Corvallis firm’s high-tech chiller could be hot ticket for utilities

One of the most vexing problems with renewable energy sources such as wind and solar is that they generate electricity intermittently, and there’s no good way to store surplus power for later; it’s a matter of use it or lose it.

A Corvallis startup, Applied Exergy, is hoping to solve that problem with a new technology called TAGES, or Thermal Approach to Grid Energy Storage.

TAGES (pronounced “tags”) uses a new kind of heat exchanger developed at Oregon State University to store energy in the form of an icy slush, then uses waste heat to cheaply convert it back into electricity when it’s needed.

“The melting of the ice spins the turbines and generates electricity that goes into the grid,” said Michael Baker, the new company’s CEO. “We allow these renewables to be far more contributory to supplying energy demand.”

The heart of the system is an advanced microchannel heat exchanger developed by the late professor Richard Peterson and his research team at OSU.

Chief engineer Kevin Harada, who worked with Peterson on the project, described the TAGES device this way:

“It’s essentially an air-conditioning unit combined with a steam power plant,” he said. “The efficiency of the plant is based on temperature differences.”

The TAGES device is highly efficient because of its microchannel heat exchanger, which has three patents pending, Harada said. Water ordinarily freezes at 32 degrees Fahrenheit, but routing the flow through sub-millimeter tubes alters the liquid’s physical properties in a way that permits supercooling.

“We actually bring the water down below its normal freezing point, in the range of 29 to 30 degrees,” Harada said.

Instead of slowly creating a giant block of ice in the system’s storage tank, that supercooling process quickly produces a semisolid slurry of small ice particles. The frozen slush has lots of exposed surface area, and that makes it much quicker to melt than a single massive chunk.

When it’s time to release the energy stored in that ice, waste heat from the operating environment — which could be an industrial facility, a large power plant or just warm air — is used to heat the water within the closed system, causing it to flow through the blades of a turbine generator.

“The advantage of the ice slurry is it’s very tiny little ice cubes, so water will flow through it,” Harada explained. “We take that water, we heat it up and flow it back through the system to melt the ice.”

Portland General Electric, while not a partner in the venture, has had discussions with Applied Exergy about the TAGES device. It’s one of many new technologies the utility is evaluating for electricity storage potential.

As it works to obtain 25 percent of its power from renewable sources by 2025, PGE is being forced to confront the challenge of intermittent generation, according to Joe Barra, senior consultant in business model development for the company.

“Energy storage could be a very important part of the solution for us, particularly for a resource like wind, which tends to blow more at night,” he said.

While he described Applied Exergy’s approach as “promising,” Barra was careful to note that PGE has not committed to buy any TAGES systems.

“I don’t think there’s going to be one silver bullet here,” he said. “I don’t think there’s going to be one technology taking care of this but probably a combination of things playing a role and filling a need.”

Applied Exergy recently received a $150,000 grant from the Oregon Built Environment & Sustainable Technologies Center to build a demonstration model, finalize its patent applications and validate performance and cost assumptions.

That comes on top of $325,000 in financial support from the Corvallis-based Oregon Nanoscience and Microtechnologies Institute, $200,000 from the OSU Venture Fund and some private investment from Baker and the Peterson estate.

This week the company began approaching outside investors in search of about $15 million in A-round financing to bankroll initial manufacturing and assembly infrastructure. Eventually, Baker hopes to build a factory in Oregon to produce the TAGES units on a commercial scale.

“The sweet spot on size is 1 megawatt and up,” Baker said. “That’s where the return on investment and the payback is.”

According to the company’s calculations, the installed cost of a TAGES system would be something under $1,000 per kilowatt-hour of generating capacity, with operating costs of less than $200 per kilowatt-hour generated.

The individual units will be skid-mounted for easy transport by tractor-trailer or freight container, and they’ll be stackable for easy scalability.

With the worldwide push for renewable energy driving a rapid expanse of the market for grid-scale storage technologies (a recent report by Lux Research projected it would be worth $113.5 billion by 2017), Baker thinks TAGES has the chance to generate a major payday.

“There’s going to be a lot of players in this space; we’re not going to capture all of that,” he said.

“But in fact I think this is a multimillion- or a billion-dollar business. It has that potential.”

Contact reporter Bennett Hall at or 541-758-9529.

Special Projects Editor, Corvallis Gazette-Times and Albany Democrat-Herald

(1) comment


"According to the company’s calculations, the installed cost of a TAGES system would be something under $1,000 per kilowatt-hour of generating capacity, with operating costs of less than $200 per kilowatt-hour generated."

I hope that is a misprint. Even in the highest electricity cost areas like CA the cost per kilowat-hour is in the range of $0.50. An operating cost of $200 per megawatt-hour could be competitive.

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