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Batteries

Published on September 6th, 2016 | by Tina Casey

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Energy Storage Mashup Aims Thermal Tech At Fruits & Veggies (And Ice Cream)

September 6th, 2016 by  


The US company Axiom Exergy has been wasting no time getting its new thermal energy storage technology to the marketplace. Just 18 months after nailing a glowing review from the Department of Energy’s National Renewable Energy Laboratory, Axiom has inked a major deal with the New York City utility Con Edison to supply its “Refrigeration Battery” to grocery stores all over Brooklyn and Queens.

So, grocery stores. That doesn’t sound too sexy, but when NREL reviewers say things like “the Refrigeration Battery system could provide an economical alternative to electrochemical battery storage systems,” it’s game on for Tesla and other big players in the super-hot energy storage marketplace.

thermal energy storage

NREL Likes What It Sees

To be clear, the NREL technical review was based on spreadsheets provided by Axiom, not on field observations collected by the reviewers.

However, according to NREL the spreadsheets deployed sound methodologies, and the reviewers are confident about their conclusions.

The numbers are impressive:

The round – trip efficiency of the Refrigeration Battery is expected to be between 73% and 80%, which will likely improve as the Refrigeration Battery design is developed further.

According to NREL, that’s about the same savings as  electrochemical storage systems could deliver — think Powerwall and you’re on the right track — but the Refrigeration Battery offers an important advantage:

As a result of its lower installed cost, the Refrigeration Battery system could provide an economical alternative to electrochemical battery storage systems.

In the report, NREL is looking at a simple payback period of just under three years. That sounds pretty good, but Axiom currently has something even better up its sleeve.

The company offers a shared savings option that enables stores to get their hands on a Refrigeration Battery without up-front costs. It’s a little bit like the power purchase agreements that have become familiar ground in the solar market. Your electricity bill goes down, and that savings goes to pay for the equipment in monthly installments.

Our friends over at Energy Manager Today provide a good rundown on shared savings agreements, which they call “a quantum step forward in the way CFOs evaluate and mitigate risks associated with investments.”

SSAs can cover all manner of energy efficiency investments — and not just for buildings, either. One interesting twist involves adding solar-sourced batteries to delivery trucks, which the owner can pay off through savings on diesel fuel.

Energy Storage For Fruits And Veggies

Where we we? Oh right, Axiom Exergy. The idea of thermal energy storage for load-shifting is not a new one — the basic idea is to make ice at night, when demand is lower. Business that use their stored coolant during the day can avoid the extra charges that utilities tack on during peak use periods.

Axiom is focusing on the supermarket and cold storage category because of its unique demands. Typical refrigerated units in stores are constantly being opened, and left open. Many units are open-air and don’t have doors at all.

Axiom also offers its own twist on the conventional technology. Axiom provided some insider-y details last December to the Phase Change Matters blog, which is hosted by the company Puretemp.

The energy storage system is based on a “standard, off-the-shelf, ice-on-coil tank.” As you may surmise, the secret sauce is a phase change material:

The tank is filled with a proprietary salt-water eutectic solution that freezes at a relatively constant temperature that is well below 32 deg F.

A heat exchanger in the tank does the grunt work. It contains a coolant that draws heat out of the tanks at night, and pushed heat into them during the day.

In the Phase Change Matters interview, Axiom also provided a cost breakdown:

Compared to traditional electrochemical batteries, the Refrigeration Battery is 75% cheaper (in installed $/kWh) and has an expected useful life that is 3x longer. Unlike battery systems (which are typically used for short-­term peak shaving), the Refrigeration Battery shifts 100+ kW of baseload for 6+ hours.

“Unintelligent” Equipment Gets Smart

Con Edison has been involved in some interesting energy efficiency and storage projects lately, including green roofs.

The new deal with Axiom dovetails with the utility’s recently announced “virtual power plant” program, which involves coordinating hundreds of rooftop solar arrays.

Under the new agreement, Con Ed’s Neighborhood Program will provide incentives for store owners to install the Refrigerator Battery system.

Stores with the Refrigerator Battery will be networked into Con Ed’s virtual power plant:

The fleet of Refrigeration Batteries in the Con Edison Neighborhood Program will respond to Con Edison’s signals requesting electricity demand reductions. In order to provide host sites with even greater energy bill savings, each Refrigeration Battery can also permanently shift large refrigeration loads away from on-peak hours (when electricity is most expensive) on a daily basis.

That permanent load-shifting could relieve store owners from up to 40 percent of their peak demand.

Here’s a nifty graphic from Axiom that illustrates the difference (the “before battery” load is in red):

energy storage load shifting

Axiom’s energy management system also gets a turn at the plate. In effect, it adds a smart grid element to existing equipment:

Controlled by Axiom’s KARL cloud platform, the fleet of Refrigeration Batteries will also provide facility operators and Con Edison with real-time fleet performance monitoring, data analytics, and alerts, adding significant intelligence and flexibility to otherwise unintelligent refrigeration equipment.

The goal of the Con Ed/Axiom agreement is to install between 1.5 and 2 MW of the systems, which would be enough to shift 6-8 MWh of energy. The total cost will top $5 million.

Con Ed is also trying to get store owners to install doors on existing open-air refrigerated units.

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Images: via Axiom Exergy.


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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



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