Why can’t my whole home participate in this technology? It would seem an ok fit for things like freezers, refrigerators, hot water heaters, etc.
When it’s freezing cold outside, it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated.
Someone needs to make a standard for moving heat/cool through all appliances in a house…
> it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated
The fridge is simply moving a little of the warmth in your room out of its box, and adding a little more warmth to the room in the process. You lose no heat from the room, which is what matters, really. It would be worse to dump the heat outside! At least in winter. The heat has to be removed in summer if you have air conditioning.
In any case, an exterior heat exchanger and heat pump that can handle a wide exterior temperature is much more heavy duty. This could all end up being less efficient, in practice. House-scale heat pumps can efficiently move heat even from a freezing cold outside into a warm interior. Just as fridges can efficiently move heat from their cold interiors to a warm room.
I always joke that in winter all appliances are 100% efficient (I know they're not). Some look at me funny but the ones who pay the gas bill get usually get it.
If you have a resistance electric furnace, that is essentially true. With gas, you add the electric generation and distribution losses, which is a pretty big difference. It does cost more to run an appliance than to heat with gas.
If you account for the electric generation and distribution losses, you should do the same for gas.
"It does cost more to run an appliance than to heat with gas."
That's highly dependent on the appliances involved and the price you pay for each fuel. For me, a heat pump is much cheaper to run. You really need to calculate it for each individual situation.
It's always been funny to me that throughout engineering people chase like 1% efficiency improvements from like 20 to 21 or 35 to 36 and it's usually a big win when achieved... meanwhile resistive heating has an efficiency of 100% and it still manages to absolutely suck.
It only sucks because of generation and transmission losses. If those didn’t exist (not possible), electricity would be much cheaper and they would be on par with or better than natural gas furnaces
How do they affect the air quality indoors? Don't modern (less than fifty years old) gas boilers have balanced flues so that they take in air from the outside and exhaust the combustion products outside too?
Surely properly installed gas boilers always did that even without balanced flues too.
My experience (sample of one) is that they don't. They're supposed to, but VOCs are definitely higher all winter running heat than all summer running air conditioning. Natural gas combustion is at best _mostly_ exhausted.
> My experience (sample of one) is that they don't.
There is something very very wrong with your equipment (or you're measuring something else not having anything to do with the heating equipment - more likely). A high efficiency furnace has a sealed combustion chamber, the entire thing runs in a circuit vented to the outside - combustion air comes from the outside and it is vented to the outside. If it is not airtight sealed from the indoors, it is broken. Even a mid-efficiency furnace with a non-sealed system will vent 100% of the flue gas outside.
> Natural gas combustion is at best _mostly_ exhausted.
Bullshit for any modern equipment (ie installed in the last 50 years).
It could also be that outdoor AQ is worse around you in the winter because everyone is running their boilers, and then that outdoor air ends up inside. I can't test it because I have a heat pump, but I would be curious to know what happens to your VOCs if you turn off your boiler at a time when your neighbors are still running theirs.
Mid-efficiency furnaces are still commonplace in the US, and they don't have sealed combustion systems - they get combustion air from the indoor space, but they vent 100% of combustion products out. High-efficiency furnaces in the US made in the past 30 years or so use sealed combustion with intake and outtake to the outside. (North American high efficiency furnaces older than about 30 years were not necessarily sealed).
But yes, the GP is full of shit. Maybe they have some other non-induced vented gas burning appliance (ie a hot water heater or gas hob), or their measurement equipment is faulty.
Or you live insulated from shitty alliances and low income life.
A friend's husband was killed by a faulty boiler, carbon monoxide poisoning. In 2015 I lived in a house where boiler ignition didn't work and you had to reach inside with a lighter. That unit was definately not sealed.
UK only required consenser boilers since 2005, the ones before that used to air from inside your house.
Condenser boilers and balanced flue are separate concepts. The house I bought in 1978 had balanced flue gas heaters but they were not condensing. Condensing boilers are an efficiency measure. Balanced flue boilers have been available in the UK since the mid sixties.
All I can do is share personal experience of living in rental properties in UK, and if these boilers were really sealed, my acquaintance wouldn't be dead.
Whether most boilers are prehistoric, or it's just years of neglect, I don't know.
