[HN Gopher] Re-using the heat in bathwater in Britain
___________________________________________________________________
Re-using the heat in bathwater in Britain
Author : colinprince
Score : 93 points
Date : 2022-10-30 17:48 UTC (5 hours ago)
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(TXT) w3m dump (dynomight.net)
| joezydeco wrote:
| These diagrams imply that the incoming water to the heater is
| heated by drain water from the bath.
|
| But if you're filling a bathtub there's no warm water going down
| the drain. So the exchanger is useless here. And then when you're
| done and drain the tub the exchanger gets hot but the heater
| isn't filling any more.
|
| This device only really works in a shower situation, it seems.
| bombcar wrote:
| The only "practical" installation I've seen (besides ones in
| massive multiplayer showers like you'd see at a college or
| YMCA) was for a massive house with a huge shower designed for
| 30+ minute showers.
|
| And at that point you probably can "save the environment" more
| by not building a 10k sq ft mansion. But what do I know?
| tuatoru wrote:
| Someone (Luu?) coined, a while back, the phrase "cocktail party
| idea".
|
| This is exactly that. Something that sounds like a great idea to
| people standing around chatting, but in reality is full of fail.
| stefan_ wrote:
| As the article points out, only some 9% of domestic energy goes
| towards heating water for showers and baths. Instead of trying to
| force yourself to do cold showers, you could save much more just
| turning down the thermostat.
| Tade0 wrote:
| Exactly. Space heating is the most energy-intensive an
| expensive item on the list of things you can save on in a
| detached house - especially that you only really need the heat
| to be where you are.
| sweettea wrote:
| Not discussed: hot water in houses increases humidity. In modern
| well sealed houses, that can result in unfortunate mold growth.
| vasco wrote:
| From the article:
|
| > Extra moisture in the air might cause problems with things
| like mold. Use your judgment. It's probably fine as long as
| things don't stay damp all the time. For many, extra humidity
| in the air would be welcome. (Maybe you can stop using that
| ultrasonic humidifier.)
| yjftsjthsd-h wrote:
| I've always experienced extremely low humidity in winter
| months, so I would think the net effect might be a reasonable
| positive if this saves me needing to run a humidifier. Am I
| missing some detail? Or is that just unusual?
| bombcar wrote:
| Moisture is the #1 destroyer of buildings in its various
| forms.
|
| https://www.buildingscience.com/bookstore/books/moisture-
| con...
|
| Moisture control and mitigation is a very important part of
| building to last, and building to minimize maintenance and
| energy usage (simplistic "insulate everything and seal all
| air leaks" can result in a doomed structure).
| jibbit wrote:
| You're in the uk?
| yjftsjthsd-h wrote:
| No, but I was given to understand that winter => cold =>
| dry air was driven by the basic physical properties, so I
| would be very curious if it was different there. Is it
| different in the UK, and if so, why?
| mrob wrote:
| The UK climate has moderate temperatures and a lot of
| rain. Excess humidity is a common problem here, and
| excessive dryness is rare.
| jibbit wrote:
| someone else can explain better than me, but.. humidity
| is lower when it's cold but relative humidity is higher.
| Being outside in the uk when it's cold is often like
| being inside a cloud, with 100% relative humidity levels.
| Combine this with the old, badly insulated, difficult to
| heat housing stock, and you can guarantee that there is
| one part of the house (a north facing wall, say) that is
| at or dangerously close to the dew point for some part of
| the day/night. You wouldn't want to leave a steaming bath
| for longer than necessary.
| infpeace wrote:
| It tends to often be humid here, even in winter.
|
| Right now, it's 81% humidity. Our laundry has been taking
| two days to air dry.
| stefan_ wrote:
| Cold air can hold much less water (hence why it's
| _relative humidity_ ). This is good if you take in cold
| air and heat it to 21degC or so because the air you end
| up with will have very low humidity, but if the outside
| is a drizzly 10degC and you are only heating to some
| 18degC, it can be a problem.
| bausgwi678 wrote:
| It depends massively on your climate and how air in your
| house is managed.
|
| If you live somewhere which is significantly colder outside
| than in (e.g. 0-5C out, 21C inside) heating outside air to
| comfortable temperatures will greatly decrease humidity.
| Couple this with a system which circulates air, or even
| exchanges inside&outside air and you will have incredibly low
| humidity inside.
