The Solar Stirling Engine from Infinia Corporation

Jim Clyde was interviewed by Robert Pritchett for this article

“Originally developed by Robert Stirling in 1816, the Stirling cycle uses a working fluid (typically Helium, Nitrogen or Hydrogen gas) in a closed cylinder containing a piston. Heated on one end and cooled on the other, the expansion and cooling of the gas drives the piston back and forth in the cylinder. The work performed by this piston-motion is used to drive a generator (in Infinia’s case, a patented linear alternator) or to create pressure waves to drive a compression process.

The cycle can be operated in reverse by using the generator as a motor to drive the piston. In this case, the continuous expansion and cooling of the working fluid caused by the piston motion creates a cooling effect. These types of systems are called Stirling coolers (also referred to as cryocoolers) and can maintain temperatures as low as 10 Kelvin (-263°C, and –442 °F).”

I remember this company back in the 1980’s (three company name changes ago) when it was working on the engine vehicle. When I asked about it, I was told it was before Jim Clyde’s time at Infinia and so that was buried deep in the past.

Infinia Corporation worked with NASA back then to get a nuclear-based power plant on to a space probe to Mars that could withstand being bottle-rocketed into space from earth, survive the landing on Mars and do its job for 17 years without failing.

Based on those successes in space, they moved on to using this maintenance-free, free-piston generator system for ground-based mission-critical applications for the military and other government organizations.

Remember the program on TV with Tactical to Practical? More

Perhaps Infinia was the inspiration for those episodes by showing how tax-based projects can be converted into real public good.

Today the little engine that could can be found in rare-to-be-found-publicly portable generators, vehicle auxiliary units and mini combined heat and power (CHP) systems. But that is about to all change soon.

Infinia received some well-deserved venture capital to take it up a notch from Paul Allen’s Vulcan Group. They are being extremely conservative about what is possible and what has been accomplished so far and that is probably why you never heard of them before. But you will. I’ll see to it.

Why? Because they are also using this inspired device to generate electrical power from sunlight!

Will you be able to have this on your roof? No. At least not in the near future.

Will you be able to have this on the ground using a 2-axis stand (2 axis poles provide 50% increase in efficiency)? Yes – if you are a commercial site.

Will there be direct sales or dealerships? Yes, to fill government contracts. Yes, to solar distributors for commercial installations.

How soon? The Solar collector and engine units will be visible at the company location in October with prototypes being tested around the USA in January, so expect (if nothing goes wrong) these units to be available in the Fall of 2008. They just removed the “1^st gen” that was located just west of their building that had been there for nearly 2 years. I thought it was a closed-circuit broadcast dish that the local TV stations use. Boy, was I wrong!

The $2-billion + alternative energy industry is heating up and you will have to wait in line after the government and commercial entities have gorged at the feeding trough first. Perhaps by then the whole unit will have been reduced in size even further. Can you hold out for the roof-top version in 2 or more years (if ever)?

This is tantalizing tech!

The key to all this effort are the patents that have been carefully and patiently preserved for close to 2 decades.

And what I feel is the real key to the free-piston engine is the patented flex-spring technology shown above. You wouldn’t know it by just looking at it, but if you pushed down on the handle in the first picture, the two “wheels” would flex downward (assuming the outer edges were anchored to something) and in the 2^nd picture, the holes in the outer rim are for anchoring. The center would be where the free-piston would be located and there are 6 or eight of these rings that can flex a few millimeters in either direction as the gas heats and cools inside the hermetically sealed engine.

The recent job postings at Infinia indicate that this technology is going to leap Photovoltaics in the next year or so, because it can do nearly twice the power in the 1/3^rd the space and for less cost than for a Photovoltaic array based on the same power requirements. Fewer parts, cleaner design, smaller components equals quick assembly (relatively speaking) in comparison to the turn-around time for photovoltaic cells to finally get to sunlight and produce power.

Internally these electric-generation jewels contain not only the generator, but the alternator and the inverter, none of which have mechanically moving parts. No brushes, no bearings to wear out, etc. What was simple has been made even simpler still.

The materials are essentially off-the-shelf metal parts that do not have the legacy issues of pollution and brown-fielding activities associated with the long process of creating silicon-based solar cells. (By the way, one of the largest manufacturing facilities for solar silicon is also here in Washington State – except all product is being shipped to Norway for further processing and used in Europe. So far, none of it has “reached home”.)

The latest 3.3kW stirling engine unit is going the solar mirror dish route and those units take up a little bit of space. In this picture below, think of the frame as a gun turret for side-to-side and swivel up-and-down motion.

Remember the first set of dishes that came out for satellite reception? These are smaller. A real live one will be planted next to the Infinia Corporation building in Kennewick, WA soon, so concept will become reality.

Why did I interview Jim Clyde (VP of Marketing and Business Development) now instead of waiting a year? Because it would be really sweet if I could have a day job with a company that has taken “old” technology, spiffed it up and made it leapfrog what we would consider the latest in Solar Tech today. And because I wanted to see for myself if this technology was consumer-ready for prime-time. Just hold your breath for a little while longer…

Meanwhile, the engine by Infinia Corp is seeing the light of day in systems being OEMed to Rinnai in Japan for combined heat and power units that probably will be sold here in the US within a year and also by Enatec in the Netherlands.

What was old has been made new again and we can see that the “not invented here” syndrome does not exist at this company. They have taken the best of the best and made it literally shine around the world!

A presentation was given to the Alternative Energy User Group January 4th, 2008 by Seth Poulson and Rocco Luongo.