Friday, July 01, 2005


Welcome to Charge: the future of energy

Designers of new types of heat engines almost never show up at alternative energy conventions or finance conferences. The engines themselves are generally ignored in discussions of peak oil or global warming or the hydrogen economy, and most environmentalists have no idea they even exist. In fact I have found that among the relatively few analysts in the field of alternative energy, most know almost nothing about the subject, and I’ve given more than one informal tutorial on the subject. So if, as I indicated in the previous post, further development of heat engines is more likely to ease our immediate problems concerning a carbon dioxide build up in the atmosphere and declining reserves of fossil fuels than fuel cells, how come engines remain below the radar screen, so to speak?

I think that there are a number of reasons why innovation in the field of heat engine design goes so unrecognized.

First of all, almost all of the innovation is incremental. All of the primary heat engine designs were invented long ago and the fundamental design possibilities have been exhausted. What we have today are embellishments and refinements, albeit improvements of considerable significance.

Second, the barriers to market entry are simply more evident than is the case with fuel cells. Fuel cells are something like atomic energy was in the nineteen fifties, a new technology so seemingly marvelous that its triumph appears both inevitable and obvious—so obvious as to discourage any careful consideration of the new technology’s real suitability for the markets it addresses. Innovative heat engines, on the other hand, are close enough to existing designs that one can see them within a clearly defined competitive context.

And that context, as it happens, is pretty daunting. In most of the niche markets for engines the manufacturers are few and well entrenched and enjoy oligopoly status. Stationary power, portable power, backup power, automotive, power tools, marine, and aviation—in every market there are very well accepted designs and very well established relationships between the engine makers and the industrial customers for the engines in the cases where they aren’t one and the same. In the automotive field, the single biggest market, forget it. No auto maker is going to buy an innovative design from a startup—not under any circumstances. There is but one single instance of a truly innovative engine being purchased by a major auto manufacturer that being NSU’s acquisition of the Wankel design in the nineteen fifties. Other than the Wankel, the only other success in any market is the adoption of direct injection by two stroke engine makers in the last few years, most of them licensing either the Orbital Engines or Ficht designs. Unquestionably this is encouraging, but it is well to remember that two stroke designers were facing grave losses because they could not meet toughened emissions requirements in many countries. Direct injection saved their bacon by bringing emissions in line with those of four stroke designs.
What about microturbines, that much heralded technology that garnered much publicity in the late nineties? It may be too soon to say that microturbines will not succeed in distributed power applications, but sales so far have been unimpressive.

Perhaps at this point it might be well to indicate where research is currently focused on improving heat engine design and what entities both corporate and governmental are involved in such research.

Most research is rather narrowly focused on improving one or at most a few aspects of established commercial designs. Perhaps the most heavily researched area in heat engine design in recent years has been what is known as direct injection of fuel with air intake occurring separately, a technique which has always characterized conventional diesel engine but which is now being extended to gasoline engines, particularly two cycle gasoline engines. Direct injection has the potential for improving both the efficiency of an internal combustion engine and reducing its emissions. Why this is so will be explained in a future posting but it is indisputably true. Direct injection is used in all compression ignition diesel engines and is the main factor behind their superior efficiency in respect to spark ignition engines (diesels are approximately twice as efficient as gasoline engines.)

Direct injection gasoline engines are quite difficult to design, and Mazda currently makes the only such engine for automotive use (developed at a cost of $110 million) but expect to see others in the future as the price of gasoline continues to climb.

Another area subject to considerable research is pulse detonation. Pulse detonation is the most efficient way to burn fuel and results in the lowest emissions. What happens during the process is that a shock wave forms in the combustible mass and propagates outward at supersonic speeds igniting all of the fuel almost instantaneously and extracting all of the fuel’s available energy.

If it sounds like an explosion, that’s exactly what it is and therein lies the problem. Attempts to harness pulse detonation in reciprocating engines have always come to grief because of the stresses the shock wave places on the engine. Engine knocking is in fact a pulse detonation and we all known what that can do an engine.

Pulse detonation is actually much better suited to a rotary engine where the rotary device is moving continuously than stopping at dead center where it must endure the shock of the pulse. Pratt Whitney, the aircraft and industrial gas turbine manufacturer, claims to be working on a pulse detonation turbine, and two small startups, Quasiturbine, located in Quebec, and Phoenix Navigation, headquartered in Munising, Michigan, also claim to have developed rotary engines utilizing this principle.

Finally, there is a significant amount of research going on in the area of what are known as continuously variable transmissions which are able to vary gear ratios between the engine and wheels automatically over an infinite range of gradations so as to optimize power transfer. Such transmissions, called CVTs for short, offer the highest possible efficiency combined with the convenience of an automatic transmission.