But if we're going with the "heatpumps are more than 100% efficient" that everyone brings out, then running my computer to work & heat my room is far above 200% efficiency.
If I'm running my computer to use it & it keeps me warm, there is no way turning on a natural gas heater is going to reduce my costs.
Heatpumps are more than 100% efficient refers to a technical specification measure called efficiency, which is watts of heating per watt of energy input. For space heaters, electric furnaces, and your computer (/many other appliances), it’s always 100%. For modern gas furnaces it can be 90%ish (but the difference in electricity and gas prices mean that gas furnaces are still cheaper). For heat pumps it’s typically between 200% and 540%.
If you have a thermostat in your home, any appliances you use will reduce your heating usage because the thermostat will automatically decrease how much the furnace runs. So, yeah, it’s not wasteful to vent your computer exhaust outside in the winter, but no one’s doing that. On the other hand, it’s not worth it to run appliances you wouldn’t otherwise run unless you have an electric furnace, in which case it doesn’t matter.
Sure but why limit ourselves to "which is watts of heating per watt of energy input." Wouldn't "amount of useful work per watts of energy input" be OK? So if I am putting in 100 watts constantly to my PC I am getting 100 watts of heating & 1 unit of computing. Which is more than 100%
In the summer, my heat pump water heater in the basement is essentially 'free' to run, since most of the heat it captures is by condensing water in the air i.e. dehumidifying my basement. I still need a dehumidifier, but it doesn't have to run as hard.
This is the first year where heating the home with gas isn't an order of magnitude cheaper than with electricity here in the Midwest. Gas still wins, but not by as large of a margin!
I think 100% is pretty accurate for most devices, except for washing machines and other gadgets connected to the sewer. Where else would the energy go?
Your fridge has the potential to go even higher than 100%, as it's a heat pump. But for more than a temporary effect you'd have to keep replacing the stuff inside it with stuff warmed up to outside temperate, which would have to be between fridge temperature and room temperature. Perhaps slightly impractical.
Get buckets of water from your pool (or lake or well) and put them in the fridge till they cool down. Then dump the water outside and get a new bucketful).
To save effort you could run 2 hoses with a small pump.
You are now heating your house with a ground source heat pump.
“100% efficient” doesn’t tell the whole story of the gas bill if you’re heating your house with something cheaper than electric heat (e.g. natural gas).
It's not about fault at all - I'm just saying that the analysis does not apply to lightbulbs. For a lightbulb to be as efficient as a resistance furnace at heating a room, you would need to have zero light escape that room so that all the light would be converted to heat. Then, the heat would leave the room at the same rate as heat generated by a resistance furnace.
Even if we consider incandescent light bulbs, which waste most of the energy they use as "heat", that heat is actually being transferred primarily through radiation, so it can escape through windows more easily than the heat that a furnace transfers to your indoor air.
I assume by “thermal infrared” you mean the IR produced by approximately room temperature objects. Incandescent bulbs produce much higher energy infrared because the filament reaches about 2000 Celsius. Those higher energy waves can go through glass.
Natural gas furnaces are designed to not let that light out. Instead, the light is absorbed by the surfaces of the furnace and turns into heat. The inefficiency in gas furnaces is heat leaving in the exhaust.
The smart thing to do in winter is put municipal liquid water in your freezer, and dump it outside once frozen to thaw in spring. Rince repeat all winter long.
Voila: everyone has heat pump heating! (And dead compressors).
The dumb thing is having the compressor itself indoors in summer. Should be outside.
The issue with that is that if it’s outside, you need a hole in the wall somewhere to connect it.
Today fridges are more or less plug and play. Most kitchens don’t have a hole in the wall going outside where the fridge would go. Some kitchens aren’t even on walls facing the exterior (which I dislike, but they exist)
Interesting, how to remove it easily from the container? Or do you use an ice machine? Is this more efficient than using the heater? Guess it uses heat pump tech.
The fridge isn't the biggest energy hog in the house, but I'm very sympathetic to the absurdity of heat levels in a house.
I often see my HVAC cooling when the set-point temperature is actually _higher_ than the outside temperature. Logically, the house is a heat generator, it makes sense physically. The roof is black, etc.
