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The humble water heater could be the savior of our energy infrastructure woes

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Re: The humble water heater could be the savior of our energy infrastructure woes

#241

Post by WalterBright »

bluGill wrote: post #169
WalterBright wrote: post #138

I've proposed this (water heater as battery) innumerable times here on HN. Glad to see it finally catching on! You can do the same thing with the HVAC system. For example, when the sun is high and electricity is cheap, have the A/C cooling a large mass of stone or concrete. Then, blow air over it at night to keep the house cool.

You are not the first to propose it, and won't be the last. It is obvious to any engineer who spends more than a few minutes thinking about the problem. It works in practice too, but the space needed means most people don't bother.

> obvious

You'd be surprised at the resistance to the idea it always engendered.

Re: The humble water heater could be the savior of our energy infrastructure woes

#242

Post by coryrc »

larsalmen wrote: post #240
coryrc wrote: post #128

Earlier quoted context omitted.

If the hot water heat pump is a single unit (which is the vast majority of residential installations) and indoors, it is just stealing heat from your regular heating system. You're paying for that heat, so you aren't getting COP > 1.

Who has that, a "indoor heat pump"? That's just stupid. Sure, exhaust air heatpumps "use" the (excess) heat from indoors, but that would just get expelled anyways.

https://www.hotwater.com/water-heaters/residential/hybrid-el... this is what people are talking about when they reference hot water heat pumps without qualification, because they are the vast majority of the market.

There is no excess indoor heat in winter in 99.9%+ non-passivhaus homes.

Re: The humble water heater could be the savior of our energy infrastructure woes

#243

Post by tacLog »

MertsA wrote: post #111
tacLog wrote: post #103

Earlier quoted context omitted.

Is it though? It might be cheaper in many area's but this source [1] says that the grid transmission loss is only 5%. Am I missing something that makes it a more substantial difference? Not to mention that piping all that natural gas out to each home has to result in a certain amount of leakage and energy cost in just the pumping itself. [1] https://www.eia.gov/tools/faqs/faq.php?id=105&t=3#:~:text=Th... .

Yes, even the most efficient natural gas plants aren't going to come close to the efficiency of a modern condensing gas water heater. For the water heater it's just a matter of a single heat exchange process from the exhaust to the water. For a combined cycle power plant you're dealing with a gas turbine and boiling water to run additional steam turbines but in the end converting heat into mechanical energy is not tr…

Thank you, I was not aware that natural gas generation was so inefficient.

I wonder how from a pure greenhouse gasses perspective, the numbers stack up. I know that leaked methane is much worse than CO2. 28x according to [1]

This source [2] says that the grid looses: 2% - 5% of gas between provider and consumer.

Even assuming that your grid is 90% just gas plants stil.

30% loss at the power plant, 5% loss from electrical grid. So for every unit of water heated you are wasting 35% of the energy.

Vs say 2% loss in the natural gas grid. but that 2% is 28x worse than burned CO2.

Am I completely wrong in saying that from a pure this hurts the planet more electric based water heaters often probably still win?

[1] https://www.epa.gov/ghgemissions/understanding-global-warmin... [2] https://pubs.naruc.org/pub/FA86BB52-AE3F-D8AC-B295-801BD6DC6...

Re: The humble water heater could be the savior of our energy infrastructure woes

#244

Post by elil17 »

Maximus9000 wrote: post #185
elil17 wrote: post #45

Another type for thermal battery: ice thermal storage. Instead of running AC, it’s a freezer that makes ice during the night (using off-peak electricity and taking advantage of the cooler nighttime air) and then melts it during the day to cool large buildings. They’re a ridiculously good idea if you’re running a large enough HVAC system - they can even lower capital costs compared to traditional systems. Unfortunatel…

If I recall correctly, these are not suitable for residential use, right?

One company tried to make a residential version (called Ice Bear, IIRC), but it was unsuccessful. There’s no reason it couldn’t be practical, though. Especially with something like some prototype concepts which propose putting all heating and cooling appliances (refrigerator, water heater, HVAC, and possibly even a drying machine) on a single heat pump loop, ice thermal storage could become economical for single family homes in the near future.

Re: The humble water heater could be the savior of our energy infrastructure woes

#245

Post by elil17 »

nraynaud wrote: post #183
elil17 wrote: post #45

Another type for thermal battery: ice thermal storage. Instead of running AC, it’s a freezer that makes ice during the night (using off-peak electricity and taking advantage of the cooler nighttime air) and then melts it during the day to cool large buildings. They’re a ridiculously good idea if you’re running a large enough HVAC system - they can even lower capital costs compared to traditional systems. Unfortunatel…

I'm curious of the mechanics of this, since the expansion of ice makes it a pain to manage.

Surprisingly simple design, actually. The water sits in a large tank with plenty of room to expand and contract. Pipes filled with refrigerant run inside the tank. Here’s a photo: https://images.app.goo.gl/Td6RdFbuVE8QJAmu6

Re: The humble water heater could be the savior of our energy infrastructure woes

#246

Post by elil17 »

NickM wrote: post #196
elil17 wrote: post #45

Another type for thermal battery: ice thermal storage. Instead of running AC, it’s a freezer that makes ice during the night (using off-peak electricity and taking advantage of the cooler nighttime air) and then melts it during the day to cool large buildings. They’re a ridiculously good idea if you’re running a large enough HVAC system - they can even lower capital costs compared to traditional systems. Unfortunatel…

This seems like it could backfire if we start to get the majority of our electricity from solar, though, right? Nighttime may not always be considered off-peak.