Leonardo Da Vinci conceived the CVT at the beginning of the sixteenth century and a multitude of design variants appeared by the end of the nineteenth century. Since then dozens of different designs have been prototyped but commercial examples have been relatively few in number, largely due to durability problems. General Motors’ famous but problematic Dynaflow from the nineteen fifties is the by far the best known, but the biggest market to date for the devices is the snowmobile. CVTs are also used in tractors, motorcycles, and military vehicles.

Finally, we have electric hybrids, an area of fairly extensive research today. Hybrids, of course, go beyond the design of heat engine itself to include the generator and the motor but they necessitate modifications in the heat engine and they considerably augment its efficiency. Most of the research effort has to focus on the electrical portion of hybrid, however, because that is most in need of improvements. Expect breakthroughs in motor and generators in the future and probably in storage batteries as well.

In the next installment I shall consider the neglected category of external combustion engines of which only one type, the Stirling cycle engine, has received any significant degree of attention from the alternative energy community. I will certainly cover the Stirling but I will also say something about its neglected cousin, the Ericsson engine, and I shall even say something about the possibility, admittedly remote, of some slight revival of steam.


FatherofFour said...

Dan - I've added your blog to my sidebar list of blogs at

Engineer-Poet said...

Yvonne:  Would you mind expounding on your background a bit?  For instance, have you ever taken a course in thermodynamics?

Anonymous said...

Of course, even with direct injection engines, diesel has higher efficiency - while a very, very good gasoline engine MIGHT make 35%, a diesel can go as high as 40% in a best case scenario.

Yvonne said...

Thank you.

Dan Sweeney
(818) 954-0480

Yvonne said...

To engineer-poet

We've read the Carnot equations but we're basically self taught.

Dan Sweeney

P.S. Yvonne is the Web poster

Yvonne said...

To anonymous:

You're right about direct injection gasoline engines as compared to diesel. None that I know has ever equaled a diesel when it comes to efficiency. The really interesting area in diesel today as I see it is two stroke diesel which offers high energy density plus good fuel efficiency. I'll be writing about it in the future.

Dan Sweeney

Engineer-Poet said...

The problem I see with this blog is that you are neither engineers nor scientists, and you don't "smell" when numbers are funny or things don't quite add up. Thermodynamics is part of it, but not the whole thing.

I've found a number of errors in this and other posts, some of them substantial. If you intend to try to inform people, you have an obligation to get your facts right. If you can't do this yourselves, you should enlist outside help.

One example: The efficiency difference between Otto-cycle and Diesel-cycle engines is not at all due to direct injection of fuel, or even primarily due to the higher compression ratio of diesels. The biggest difference is caused by throttling of the air supply of Otto engines, which makes them work against a vacuum in the intake; the energy spent moving air from low pressure in the intake manifold to above atmospheric so they can go out the exhaust is called "pumping losses".  If you run an Otto engine at wide-open throttle its efficiency is quite close to a diesel; unfortunately, actually doing that presents great difficulties.

I could go on, but that should give you a hint.

Anonymous said...

Fine, great, super! Now build one and save the world (as if!)

Yvonne said...

Reply to Enginee-Poet

I'm aware of the throttling issue in spark ignition engines. Direct injection provides a solution by permitting fuel intake to be regulated independent of air intake thus reducing drag on the piston.

Engineer-Poet said...

You mean, direct injection allows charge stratification so that the fuel mixture around the spark plug is rich enough to ignite while the overall mixture is far leaner.  This still leaves you with NOx issues in the exhaust gas, and you can't use 3-way catalysts to aftertreat them.

You can accomplish some of the same things with the Atkinson cycle, short-cycling the intake stroke to reduce pumping losses.  VVT appears to be the way the auto industry is going, for exactly the reasons above.

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Terry said...

Among the new things that have interested me this year has been the design and build of a novell concept for a sterling type engine.
I have not finished the proto type yet but I wondered if anyone else would have built a similar machine.
My design is for a hybrid system. an electric motor drives a fan.
The fan sequentualy moves a contained volume of gas through two heat exchangers ; one hot ,one cold.
The movement of gas through the heat exchangers is controlled by a solinoid operated valve on the pressured inlet of the heat exchangers.
The solinoid is actuated by contacts attached to the con rod of the power take off piston.

The intention of the design was to increase the power available from low temperature energy sources and give more control over the heating cooling change over points during start up and loading.

I would be interested to hear of anyones comments on the idea

Anonymous said...

i have 2 rotary engine designs which might be of interest. One will run on sunshine easily. The other is a "four-stroke" internal combustion, with 3 moving parts.