In addition to a heat pump, I wish my HVAC had a filtered vent from the outside and would be intelligent enough to sometimes just pump in cooler or warmer air from the outside when viable.
I don’t like having to shut off my furnace and manually manage windows. But I also don’t want automatic windows. I just want it to be like, “you’re asking for 21C and we can get there by pumping in outside air rather than using an AC to transfer heat from the inside air to the outside air.”
We installed something like this, but for the purpose of getting fresh air into the house (instead of circling stale air over and over and increasing the CO2 levels). Our setup is:
Fresh air / circulated air -> Perfect 16[1] -> HVAC
I highly recommend it. You can also get an ERV or HRV to utilize heat/humidity when bringing in outside air.
Matt Risinger explains how and why he put an ERV in his house in this episode of The Build Show https://youtu.be/OrG7oG8Tvp8. It seems to be the thing to do of late in to help with air exchanges and still meet the passive house standards.
I read that page, and that sounds like a MERV 16 filter than attaches to a third party fan coil. I can’t tell how it’s any different from, say, an Aprilaire 216 plus its (very cheap) housing, along with smart home integration and a pretty logo, minus the transparent pricing.
One of the differences is how hard you have to push against a regular MERV 16 filter vs. this one. You can generally install a Perfect 16 into an HVAC without having to adjust its settings and thus how much energy is required to run it. I haven’t looked at the April Aire stuff in a bit, so don’t know if they happen to do something similar, but I was looking at a number of different options for a much larger building install, and you can generally price the P16 without having to factor in energy price increases.
The 216 filter has 0.17" wc of initial pressure drop at 1000 cfm as compared to 0.12" wc for its MERV 13 equivalent, the 213. You can just swap it in if you started out with MERV 13 [0] have 0.05" wc of extra pressure budget (and an existing compatible housing), and you can probably save 0.05" wc by just changing your filter more often. Or you can design something like this into a new system, just like you would have to design a Perfect 16 in.
[0] You must have some kind of return air filter to avoid destroying your fan coil. MERV 13 is somewhat of a baseline for a decent system.
That’s… a lot more expensive than Aprilaire for only slightly better performance. Two or three Aprilaire (or Lennox, etc) filters in parallel will dramatically outperform the Perfect 16 and will cost much less. Of course, that would require some custom sheet metal, but the Perfect 16 may also need some custom sheet metal.
The beauty of a real ventilation system is the heat exchanger. I’m still waiting for someone to make one that I can run by feeding a tube out my window, but until then, you need to spend a bit of cash on a permanent installation.
You might try buying two CPU coolers with fans and connect them together via their heat sinks with the fans pointing in opposite directions. Then build a housing for it to match your window. That should transfer some of the heat/cool from the outgoing air to the incoming air. Put a filter on it to keep bugs and pollen out of the house (including the outgoing fan because you might turn it off sometimes. It needs at least a no-see-um size mesh screen.)
Dunno either. Should be no issues in flipping the whole unit around. Controls/weatherproofing would be on the wrong side. Put some nice indoor plants underneath it because they'll now be self-watering.
That's kind of the flipside of what OP is describing. OP is saying if it's colder outside than inside, and you want it to be colder inside, the unit would intelligently just pull in unprocessed (except filtering) outside air.
An HRV or ERV is designed to pull in fresh air without losing heat from inside (or while keeping the heat outside in the summer), by transferring heat between the air being drawn in and that being exhausted.
My heat recovery ventilation system does exactly that. It has a bypass valve to just suck in filtered air when needed, bypassing the temperature exchange mechanism.
Yes - these are necessary in houses designed to minimise air leakage, because without them they can end up so well sealed that they do not allow enough air changes per hour.
The cheap DIY is to add WiFi switches to your bathroom fans, turn them on when humidity is lower outside or when the outside is cooler than the inside.
WiFi? Eh. As an ever-so-modest upgrade to the cheap DIY, a Zwave or Zigbee system might be a better choice to integrate with a variety of other things (like thermostats and temperature/humidity sensors.)
Most WiFi switches are based on ESP chips. Meaning they are trivial to install custom firmware on to extend the functionality. I haven’t found any affordable Zigbee or Zwave switches of this kind. Meaning that all the smarts need to be programmed centrally instead of putting them locally on the switch itself.
In my house.
9 X main lights.
Kitchen work lights.
Extractor fan.
Oven
Hob (gas)
Dishwasher
Washing machine
Dryer.
Fridge.
Freezer.
Food processor
Kettle
Toaster.
TV.
Digi box
PlayStation (2 but anyway)
Extractor fan
Boiler
Laptop
Printer
5 X lamps.
So I managed to get to 30 things. I'm not entirely sure I'd want to hook up all those things to a network though...
Zigbee also runs on 2.4GHz, but I wouldn't even count WiFi out just yet since those devices are on 2.4GHz where latency and throughput are almost irrelevant (to me) for that application. Plus it's usually cheaper.
The problem is that lots of little wifi devices on your network will slow down everything where latency and throughput is relevant. I guess WiFi 6 will "fix" this, so maybe I'll be wrong when light switches are all WiFi 6, but I'm right for now.
Also, latency is very relevant for IoT stuff. Lights turning off 2 seconds after you push a button is a crappy experience.
Presumably you're doing this to pull in air from the outside using negative pressure? I heard this approach isn't optimal because negative pressure means that you'll be pulling in air through the various gaps/crevices in the walls, which is dirty and might have contaminants like mold.
Doesn't this warning then suggest that bathroom ventilation fans should never be used? And should be removed from houses (and building codes) at all expediency?
The suggestion isn't to turn them on continuously (as this would also wear the motor) but in situations that are similar to that of when showering (high humidity or temperature)
Yeah it makes me really upset when the outside dew point is lower than inside (often in the fall) and I've got to dig out my lasko box fan and run it in the windows.
There are several kinds of HVAC systems for fresh air ventilation and free cooling (HRV/ERV) and it was a huge bummer to hear an ac expert say "your tiny house's tiny closet has no space for any new toys at all"
Not to be really dumb about this (I don't have a heat pump, don't know exactly how they work, but have some interest in getting one) -- is it not possible to shut them off entirely for the fall? Are they hard to restart or something? Is it like the obnoxious car systems that always want to be giving you either heat or cool and just refuse to do nothing when it's nice out?
They can easily turn themself off and restart easily.
GP was wanting to take advantage of the more favorable outside air (lower sensible and latent heat) and just do filtered air exchange directly with the outside rather than running the compressor.
I think the main problem would be humidity issues. The outside air swings so wildly in humidity. I was growing weed outside in my state and surprised to watch the humidity on the meter regularly go from 21% to nearly 100% on day night cycles.
Look at dew point or some absolute humidity measure instead. As air gets colder, the amount of water vapor it can hold (the denominator in relative humidity) decreases dramatically.
Introducing cold, saturated air to your warm house will not, in general, make it feel nasty and humid.
I can only barely understand what’s going on in that link, but I think it really depends on target indoor environment.
While I don’t want the walls sweating, I could imagine there are industrial or commercial environments where moisture level matters a lot. Electronics plant: dry is always bad! Want some moisture to dissipate static. A library wants low, but not zero moisture. A manufacturing plant wants it to be very consistent. A fruit market wants its humidity high.
In a residential environment, it’s a toss up: some stuff wants to be dryer while other stuff doesn’t.
I don’t think you’re likely to make the walls sweat by running an economizer or, for that matter, opening a window while it’s cooler outside than inside. You may end up with more humidity inside than you like, though, depending on the weather.
That link seems to be discussing a situation where there is too much humidity coming in relative to the amount of heat the A/C needs to remove, and that hits my pet peeve about air conditioning design. Air conditioners generally run at a roughly constant coil temperature, which means that there is no independent control over dehumidification versus cooling. If you happen to be at the design conditions, great. Otherwise you don’t end up with the humidity you want.
I know of one system (“dynamic humidity control” by Chiltrix) that adjusts the coil temperature to control humidity. As far as I know, any hydronic system can do this with minimal modification, but I don’t think it’s popular.
I have a similar issue with thermostats in general: set points without a humidity coefficient is a constant battle. 26C and dry is comfortable: Stay off. 26C and humid is sweltering: Power up.
My "smart" thermostat has a settings for this, but I seem to be at its algorithm's mercy instead of specifying: "50% RH or less, no change, 50-70%, -2C to the set points, 70%+, -3C to the set points".
This isn’t entirely a problem with your thermostat. If it’s 26C and humid, all your thermostat can do is to call for cooling. (Maybe it can call for stage 1 or stage 2. You are unlikely to have anything that can do stand-alone dehumification.) So it can’t actually achieve a comfortable and efficient target.
