physical law
Thermoacoustic refrigeration seems to be one of the more promising technologies but I would love to hear about others.
Interestingly, they aren't that loud because any sound lost is energy lost, so they try very hard to 'keep it quiet'.
Some areas (cough nyc cough) may need some regulatory breakthroughs but the technology is there.
Computers are actually a very special case. They don't really do any physical work in sense other stuff does, thus miniaturization gives lot of gains there. I have long said that small drones are answer to flying cars. We have them and they are small, but lifting people is hard work.
It's physics and thermodynamics. It's basically the same as with any heat engine, internal combustion engines included.
There is a certain maximum theoretical efficiency that is not 100%. When we build real machines (not theoretical ones) there are real world losses like heat loss, fluid flow friction, moving part friction, electrical inefficiencies, etc. Those real world losses van be gradually worked on over time, improved incrementally to yield small gains in efficiency. But never large ones, and never more than the theoretical max efficiency, which is not 100%.
It's like hybrid cars (not plug in hybrids, but just gas powered hybrids), they've doubled or trippled the mileage compared to a comparable regular car, but they will always need gas, they will never be 100% efficient.
Same with this. There will always be some fundamental electrical losses in the copper in the motor, air gap losses in the motor, friction in the bearings and fluid, heat losses to the environment, etc. It's the cost of doing the work. There is no free lunch, so we can only incrementally improve the little losses over time.
"The coefficient of performance or COP (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required.[1][2] Higher COPs equate to higher efficiency, lower energy (power) consumption and thus lower operating costs. The COP usually exceeds 1, especially in heat pumps, because, instead of just converting work to heat (which, if 100% efficient, would be a COP of 1), it pumps additional heat from a heat source to where the heat is required. Most air conditioners have a COP of 2.3 to 3.5. Less work is required to move heat than for conversion into heat, and because of this, heat pumps, air conditioners and refrigeration systems can have a coefficient of performance greater than one. However, this does not mean that they are more than 100% efficient, in other words, no heat engine can have a thermal efficiency of 100% or greater. For complete systems, COP calculations should include energy consumption of all power consuming auxiliaries. The COP is highly dependent on operating conditions, especially absolute temperature and relative temperature between sink and system, and is often graphed or averaged against expected conditions."
https://en.m.wikipedia.org/wiki/Coefficient_of_performance#:....
More detail here:
https://physics.stackexchange.com/questions/489467/can-a-hea...
In short, a heat pump is more efficient when compared to using the energy to directly generate heat because it's more efficient to move heat than generate it.
Absolutely not. Where I live we had 34°Ctoday but I would still never buy an A/C unit, which will ruin your health (heat/cold shock, bad air moisture levels, ...), waste immense amounts of energy and makes leaving the house a pain as the rest of the world becomes uncomfortable. Most of my friends here earn very well but I can't think of anyone that would see a reason to buy one. Live with the temperature and adjust - like the famous Iberian or Mexican siesta, where you simply accept that midday are low energy hours.
But even beyond this, the reason for A/C use is just bad architecture and city design. More trees in the streets can lower the temperature in the street itself and nearby residences easily by 1-2 degree. Less absorbing surfaces (asphalt, stone sidewalks, ...) make another difference.
And as regards the houses, there are plenty of ways for passive and energy efficient buildings that keep cool. In the middle east they have built self-cooling houses for centuries.
And in all this, even if you are stuck with bad streets and architecture, you can simply adapt, use efficient ways to keep cool (a fan can work wonders) and drink warm rather than iced drinks and your circulatory system will thank you as you don't switch regularly get shocked with 10-15° differences and you will sweat much less.
We need to start nullifying IP if we ever hope to see innovation.
If you can't have central, you should have mini-split, and that's where all your problems get solved. If you can't get mini-split because your landlord won't let you drill conduit to outside then you're just kinda stuck and the laws of thermodynamics are your enemy, not a lack of innovation.
Business wise, if this really works at 2COP at 5F, this might take over most of the market served by ground source heat pumps though.
Tell me you’ve made an incremental improvement and I’ll believe you, tell me you’ve made a breakthrough and either you’re lying or something will prevent it from being realized before commercial availability. This is what decades of press releases and articles that might as well be press releases have taught me.
And I suspect the magic here is also an air tight new construction home with a layout designed around this, not leaky everything with an old water heater tucked under the stairs, a 30 year old furnace, and R19 insulated walls.
The "up to" part means it's the absolutely largest home you can possibly imagine
I have realized an approximately $500 yearly savings by replacing an older electric tank water heater with a hybrid electric (heat pump) water heater so I can believe that claim.
The announcement is basically: A US company (Lenox) has a prototype heat pump that matches performance of Mitsubishi and LG heat pumps.
The DOE is running a competition to get US companies to improve performance of their heat pumps.
But there exist sooo many prototyping breaktroughs.
