I've been thinking about flat-panel solar thermal to electricity for years as a very cheap alternative to PV (although based on organic rankine cycle). Could be easily scaleable for cheap, storeable, on-demand electricity.

But for solar thermal to electricity, it doesn't really matter if it's only 10% efficient. Plastic panels are cheap!

@ Michael McMillan -

the company's GRE is a steam engine, which is fine for stationary applications if the pressure can be controlled - i.e. safely bled off in case things go haywire. The IP is really in the combustion chamber.

Since the WHE is derived from the GRE, I expect it's a smaller, less efficient but also less expensive steam engine. Less dangerous, too.

Automotive history buffs will recall that very early on, steam power competed against both ICEs and electric motors. Steam offers constant power at any engine speed, subject only to a maximum torque rating. No clutches, not even a transmission to worry about.

Unfortunately, it takes a long time for a boiler to work up a head of steam, i.e. system dynamics are unacceptable for the prime mover in an automobile. Plus, boilers explode violently in a crash. Another obstacle is weight, as thermodynamic efficiency is poor at low temperature differentials and pressures are high at high ones. Finally, you need a large radiator to shed the heat of a Rankine cycle in a mobile application, unless you blow off the waste steam and frequently take on additional water.

BMW is working on a long-term research project called turbosteamer to leverage waste heat using a rankine cycle based on ethanol as the working medium. Also, VW had IAV in Berlin develop a demonstration steam engine with reciprocating pistons but it ran smack into the weight-vs-efficiency issue.

Personally, I think hermetically sealed Stirling gensets with four free pistons and linear alternators are the way to go for those mobile applications that need the efficiency and have sufficient space to fit one. To keep pressure and weight within reason, the working medium would be hydrogen, even though that means using special materials to avoid hydrogen embrittling. The output would be electric rather than shaft power.

Elliot, you need to change your frame of reference. Waste heat is not fuel, it is energy that has not been harnessed. These products aim to harness the heat energy from fuel that was previously used to push a piston down inside an ICE. Generally you would feed this recovered energy into an accessory like an A/C compressor for instance.

I find thi to be very interesting. I live in SC, and I have had a solar hot water system installed (pressurized glycol type). That sucker gets HOT, and produces much more hot water than my family needs with 2 collectors (4x8 ft).

Supposedly, the he panels can collect 40,000 BTU each in a day under optimal conditions. What is that, just under 12 kwh?

I'm not sure what the efficiency of a sterling engine can achieve, but if it decent, then collecting 6 kwh per panel per day seems reasonable.

Not sure how real world performance would compare to PV or a direct solar concentrator-sterling setup. PV may do better in overcast situations.

Rafael,

I agree with you that a hermetically-sealed free-piston Stirling with built-in linear generator is more practical than a Rankine-cycle engine for converting low-grade heat to electricity.

For low-grade heat, an organic Rankine in a closed cycle would invariably be the case, and this is subjected to the use of potentially flammable or toxic organic solvents such as Toluene, or Florinal, or Acetone, etc. and would be more bulky, since condensation at lower temperature than steam at 1 atm would require a rather bulky heat exchanger, with plenty of change for leakage eventually with time. Plus, more complication including pumps and a lot of valves, crankcase, bearing etc...
whereas in a free-piston Stirling, a linear generator designed to harness power directly from a reciprocating piston has almost no mechanical loss, and much lower piston friction due to the lack of side force on the piston skirt in the absence of the crank mechanism. An organic Rankine cycle cannot utilize high heat because the working fluid will decompose, while the Hydrogen-Stirling can use much higher temperature for higher thermal efficiency.

A solar heat collector powering a free-piston Stirling would be real neat, since you can use natural gas to generate electricity during sun-down period, and use the waste heat for your hot water storage tank, or use the waste heat to heat your house in the winter while selling the excess electricity back to the grid to charge up someone else's BEV's. Combined solar electricity and distributed generation with combined heat and power generation (CHP) all in one system and one investment much lower than a PV panel system with inverters of equivalent output.

A hermetically-sealed Stirling engine can be built to last for tens of thousands of hours with minimum maintenance, if properly designed, and not subjected to too high temperatures.

3M makes HFE fluids with low boiling point, non flammable and not as harmful for the environment as CFCs. BMW uses ethanol, which is cheap, but flammable. But them again, automobile fuel is flammable and direct injection pressures are high. I guess it is all in how you look at the safety of the fluid you use.

Michael McMillan, LEARN SOMETHING ABOUT THE "GRE" (I.E. CYCLONE ENGINE) BEFORE YOU POST COMMENTS. THIS KIND OF BLATANT MISINFORMATION IS INEXCUSABLE!

The automotive cyclone engine is a 100 hp, 6 cylinder, 618 cc, uniflow, radial piston engine with 700 ft lbs of starting torque. Engine starts in only 15 seconds from cold and is fully warmed up in only one minute (faster than Diesels). The entire system weighs less than half that of conventional automotive systems of equal power. The condenser is full contained in the compact unit and is extremely compact. There is ZERO danger of a boiler explosion. The thermal efficiency of the Cyclone is in the Diesel range and peak effiency was measured at 36%. The water/steam system is fully contained with ZERO need to add water. Power is controlled by steam inlet valve timing and moderating compression ratio. The steam pressure is not throttled but remains constant at 3200 psi with temperature of 1200F.

Email me if you want more info, but please do not make further comments on this technology until you understand it.

Mark,
I certainly can sympathize with your frustration at times.

However, these "unprepared" responses from this forum, or responses by less-than-experts, to put it politely, can give you valuable feedback on how to go about preparing for the promotion of your project. Many potential investors have little technological background, and therefore, the advantages of new ideas must be hammered on and on relentlessly in layman's terms and approaches before they will sink in.

It is only human nature to have pre-conceived notions or biases, especially against new and revolutional ideas. Howver, through patience and persistence, these unfavorable notions will [sometimes] slowly change.