If you're in a climate where that is a problem, the solution is to use an energy recovery ventilator (ERV) along with your air conditioning to use the conditioned inside air being exhausted to pre-treat the incoming air using an enthalpy heat exchanger.
Heat recovery ventilation (HRV), which uses a sensible heat exchanger, is sufficient in temperate climates but otherwise you need to be able to transfer latent heat also to reduce humidity, so need the ERV.
It’s called an economizer and is controlled by enthalpy sensors. Look into honeywell jade system, if you are handy then you can DIY it. Controllers are super cheap on ebay. Just be mindful of air balance.
Really? I live in a mostly not very well-insulated 200 year old wood construction farm house and I find that there can easily be a 10 degree F delta between indoors and outdoors. I have heat for the winter given northern climate but otherwise mostly just do regulation by opening or closing windows.
One thing to remember is that when the air outside is already warmer than the air you want to heat or cooler than the air you want to cool, this will significantly increase the efficiency of the heat pump in achieving that temperature. I would guess to the point where it's not worth complicating the system in this way. (Especially since it will be a relatively rare compared to the reverse situation.)
You can get this in a lot of places, with units that use the inside air to pre-condition the outside air being brought in so you're not destroying the efficiency of your HVAC system. It's called Heat Recovery Ventilation (HRV) or Energy Recovery Ventilation (ERV). Units exist for small residential buildings all the way up to massive commercial units. HRV is used in temperate climates where the humidity outside is generally not a problem, and ERV is used when the outside air needs to be dehumidified also.
It's not usually a feature of residential units, but commercial ones also have a bypass for when the building management system detects (using sensors like wet-bulb thermometers) that the outside conditions are fine to bring inside, which is called the "economy cycle". It switches off the baffles to the HRV or ERV and just brings the outside air in directly.
If somebody was really interested, that could be implemented at home with some extra ducting, some controllable dampers, sensors, a Raspberry Pi, etc.
This “Smart Window Fan” is a window-mounted economizer. If it’s cooler and dryer outside, like at night, it opens its louvers and pulls in cool air and exhausts warm air. It also has a HEPA filter. I assume it has humidity sensors too to avoid running when it’s humid outside.
I am wary of a product sold by only one vendor. Economizers tend to be added to large central ducted commercial HVAC systems and this is the only window unit I’m aware of.
> In addition to a heat pump, I wish my HVAC had a filtered vent from the outside and would be intelligent enough to sometimes just pump in cooler or warmer air from the outside when viable.
Hell a modern AC can probably do with only filtered venting, with a heat exchanger which gets disabled when using external air to get to the target temperature.
Thats an interesting idea. Where I live I think you would have to have significantly colder air outside to compensate for the humidity of just bringing in outside air, unless if could be dehumidified. I think there would be a limited window of usefulness.
It feels obligatory to reference Technology Connection in a thread about heat pumps. TC is a super fun YouTube channel that digs j to everyday technology and has had a number of episodes on heat pumps and modern thermodynamic management challenges and technologies.
The TC channel is definitely a hacker's eye view in to all the technologies that we take for granted every day. Tons of fascinating tech history covered, too.
- why dishwasher detergent packs are stupid (use powder/liquid) and why you should use the pre-wash slot and not bother pre rinsing your plates https://youtu.be/_rBO8neWw04
I take his stuff with a grain of salt because I found the dishwasher detergent recommendation to be a bad idea.
A while before the TC video came out, I had an appliance repair person working on my fridge and asked him what he thought the best detergent was and he said use powdered, not the packs. So we switched to that.
Not long after our dishes were never getting cleaned. I thought it was a problem with the dishwasher so I took apart the filter, cleaned all the sprayers, etc. but nothing worked. Was thinking we needed a new dishwasher until one day we ran out of powdered detergent but had a couple packs left over so my wife used one.
Bingo! Our dishes came out PERFECT. We haven’t had a single problem since.
What kind of powder are you using? Some really cheap powders are basically just sodium carbonate and silicate, with some enzymes, and no actual detergents. These won't work well if your load is "too clean", as it needs some grease to saponify in order to generate detergent.
The medium/high quality stuff contains more/better detergents,
water conditioners, and sometimes rinse aids. The packs are just powder formulations pressed into a pellet.
I mostly used Cascade Complete powder (there was a point early in the pandemic when I had to grab whatever was on the shelf) and use Cascade Platinum packs.
A couple months back we ran out of packs and had some powder leftover, so I ran a load with the powder. I ended up having to run the load again once we got the packs.
Quite the contrary for me. I suppose your powder detergent might be of lower quality than the packs one, or is not as concentrated and you need to use more of it?
I, too, had to adjust the amount of powder. Roughly 1/2 of recommended dose goes onto tray, and an additional 1/5 directly into the washer for prewash cycle.
I used Cascade Platinum packs before and after trying powder. When using powder I primarily used Cascade Complete (there was a short time early in the pandemic when I had to grab whatever was available on the shelf).
I tried the 'add detergent to the pre-wash-cycle' part. While it seems to make sense, it also caused a lot more rust spots on cutlery. The detergent is just too aggressive that way.
the goal is to use the cheapest not the most expensive... my miele tablets were destroying my duralex picardie big time, so I now use the cheapest powder and if I feel like the stainless steel don't shine bright enough (maybe once a month) then I use one miele tablet...
Detergent packs in the US seem to be mostly gel packs. In Germany, most tabs are simply hard pressed powder. Gel packs did fail in their cleaning function and the recommendation generally goes for either tabs or powder, where powder can save you money because you set the dosage according to how full your dishwasher is.
How much extra time does it take to dump out some powder? I don't actually measure precisely and just eyeball it. The advantage is I can dump some extra in the bay to act as pre-wash. The cost is 4-10x more for the self-dissolving packs.
Most dishwashers are designed to do a pre-wash, change the water, then do a wash. Pre-wash requires detergent to work optimally, ideally one specifically designed for pre-washing. Even dishwashers which have no pre-wash detergent dispenser will typically tell you to add some detergent directly on the door in the instruction manual. Most packs are suboptimal for that. Technically they should be used in addition to pre-wash detergent but that kind of defeats the point of using a pack.
Best advice I learned from that channel was to run the sink faucet until it’s hot. Then run the dishwasher so it starts its cycle with actually hot water.
Hmm, dishwashers I have had (including my current one) have a large heating element in the bottom, I would have thought that could heat the relatively small volume of water in there pretty quickly?
Most (actually all) dishwashers that I've encountered are designed to not get hot water coming in. Where I live a high-pressure hot-water outlet is not the norm at all. And yet, we don't have a catastrophic country-wide problem with dirty dishes. I'd argue that something else it at play.
When reading many of these articles always miss a condensed explanation of what a Heat Pump really is. In some countries they are common, while in others, seems they are very rare.
TC have a wonderful presentation, but like all YouTube channels, should be taken with a grain of salt. TC made a fair share of errorenous claims, some of which they addressed in follow up videos (definitely not all). One example they never addressed was in their dishwasher video where they explained how a dishwasher worked (which was good) and then pushed to stop using capsules in favor of soap powder. Using powder requires more maintenance because you'll have to buy special salt and run your dishwasher with it but this was never mentioned in the video. The capsules have this so you don't have to add anything else. If you followed their advice blindly, you could damage your dishwasher. Ask technicians what to use and they'll all say the capsules are better for your appliance. Always trust professionals over YouTube videos.
The salts issue was actually mentioned in a follow up video [0], with the note that only homes with specific water types (excessively hard water if I remember correctly) will require them.
It seems odd to account for hard water in one appliance but not another.
I’ve lived in places with hard water and most people have a water softener right next to their water heater so that all water to all appliances in the house is softened.
He says in the video only 1/4 of US homes have softeners.
Every dishwasher I’ve had in Europe has a salt compartment. I can’t remember the ones I had in the US to have a salt compartment. I’d wager the powder and pods in the US have some salt in them to make up for that?
"The capsules have this" is only kinda-sorta true as is "special salt".
Lets do "special salt" first. What you need is Sodium Chloride. Commonly: salt. The manufacturer tells you to buy "dishwasher salt" but all that is, is a bag of salt. Why not say just "salt"? Well, the table salt you might buy comes in lots of fancy and/or tweaked varieties which are not ideal for the machine, yet they are more expensive. Instead of buying ten smaller packs of "Genuine Himalayan Rose Salt" for $1.50 each, you should buy the same amount of just regular sodium chloride labelled "Dishwasher salt" in your supermarket in one packet for like $1. As well as irrelevant or potentially undesirable minerals to make it pink (for some reason) salt for food might have a packaging stabilizer, an ingredient added to make sure it doesn't stick together, and iodine salts because sometimes humans don't eat any iodine and if they don't their thyroid gland doesn't work properly which is bad so some public health authorities have local salt tweaked to fix that (salt is chosen because it's really easy). So yeah, TL;DR it's literally salt, it's not special.
