HN Theater @HNTheaterMonth

Yes, apparently there have been huge advances in the efficiency of heat pumps since then. And this is why ground source heat pumps are less of a thing these days: you don't need the help of that underground temperature as much.

This guy gets really excited about heat pumps:

https://www.youtube.com/watch?v=MFEHFsO-XSI

https://www.youtube.com/watch?v=43XKfuptnik

⬐ taylodl

Thanks for the links!

>Burning something for heat is always more effective, cheaper, and produces fewer emissions compared to an electric heater... >If you’re getting electric heat from coal fired steam that’s always worse than burning the coal locally to heat something, and this is true for all emission-producing power sources.

Apparently you can actually save natural gas with electric heat and a heat pump.

https://youtu.be/MFEHFsO-XSI

Article failed to mention that wind/solar storage can be usefully teamed-up with the another (renewable) energy source, the heat in the ground ... which is nearby many of our houses.

Today's heat pumps can work well for many down to outdoor temperatures of about 5 degrees F (-15C). They'll bring down the cost of using the other sources. [https://www.youtube.com/watch?v=MFEHFsO-XSI]

So off-peak pre-cooling, did I read your comment right?

That has been talked about quite a bit actually. Technology Connections made a nice YouTube video (https://www.youtube.com/watch?v=MFEHFsO-XSI) about it.

I'm a bit surprised though that off-peak pre-cooling isn't more common or even widely incentivised, especially with the rise of smart home and IoT stuff. All I've seen is reduction (so less cooling) during peak, if I'm not remembering wrong, people were quite annoyed with that.

⬐ lisper

It only works on well-insulated buildings. There are a lot of older legacy structures where the temperature equalizes very quickly once you turn off the climate controls.

⬐ criddell

My home's HVAC system is getting old and when I had the HVAC technician out for the summer inspection I asked about a new system (mine was installed in 2008). He said a new one will be a lot more energy efficient and (depending on the system we choose) would have more settings than off and blast cold.

I mentioned that this one struggles to hold 75 when it's much over 100 degrees outside and was told it doesn't matter what system I buy, that will always be true. The systems can only pull down the temperature around 25 degrees Fahrenheit. Is that true? If so, how do stores hold their temperature so low?

⬐ lfowles

Seems about accurate, but the variable speed systems are a big QoL upgrade regardless. Just being able to have AC on lower speeds has helped a lot with humidity even when the house doesn't necessarily need cooling. We upgraded last summer from a 3 ton unit to a 3.5 ton unit (max size our ducts would support). It's still struggling to hold 75 when over 100 outside and some upper rooms hit 80, but that's more down to our ducts and layout of the house. The lower humidity and constant (yet inaudibly low) air flow makes it feel much more comfortable at 75 than with the old system.

⬐ criddell

What I want is an oversized system with variable speed but they seem reluctant to sell me an oversized system.

⬐ daggersandscars

This is from 2016, but an oversized system can be more prone to having the condenser freeze.

Ask This Old House (https://www.youtube.com/watch?v=-33wjzNxgSw)

⬐ criddell

The first time I had my condenser freeze, I called the HVAC company we use and they had me shut off the system for 30 minutes and it started working again. When their tech came out, he found the refrigerant pressure was low so he corrected that and let us know that when it's hot out (105+) don't ask the AC to keep the house at 75 because it will run non-stop and freeze again. That's when I started thinking about buying an oversized system.

Thanks for posting this video. It's pretty good, but it raises some questions for me as well (like was the 4 ton system in the video a variable speed system?).

⬐ elil17

No that's not true, you could oversize the system or improve your insulation. The condensing temperature is typically 45 F and the evaporating temperature is typically 120 F - in layman's terms if the building were perfectly insulated, you could get it to 45 F as long as the external temp didn't go above 120 F.

⬐ mrfusion

Besides that you actually want your unit to struggle a little in order to have enough run time to control humidity.

It’s actually a problem if you have an overpowered system.

⬐ criddell

When is the humidity a problem? If I have my thermostat set to 73 and the system is maintaining that through the day and night, will humidity be an issue? A variable speed system in a typically insulated home will likely be running at a very low level most of the day.

I can see it being a problem if I come back from vacation and change the thermostat from 85 to 73 and ask the A/C to get there ASAP, but even then the controller could know how much moisture is in the air and make sure the temperature drop is slow enough to deal with condensation.