|
| I live somewhere which often sees 10-15C @ 80% humidity over
| winter, and the only air circulation in my house is from
| opening doors/windows. 70% internal humidity @21C is
| incredibly common. It takes a bit of moisture management to
| keep it below 60%.
| newaccount74 wrote:
| Ventilation with heat recovery sounds like it could work in
| those conditions, but just barely. 80% @ 15C would turn
| into 55% @ 21C.
| cameronh90 wrote:
| Unfortunately, very few homes in the UK have any air
| ducting. I'm looking at installing a MHRV system at the
| moment, but planning the ducts is a nightmare. Brick
| walls, lintels and structural joists everywhere with no
| headroom between floor and ceiling.
|
| We absolutely should be doing it in new builds though,
| and we're not.
| nsteel wrote:
| New build flats have some air ducting. At least, mine did
| in two rooms (it wasn't for AC). But maybe you meant new
| build houses.
| [deleted]
| hgomersall wrote:
| It's because the house builders don't do the job properly and
| install MVHR, which not only removes the excess humidity, but
| also recovers most of the energy of vaporisation.
| dmd wrote:
| Why do you say "not discussed"? That's point #4 in the article.
| nicd wrote:
| This reminds me of a "re-circulating shower" concept I was
| looking into recently. By filtering and re-using shower water, it
| saves both water and heating energy. There is a company in Sweden
| doing this: https://orbital-systems.com/.
|
| There's a bit of an ick factor, but with filtration, it seems
| this should be more hygienic than bathing? My family remains
| unconvinced though ;)
| tempestn wrote:
| Most people are fine with hot tubs aka spas, which are
| essentially this. (In fact most spa designs don't even filter
| all the water on each re-circulation, as there are returns both
| at the bottom and in the skimmer, and only the latter is
| filtered.) Re-circulating shower sounds like a great idea to
| me.
| wcoenen wrote:
| I tried this once on a cold winter day: I let the bath cool down
| to room temperature (which was <20C) before letting it drain,
| with the bathroom door open. The result was a lot of condensation
| on the windows in the surrounding rooms. I figured the high
| humidity was going to cause more damage than it saved money, so I
| scrapped the idea.
| shellfishgene wrote:
| If you really wanted to do this and remove the moisture problem
| you could probably cover your tub full off water with a plastic
| sheet to cool off.
| georgeg23 wrote:
| You could place a plastic mat on top to limit evaporation.
| SnaggyJoker wrote:
| You could also switch to a water conserving mist shower and
| reduce the amount of heated water used for the shower.
|
| You could also reclaim the water from the shower for use in
| the toilet by turning the supply to the toilet off and
| manually transferring it to the toilet tank.
|
| There are lots of things you could do to save resources but
| most things are not done and are not going to be done because
| it is inconvenient and takes time, and time is money.
|
| Edit: now that you have me thinking about this idea, it would
| be possible to have a container in the bathroom attached to a
| plug that has a hand pump and a tube going to the drain that
| could be used to reclaim and hold the water that could be
| higher than the toilet supply and the pressure from it could
| be used to have it self fill the toilet tank. The container
| could be highly conductive material like stainless steel and
| it could be relatively sealed to avoid humidity issues. This
| would of course be a vector for illness in some cases.
| TrueSlacker0 wrote:
| Combo that with toilet sinks and a lot of water would/could
| be saved per year/person.
| SnaggyJoker wrote:
| The same tank could be connected to the sink too, turning
| any toilet into a toilet sink.
| thinkingemote wrote:
| My smoke alarms go off.
| z3t4 wrote:
| It could also be that your windows are not insulated enough.
| For 20C and 40RH the windows need to be colder then 6C to get
| condensation.
| leoedin wrote:
| The relative humidity of a bathroom after a shower must be
| much higher than 40% - I would imagine getting towards 100%
| (hence room temperature mirrors steaming up). Where I live
| (UK) I don't think I've ever seen an indoor humidity as low
| as 40% - it's typically in the 60-70% range.
| bombcar wrote:
| Moisture has to go _somewhere_ even if you don 't see it
| visibly condensing on windows.
|
| Either it's being absorbed or you have something removing
| moisture from the system (venting, etc).
| comboy wrote:
| Simplest use case would just to have a container in the
| basement / garage through which the water flows, assuming you
| are heating it at least a little. You likely keep lower temp
| there so it is much more efficient. Although in practice drain
| from the shower or bath quickly connects with the one from the
| toilet so it's not that easy to implement.
