[HN Gopher] Suddenly everyone wants 'super-hot' heat pumps
___________________________________________________________________
Suddenly everyone wants 'super-hot' heat pumps
Author : ZeroGravitas
Score : 135 points
Date : 2022-09-04 12:02 UTC (10 hours ago)
(HTM) web link (norwegianscitechnews.com)
(TXT) w3m dump (norwegianscitechnews.com)
| jwie wrote:
| 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.
| ctur wrote:
| 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.
|
| Do not burn fissile fuels in your home.
| sokoloff wrote:
| > Do not burn _fissile_ fuels in your home.
|
| Completely agree; that would be incredibly dangerous and
| polluting (and probably illegal)!
| tialaramex wrote:
| Buffy had it right, "Fire bad, tree pretty".
| tialaramex wrote:
| You seem to have only half understood?
|
| 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.
| phyzome wrote:
| 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.
| saltcured wrote:
| 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.
| tialaramex wrote:
| 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.
| legulere wrote:
| 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.
| throwaway894345 wrote:
| 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.
| KVFinn wrote:
| >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.
|
| https://youtu.be/MFEHFsO-XSI
| altcognito wrote:
| 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.
|
| https://www.youtube.com/watch?v=7J52mDjZzto
|
| (edit: I think you're going to get a lot of links to the overly
| in depth series tech connections, but I'm leaving it here all
| the same)
| boloust wrote:
| 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.
| [deleted]
| brnt wrote:
| 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.
|
| Move heat. Don't create it.
| crote wrote:
| 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.
| aftbit wrote:
| 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.
| donny2018 wrote:
| Is there a heat pump technology that I can just swap my gas
| furnace to? With no additional insulation requirements and no
| other strings attached?
| falcolas wrote:
| 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.
| SuperQue wrote:
| 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.
|
| For example:
| https://www.trane.com/residential/en/products/heat-pumps/
| toast0 wrote:
| 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)
| sharpercoder wrote:
| 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.
| ZeroGravitas wrote:
| 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.
| belter wrote:
| 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.
|
| "Heating and Cooling With a Heat Pump" -
| https://www.nrcan.gc.ca/energy-efficiency/energy-star-canada...
|
| "Heat pump" - https://en.wikipedia.org/wiki/Heat_pump
| oezi wrote:
| I haven't understood why they are called heat pumps now when it
| is essentially the same as a AC.
| toast0 wrote:
| 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.
| ChuckNorris89 wrote:
| 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.
| whoooooo123 wrote:
| Is there any meaningful difference between a heat pump and an
| air conditioner, other than the direction the heat is pumped
| in?
|
| Wouldn't it be more accurate to say that an air conditioner
| is a type of heat pump?
| jasode wrote:
| _> 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.
| otikik wrote:
| 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.
| contravariant wrote:
| 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.
| ChrisMarshallNY wrote:
| Thanks for the links! The Canadian one is great!
| ornornor wrote:
| Technology connections on YT has a fantastic video on heat
| pumps, how they work, their energy efficiency... highly
| recommended
| magic_hamster wrote:
| 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.
| codewench wrote:
| 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.
|
| [0] https://youtu.be/Ll6-eGDpimU?t=2099
| styfle wrote:
| 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.
| ornornor wrote:
| 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?
| whatisthiseven wrote:
| Honestly I dislike TC because he rambles and is too
| verbose. I don't know why he has recommended so much here.
| ornornor wrote:
| Because he digs deep in topics that I find interesting. I
| don't find the rambling annoying, personally.
| tialaramex wrote:
| "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.
| ornornor wrote:
| 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.
| tialaramex wrote:
| 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 PS40
| 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 PS0.10 per 100g. I could put that
| in a dishwasher but...
|
| If I want dishwasher salt, that's PS1 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.
| sokoloff wrote:
| That video: https://youtu.be/7J52mDjZzto
| ssizn wrote:
| 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
| ricardobayes wrote:
| The key as to why is probably lies with the price of gas vs
| electricity. Countries where natural gas is cheap, you won't
| find heatpumps.
