The humble water heater could be the savior of our energy infrastructure woes • Hacker News Board

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

#231

Post by _0w8t » Wed, Jul 07, 2021, 8:09 PM UTC

AnimalMuppet wrote: post #228

_0w8t wrote: post #117

Earlier quoted context omitted.

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

In a post parallel to yours, lmm says that gas-powered plants are low efficiency. Can either of you supply some documentation or references for your respective positions?

I already posted to another sub thread, https://www.ge.com/gas-power/resources/articles/2016/power-p... - gas power plant with 62% efficiency.

The best coal plants can archive 47% efficiency, https://www.brighthubengineering.com/power-plants/72369-comp...

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

#232

Post by giantg2 » Wed, Jul 07, 2021, 8:13 PM UTC

larsalmen wrote: post #225

giantg2 wrote: post #190

Earlier quoted context omitted.

It depends on the insulation type. If you're using mass as insulation, it can keep the house very cool. This is a common effect in stone houses and barns as they stay closer to the average daily/weekly tempature because it takes a long time for the tempature of that much mass to change.

Mass ≠ insulation. You can have mass as a buffer and regulator, but normally stone or brick and mortar houses simply shift the issues to later in the hot season. It is usually a more even temperature over any given timespan though, as you say. I'd think barns would have very low mass in comparison to their size, but would stay close to surrounding temp by way of having very little insulation and being very "drafty"

Yes, they aren't the same but can be applied to a similar end goal.

It doesn't completely shift the issue to later in the season. Yes, it will shift some of it, but you still have the night/day average effect. This can still be beneficial, especially if in a shady location.

Barns can be drafty if you are talking about wooden barns. Stone barns, or stone foundation barns built into a hillside, can actually be cooler inside than outside during the heat of the day. That's part of why horse owner sometimes leave their animals in the barn during the day and turn them out at night (typical summer schedule).

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

#233

Post by scotty79 » Wed, Jul 07, 2021, 8:20 PM UTC

sidewndr46 wrote: post #215

scotty79 wrote: post #201

Earlier quoted context omitted.

Units are fine. He just said he gets energy as heat in the amount 4 times higher than amount of electrical energy he uses to get it. It's fine to talk about it in terms of energy as it would be to talk about it in terms of power. And I'd argue that kWh is exactly the usual way of saying 3600000 joules. Also name "geothermal heat" for ground heat pumps might be a local US marketing term. In international English geoth…

I don't know anything about Iceland but I am using the definition from energy.gov https://www.energy.gov/energysaver/heat-and-cool/heat-pump-s... Geothermal works with either vertical holes in the ground or a big loop spread out horizontally. Neither one is very deep nor does it involve hot rocks.

Ah, geothermal heat pumps is perfectly accurate.

Geothermal heat on the other hand is a wider term https://en.m.wikipedia.org/wiki/Geothermal_heating of which geothermal heat pumps (ground source heat pumps) https://en.m.wikipedia.org/wiki/Ground_source_heat_pump are just a subset.

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

#234

Post by ttwwmm » Wed, Jul 07, 2021, 8:21 PM UTC

jhgb wrote: post #43

toomuchtodo wrote: post #6

Earlier quoted context omitted.

Yeah, timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection). New hotness are heat pump water heaters that are very efficient and can even add cool air to a conditioned spaces by their inherent operation. Electric vehicle charging orchestrated as large aggregate loads are what replaces “the humble water heater.” Tankless heaters are great if y…

> timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection) This is literally the first time I'm hearing of this as a concern. Our local recommendations are to keep tank temperature above 70C and you should be fine.

My heat pump water heater is at 140F all the time, maximizing the banked energy. There's an outboard mixing valve to reduce this to a safe temperature in the house.

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

#235

Post by ttwwmm » Wed, Jul 07, 2021, 8:22 PM UTC

caf wrote: post #24

ip26 wrote: post #10

Earlier quoted context omitted.

Heat pump water heaters do seem promising... But many water heaters live in cold basements... Classic tanked electric is so cheap to make & operate, I have come to think they may always be with us. (Though certainly a heat pump water heater is an easy choice in the right climate)

There are split system heat pump hot water heaters which allows you to exchange heat with the outside environment, eg. https://reclaimenergy.com.au/products/residential/

The all-in-one units can also be installed with ducting.