Now, do "the capsules have this". Well, they all say they solve this problem, but of course they say that, a manufacturer isn't going to advertise their product and say "This product is pretty bad really, you probably shouldn't use it". Every manufacturer of "flushable" toilet wipes says their wipes don't cause sewer blockages. The blockages happen. Maybe all the other brands are lying except yours?
Here's why they don't really solve the problem, what your dishwasher wants from salt is a source of ions to re-charge its water softener. Sodium Chloride is (if you remember chemistry class) Sodium ions and Chlorine ions, the softener wants the Sodium ions, it will swap them with the ions from the hard water, softening it. But how much softening is needed? With bulk salt in the machine you don't care. Once a month (or even once a quarter) check the salt, if it's low fill it back up, done. But in a capsule there must be enough softener for each load, or else it gradually gets worse.
Now, it can happen you live somewhere that the water is exactly as hard as the capsule manufacturer decided water should typically be, and for you they work perfectly. Most people don't.
Is it really table salt in big chunks? I didn’t realize… I’ll dig up the MSDS tomorrow but if so I guess I’ll just refill the dishwasher with coarse salt next time I guess rather than the dishwasher variety.
I've never seen it in "big chunks" but sure, the dishwasher doesn't care, it just wants Sodium Ions.
It seems weird if "coarse salt" is significantly cheaper where you are than dishwasher salt, the main cost difference I'd expect is that the "dishwasher salt" manufacturer is like "This isn't food, so I don't need food inspections" which would make their product cheaper.
I checked my usual suppliers, if I want fancy salt, because I'm stupid, crazy or rich, I can pay up to £40 per 100 grams for special "black salt" which apparently has rare minerals in it and presumably is aligned with my spiritual ancestors or something?
If I'm content with just salt, NaCl, ordinary crystals of sodium chloride, that's £0.10 per 100g. I could put that in a dishwasher but...
If I want dishwasher salt, that's £1 per 1kg, which is the same ratio but larger sizes because unlike fancy specialist salt, nobody buys 100 grams of dishwasher salt.
However, do check your "coarse salt" is actually just salt, it probably doesn't matter, but the manufacturer doesn't design the machine to have, for example iodine in it, which is often in the table salt in places where iodine deficiency causes medical problem, or an anti-caking agent (to stop it forming "big chunks" when you want to sprinkle it on food) or other food ingredients.
I recently bought my mom a dishwasher, so I can tell you that at least in my mom’s town, dishwasher salt is more expensive than regular salt. Perhaps because dishwashers are still a luxury product, so everything related is still more expensive because those who need them can buy them at these prices.
Just verified, dishwasher salt is almost 5usd/kg. Coarse salt is .75usd/kg
Regardless of implementation, a heat pump is basically a reverse air conditioner: taking heat energy form outside and brining it in your house. The main components are also the same as an AC: heat exchangers, a compressor, refrigerant fluid and piping.
Where exactly outside you tap in for that heat energy and how the outdoor heat exchangers look like varies depending on implementation, but the principle is the same.
Although to be more exact it's a reverse engine, where an engine is a device for turning a temperature gradient into work, and a heat pump is a device for turning work into a temperature gradient.
In this view air conditioners are a kind of heat pump.
>Is there any meaningful difference between a heat pump and an air conditioner, other than the direction the heat is pumped in?
In terms of basic science, they are the same principle so "air conditioner" is a type of "heat pump".
But in terms of semantics that is understood by the general public for purposes of differentiating various HVAC equipment one can buy, a heat pump has an extra reversing valve to change the flow of refrigerant. A standard air conditioner doesn't have that extra feature.
When folks casually say "heat pumps", they're talking about a HVAC equipment category and not general science principles.
US people call them heat pumps because they have been calling the non-reversible cold-only kind “air conditioner” so they needed a new term.
In Europe most units are reversible cold/heat unit so “air conditioning” means making air both colder and hotter. We would call the ACs the Americans have “air coolers”, if we needed to make the difference.
It’s basically a reversed refrigerator. In the box heat get pumped out from a power temperature to a hotter one the room. Open your fridge door to the outside and the radiator into the home it’s done.
An heatpump is either an Air Conditioner (which is really jusf a refrigerator) running in reverse, or an A/C with a reversing valve so it can move (pump) heat in either direction, depending on the application. Heat pump driers and water heaters never cool the clothes or the water, but home heat pumps are almost always setup for heating or cooling.
For heat pumps to work, you need well insulated houses. This means you're more likely to get them in colder environments (Canada) than more temperate ones (here in the UK)
It sounds like something fancy but it’s common where I live. It’s usually hot all year round so it made sense to buy an air conditioner with a heat pump built in. Although it’s been a few years since we last turned it in because it’s never cold enough to justify the electricity usage given the always high prices here in Europe. So perhaps it doesn’t even work anymore :P
Your refrigerator is a heat pump. If you put something warm in there its heat is drawn out to the environment heating your kitchen. A refrigerant is used to achieve this. When it’s pressure is reduced it will evaporate absorbing thermal energy from its surroundings to change phase. When pumped around it’s circuit and compressed and accordingly condenses releasing all that energy to its surroundings. The electrical energy required pumps the fluid and drives the compressor. Of course there will be some heating due to heating of the mechanical components.
A lot of homes here in Ireland (and I presume elsewhere in Europe) must be built to an ‘A level’ build energy rating. This typically means installing PV Solar or heat pumps. Rarely both.
My modest solar installation on my three year old house only provides about 40% of my electricity needs (typical daily import is 8 kWh and generation is 5 kWh). Winter is a different story.
Most heat pumps here are air to water systems. Homes don’t require AC here but you can get air to air systems that can heat or cool your home as needed. The benefit of a heat pump is it’s coefficient of performance (CoP). This is the amount of thermal energy you get out for electrical energy put in. A typical system can sustain a CoP of between 3 and 4. However this drops off as the outside temperature drops and you push up the heating demanded.
They should be as reliable and performant as your fridge or AC unit. So you many need to replace the pump or refill the refrigerant.
Another interesting technology is a so called solid state heat pump or thermoelectric module. These have an awful CoP usually much less than unity. They are interesting for thermal management due to their size however. You can aggressively cook a small high-flux component and then deal with the thermal load form the hot side of the TEC with a big cooler. You can even stack them. Their efficiency increases as the temperature difference goes to zero so a stack with a small
temperature jump between layers can be better. They also work in reverse and can therefore be used to scavenge electrical power when you have hot and cold reservoirs. For example put one on the exhaust of your car and you can harvest enough energy to charge your phone.
> Your refrigerator is a heat pump. If you put something warm in there its heat is drawn out to the environment heating your kitchen.
I’ve tried to explain to people that putting something warm outside to chill in winter before refrigerating it costs them more in electricity and they look at me like I’m insane.
Parent is right, with some assumptions to be made explicit. Considering the reactions this deserves more explanations ;)
Let's say that the heat energy of the warm thing is "E" and the outside and fridge are at same temp for simplicity. Let's also assume that the house is not heated using a heat pump.
Consider the two cases:
1) The warm thing is put into a fridge. It's a heat pump, with coefficient of performance C. To cool the thing the fridge will consume E/C, and E will be released as heat inside your room. So you paid E/C of electricity to get E Joules of warming in your home;
2) The warm thing is put outside. The energy E is wasted outside, and then the piece put into the fridge with no extra cooling there. No energy spent by the fridge, but no warming of the house either. To do a fair comparison with the same final state, we need to add E joules of energy to heat the house, which will require E Joule of electricity or primary energy (because no heat pump to heat the house).
So to reach the same point, in case (1) we spent E/C of heating energy, and E in the second case. It is indeed more efficient to put the warm thing directly into the fridge, as this will contribute to heating the house with the efficiency of a heat pump.
And if you heat your house with a heat pump of same efficient C, you don't care either way: it's equivalent.
You’re going to have to explain your reasoning to me there.
If your fridge is at 4°C and you put something in there at 21°C it will have to transfer an amount of Joules of thermal energy to the internal environment and then the fridge will have to transport that energy out to the kitchen. The amount of energy depends of the specific heat capacity of the item (J/Kg/K). So to drop the temperature of 1kg of stuff from 21°C to 4°C your heat pump needs to work to remove however many Joules the specific heat capacity determines.
If on the other hand if your item is at 0°C then it’s going to heat up via heat transfer from the other items in the fridge. This means the internal temperature of the fridge will drop. But this means the heat pump will have to work less to maintain the internal temperature of 4°C. It’s not that the fridge attempts to heat the fridge up. The fridge simply works less because no fridge is perfectly insulated so it’s easy to let the temperature rise.
