Comments on: Ice-powered air-conditioner could cut costs

Ice Energy says energy-storage system cuts down on the power required for air conditioning by 30 percent.
Photo: Ice-cold air

Nice, but not new

I work at a local community college that has a campus-wide cooling system that is cooled by ice formed in chillers at night. It has been in place for years.

Still, I agree it makes terrific sense from an energy-efficiency and cost savings standpoint.

[bigduke]

Ice to store energy

A couple decades back I read about a mine in Canada that had a heat problem in both winter and summer. Summer it had to pump in really huge volumes of cool air to keep work areas tolerably cool, and in winter minus forty air was way too cold. Cure was to warm the winter air with water spray that froze. It was stored in a really huge cavity and when the weather changed the same fans pumped in warm air that melted ice and reached the working areas at a usable temperature. By cold weather most of the ice was gone and the freezing started again.

It helps that a really large amount of water was available. Note that the heat capacity of water is small compared to the heat required in freezing phase change.

My recall is that the cavern where the ice formed was something like a quarter mile long and quite wide and deep. This is not for everone, but it made a huge difference in the mine for a relativly small cost compared to cooling or heating by fuel driven air conditioners.

My thought is making ice in the volume of a small fridge seems to be not enough storage volume. My AC it 3 tons. Three tons of ice is a big block Water liquid is about 62.4 lbs per cubic foot So ten cubic feet (a small fridge) is 624 lbs liquid. After freezing it is less dense and same volume is mow about 56 pounds per cubic foot of ice. That is a quarter of a ton more or less. Three tons of my AC would take twelve of these units. Doesn't seem too workabe to me. My floor won't take that load, but the basement could.

I do my house differntly. At midnight the AC is turned on to cool the entire house to 78 F from the set point for rest of day of 84 F. This uses power at lowest demand time, and the AC does not come on in most summer weather until after noon. I know it is peak power demand time, but it misses the AM ramp up. We also use gas discharge lights that take a quarter or less of the power of hot filament bulbs. And they are off if not needed.


duke

[pietrodelai]

Already in use

For more than decade, Malls and Shopping Centers in southern Brazil are using this. Ice is made during off-peak hours, reducing energy (peak) costs and improving thermal efficiency. On top of that, integrated "intelligent buildings" activates the right combination of compressors and freezing devices that giving best efficiency for that particular thermal condition. It also considers the cars/crowd flow (enter/exit) to antecipate the heating demand, again, for better overall efficiency.

[jrpettit]

Commercial yes, residential probably not

As was noted, commercial businesses have been using thermal storage for years. The advantage that they have is that peak charges are more during the day (or they have some other type of variable rate). For a residential user, rates are normally flat and do not change based on what time of day the power is consumed.

[RichHorst]

Residential TOU - becoming popular

More utilities are again talking about offering a residential time-of-use rate, in fact many do. These were starting to be expored a few years ago, then became unpopular again.

An ice cooler is currently being used in Californina in the Sacramento area and a TOU rate allows the equipment to make ice at night, then chill with it during the daytime. These systems are not currently in production anymore, but obviously the concept has been around a while. It may need some more development to perfect the technology and affordability for residential use.

[truks]

Residential yes

When making ice or cooling a house, the process is generally the same.

The difference comes in the fact that it is usually cooler at night and using the heat exchange process to make things cool is more efficient when the ambient temperature is cooler - there is simply less of a thermal difference to overcome.

The ice is a simple thermal battery to allow the cooling process to happen at a time when less electricity is needed to do the same job.

Peak/offpeak charge differences would add to the savings, but the savings are still there without them.

[jallegro]

Off-peak Rates

My electric coop offers off peak rates and other programs like a/c cycling. I run my garage heat and basement heat on an off peak METER which is billed at roughly 60% of regular rates. They regulate use and consumption with some sort of timer and it is available from 9 pm to 7 am automatically. Saves me a decent amount every month in the winter.

So... some electric companies do offer it to residential companies.

[Red Rat2]

Off-peak rates

Here in the Pacific Northwest of the US, my power company offered off peak rates, it then stopped doing this. They said it was withdrawn because people were not using it. I suspect that the real reason was that too many WERE using it and the company lost revenue--they are a privately held company. More than likely the petro industry put pressure on them I suppose, but who knows. All of these suggested schemes presented in this thread would certainly help to reduce demand during peak hours.

[bigduke]

Off peak residential rates

That your coop has variable rates is becaues you and others are the owners. Not so for the billion dollar plus outfits that feed my meter.

I'm sure that the order of generation for the big companies is soemething like this: full load on Nuke stations, then coal generation, then oil, then peak loads from natural gas turbins. If they are lucky enough to have hydro power, it would be fitted in to maximize income. Pumped storage woud be recharged during off peak and weekends when industial loads are off line.

Some used to have discounts if you were willing to have a remote signal disconect the AC for short periods of peak demand. Idea was to avoid blackouts.

[sctang73]

when I was dirt poor...

I put a bucket of ice in front of a fan. Same concept, except much more high tech...

=P

This sounds like...

This sounds like a good old fashioned swamp cooler!

A big ol' block of ice and a fan!

[dmm]

not the same

A swamp cooler blows hot, dry air over water. The evaporation of the water cools the air. This also raises the relative humidity, which makes the air seem less cold to people, so it actually would NOT be good in a swamp. But it works well in desert areas.

[pvalenta]

Off peak rates will continue to develop as utilities are viewing current assets that are only utilitzed 50% as a resource. Utilizing existing assets is faster AND cheaper than building new power plants. Having said that cooling requirements that are NOT 24/7 will utilize this technology first. Commercial buildings including offices, K-12 schools, community colleges and universities and retail to name a few. Residential units typically require cooling 24 hours a day which means cooling is required when the ice tank is charging. That requirement adds equipment cost which must be subsided by a huge rate differential between night and day, through utility rebates - OR Both. Look at this link for a commercial application of ice storage. http://kdka.com/video/?id=43916%40kdka.dayport.com

[dennisrader1945]

We have a newly constructed building in Southern California with Ice Bear units. They are absolutely terrible. Right now it is 88f degrees in our shop and across the hall way it is 92f degrees (they have the setting sun on them right now). It?s unbearable, and we have no business due to the heat. It?s 107f degrees outside right now so why would anyone want to eat in restaurant that is over 90f degrees.