Well you’d just make the ice whenever it’s cheapest, taking into account the effects of cold air and of electricity prices. In the future it might make sense to make the ice when it’s warm out because power is nearly free at those times. But a smart building automation system could know when cloud cover is predicted and make ice the night before.

Re: The humble water heater could be the savior of our energy infrastructure woes

#247

Post by larsalmen »

coryrc wrote: post #242
larsalmen wrote: post #240

Earlier quoted context omitted.

Who has that, a "indoor heat pump"? That's just stupid. Sure, exhaust air heatpumps "use" the (excess) heat from indoors, but that would just get expelled anyways.

https://www.hotwater.com/water-heaters/residential/hybrid-el... this is what people are talking about when they reference hot water heat pumps without qualification, because they are the vast majority of the market. There is no excess indoor heat in winter in 99.9%+ non-passivhaus homes.

Right, I stand corrected. I had never seen such a heatpump (based in the nordics, that concept would never fly), and I'll agree with you that in homes heated by "regular means" (resistive/electrical, fossil fuels) they add little to no value, simply adding complexity. In heating season they would just siphon heat energy from the rest of the house...

(They would however de-humudify the space they are in, but that's another thing...)

I'd argue that every house that has any sort of ventilation, even naturally aspirated ones, have excess heat in that any amount of air leaving the house "unreclaimed" while there is any heating need contains wasted energy.

Heatpumps using that energy are very prevalent in the Nordics and Scandinavia, even with a majority of the time being heating season here.

Re: The humble water heater could be the savior of our energy infrastructure woes

#248

Post by thebiss »

brtkdotse wrote: post #123
cycomanic wrote: post #88

In Northern Europe heat pumps are now pretty much standard for new homes. They reduce heating bills quite dramatically compared to other technology. In particular if combined with solar power. One big advantage is that they can also be run in reverse so you could cool the house in summer (although you might need a special heat pump to do this, especially to separate from the hot water). In areas where it gets very co…

Another thing Northern Europe has going for it is that we generally go all-in on insulation. 300mm of insulation are norm in newly built house, meaning you can heat a whole house above the Arctic line with less than 5000 kWh a year. Insulation is _dirt cheap_ compared to lifetime heating costs AND it also keeps the house cool during the summer. Such a no-brainer.

We have insulation thickness standards in the US, varying by weather "zone", but for residential construction they seem to be lightly enforced, and efficiency tests are rare to non-existant. (For an illustration of how we typically insulate, see [0].)

It's only one data point, but I'm in New England and from my home office I've watched builders replace 3 1960's-era homes with large colonials. Each is insulated with fiberglass, no visible foam, and nothing outside the sheathing (exterior plywood) except vapor paper / tyvek.

Sure, it meets code requirements for inches of insulation, but it's far from air tight or efficient.

[0] https://www.energy.gov/energysaver/where-insulate-home

Re: The humble water heater could be the savior of our energy infrastructure woes

#249

Post by z3t4 »

wodenokoto wrote: post #150
z3t4 wrote: post #148

Earlier quoted context omitted.

The isolation is made to keep the house hot. About 10 degrees hotter then the outside (without the heater on). This is usually not a problem as temperatures are around 15 during the summer and you can open a few windows to let the hot air out. It does become a problem however when we get extreme temperatures like +30 C as you cant lower the temp by opening a window. Compared to south europe and other warm climates wh…

Glass helps trap solar heat, but other than that any form of insulation keeps heat from entering and escaping. This is how your thermos knows wether to keep your drink hot or cold. So except for the sun shining through windows, insulation keeps heat out of your house.

new product idea: black plate (same as Northern roofs) thermos with glass windows. Would only work if you wanted to keep the drink hot though.

Re: The humble water heater could be the savior of our energy infrastructure woes

#250

Post by z3t4 »

konschubert wrote: post #149
z3t4 wrote: post #148

Earlier quoted context omitted.

The isolation is made to keep the house hot. About 10 degrees hotter then the outside (without the heater on). This is usually not a problem as temperatures are around 15 during the summer and you can open a few windows to let the hot air out. It does become a problem however when we get extreme temperatures like +30 C as you cant lower the temp by opening a window. Compared to south europe and other warm climates wh…

As far as I know, Insulation should keep the house cool in summer, because it keeps the heat out. Of course, once the heat is in, you need a way to get it out (at night, through windows). Unlike a greenhouse, insulation is not directional.

It basically becomes a greenhouse if you have windows, and of course the windows have three layers which prevents the precious warm air to leak out. Also the roof is black metal. You basically don't need to have the heater on if it's a sunny winter day - because the heating from the sun.

The biggest problem though is the dryness during the winter, cold air comes in and expands, lowering the relative humidity, warm moisturous air is pushed out by mechanical fans. You get extreme dryness, lower then in the desert, which is not good for mucus membranes. I believe that if we could revolutionise air conditioning systems we could prevent the next pandemic (and maybe help the global climate).

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