It would offer a good number of benefits if the system could outright open a duct to the outdoor air, and suck it in whenever the local outside temperature is within the range requested by the user. People who are into optimizing energy use (they exist) can go even further and pre-cool their house during the night in summer.
For this to work, all you need a pusher fan, no refrigeration at all. There might be some pressurization problems, like, you may need a duct both for the intake and outlet. Also might require another filter... but air quality would improve significantly.
This is a really "dumb" idea, but it's perfectly in-line with all the new ideas being thrown out there. The new ideas just tend to throw in an additional heat storage mechanism, like a water tank (in the article). You can get a lot more efficiency gains by saving the night's cold in a tank and using it through the day. But on a more basic level, you can pump straight into the house when the conditions are right.
I've built/retrofitted and a prototype of mechanically operated louvres with push/pull fans for air exchange in an old school building, tied to the thermostat, ac, and a CO2 detector.
The idea of doing the same in my home has been taunting me for years now. Ideally you'd have two such louvres, one with a push fan in the upper floor and the other with a pull fan in the lower floor to simultaneously eject unwanted heat, bring in fresh air, and boost whole-house circulation. They'd be set up to interface with the thermostat/hvac and would operate when the outdoor temperature at intake is lower than the temperature at exhaust and both are above the set point on the ac.
The biggest problem is really one of convenience. You'd need a filter on the intake and a rather large and powerful fan to overcome that static pressure - ergo, a noisy one. And you'd probably have to fully dismantle the system in the winter to prevent the cold from getting in (the Midwest is cursed with both hot and humid summers and cold and dry winters). It just end up being the kind of thing where the devil really is in the details and you either do it right and it's a huge undertaking or you do it fast and sloppy and its drawbacks won't be worth it.
But I agree, nothing is more infuriating than seeing the AC on and the outdoor air temperature being lower than that of the home. And opening windows just doesn't make a difference since in most 20th century homes there's just poor airflow and no circulation.
I was thinking a big vertical heat pipe that sticks out like a chimney would be great for this and keep inside+outside sealed.
When it’s colder outside, liquid will evaporate on the bottom and condense at the top through gravity. Once it’s warmer outside, the whole process just stops.
No valves, no pumps, no analog or digital controls. Ok, maybe a fan.
I actually want a fridge/freezer at the cabin that works like this in fall/winter/spring. I know it’s technically moving heat from inside to outside, but I’ve got more wood than electricity to work with.
I've often wondered if opening windows while AC is running and outside temp is below inside temp is less efficient than keeping them closed.
My thought is I should keep them closed due to extra load on the AC to dehumidify the outside air. Or open windows and turn AC to fan-only mode to prevent stagnant air in rooms without windows.
Unless you have a very strange setup, centralized A/C does not have humidity sensors nor run just to dehumidify. Nor does removing humidity increase the load on the A/C system. Removing humidity is just a happy by-product of how centralized A/C works. So no, you would not be increasing load for that reason.
The above comment is incorrect, even for systems without integrated dehumidifiers. AC systems absolutely do have a higher load with higher humidity because ambient water will condense on the evaporator coils if the dewpoint is higher than the evaporator temperature (which it typically is).
That said, it still may be more efficient to open your windows, depending on the humidity.
I stand corrected. Apparently 60% humidity or so is the line. That said, I live in Florida and haven't ever had an issue, but maybe that's because the A/C runs so much anyway...
FWIW I had a new Lennox heat pump installed a couple years ago, and I can (but don't) configure it to "cool to dehumidify", and it tells me the humidity on the thermostat. I don't know if this is common in new units, or if I'm just special.
Based on some of the home building and HVAC videos I’ve seen on YouTube, it seems pretty common for high-end new home construction in the U.S. (especially the south) to have separate AC and dehumidifier units.
Right. It takes into account both temp and humidity and either can trigger the cooling. It is a two stage system, so usually on the first stage is enough to get the humidity low enough to feel better.
Happy in some times, unhappy in others. There are days I'd love if the A/C would have a humidifier built-in, for those winter months when you might want to use A/C to warm the interior.
A good chunk of the United States (and a number of other countries) uses forced air natural gas heating. If you fall into that group, you can install a "whole-house humidifier" that injects steam into the hot air plenum, distributing it around the house. This makes the air less dry (obviously) but also has the side-effect of actually reducing the need for heating because air holding moisture feels warmer than air without (hence the oppressive heat in the humidity of summer), meaning you can lower the thermostat.