|
| In your case efficiency is also slightly lower due to
| evaporation. If anybody has any idea how significant it is I'd
| love to learn. I was surprised one day in winter to find that
| my evaporative humidifier has temp below 10C on it (room temp
| 23C).
|
| I think ground heat pumps could have an exchanger around the
| main drain pipe which should work nicely both in winter and
| during summer.
| Anthony-G wrote:
| As a bather, I also tried this idea a couple of years ago. I
| thought condensation would be an issue but the house I live in
| seems to have low humidity. The bigger downside for me was
| having to expend more time and effort cleaning the sides of the
| bath.
|
| This summer, I tried taking cold showers as an alternative
| energy conservation measure. So far, this Autumn has been very
| mild in Ireland so I've been able to keep up the habit (I still
| treat myself to a bath once a week or so).
| hanoz wrote:
| It occurred to me to try this for the first time last week
| and the extra cleaning thing swung it for me too, which is a
| pity as there's a good 40 pence worth of heat in that water
| at current prices. Not sure the wife was going to be too
| pleased with my used bathwater hanging around all day anyway.
| Also, probably not a very good idea for anyone with young
| children in the house.
| skrause wrote:
| Living in Germany and getting both my heating and hot water
| from natural gas I regulary track my gas consumption throughout
| the different seasons. With 1-2 showers per day in the
| household my daily natural gas consumption in winter is about
| 20x higher than in summer, so compared to heating the house the
| energy in the hot water is a drop in the bucket.
| SECProto wrote:
| Note that a portion of that increase in gas consumption is
| still due to the hot water usage, even if the number and
| duration of showers stays the same - tap water varies in
| temperature through the year, getting colder in winter and
| warmer in summer. In my case, it varies between ~5 and ~22C.
| Germany has milder winter temperatures so likely not as much
| variation, but still a significant fraction of the
| temperature increase imparted by your water boiler.
| Additionally, if you have a hot water tank (as opposed to on
| demand), then the tank has to work harder to maintain
| temperature (assuming you maintain the indoor air temperature
| differently in winter than summer).
|
| All combined, that might account for a 2 to 3 fold increase,
| the rest of it would be caused by space heating.
| Retric wrote:
| Well water stays very consistent year round in most areas.
|
| Some municipal systems vary more depending on where they
| get it and how they store it. Water towers used to smooth
| out water demand for example can noticeably impact water
| temperatures.
| SECProto wrote:
| Temperature _at the well_ stays consistent, but it can
| vary at the tap. At a family member 's secondary
| property, tap water will vary from 2 deg in winter up to
| 15 in summer (because the line between the well and the
| house is only ~3-4 feet deep, and surface temperature
| changes a lot). If we were drawing more or less/line was
| different length/different depth, the variation would
| change.
|
| (I know all these values from homebrewing, where water
| temperature plays a big role in how long it takes to
| cool)
| Retric wrote:
| Very rarely used property you can get temperature swings
| underground next to these pipes. But in normal domestic
| or municipal settings the regular water through the pipes
| is going to equalize temperatures year round to within a
| fraction of a degree at 3-4 feet underground outside of
| extremely long runs.
|
| Also of note, ~25feet of one inch pipe holds 1 gallon of
| water. So there can be quite a bit of lag involved, but
| water is unlikely to spend that long in these pipes to
| change temperature. Thus the ground temperature would
| need to be extremely different to make a significant
| difference once the temperature equalized.
| alkonaut wrote:
| 22 degrees is the coldest tap water? That means you
| basically need ice cubes or fridge storage before you can
| drink it in the summer?
| SECProto wrote:
| Strangely enough, drinking water is served at
| temperatures up to 100C in certain preparations (eg tea)!
|
| Less tongue in cheek, yes, people will often chill their
| tap water in the summer before drinking. But it's
| perfectly drinkable at whatever temperature it comes out
| of the tap. The water supply in my locality comes from a
| surface reservoir, leading to the higher summer
| temperatures.
| alkonaut wrote:
| I just never reflected on the idea that cold tap water in
| summer is quite luxurious. I have that but I have no idea
| why tbh.
| michal8181 wrote:
| Same here (I live in Poland). 2 + 2 family with small kids.
