Thermoelectric heating stands at the brink of commercialization
spectrum.ieee.org
spectrum.ieee.org
These sentences are useless. Going from 1 to 2 probably means doubling the efficiency, if the base value is 0. But even if that's true (which it's not guaranteed to be) is a real-world usable value 3? or 478?
Much later in the article: "Vining predicted in 2009 that a ZT of 4 would be the required threshold for commercialization." There it is. But even with that, the information given tells us very little about the underlying property, or the technology.
And I don’t get why replacing one is an all day job for three people. There should be standard connections they just plug into. Like a dishwasher.
The hardest part of installing AC is the ductwork. Swapping out the outside + inside heat exchanger unit is a 1-person 3-4-hour job.
Sorry if some HVAC company scammed you, but it's definitely not a 3 person job, unless we're talking some commercial building 5+ ton units.
Seemed like a lot of wiring and charging things. I didn’t think it should take that long either.
Their price was in line with other quotes. I wasn’t paying by the hour or anything.
Anyway, the install itself was about $400, took one guy a few hours like you said. Another $200 for the electrician which had to hook up a dedicated circuit for it as per regulations, though he did it as part of a larger job so would have been $300 as a stand-alone deal.
Total it was $2200. This is considered a premium unit over here, we could have gotten something cheaper but alas looks matter.
Thing is supposedly guaranteed to provide COP of 2 down to -25C. We've had such low temps here a several times (in fact past week has been around -15 to -17C with a harsh 85% humidity, biting!) and we've never had to turn on the backup floor heating so far. Though you can definitely hear it working harder when it's that cold.
[1]: https://mee.no/privat/produktkategori/luft-luft-varmepumper/...
The plumbing is covered by a plastic cover, both for protection and looks.
We have a small wooden "shed" for the outside unit[2], to protect it from getting clogged up with snow and also to make it less visible. Both the plastic cover and the "shed" is painted in the same color as our home, so blends in nicely.
[1]: https://www.varmepumpeservice.no/mitsubishi-kaiteki-6300-hvi...
Where natgas can lose its lustre is on delivery/standing charges. And sometimes transmission and distribution charges (those usually scale with use, but can make cheap gas expensive).
On smaller/well insulated homes, the fixed gas connection cost can really improve heat pumps economics if you're already on electric grid and can cutoff gas entirely. Or have an aux source like oil/propane/wood.
The fun part is that utilities are generally a regulated rate of return business, so as users disconnect, the base costs go up on the remaining subscribers. Pushing more subscribers to disconnect from the gas grid, pushing cost up on the remaining...
I wouldn't invest in natgas distribution companies in mild-moderate climates.
Of course the maintenance costs and the amortized cost of infra is a much larger proportion of the gas bill, but the utility can't pass that on to customers as a fixed monthly fee. Gov't tariffs usually make that illegal
It was nothing but "only rich people are buying these right now so lets cash in" pricing
https://www.acdirect.com/ductless-mini-splits/8-zone-mini-sp...
80k is hilarious. That’s a 70k install for pulling lines, charging them and maybe an electrical run and pad.
Even if you have to buy two or three systems the price is laughable.
A large multi-zone installation (~20 rooms) with all-new duct work and natural gas backup in a major cold-weather US metro can be about $40K.
If it cut my electricity bill in half it would take 10-20 years to break even.
We recently upgraded our central heat pump as the old one died after 15 years or so. IIRC the total was $13k CAD, so around 9-10k USD, which included indoor and outdoor units for a roughly 3000sqft house, with installation. But all the ducting was there already, so it was just a matter of swapping out old unit for new. (Got some nice government grants too, so it was only a few k out of pocket.)
Presumably there is a useful life on your existing heating system. At some point it would need replacing?
Let's go through the whole process. You need a system changeout for a ducted central HVAC system. Someone comes over and gives a bid. You accept. Your HVAC person needs to go to a supply house and purchase all of the parts and bring them to your residence in a vehicle than can hold everything.
