Breaking the Ice with Thermal Energy Storage
Quick quiz: Where can somebody find a very common substance that has the potential to drastically reduce energy spending – especially at peak price points when electricity is most expensive?
Answer: Any freezer.
Granted, the scale in the use of ice to cool a building and to cool a glass of ice tea is significantly different. But the bedrock principle of energy transfer is the same. Thermal cooling leverages that concept by freezing water at night, when the energy required to do so is less expensive. The melt water is stored and circulated as it is needed during peak demand times the next day. Thus, the heavy lifting — the energy-intensive process of freezing the water — is done at a point at which costs are lower.
Interesting use case studies were posted during the past few weeks. The Herald Tribune last week reported that a thermal storage system featuring 36 ice tanks is being used by the Sarasota County School District in Florida. It seems to be working: The state says that the district is paying 96 cents per square foot for energy, which is 24 cents less than average and ninth best among districts in the state.
The story doesn’t say so, but the Sarasota schools are using a system from CALMAC. CityLab posted a story on CALMAC’s thermal storage several weeks ago. The piece points out that ice cooling is a concept that goes back at least as far as the Revolutionary War. It has been updated and is attracting attention:
CALMAC has been using it successfully in commercial buildings since 1979. Its new system in the new Goldman Sachs Tower in New York City freezes 1.7 million pounds of ice every night in 92 basement tanks. A rival firm, Ice Energy, uses similar technology to run cooling systems for both residential and commercial applications. The principle is simple and elegant, since an ice battery has no moving parts and doesn’t corrode or wear out like chemical batteries.
Earlier this month, New York City utility Con Edison and Axiom Exergy announced that thermal storage is being made available to businesses with special cooling requirements in the boroughs of Brooklyn and Queens. The offer is through Con Edison’s Neighborhood Program. The companies aim to install between 1.5 MW and 2 MW of refrigeration batteries, which carry a value of more than $5 million. The system is designed to work with existing refrigeration systems. The target businesses are grocery stores and cold storage facilities, according to the press release.
A nice backgrounder of Axiom Exergy is available at Clean Technica. The company is aiming at supermarkets and similar businesses because their needs fit very nicely with thermal energy storage. Supermarkets, in particular, are a good target: It costs lots of money to power cooler and freezer cases, which are subject to use patterns by consumers that make them inefficient. The company announced $2.5 million in funding from a number of investors early last month.
A final recent posting on thermal cooling is a bit different. Maine Public Radio reports on use of 31 ice batteries – or “ice bears” — in the Boothbay Harbor area. The difference is that they are presented not as a panacea, but as part of a bigger effort to power the town sufficiently when the population explodes during the summer. Without such a plan, Boothbay Harbor may be forced to erect an $18 million transmission line that only is needed for a few months per year.
Thermal cooling strategies have a lot going for them. They are energy efficient, largely passive – water, by freezing, in essence supplies its own storage — and rely in many cases on technology that already is largely in place. The trend towards hotter summers – and, therefore, more peak demand – may give renewed value to an old technology.
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