| Hot water is 5% of my overall gas bills. Rest is heating.
| Someone1234 wrote:
| Although higher humidity should make it feel warmer given the
| same ambient temperature. So if you're increasing the
| temperature mildly using this method AND increasing humidity,
| it may compound one another positively.
|
| Although, it is a minor efficiency gain either way.
| cameronh90 wrote:
| I'm in the UK, extra humidity is the last thing I'd ever want
| in winter.
|
| At the moment, I've got two beefy dehumidifiers running and
| I'm still at between 70-85% humidity in each room. I don't
| have any damp or leaks, it's just that the outdoor humidity
| has been 80-90% for the last few weeks, so ventilation is
| futile. And because of the weather at the moment, we're
| drying clothes indoors.
| cannam wrote:
| I thought high humidity made it feel colder, when the
| temperature was relatively low?
|
| Hot damp air feels hotter than hot dry air, but I've had the
| idea that cold damp air feels colder than cold dry air. Is
| that a misconception?
| magneticnorth wrote:
| I agree with you. Water facilitates heat transfer, and the
| surface of skin is about 95f, so it seems that below that
| temperature, and assuming you aren't already sweating for
| the evaporative cooling effect, humid air should move heat
| out of your body more effectively than dry air.
| lucb1e wrote:
| But did it even do anything in the first place? Because if the
| temperature wasn't measurably raised, it's not even worth
| considering the 'how to deal with humidity' question that
| people are discussing.
| bitxbitxbitcoin wrote:
| This is so much more reasonable than that ...other... Modest
| Proposal.
| [deleted]
| yjftsjthsd-h wrote:
| The other one would have a bigger environmental impact;)
| jitl wrote:
| What other proposal?
| Anthony-G wrote:
| That would be _A Modest Proposal For preventing the Children
| of Poor People From being a Burthen to Their Parents or
| Country, and For making them Beneficial to the Publick_ by
| Jonathan Swift:
| https://en.wikipedia.org/wiki/A_Modest_Proposal
| [deleted]
| [deleted]
| convolvatron wrote:
| I reuse my bathwater to start a new load of laundry...that seems
| a lot simpler
| pshc wrote:
| How do you get the bath water to the laundry machine?
| convolvatron wrote:
| I do my laundry in the bathtub :-)
| throwaway894345 wrote:
| Not if you have a frontload washer. :)
| ars wrote:
| Along with the problem of getting the water into the machine,
| the soap from a bath would damage the machine.
|
| Front Loaders require low-sudsing soap, and you have to be
| very careful on the type of soap, because many types tend to
| precipitate onto the inside of the machine.
| VBprogrammer wrote:
| How does the plumbing work for that? I can't imagine it passing
| plumbing regulations in most countries. Even having a grey
| water system is tricky under most regulations (the reason for
| this is the slim chance someone could misconnect a potable
| system.
| ytdytvhxgydvhh wrote:
| I appreciate this attitude:
|
| > Should you do this?
|
| > I render no judgment!
|
| > But here's a thought: It's OK to use energy for convenience.
| This is true even in a time of crisis. After all, only a small
| fraction of the energy we use is necessary to stay alive. We
| could live dirty and shivering in dark rooms, eating oats and
| only moving around on foot. But no one does. So the question is
| how much energy you want to use for how much convenience.
|
| Too many articles or conversations about energy usage seem to
| take an attitude more like, "if you're not doing the thing we say
| is the solution then you're the problem".
| imoreno wrote:
| This seems like a lot of work to save PS0.13.
| kragen wrote:
| I've done this. It works surprisingly well, and (as Might points
| out) humidifies the house in a way that radiators and resistance
| heaters do not.
|
| The evaporating water does convert (to use the traditional terms)
| sensible heat into the latent heat of water vapor, and you might
| think that this heat should be discounted from the heat you're
| getting out. Sometimes it should, but not other times, because if
| the water vapor condenses again inside the house (for example,
| near the surface of the plaster in cold walls) it will release
| this heat again as sensible heat. In other cases, it's worse --
| I've had the displeasure of staying in a cold guest room where
| the blankets were all slightly damp from such condensation and so
| failed badly at keeping me warm.
|
| In that case, the water vapor had been produced not by
| evaporating standing water but by burning natural gas. Be
| careful.
