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High-performance-home designer Michael Maines takes a detailed look at the new low-carbon edition of the grassroots building standard.
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"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
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you buy one if it works i'll buy one!!! i hate being on the cutting edge,it bites me every time larry
hand me the chainsaw, i need to trim the casing just a hair.
It would use slightly more energy to make and "store the cold" than an air conditioner making it as needed would. Therefore, it only makes sense if the "cold" could be made more cheaply at night. That would depend on how much less you pay for electricity at night.
Even in the absence of cheaper power at night, it could be more efficient since the cooling cycle occurs when the air temperature is a lot cooler. It would depend on area of the country, and the temperature differential from day to night.
John
Good point. I hadn't thought of that.
back in 1986 era, we built this bldg at the local gayfers, It was about 40 foot tall with no doors , window or floors. what it was, there was a huge high machine on the roof, and made ice at night dropping in to the hollow bldg. During the day, they blew air across the ice making hvac.
If you have time based demand charges for power then they make sense. Probably no payback for residential.
Not really new in commercial.
There are systems where they actually freeze water in the winter and then use it during cooling season.
Like the others have recognized, it has been around for 25 years or so, in the large commercial versions.
Most residential rate structures for electrical power include either a simple flat rate, a graduated rate all the time or a graduated rate in non-cooling season only. I have never seen or heard of a residential electrical service with a demand charge. The benefit of thermal storage without reduction electricity demand charges are minimal.
The primary benefit of thermal storage is in what is known as "load shifting". That is moving some or all of your cooling energy usage from peak (3-5 pm) to off-peak. In a facility that has office hours, or two shifts, at night when there otherwise no load, you run your chiller plant to freeze a large, very well insulated tank of water when the lower OAT alloes your chiller to run more efficiently and your process loads are minimal. Then, when cooling i required, you utilize the "stored cold" to meet some or all of your cooling needs. Depending on the size of the plant and the rate structure, overall energy expended for comfort cooling can see 25 to 50% reductions. In some cases you can buy smaller chillers upfront, use the ice storage to pickup the slack in high load times.
Unless you pay significantly more for electricity during peak hours (i.e 8 am to 6 pm, M-F) this is not worth the trouble or expense in a residence. The reduced "interruptable" rates available in some locations might be worth it with a device like this, pending some number crunching.
In the NW I have heard that have special residential rates for thermostorage for heating units. Don't know if they have will do anything for AC or not.And an electrican that I knew back in MD had, IIRC, a 3 or 4 step rate. Very, very cheap overnight (10pm - 6 am or something like that). More exepensive during the day and very expensive during the peak afternoon/early evening. I think that at the lowest it was less than 3 cents at the lowest and 15 to 20 at the highest.Don't know how that varied, if any, seasonally.
blowing air over ice makes the air cooler but its still humid
Actually, ice should remove humidity about as well as a regular AC. It simply depends on how cold the air gets at its coldest. And I suspect that many of these systems use a heat-exchanger scheme where the air doesn't pass directly over the ice anyway.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
The air is still passed through an evaporator coil, operating as it would without the device (according to their claims).
With variable rate structures in residential electrical supply, this could be a very big seller/saver.
I know how the systems work in a chilled water system. Would be curious to see how this is implemented in a direct expansion system.
I think Trane, York , and Carrier are in that market now.
We use to use a variance of the system for the very reasons you have stated. We had a large chilled water storeage tank, 20,000 gal. IIRC. We used a single 75 ton York chiller most of the time to maintain the chilled water in the loop and tank at 40 degrees. When the load exceeded the capacity of the first chiller, a second 75 ton chiller would come on. Durring the hottest dog days of summer we seldom ever ran both chillers more than 50% of time durring peak loads.
Took those old centrifical out about 4 years ago and put in two 125 ton screws from Trane, and eliminated the chilled water storage tank. We later had to add a three stage 50 ton scroll (air cooled condenser) as a back up and night time energy saver.
Trane can sell snow in Alaska :)
We use to be able to change out a cooling tower motor, fan blade, pulley shives, bearings and shaft durring the hottest part of the summer and the building would never know the system was down for repair. As long as the chilled water pumps and AHU were running, the building temp was maintained by our stored chilled water.
Not so now. If something goes south on us, we're lucky is we don't have com. and computer systems shutting down by the time our "on call" tech and the Trane tech. arrived on site.
But, we have the Trane Summit Sytem controls, and their system is so reliable that we don't have those problems any more....... :(
There is a lot to be said for the old stored cooling systems, but not a lot of money to be made.
Dave
One thing to note in a system that uses the stored "cold" to meet partial load, is that if it is not fully operational, then you're short of cooling capacity.
I have never had to opportunity to design a thermal storage chilled water system from scratch, but I did do a study/analysis of of building that had one. This was a Baltimore Air Coil storage tank and cooling tower system, with two 50 ton Carrier chillers. The design cooling load for the building, based on my calculations, was 125 tons. One quadrant of the four coil storage tank had failed and been isolated. Regardless of the load, they could never get chilled water out of less that 50 degrees, and were thinking of scraping the thing and going with g/e rtu's. With the tank restored, we regularly saw 40 degree CWS, never had trouble providing 45 degF CWS under design conditions and everyone was happy, cool and dry. Saved them a lot of wasted money for the initial work and every summer thereafter. The electric utility in this area charges a stiff premium for peak demand, so here, it really makes sense with a commercial chilled water system.
The facility I work in was originaly a Sears store most likely built in the early 50s'. I don't think that it was one of the building that use aquifier or artisian well water in our downtown area, but it was one of the first air conditioned retale stores around. The chilled water storage tank was original to the building. We upgraded the chillers, piping and AHUs to support an office facility when we purchased and renovated the property in the early 80s.
The old York chillers, Johnson Control combination worked great for over 20+ years. York and Johnson Control gave us great support and kept a close watch on their maintenace contracts.
Trane got the maintenance contract in the mid 90s, andthe shift to all Trane systems followed over the next sevral years. One of the Trane design engineers even told he though the storecooling capacity was a great design buffer, but could not leave it in their design proposal.
No point in beating a dead horse, but from a maintenance techs point of view, it sure was nice to have that storage buffer there when poop happened.
Dave
"The facility I work in was originaly a Sears store most likely built in the early 50s'. "I thought that it was much older than that.My mother used to say how my father would take her there to look at tools on 'dates'.That would put it back in the late 30's.But it might have been a different store, but she would mention it when we went to that store.
Yeah, Sears tended to build fairly modern looking buildings, and one built in the 30s could likely pass for being 50s era.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Might be Bill.
I'll ask the former renovation project manager if he knows.
The old automotive center is now our Annex. Mostly meter readers and gas dept. contractors out there. It has some unique features in the basement. Old pads for hydrulic lifts, elevators for parts and tire movement, some strange ejection pumps with drip oilers on it, and an anceint old chiller.
Dave