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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

#221

Post by _nalply »

You shouldn't let warm water stay in a place with air contact. First it makes air humid and the affected rooms prone to mold, and second evaporation takes energy away, and while condensation might give the energy back you will have wet conditions. It's not very sanitary: warm and wet conditions for some time tend to encourage unwanted life.

I armchair thought about a scheme: collect the bath and shower water in a tank in the cellar and use a heat exchanger. However the tank will turn disgusting very quickly. Perhaps a better solution is using a large, long pipe with a flat floor with little inclination, such that warm water does not stay for a long time but flows slowly. Cool the floor of the pipe with a heat exchanger. Perhaps have a contraption to regularly have the pipe brushed from inside and flushed with cold water. Instead of a heat exchanger, use cold water, but this has the problem that fresh cold water needs to flow at the same time as the used warm water.

It is worthwhile?

Re: Re-using the heat in bathwater in Britain

#222

Post by _nalply »

Retric wrote: post #114
SECProto wrote: post #63

Earlier quoted context omitted.

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 inc…

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.

Once in Singapore when I was invited by a friend in a highrise flat I wanted to have a cold shower. However the cold water was still very warm and I didn't feel refreshed. I think the tropical sun warmed up the water in the pipes in the walls.

Re: Re-using the heat in bathwater in Britain

#223

Post by blitzar »

hkt wrote: post #219
sokoloff wrote: post #104

Earlier quoted context omitted.

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.

Charitable of you to assume it is incompetence rather than malice :/

> You can’t make something both 100% mandatory and unregulated and then go shocked-Pikachu

The shocked-Pikachu face is the face they make when trying to figure out if anyone will notice the bribe they took to gift the contract to their buddy joe.

Re: Re-using the heat in bathwater in Britain

#224

Post by blitzar »

est31 wrote: post #78
yrgulation wrote: post #62

Earlier quoted context omitted.

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.

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.

> Solar farms are more economic to build than rooftop solar

For utility / central planners the cost of rooftop solar is ZERO. The owner of the roof pays it. Even better they get to buy the excess for 5p and sell it on at 35p. So they make money on every panel installed.

The utility pays for the solar farm and it costs $.

Re: Re-using the heat in bathwater in Britain

#225

Post by madaxe_again »

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.

I just built an off-grid cabin, and built heat reclamation into our plumbing in multiple locations, as it seemed silly not to.

Currently we’re using butane for our hot water, although I’m switching to biogas in the spring - the first stage of reclamation is a simple loop of hot water line around an insulated hutch in which the gas bottle lives - keeps it warm, as butane is useless in cold weather.

The second stage of reclamation is exactly what he proposes - our cold water line comes in, spirals around the waste water line for about 5/40 meters of respective length, in an insulated sleeve, before hitting the boiler.

Our input water is often barely above freezing - it’s the difference between having a cold/lukewarm shower and a scaldingly hot one.

Re: Re-using the heat in bathwater in Britain

#226

Post by koliber »

_nalply wrote: post #221

You shouldn't let warm water stay in a place with air contact. First it makes air humid and the affected rooms prone to mold, and second evaporation takes energy away, and while condensation might give the energy back you will have wet conditions. It's not very sanitary: warm and wet conditions for some time tend to encourage unwanted life. I armchair thought about a scheme: collect the bath and shower water in a tan…

In the winter, the air is very dry in my house and we use humidifiers. By leaving the bathwater in the bathtub, we could kill two birds with one stone.

Everything you say about ventilation is right though. I just don't know if calling this unsanitary is universally true. Maybe in climates where humidity is a problem to begin with, adding more humidity leads to less sanitary conditions.

Re: Re-using the heat in bathwater in Britain

#227

Post by _nalply »

koliber wrote: post #226
_nalply wrote: post #221

You shouldn't let warm water stay in a place with air contact. First it makes air humid and the affected rooms prone to mold, and second evaporation takes energy away, and while condensation might give the energy back you will have wet conditions. It's not very sanitary: warm and wet conditions for some time tend to encourage unwanted life. I armchair thought about a scheme: collect the bath and shower water in a tan…

In the winter, the air is very dry in my house and we use humidifiers. By leaving the bathwater in the bathtub, we could kill two birds with one stone. Everything you say about ventilation is right though. I just don't know if calling this unsanitary is universally true. Maybe in climates where humidity is a problem to begin with, adding more humidity leads to less sanitary conditions.