| LatteLazy wrote:
| 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)
| foepys wrote:
| Everybody already has a small heat pump at home. It's the part
| that makes the refrigerator cold.
| RandomWorker wrote:
| 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.
| knolan wrote:
| 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.
| Scoundreller wrote:
| > 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.
| yaantc wrote:
| 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.
| [deleted]
| madacol wrote:
| I don't understand how that conclusion follows from the
| quote.
|
| I still think "putting something warm outside to chill in
| winter before refrigerating" cost _less_ electricity than
| refrigerating immediately
| Scoundreller wrote:
| By outside, I mean outdoors.
|
| 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.
|
| On a net basis, you've made your home colder.
| ianschmitz wrote:
| Because what you said doesn't make sense
| knolan wrote:
| You're going to have to explain your reasoning to me there.
|
| If your fridge is at 4degC and you put something in there at
| 21degC 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 21degC to 4degC 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 0degC 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 4degC. 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.
| Scoundreller wrote:
| Because I'm trying to heat my home in winter.
|
| Outside = outside_outside = outdoors.
|
| Not, uhhh, inside outside like the kitchen counter.
| ThunderSizzle wrote:
| Running the refrigerator requires power. Is that power usage
| more efficient than not running it and relying on another
| heat source?
| Scoundreller wrote:
| > 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.
| Nextgrid wrote:
| 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?
| smileysteve wrote:
| Water is much more efficient at thermal transfer than air.
| All of those little brittle fins on the outside, less
| compressor run time.
|
| It's also better in cold weather for heating as a water mass
| rarely gets below freezing.
|
| The issues are a water source and corrosion.
| quintushoratius wrote:
| 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.
| legulere wrote:
| 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.
| sokoloff wrote:
| 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).
| Nextgrid wrote:
| > 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.
| WastingMyTime89 wrote:
| > European-style systems where you have A/C units in
| every room
|
| Which European countries are you talking about? There is
| no European standard regarding A/C or heating.
| Nextgrid wrote:
| 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.
| knolan wrote:
| 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.
| crote wrote:
| I feel like installing a heat pump which cannot cool is a
| mistake at this point.
|
| Heat waves are already getting more intense and more
| frequent. While AC was a luxury a decade or two ago, it is
| rapidly becoming a necessity.
|
| It is absolutely bizarre seeing houses designed like -20C
| winters are still a common thing, while completely ignoring
| summer heat.
| Nextgrid wrote:
| > 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.
| falcolas wrote:
| Because it can also heat a house at the same energy
| efficiency, that is, better than electrical resistance or
| gas heating.
| sokoloff wrote:
| 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).
| Ekaros wrote:
| 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.
| hanche wrote:
| 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.
| kevincox wrote:
| > 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
| 0degC.
| tzs wrote:
| > Newer heat pumps can maintain very good efficiency under
| 0degC
|
| 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.
| dv_dt wrote:
| 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?
| knolan wrote:
| 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.
| intrasight wrote:
| 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.
|
| https://www.columbiagaspa.com/services/add-or-convert-to-gas...
|
| 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.
| ZeroGravitas wrote:
| 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.
| intrasight wrote:
| 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.
| pmlnr wrote:
| Blow what? Don't do foam. It'll massacre the timber. If you
| want something else, look at hempcrete, wool, foam glass
| aggregate.
| jws wrote:
| 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.
| nkurz wrote:
| > depending on local regulations, they may have been able to
| insulate to a higher standard
|
| Are you implying that some places have _maximum_ amounts of
| insulation that are allowed for new construction? This seems
| backwards.
| ZeroGravitas wrote:
| No, but they'll insist on minimum ventilation if you burn
| stuff, which usually involves letting heated/cooled air out
| with the toxins.
| Scoundreller wrote:
| 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.
| xeromal wrote:
| If they're too airtight, it's a safety issue if you have a
| gas system.
| ceejayoz wrote:
| Builders and homeowners tend to functionally enforce the
| minimum _as_ the maximum.
