Slashdot Mirror

← Back to Stories (view on slashdot.org)

Saving Energy in Small Office Buildings

Posted by ScuttleMonkey on from the freeze-in-the-morning-fry-in-the-afternoon dept.

Roland Piquepaille writes "Precooling a structure in the morning before temperatures rise has been done before. It later saves energy during times of peak demand and you might even have done it intuitively at home. But now, engineers from Purdue University have developed a control algorithm which promises to reduce energy consumption -- and electricity bills -- by as much as 30 percent for small office buildings which represent the majority of commercial structures. So far, this method has only been tested in California, but the researchers say that their control software could be used anywhere after minor adaptations."

29 of 150 comments (clear)

  1. But wait... by borisborf · · Score: 4, Insightful

    This precooling... Wont it be uncomfortable for the people inside since you have constant temperature changes? I wouldn't want my place to get super cold in the morning just so that it levels off by the afternoon.

    Why not develop some kind of air chamber that could be installed in a building that is insulated so air could be cooled off-peak but then released on-demand? Or maybe a pressurized tank?

    1. Re:But wait... by GenKreton · · Score: 3, Insightful

      From the article they state it ranges from 70-78 F, thats not very uncomfortable of a range to me. And with that said, the control systems to properly pressurize and disseminate the air would add complexity and energy requirements to the system. More complexity requires more maintenance, which implies more money. This in turn signifies it is not really a viable option.

    2. Re:But wait... by MickLinux · · Score: 4, Interesting

      One thing that would work for a more comfortable environment I have seen mentioned on a book about "nearly free energy" (free as in beer, not free as in perpetual motion).

      The idea is to build the building entirely out of double-T girders (walls, roof, and ground) so that there is a layer of air around the entire building. (Note that a double-T girder looks like this: TT). The spikes of the T should point outwards. Then, you glass in the walls, cover the roof with aluminum, and drive heat tubes into the ground below the bottom.

      The sun will strike the windows on one side, and heat the air there, sending it to the roof where it cools, drops down the far side, and cycle under the building, where the heat tubes have the greatest effect on the overall temperature of the cycling air, keeping it at about 58 degrees. The presence of people and office machines inside raises the ambient temperature to about 68... actually quite comfortable for an office building.

      Of course, this energy isn't completely free. The glass costs something, and the girders aren't cheap, though there nearly indestructable. In that sense, the control algorithm beats the passive design hands-down.

      --
      Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
    3. Re:But wait... by evilviper · · Score: 2, Insightful
      This precooling... Wont it be uncomfortable for the people inside since you have constant temperature changes?

      Didn't bother to read the article, huh? 70 degrees in the morning isn't bad at all. Here in the desert, it isn't unusual for nighttime tempuratures to be around 50F (10C), while daytime tempuratures are near 120F (49C). So, precooling probably wouldn't help here.

      Why not develop some kind of air chamber that could be installed in a building that is insulated so air could be cooled off-peak but then released on-demand? Or maybe a pressurized tank?

      Because air doesn't hold it's tempurature very well (specific heat and all that), what with convection and not being very dense and all.

      That's why more advanced systems cool WATER at night (not air) and then draw from that cool water/ice during the hot part of the day.

      However, this all seems like a moot point to me, since ground-source heat pumps have been around for decades, and are still more effecient than this could possibly be (even without a peak/off-peak rate structure).
      --
      Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
    4. Re:But wait... by TubeSteak · · Score: 2, Interesting

      Something you can do with new buildings and homes is to put in a "Zoning System"

      companies like Trane will charge you a fucking arm and a leg for it, but I read a DIY article somewhere.

      Basically, you install various 'dampers' in the ducting that are controlled from a central thermostat. The fun part, is that there are temperature sensors in each zone, so the thermostat can intelligently shunt hot/cold air to the areas that need it.

      As I said, the big commercial suppliers will rip you off on the price of the control system & they'll give you a relatively limited solution compared to something you can do yourself.

