May 17, 2007 11:56 AM PDT

Throwing cold water on energy-hog air conditioners

Throwing cold water on energy-hog air conditioners
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March 20, 2007
Is ice the future of air conditioning?

At least two companies have built systems that store cold water or ice to make air conditioner operation less expensive and energy efficient. They are both commercializing the approach, already done in large-scale systems, in an effort to make ice-powered air conditioners accessible to small businesses and homes.

On Wednesday, Ice Energy announced that it has landed $25 million in funding to further develop and market its products, which are aimed at both commercial and residential customers.

Trinity Thermal Systems on Monday described a similar cold-water storage system during a presentation at the Clean Energy Venture Summit in Austin, Texas.

But rather than have a storage tank in a back yard or on a roof, its IceCycle-branded products store the cold water in underground tanks where temperature is more constant.

The idea behind these thermal storage systems is to run air conditioners at full tilt during the night when the demand--and in many cases, the price--for electricity is lowest.

Standard air conditioners circulate a refrigerant through coils which creates cold air through a heat-exchange process. By cooling the refrigerant with cold water during the hot times of the day, air conditioners do not need to work as hard to cool the air and remove humidity.

The savings from this "peak-shaving" setup can be significant.

The IceCycle line can reduce power consumption by 20 percent by moving up to 95 percent of the workload to off-peak hours, according to Trinity Thermal Systems CEO Mark Glover. The payback for commercial systems can be two and half years, he said.

The company, which is seeking funding, is bringing its products to market this year. There are models for new installations as well as those that are retrofit to existing air conditioning systems.

Ice Energy is focusing marketing of its Ice Bear-branded line mainly to businesses where it says that the payback, with incentives, can be a few years or cash-flow positive for customers that lease.

It is also working on making its residential storage units--which are about the size of a refrigerator--smaller for individual homes. It plans to introduce these smaller units this year.

Green angle
In addition to lowering air conditioning bills, these ice storage products help lighten the load on electricity grids during the times of highest demand--the middle of a hot day. That means these "peak-shaving" products benefit from utility or government energy-efficiency incentives and tax breaks.

Utilities are also introducing more time-of-day pricing to encourage people to consume electricity at night, rather than high-demand hours, said Gary Kaiser, the vice president of strategy and business development at Ice Energy.


"In the past, energy efficiency was viewed the same in daytime or nighttime," he said. "Saving energy is all good but some times are better than others. The best is to save energy at peak times of day."

Time-of-day pricing is common for business customers in the U.S., with about 96 percent of utilities with programs in place, said Kaiser. Only about half of utilities offer this to residential customers, he said.

Many of these programs don't offer dramatically different pricing schemes between peak and off-peak times but that is changing because utilities want small businesses and consumers to contribute to lowering demand, Kaiser said.

Utility incentive
By shifting the load to nighttime, utilities do not need to build additional power plants to address those relatively small windows of maximum demand, typically hot days.

In the territory covered by California utility Pacific Gas & Electric, the highest 25 percent of the utility's total capacity is needed only 10 percent of the time, said Hal LaFlash, director of renewable energy policy and planning at PG&E.

By smoothing out the overall load, utilities can take better advantage of distributed renewable energy power generation "to meet gaps in demand," LaFlash said.

In some areas, output from wind turbines is highest at night and lowest during the middle of the day.

To take advantage of more interest in peak-demand reduction efforts, Ice Energy is trying to get its Ice Bear certified for efficiency incentive programs

On Wednesday it announced that Ice Bear products will be used as part of the Anaheim Public Utilities' Thermal Energy Storage Incentive program.

SI Manufacturing will install five Ice Bear units to cool 14,600 square feet. Because the system is more energy efficient and draws on cleaner sources of power--like wind--at night, Ice Energy estimates that the installation will have the same impact as removing between four and five cars from the road over the next 10 years.

Although air conditioners with thermal storage outfitted for single buildings are relatively rare, large-scale thermal storage systems are in operation at about 5,000 places in the United States, said Trinity Thermal Systems' Glover.

Austin Energy, the municipally owned utility, has installed two thermal towers that are connected by underground pipes, according to a utility executive.

