Cool Energy from a Solar Heart

On September 10, 2013, in Blog, by Jeanne Roberts

The title isn’t confusing once you realize that the ‘cool’ aspect stems from a technological giant step forward in Stirling engine design.

Stirling engines, unlike vehicle combustion engines (which burn a fuel), work by expanding and contracting a working fluid at different temperatures. Most Stirling engines work most efficiently at about 1000 degrees Fahrenheit (1000 °F), the typical temperature of exhaust when it leaves a large turbine like a GE LM6000.

These very high exhaust temperatures, typical of heat engines burning fossil fuels to create electricity, are the byproduct of 80 percent of electricity generation methodologies.

Smaller applications, as used in manufacturing, or for electricity generation at remote (military) outposts, or even aboard ships for both motive power and electrical support for electronic communications equipment, etc., produce cooler exhaust which until recently was not seen as worth capturing.

But all that is changing as the environment does some number crunching of its own, and Samuel P. Weaver, president, CEO and co-founder of Cool Energy, Inc. is the brains behind the 21st-century Stirling engine adaptation that will make low-temp engine exhaust recovery both feasible and affordable.

This new kid on the block is the SolarHeart® Stirling engine, an impressive ‘mighty mite’ which captures temperature differentials in the 100 to 300-degree (Celsius) range, significantly below exhaust temperatures that have traditionally been considered optimum for waste heat capture. In fact, the SolarHeart® is so ‘cool’, it can trap enough waste heat from industrial processes and large-scale HVAC systems to offset almost a fifth of the energy needed, particularly at remote locations where bringing fuel in is difficult and these difficulties drive the cost of said fuel to $15 per gallon or more.

Weaver is also on the board of directors of Proton Power, Inc., another high tech energy firm also located in Boulder, Colorado. In addition, he is responsible for the Colorado-based startup, Colorado Photonics.

When not working on one enterprise or another, he invests time and brainpower in Colorado’s technology and business marketplaces, using his B.S. degree in engineering and applied sciences from the California Institute of Technology, or Caltech, to generate inventions (17 of which have been patented).

During vanishingly small amounts of free time, he also sits on the boards of Clean Energy Action, and the Colorado Clean Energy Development Authority (Alternative Fuels Data Center, or AFCD, a working arm of the U.S. Department of Energy’s Energy Efficiency and Renewable Energy (EERE) agency.

Weaver is also a member of the City of Boulder Planning Board – and if you aren’t as tired as I am just thinking about all this activity, you’ve likely been skimming instead of reading. But back to the subject: the intense effort to capture waste heat, which one energy site referred to as the “sleeping giant” of all energy – an extrapolation that does the math, and it’s not fuzzy logic either.

There is at least 8.4 million megawatts (MW) of free energy, based on a thermal efficiency of 40 percent of the 14 terawatts (TW) of global energy consumption in 2003, rising to an estimated 24 TW of consumption and 9.6 million MW of potential savings by 2013, according to Nobel Prize winner Dr. Richard Smalley of Rice University.

Still not convinced that waste heat capture is the next big thing? As Bloomberg financial points out, more than 50 percent of the energy produced in the U.S. in 2011 went to waste up smokestacks and out exhaust flues. This includes not only the excess heat from industrial operations, but also that which results from generating electricity – not to mention the smaller amounts of boiler heat exhaust from large apartment buildings and offices, small factories and even the local Panera bakery.

The amount of waste was calibrated by the DOE’s Lawrence Livermore National Laboratory (LLNL), another one of the 17 laboratories operating under the DOE’s Office of Science. But the real heavy lifting was done in 2006, when the Pacific Northwest National Laboratory, another of the DOE’s 17 labs, studied the problem of waste heat from industrial emissions.

“Realistically,” Notes author Gary Beck, “most locations are probably just too remote or too distributed to justify heat recovery.”

He uses the example of heat recovery from rural cooking fires to make his point. But it is only very recently that the SolarHeart® Stirling engine has been able to maximize that potential, recapturing over 22 percent of wasted heat. The next generation of SolarHeart® Stirling engines should be at even better, at 25 percent efficiency conversion.

For those baffled by engines in general, the Stirling is an engine that works off the difference between exhaust heat and outside air. That is, instead of using fuel to move pistons to generate energy, the Stirling engine uses the differential between heated exhaust gas and cool air to play tennis with itself. When the piston goes up, energy goes to a generator; when it goes down, the gas has been cooled, and because it is cooler it is easier to compress for the next iteration. The difference (between tennis and Stirling engines) is that the engine always wins!

Using the SolarHeart® engine, U.S. military ops working from a remote station can reduce the amount of fuel needed by 5 to 10 percent. When fuel costs $15 a gallon, this is a huge chunk of change. Next, says Weaver, the company plans to deploy the engine, or engines, to ships, which use one engine to move forward and another for auxiliary operations (lighting, heating, cooking, heated water, etc.)

Where does Weaver’s lifelong fascination with energy come from? As one might expect, from his father, who worked at Oak Ridge National Laboratory, where he acquired a Ph.D. Oak Ridge is another one of the DOE’s 17 labs focusing on energy and advanced materials.

“He is Sam C. Weaver; I am Sam P. Weaver,” the younger Weaver notes, “and his profession meant I grew up talking and thinking about energy.”

His residence in Boulder is a bit of serendipity. As an energy guru, he was able to advise city fathers and concerned residents about the proposed takeover of energy generation and distribution from Xcel Energy, Inc., a Minneapolis, Minnesota-based public electricity and gas utility. The issue has been a thorn in the side of Xcel since 2011, when in Feb. of 2011 the utility cut incentives to homeowners and small businesses that install solar photovoltaic (PV) panels to generate electricity.

The incentive program had been on the books since 2006. The rate, which was before February of 2011 a hefty $2.35 per watt, fell to $2.01. Residential rates were similarly reduced – an across-the-board decentivization that failed to acknowledge the 4,800 jobs created by the program. Xcel also asked the state to cut its incentives and rebates.

Thanks to Homer Energy, also in Boulder, Weaver and a team of similarly educated and public-spirited individuals helped craft a virtual model of Boulder’s takeover and what residents might expect when Xcel’s 20 percent profit margin has been invested in renewables, and the Federal Energy Regulatory Commission has arrived at a figure to pay Xcel for its stranded assets (think distribution lines, for example, which are largely depreciated but would cost the buyer much more if they had to be replaced).

Weaver was enthusiastic:

“Yes, I think it is possible, and it would be a very good idea. In view of that, I think all the utilities need to rethink their business model.”

A remark which foreshadows a future in which more and more local entities bid to take over their electrical generation and transmission systems and transform the whole into a distributed energy platform; that is, power from many small sources as opposed to power from a single large generating plant which, in Boulder’s case, would be the Valmont Station.

Is the nation as a whole ready for distributed generation? Perhaps not, but Cool Energy, Inc. is, and so is Boulder.

“There will be a lot more distributed generation going forward,” Weaver says. “And it isn’t just utilities. Manufacturers can save between 3 and 8 percent of fuel costs by recapturing waste heat. On a global scale, we have estimated a full 300 gigawatts (GW) of energy which could potentially be collected from waste heat!”

A goal which moves closer as the SolarHeart® Stirling engine begins to strut its stuff on the commercial landscape of 21st Century energy paradigms, moving pistons and creating electricity at 80 °C (176 °Fahrenheit) as opposed to the 537 °C (1000 °F) flue gas temperature required by most standard Stirling engine designs.

On a parting note, Weaver adds:

“This is one of the biggest economic opportunities in human history!”


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