| 2Gkashmiri wrote:
| I am in the market for a heat pump.
|
| 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 40-55degC, 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.
| ricardobayes wrote:
| 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.
| jaclaz wrote:
| There are units which exchange heat with water, but typically
| they won't reach more than 40-45 Cdeg, 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 Cdeg) and boost to the
| wanted temperature when you are in or keep at all times the
| house warm (at - say - 13-15 Cdeg) and only increase the
| temperature to 18-20 Cdeg when you are in
| te0006 wrote:
| >There are units which exchange heat with water, but
| typically they won't reach more than 40-45 Cdeg, 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 55degC 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 >55degC, 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.
|
| [1] e.g. this one, which even delivers 60degC:
| https://www.daikin.eu/en_us/product-group/air-to-water-
| heat-...
| 2Gkashmiri wrote:
| 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?
| jaclaz wrote:
| 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.
|
| You mean:
|
| https://en.wikipedia.org/wiki/Solar-assisted_heat_pump
| 2Gkashmiri wrote:
| not these... they aren't available in india :-(
|
| i mean air to water source heat pump that would get
| inputs from a standalone solar water heater.....
|
| solar water heater>heat pump>??? profit
|
| https://www.racold.com/heat-pump-water-heaters/domestic
|
| 150Litre one basic model costs INR 122,000 or US $ 1452.
|
| https://www.racold.com/solar-water-heaters/alpha-pro the
| basic 100 Litre one costs inr 24000 or us$ 285. this is
| retail prices while government subsidy is like in 10,000
| or US$119.
|
| you can see the idea,
| ZeroGravitas wrote:
| Mixergy does a water tank that can accept input from
| multiple heat sources including solar thermal and solar
| PV and heat pumps.
|
| Not sure how widely available it is though.
|
| https://www.mixergy.co.uk/products/solar-tank/
| rjsw wrote:
| 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.
| BonoboIO wrote:
| 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.
| kleiba wrote:
| 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.
| mardifoufs wrote:
| They aren't at all new in the US though? It just depends on
| the location, and they are very common in some areas
| sokoloff wrote:
| I like HeatGeek and once you start watching them, you'll get
| plenty of other recommendations.
|
| Here's a reasonable get started video of his:
| https://youtu.be/D8pvXDk_KAA
|
| 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.
| Nextgrid wrote:
| > I found how people are using heatpumps to heat the water at
| 40-55degC, 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?
| ricardobayes wrote:
| 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).
| ZeroGravitas wrote:
| 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.
| ctur wrote:
| 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.
|
| https://youtu.be/7J52mDjZzto
| bcjordan wrote:
| Came here to post this :D
|
| 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.
|
| Other fun ones:
|
| - a defense of the simple drip coffee maker
| https://youtu.be/Sp9H0MO-qS8
|
| - why do the turn signals not sync up when you're at a stop
| light? https://youtu.be/2z5A-COlDPk
|
| - how humidifiers work and ehy the simple swamp cooler style
| are pretty ideal https://youtu.be/oHeehYYgl28
|
| - 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
|
| - why do light switches click? https://youtu.be/jrMiqEkSk48
| pottertheotter wrote:
| 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.
| BoiledCabbage wrote:
| Did you change brands or types when you switched to powder?
| pottertheotter wrote:
| 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).
| cromka wrote:
| 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?
| pottertheotter wrote:
| I used Cascade Complete powder and Cascade Platinum
| packs.
| lupire wrote:
| When you used powder, did you add detergent to the prewash
| cycle?
|
| TC did make an apology video after the first detergent
| video.
| pottertheotter wrote:
| I usually put some in the prewash area.
| kortex wrote:
| 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.
| pottertheotter wrote:
| 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.
| smhg wrote:
| 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.
| oezi wrote:
| > - why dishwasher detergent packs are stupid (use
| powder/liquid)
|
| ? I thought that powder and liquid for dishwashers have come
| out worse on any consumer reports test (at least here in
| Germany).