Commercial buildings, including a hotel, in the downtown area can tap into the cold-water storage distribution system.

The utility also installed a single thermal storage tower at the Dell Children's Medical Center in Austin.

See more CNET content tagged:
air conditioner, incentive, storage system, ice, pricing


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Saves money not energy
This will reduce your costs by using energy when it's cheaper. The net result will be more energy used than if the system were not implemented.

Despite decent insulation the system is not 100% efficient so it will actually use more energy than if you just run the AC when it's needed.

It also burns energy at times when solar is not available so it's almost guaranteed to be fossil fuel energy.

If money is the only issue then I supposes it's a clever (although not new) idea.
Posted by smilin:) (889 comments )
Reply Link Flag
Right and wrong
Right that it does save money, and wrong that more energy is used.
It is not difficult to imagine that dumping heat into cool night air
would be more efficient than dumping heat into warm air during
the day. Moving the heat is what uses energy, so as long as the
efficiencies of transfering heat at night outweigh the added costs of
running the system you use less energy overall. The temperature
differential between the heat source and heat sink is important.

Have a nice day!
Posted by lesfilip (496 comments )
Link Flag
cooler temps at night
Actually, it is likely to be more efficient -- take someplace line Walnut Creek, CA where the July daytime max temp is 92 and nighttime min is 65. By running the AC only at night, the condenser runs nearly 30 degrees cooler.

While it's not using Solar power, it can still use other alternative energy sources at night, like wind or hydroelectric. Even if it's using fossil fuels, it's not going to have to tap into relatively inefficient and often dirtier peaker plants.
Posted by sfbiker (147 comments )
Link Flag
It also burns energy at times when solar is not available so it's almost guaranteed to be fossil fuel energy.

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Posted by colala (1 comment )
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Yes it will save energy!
You guys seem to think that all these power generators can be turned off and on like a light switch. Some smaller units can be turned off at night, medium units may be able to go into a "reduced" production mode at night, but large units, such as nuclear generators, may take a day or two to go from being turned on from off, so they run at normal capacity at night. So usually at night when power usage is low, utilities often have to either throw away excess power or try and store them (such as pumping water from the lower side of a hydropower generation dam to the higher side). Excess power generated at night can be used if it can be stored in a form that is economical.
Posted by shawnlin (75 comments )
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Saves energy too
You can use smaller compressor units which take less power to run in the first place when you have a smaller temperature differential between the heat source and the heat sink. Also it doesn't say but the chilled water can be used direct to the A-coil in the duct work to cool the air being sent to the building instead of being used to cool the hot side of the external coils so the compressor doesn't have to run at all for at least part of the cooling day.

The downside as always is the additional complexity which makes it more expensive to install and to maintain.
Posted by extinctone (214 comments )
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Ground Source
Sounds like the old Ground Source Heat Pump. Ground Temps
would hold in the 52 deg or so for the midwest at the elevation
they installed mine. Works great in homes. Sand foundation
makes it impossible to hold/disperse heat. You want good soil.

The Ice theory is interesting, then mix it into what to bring it
back to ice??? If the storage is underground you'll have cool
water NOT ice to pull off for your temp source/exchange. The
exchange unit the copper pipes perspire, and need foam on
them when entering the building before heading to the exhange

The last problem, IF this is the same theory, Ground Source Heat
Pumps are expensive. Cheap to use for AC, and cheap to run for
heat. In cold temp area where I lived we only needed to use the
heater (gas furnace) ONCE on a blistering cold day.
Posted by Travis Ernst (170 comments )
Reply Link Flag
Not Ground Source
Ground source heat sinks progressively lose efficiency over a
period of a few decades as excess heat is dumped into the
ground. This is because the net movement of heat is from the
heat source to the heat sink.

The systems they are describing here are simply timeshifters
whose goal is to move heat around when it is both more efficient
and when energy is cheaper. The goal is not to dump heat
underground but to dissipate it at the most efficient time of
night when it is the coolest.

Have a nice day!
Posted by lesfilip (496 comments )
Link Flag
Umm, I think you need to wikipedia the basics of compression adn decompression...

