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

#121

Post by brtkdotse » Wed, Jul 07, 2021, 7:06 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?

Usually 100-150mm wide. You don't do it yourself, you get a company with a drilling rig to come out and do it. Costs around 5k€.

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

#122

Post by distances » Wed, Jul 07, 2021, 7:09 AM UTC

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 :)

Helsinki too has district cooling in addition to district heating: https://www.helen.fi/en/news/2018/cooling-demand-in-helsinki...

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

#123

Post by brtkdotse » Wed, Jul 07, 2021, 7:10 AM UTC

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.

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

#124

Post by brtkdotse » Wed, Jul 07, 2021, 7:12 AM UTC

jcynix wrote: post #97

elric wrote: post #92

Earlier quoted context omitted.

> One big advantage is that they can also be run in reverse I don't get why this is an advantage. That's just plain old air conditioning, which is genreally considered to be a wasteful, energy guzzling luxury in colder climates. The heat pump hype is a bit puzzling to me. Here's a TreeHugger article which puts it better than I can: https://www.treehugger.com/why-are-there-so-many-fist-pumps-...

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.

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

#125

Post by c_o_n_v_e_x » Wed, Jul 07, 2021, 7:13 AM 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.

They're around in the US as well. Worked on one in downtown Austin in a previous life.

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

#126

Post by kpozin » Wed, Jul 07, 2021, 7:18 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.

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?

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

#127

Post by tomarr » Wed, Jul 07, 2021, 7:23 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?

They are designed for a number of air changes per hour/day which would be analogous I guess. I can't remember the number but a Google will tell you, it's different depending on the kind of environment (office/home etc)

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

#128

Post by coryrc » Wed, Jul 07, 2021, 7:30 AM UTC

jnsaff2 wrote: post #93

coryrc wrote: post #46

Earlier quoted context omitted.

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.

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.

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

#129

Post by ZeroGravitas » Wed, Jul 07, 2021, 7:42 AM UTC

simlan wrote: post #105

tacLog wrote: post #103

Earlier quoted context omitted.

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... .

Gas to electricity efficiency is low so you loose more then half the energy when producing electricity from gas. Using a 90 percent efficiency furnace to heat water directly with gas is the better solution. Assuming your electricity comes from gas plants.

Heat pumps can have COPs above one so if your entire electrical grid was gas fired then youd need a COP of around 3 to break even which is doable.

The grid is getting greener which means you win by even more if you electrify everything.

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

#130

Post by korethr » Wed, Jul 07, 2021, 7:43 AM UTC

adrianN wrote: post #81

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.

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.

A thought occurs to me just now: Why not also use that 40-60% waste heat to drive district cooling during the hot season? There's the absorption refrigeration cycle[1], which requires only a a heat input to drive the cycle to pump heat from the cold side to the hot side. Is the difference between the coefficient of performance between the more common vapor-compression cycle and the absorption cycle such that it is more cost effective to use the generated electricity to pump heat out of conditioned spaces during the hot season?

1. https://en.wikipedia.org/wiki/Absorption_refrigerator