| pmoriarty wrote:
| If you let dirty water fill up your tub while you shower that'll
| result in a dirty ring around your bathtub which you'll have to
| clean... with more water (and possibly chemicals)... it'll cost
| you extra time to clean as well.
|
| All together the total costs of the extra cleaning resulting from
| this may exceed the cost savings from letting the water heat your
| home.
| sixstringtheory wrote:
| In addition to things like heat exchangers or reducing the amount
| of time/water in a shower, is there any work being done around
| optimizing the amount of time a hot water heater keeps the water
| at high temp? I've thought about this for extended absences but
| this could also bring potential benefits if it just doesn't run
| for certain portions of the day or middle of the night.
| mvhvv wrote:
| I'm not sure if things are different outside Australia, but
| it's probably been 15-20 years since I've lived in a house with
| a hot-water storage tank. As far as I know most places seem to
| have instant/continuous systems that heat the water on demand
| as it passes through the line.
|
| Solar-heating definitely makes storage make more sense, but I
| don't know how the numbers actually work out on that one.
| bombcar wrote:
| People have done that (some recent post on HN was about using a
| RaspberryPi to do just that, including a "get hot enough to
| remove legionaries' disease").
|
| Likely for most people the tankless heaters would be a better
| option, or using in-floor water-based heating instead.
| Something like this:
| https://www.radiantcompany.com/system/opensystem/
| maherbeg wrote:
| I was actually looking at heat recuperation systems for bathrooms
| recently and stumbled upon https://ecodrain.com/en/ - if we
| hadn't already remodeled our bathrooms I'd have loved to have
| installed this.
|
| For now we make do with a heat pump water heater which is very
| efficient.
| twic wrote:
| There are numerous manufacturers of these things, eg:
|
| https://powerpipehr.co.uk/
|
| https://showersave.com/vertical-wwhrs/
|
| https://recoupwwhrs.co.uk/
|
| Ultimately they're just cleverly arranged copper pipes, so the
| barrier to entry for new manufacturers is low!
|
| I am keen to get one - my shower sits directly above a cupboard
| on the floor below, where it would be simplicity itself to fit.
|
| This article suggests the energy savings are not particularly
| big:
|
| https://www.thegreenage.co.uk/tech/waste-water-heat-recovery...
|
| ... but there are several comments reporting the opposite!
| ip26 wrote:
| It depends heavily on how much your house showers, what the
| water temperature is at the inlet to the house, and how ideal
| your plumbing is. The efficiency is highest with a vertical
| unit at least five feet in length, and that's really just
| down to your house's layout.
| afandian wrote:
| I wonder how different it would be to use an off the shelf heat
| exchanger, e.g. this one?
| https://www.ebay.co.uk/itm/263272702860
|
| You'd probably have to filter the shower water before sending
| it through, but beyond that I wonder how different the
| principle is. Maybe being easy to clean is a significant factor
| in drain showers.
| shellfishgene wrote:
| There may also be problems with sanitation rules, only a
| minimum of water should sit in the pipes, and then ideally
| hot our cold but not luke warm.
| afandian wrote:
| Got a link (or explanation) for that temperature
| stipulation?
| tempestn wrote:
| Temperature window for bacterial growth. Above about 120F
| harmful bacteria commonly found in water won't
| proliferate, but will survive. As you get hotter from
| there, they're killed off increasingly rapidly. Above 135
| or 140 or so they don't survive long. In cold water they
| won't die off but also won't multiply quickly. The
| dangerous range is in the middle.
| twic wrote:
| I think doing adequate filtration of the full waste water
| flow without losing most of the heat would be a challenge.
| And remember you're also sending soap suds down the pipe,
| which will pass the filter and leave deposits inside the
| exchanger.
|
| Also, if you're just using gravity to push the waste water
| through, what flow rate would you get on one of those units,
| and how many would you need to handle the full flow?
|
| The most persuasive waste water heat exchangers i've seen are
| based around the a large-diameter pipe, with conical sections
| connecting it to the input and output, where the waste water
| flows down the inner wall of the pipe in a thin layer, and
| the cold water flows up the outside. It's not as space-
| efficient as a conventional heat exchanger, but it avoids the
| problem of blockage.
|
| That would also be fairly easy to improvise, i think, given
| that you can buy copper pipe, or even buy copper foil and
| wrap it into a large, thin-walled cylinder.
