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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."

13 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 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
    3. 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...)

  2. Re:What? by MustardMan · · Score: 1, Insightful

    the efficiency of air conditioning changes with the temperature of the outside air (unless it's something that does heat exchange with the ground, such as a heat pump). therefore, pumping out the same 10k joules in the early morning could indeed cost less energy than pumping it out during the day.

    that being said - I still hate roland pipsqueak blog articles, and wish we had an option to filter them

  3. 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!

  4. 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.

  5. 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.

    --
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  6. 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.

  7. 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
  8. 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.