Assuming you have an existing system, the refrigerant has to be recovered with a special recovery pump. You can't just dump refrigerant to the atmosphere. This can take an hour or so.
You've got to find the right breaker(s) and then turn them off. Disconnect the power wiring. Then you've gotta disassemble the old equipment and remove it. Next you move in the new equipment. Rewire the power. Rewire the controls wiring. Assemble the new equipment, assemble plenums, cut holes in plenums, install collars, run duct work from plenums to boxes, attach and seal all ductwork with tape, mastic, etc. You need to strap up the ducts to properly. You still need to solder the line set at this point.
If your new equipment runs on a different type of refrigerant, in all likelihood, you need a new line set (the copper tubes that transport the refrigerant to the evaporator from the condenser and back). Why? Different refrigerants have different working pressures, may require higher flow, etc.
Once you're lineset is soldered back to a condenser AND the evaporator, then you must pull a vacuum on the system to A) remove non condensable gases and B) dehydrate the system so that your refrigerants are clean and the system is efficient. Properly pulling a vacuum is very time consuming. Most guys start by pulling an initial vacuum and then shutting in the system to do a leak test. You may find a leak, this takes more time. You need to repair the leak, then pull another vacuum. Once you past leak test, you pull a final vacuum. You don't want installers skimping on this step as this affects the overall lifespan of the system and system efficiency.
At this point, you can start the system (I've had new units dead from the factory... groan), then you can start charging the system with refrigerant. You need to let the system run for a bit to monitor pressures, monitor return air and supply air temps, etc.
Once the job is done, all of the old equipment and refrigerant has to be taken to specific places for proper disposal.
Everything above is a generally straight forward non-permitted replacement. Other installs may require new circuits run to the equipment, natural gas lines, etc. Some jobs require permits so now the HVAC person has to go to the city, apply for permits, submit plans, have the work inspected, etc.
There's quite a bit of work that has to be done which requires transportation, disposal, specialized knowledge, expensive tools, employees, and most important of all, insurance! Also, keep in mind that a lot of this work is done at temperatures FAR beyond ambient AND in low clearance areas, usually filled with itchy fiberglass. This work is also done with risk of bodily harm (electrocution, poisoning (hello phosgene gas), suffocation (asphyxiation from refrigerants), heat stroke, falls from height, exposure to industrial pollutants like asbestos, burns).
But not $10K for a mini-split.
It's interesting that Americans are retrofitting them into HVAC systems, while in the UK we're trying to retrofit into natgas/water based systems, and seemingly the Scandinavians have gone for .. I'm not sure but it seems cheaper?
I upgraded to a "hybrid" system because it was the least cost / minimal change, so I continue to have natgas hot water which can optionally heat the radiators if the control unit deems it economic (no, it doesn't have dynamic pricing). And that was still £15,000 even though it could reuse all the existing radiators. Apparently having 8mm "microbore" copper plumbing is a problem for "low temperature" heat pump systems, because they rely on higher throughput.
At the end of winter I'll write-up my bills and evaluate the experience.
Air to air is much cheaper and is more efficient because it doesn't need to raise the temperature of the working fluid so much and doesn't require a big fluid to water heat exchanger.
I'm having a Toshiba Polar 35 heat pump installed soon. Nominal output 3.5 kW, maximum output 7 kW. The total cost is 28 kNOK, about 2.6 kUSD, 2 kGBP. Should be enough for the whole ground floor of about 80 square metres.
"Difluoromethane, also called difluoromethylene, HFC-32 Methylene Fluoride or R-32, " [2]
[1] https://www.toshibavarmepumper.no/globalassets/inriver/resou...
So yes, air-to-refrigerant-to-air. But your packaged terminal heat pump is also air-to-refrigerant-to-air. Both are just refrigerators turned inside out.