| ArmandGrillet wrote:
| Tangentially related: has someone found something less energy
| intensive than taking a bath while bringing the same degree of
| warmth?
|
| I've been looking at heated blankets but they're all made of
| polyester which is not comfortable due to the moisture being
| trapped under the blanket. Heated seats in some cars are the
| closest sense of comfort I've found but that technology doesn't
| seem to exist for regular seats.
| bombcar wrote:
| Heh get a dry suit (like a wetsuit but sealed) and then fill it
| with hot water? Should only use a few gallons.
| ac29 wrote:
| Electric heating pads?
| luckylion wrote:
| Heated blankets never really did the trick for me either.
| Electric foot-warmers do. They're cheap, don't consume too much
| energy, and will get your feet nice and toasty in no time.
| twic wrote:
| I have an electric blanket. The way it works is that you put it
| underneath the sheet, on top of the mattress. Moisture getting
| trapped under it isn't really a concern, because i lie on top
| of it. From the sheet up, the bed works in the normal way.
|
| I turn it on for 30 - 60 minutes or so before getting into bed,
| to warm the bed up, and turn it off once i get in. I have tried
| leaving it on all night on the lowest setting, when it is very
| cold, but i wake up dehydrated.
| zubspace wrote:
| Maybe just one or two hot water bottles? [1] We use them in
| Winter to warm our feet in bed. But they are very versatile and
| can also be used to alleviate any kind of tension.
|
| I also use one while I code: I put it inside of a small
| (baby-)sleeping bag wrapped around my feet. Sounds weird, but
| it's so comfortable!
|
| [1] https://www.google.com/search?q=hot+water+bottle&tbm=isch
| gima wrote:
| Another trick is to put lots of dry rice grains into a sock,
| tie the sock and warm it up in a microwave. Just be careful,
| as the rice heats up Really fast in the microwave.
| sixstringtheory wrote:
| We use this trick on winter backcountry camping trips to good
| effect. After dinner, melt snow to a boil and fill up all our
| water bottles and bring them in the sleeping bag. Every
| little bit helps!
| ArmandGrillet wrote:
| Went for https://www.yuyubottle.eu/ after a bit of googling
| due to the cotton fabric + the strap, will test it this
| winter.
| GavinMcG wrote:
| https://solar.lowtechmagazine.com/2022/01/the-revenge-of-the...
| ericpauley wrote:
| A heated mattress cover has been a game changer for me. You can
| use your existing comfy blankets and it only takes a very small
| amount of heat to really make a difference. It definitely pays
| for itself in being able to reduce temperature set point at
| night.
| oliwarner wrote:
| Having read this, I'm strongly considering routing my bath and
| shower wastes through a poorly insulated hot water cylinder in
| reverse (new [warm] waste in at the top, old cold waste out the
| bottom). Hot water will float in there. Cold will be displaced
| first.
|
| It only has to hold the volume of "a shower" and we'd keep that
| energy within the envelope of the house, without added humidity
| or state-change heat loss.
|
| The only major downside is the "what happens when it clogs"
| question. To work normally, it would require the discharge to
| rise to the same height as the top inlet before falling to the
| drain, but there could be a secondary purge for pressure-flushing
| it once a month.
|
| Rarely does plumbing make so much sense to me. I suspect I'm
| overlooking something. Answers on a postcard.
| frankus wrote:
| Something like this could be interesting with active heat
| transfer, for example using it as the source side of a heat
| pump water heater. As long as the outgoing water remains above
| freezing, of course.
| jitl wrote:
| I read a lot about district heating systems yesterday after
| seeing an article on NYC's steam system on HN
| (https://news.ycombinator.com/item?id=33388473). District heating
| systems allow you to capture waste heat _at the power plant_
| (called co-generation), and use that to heat & cool (via cooling
| compressors) many, many buildings at once. The wikipedia article
| about it is very informative as well:
| https://en.wikipedia.org/wiki/District_heating.
|
| Usually district heating systems route heat into your building's
| pipes using a heat exchanger - so the network's fluid never
| actually intermingles with your building's fluid lines. These
| systems also use the same heat exchanger to return excess heat
| back to the network. District heating systems require a large
| initial investment, but over the long term are very efficient.
| Gigachad wrote:
| Why not feed that heat back in to the power plant to squeeze
| more electricity from it?