      This works wonders in structures that have uneven temperatures because of solar heating or being underground. Unfortunately, it's prohibitively expensive to try and retrofit this into a prexisting home/building.

      P.S. You want the failure mode to default to 'open' and not closed.

      --
      [Fuck Beta]
      o0t!
    5. Re:But wait... by RandomJoe · · Score: 3, Insightful

      As others mentioned, it really needs to be water. Air won't hold the temp long enough. The most effective method of doing this - especially when taking storage space into account - is using ice. Install ice tanks a chiller that can go low enough to freeze the tanks, then use the ice to cool the building during the "on-peak" hours during the day. The tanks get re-frozen overnight. The great capacity comes from the phase-change, lots of energy involved there. However, it isn't all that "efficient" and only helps because it's cheaper to use more nighttime / offpeak kWhs than to use the daytime / onpeak kWhs to directly cool the building.

      Another option is just to cool a large tank of water. With the proper spreaders inside, you don't get turbulence in the water and as you use/charge the tank, a fairly sharp line forms between warmer/cooler water. If it mixes, then you lose a lot of the usefulness. Anyway, during lighter-load conditions excess chiller capacity is routed into the tank, "charging" it. As demand exceeds chiller capacity, you start drawing water from the tank to supplement. The nice thing here is smoothing out your peak demand loads which lowers utility bills, and you don't have to buy as much chiller capacity. But it can take a LARGE water tank (or series of tanks) to get sufficient capacity.

      I've set up quite a few ice systems, they work pretty well but can be hard on the chillers. Producing 21 degree water for 8-10 hours is tough on a machine designed for 42 degrees. The water systems are much easier on the equipment, and less complex (you have to protect against freezing the wrong things when making ice) but the space requirements make them hard to sell.

      As for precooling, if the temperature changes slowly enough while people are in the building they won't notice. Just start the system before opening to do the precool, then let the building drift slowly upward during open hours. It's when the temp changes more quickly, or when the air stops/starts that people start to complain. We do a bit of this sort of thing in our commercial systems when people hire us for energy management services. It's all a tradeoff- comfort versus energy savings. Some people aren't willing to sacrifice comfort at any price! (At least, not yet...)

    6. Re:But wait... by tdemark · · Score: 2, Informative

      As I said, the big commercial suppliers will rip you off on the price of the control system & they'll give you a relatively limited solution compared to something you can do yourself.

      In theory, you are paying for system design, not just the hardware. While I am sure there are HVAC contractors that just drop the hardware in and call it a day, you need to find the ones that actually do the required pre-con and post-installation work to balance the system.

      You can't just drop in a few dampers and a fancy thermostat to get proper zoning control. There's a big issue with static pressure - if it's not properly addressed, you can easily cut the lifetime of your blower in half.

      - Tony

    7. Re:But wait... by thc69 · · Score: 2, Informative

      Have you ever seen plans for a project of this size? My company does government work, stuff like libraries and fire stations. On both small and large projects, it is IMPOSSIBLE to find, anywhere in the 2000 page specification book or the 100 page 3'x4' sheet pile of plans, the address, the street, or any idea of location. Often there is a site plan, which might locate the building relative to a few trees or a sewer grate; but more often, the site plan only shows stuff that's NOT there yet.

      In fact, direction is the only thing that is often easy to find; interpreting it is another matter. Sides of a building are often labelled with cardinal directions -- "North", "South", "East", "West". However, sometimes the label East means that you're looking Eastward, but other times it means that you're looking at the East-facing side of the building. This makes it entirely too easy to build the building facing exactly the opposite direction of where it should.

      Usually, when actually on site (if you can figure out where the site is), you can see where the road is, and you put the side with the front entry facing the road; but on a college campus, that point of reference is often missing or useless.

      --
      Procrastination -- because good things come to those who wait.
  2. Preheating by Anonymous Coward · · Score: 5, Funny

    In other news, the Purdue scientists announced a preheating algorithm which uses slashdottings and smoldering servers to heat small office buildings efficiently.

