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

#141

Post by laurencerowe » Wed, Jul 07, 2021, 8:37 AM UTC

ac29 wrote: post #94

phire wrote: post #71

This is old technology, I'm surprised the US hasn't already implemented it. They have been remote-controlling water heaters in New Zealand and Australia since the 50s. Just a simple relay installed in each house that responses to extra frequencies on the power lines in the 160-1600hz range. It's called ripple control, for obvious reasons. Each home gets assigned to one of several channels in each area so they can hav…

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.

> its substantially more efficient than burning said gas (or coal) to generate electricity, then using the electricity to heat water.

While this is true for basic resistive electric water heaters it's not for modern heat pump water heater which have energy factors of 3.5x which more then makes up for the 34% efficiency of a simple gas power plant (more modern combined cycle plants are 50-60% efficient) and the 95% efficiency of the grid.

Still works out much cheaper to use gas than electricity for heating in California with gas at $0.06/kWh vs $0.26/kWh for electricity.

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

#142

Post by jcynix » Wed, Jul 07, 2021, 8:50 AM UTC

kpozin wrote: post #126

brtkdotse wrote: post #123

Earlier quoted context omitted.

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.

Out of curiosity, what is the effect of this thick insulation on indoor CO₂ levels? Do these houses usually have ventilation systems that can compensate?

Our house (with a ground based heat pump) uses active ventilation with heat exchangers (and pollen filters) and as a result we have better indoor air than we've had in rented flats in all years before.

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

#143

Post by elric » Wed, Jul 07, 2021, 8:55 AM UTC

dvdkhlng wrote: post #119

devwastaken wrote: post #106

Earlier quoted context omitted.

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 lay…

Here in Belgium, electricity metering is switching from merely "kWh/year" to peak power draw (kW). Running a heater at 24kW will become very expensive.

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

#144

Post by jcynix » Wed, Jul 07, 2021, 9:00 AM UTC

elric wrote: post #104

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…

> 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. Good point. The source and destination of heat can be air, water, or "ground source". But it's still all just the same concept as A/C units. Pump heat to one place, using less energy than what it would take to heat it using resi…

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 water during the night.

We do live in a densely populated area and about every fifth hoiuse built here during the last 10 years uses a ground-based heat pump. As for electricity use: each house has two hours of "blockage" where the pump is not allowed to run, so that the power lines aren't stressed. That's no problem at all, because all houses are highly insulated and thus buffer rather good.

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

#145

Post by jcynix » Wed, Jul 07, 2021, 9:04 AM UTC

brtkdotse wrote: post #124

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…

> Airflow based heat pumps are less efficient, and more noisy outside, of course. This is only true when the ambient temperature dips below the geothermal temperature which depending on your location should make you prefer one over the other.

Germany. Where temperatures dip for some months below the geothermal temperature. Efficiency of air based pumps drops markedly when temperatures reach below 0 degrees Celsius.

And last but not least: ground / water carries much more energy per volume unit than air does. So air based heat pumps would make more sense in Europe's south and less sense farther north.

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

#146

Post by jcynix » Wed, Jul 07, 2021, 9:13 AM UTC

mprev wrote: post #101

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…

What sort of problems did you encounter drilling two 60m deep holes? How wide are they?

We did have no problems as the ground below consists mostly of clay for at least 100 meters. Two times at 60m was a political limit 10 years ago, because at 100 meters "suddenly" mining rules applied.

The tubes are about 100 mm in U-form, drilling mostly is offered in combination with the heat pump. And costs where payed of after about 7 years.

Costs and problems depend on the ground's structure. When I talked with the guys of the drilling team, they told me that problems occur if they work in hill regions with cavernous spots in the ground. That's because the tubes need firm contact to the ground to transfer heat.

Edit: here's an image of the drilling machine in operation: http://www.cynix.net/2008/img_1757.jpg and the tubes are those black ones on the rolls in the front.

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

#147

Post by manmal » Wed, Jul 07, 2021, 9:36 AM UTC

adrianN wrote: post #107

manmal wrote: post #96

Earlier quoted context omitted.

That’s impressive. We don’t use electricity for heating (heating and warm water are powered by community heat), and need 11kWh per day on average, excluding the EV. The EV adds another 5.5kWh per day.

My main consumers are probably the fridge and the oven. I made sure to buy an efficient fridge. Other than those I usually only have a laptop or two running. The washing machine only runs once or twice a week, most of the time only at 30°C.

Well we are four people in the household. I guess that does increase consumption.

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

#148

Post by z3t4 » Wed, Jul 07, 2021, 9:43 AM UTC

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.

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 where the houses are built to stay cool.

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

#149

Post by konschubert » Wed, Jul 07, 2021, 10:10 AM UTC

z3t4 wrote: post #148

brtkdotse wrote: post #123

Earlier quoted context omitted.

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.

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.

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

#150

Post by wodenokoto » Wed, Jul 07, 2021, 10:19 AM UTC

z3t4 wrote: post #148

brtkdotse wrote: post #123

Earlier quoted context omitted.

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.

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.