Cutting to the blunt point, you only need the AIR CONDITIONER, not the heat pump. Heat pump mode pulls warmth from the outside air. You aren't using that here. You aren't boiling the ice water.
Further, from what I understand, there are two types of ice systems. One uses water flowing through the copper pipes (or alternative, uncompressed liquid with good heat transfer properties) which means a compressor isn't needed, simply a low flow pump, which uses about 10watts an hour.
The second system does use a compressor, but like a car it switches on and off.

Another easy way to look at this is how much cooling power these ice chests store, which the last C|Net article said was 5tons. My home AC is 1/2 ton. Thats probably per hour, so 10 hours of cooling stored in ice. Needing a smaller AC unit to freeze ice (like a freezer compressor at 1/10 hp/ton) you are saving quite a bit of energy.

Back to the heat pump efficencies... look up heat pump water heaters ;) 1/10th of energy used (fossil fuel or otherwise) is energy saved period.

Now don't reply with your canned responce.
Posted by timber2005 (720 comments )
Reply Link Flag
Didn't mean to reply to story but to someone spefically...
SOrry, I correctly replied to someone now.
Posted by timber2005 (720 comments )
Link Flag
new style air conditioners don't work
I redid an old Victorian in New Orleans and was told because of
the size of the house and height of the ceilings that I would
need three compressors. By contrast the house I grew up in,
also in hot humid Louisiana, only needed one. The difference,
you ask? The house here is only 1000 square feet bigger yet
the brand new "energy saver" units struggle to keep it below 75
degrees with about 90% humidity inside. I routinely get $400
monthly bills. They have to run all the time. Not very energy
efficient. When I marveled to my mother about how well the one
worked that we had growing up, she told me that the handyman
had gotten it off a trailer, you know like a trailer park trailer.
Apparently those things work better than the fancy
environmentalist politically correct ones that they want to force
on us. Maybe it's just me, but I would rather have something
that works the way it's supposed to. That's sort of like the new
toilets that don't use as much water until you have to flush them
five times in a row to get them to work. Maybe Sheryl Crow
came up with that idea.
Posted by drink more iced tea (1 comment )
Reply Link Flag
Not the ACs fault
It sounds like you were sold a system by someone who failed to size it properly. An undersized system will run continuously and not keep up while an oversize system will run in short spurts (which is also inefficient).

Call out a different company and have them look at your system to see what you can do to correct the problem and do it today so you don't end up spending too much again this summer.
Posted by extinctone (214 comments )
Link Flag
... or sheryl crow's
um... maybe sheryl crow came up with that one? really?

hey, maybe it was jane fonda. or rosie o'donnel. hell, maybe it was oprah that came up with the low-flow toilet.

how am i doing on your list of "uppity biches"? do you feel like enough of a cliche yet?
Posted by muskratboy (349 comments )
Link Flag
Have you had your current home's insulation updated at all? There are probably enough cracks and crevices to add up to the drafts from an open window. Most likely the new AC units are working great, but the house is so horribly inefficient, they just can't keep up.
Posted by skrubol (181 comments )
Reply Link Flag
Not mentioned: efficiency IS greater at night
Ice Bear literature claims that it's actually more efficient to run the AC unit at night. And it makes sense. I mean, is it easier to make ice when the temperature is 70 or when it's 100? The ambient temperature acting on the cooling coils is 20 to 30 degrees lower, so the cooling effect is greater. It's not just a matter of taking advantage of cheaper rates at night. It's a double benefit.

And, the technology is not really radical. Standard refrigeration equipment is used.

I really like the idea and hope that these units are well engineered and reliable. Storing lots of ice on the roof (or where?) will require some thoughtful design work. But the idea is great and I wish I could buy one.
Posted by ArtInvent (374 comments )
Reply Link Flag
The payback period depends on what U have now.
I think cities should start programs with the utilities so when they do their home inspections they also make an energy efficiency checklist.

Adding insulation will save you approx. $/yr and will cost $$
Upgrading your furnace will save approx. $/yr. and will cost $$
Upgrading the refrigerator, A/C, etc.