⬐ kayodelycaon

That's gotta be bullshit. I live in a 1930s house with little to no insulation. I have curtains on all of the windows to block heat and my ground floor can maintain 72°F all day during 100°F weather. Same with my upstairs office using a window air conditioner. (The rest of the upstairs is a lost cause.)

There might a reason for that though. There are dampers in the basement air ducting I can use to redirect airflow, so I'm running a system designed for 1,300 sqft to cool an area that's half that. My office window unit is overkill for the room I'm in.

I've optimized this using data from home assistant, which continuously monitors the outside weather and temperatures (plus occupancy, light level (lux), light bulbs, etc) for every room.

⬐ bluGill

> The systems can only pull down the temperature around 25 degrees Fahrenheit. Is that true?

When sized correctly that is true. If you install an oversized system it can cool down even more (which answers your store question: they have an oversized system). An oversized system will cool the air too fast and not deal with the humidity correctly. There are other problems with an oversized system as well that someone who knows HVAC better than me can talk about..

⬐ zrail

If you size up a system with variable compressor and fan the system will use the correct amount of power to maintain whatever temp you want. This is more common with inverter compressors, as far as I can tell.

⬐ MisterTea

> There are other problems with an oversized system as well

(Not an expert but I've dealt with HVAC enough) Short cycling is another problem. The system cools the room air faster than the air can absorb heat from the objects in the room and the structure itself. This causes the thermostat to cut out prematurely. The air then quickly warms from absorbing heat causing the thermostat to cycle on. The room again cools too fast and thermostat cuts off. That constant on-off cycling can damage the refrigeration compressor. Plus like you said, the humidity is not controlled so the room is cool and humid which is much less comfortable (to me at least.)

⬐ criddell

Wouldn't variable speed systems alleviate some of the issues with short cycling?

It seems like this is something that automation could help. A variable speed system could learn what the neutral setting is for different indoor-outdoor temperature gradients and cool the space slowly enough to avoid short cycling. But then I dropped out of thermodynamics when I was in school, so I really have no idea what I'm talking about.

Edit: After looking, I think everything is already in place. Our thermostat also measures humidity, so there's no reason it would run the A/C at a level that would make condensation a problem.

⬐ lfowles

One note I remember from my research, variable speed systems are tightly coupled to the thermostat so you may not be able to use an easily automated thermostat. My thermostat shows humidity (Mitsubishi MHK2), but as far as I can tell that doesn't factor into when/how hard the AC runs.

⬐ elil17

I work in HVAC and it is very common for larger buildings. They get huge incentives for shedding load during peak hours. Larger buildings also have more tools at their disposal beyond simply the "thermal inertia" of the building itself:

1. Ice thermal storage. You freeze ice at night and melt it during the day to cool your building. Only used for large buildings - check out Chicago's district cooling for an awesome example.

2. Adiabatic and hybrid cooling towers. These are HVAC equipment that can switch between regular and a "wet mode" where they evaporate water to cool the AC coil and reduce electricity usage.

3. Better automation tools. Building automation systems are fully programmable (e.g., switch schedules when outdoor temperature is past a certain threshold), unlike most programmable thermostats which can run a fixed schedule but not much else.

⬐ a3camero

In Toronto there's a giant cooling system for downtown buildings that uses cold lake water pumped downtown from 83m underwater:https://en.wikipedia.org/wiki/Deep_Lake_Water_Cooling_System. It's being expanded to offer even more cooling with a low carbon footprint.

⬐ elil17

Very cool! Sort of reminds me of seasonal thermal energy storage: https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag...

⬐ evanelias

Knowing very little about HVAC, when I worked in higher education I was surprised to learn that some colleges centralize heating and cooling for their entire campus. For example, Harvard has a chilled water plant which cools 75 buildings: https://www.energyandfacilities.harvard.edu/utilities/chille...

Interesting article from the Crimson (student newspaper) from 1978 about their recent-at-the-time move to computerize the heating and cooling systems: https://www.thecrimson.com/article/1978/1/12/the-great-chill...

Edit: fixed unintentionally humorous typo, whoops

⬐ googlryas

You know Harvard's endowment is getting too big when they go out and buy Ganymede.

⬐ elil17

FYI, when that webpage says "tons" they mean the capacity to freeze a ton of water in one day. So Harvard's CWPs can move enough energy to freeze 20,500 tons of water a day - absolutely humongous!