If you heat your home using a heat pump, it makes no difference. If you heat with gas, you will indeed use more electricity but less gas when refrigerating immediately.
By bringing "the cold" from outdoors inside, you're going to need an energy source to heat it back up when your home is in heating-mode. Even if you put it inside a small island of cold inside your home.
After writing (and deleting) a long response, I finally get your point.
You are trying to heat your home, so putting something outside to chill, is to waste heat, but putting it in the fridge would be like recycling that heat from the fridge to your room which should alleviate your room's heater burden.
> Is that power usage more efficient than not running it and relying on another heat source?
I can't get whether to answer yes or no to that question, but the fridge's heatpump is more cost-efficient that most people's heat sources. That's the entire premise of the article.
> However this drops off as the outside temperature drops and you push up the heating demanded.
With Irish climate and modern heat pumps this should be a non-issue. Maybe in the colder areas a day or two in the average year. Newer heat pumps can maintain very good efficiency under 0°C.
> Newer heat pumps can maintain very good efficiency under 0°C
Well under 0℃, in fact. The Mitsubishi ones are still at 200% at -18℃ (0℉), down from 300% at 0℃ (32℉). They don't fall to 100% until around -26℃ (-15℉). Fujitsu is similar.
Their capacity also falls at lower temperatures going from 100% at -5℃ (23℉) to 76% at -25℃ (-13℉) so you might need to go with a bigger system in some areas.
Heatpumps are commonly used all over scandinavia. They work fine even with extreme temperatures. Temperatures stay well above 0 Kelvin. So there's still plenty of energy to pump around. Of course with extreme temperatures you need to produce more heat. Which simply means you need a bigger setup.
What’s the advantage of an air-to-water heat pump as opposed to an air-to-air system? Why are they used for new buildings, instead of a standard A/C indoor unit which can also offer cooling?
Water can carry heat around a building more efficiently (in power and space terms) than air.
In a heating dominated climate, this can make sense in a new building. (It’s also a good match temperature-wise to in-floor radiant heat.)
In a retrofit situation (such as my house), it also makes sense and is cheaper than running supply and return ducts everywhere.
It’s not as good a fit in mixed or cooling-dominated climates (though they can cool as well, but then you have to insulate the pipes much better to prevent condensation).
> Water can carry heat around a building more efficiently (in power and space terms) than air.
Heat is carried by the refrigerant though? It only gets "converted" to air in the room itself by the indoor unit.
I am talking about European-style systems where you have A/C units in every room, not the American-style with air ducts distributing air from a central unit in the utility room.
I didn't mean a formal standard - I checked the definitions and what I'm referring as is that US generally prefers central or "packaged" systems (single big unit in the utility room, air is piped from there into the living space through various ducts) where as Europe prefers "split" systems where you have units in each room with refrigerant pipes going back to the outdoor unit.
Most of the US uses split units for central air (split meaning the condenser and evaporator are in separate units).
What you’re calling a “split” is more precisely called a “ductless (mini-)split” as even an evaporator in the mechanical room and linesets carrying refrigerant to an outdoor condenser is still a (conventional) split setup.
Other posters are correct that water can transfer heat more efficiently than air, but they're missing or burying the lede:
The temperature is very stable once you dig down a couple of meters. Winter or summer, it's probably an even 10-20 C (depending on your specific location). The ground has tremendous thermal mass and can act as an enormous heat sink. Your little house-sized heat pump isn't going to vary the temperature very much. You can optimize your heat pump to the specific temp range and dump/draw as much heat as you like year round.
In our climate there is simply no need for AC as it never gets uncomfortably warm for more than a few days a year. Air to water is used to heat radiators and supply hot water in lieu of gas or oil fired heating. In other climates air to air is more popular and it can be less complex as you don’t need all that extra plumbing.
With new builds air to water makes sense as it’s no different to installing any type of central heating system.
As a retrofit option an air to air system would seem attractive as the installation is much simpler. Our homes tend to be smaller and there wouldn’t be any HVAC ducting so you would probably only have a since source of warm air with an air to air system.
> With new builds air to water makes sense as it’s no different to installing any type of central heating system.
But it's the same level of effort than installing indoor A/C units, so why not install those instead? Plus refrigerant pipes can potentially be thinner depending on the max "load" of that room.
In a heating-dominated climate, there may well be no air conditioning installed. In a hydronic-only heating building (underfloor and/or baseboard/radiators), there can be less work to run heating pipes only (much faster, cheaper, and more forgiving than running refrigerant lineset and managing the condensation drain line).
For heat-only, I find hydronic to be nearly ideal: low noise, no dust, and high comfort (no air movement/drafts).
Heating with air is less efficient in transporting heat with water. So you either need to move more air or heat it up to a higher temperature. The first one is obvious why it’s a bad idea, the second is a bad idea as at a certain point the dust in the air is burning up leaving a bad smell. So practically you can heat a house with air heating alone only when they are extremely well insulated or in a mild climate. The passivhaus-Standard in fact is defined by heating through air being enough.
There is also question what is the water in picture. Heat pump efficiency decreases when the temperature delta increases. As such it really does depend is the heating done via radiators or underfloor. As later can be used with significantly lower temperature. Where as specially during cold times radiators need rather hot water. In such cases air-to-air might actually be more efficient.
Not an expert, but the much higher heat capacity (and heat conductivity) of water compared to air is likely one reason. But also, when it’s really cold outside, an air to air heat pump is much less efficient. If you have access to liquid water, that is of course much warmer than outside air.
Seems odd not to encourage both as PV solar and a heat pump go pretty well together. Is it more of a question of legislative particulars vs technology?
It’s down to cost. The energy rating is subdivided into thirds. An A1 home would have both but an A2 or an A3 will have just one. As long as it’s any type of A rated it’s acceptable.
For a ne whole adding both wouldn’t increase the cost to the buyer - they are already willing to pay X for the house. It would increase the cost to the builder, who would then have less money to pay the land owner for the land, who had received a massive planning gain when the 50k field was given to build 100 houses and increased in value to 3m.
I dont see the problem, PV and heat pumps should be mandated.
I have made a successful offer on a house. When I had initially walked through with realtor, I looked at the furnace and thought something was amiss. Then during inspection, the inspector told me that it was a heat pump, and it's only about two years old. My first reaction was "on no - electric heat". But later I Googled and found a page that has a cost calculator.
It looks like it will be ~20% less to have a heat pump. Also natural gas prices are forecast to continue up and make the heat pump even more cost effective.
I still do wish there was gas service to the house. But I doubt that I want it enough to pay for the installation.
If the house has no gas connection at all then, depending on local regulations, they may have been able to insulate to a higher standard, and so you save even more money.
Because of combustion you need extra ventilation designed in.
That and the connection cost make it an easy choice for newly built homes.
The house was built in 1975. There's about 3 inches of fiberglass batting in attic. One of the first things I'll do after closing is to blow in 12+" of insulation.
If you can pay for an alternative I’d strongly consider it. Blown insulation makes a mess of the attic. Makes it really hard to work up there if you need to get access, potentially blocks your soffits and decreases airflow, and makes it more difficult and dangerous to walk without risking falling through the drywall.
Drove me bonkers that “over-the-range” microwaves are unavailable in europe. Probably because they assume everyone uses gas and would set them on fire, or that it’s impossible for them to vent fast enough.
Unless you're building some billionaires summer cottage it's just not economically justifiable to pay for all the labor required to deviate from the standard plus all the material. If you want "better" you just do more extravagant construction but you keep to the same minimums.
That said, there are plenty of people exceeding the minimums. You just don't know it because they are doing it themselves (or with a friend or two's help) on their own property and typically not pulling permits. <clutches pearls>
In the US at least, high efficiency home gas furnaces bring in their own combustion air from the outside so they don’t bring drafts into the house. They also don’t have flues throughly the roof. The exhaust gas is cool enough that it goes out wherever is convenient through a PVC pipe parallel to the intake pipes.
This is pretty common in commercial buildings, though not for the heat reclaim that you're describing. It's particularly useful when you have simultaneous heating and cooling loads that can effectively serve each other.
There are two issue in heating a home with a heat-pump:
- one is for new homes, well insulated that do not demand much energy and have a p.v. system, so they need ways to minimize all costs, one way is if space is not an issue, to heat large quantity of water and store them to grab heat at night. For instance if you need 40kWh to heat the home for a night having something able to push 1000l of water let's say from 20 to 60℃ quickly enough to run on winter Sun from p.v. means free heat for the night [1];
- one is for those with old homes, who simply need MUCH thermal energy. They do not have much choices, so they need powerful heat-pumps and in that case low temp heating it's not much an option, they need high temperature water.
