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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

#111

Post by MertsA »

tacLog wrote: post #103
ac29 wrote: post #94

Earlier quoted context omitted.

About half of the US uses natural gas for water heating - its substantially more efficient than burning said gas (or coal) to generate electricity, then using the electricity to heat water.

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 tremendously efficient.

Figure on the order of 60% efficient for the best natural gas power plants vs. 95% efficient for a condensing gas water heater. Not to mention the drastic reduction in expensive electrical infrastructure, the power plant, etc.

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

#112

Post by MertsA »

dashundchen wrote: post #75
_huayra_ wrote: post #68

Earlier quoted context omitted.

My parents got a heat pump water heater (electric) a few months ago and it's great. Definitely the priciest option, but it sips electricity and also cools the area around it (basically operating as an "inside out refridgerator"). In this same remodel I also convinced them to get heat pump / AC combo unit to replace the old gas furnace. Again amazingly cheap (even compared to gas), but also higher upfront cost. This i…

Definitely works in cold areas. Most heat pump manufacturers offer separate models for cold climates below zero. The worst case is efficiency approaches resistance heating at 1.0, maybe with backup resistance heat strips. But a well designed system to match worst case load should rarely see this. For some reason they've really only been widely available in the US in the past few years.

> But a well designed system to match worst case load should rarely see this.

Well actually it'll see it quite often. Every time a heat pump goes into defrost mode it'll use resistive heating inside to hold over while it's working like a traditional air conditioner to thaw out the outdoor coils.

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

#113

Post by thehappypm »

elric wrote: post #102

Lots of good discussions about water heating in this thread. But it's such a tricky topic. Tankless water heaters are pretty efficient, but when you need hot water, you briefly use huge amounts of energy. It's for this reason that they almost always use natural gas. Electric tankless heaters are a great way to cause brownouts. They're roughly the size of a microwave oven, so they can fit in pretty much any kind of dw…

Heat pumps are not noisy, though. Mine are completely silent.

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

#114

Post by judge2020 »

stdgy wrote: post #108

Am I the only one that find this article incredibly confusing? It starts off talking about wanting to move energy production to renewable sources. Great, I'm with you so far. A major issue with renewable energy (solar and wind) is that they're variable, not constant. This results in uneven power. The wind doesn't blow, it's cloudy or it's night time. So we need a way to convert this variable renewable energy into con…

Maybe this author has a stake in some up-and-coming smart water heater company whose sales pitch is that they only heat up the tanks when it would use only renewable energy?

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

#115

Post by _ph_ »

stdgy wrote: post #108

Am I the only one that find this article incredibly confusing? It starts off talking about wanting to move energy production to renewable sources. Great, I'm with you so far. A major issue with renewable energy (solar and wind) is that they're variable, not constant. This results in uneven power. The wind doesn't blow, it's cloudy or it's night time. So we need a way to convert this variable renewable energy into con…

The point is, that we can move demand around. The smart water-heaters with the ability to store heat are not only more efficient, they can be run when a lot of electricity is available and can be shut off, when there isn't. Yes, we also will need some amount of storage to produce electricity when demand exceeds production, moving the time of demand goes a long way on managing renewables.

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

#116

Post by evandijk70 »

stdgy wrote: post #108

Am I the only one that find this article incredibly confusing? It starts off talking about wanting to move energy production to renewable sources. Great, I'm with you so far. A major issue with renewable energy (solar and wind) is that they're variable, not constant. This results in uneven power. The wind doesn't blow, it's cloudy or it's night time. So we need a way to convert this variable renewable energy into con…

The idea was that you run the water heaters at a time when demand for electricity is low, and supply is high. The water will stay warm for quite some time and can be used later. For example - run the water heater at 3am during a windy night, so people can shower in the morning

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

#117

Post by _0w8t »

nine_k wrote: post #63
jdsully wrote: post #33

Earlier quoted context omitted.

The majority of your savings are from switching to gas from electric. Gas is significantly cheaper per BTU. Gas tank heaters are still pretty efficient. Especially if insulated.

It's easy to understand. First, a gas-fired power plant converts about 40% of thermal energy to electricity, discarding 60% to further heat the planet. Then a few more percent are lost in transmission lines and voltage-lowering transformers. Only then that electricity is used to heat water or air in one's house. If you just directly burn that same gas in the house to produce heat, it's nearly 3x as efficient.

The modern gas power plants archive over 60% efficiency. It is with coal that one gets at best 45%.

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

#118

Post by diarrhea »

WhompingWindows wrote: post #28
s0rce wrote: post #18

Virtual battery, there is an interesting project to do a similar thing with aluminum smelters where you heat them and operate at full capacity off-peak and then during peak electricity usage you run slower. Since a smelter consumes so much power this can significantly level the grid usage.

Would that be economical? Places with abundant geothermal power like Iceland are probably going to make much cheaper aluminum smelting than anywhere else.

Not all thermal energy is created equal. The temperature level plays a huge role, and I imagine geothermal is on the low end. Suitable for household heating and the like, but not for smelting metal. From hydro, you generate electricity, and that can be converted to thermal energy on very high temperature levels.

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

#119

Post by dvdkhlng »

devwastaken wrote: post #106
elric wrote: post #102

Lots of good discussions about water heating in this thread. But it's such a tricky topic. Tankless water heaters are pretty efficient, but when you need hot water, you briefly use huge amounts of energy. It's for this reason that they almost always use natural gas. Electric tankless heaters are a great way to cause brownouts. They're roughly the size of a microwave oven, so they can fit in pretty much any kind of dw…

Tankless are also useless if you don't have perfect water, and even if you do you have to descale them every year. The calcium, iron, and others in your water builds up in the small copper pipes, and an acidic cleaner is required to remove it. If youve ever used a Keurig it's similar. Propane water tanks are pretty bulletproof. Even with bad water they just truck, and require no electricity to operate, unlike some ot…

Where I live, tankless heaters are pretty wide-spread. They connect to 3-phase power supply, heating at a variable power level up to 24 kW [1]. They need almost no maintenance, nobody I know has ever descaled one. I think the better units directly run the heating wires through the water, so they do not calcify due to small surface area (or maybe the huge temperature gradient when operated breaks the calcification layer).

Usually you operate them until they break (maybe around 10 years), then get a replacement heater for like 400 €.

[1] https://www.stiebel-eltron.co.uk/en/products-solutions/dhw/i...

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

#120

Post by _0w8t »

nine_k wrote: post #84
lmm wrote: post #76

Earlier quoted context omitted.

Gas-fired power plants are already known to be particularly low-efficiency. They're not representative of electricity production in general.

I wonder what kind of thermal electricity generation achieves efficiency above, say, 45%. Efficiency of thermal engines, even when you recycle the waste heat of the gas turbine exhaust with another cascade using a low-boiling substance and another turbine, is limited. I only mentioned the gas-fired power station to make it an apples-to-apples comparison. It would be hard to compare e.g. to solar panels, even though d…

https://www.ge.com/gas-power/resources/articles/2016/power-p... is over 62% efficient.
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