Chicago startup’s thermal battery is ‘adaptive’ solution to spikes in electricity demand

A Chicago-based startup is trying to address a major engineering challenge with the electric grid by redesigning one of the most fundamental substances in the universe: ice.

On very hot days, the nation’s power grid strains under peaking demand for electricity to run air conditioners. Increasingly, utilities are looking to electric batteries to address the problem, charging them when demand is low and unleashing the stored power when power plants are stretched beyond their capacities.

But why store electricity to produce cold air if you could just store the cold itself? That’s the idea behind NETenergy, a thermal-energy-storage company founded by Said Al-Hallaj, a chemical engineering professor at the University of Illinois at Chicago.

Of course, it’s not exactly a new idea. Ice and chilled water have long been used to produce cold at one time and use it elsewhere. But as user demands expand and evolve, there is a need for a cooling solution that is “more robust, more adaptive to air conditioning, more adaptive to the smart-grid interface and [able] to react fast,” says Al-Hallaj.

NETenergy’s “Black Ice” aims to do exactly that. A composite of graphite and wax, the technology is essentially a more responsive and flexible artificial ice. The idea is to integrate it with existing air conditioning systems, which can then run at night when energy demand is low to squirrel away cold. Then, at peak hours of demand during the day, the Black Ice is used to cool a building instead of the refrigerants in an electricity-guzzling air conditioner.

The advantage over regular ice is that the Black Ice can be designed to meet the specific cooling needs of an individual structure and it can more quickly transfer energy, says Mike Pintar, NETenergy’s chief operating officer.

“We can charge and discharge in less than two hours, whereas ice takes six to eight hours to charge or discharge, so to speak, when you use it for thermal storage,” Pintar says. By storing cold energy with NETenergy’s thermal battery, the company says building owners can save 30 percent or more on their energy usage and reduce carbon emissions by 50 percent.

Curtailing peak usage

The NETenergy team works out of a squat, gritty, brick building — the former offices of a construction company — on Chicago’s industrial southwest side. The scene there is befitting of the Windy City’s legacy of manufacturing and mechanization, but instead of making refrigerators or butchering hogs, the dozens of workers here are building batteries for an increasingly electrified world.

In addition to launching NETenergy, Al-Hallaj is the CEO of AllCell Technologies, which designs and builds lithium-ion battery packs with a proprietary thermal management system that it says helps absorb and distribute heat — a common design challenge for electric batteries. Al-Hallaj says his experience with the possibilities and limitations of lithium-ion batteries has helped in developing NETenergy’s thermal battery.

Al-Hallaj likens the technology to ice cubes in lemonade on a hot summer day. A freezer makes the ice beforehand using electricity, and then the ice is used to cool the lemonade. It actually absorbs the lemonade’s heat in a process called latent heat of fusion, a transfer of energy that involves a change in state (i.e. the ice melts from solid to liquid) rather than a change in temperature.      

Pintar, a graduate of the University of Chicago’s Booth School of Business, says there’s a market for this kind of technology among commercial and industrial consumers. Unlike residential consumers, businesses usually pay for electricity based on their peak usage levels, so they are uniquely incentivized to curtail energy use on hot summer days or other times when energy is most needed.

Electricity during peak hours can cost two to six times as much as off-peak electricity, Pintar says, and peak-demand charges can account for as much as half of a commercial enterprise’s energy bill. Many utilities are contemplating or have already implemented similar peak-time programs for residential users.

A growing need

NETenergy won the 2015 Pritzker Foundation Prize as part of the Clean Energy Trust’s Clean Energy Challenge. In 2015, NETenergy was awarded $250,000 as part of the Wells Fargo Innovation Incubator, which is co-administered by the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL). After doing initial modeling, the technology was awarded an additional round of $250,000 in funding to integrate the technology with existing energy software and testing a full-scale prototype at NREL’s thermal testing facility.  

The global, long-term outlook for a more efficient cold-storage technology is promising. As global temperatures rise in coming decades — and as developing economies seek higher standards of living — the world is expected to add 700 million air-conditioning units by 2030 and 1.6 billion by 2050, according to a 2015 study by the Lawrence Berkeley National Laboratory.

These units typically include Hydrofluorocarbon refrigerants (HFCs), which are the fastest-growing of greenhouse gases, according to the study. In 2016, 197 countries adopted an amendment to phase down HFCs under the Montreal Protocol in Kigali, Rwanda.

“The world room air conditioner market is growing fast with increasing urbanization, electrification, rising incomes and falling air conditioner prices in many developing economies,” the study reads. “In the absence of policy to mitigate the impact of this growth, it is expected to have a large-scale impact on electricity generation capacity and peak load particularly in economies with hot climates, and contribute significantly to GHG emissions.”

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