⬐ hermitdev

I spent nearly a decade working across the street from plant #1 without knowing what it was, it just seemed to be an out of place (for the comparatively tiny building it was on) massive cooling setup. When I needed to think, I'd often stare out the window and watch the cooling towers in the summer. It was kind of hypnotic, specifically all the running water. From the angle I was at, I could see pretty well into the cooling towers from above.

⬐ shagie

I recall watching a program on green construction on KQED and the Federal Building in SF and how it was built.

From Wikipedia:

> The building was designed to be a 'green' building consuming less than half the power of a standard office tower. Utilizing natural light to illuminate 80 percent of the building helped it achieve worldwide recognition as the first Federal Building to be certified under the USGBC's Leadership in Energy and Environmental Design (LEED) criteria. Its southern wall is draped with translucent panels of perforated stainless steel (3 by 8 feet in size), intended to accumulate solar heat and thereby create an upward air flow, which in turn causes cooler air to enter the building through sensor-controlled windows, achieving an air conditioning effect. The result has been criticized as unsatisfactory by employees working in the building, which has received low workplace satisfaction ratings.

And an article on it - https://www.govexec.com/pdfs/green/080108gsa.pdf

There are some neat things they tried there.

Technology Connections on Youtube has a great video series on how heat pumps work, why they're important environmentally and what kind of power cost savings they can bring. The second video is a longer guide for people who want to get a heat pump.

https://youtu.be/MFEHFsO-XSI https://youtu.be/43XKfuptnik

This is not true since the vast majority of electric whole home heating units sold today are heat pumps, which are up to 300% efficient [1]. If the power generation and distribution is 33% or higher efficiency, then a heat pump will outperform a natural gas furnace operating at 100% efficiency.

EDIT - Here's a video that explains it much better than I could, although it's a bit long, this YouTuber is great. [2]

[1] https://tristate.coop/advantages-heat-pumps-energy-efficienc... [2] https://www.youtube.com/watch?v=MFEHFsO-XSI

This video does a great job at considering that aspect: https://youtu.be/MFEHFsO-XSI

Another one of my "came across this in YouTube" things (started with the design of a hurricane lantern) Why Heat Pumps are Immensely Important Right Now - https://youtu.be/MFEHFsO-XSI

The key is the Coefficient of performance https://en.wikipedia.org/wiki/Coefficient_of_performance

Sure they exist. But it's more than just "swap one unit with another" which was the claim above.

Heat pumps are actually pretty efficient, down to low temperatures. Have a look at https://www.youtube.com/playlist?list=PLv0jwu7G_DFVIot1ubOZd... where Alec discusses that.

Around Chicago you can expect to have only a few days in winter where the COP is bad: https://www.youtube.com/watch?v=MFEHFsO-XSI&list=PLv0jwu7G_D...

⬐ jaclaz

Not really, of course it depends, but IF the actual heat diffusion system is compatible (fan-coils or under floor) it can be pretty much "swap one unit with another", at least for single units.

Still, to give you a single datapoint, I just replaced on a unit a small gas heater with a heat pump and it was really a "swap one unit with the other", still a few issues came out:

1) the cost of the unit, even considering that it doubles as air conditioning/refreshing was only affordable because of some government subsidies (think of 6-7,000 Euro compared to 2,000 Euro for a gas heater and 2,500 Euro for a more traditional conditioning unit)

2) for some reasons, the heat pump is much slower in heating, the net result (in my specific case) is that the unit needs to be kept slightly heated on weekends (it is a small shop that closes saturday and sunday) otherwise when it opens on monday it will take forever to reach a suitable temperature.

Besides, from an infrastructure point of view, if many people change from gas to electrical (though gas powered heat pumps do exist, BTW) the local increase of consumption from the grid needs to be taken into account.

Indeed. A recent Technology Connections video was on this topic:

https://www.youtube.com/watch?v=MFEHFsO-XSI

I’m backtracking the debate here so feel free to ignore this.

I just watched the latest Technology Connections video about heat pumps[1] where he talks about the total energy savings in replacing gas stoves with heat pumps to provide residential heating, with total energy savings up to 5 times. This goes to show my previous point about how “[w]e don’t need to replace carbon power 1:1 if we patch up the inefficiencies of our current energy use.”

So to answer your concern that:

> Electrifying railways and other transportation is going to increase electricity usage, not decrease it.