"“Packaged terminal heat pump” means a packaged terminal air conditioner that utilizes reverse cycle refrigeration as its prime heat source, " [1]
[1] https://www1.eere.energy.gov/buildings/appliance_standards/s...
Most heat pumps installed in dwellings in Norway are capable of cooling the building as well as heating it. This is the one that will be installed in my house (in Norwegian, Google does a good translation job): https://www.toshibavarmepumper.no/varmepumper-luft-luft/tosh...
> Air to air is much cheaper and is more efficient because it doesn't need to raise the temperature of the working fluid so much and doesn't require a big fluid to water heat exchanger
It might still be worth it to go with water based system if you're going to have underfloor heating. It requires lower water temperatures, so efficiency hit is not that big compared to air-to-air systems (if there is a hit at all).
As a bonus, there are some savings from using the heat pump to heat the hot water for showering and you get the supreme cozyness of warm floors.
On the other hand, now you need some other way of cooling in the summer as underfloor system will not work for that.
:-)
The majority of the world deal with these temps for months on end without A/C.
After a pipe burst in the baseboard heating system (because it wasn't running, it was only -10F outside, and the pipe passed through a poorly insulated area of the house), I had the HVAC company rewire the system to use the gas-fired, forced hot water baseboard system as the backup. I look forward to much lower heating costs this Winter.
I understand your bill went up because the backup electric heating was kicking in.
I don't understand why in 2022 it would even be an option to get a heat pump installed that only works down to 25°F. That's super outdated tech.
Funny that you mention standards.
It should be possible to swap out the multimedia device in your car with a new one. It should use a standard connector and form factor.
So I guess we should start working on standards that would improve our world and make reuse possible instead of buying even more new shit all the time.
[0] I mean real duct tape: the UL181 stuff. The world is full of kinds of tape, and many of them are excellent. I’ve never seen anything I would call excellent duct tape. It doesn’t conform well to irregularities, and it doesn’t seem to have anywhere near the stretchiness required to actually seal the inherently curved gap between round ducts.
edit: apparently I was misinformed, but it doesn't seem like something worthy of being downvoted into oblivion.
It'd be amazing if someone put together some kind of dynamic calculator that could take electricity and natural gas prices and examine inside temperatures based on a smart thermostat system and rejig the cutoff temperature based on all of it.
There's a (third-party?) dashboard of the data here: https://agile.octopushome.net/dashboard
Does make it very clear where the afternoon peak is though, and that's a nice dashboard.
In other words, with one part of electrical energy, they manage pull 3 parts of of heat energy from the outside air into the room. Hence, they use just 25% of the electrical energy that a electrical resistance heater would require.
They're currently able to replace a boiler for a heating system designed around relatively low-temperature (120°F/50°C) emitters, with lower temperatures leading to better performance (so a large radiant panel in a floor or ceiling is a good choice).
One of the underutilized capabilities they have is to do radiant cooling. The tricky part is that any part of the system that drops below the dewpoint (in whatever space it's located in) will condense moisture out of the air, likely damaging itself or things around it over time. You can address this to some degree by either modulating the heat pump or mixing/recirculating water to keep the emitters a few degrees above the dewpoint, but that limits the amount of sensible heat that you can remove from the space and doesn't do anything for latent heat (i.e. humidity).
One solution is to use an emitter (e.g. fan coil, either central or in a little wall unit like a mini-split) that has a drip tray that drains the condensate away to where it can't do damage, but the pipes leading to the emitters still need to be insulated and vapor-sealed. This isn't terribly expensive to add to a new system but could be quite expensive to retrofit into a system where the pipes are already buried into the walls.
Another approach is to keep the fluid above the dewpoint and use a separate dehumidifier that condenses moisture out of the air and releases the resulting heat into the space. This isn't ideal because you're adding an additional heat source into the space that you're trying to cool.
As I understand it, the strength of thermoelectric devices is that they're silent and relatively small, but their weakness is they're not terribly efficient, especially for cooling, and have a steeper drop-off of efficiency with increasing temperature difference between the cold and hot side.