This is interesting for another consideration: most "efficient" electrical devices are built to consume less overall, but their load profile is TERRIBLE for a p.v. inverter. Witch means that a modern tumbler with a heat-pump not only costs more and last less than a classic ones but if you have p.v. it means LESS self-consumption. Similarly for ovens who try "pushing the heat" instead of give large amount of energy: they tend to have pulse loads that are terrible for a p.v. inverter. That's a thing their OEMs must consider in the present and future models.
[1] if some are curious thermal kWh = 4.2 kJ/kg·℃ * (initial_temp-final_temp) * volume_in_liters * 1/3600 h/s witch means in the above example 4.2(60-20)1000*(1/3600) = 46.67kWh
If you have a hot water store its relatively cheap to dump excess electricity as heat when you have nothing better to do with it. Not as magically efficient as heat pumps but possibly still worth it overall abd there's already products that meet this need on the market.
I do that already, but just for home sanitary water (sorry, do not know the name in English, water for shower etc) with the secondary resistive heating of an "old" (not on sale anymore) Daikin/Rotex M2O EKHHP 300l v3 but I can't do the same for heating: too much water is needed.
Actually I'm looking to expand the system with just a set of insulated tanks (found some on sale 500l/~1kWh/day of dispersion at 60℃ inside, 5℃ outside) and a bigger external heat pump + wood stove (for emergency) to heat the water. It's just an idea because:
- nothing pre-built seems to exists, apparently nobody is interested enough in try this way to save energy bills;
- it not really cheap and DIY style there are many things who can break making the project more an expensive toy than an effective solution.
IF I found something that seems good enough next spring I plan to expand, but it's still a relevant and generally interested issue the fact that nearly nobody talk about the dichotomy between p.v.-powered device needs to maximize self-consumption vs non-p.v. powered homes needs to reduce the total consumed energy: with a p.v. system anything should be designed to run all together at full power as much as possible, so automation to power on and off things quickly and things made to march at very different speed depending on the available power. It's far better for instance in that sense a classic resistive boiler who heat water less efficiently than a heat-pump BUT with a constant load and perhaps not a single resistance but few, to being able to "sum or reduce" the power depending on how much you can get from Sun. While if you do not have a p.v. it's far better to save as much energy as possible...
Some patterns might be common, like running appliance at a dynamic point in time, one depending on the Sun, the other depending on current grid load (and so price). But many others are different. A stupid example my washing machine, with it's eco-mode actually consume less kWh, but consume MORE from the grid because it have spike loads my p.v. inverter can't satisfy quickly enough from p.v. so they goes on the grid. On contrary running an "expensive" high temp washing program my self-consumption is normally 99.99999%
Surely, so far most homes do NOT have p.v. so the biggest market for any appliance is the one who do not count p.v. but is not really expensive counting it. Also it's absolutely not expensive ad ModBUS controls on anything who consume more than 1kW. It does not really change the price. It's absurd not offer such option in most appliance with a significant overprice (let's say 40€ for something that to the OEM cost just 1€).
> nobody talk about the dichotomy between p.v.-powered device needs to maximize self-consumption
I think there are two reasons. First, it's easy to use the grid as a sink, and add in local batteries if you're still concerned. Like here in the US, solar companies size people's PV systems based on their yearly consumption, totally ignoring what time of day consumption takes place, peaks, etc. We're basically coasting on the "net metering" mindset, for better and for worse.
Second, control solutions and energy storage solutions are generally quite bespoke (custom). I agree about the need for load management and device communication in general, but we're still (unfortunately) at the point of DIY solutions rather than some standardized communication. Which is probably a good thing, because the whole "smart" cloud crap that companies leap at is dead end technology anyway.
In the context of a northern climate with significant heating load, I don't think resistive heating ever makes sense, unless you somehow have access to free solar panels and free land. The tradeoff is going to be the maintenance burden of a heat pump versus how little heat you need, and if you're talking about storage then you seemingly need a bunch of heat.
I've been thinking about this problem due to wanting to go solar (with a utility that won't net meter) and also wanting to have a back up generator (but not wanting to get some oversized 12kW monstrosity to power a handful of things in an outage, just in case they happen to all turn on at once). My eventual solution will probably be something like a relatively large capacity battery inverter (eg SMA Sunny Island) tied to a relatively small amount of storage batteries. I'll schedule some loads (eg dehumidifer) to operate only during the day. If I get to the point where I'm significantly overproducing electricity, then I will think about increasing the battery storage.
The issue of consider the grid as a kind of battery is that IF you are paid for the energy you inject you are paid FAR LESS than the energy you grab with a so big delta that's far less than the "efficiency loss" of a battery...
When I've made my actual p.v. (here, France, we are allowed to build p.v. systems as generic citizens because before connect any system you need a certification from a third party body) I choose 5kWp because I thought it's enough. Now I understand that to really maximize my self-consumption I need MUCH more peak power because I need to been able to run on p.v. anything at once as much as possible because sunny hours are not that long. It's the same for the actual heating (water-water heat pump) I have a small reservoir because the system is designed to run when I need heat. It should instead be designed to run full power but really MUCH in few hours per day etc. Now, I'm a sysadmin not a p.v. technician not working for anyone in the industry so I find curios that I personally realize that and no one who damn work for perhaps a decades in the industry do not realize the same...
About resistive heating: yes it's far from being interesting but it is for a thing: it's extremely cheap and run in any external temp condition. air-water heat pumps do not, water-water (geo or from hot water reservoirs) heat pumps are still dependent on the "external side" temp. A small batch of resistence run by relais piloted via a cheap GPIO board in sequence following the maximum p.v. output possible it's a cheap way to maximize self-consumption. A heat pump can't vary much the compressor absorption witch means that if you need a big one to heat quickly a large mass of water you also need to power it. If you have few smaller you might fire up depending on the available power but it's hyper-costly... IMO having a big heat-pump for when the Sun shine well, a small one for when you can't run the big and you are on-grid/battery and resistive for the rest is the cheapest solution to use at best any kWh you can produce, no proof for that, just an idea, but so far that's the result of my limited experience...
> big delta that's far less than the "efficiency loss" of a battery
I agree with you, I'm just trying to explain why I think there hasn't been much emphasis on optimizing usage with regards to solar. For the most part people do not want to be their own electric company. They want to offset their bill and feel good about creating some solar production. Those that do want to be their own electric company are called "off grid", and end up going down a rabbit hole of custom engineering time that doesn't translate to the larger consumer market. It's closer to farming and that type of ingenuity rather than standard suburban living.
For resistive heating, you should also be able to continuously vary the power using a triac dimmer setup, although your solar inverter may be incompatible with this, or you may at least have to massively oversize it.
But heat pumps that use variable frequency drives do exist. They're commonly called "inverters", at least in US marketing, and should allow you to vary the power the heat pump consumes. Maximizing self-consumption isn't as important as maximizing the efficiency of that consumption. If a heat pump has a COP of 3, you're better off with a single 1kW heat pump than a resistive array that can sink 1, 2, or 3kW. Add in some storage batteries that can handle the cycling of the heat pump and you can dither its power consumption in time rather than worrying about instantaneous usage.
You said above that you've got a wood stove for backup. That's the way I'm leaning for now because heating with solar, heat pump, and battery storage in my climate seems impractical. If you're already doing water for heat storage, I'd recommend looking into setting up the wood stove so that it can heat the storage water, such that a single burn could perhaps give you enough boost for a few days.
> Those that do want to be their own electric company are called "off grid"
That's also my point, perhaps not clear in my poor English and quick writing: I do not want to be totally off-grid simply because it's crazy in costs terms for a marginal outcome BUT I want to be "off-grid capable for a potentially long time" witch is again the better "cost optimization" IMO, I mean the sole reason to have a lithium storage is protect themselves from blackouts. Even with skyrocketed energy prices batteries still not pay back at all. So the cheapest individual options are:
- just grid-connected p.v., you can lower the bill around 50% and the whole setup pay back at actual grid rate in a not so big number of years 5-10 maximum from a country to another. There is no protection against blackouts [1]
- AC-coupled or hybrid inverters with a battery, smaller enough to nearly pay back mixing the blackout backups protection + the little maximization of self-consumption during the day and the little authorized discharge (10-15% DOD) per day
Now just an year ago for most people in the western world protection against blackouts was simply too costly and essentially not needed. Blackouts war VERY rare and VERY short if any in an whole year, in few years. Nowadays for various reasons they start to be, at least they loom as an issue how seems getting bigger and bigger. Now running on a backup generator never pay back and have MANY issues, while a not so big battery, recharged by a small generator in few hours (when noise is not an issue etc) offer an expensive anti-blackout protection that probably do not pay back entirely but at least a bit and as for the resistive heating I call it "the best compromise" we can get now.