| WastingMyTime89 wrote:
| 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.
| Scoundreller wrote:
| 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.
| oezi wrote:
| A good dishwasher (based on testing) will never need some
| manual tinkering like this.
| blacksmith_tb wrote:
| 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?
| zo1 wrote:
| 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.
| Scoundreller wrote:
| Not on this continent. But obviously the advice can be
| ignored if your dishwasher isn't connected to hot water.
|
| The reason for your setup is probably 240V electricity
| that is affordable enough to resort to resistive heating.
| oezi wrote:
| Packs should be put in the dispenser so they don't act
| during prewash.
| mschild wrote:
| 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.
| lupire wrote:
| Fine tuning powder per wash sounds like overoptimization.
| Just useing powder instead of tabs will save most of the
| money.
| Scoundreller wrote:
| But I _save_ time by pouring in less when less is needed.
| oezi wrote:
| Prepackaged tabs with self-disolving packaging is
| actually the cheapest if you assign a non-zero amount of
| money to your own time.
| kortex wrote:
| 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.
| sokoloff wrote:
| I looked on Amazon at Cascade powder ($0.22/oz in large
| packages) and the same name tablets ($0.30/tablet in
| large packages).
|
| A load with powder is typically 0.75 oz. ($0.165/load) or
| about 55% the cost, not 10-25% the cost.
|
| Being able to dump in extra for pre-wash is an advantage
| to powder for sure.
| [deleted]
| stormdennis wrote:
| 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.
| ClumsyPilot wrote:
| 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.
| Jill_the_Pill wrote:
| Do you know: is this tech useful for hot water
| radiator/boiler systems or is it just for air?
| pottertheotter wrote:
| In Europe where most homes only have radiant
| heating/cooling, new homes have a separate fresh air
| system, which would include an ERV.
| ctroein89 wrote:
| 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.
| tialaramex wrote:
| 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.
| legulere wrote:
| 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.
| contravariant wrote:
| 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.
| adgjlsfhk1 wrote:
| 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.
| sokoloff wrote:
| 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 120degF 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 150degF water a lot, AWHPs are probably not a
| good fit.
| contravariant wrote:
| Oh were the temperatures mentioned in Fahrenheit? Then that
| makes things a bit easier, I thought they needed 150degC.
| nkurz wrote:
| No, the temperatures are in Celsius. From the white paper
| linked from the main article: "This paper makes a
| distinction between low temperature (<200degC) and high
| temperature (>200degC) process heat".
| https://www.sintef.no/globalassets/sintef-
| energi/industrial-...
| hanche wrote:
| 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.
| MobiusHorizons wrote:
| Another clue is that they call 150 deg 5 bar steam.
| sokoloff wrote:
| In that article (for industrial process heating), it could
| be in degC.
|
| For home heating, 150degC would be far too dangerous to
| circulate.
| ZeroGravitas wrote:
| 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.
| csours wrote:
| I completely missed the link to the whitepaper and thought it
| was just a really bad article.
|
| Does the pdf talk about which working fluids are used? Are
| there any details at all about implementation?
| icegreentea2 wrote:
| 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 120degC to 150degC from waste
| heat at 60degC to 90degC 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 EUR/tonne.
|
| So... definitely not slam dunk.
| Waterluvian wrote:
| 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."
| Dig1t wrote:
| You must have a well insulated house.. as soon as I turn off my
| AC or heater my house very quickly becomes the same temperature
| as outside..
| Waterluvian wrote:
| My house is also in a forest so the sun doesn't bake it. That
| might be part of it.
| ghaff wrote:
| 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.
| [deleted]
| dijonman2 wrote:
| 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.
| dagmx wrote:
| Isn't that effectively a heat recovery ventilation system?
|
| https://en.wikipedia.org/wiki/Heat_recovery_ventilation?wpro...
| elil17 wrote:
| That's called an air side economizer, they're very common in
| commercial buildings but residential units are also available.
| JohnJamesRambo wrote:
| 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.
| amluto wrote:
| 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.
