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Re-using the heat in bathwater in Britain

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Re: Re-using the heat in bathwater in Britain

#171

Post by smileysteve »

SnaggyJoker wrote: post #70
georgeg23 wrote: post #28

Earlier quoted context omitted.

You could place a plastic mat on top to limit evaporation.

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…

Interesting thought on graywater. It really does seem easy enough for shower/washer/non-kitchen sinks to drain to toilets.

Re: Re-using the heat in bathwater in Britain

#172

Post by [deleted] »

bemmu wrote: post #166

In Japan at our place we always do this. After the last person has used the bath water, we let it sit there overnight, and then use the water for the first wash cycles of the washing machine. The less efficient part of this story is that everyone showers before entering, and that does go down the drain.

[deleted]

Re: Re-using the heat in bathwater in Britain

#173

Post by SECProto »

godelski wrote: post #159
SECProto wrote: post #119

Earlier quoted context omitted.

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 hom…

I'm very confused at the lash back you're getting. Have you all never seen the pipes freeze? Or worse: burst? They wouldn't do that if they didn't swing in temperature. I'm not convinced of SEC's 2-3x estimated increase but the claim that water temperature delivered to your taps vary in temperature is an objective fact. Of course different areas have different infrastructure and can be more resistant to freezing and…

> I'm not convinced of SEC's 2-3x estimated increase

It's a simple calculation, but very location specific. In my particular case, if the water heater is set to 50C, and tap water is 22C in Summer, it has to impart a ΔT of 28C. If your tap water is 4C in winter, the ΔT is 46C. Not quite double, but close to it. If your water heater is in a poorly conditioned space, then it would lose considerably more heat to the surrounding space when outside temperatures are -15C than when outside temps are 35C. All told, hot water energy usage for my particular situation is between 2x and 3x. Other situations would vary, but still significant.

Re: Re-using the heat in bathwater in Britain

#174

Post by zarzavat »

refurb wrote: post #145
alkonaut wrote: post #126

Earlier quoted context omitted.

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.

Indeed. Having living in SE Asia where you can drink the tap water, it’s rough getting a glass of water from the tap and it’s 25C. There is no “cold” tap, just warm and hot taps.

> SE Asia where you can drink the tap water

A very verbose way of saying Singapore.

Re: Re-using the heat in bathwater in Britain

#175

Post by fomine3 »

maherbeg wrote: post #11

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.

Newer heat pump bath system in Japan supports to reclaim the bath water heat into heat pump bath system's tank. Though it won't reclaim from shower. https://www.mitsubishielectric.co.jp/home/ecocute/function/h... https://kaden.watch.impress.co.jp/docs/news/523254.html

Re: Re-using the heat in bathwater in Britain

#176

Post by zarzavat »

smileysteve wrote: post #171
SnaggyJoker wrote: post #70

Earlier quoted context omitted.

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…

Interesting thought on graywater. It really does seem easy enough for shower/washer/non-kitchen sinks to drain to toilets.

The problem is how to keep such a system clean, as then there will be a bunch of foreign gunk floating around in your cistern.

Re: Re-using the heat in bathwater in Britain

#177

Post by fomine3 »

ArmandGrillet wrote: post #53

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.

Isn't bathing the worst heating method for energy usage perspective? I don't think it's heating method but cleaning.

Re: Re-using the heat in bathwater in Britain

#178

Post by Loocid »

mvhvv wrote: post #115
Gigachad wrote: post #102

Earlier quoted context omitted.

Why not feed that heat back in to the power plant to squeeze more electricity from it?

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.

They exist but you're right that you can't just use the waste heat directly. You have to pump in some extra heat to make it worthwhile.

They are called co-generation power plants. The one I used to work at took the waste heat from gas turbines, added more heat with HRSGs (heat recovery steam generators) and fed it into a steam turbine. It adds a significant amount of efficiency.

Re: Re-using the heat in bathwater in Britain

#179

Post by fomine3 »

Tade0 wrote: post #45
stefan_ wrote: post #5

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.

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.

It heavily depends how they use bath, and how cold. In Japan, 25-40% (vary depending on research) of energy at home is used for heating water because people prefer bathing. Heating water is expensive.

Re: Re-using the heat in bathwater in Britain

#180

Post by SnaggyJoker »

zarzavat wrote: post #176
smileysteve wrote: post #171

Earlier quoted context omitted.

Interesting thought on graywater. It really does seem easy enough for shower/washer/non-kitchen sinks to drain to toilets.

The problem is how to keep such a system clean, as then there will be a bunch of foreign gunk floating around in your cistern.

Yeah and bacteria would build up in the reserve tank.

An inline filter of some sort could be used for particles but that would require maintenance.

There would also be soap scum build up and hair conditioner products would gunk up the works I'm sure.

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