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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

#81

Post by adrianN »

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.

If you use the electricity to run a heat pump you can get a couple more Joules out of the gas. Ideally your gas-plant is also connected to a district heating network, so the 60% heat are not completely lost.

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

#82

Post by adrianN »

gnicholas wrote: post #47
krrrh wrote: post #41

Earlier quoted context omitted.

I had a friend who spent months measuring the power output of all his appliances and lights trying to figure out where half his electricity bill was going. He finally realized it was the hot water recirculator.

We have an under-sink unit that has hot water ready 24/7. After hooking it up, I noticed it increased our monthly bill by about $15. I bought a used Wemo plug for $10 and set it to only be on for 3 hours in the morning and 3 hours at night. Now we have hot water at any of the times when we actually would want it, and we aren't wasting money/energy to keep hot water on tap 24/7.

Make sure to set the temperature really high if you don't run it continuously or you risk breeding Legionella.

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

#83

Post by simfoo »

nine_k wrote: post #62
selectodude wrote: post #52

Earlier quoted context omitted.

There is a large building in Chicago that basically contains a giant ice cube. https://www.enwave.com/locations/chicago.htm

From their website I gleaned that they have 5 facilities, and several miles of piping that carries ice-cold water to their customers, large buildings around. It's the maximally outsourced air-conditioning solution I ever saw :)

The city of Munich in Germany actually has a cooling network to cool large buildings in the city centre. See here: https://www.swm.de/geschaeftskunden/fernkaelte

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

#84

Post by nine_k »

lmm wrote: post #76
nine_k wrote: post #63

Earlier quoted context omitted.

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.

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 direct hearing by concentrated sunlight might be feasible.

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

#85

Post by adrianN »

mabbo wrote: post #26
xupybd wrote: post #5

"This approach can be deployed far faster than dam construction" Can we really manufacturer that many hot water tanks in less time than building a damn?

One neat difference is that dams only provide benefits when they're done. Building a big dam takes a long time. But with the water heater solution, every time a water heater is replaced, we get the partial benefits immediately.

The same applies for nuclear power plants vs renewables.

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

#86

Post by perihelions »

m463 wrote: post #65
perihelions wrote: post #58

Can you also store cold cheaply? For example, to run an A/C early in the morning, and put the cold in an insulated tank of a room-temperature phase change material [0]? [0] https://en.wikipedia.org/wiki/Phase-change_material#Common_P...

A long time ago I read an article that made an impression on me. This guy had developed a house using logs that were basically phase change material. I think part of the design was to build almost a house within a house. An inside wall made of the logs containing pine sap that would change phase at a comfortable temperature. So with sun it would reach that temperature then start absorbing it and becoming more liquid,…

Oh thanks for that. Indeed it seems to be a phase change of resin in pine logs.

https://enertia.com/about.html

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

#87

Post by deviledeggs »

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.

> For some reason they've really only been widely available in the US in the past few years.

I think it's cheap energy. In places like Japan they've been using heat pumps a long time

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

#88

Post by cycomanic »

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 cool, one can also use connect the heat pump to the ground as heat sink which improves efficiency even more.

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

#89

Post by RHSeeger »

temporallobe wrote: post #29

I have a tankless hot water heater system in my new home that runs on a city natural gas line. It’s super efficient and thus my energy bills are very low compared to what I used to pay for the traditional electric hot water heater in my previous home, however it’s not a silver bullet. I find myself running the water for a ridiculously long time in order for the water to start getting hot, sometimes for more than a mi…

Its worth noting that you can combine an on-demand (tankless) hot water system with at tank. The on demand system heats the water and stores it in the tank (which is not a water heater). The tank itself, since it has no heating elements, can be _very_ thermally efficient. You get the benefits of both systems (though it does cost more to install, obviously)

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

#90

Post by choeger »

manmal wrote: post #74

Most newly built electric cars have a 50+ kWh battery. Imagine if smart meters could use _that_, regardless of where the car is currently parked and plugged in. 50kWh is in excess of what most households use in electricity on most days.

This will be the case in the next couple of years. Wall boxes are inherently smart (that is, controllable). So as a sink, the concept works somewhat already. But most cars won't be empty all the time. Also as source the 50kWh will only be usable as an emergency backup for the owner of the vehicle and only if they have the infrastructure to consume directed current. No one will let their own battery drain for the greater good. For public use cases people won't offer to unload more than maybe half of the capacity, realistically maybe 25% on average.
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