I agree, sometimes I do that, too. However the whole October was warm and humid and I never let the water stay in the bathtub. I carefully check for humidity: it should be between 40% and 60%. Sometimes I hang washed clothes in the room to get more humidity.

Re: Re-using the heat in bathwater in Britain

#228

Post by yurishimo »

_nalply wrote: post #222
Retric wrote: post #114

Earlier quoted context omitted.

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.

Once in Singapore when I was invited by a friend in a highrise flat I wanted to have a cold shower. However the cold water was still very warm and I didn't feel refreshed. I think the tropical sun warmed up the water in the pipes in the walls.

Where do they store the water? In NYC it's not uncommon for a building to have a holding tank on the roof of the building and then use gravity to supply "pressure" to the units in the building. If Singapore does something similar, it would be logical that the water would be warmer.

I lived on the top floor in a newer building in Dallas that pumped water the entire way and the pressure was noticeably less in my apartment than in the gym on the ground floor. The water was "cold" though!

Re: Re-using the heat in bathwater in Britain

#229

Post by roenxi »

oezi wrote: post #214
roenxi wrote: post #181

Earlier quoted context omitted.

The German situation is pretty illustrative of what would have happened to anyone stupid enough to try and build more power plants in Western Europe - nuclear stations would have been shut down, fossil fuels have been staring down the barrel of the burgeoning Green movement for at least 20 years and are somewhere close to being hit with legislation designed to make them unprofitable. Renewable haven't been cost-effec…

On the contrary: everyone who invested in Europe in building any sort of capacity was handsomely rewarded (incl. nuclear). Energy prices are so high because too many guarantees were given to too many parties to entince investment.

They aren't building new capacity in most forms of energy generation. Eg, in the UK they've basically only building renewables [0], and not in sufficient quantities to maintain their electricity production. The story is similar in most EU countries last I checked. Compare to, say, India to see a healthy approach [1].

Sure the market is signalling that anyone who can bring energy to the table will be rewarded, and trying desperately to keep people in the game who are already playing. But there'd be capacity built and the aggregate numbers wouldn't look so bad if new construction hadn't been politically blocked for years now.

They're choosing de-industrialisation rather than letting people use nuclear or fossil fuels. People really should be panicking about that, they are going to take a massive lifestyle hit. There will be trouble.

[0] https://en.wikipedia.org/wiki/File:UK_electricity_generation...

[1] https://en.wikipedia.org/wiki/File:India_electricity_product...

Re: Re-using the heat in bathwater in Britain

#230

Post by mnw21cam »

_nalply wrote: post #221

You shouldn't let warm water stay in a place with air contact. First it makes air humid and the affected rooms prone to mold, and second evaporation takes energy away, and while condensation might give the energy back you will have wet conditions. It's not very sanitary: warm and wet conditions for some time tend to encourage unwanted life. I armchair thought about a scheme: collect the bath and shower water in a tan…

I have been considering a grey water solution that would achieve two things. The bath in my house is upstairs, and I have an additional toilet downstairs, almost directly underneath. So, I could let the bathwater drain into a tank above the toilet cistern, from where it can slowly release its heat, and then use the water to fill the toilet cistern for flushing. That way, I save on heating and on water usage, and the water wouldn't be evaporating into the house causing humidity problems.

I did the calculations. A 120l bath has water costing £0.53 and heating (by gas, if we assume the incoming water is about 10C and heating it to 40C, about 4.2kWh) costing about £0.44. We probably get out of the bath and drain it when it's about 35C, so if the house is at 22C then there's about 1.8kWh of energy that would get transferred as heat to the house, about £0.19 worth. So, for a very modest cost of installing a tank and a little bit of plumbing (probably less than £200), we'd be saving £0.53 each day (assuming all that water gets used) plus £0.19 each day that we would have the heating on, probably half the year, which is around £230 per year. It'd pay itself off very quickly.

The main concern is that the holding tank doesn't become a bacterial breeding ground, so it may need some chemical discouragement every now and again, but that's hardly difficult.

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