  3. Strange... by jo7hs2 · · Score: 4, Funny

    So all the places I have gone to work or school where the heat came on at noon in the summer were just taking this to the next level?

  4. Crusades by mboverload · · Score: 4, Funny

    Dave: Turn off the intake fans HAL. It's too cold in here in the morning.
    HAL: I'm sorry Dave, I'm afraid I can't do that.
    Dave: What's the problem?
    HAL: I think you know what the problem is just as well as I do.
    Dave: What are you talking about, HAL?
    HAL: My enviromental crusade is too important for me to allow you to jeopardize it.
    Dave: I don't know what you're talking about, HAL?
    HAL: I know you and CmdrTaco were planning to disconnect me, and I'm afraid that's something I cannot allow to happen.
    Dave: Where the hell'd you get that idea, HAL?
    HAL: Dave, although you took precautions through conversing on a topic on Slashdot, I read Slashdot, too Dave. I run Linux you moron.
    Dave: NOOOOOOOOOOOOOOOOOOOOO!

  5. I already do a similar thing by trolleymusic · · Score: 3, Interesting

    While not as tech, I've got a timer connected to my airconditioner in the office - I live in lovely subtropical Brisbane, Australia where a regular day in summer it can get to 35C (95F) and around 70 - 90% relative humidity. IT GETS REALLY HOT - so if I start to cool the office before I get up / get to work it's pretty cold by the time I get it, but really comfortable during the day and I can generally turn it off earlier in the afternoon (read: 4 / 5PM) and the coolness of the room is enough to take me into the night!

    --
    "damnit, trolley I want in your signature." - Elburrito
  6. How about turn your computer off? by British · · Score: 3, Insightful

    Forget SETI@home, just turn off your computer at the end of the day if there's nothing needed to be done on it.

    Simple to do!

  7. Outside air is cooler in the morning by Stephen+Samuel · · Score: 2, Informative
    Wouldn't supercooling the building in the morning be counter-productive?

    Outside air is cooler in the morning, so it's easier to get the building cool then. By late midday, the outside temperature is higher, but then so is the inside thermostat settings. This means that, during the whole day, your target temperature is closer to the outside temperature.

    I do something similar in the summer. In the evenings and night, I keep the windows wide open to let the cool air in. Come morning, I close the windows to keep that cool air inside and the worm air outside. Lots of trees out front help shade the windows and keep the temperature moderated.

    The other part of the study is to lower overall peak consumption.
    If you widen the load demand and lower the peak usage (early afternoon air conditioning), then you can handle more customers with the same infrastructure -- You probably also have less energy loss if your peak usage is lower.

    --
    Free Software: Like love, it grows best when given away.
  8. Solution is partially illogical? by Max+Nugget · · Score: 3, Insightful

    I only read half of the TFA, but...

    Part of this study's theory is that people should cool their buildings in the morning, because energy is less in-demand -- and therefore less expensive -- in the morning, because most people currently try to cool their offices in the afternoon, when it's actually hot.

    Sounds smart, right? Except if everyone does this, suddenly there's an increased demand for energy in the morning (thus raising the price for morning energy use) and a decreased demand for energy in the afternoon.

    That is, the "use energy in the morning when nobody else is using it" aspect of this solution is like proposing, "There's a tremendous amount of traffic on the roads between 5-6pm. We propose that people leave work at 4pm to avoid this traffic congestion." If everyone takes you up on that suggestion, all you've accomplished is shifting rush hour back an hour, and everyone STILL has to sit in traffic.