| mvhvv wrote:
| I'm no power-plant engineer, but vaguely remembering back to
| thermodynamics 101, in a perfect heat-engine efficiency is
| relative to the temperature delta.
|
| You can't just turn heat to electricity, so below a certain
| threshold it's only good for warming spaces.
| HPsquared wrote:
| The mirror image of this is combined heat and power (CHP). That
| is, instead of burning fuel to heat the home, use the fuel to
| power a generator of some sort, and using the electricity to
| power the home. The waste heat (most of the energy from the
| fuel ends up as waste heat) is then captured to heat the home
| It's basically free electricity, if you were already heating
| the home by means of combustion anyway (e.g. oil, natural gas,
| propane).
| nsteel wrote:
| The problem with district heat schemes in the UK (at least) is
| they are becoming mandatory for new large housing developments
| but are 100% unregulated every step of the way. The builders do
| the cheapest job possible because the efficiency targets
| they're supposed to hit are never measured or verified post
| install. And unlike the rest of domestic energy in the UK,
| pricing is totally unregulated. The residents can (and are)
| charged high rates because it's impossible for them to change
| supplier. Any potential savings are undone by these two things.
| The energy regulator has so far refused to do its job because
| they supposedly don't want to stifle growth in this new market.
|
| It is a good idea but it's been sabotaged by greed.
| sokoloff wrote:
| It seems sabotaged by incompetence on the part of regulators.
| You can't make something both 100% mandatory and unregulated
| and then go shocked-Pikachu when the monopoly grantee takes
| advantage.
| louison11 wrote:
| Where we live in Portugal humidity is a big problem, and we
| actually spend 1kW 24/7 running dehumidifier throughout the
| house. If we didn't, mold would grow and we would get severe
| allergies. So... this seems like a very bad idea even for the UK,
| considering it's very rainy there in the winter.
| frankus wrote:
| A house with plenty of air exchange (either mechanical or
| because of a leaky air barrier) in a cold climate will tend to
| suffer from too low of humidity (cold air enters, and as it
| gets heated to room temperature the relative humidity drops).
| pshc wrote:
| This is a thing in some newer construction, e.g. in Vancouver BC,
| the Southeast False Creek Neighbourhood Energy Utility recovers
| waste heat from a wastewater treatment system to supply heating
| energy and hot water to mixed-use buildings.
| lkramer wrote:
| In my experience, there a many lower hanging fruits in British
| houses to save energy than this. Uninsulated and draughty old
| houses seems to be the norm here (at least if you're renting).
|
| I'm surprised the government is not pursuing this more
| aggressively.
| mgaunard wrote:
| Even if you're buying, the most popular houses are ancient
| Victorian ones which, in spite of their charm, are very badly
| insulated.
|
| They're often listed and require fitted wooden windows, so it's
| not exactly easy to fix.
| twic wrote:
| Vanishingly few houses are actually listed. Some are in
| conservation areas, which have similar but less strict
| restrictions on what changes you can make. These are the
| areas in my borough - almost half the built-up area, but i
| would guess proportionally less of the homes, because they
| are lower-density old buildings:
|
| https://www.haringey.gov.uk/sites/haringeygovuk/files/haring.
| ..
|
| You can coax a London-wide map of conservation areas out of
| this, and see that most of the suburbs aren't covered by
| them:
|
| https://apps.london.gov.uk/planning/
|
| It probably is true that the most desirable houses are in
| those areas, but being in a conservation area helps preserve
| them and keep them desirable.
|
| Anyway, even within those conservation areas, there is plenty
| you can do to improve insulation. I had internal wall and
| ceiling insulation fitted, and replaced the window sashes
| with double-glazed ones.
| jupp0r wrote:
| "Extra moisture in the air might cause problems with things like
| mold. Use your judgment. It's probably fine as long as things
| don't stay damp all the time. For many, extra humidity in the air
| would be welcome."
|
| In climates like in the UK, this is a great way to create mold in
| your bathroom and adjacent rooms if your house is well insulated
| and does not have central ventilation.
| imhoguy wrote:
| Or simply take shorter showers, then this system wouldn't really
| benefit because before the drainage pipe warms up enough to
| transfer any heat to cold water, you will be done. Grey water
| tank systems with recuperation are already known tech, but it
| requires extra maintenance unfortunately.
| fifteenforty wrote:
| I've looked into installing a system like this in Australia. It
| only barely makes financial sense as part of a new build. Maybe
| in the colder UK climate it would make more, but surely not as a
| retrofit.