Then provide a low cost loan program that allows new homeowners to upgrade and pay over time. If it pays for itself in 10 years or less it should be a no brainer. Some utilities have programs like this, Laclede gas offers up to $2000 for insulation. But that should be expanded. If it pays for itself, then you'll also have newer stuff if you ever go to sell the home also.
Posted by stlwest (72 comments )
Reply Link Flag
How Ice Storage Saves Energy
Ice Storage can save up to 14% of energy consumption at a building. The technology?s real benefit is using existing and new generating resources more efficiently. Ice Storage reduces the impact of comfort cooling on the electrical grid by lowering peak electrical demand, which improves electrical system reliability and slows the need for building new power plants and transmission lines. By generating cooling at night and using it the next day during peak electrical demand periods, valuable source energy is saved too because electricity is generated and transported more efficiently at night. One California Energy Commission study says night-time generation saves from 8 - 34% of valuable source energy.

Furthemore, more energy at the building can be saved by rightsizing the Ice Storage system. Routine oversizing of chillers in commercial buildings causes related components to be oversized including condenser pumps and cooling towers and transformers, which will likely never run at full load for the life of the system. Right-sizing chiller capacity is capable of saving lots of energy at the building.

There is an extra step involved by using Storage in a cooling system but the benefit is not just financial. The inclusion of storage decouples the cooling system?s two functions, namely to create and distribute cooling. The benefit is that there is a dramatic reduction of peak demand. And reducing peak demand saves energy at the power source. A number of studies and articles have stated that it is more efficient to generate and distribute power at night than to do so during the day. The main cause of the inefficiency was dirtier, peaking plants.

While off-peak, base-load plants run with heat rates of 7,900 to 8,500 Btu/kW (8335 to 8970 kJ/kW), the existing stock of ?peaking? plants, which are comprised mainly of simple cycle combustion turbine units, are in the range of 9,000 to 12,000 Btu/kW (9495 to 12 660 kJ/kW). By using off-peak energy, the utility should save source energy while supplying the same usable unit of energy to the building.

Some environmental implications of the use of on-peak power are:
? Line losses are less off-peak because that much less power is transmitted at night.
? Spinning reserve requirements are lower. (Spinning reserve essentially means power plants are forced to spin turbines at night, without generating power. So, the plants are ready to help
meet the following day?s peak load). Therefore, lower on-peak power requirements translate into less waste from spinning reserves.
? The building of additional power plants to meet more immediate peak electric needs are avoided.
? Blackouts and brownouts are prevented.

If you wish to consider sustainable energy resources, whether they be Wind or PV or geothermal remember they are cyclic (at best) by nature, very expensive and not yet widely used. If we add clean coal or nuclear the assets are still probably double the installed cost of power plants of the past. And Net Zero buildings do not mean you take nothing from the Grid. It means the average energy taken from and given to the grid is Zero. Having PV or Wind on a building actually makes its Load factors much worse because when the cloud comes by, the PV goes to zero and now all your power instantaneously must now be supplied by the grid. Instantly supplying power is not efficient. Imagine how inefficient life would be if we had to search for food or water each time we we became hungry or thirsty! Water is stored in reservoirs and food in cupboards. Storage is integral to not just AC systems but the world (nature).

Consider, Building and Grid LOAD FACTORS as an important metric in studying reduction of peak demand. (California?s new Title-24 building code has started to address it with Time Dependent Valuation). As you may know Load Factor is the average load of something divided by the peak load. In the US the Load Factor of the Grid Generation is now a little over 50%. What this means is that power plants must be able to meet the highest demand for electricity every time and at any time. A level electric demand or better Load Factor would mean that the highest demand for electricity that a utility will have to meet wouldl be lower. Think about it. We actually have about twice the generation capacity installed as we really need IF we used electricity at a level rate day and night. (This Grid Load Factor is down from about 68% in the late 1950?s, (EPRI numbers)). Building load factors can go from the 50's to possibly the low 80's with the addition of Energy Storage (Electric Energy Storage is expensive however Thermal Energy Storage (Ice) for Air-Conditioning is not.) And it was AC that caused our Grids Load Factors to change so much in the first place.

Ice Storage is a powerful means of shifting kWh from on-peak to off-peak. This saves energy at the power source and at the building. Oh yeah, and it saves a lot of cooling costs but that?s another thread?!
Posted by theIceQueen (1 comment )
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