Those who follow press releases for many years know that just a tiny fraction can transfer this in real world products that actually work
(so many more challenges to overcome compared to prototype situations!! I don’t even know where to begin… every ground is different, average person doing the manual work is not as skilled and has less support engineers, the guys setting/defining the dimensions of various recipients/pumps/conduits are often undeskilled and the efficiency often lacks tremendously for that reason…)
Labor is expensive right now. :(
I set mine up with T's, electric dampers and some simple logic.
It's a bad system. Split systems make sense, and I know they exist, but they seem weirdly rare.
Some data on this topic: https://www.energyvanguard.com/blog/will-a-heat-pump-water-h...
I have the stats from my own Rheem to know I’m coming out ahead financially during winter and also haven’t seen a meaningful swing in the basement climate.
I’m a regular participant in that linked blog, too. :)
- the Canada premium: these sorts of things are just more expensive here. The base price was just higher than I could find in the US, but obviously importing is too expensive. I think the reason for this is there's almost no stock.
- adapting my house: the house I live in was built to have central air added to it, but even so the pipes going from the furnace room to the outside had to be insulated both directions instead of only one for an AC. Ripping up our basement ceiling to do this added a lot to the cost. An unfinished basement would help a lot here.
- HVAC company confusion: I had to go through like five HVAC companies before I found one that would believe me that I really wanted it. The one I got is a commercial outfit, so their prices were just higher. Even they were skeptical but they were willing to work with us, and by the end they talked about doing more installs so that was nice.
I think the cost for the install and unit itself was $12k for a top of line carrier unit capable of working down to pretty low temperatures. But we already had a compatible carrier furnace and exchanger. Was another couple thousand for ripping up the basement, which we had other contractors do.
This was also literally during the heat dome last year. They had to ship the unit across the country.
You can definitely do it for cheaper. There are $1000-$3000 single-head units available online for self-install, and you could hire an HVAC person to come out and do the high pressure line part of it (or all of it) for a similar range. It just gets expensive with the name-brand ones. For some reason that $2k-6k turns into 10k-20k when you switch to a name brand (e.g. mitsubishi). They're only available through specific installers, and using a non-authorized installer means your warranty is void.
Of course, a multi-room install would probably get expensive quickly here too.
[1]: https://kaiteki.no/
That's certainly a way to retrofit an older building, but you still need a heat pump.
A heat pump isn’t cost effective compared to Reno with spray foam. An average heat pump probably takes a decade minimum to pay off.
Serious question.. I'd have thought it not practical to remove the cap on the wall (and that's assuming you can access it from the attic).
edit: "top plate" is the term I couldn't remember. substitute for cap in my comment.
We got blown insulation in the floors (ie between roof and floor), he drilled a 2 inch hole every two feet or so. We added our parquet floor right on top, with just some thin XPS sheets inbetween for noise.
Not sure about drywall, but I'd imagine it's similar. Easiest would be to just put some 6mm plasterboards on top to cover the holes, saves you handling each one individually.
A cheaper option is rigid foam with canned spray foam around the perimeter.
In the mean time, there are good quality air/water heat pumps on the market in Europe. Look at the Nibe F2120 for example. It blows this thing out of the water. It has a COP of 2.5 at -25C...
Cooling the output should increase the Carnot efficiency of the motor.
Heating the outside air intake with that heat should be sufficient to avoid the need for an electrical resistance pre-heater.
This combination could also run on propane, ethanol, gasified wood, etc. Anything that gets burned now could be used to create far more heat output than straight up combustion.
There's got to be a flaw in this idea, math/physics wise.
The great thing about electricity is that it scales REALLY well with new generation and distribution technologies.
Or, spend the same amount on air sealing reducing heating needs by about 30%, pay workers instead of factories, and get the same reduction in natural gas use, also without the refrigerant bomb waiting to go off, and not needing more power plants built. Mandate every rental have lower than 6 ACH50, since misaligned incentives mean they're usually worse than homeowner-occupied units.
Wind and solar also lock in natural gas usage, because they don't provide inter-seasonal storage or even intra-day storage.
55 billion cubic meters annually were set to be added to this dependency as recently as February 21st of this year before yet another land war erupted on the continent, forcing them to suspend certification.
The pipeline is already built though.
The flaw is that we need to stop using fossil fuels now in order to meet Paris targets.
Natural gas in particular is an issue because demand is increasing globally whilst large suppliers i.e. Russia, Australia for many reasons are not able to meet it. Which is pushing up prices and increasing unreliability over the short, medium and long term.
Now is the best time to bite the bullet and transition to a decarbonised world.
It’s pretty complicated. Direct hearing via heat exchanger is usually pretty good and much simpler, albeit less efficient. If burning thermal sources, raw efficiency is rarely all that necessary though. The heat output per unit mass is usually pretty high.
Environmental impact or geopolitics issues aside, an electricity grid is much more convenient and cheaper than a propane/ethanol/gasified wood grid. Transporting gaz by trucks and storing it in individual houses is not very convenient too.
Personally I’ve seen them use when there are large air conditioning loads but insufficient electrical power
All I'm suggesting is that we take an existing natural gas furnace out of service, and replace it with something that uses FAR LESS natural gas, with the same heat output to the home. It's not perfect, it it's better than what's there, and fits within the infrastructure in place.