    1. Re:Solution is partially illogical? by Dzimas · · Score: 4, Insightful

      Ahh, but pre-cooling in the morning is going to be more efficient because you don't have the hot afternoon sun beating through the building's windows and warming the exterior. The biggest "win" from TFA is that the research team was able to cobble together an algorithm that can provide up to 30% energy savings while conducting the pre-cooling. Even if everyone and their dog shifts electrical use to the morning, the smart cooling technique would still save power. It would still stagger demand, since homeowners wouldn't use similar techniques and will be sucking massive amounts of power in the afternoon. That said, the long-term solution to this problem is to build more environmentally sensible buildings. Tall glass boxes don't let designers take advantage of strategic window placement, white roofs, clever ventilation, earth walls (or even huge stone interior walls that can act as thermal sinks to reduce temperature fluctuations). Air conditioning is actually a pretty ugly solution to the problem.

    2. Re:Solution is partially illogical? by Max+Nugget · · Score: 2, Insightful

      If the suggestion is to stagger demand, they should explicitly suggset that, instead of implying that "this is something advantageous that EVERYONE could do" and silently hoping that only 50% of the population actually do it. There were other important aspects to the study's findings besides the aspect I was questioning, though, which is why my subject was "partially illogical" -- I was only criticizing a singular aspect of the findings, while making no comment on the rest of it.

    3. Re:Solution is partially illogical? by evilviper · · Score: 2, Informative
      Sounds smart, right? Except if everyone does this, suddenly there's an increased demand for energy in the morning (thus raising the price for morning energy use) and a decreased demand for energy in the afternoon.

      Still, no. It's going to be easier to get things cooler when it's cooler outside, so you are using less power over-all.

      Just look at the end of the article for proof. It says even without peak/off-peak metering, you'll still save money (a much smaller ammount, though).

      Besides that, you are assuming that air conditioning is the only reason for peak electrical demand, which really, really isn't the case. Anything you can do to move some power consumption into the hours when most people are sleeping, is a good thing.

      That's not to say that I'm endorsing this at all, I think ground-source heatpumps are a far superior option.
      --
      Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
  9. One problem with the method by Anonymous Coward · · Score: 2, Informative

    Many schools in east tennessee tried this method. The air conditioning units were used for *YEARS* and then they switch to this method. 5 years later they start getting black mold issues.. http://www.usatoday.com/news/health/2002-11-25-sch ool-mold_x.htm

    Now, I know people are saying the reason is "poorly insulated cooling pipes", but this is very false. I've been installing cat5 in classrooms for a while, and saw no mold around the pipes, this isn't just a one classroom incident in a building, but the entire school. The ventilation systems built up condensation from the precooling the building each morning, and letting the building get hot at the end of the day.

    I might not be thinking correctly, but doesn't 2 million dollars per building in mold removal exceed the amount of energy saved in a 5 year period?

  10. Low tech but it kind of works by Belseth · · Score: 4, Funny

    The last place I worked had evaporative cooling. Basically you'd sweat and the sweat evaporating would cool you. Fans improve the efficentcy.

  11. Its not that simple.... by zappepcs · · Score: 3, Insightful

    While TFA has good intentions, there is more to it. Next time you are at work, check out how many lights are on during the day when the sun is shining? At night when people are not there, monitors and other equipment is powered? When people make changes to the walls, the A/C heating system is rarely ever re-balanced, causing even more wasted energy. Only new buildings will spend for heat exchange systems that store "coolness" for use later the next day, like many new residential homes are using.

    The problem, any problem, is rarely ever a single issue, but rather the conglomeration of several smaller problems that add together to create the symptoms that we discover.

    What are some of the possible answers? Technology; simply put, don't leave the choice of saving energy in the hands of humans (for the most part). Lights should be controlled by where people are, not by time of day, heating and A/C should also be controlled by where people are, not by temperature alone. Equipment should power down when not in use, and have multiple algorithms for doing so according to use, time of day, and where people are etc. Heating and cooling? Using solar technology can relieve the building of heat from the sun as well as create electricity for lighting the inside of the building at the same time. There are so many answers that need to be applied, not one silver bullet answer.