All else being equal, yes. However we are not going to replace the energy consumption 1:1. Electrical railways have the potential to be far more efficient in the energy use. Especially if you consider the potential increase in traction allowing better track usage which will pull super inefficient cars and lorries from the road and onto the tracks.

Also a minor correction:

> So assuming that electricity consumption is going to decrease is a very dubious prospect.

No, I don’t assume that. However I am hopeful that we can easily decrease our total energy consumption as we electrify. Meaning that if we are still pumping gas to put into our newly electrified infrastructure and consumer systems, there is a potential that we need to pump less of it for the same benefits because of how much more efficient these new electrified systems are over the old fossil fuel powered ones.

1: https://www.youtube.com/watch?v=MFEHFsO-XSI

⬐ Manuel_D

Even if heat pumps are more efficient, replacing gas heating with heat pumps (like what much of Germany is going to have to do) is still an increase in electrical load. Similarly with railway. Electric rail engines may be more efficient, but the existing diesel engines are totally unrepresented in current electrical load.

Even if total energy consumption goes down, huge amounts of fossil fuel usage in transportation and industry needs to be electrifed. The fact that they may be more efficient doesn't change the fact that they are totally unrepresented in current electrical energy usage. I stand by my point: decarbonization means our electricity usage is going to grow significantly as existing fuel-based energy is converted to electrical energy input.

⬐ Blackstone4

I’ve looked at ground heat pumps before (not air pumps). However they are a huge capital outlay of £10k-£19k ($13k-$26k).

Both air and ground heat pumps work best for buildings with underfloor heating. Floors cover a much bigger area than radiators so they don’t need to get as hot to provide the same amount of heat.

We’re in a 70 year old building so that doesn’t help.

The savings are minimal maybe £30-£60 a year before the recent gas price increases. You can get grants of £2k per annum for 7 years so you will get money back. However they don’t really save any money unless you think gas prices will remain high. Outside of that you do it to be green.

https://www.which.co.uk/reviews/ground-and-air-source-heat-p...

⬐ g8oz

Air source heat pumps that couple to forced air venting work great as well. The Mitsubishi Zuba line up is an example. Of course better insulation is needed reap any benefits.

⬐ martythemaniak

Good video. I've been thinking about heat pumps a lot lately, namely, is it possible to make geothermal ground loops cheap and not disruptive? I wrote a bit about it here: https://www.greennewdealio.com/heating/robot-mole/

Air source heat pumps really are great and it seems everyone in mild climates should be moving towards them. In fact, what I'm working on right now is trying to figure out the maximum ground loop "budget", beyond which it would be cheaper to run inefficient heat sources (COP of 1) for the small periods of time where air sourced pumps no longer work.

⬐ sokoloff

I looked into air-to-water heat pumps (hard) as I’m planning to replace my boiler this summer.

Even with large cast iron rads, I need 130°F water temp when it’s below about 25°F outside and the air-to-water heat pumps struggle to hit 125°F output water temp there and fall even lower when it gets colder.

⬐ chrislund

They aren’t in all markets but there are heat pumps that use CO2 as the refrigerant that can make quite-high output water temps. They’re often used for domestic hot water. I haven’t looked too deeply in to them but IIRC they have COPs around 3–4. Sanden is one manufacturer, Mitsubishi and their Ecodan line is another.

⬐ beamatronic

The Bay Area has a mild climate but I’ve never seen a heat pump here.

⬐ Tagbert

Probably because in a mild climate even conventional heating systems don’t cost much. There isn’t a lot of pressure to invest more in the system initially just to save only a small amount per month.

⬐ bradknowles

The heat pump has more to do with getting off gas and oil and other hydrocarbons that are burned at the house, and switching all your energy usage over to electricity, which can either be efficiently generated elsewhere, or allow you to go completely off the grid.

Don't do it today to save money today. Do it to save the planet and help ensure that you're not beholden to $9000/hour bills because the people selling you the precious hydrocarbons have you backed into a corner that you cannot possibly dig yourself out of.

You know, so like you can't be screwed by the like of ERCOT when they tell Texans "oh, that sure is a nice grid you've got there. It would be a real shame if it were to be shut down simply because some of the electrical generating plants haven't been properly weatherized. Hmm, I wonder how many of these plants we should take offline on the coldest day of the year????"