But for dehumidification, the temperature difference is likely small (from a few degrees above the dewpoint to a few degrees below it), and also the latent cooling load tends to be a fraction of the sensible cooling load.
So the idea would be to build a device that is plumbed inline with the emitter in each room (or possibly just e.g. a bathroom or kitchen) that uses a thermoelectric device to cool a heatsink below the dewpoint (with a fan) and collects the condensate for disposal, but rejects the heat into the return pipe to the heat pump.
The advantage over a conventional fan coil-based system is that the in-wall plumbing (and indeed all of the hydronic plumbing) remains above the dewpoint, so the indoor hydronic piping doesn't need insulating or vapor sealing.
I could see this being especially useful in buildings converting from a condensing boiler to a heat pump and want to add cooling without tearing open all the walls.
Northern Canada we run our wood stoves for ~8 months a year. Temp on the surface of the stove is 200C to 300C. Outside is -20C to -40C.
Let's say an average of 200C temp delta across the TEC.
Throw a radiator on the outside of the cabin, use coolant with a tiny pump to circulate. How much power am I going to generate with a square foot (or two) of TECs strapped to the wood stove, using the coolant loop to cool the other side?
It feels like we have such a huge temperature delta we should be able to do something with.
I feel like that's not a great use of your stove?
Heating with a wood stove doesn't really have a 'medium' setting. You get 100% while it's roaring away, and that slowly diminishes as the fuel burns down. (Yes you can adjust dampers, and air-flow valves to "slow it down"; but that doesn't really work/happen.)
I've lived in a home heated by a wood stove for 10 years. You would build-up the stove so it blasts away, goto bed, and by morning there would be enough coals left to start it up again but quite chilly in the house.
There is nothing like it. I love it. I don't have the same access my father did to family farms, wood lots, and trees. Today I would look into rocket mass heaters. Spread that heat out and allow it to more slowly heat a house.But that doesn't really address my issue. For an ambient wood stove, the heat is pushed through the house from one central spot (the stove).
If you use a system to use that heat for power or something else, aren't you just going to cool your home?
Ie convert 1% of the stoves energy into electricity which you then use to power a fan. The fan‘s waste heat also heats the room thus you get to use both the utility of the fan (1%) + waste heat from stove (99%) + waste heat from fan (1%) = 101%.
Carnot limits the efficiency to make work from a thermal process (much less then 100%, in fact).
Carnot does not prohibit you from enjoying the inefficiencies as waste heat.
A computer converts 99.9% of the electricity to heat a room just like a space heater. However, you can play video games on the PC while it’s heating your room.
Pick up a pile of aluminum oxide from a depot, electrolyze it into aluminum at home, and drop off the finished aluminum at the depot for a cheque that covers your electricity.
"The theoretical minimum energy requirement for this process is 6.23 kWh/(kg of Al), but the process commonly requires 15.37 kWh."
https://en.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_proc...
That's quite a few kWh of heat per kg of finished product. You're going from Al2O3 to Al, so your returns will weigh less than your pickups.
Comparable to coal or oil heat:
"With a complete combustion or fission , approx. 8 kWh of heat can be generated from 1 kg of coal, approx. 12 kWh from 1 kg of mineral oil"
It might make sense at industrial scale while pumping waste heat to nearby office buildings or something. But even slightly higher electricity costs would be a huge issue.
An aluminium smelting at home heating solution would have a maximum CoP of 2 (as you're reducing the energy usage of the smelter by the same amount). A heat pump could easily have a CoP of 3 or 4.
The use of electricity as an input is inescapable for this process, so may as well use the waste heat as directly as possible.
Thus various schemes for combined heat and power etc which take the valueless waste heat and use it for some other purposes like warming homes or greenhouses etc. So while the COP would be 0.5 the electricity would be subsidized by the smelling process. https://en.wikipedia.org/wiki/Cogeneration
Where such schemes fail is generally economies of scale.
