6 ms·

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 (http

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 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 4y ago
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.
elil17 4y ago
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.
- shagie 4y ago
  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 https://www.govexec.com/pdfs/green/080108gsa.pdf There are some neat things they tried there.
- a3camero 4y ago
  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 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 4y ago
    Very cool! Sort of reminds me of seasonal thermal energy storage: https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storage https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag...
- hermitdev 4y ago
  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.
- evanelias 4y ago
  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/chilled-water 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-chilled-water-bazaar-or/ https://www.thecrimson.com/article/1978/1/12/the-great-chill... Edit: fixed unintentionally humorous typo, whoops
  - googlryas 4y ago
    You know Harvard's endowment is getting too big when they go out and buy Ganymede.
  - elil17 4y ago
    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!
criddell 4y ago
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?
- bluGill 4y ago
  > 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..
  - MisterTea 4y ago
    > 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 4y ago
      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.

lisper 4y ago

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.

elil17 4y ago

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.

shagie 4y ago
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 https://www.govexec.com/pdfs/green/080108gsa.pdf There are some neat things they tried there.
a3camero 4y ago
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 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 4y ago
  Very cool! Sort of reminds me of seasonal thermal energy storage: https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storage https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag...
hermitdev 4y ago
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.
evanelias 4y ago
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/chilled-water 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-chilled-water-bazaar-or/ https://www.thecrimson.com/article/1978/1/12/the-great-chill... Edit: fixed unintentionally humorous typo, whoops
- googlryas 4y ago
  You know Harvard's endowment is getting too big when they go out and buy Ganymede.
- elil17 4y ago
  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!

criddell 4y ago

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?

bluGill 4y ago
> 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..
- MisterTea 4y ago
  > 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 4y ago
    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.