| tempestn wrote:
| Problem is you're not just adding heat, but humidity. Normally
| while having a shower you're going to run an exhaust fan in the
| bathroom. So if you want to conserve heat, the better approach is
| just to make the shower as short as possible.
| chihuahua wrote:
| That seems like a more realistic suggestion to me. If you want
| to take this further, switch to taking Navy showers: get wet,
| turn off shower, apply soap, turn on shower to rinse off.
| upsidesinclude wrote:
| Turning your thermostat down by one or two degrees per week and
| getting acclamation to cold is a better alternative. 5 degrees on
| the thermostat would be a far better measure than tub heat.
|
| Short showers, or 'sea showers', to conserve water and heating
| would likewise be a far better option than a 50 gallon bath.
| sixstringtheory wrote:
| And not just short showers, but managing the amount of time the
| water is actually running. Here's my strategy for an efficient
| shower:
|
| 1. turn on the water, get in, rinse down, soak a wash cloth
|
| 2. turn off water
|
| 3. lather hair with shampoo
|
| 4. lather wash cloth with soap and scrub body
|
| 5. turn on water and rinse down
|
| The majority of the time we're standing in the shower, we don't
| actually need the water to be running.
| pbhjpbhj wrote:
| It gets really cold without the shower water running. Our
| indoor temperature in the day is 16-18degC in Winter (UK).
| pbhjpbhj wrote:
| What's a "sea shower". Do you mean when you literally just
| spray water on yourself, then soap all over, then rinse off?
| twic wrote:
| https://en.wikipedia.org/wiki/Navy_shower
| erik_seaberg wrote:
| Tom Clancy loved to collect details like this. When Jonesy
| detected the Red October on sonar, in the book he was
| rewarded with a "Hollywood shower."
| brunick wrote:
| i did hear about some shower drains that reuse the heat like this
| one: https://www.youtube.com/watch?v=s5bJ61fCA2E
| yrgulation wrote:
| Energy poverty can be sorted out by better insulation and
| investment in cheaper and more sustainable sources such as
| nuclear, wind and solar. Instead of working around this issue
| with clever hacks this needs to be a national policy. I think all
| roofs should be mandated to have solar panels installed, as a
| start, and all new builds should have proper insulation.
| VBprogrammer wrote:
| I think a step further is required. I really like the idea of
| using solar panels as an integral part of the roofing
| structure. There are people in the UK doing this as integrated
| solar panels which use a plastic tray underneath. I think with
| some slight adaptions we could even do better.
| spockz wrote:
| We had a few of these projects in the Netherlands. It is
| nice, until it isn't. The solar panels are more vulnerable
| than tiles, they will degrade or need repairs/replacing. The
| mechanism for sealing it up will leak. The format of the
| panels and or the inverter was proprietary. Or the connection
| was and you couldn't retrofit another inverter. It wasn't a
| good experience.
| HPsquared wrote:
| If I was planning national energy infrastructure, I wouldn't
| plan on dividing the equipment into a million tiny pieces and
| installing it on roofs, of all places. It seems much simpler to
| manage a solar farm than 10,000 roofs.
| yrgulation wrote:
| Why not both tho? Energy issues arent limited to capture and
| storage, it involves distribution as well. Plus you want
| energy to be dirt cheap and accessible. So the more the
| better.
| est31 wrote:
| Solar farms are more economic to build than rooftop solar:
| https://www.nrel.gov/news/program/2021/documenting-a-
| decade-...
|
| For individuals the calculation might be different as
| rooftop solar makes you less dependent on price trends you
| have no influence over, but as a society, utility solar is
| less expensive.
| hgomersall wrote:
| Waste water heat recovery should be mandated. I'm not sure if
| you included that in your "clever hacks", but it's definitely
| fantastic value for effort.
| postultimate wrote:
| I've been doing this, except I have a bath. It finally dawned on
| me that heating water and leaving it to cool was exactly the way
| the house is normally heated, so it was costing me nothing to
| bath as long as I liked. I live there now.
| IanCal wrote:
| A good way of reusing the heat from a shower is to have a heat
| exchanger to the cold pipe coming in. This has the advantage of
| also meshing nearly perfectly when you want to heat water.
| kragen wrote:
| The article mentions this about halfway down, with a diagram.
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