Yes, I got an wood stove (two actually, one potentially hydro even if I never made the plumbing and not even knowing what I really need to add precisely) and I have woods, and a bit of bush on my own, but that's meant for pleasure (seeing the flames sometimes in the evening) and real damn emergency usage. On a regular basis it's not much comfortable to use them, I do not have even enough wood for an entire whole winter... Something I can buy that can work automatically most of the time, enough to pay back a bit is far more welcomed...
My reasoning is that I already have p.v. and a small storage (8kWh) as a backup protection for freezers/fridges/VMC/computer/... It's expensive but lower my bill and it already protect me well, even if that happen only three times for few hours and a bit more for just few/less then a minute. It might help to lower the opex of a future EV since I WFH and so I tend to be at home during most days of the week the best I can do to maximize the ROI is using as much energy as I can, of course for something useful, not just to waist it... For instance for AcS I find better when I can (most of the year) heat it with it's built-in resistence instead of the heat-pump because it make the equipment last far longer and I can't use anyway the producible energy. If I decide in the end to expand the hot water storage also for heating well... Calculation are a bit complex and unfortunately that seems not a popular choice so even technicians I can find do not help much... Surely I'll integrate the wood stove, of course, it should be relatively easy and cheap and potentially really useful, but for the rest I do not know... I found very few "big enough" air-water heat-pumps not so expensive, but can't really know how well they can run in winter despite they formal claims.
[1] very few inverters/microinverters declare to been able to produce AC from p.v. without the grid or a battery BUT they can't sustain essentially any peak load, witch means you need special equipment that mount/lower their power consumption slowly and can survive a sudden energy drop if just a cloud pass by.
I notice the title has been changed. I think some people have misunderstood the original title, which was talking about a new category of industrial heat pump, since the site is Norwegian and assumes audience familiarity with 'standard' heat pumps.
Most of the conversation here is about standard heat pumps so the new title suits the conversation better, just thought it worth noting.
A bit of back story. When we built our home in 2003, we had plumbing for central heating put in with the idea that we would get a boiler, a lot of kerosene and get heating.
Sadly, but the time the home was finished, kerosene started to reach unreasonable levels which continues to this day.
Never had any boiler or even the radiators put in.
Over the past year or so , I found how people are using heatpumps to heat the water at 40-55°C, that water can be used to warm the house.
Tried to talk to some installers including the one who set up the plumbing, they are not convinced.
One said " the life of a heat pump is like 10 years. If you buy one, you will use it only for 10 seasons and the cost of that is quite a lot so the math does not check out.
To note, we don't have at whole house heating right now.
Tried to find YouTube but there isn't a lot of material on using heat pumps with central heating.
There are units which exchange heat with water, but typically they won't reach more than 40-45 C°, maybe 50, I doubt 55, so radiators heating won't work, you need fan-coils or - better - under floor heating.
Additionally (it depends) usually pipes used in traditional radiator heating system are smaller in section (when compared to those used in fan-coil heating/refreshing) so your existing pipes may be too small to allow the system to work efficiently.
Personally I am not impressed by them, if not in direct small (split) systems, the exchange to water seems like losing a lot of energy.
But the good thing is that they allow, in reverse, to cool the house in the warm months (though not comparable to a traditional A/C system).
The 10 years duration sounds like what you can expect (to be compared to a traditional burner that would cost less than half a heat pump and is more in the 20+ years duration).
There is also the issue that (at least in my experience) they are "slow" when compared to a gas/kerosene/oil burner, so you need to keep the house somewhat heated at all times as it takes more time to raise temperature[1].
[1] there is a lot of debate around whether it is more efficient (with traditional fuel burners) to switch heating off when you are not in the house (potentially letting the temperature go down to - say - 8-10 C°) and boost to the wanted temperature when you are in or keep at all times the house warm (at - say - 13-15 C°) and only increase the temperature to 18-20 C° when you are in
>There are units which exchange heat with water, but typically they won't reach more than 40-45 C°, maybe 50, I doubt 55, so radiators
That's what two heating "experts" told me in Spring 2021 when my gas furnace for central heating needed to be replaced and I asked them wether it would be possible to just replace it with an electric heat pump. "Impossible", they said, your house is not insulated strongly enough and you don't have floor heating, so the outgoing temp will not suffice".
It's not true. There are many heat pumps on the market now, and have been since 2020, which manage to deliver 55°C without problem, amongst them, self-contained "monobloc" devices[1] - a box mounted at the outside of the house, which only needs cables and two pipes for connecting to the central heating circulation. With COP values of 3-4 depending on outside temp and outgoing heating water temp. Look at your actual outgoing temp settings (or "heating curve") on the gas furnace. If you never need >55°C, or only need such a temperature on three extremely cold days each year, then a heat pump might be a good idea. Except you can't buy them right now, at least in parts of Europe, for reasons that need not be repeated here.
Sure, everything is possible, in theory, in practice it has to be seen specifically.
As said typically heat pumps work around 45-50 °, those that can reach higher temperature do exist, but are not common.
There is a rather nice paper (by Caleffi which produces mostly valves) that is a good intro to the conversion from burner boilers to heat pumps or other lower temperature heating systems:
what if we use, as you said, FCUs instead of a traditional radiator?
i understand other commenters are talking about individual air conditioning but that increases the electrical load exponentially because you have multiple units running at the same time... think of the poor wires.
has anyone been crazy enough to preheat the heatpump from solar ? would that even work?
As said, very likely the pipes you have (dimensioned for radiators) are too small for fan-coils.
There is not much issue with several units, the problem was with electric motors starting (old motors can have something like 5 times normal current peaks when starting) modern motors all have electronics that smooth them down.
I’d expect to get 15-20 years from a well-installed air-source heat pump. That’s not as long as an old, atmospheric boiler, but isn’t that much shorter than a modern modcon boiler in terms of what I’d expect.
Even if you got only 10 seasons, I think it would pencil out in most climates/electric prices, provided it can make all your heating load. (It was too questionable for my house, so I’ve had to pass for now, but will be plumbing the system to allow an easy addition of air-to-water to the primary loop.) Given that you’re 18 years without central heat, I’d expect you could get away with just a heat pump.
> I found how people are using heatpumps to heat the water at 40-55°C, that water can be used to warm the house.
This would only work for heating though and would have a significant latency (you have lots of thermal inertia in the system). Why not go with standard reversible A/C units which not only would also provide cooling capability but process the air locally so you don't have to wait for pipes/radiators to warm up before actually getting heat?
My research lead me to exactly the same conclusion. Heat pumps cost the earth if you call them heat pumps, but once you call them an inverter split A/C they magically cost an order of magnitude less (even though it's the exact same tech).
You do get slightly different tech when aimed at air-to-air and air-to-water needs, and different target temps and there's newer generations of the same tech that rivals ground source heat pumps.
So its not just a rip off, though there's probably a fair bit of that too as demand has risen recently.
There is a big push in Europe to replace gas central heating boilers with heat pumps, from before there were any problems with the supply of gas, I think the information available on them will improve quite quickly.
My brother has installed one for his house but I have not done yet.
Heatpumps at least in Austria are the preferred heating method for like 10 years if you build new or renovate.
They just work and it’s interesting to see that they are the new sh*t in the US.
That's right. My sister's family built their house 11 years ago in Germany, and they have a heat pump too. I think it's pretty standard for new residential builds.
40 to 55C is good for underfloor heating. Which in most cases unfortunately is way too costly to install, in an existing structure as you'd need to rip out all your floors and the ground beneath it, to allow for 8 cm of tubing in a cement structure.
The focus today is also on insulation ie preventing heat loss.
That means making houses less draughty.
But draughty houses are also healthy houses.
More fresh air and less mould.
I think it would be better if people accepted that in Winter
it's going to be colder indoors so wear thermal underwear etc.
Its called heat recovery ventillation, its the cheapest and most cost efficient improvement you can make to your life, house and energy bill.
You will have fresh air, control humidity and use 95% of the heat in your house air to heat incoming air from outside. It solves problems with mould and humidty. You can seal your house from the elments
A 'box' that does everything costs just 1 grand, just install ducting and you are done.
Making houses less draughty is just one point (convective heat transfer) another point is making walls conduct heat less to reduce conductive heat transfer.
Uninsulated houses often has higher risk to mold because of cold walls. Warmer air has a higher capacity to carry water as humidity. When it hits cold walls the air cools down and the water condensates leading to mold.