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

#236

Post by ttwwmm » Wed, Jul 07, 2021, 8:26 PM UTC

ip26 wrote: post #10

toomuchtodo wrote: post #6

Earlier quoted context omitted.

Yeah, timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection). New hotness are heat pump water heaters that are very efficient and can even add cool air to a conditioned spaces by their inherent operation. Electric vehicle charging orchestrated as large aggregate loads are what replaces “the humble water heater.” Tankless heaters are great if y…

Heat pump water heaters do seem promising... But many water heaters live in cold basements... Classic tanked electric is so cheap to make & operate, I have come to think they may always be with us. (Though certainly a heat pump water heater is an easy choice in the right climate)

Heat pump models usually have a resistive element for use when the heat pump can't keep up, or when the climate doesn't cooperate. Then you benefit from the efficiency whenever possible. (Here in coastal CA I have mine set to only ever use the heat pump since the climate is so mild.)

The up-front cost of a heat pump is definitely an issue. IMO we should be doing instant rebates to even out the cost between the two so that it's an easy decision.

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

#237

Post by larsalmen » Wed, Jul 07, 2021, 8:45 PM UTC

coryrc wrote: post #46

deviledeggs wrote: post #42

Earlier quoted context omitted.

Heat pump water heaters mentioned in the article are better for efficiency. They typically use half the energy of a normal water heater. And they cool the air around them, so if you live in a hot area they save more.

And if you live in a cold area, you get no efficiency advantage, pay more, and probably eventually leak coolant with a GWP of 2088.

Nah. It does not necessarily have to be an air-water heatpump either, colder climates more often use geo-thermal or ground-water loops as the energy-well. Then the surrounding climate have much less of an impact.

Refrigerant leaks are still an issue though, but moving to hydrocarbons and CO2 will mitigate that. Even R32 is a step up in that regard.

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

#238

Post by jcynix » Wed, Jul 07, 2021, 9:11 PM UTC

sidewndr46 wrote: post #182

jcynix wrote: post #97

Earlier quoted context omitted.

Good heat pumps aren't of the air conditioner type. Our heat pump uses two 60m deep drilled holes. Thus heat exchange happens in the ground, which is always more or less 10 degrees Celsuis. Heat exchange in the house happens through floor heating. So during a hit summer, the reverse capability just pumps the cold water through our floors (controlled for the dew point) and the warm floor water into the ground. That, c…

Is English a second language for you? I ask not because I am trying to insult, but what you are describing is just called geothermal heat in North America. It can also work in reverse if the air temperature is higher than the ground temperature. Also, you have your units wrong. Electrical demand is measured in just kilowatts (kw). Actual usage is in kilowatts-hours (kwh) which is just an unusual way of saying joules.

Energy is specified in KWh here, i.e. we have a metering system installed which states that our heat pump delivered 128024 KWh of heat and the electricity company's metering system tells me that it used 34844 KWh of electrical energy to do this.

Anyway, for one unit input we got about 3.6 units of output, which has been produced with an almost zero carbon footprint, as we buy only ecologically produced electricity.

And yes, English is a second language.

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

#239

Post by jcynix » Wed, Jul 07, 2021, 9:14 PM UTC

bluGill wrote: post #167

jcynix wrote: post #144

Earlier quoted context omitted.

There's no refrigerant here. Our heat pump uses plain water mixed with an anti-freezing agent. Just like the cooler in a car does. And there are control displays where you control all operating parameters. As for the "pump heat from here to there" ... while we are cooling we are warming the ground below. And as at our place, the ground's consistency keeps the warmth rather local, we reuse it later when we warm our wa…

There is refrigerant there. It is contained inside the system, and only your water mix leaves, but there is still refrigerant inside and it can leak.

That's correct. I was comparing our system to existing systems which directly use a refrigerant sent into the ground loop. Our heat pump itself is a closed system just as a refrigerator, and works indirectly via the water cycle used outside.

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

#240

Post by larsalmen » Wed, Jul 07, 2021, 9:21 PM UTC

coryrc wrote: post #128

jnsaff2 wrote: post #93

Earlier quoted context omitted.

I live in a cool place. This winter we had extended periods of -20C. Heat pump efficiency drops, but still stays above 2. SCOP (for year round average for heating coefficient of performance) units sold now are better than 5. Also, if you are worried about the refrigerant leaking, you can sacrifice a little bit of efficiency and buy a unit using CO2 as a refrigerant with a GWP of you know: 1. I think the biggest probl…

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.