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 makeaccessible 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 .
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.
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.
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,power generation "to meet gaps in demand," LaFlash said.
In some areas, output fromand 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 in Austin.