| JohnJamesRambo wrote:
| Some googling of experts shows it can be quite a concern.
|
| https://www.eng-tips.com/viewthread.cfm?qid=188008
| Scoundreller wrote:
| 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.
| amluto wrote:
| 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.
| Scoundreller wrote:
| 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".
|
| Let alone being able to do dehumidification only.
| amluto wrote:
| 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.
| Scoundreller wrote:
| Would still be more comfortable and efficient if could
| aim for what I'd be equally happy with: 23C + humid or
| 26C + dry
| pkulak wrote:
| That's just because the temperature swings wildly. Water
| isn't going in and out of the air.
| [deleted]
| mherdeg wrote:
| 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"
| Jill_the_Pill wrote:
| 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?
| sokoloff wrote:
| 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.
| masklinn wrote:
| > 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.
| bilsbie wrote:
| You should look into a whole house fan.
| jotato wrote:
| Can confirm. They are awesome
| bilsbie wrote:
| I have heard to avoid them in areas with high humidity for
| mold reasons. But otherwise I don't see why it couldn't
| save you a ton on cooling.
| tolmasky wrote:
| 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.
|
| 1. https://www.iqair.com/us/whole-house-air-purifiers
| piceas wrote:
| I think systems like this make sense.
|
| I'm not yet convinced that they are worth 3k more than a pico
| and a fan, at least as a retrofit.
| pkulak wrote:
| 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.
| WithinReason wrote:
| I was looking for such a minified heat pump as well, no
| luck.
| Scoundreller wrote:
| Or just, a windowshaker A/C unit that has a heat mode.
|
| (That's uglier, but surprisingly difficult to find).
| WithinReason wrote:
| Exactly, but no luck. Maybe there is a technical reason.
| Scoundreller wrote:
| 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.
| rapjr9 wrote:
| 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.)
| amluto wrote:
| 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.
| tolmasky wrote:
| 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.
|
| My main gripe with the Perfect 16 is that it doesn't do any
| of the multi gas stuff ( https://www.iqair.com/room-air-
| purifiers/gc-multigas ), and is more like running a
| HealthPro ( https://www.iqair.com/air-purifiers/healthpro-
| series ).
| amluto wrote:
| This is where less gold-plated products may be better!
| Look at page 6 here:
|
| https://leesheatingandcoolingservice.com/wp-
| content/uploads/...
|
| 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.
| amluto wrote:
| Huh, IQ Air does have specs and prices:
|
| https://www.iqair.com/us/whole-house-air-purifiers/buy
|
| 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.
| sd_mikey wrote:
| 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.
| smileysteve wrote:
| 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.
| fennecfoxen wrote:
| 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.)
| aequitas wrote:
| 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.
| speleding wrote:
| Or use a cheap zigbee or zwave power plug to switch the
| fan, then run the logic somewhere else. (I do this)
| Nextgrid wrote:
| Wi-Fi is easier to interface with using any computer, where
| as those other protocols require a dongle on the computer
| side.
| pkulak wrote:
| Sure, but once you have 20 or 30 of those things in your
| walls, congesting up your network, you'll wish you went
| with something that runs at 900 mhz.
| benj111 wrote:
| >20 or 30.
|
| 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...
| gruez wrote:
| 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.
| bombcar wrote:
| There are machines that do just that. They're descended from
| commercial units, and you have to match humidity, but they can
| be done.
|
| It's just not been worth the cost, usually.
| seniorsassycat wrote:
| Would it be feasible to create a 'heat bus' to pump heat between
| a network of devices in a house?
|
| E.g in winter allow the fridge to dump heat into the kitchen, in
| the summer pipe it outside, or into the bathroom floors, or into
| the water heater.
|
| Install one outdoor unit in the sun or attic where it's hot and
| another in the cooler shade...
| grigri907 wrote:
| 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.
| kkfx wrote:
| 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
| ZeroGravitas wrote:
| 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.
| kkfx wrote:
| 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 40EUR for something that to the OEM
| cost just 1EUR).
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