Drafty houses are not healthy houses: timber needs to be able to dry out to stay rot-and mold-free, but draftiness is associated with weakened immune systems and therefore poorer health. The draftiness rule only holds for older houses constructed before insulation, where the draftiness is needed to counteract the cool, stone/brick basement collecting moisture. A modern house design for insulation should be tight and mechanically ventilated, both for the maintenance of the structure and for human health.
It is possible to considerably improve the heat insulation of a building while still allowing turnover of fresh air. We don't specifically want to throw away the heat, we just want to change the air, and you can arrange to do that. The laws of thermodynamics forbid us from arranging to keep all the hotter molecules and lose the cool ones, but they allow us to insist on a roughly fair swap, hot air going out gets cooler, cold air coming in gets warmer.
This will be more expensive than just sealing everything up and hoping, but that's the sort of reason why you want somebody figuring out how to do it properly and only subsidising work that we know insulates homes without destroying ventilation so that they're horrible to live in. Modern homes here have much better heat insulation than when I was a kid, yet there isn't the damp problem I saw in cheaply retro-fitted rental places where I lived.
Do heat pumps still have a high enough efficiency at temperatures of over 150 degrees to justify the investment? I suppose the theoretical efficiency is still around 300% but I'm not sure how close heat pumps can get to the theoretical limits.
Page 79 has a bit of info on COP (efficiency) vs LLT (leaving liquid temp).
With intelligent management of LLT, your install will spend a lot of the year at 120°F or lower, where the efficiency is fairly high. If you end up with 2-3 days of COP under 2.0, that’s not catastrophic if you spend 40-50x as much of the season at COP of 3.5+.
You can probably find the outdoor temperature histogram for your area and figure out what your overall heating profile looks like.
But, if you need 150°F water a lot, AWHPs are probably not a good fit.
Note that the article talks about a different design of heat pump, compared with the common home and industrial HVAC units, for use in industry at that higher temp.
Especially valuable when you have some waste heat from another process.
Probably a good fit for existing district heating systems too.
No, the temperatures are in Celsius. From the white paper linked from the main article: "This paper makes a distinction between low temperature (<200°C) and high temperature (>200°C) process heat". https://www.sintef.no/globalassets/sintef-energi/industrial-...
Your original guess is right. I checked the original Norwegian text. It says 150 grader (degrees), and that surely means Celsius when used unqualified in Norwegian. So we’re talking high pressure superheated water here, for industrial purposes.
One of the demo projects listed in the linked white paper is aiming for >50% of theoretical efficiency in that temperature range
> LowCapex and FUSE (TNO): Demonstration of heat pump technology on an industrial scale (2 MW), producing process steam at temperatures between 120°C to 150°C from waste heat at 60°C to 90°C with efficiencies above 50 % of the theoretical maximum.
Elsewhere in the white paper:
> Comparing these alternatives, it has been shown that high temperature heat pumps, with COPs as low as 2, are competitive in levelized cost of heat with biomass boilers and natural-gas based boilers under consideration of a CO2 tax of 50 €/tonne.
they should. in general, the main time they drop significantly below theoretical efficiency is when the cold end gets iced up which wouldn't be a problem here.
In my country, I can't install a groundwater heat pump until summer 2023. That's almost a year. Many installation companies do not even take new customers any more.
It feels like modern air source tech is displacing ground/water source to some degree, I'm not sure exactly when ground source makes sense but it feels like the crossover point has been moving in air sources direction.
Might be worth looking into as the easier install is of course the key benefit.
Market penetration for home heat pumps here in Japan is very high, I’ve never seen an apartment that doesn’t have one in the last several years. As an American I was pretty surprised that the heating mode on my AC’s worked! https://heatpumpingtechnologies.org/market-report-japan/
Yes. But it depends a bit on the climate where you live. What you're looking for is an air-to-air heat pump. Basically it replaces the outside unit of your traditional air conditioner. But it can heat or cool.
If they only have a gas furnace, then they may not have an outside unit currently. Piping a refrigerant line and signalling from where the furnace is to a suitable location for the outside unit may be easy or hard depending on their home.
Of course, if they have a furnace and an air conditioner, it's a lot easier to change to a heat pump and that's it (or more likely, a heat pump and just in case resistive heating)
Just did this myself, but I augmented our gas furnace, instead of replacing it. The two technologies can work in tandem, if it gets too cold for the heat pump to work efficiently.
You do need more room for the heat exchanger.
But you can also get “mini split” units which are basically single room units.
Heat pumps are air conditioning systems. They work on the refrigeration cycle.
Rural homes in the US tend not to have connections to natural gas utilities. If winter isn’t severe enough to justify a storage tank, the home typically has an HVAC heat pump/AC unit, and really high electric bills for a month or two.
Heat pumps have gotten better, but they’re never a first choice for heating for good reasons.
Like most “emissions saving” initiatives the crux of it is where the electricity comes from.
Burning something for heat is always more effective, cheaper, and produces fewer emissions compared to an electric heater. Heat pumps need to power a compressor, while there’s some phase change and pressure hacks to move the heat around, systematically it’s trading electricity for heat.
If you’re getting electric heat from coal fired steam that’s always worse than burning the coal locally to heat something, and this is true for all emission-producing power sources.
The trick is that heat pumps are using energy to move heat. Let's make an example calculation:
When heating your house to burn coal, you release 1 Joule when burning the coal. It's a small plant, so it is not very efficient. You probably get 0.85 J of heating out of it.
If we instead burn coal in a large-scale modern power plant, we release the same 1 Joule, but capture 0.95 J of it in electricity. Let's say we lose 10% transporting it to your home, leaving 0.855 J remaining. Now, we use that energy to move heat from outside into our home, at an efficiency of about 300% - so for every joule we consume, we move 3 joules of energy. This means our house is heated with 2.565 J. But the energy the heat pump consumes doesn't disappear - it becomes heat too. So your house gets a total of 3.42 J hotter!
So 1 J of coal gets you either 0.85 J of heat by burning it directly, or 3.42 J of heat by burning it in a power plant and using a heat pump. And of course don't forget that for climate reasons it is trivial to replace that power plant with a solar farm or wind turbine.
The worst-case scenario for a heat pump is that it is exactly as efficient as burning stuff directly. But in virtually all cases, it is way better.
Pretty good assessment, except I think your figure for heat efficiency of power generation is way off. I would expect to convert around 30-40% of the heat energy to electricity.
That seems unlikely to me, both based on sources[1][2], and the thermodynamics of the Carnot equation. A Carnot cycle heat engine (which is most efficient possible AIUI) has a maximum efficiency of 1 - Tc/Th. Given a Tc of 300K (STP-ish), achieving an efficiency of 0.95 would require a Th of 6000K, well above the melting point of steel (only around 1800K).
The heat pump is only moving the heat. Burning coal doesn't move heat, it makes heat by destroying coal. Because the heat pump isn't making the heat it is able to move the same amount of heat from somewhere else (say, the outside air) into your home, using less energy than you'd need to make that heat inside your home.
Because you can't destroy heat (thermodynamics) for refrigerators we have no choice, we must use heat pumps. But once you get good at this technology, it's just better regardless of whether you want to move the heat away (Air conditioning, refrigerator) or towards you (heating a home).
This is how heat pumps claim seriously > 100% efficiency in many cases, they're comparing the efficiency of moving heat against making it.
It's important for people to know that at least when it comes to heating, "100% efficiency" is actually the worst possible efficiency. That's just thermodynamics. You can only get better than that.
No, you can get much worse as well when considering heating in general.
Heating efficiency is a measure of useful heat, so while of course energy is conserved in the universe, it is not 100% efficiency as measured, where we consider the consumed energy versus the successful heating of the home. Heat lost to the outside is inefficient.
With natural gas heating, efficiency used to be around 50% as the exhaust gases were quite hot. They just had passive chimney flues driven by natural convection. Improvements to recover more of that heat brought efficiency up to 80% and now approaching 95% in the most modern configurations that I've read about. They now require mechanical ventilation to remove the exhaust and also have condensate drains because the heat exchangers cool the gases so much.
Of course, something like a traditional wood fireplace is much worse than even those old gas furnaces, with a vast amount of energy going out the chimney.
With electrical heating, if you consider transmission losses you can see that the effective home heating is less than 100% of the generated power. The power lines and equipment warm the outside too.
Another benefit of the high COP heat pumps: in reducing the total power consumption at the home, it also brings a proportional reduction in those losses outside the home...
While this is true in some sort of physical sense, it's not really useful for home heating. The problem is that while burning stuff makes heat, that heat probably isn't where you wanted it, and you need to capture the heat and move it to where it's useful. Unfortunately burning stuff produces exhaust gases, and those too are hot, that is they contain some of the valuable heat, but the gases themselves are dangerous and unwanted.