I disagree with that article for the simple reason that I do not consider burning wood to be sustainable, or healthy for anything with lungs. Wood should be used for long-lasting construction or left alone / carefully nurtured to aid our forests in rebuilding biodiversity.
https://www.nytimes.com/interactive/2022/09/07/world/europe/...
https://www.theguardian.com/commentisfree/2022/dec/27/wood-b...
But if you're going to burn wood anyhow, perhaps thermoelectric stoves aren't a terrible way to generate electricity for yourself.
Short lengths, widths, knots, imperfections, wood waste pressed into pellets, etc.
Although you do have a point about it being bad for air quality. Especially old stove installations.
25 years ago my grandmother bought a pellet stove that lasted for 15 years with semi-regular maintenance.
Her next stove, same company, broke all the time and lasted less than 10 years, with much higher ongoing costs.
Enshitification strikes again!
So anecdotally, a stove that’s not a rusty old potbelly and has a good draft seems like it could be okay for air quality.
You can sell the trunk of a 200 year oak (though often they’re hollow if they’re that old) but you will have PLENTY of good firewood left behind from harvesting it, with all the branches. The best use of a 200 year old oak is of course to let it be, the backbone of an entire ecosystem. An 80 year old walnut is another story…
Maybe it's not as bad as fossil fuels, but it still has the same issues as commercial monoculture farming, which is why there are issues with bark beetles now. And most of these forests start by tearing down old growth forests.
For example, here is an MIT team experimenting with using forked tree branches in construction: https://energy.mit.edu/news/using-natures-structures-in-wood...
In Northern Canada there is almost no other way. Once you are ~10minutes out of town there is no natural gas. Also note wood stoves now are double (or triple) burning with catalytic combustors that extract waaaay more heat from the wood and emit waaaay less particles in the air (because they burn it)
You can't really make such a broad statement. Sure, burning wood isn't a sustainable solution for everyone everywhere, but there's plenty of situations where it's the least-worse option for heating. My parents heat their house with wood they gather from their property which mostly falls naturally. It's impractical to do anything else with it.
Perhaps they could let it decompose - releasing approximately the same amount of carbon it releases in burning - but while that might benefit the local ecosystem marginally, it would also mean they were heating their house with fossil fuels instead.
Better to store the heat somehow, and have it be slowly released.
It's electricity I want, in the winter, when the sun is only on the solar panels for ~3 hours a day.
You're better off buying a little steam turbine and generating electricity directly off of the stove. On top of the electricity, you get to keep the heat.
Or, better yet, buy a propane tank and a suitably large generac. Then pipe the cooling water into radiators in the house.
This is what since several years ago many researchers are obtaining (those ZT=3.1, that is 20% of efficiency? for eventual temperatures) with a mean of ZT=2 as much. Peltier effect cells remain inefficient, they are electricity guzzlers.
I don't understand then the article's purpose.
Though I'm not even sure what the target audience is anymore.
Are there thermoelectric modules less prone to failure than Peltier modules?
They have an awfully high failure rate in every project I’ve tried to integrate them into
For what it's worth, my mini fridge and my chest freezer use some hydrocarbon refrigerant. They're littered with warning signs not to puncture them.
R-1234yf is not only (slightly) flammable but also releases hydrogen fluoride and carbonyl fluoride when exposed to fire, but this is what is in almost all new cars.
I've run a propane/butane mix in an R12 car before and the fact that it was flammable didn't bother me a bit. The 14 gallons of gas would worry me more than 12oz of propane going up.
Ammonia is definitely still used as a refrigerant, just not in consumer equipment. It’s commonly used for ice rink chillers, at least in the US and Canada. Not sure about Europe.
that's key isn't it? Ammonia is corrosive and consumers are often not too bright.
Chemical companies do plenty of actual evil things, there is no need to spread false claims!
HC's are gaining in popularity but they are being fought every step of the way because they are cheap and there's no money to be made.