⬐ deckiedan

Would it be possible to do multiple vertical shaft tubes, straight down rather than a huge flat thing?

I feel like in 100 years time we'll have all these loopy pipe arrays all over the place being a pain to clean up...

⬐ c22

Yes, this is usually how it's done when a large field doesn't happen to be available. Vertical boreholes are much more expensive to make than shallow trenches, though.

⬐ bradknowles

Depends on what your ground looks like. If it's bedrock at the surface and you'd have to dynamite to clear a large patch, then drilling a small hole will be much less expensive and much more efficient.

If it is just plain brown dirt for miles down, then digging some trenches might be a better solution.

If it's a few feet of sand until you hit the water table, then I have no idea what the best solution is.

⬐ smcleod

As someone who has lived both in New Zealand and Australia where both countries mostly have heat pumps in every house - I'm genuinely surprised to hear that many people in other countries don't all have them. They're relatively cheap to install ($1500-$4000), safe and efficient.

⬐ caminante

What is your energy cost? $/kWh?

If electricity is expensive, the payback period can take longer for residential/commercial applications.

⬐ smcleod

Around 22c/kWh on over over the last month.

⬐ caminante

While not German-levels of electricity prices, that's still 100% more than my elec price in the US and comparatively worse than gas . Retrofitting a heat pump for me is a negative NPV investment.

⬐ yesenadam

> in New Zealand and Australia where both countries mostly have heat pumps in every house

I'm not sure that's right. I've lived in a lot of houses and units in Australia, in city and country, and none have had air conditioners, assuming that's what a "heat pump" is. The houses I've stayed in in NZ didn't have them either.

[After googling what a heat pump is] I didn't know a heat pump is a thing, like an air conditioner but can heat as well. I don't remember ever hearing about them! (I'm 50)

⬐ smcleod

Really! That's interesting. I'm 34, and from memory (which might be a bit rusty) of the 6 houses I've lived in in NZ 4 of them had heat pumps (aka split system aircon), and in Australia I've lived in 4 houses and all of them have had them.

⬐ nicolaslem

Two years ago I moved to a house with only a fireplace for heating. I spent the first winter taking care of the fire, which is nice at the beginning but a real chore after a while.

Before this winter I installed a air to air heat pump. The first thing I learned is that everyone calls that differently, to the point that talking with companies to get one installed was difficult: "-Hello, I'd like a heat pump please. -Sorry, we only do AC.". The name people give to this device really depends on the area.

I went with a single console unit, basically a 1x1m square that hangs inside on a wall close to the floor like a radiator. The installation took a day and costs about 2000€.

On the coldest days of the year when the temperature stays around -15°C, the unit uses about 25kWh of energy for a day to heat the whole house at 19°C. About 15kWh on days when the temperature stays around -5°C.

Before next winter I'm planing on having someone check if there are quick wins regarding insulation, I suspect that some of my windows are pretty terrible.

⬐ 2Gkashmiri

i want to get a ground heat pump, there is common to have a bore well in our area that we can get fresh water out of. i want to know if there is a calculator or something that would tell me if its possible and depths/temperature i can expect out of the system..

i already have 5 kw solar setup and expecting to install 200-300Litre solar water heater but a ground heat pump should be useful in winters when the sun is out and electricity gets out.

currently we have 0 house heating, we only use insulation and personal heaters to warm bodies so if i could have a ground heat pump get the house temperature up, that would be great

⬐ nimbix

If you pair a heat pump with good insulation, the effect can be quite staggering. My parents moved into a new house 6 years ago and their annual heating bill (for space and water) dropped from ~2500EUR down to around 300EUR.

This is in an area where night-time winter temperatures hover in the -5°C range, occasionally dropping to -10.

The old house was around 30 years old, with fairly thin insulation (5 or 7cm was pretty standard back when it was built), and had an oil burning furnace for heating.

⬐ mattiasberge

That can’t be right.

⬐ gorkish

From 2500/yr to 300/yr is 88% reduction in cost.

Heat pumps are 300% - 500% efficient, enough to represent a 66% to 80% savings on their own. Adding insulation reduces the total amount of heating necessary, plus heating oil and electricity aren't priced the same per-unit of energy.

This is not unbelievable in the slightest. Perhaps if you find it surprising, you should ponder where your reasoning got hung up.

⬐ nimbix

Yep, the "magic ingredient" is definitely insulation (along with triple pane windows).