Modern boilers achieve about 94% efficiency. That is, if we make 1MJ of heat energy by setting stuff on fire, the boiler transfers 940 kJ of heat energy into hot water. The remaining 60 kJ is warm exhaust. You've probably seen the exhaust from people's homes if you live somewhere with such boilers.
Heat pumps produce several times the heat as electricity put in. Even with a typical 40%-50% efficiency for a gas power plant you end up with more than 100% efficiency with a heat pump. If the power plant rest heat is used for instance for district heating you reach efficiency of around 90%. Add the efficiency of heat pumps on top and you end up with something very good.
What? No, this is incredibly short-sighted. It overlooks the fact that much grid energy is renewable already and will become more so in the future. Go with electric sources for cooking and heating (home and water), then let the grid handle being renewable.
Heat pumps are amazing technology and moving heat, vs generating it, is incredibly efficient and clean.
Heat pumps transfer heat from the outside, they aren’t generating it so it’s entirely likely that they would result in fewer net emissions than burning coal directly. And the calculus just keeps getting better for grids that incorporate more natural gas and renewables.
>Burning something for heat is always more effective, cheaper, and produces fewer emissions compared to an electric heater...
>If you’re getting electric heat from coal fired steam that’s always worse than burning the coal locally to heat something, and this is true for all emission-producing power sources.
Apparently you can actually save natural gas with electric heat and a heat pump.
Typical heatpump COP in Northwestern Europe sits at about 4, that means for 1 kWh of electricity your moving 4 kWh heat into your home. Electrical resistive heating sits at 1:1 by definition, and methods like wood, gas or oil, combustive methods, usually with modern installations at 80-95% efficiency. Further south heatpump COP improves; the rule of thumb is a smaller delta T the better.
Moving heat is always more efficient than creating heat. It's elementary physics.
Airconditioners, or air-to-air heatpumps, are cheap heaters for the same reason (any units sold in the last 10 years can move heat bidirectionally). Here in NW Europe by cooling bill is barely noticeable (it's no desert clime after all, although the last decade seems like it's getting there!). You don't need to set it to 18C; I really only cool when the attic gets over 28C while I work there (home office), down to 24-26, which is a few weeks a year. In winter, it heats the room at ~400% efficiency compared to the typical ~80 for gas heating.
> Typical heatpump COP in Northwestern Europe sits at about 4
:) yeah, when its really quite warm outside, but not quite warm enough that you dont need heating.
as soon as you even get down to 5C outside, you are not getting a COP of 4. Many vendors may tell you that, but well... :) some people were also sold bridges :)
A lot of people in my environment are in fact getting sCOP of 4. Bit better in fact: close to 5 in the group that also installed floor heating everywhere.
Note that COP around freezing is almost always the worst due to frequent defrosting, so yes, COP is worse at -5 most likely. You can replace COP with sCOP in earlier replies of mine.
What is true is that most people, including installers, don't know how to tune them very well, or forget to combine them with low temp radiators/ floor heating. Too high a T_out also occurs frequently.
In the Netherlands, heatpumps have been standard issue in new construction for a decade now, and 4 is about the average. It's very much not imaginary, but hard to believe for people from areas used to wood and oil burning ;)
i would question whether that is in fact happening. MAYBE scop, for the recent winters where it has not been cold, but unless you have a vastly overdimensioned setup for what is done now then, you'll be screwed if a real winter happens again
Overdimensioned: that can be a cause for low COP, and not always a surefire solution. But yes, properly dimensioning to your particular situation is more important than with other heating methods, agree. The best point I think is to target not the coldest winter you'd ever expect, because that means suboptimal runtime the rest of the year. Better is to target optimal runtime for most of the year, and accept horrible performance for a few days every 5 years or so.
Modern heatpumps work perfectly fine down to -20C or so, which covers nearly all of Europe.
If your winters are around 0C, it really pays to get units with better defrost management. You can use power output ratings; cheaper brands might have a third less output at 0deg, while others barely dip. In colder countries the cheaper units are funnily enough a great option, because once it's cold enough to continuously flow, you don't have to defrost at that often anymore.
they might work at -20C, but you cannot get ANYWHERE near the output out of them as you can when its hotter.
Several of my family members have heatpumps, myself included, and I can tell you that the COP reduces significantly as soon as we hit just 0C outside. my panasonic has a supposed SCOP of 5.1(or 5.2, cant recall), when it hits 0C here, its down to COP of ~2.5 at my best estimates.
when it hits -10, the COP is at best 2. I know this because I think around 1300W into it, and it is not able to heat my house more than a 2.5kW resistive heater.
this is their 3 year old flagship "nordic heat pump" that they will market as the sole heating solution for houses twice the size of mine, yet can barely do mine when it hits -5-10C :)
edit:
im not saying heatpumps are bad, they are great, but I dont think they are a great ONLY solution for places that are below 0C for more than tiny peak times.
when its 5-10C outside, and you want 22C inside, they are really amazing
Like I said, around 0 you're gonna get the worst performance, as outside temp goes down most models will see they COP actually increase (compared to ~0 C). Of course, delta-T is still important, so it helps hugely if you can have your water temp at 30 C (and still radiate effectively). It takes a carefully planned systems to reach that though (i.e. active ventilation on your radiators, or floor heating), so many will need to get water out at 40 C or even higher, which is going to bring you down from sCOP 4. At -20 COP is going to be 2-2.5. But, for many Europeans, that's not a frequent event. Even so, 200% efficiency is better than <100%.
I think many don't put much effort in the radiator side of things. E.g. here gas heating is usually ran at 60-70 degrees, while for that sCOP of 4+ it should be 30-35 C. Roughly, you're going to need a factor 4 more radiating surface. People don't always install that, and then run their heat pump at 50 C and get a COP of 2. Well, no shit :)
So, you gotta take a reasonable low point, understand how hot your circuit temp is going to be (the formula for radiators is pretty much the same over radiator brands from those I've used, floor heating idem), account for buffer losses (with floor heating, you can cut out your buffer and gain 0.5 COP just like that), and, if you have an outdoor temp of ~0 C for much of the year, look for a model that comes with a good defrosting strategy and keeps an acceptable efficiency around that temp. sCOP 4 is for the Netherlands, which has mild winters thanks to the Gulf Stream. However, family is in Poland, and there heat pumps are now also being installed everywhere (where below -20 C is expected for weeks each winter) and while you're right that this means an sCOP reduction, it can still be near 3 if you configure the rest of the loop right. And 250-300% efficiency is going to beat resistive heatings 100% or combustive methods each and every time.
2.5 kW sounds severely underdimensioned for a house at -20 C though. That would not cut it for my smallish house in NL, I've calculated ~5 kW at -15 C needed (and don't forget, make sure your radiators can emit this at the T_out!). Typically people would install a 7-10 kW unit for my sort of house.
> Like I said, around 0 you're gonna get the worst performance, as outside temp goes down most models will see they COP actually increase (compared to ~0 C)
This simply makes no sense, and is not to be found in ANY datasheets from any of the big manufacturers. How do you propose this will work? a given volume of air, say 1 cubic meter, has a certain amount of heat at 0C, if you take it down to -5C or -10C, that amount of heat is reduced. The heatpump can only put so much air over the heatsink, and thus the absolute amount of heat visible to the heatpump reduces as temperature goes down.
> 2.5 kW sounds severely underdimensioned for a house at -20 C though
well yeah, I have of course not installed such a heatpump (with a max draw of ~1500W in plus degrees) as my only heat source, im just trying to convey the output capabilities
It makes total sense, if you understand what a defrost cycle is. In the LG sheet I have in front of me its quite clearly reflected in the effective power output: a dip around zero.
replying here as could not reply deeper in thread...
Well maybe you ought to enlighten mitsubishi and panasonic, because they do not appear to have wrapped their minds around this yet. Looking at chinese manufacturers, neither have they.
The argument is that for regions that do not spend much time below 15 degrees Fahrenheit, they tend to be cheaper to run because they can pump more heat than electricity they use, effectively becoming 300% efficient instead of 95% efficient for say an gas heater.
As the temperature differential between the desired temperature and the outside temperature increases however, the efficiency does drop and what you say is true, but for most of the populated world, this is not the situation.
Heat pumps can be efficient enough to overcome the losses from coal -> electricity. So it's possible to use a heat pump to heat a space more efficiently than burning that same coal directly in the space.
I don’t like having to shut off my furnace and manually manage windows. But I also don’t want automatic windows. I just want it to be like, “you’re asking for 21C and we can get there by pumping in outside air rather than using an AC to transfer heat from the inside air to the outside air.”