Unfortunately I have only seen commercial humidification units that boil water into steam with the use of natural gas. Without exception, everything for sale for home use uses electricity (you'll need 230V minimum, single phase will do just fine) to boil the water, which is costly (though this year natural gas prices have risen or even doubled, but even in states with cheap electricity it's probably still cheaper to use natural gas).
The moisture can promote mold in the ductwork though. We had our furnace replaced a few years ago and had the central humidifier removed. The interior of the ductwork was black with mold near the humidifier so that was also replaced.
Be careful you’re not running it independently of whether or not the furnace is actually on. 120V generally can’t evaporate enough water in the short window while the furnace is running and many techs will set it up to run at all times (with the blower but not the furnace) to compensate. This lets mildew or mold grow in your ducts.
One of the Daikin models for Japan apartments/condos (known as mansions) has a tankless humidifier; it is able to condensate humidity from outdoor air and introduce it into the home. On a cold winter day it is able to raise the relative humidity from around 30% to about 45% or so. うるるとさらら is the name of their series of things that humidify.
HVAC can do that and it’s not too expensive. You do need to run water to your unit though and there’s quite a bit of maintenance as humidifiers create mold, etc.
Some AC units have two modes - cooling and dehumidifying. When in cooling mode it will blow a lot of air to keep evaporator as hot as possible, so less humidity is condensing on it (but there will still be some). In dehumidifying mode it will blow less air but keep evaporator cool, so more condensation for the same amount of air cooling.
Source - I have Kaisai mini-split at work and I've observed how each mode works (with my hand). There's probably more energy used per cooling amount during dehumidifying, because it's bigger temperature differnce (which means lower COP) PLUS condensing water (water phase change energy is big).
You are exactly describing a HVAC "Economizer" as they are called. I believe they are almost solely used in commercial HVAC installs, probably due to price/additional install complexity? They are very neat though, and do save significant energy in shoulder seasons, or at night in the summer as you mention.
The function to just bring outside air when it makes sense is an extremely common feature in commercial HVAC systems - it’s called ‘night purge’.
Most of these systems have a damper that the system can use to choose how much fresh air is used or how much return air is recirculated so it’s not difficult to use that to just put fresh air in directly with no cooling or heating. Even systems with heat or energy recovery will often have a bypass damper.
You need the humidity to be in the right range as well as the temperature, but it can save a lot of energy!
You'd need one of three solutions to make this work:
1) Long refrigerant pipes. This is unacceptable because it increases the amount of refrigerant in the systems (refereed to as the charge of the refrigerant). Refrigerants are powerful greenhouse gases so it is important to design low charge systems.
2) Another process fluid (e.g. water or glycol). This adds expense (more pumps and heat exchangers). You'd increase the cost of all these systems by a lot.
Also, both 1 and 2 involve running a new set of single use pipes around your house.
3) Make a "single appliance" household. A design like this has been tried - single AC/heat pump hooked to fridge, freezer, oven, dishwasher, washer/dryer, and water heater. The problem is that you really have do design the house around this and it is quite limiting from an architectural perspective.
Combined AC/heat pump and water heater is a thing though.
Adding to (2), I've worked with liquid-liquid heat exchangers (large heat/chiller units for chemical reactors) and they are super quiet and efficient, but boy howdy, are they messy and high maintenance. The glycol lines leak, the water supply leaks, the water needs to be screened and the screen needs to be changed.
Air-sourced exchanger individual appliances are just so much simpler for the consumer.
Not dissing ground-source heat pumps. Those are fine, since they are typically a plumb-once-and-done. You just generally don't want separate appliances which quick-connect.
> Why can’t my whole home participate in this technology? It would seem an ok fit for things like freezers, refrigerators, hot water heaters, etc.
At large scale (think like walk-in coolers of supermarkets), this is actually being done in the form of district cooling [1].
> Someone needs to make a standard for moving heat/cool through all appliances in a house…
The problem is that the piping itself and the circulation required are sources of energy loss, and it's hard enough to keep these appliances sealed so they don't leak their coolant - most coolants have insane CO2 equivalent potentials. It's not worth the effort.