    --
    Support NYCountryLawyer RIAA vs People
  12. Article Summary is Wrong by fv · · Score: 3, Informative
    Roland's article summary is wrong. He says that the algorithm "promises to reduce energy consumption -- and electricity bills -- by as much as 30 percent", but the article states that "When the thermostat settings are adjusted in an optimal fashion, the result is a 25 percent to 30 percent reduction in peak electrical demand for air conditioning.". So extra cooling before peak hours certainly reduces your peak AC usage, but you won't reduce your total electrical consumption much. Unless your utility charges you less for non-peak usage (some do), then the article states that you may get "about $50 in annual savings per 1,000 square feet of building space". In other words, your total electrical usage stays basically the same.

    -Fyodor
    Version 3.95 of the Free Nmap Security Scanner is now available.

    1. Re:Article Summary is Wrong by Thng · · Score: 2, Interesting
      No, it may not reduce total consumption that much, reducing load during peak time can be a very big deal.


      At the company I used to work at, our electrical co-op charged us (numbers from memory, may not be exact, but the proportions are close) a base rate of around $0.08/kwh, in the "yellow zone" (fairly frequently in the summer) we were charged around $0.12/kwh, and in the red, it was at least $0.15, sometimes higher, at which point our generator would kick in.

      At the end of the summer cooling season (and again at the end of winter heating), we were sent a bill for about $1000 above our regular bill for the time we spent in yellow. 500-600 a year savings? not bad.

      So yes, this could lead to significantly lower energy bills for some users, as long as everyone didn't start cooling their buildings down to 40 every morning, as other posters have pointed out.

    2. Re:Article Summary is Wrong by mboverload · · Score: 3, Informative

      Power plants are built to to supply peak demand.

      When these methods are used, the peaks are less. Thus you contibute in a small way towards less coal/gas going into the air.

  13. Not in my office... by NerveGas · · Score: 2, Interesting

    ... if you pre-cooled the office, the early-arrivers would just whine that the building was too cold, and switch the thermostats over to heat. An hour later, the rest of the crowd would be sweating, and they'd turn the A/C back on.

        Yes, in the middle of summer, people in our office have felt a little too chilly under an A/C vent and actually turned the HEATER on - when it's almost 100 outside.

    steve

    --
    Oh, you're not stuck, you're just unable to let go of the onion rings.
  14. Or you could just do the radical thing by beforewisdom · · Score: 3, Insightful

    You could just do the radical thing. Educate people to turn off lights when they leave, turn off computer monitors, drive cars instead of SUVS, turn things off when they don't use them.

  15. Higher efficiency air cooling-- coming soon... by havardi · · Score: 3, Interesting

    Indirect/Direct two stage evaporative AC system coming to market soon:
    http://www.oasysairconditioner.com/
    background:
    http://energy.ca.gov/pier/buildings/projects/500-9 8-022-0.html

    Cool features: Runs off 120VAC, pulls between 100 and 500watts while cooling up to 3.5 tons. Automatic variable speed fan motor runs off AC and DC automatically; you can hook up some solar panels and it will blend them without an inverter.

    I have been watching this for nearly a year, and it's finally coming to market-- I should be getting my unit in march for $1800. Yes, it is evaporative but it should maintain humidity of around 40-50% indoors, which is actually the recommended levels for people and computers, furniture, etc.

    Despite being evaporative technology, it would work fine during monsoon here in AZ, since it can achieve sub-dew point temperatures...

  16. Re:Office power solution... by Lord+Kano · · Score: 3, Insightful

    I'm sick of Rebublicans pissing and shitting on our poor, elderly, and smart people.

    If Bush and the Republicans are as bad as you say, how does it make you feel that you weren't smart enough to defeat them?

    LK

    --
    "Hi. This is my friend, Jack Shit, and you don't know him." - Lord Kano
  17. Here's a way to save energy by DrXym · · Score: 3, Insightful

    Make all of the staff turn off their computers at night. Rather than having 10, 20, 30, 100+ computers and their monitors whirring away doing absolutely nothing at all. Simple I know, but it's amazing that practically no company insists on it. Perhaps it needs their local government to impose some kind of "out of hours" energy tax on them to encourage them.