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Saving Energy in Small Office Buildings
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."
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.
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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?
HOW THE BIG GUYS DO IT. I used to work at JCPenney headquarters in Plano TX. They built their HQ back about 14 years ago. At night they chill a series of water tanks using low rate kilowatts. Then during the day that chilled water is used for HVAC. Of course heating can be done the same way. ITS A DUSTY PLANET. If this company has done it, then most likely an amazing number of recent office buildings have done it. NOT NOTICING? And like others, I have considerable reservations about 'not even noticing' a cooler temperature in the morning. In the controlled environment at JCP they certainly turned OFF AC in the evenings and weekends. Yep I noticed that. Same thing in reverse in winter. JUST A GRAD PAPER? Seems to me to be yet another graduate research project unleashed on an unwanting world. A better approach would be to somehow retrofit those 'package' HVAC units to chill a different mass such as an external tank.
-Fyodor
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...shade awnings. They work well, and were very common back in the olden days before cheap electricity made cheap air conditioning possible. Now that this is changing, it might be prudent to relook at old solid tech that worked.. In the summer most of the day the sun is high overhead, high enough so that the awnings make the window shady, hence, little direct thermal gain. In the winter, the sun is lower, it comes in under the awning, you get solar thermal gain then, which you want then. The other nifty advantage is you can use your windows. Passive heated solar houses work this way, the south side of the house has a steep overhang and is mostly glassed in. Winter=warmer, summer in the shade= cooler. Works great, no moving parts and less "bunker" closed in no windows claustrophobia action.
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.
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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
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.
the condensing outdoor unit standing in the burning ... ...
mid-day sun and don't you just love the outdoor
consing unit standing like 1 inch from the wall, when
acctually positining it 90 degrees to the wall would
give much better airflow and on a windy day even
near "free" condensing? tsh-tsh-tsh
and maybe you have noticed that really cold drinkable
water coming from the indoor unit? well why not
just let THAT flow over the cooling ribs of the
outdoor condensing unit? nevermind then