It is technically possible. I had the same thought as you and looked into it some time ago. The only references I ever found to it actually being implemented were in cases of giant walk-in (even warehouse sized) refrigerators/freezers in places where district cooling exists.
For something the size of a home fridge the costs would be immense compared to the energy savings. You're far far better off spending that money on more efficient heat pumps and more/better insulation.
The federal limit for the amount of power a fridge can pull is 527 kWh/year, which at my rates (admittedly on the low end these days) is ~$70/year. There are very commonly available fridges that are < 300 kWh/year, which would be ~< $40/year. So before even taking into account the efficiencies you implicitly make back when you're heating your house anyway, that's your per-attached-appliance limit for input cost on building out, maintaining and running that system.
Though, I admit that the idea of a completely silent fridge & A/C is alluring. Here's to hoping we make some breakthroughs on sold-state heat pumps.
The good news is that the process of running your fridge moves the heat from the fridge into your home, which in the winter is not such a big problem. Your fridge is just another heat pump. It's a bigger problem in the summer when you are maybe trying to cool your house using air-conditioning and your fridge adds heat to your house to keep the fridge cool. Much less desirable.
actually, that makes the room warmer. Your fridge just becomes a bigger heatpump with the door open. the compressor has to work hard to cool a larger area, so therefore uses more electricity and dumps more heat out into the room.
They move the heat from inside the fridge to outside. That heats up your home. This reduces your need to heat your home, temporarily.
Generally, every device in your home that uses electricity is creating roughly the same amount of heat as an electric heater would have using the same amount of electricity. Even fridges and freezers, so long as nothing is being vented outside.
This is one of the bigger myths used to sell tankless. Modern water heater tanks are well insulated; losses are usually quoted as less than 10%.
From a cost perspective, the slight efficiency increase of tankless never pays back over the cost of the unit, and unfortunately, usually the more frequent repairs. The big benefit is the 'unlimited' hot water.
Devices are beginning to appear that can move the waste heat generated by home AC compressor into the pump loop for a swimming pool outside that same home, getting your pool heated for free by cooling your house, and your aircon cooling becoming much more efficient by using your swimming pool as a giant heat sink.
However unless the house was built, and / or the pool installed in a coincidentally fortunate configuration where the AC compressor and the pool filter pump are within a meter or two of each other, these devices cannot be used effectively due to impractical tolerances and insulation needed to mitigate losses from contact with the highly variable outdoor environment.
> nd the pool filter pump are within a meter or two of each other, these devices cannot be used effectively due to impractical tolerances and insulation needed to mitigate losses from contact with the highly variable outdoor environment.
that makes no sense. effective insulation is no problem at all. In large parts of europe they even have centralized water heating and run insulated hotwater pipes to houses across kilometers without huge losses, hell, for this kind of setup it would even be possible to just run refridgerant, which typically specs at ~15m for minisplits as maximum(with very minor losses) distance
Note that this is only an advantage in cooler months, and does work against cooling your home in hotter weather. In principle it seems like we could could build our refrigerators into an outside wall (like iceboxes once were) and then expose the coils in summer, and enclose them in winter.
Not really, efficienty aside the heat it puts out the back is coming from inside the fridge... Which is coming from the room housing the fridge. So over the course of a day it should be neutral.
I think you are looking for (one specific implementation of) Cold district heating.
It can be implemented as a single line of force water flow with 20-25 Celsius. It is viable as both a heat source and a heat sink at the same time.
This thing can be connected to both your coolers and heaters, and thus transfere heat from one to another. Maybe you could even get you desktop computer into the loop.
Usually it implemented on a lager scale, but i don't see why this would work scaled down.
In order to cool your refrigerator, the system has to have a place to the put the "hot" it just extracted. And that place is your house itself; your freezers and refrigerators are warming your house and contribute just like the radiators you installed. So the losses are not as big as you expect them; the money you spend on those appliances also lowers your heating bill.
> the money you spend on those appliances also lowers your heating bill.
It should net out to no less than the same energy though, right? That refrigerator needs energy to move the heat out of the fridge and into the home. If that process takes more energy than just letting the house HVAC deal with it, wouldn’t the energy bill be higher?
When it’s freezing cold outside, it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated.
Someone needs to make a standard for moving heat/cool through all appliances in a house…