Image Credit: Steven Depolo / Flickr

Image Credit: Steven Depolo / Flickr

It costs a lot to keep cool in America.

According to the U.S. Energy Department, air conditioning uses about five percent of all the electricity produced in the nation. That adds up to more than $11 billion in annual costs, to say nothing of the damage it does to the environment. Some 100 million tons of carbon dioxide is emitted into the air each year from A/C, absorbing heat energy and gradually raising the planet’s temperature. This creates a positive feedback loop in which the warming of the globe induces more air conditioning use, which induces more carbon emissions, global warming and so on.

This feedback loop has been highlighted by the U.S. government as a major cause of concern in its report on the social cost of carbon. In fact, in its climate Framework for Uncertainty, Negotiation and Distribution (FUND), the reduced electricity costs of not having to run air conditioning as intensely is viewed as the “largest single benefit category.”

Reducing both the costs and the environmental impact of air conditioning is what energy storage company CALMAC is all about, and their solution is as simple as it gets: Ice.

The IceBank® Energy Storage System

calmacCALMAC’s IceBank Energy Storage System is fairly easy to understand: Once installed in a building, it creates ice overnight when electricity costs are low. That ice is then used to cool the building during the day, saving on the higher-priced electricity that regular air conditioning would cost during peak hours.

And it does cost. According to the American Council for an Energy-Efficient Economy, commercial buildings account for 19 percent of the energy consumed in the United States. Two-thirds of that energy is spent on temperature control – most of which occurs during the day.

I contacted Mark M. MacCracken, the CEO of CALMAC Manufacturing Corporation, whom explained the pricy dichotomy of day and night electricity rates.

“Ninety-nine point nine-nine percent of people – probably in the world but certainly the country – think that the cost of electricity is the same day and night,” said MacCracken, “because, at home, they are charged by how many kilowatt hours they use and normally there’s no difference between day and night power. The utilities like to kind of promote this idea and you’ll hear a term called ‘flat rates.’”

Mark M. MacCracken, CEO of CALMAC

Mark M. MacCracken, CEO of CALMAC

To illustrate the problem, MacCracken pointed to a commercial building in Austin, Texas that has a purported flat rate of five cents day and night. “And that would give most people the impression that you’re paying the same price for electricity day and night,” he said. “What they don’t highlight is that they also have what’s known as a demand charge.”

Whereas a residential rate is based on how many kilowatt hours (kWh) a homeowner uses, commercial buildings are charged by kilowatt hours (kWh) plus peak demand (kW). That demand (kW) charge is where the costs really add up. MacCracken likened peak demand to the speedometer of a car. “They measure the fastest the car goes anytime during the month,” he explained. During especially hot days, a building’s chiller (the machine that removes heat from liquid to create cool air) can really make that speedometer spin.

“They measure your peak demand for a 15-minute period,” said MacCracken. “And whatever that 15-minute demand is, they multiply that by something like $14 per kilowatt per month.”

According to MacCracken, that kilowatt demand charge makes up 50 percent of the commercial electricity bill in most cases around the country. So that building in Austin that claims to charge five cents day and night really ends up charging something like 12.5 cents during the day and five cents at night.

Put that way, it’s not hard to believe that CALMAC has installed its IceBank system in over 4,000 businesses and institutions in 37 countries over the last few decades. Sure, it’s nice to cut down on carbon emissions, but the real selling point is the savings.

“For years we’ve been selling on really just the cost arbitrage between day and night power,” said MacCracken.

How Much Energy Does Ice Storage Save?

As CALMAC explains in this video on thermal energy storage, the idea behind ice cooling is the same as making ice before a party. Just as you wouldn’t wait until the party had begun to start making ice, you needn’t do the same when employees start filing into the office. That immediately puts a high demand on the building and the energy grid.

“Why would you instantaneously have this on-peak demand,” asked MacCracken, “and draw tons and tons of power – that we have to build a hugely oversized grid for, and for a very small period of the year – when you can very easily make that at night [and] store it? Then you don’t need all this power during the day.”

Ice is like gasoline in the sense that the energy it provides (i.e. cooling) is stored within the substance itself. This is what makes oil and coal such desirable fuels: They can be stored and used as needed. By comparison, affordable storage systems for renewable solar and wind power are still under development (and making progress). But in the present day, storage of electrons in the form of batteries is expensive, and since so much electricity is needed for instantaneously creating the cooling, CALMAC says, “Why not just store the ice?”

After water is frozen, it can be used to cool a building throughout the day, putting no strain on the grid. And, unlike gasoline, once the ice is used (i.e. melted), it can be reused the next day.

According to MacCracken, freezing water at night to use in place of a conventional air conditioning system saves the equivalent of about 35 percent of the total electric draw on a hot summer day.

“You take 35 percent off that peak and now you’ve got the grid operating almost where it is on an average day,” he said.

How Does It Work?

A conventional central air system can easily be retrofitted into an IceBank system. A contractor installs ice tanks into a building, which are then fed into the duct network already in place for an applied or central system. The chiller serves the same role in both systems, cooling down the liquid – except in the IceBank system it is used to make ice in the tanks.

CALMAC's ice tanks.

CALMAC’s ice tanks.

The installation time, according to MacCracken, is minimal. “In Park Avenue Plaza,” he said, “a major building for Fisher Brothers in New York City, they dropped 50 tanks into the basement of the building in two days. So, you know, it’s not a big deal. They’re also doing a chiller replacement at the same time, but the time to install isn’t really a factor at all.”

MacCracken adds that the company is very proud to be installing in New York City, which is 15 minutes from the CALMAC factory. “It took us twenty-something years for us to get our first installation,” he laughs. The reason being, when it comes to air conditioning, NYC only accepts the tried and true.

“You need to be a really proven product to be able to make it in New York City,” said MacCracken, “because people are not happy when they’re hot.”

CALMAC has since installed IceBank systems in over a dozen buildings in Manhattan, in 30 Rock, the Bank of America Tower, Goldman Sachs, Morgan Stanley, Credit Suisse, Rockefeller Center and the New School.

In the 20 years or so it took to get to New York, CALMAC has been busy around the world meeting the rising demand for more natural cooling.

“I know I’ve air conditioned you,” said MacCracken. “If you passed through certain airports – we’ve done a lot of airport installations. You know that yellow duct that comes off the jet bridge and plugs into the bottom of the plane? That’s cold air and a lot of times that’s coming from ice.”

Why Does It Work?


Installing an IceBank system not only saves businesses money, it also helps them achieve LEED points in Energy & Atmosphere, the largest credit area for new and existing buildings.

Leadership in Energy and Environmental Design (LEED) is an internationally-recognized building certification system created by the U.S. Green Building Council (USGBC) that rates buildings on their environmental soundness and energy efficiency. Some federal, state and local governments offer various initiatives and incentives for LEED-certified buildings, but the certification mainly serves as an indicator that the design incorporates next generation principles.

But even beyond the environmental value, IceBank simply improves the livability of modern buildings.

“That’s the big deal about our storage” said MacCracken. “With traditional demand response, the occupant is going to see a difference in the comfort of the building: A couple escalators might be turned off, there might be a longer wait on the elevator, the temperature might be set a little higher, or the lights might be lower. All these different tactics are used to lower peak demand. With cool storage, occupants don’t know any difference. The building can reduce peak demand easily by 10 percent and you’re just melting ice and you’re not running the chiller. There’s no difference in comfort.”

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