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

#221

Post by kragen » Wed, Jul 07, 2021, 6:01 PM UTC

mabbo wrote: post #210

philote wrote: post #208

Earlier quoted context omitted.

Doesn't that increase the lake's overall temp though?

Probably not, because there's a second interesting fact about the system (which I just learned): the water isn't returned to the lake directly. Instead it's used as an input to the filtration plants, cleaned, and used as municipal water. I'm not sure what the overall effect of getting slightly warmer water in the municipal system is, but I bet it's a win overall since we spend so much energy heating up water (as per…

1600 km³ × .1 kcal/ℓ is 670 petajoules, so that's the energy input you'd need to heat the lake up by 0.1°. World marketed energy consumption is about 20 TW, so the entire world economy could heat the lake up at about 0.23° per day if you covered it in a blanket first. So it's not completely out of the question, but only 2.7 million people live in Toronto, so Toronto probably only uses about 20 GW.

By comparison, the lake's surface area is 19000 km², so when the sun is shining on it (at a slanting angle, as it always does that far north), it's receiving about 10 TW of solar energy, half the amount used by the entire human economy. It reflects about 10% of that into space and converts the rest into heat, then re-emits it as longwave infrared light, half at night.

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

#222

Post by elric » Wed, Jul 07, 2021, 6:33 PM UTC

BizarroLand wrote: post #218

elric wrote: post #193

Earlier quoted context omitted.

That many cars seem undesirable in urban areas (or anywhere, really, but let's not go there). From a bit of quick searching, EV battery packs are roughly the same volume as a fridge, and weigh in around 300kg (that was a Nissan Leaf specifically, but I assume others are similar). I don't have enough room for a fridge sized battery in my house. It'd be nice if they could shrink a bit. With enough capacity to run a tan…

On the other hand, if every home had a load leveling battery system of even modest storage capacity, say, 15 minutes average power usage covered, then load leveling would not be nearly the problem it is today.

You're probably right. Something like a small battery per home, and a bigger battery per block would likely go a very long way in creating a more stable grid. That's probably cheaper than "real" grid scale storage. What would a 15 minute battery look like? Probably not much bigger than a car battery. Install one with every power meter. Sounds so easy that I can't help but wonder what the catch is. Why aren't we doing this?

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

#223

Post by stdgy » Wed, Jul 07, 2021, 6:43 PM UTC

bluGill wrote: post #162

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…

> How do more efficient water heaters in any way, shape or form help solve the renewable variable rate energy to constant energy problem? I feel like I must be missing something obvious A large portion of our world energy use is to make heat. Thus if you can make the heat you need when there is plenty of renewable energy available, and then store it for use latter that is a large win. Sure we can't turn that heat bac…

Good points! I'm certainly in favor of time-shifting demand to meet supply to maximally utilize renewables. Let's grab as much of this low hanging as we can.

I just thought the framework of his argument was rather odd. Better water heaters are framed as being a way to avoid constructing power storage systems that convert variable renewable energy into steady baseline power, which feels like an argument that doesn't hold up. We'll still need some way to supply steady power to run AC units, heaters, and other big power draws all night, no matter what type of water heaters we use!

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

#224

Post by matheusmoreira » Wed, Jul 07, 2021, 6:46 PM UTC

landemva wrote: post #204

matheusmoreira wrote: post #173

Earlier quoted context omitted.

Is it possible to hook up computer heat sinks to these things? I figure it'd be better to pump the heat outside my home instead of dissipating it into my air conditioned rooms...

I want that for my fridge. Move the compressor and radiator somewhere else than the kitchen.

That'd be cool. Those things make a lot of noise. Would be nice if the refrigeration hardware itself was located as far as possible from the living areas.

What if homes had some kind of centralized modular heat exchanging infrastructure? That way we could move heat from hot things that need to be cold to cold things that need to be hot. Move heat from my computers to a water heater or something. Gotta use all that excess heat for something, right?

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

#225

Post by larsalmen » Wed, Jul 07, 2021, 7:46 PM UTC

giantg2 wrote: post #190

bluGill wrote: post #165

Earlier quoted context omitted.

If you are only worried about natural cooling, insulation is not the answer. You want a poor insulated house with a lot of shade, and large open windows for the wind to blow through. Most people these days want more than natural cooling. As soon as you decide to have an AC system installed more insulation is better for the reasons you state.

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"

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

#226

Post by nine_k » Wed, Jul 07, 2021, 7:46 PM UTC

_0w8t wrote: post #117

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.

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

Wow, TIL! Thanks.

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

#227

Post by jfengel » Wed, Jul 07, 2021, 7:46 PM UTC

fy20 wrote: post #69

nine_k wrote: post #62

Earlier quoted context omitted.

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 :)

District cooling (as opposed to district heating) is fairly common in Gulf countries.

I hadn't heard the term "district heating" before, but it makes sense.

The name puts me in mind of a chain called District Taco, but unfortunately that doesn't mean a supply of tacos piped directly into your house.

https://www.districttaco.com/

Not even slightly authentically Mexican, but nonetheless quite tasty.

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

#228

Post by AnimalMuppet » Wed, Jul 07, 2021, 7:52 PM UTC

_0w8t wrote: post #117

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.

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?

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

#229

Post by opwieurposiu » Wed, Jul 07, 2021, 7:56 PM UTC

jojohohanon wrote: post #214

opwieurposiu wrote: post #212

I have 1200w of solar panels hooked directly to the lower element of my hot water heater. I sized the element to match the source impedance of the panels in full sun. If you use a MPPT system you could get 50% more power in partial shade but panels were so cheap it was not worth the complexity. The top heating element is still on city power as backup but I rarely use it. The water will get up to 80c on a sunny day, s…

When hooked up to the grid, converting from electricity to heat for storage makes alot of sense (to me). But I'm curious about your case: why not use the old-fashioned solar water panels to create hot water directly?

Solar hot water panels would make 4x the heat for the same area, but are too complex and expensive to install. They need pumps, expansion chamber, control system, antifreeze, new larger hot water tank. They are too heavy to get on the roof by yourself.

My non-grid connected solar cost about $1200, and was easy to DIY. No $1000 permit needed since it is not connected to the grid. No moving parts and almost no electronics. House now uses only 8-12 kWh a day.

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

#230

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

benhurmarcel wrote: post #155

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.

You're only paying for that heat in the winter though.

Hence the preface of "cold area", but my heating season is over 6 months. The ROI is already long in HWHP even assuming the best numbers, and often negative once you account for reality in areas which get cold.