JMU AFV Lab Blog

Came across this item in the Science Daily newsletter I get. At first glance, it would seem to be a simple solution to the problem of efficient vehicle propulsion. The concept is to use compressed air to store energy instead of a battery as in a conventional hybrid vehicle. The curious twist here is using the compressed air to assist the conventional internal combustion engine by either direct pressure on the pistons or as a turbocharger. The theory seems to have merit; compressed air is as viable a means of storing energy as a battery and turbocharging can drastically improve the efficiency of an ICE. However, my personal experience with compressed air as a means of energy storage and transfer is that it is highly inefficient. There is quite a bit of heat generated when air is compressed. After all, a diesel engine depends upon the same heat of compression to ignite its fuel. Shop air compressors require substantial cooling fins on both compressor heads and on connecting piping and large fans to keep compressors from self destructing. And shop air is usually only about 120 psi or so. All this heat that must be expelled is lost energy. As a practical matter, I am skeptical of being able to design a compressor and pressure storage tank with enough capacity to overcome this heat loss and be practical and still be lighter than the electric motor, generator, and battery of a hybrid like the Prius or Escape.

Source: http://www.sciencedaily.com/releases/2009/01/090131113216.htm

Saving Gas: Pneumatic Hybrid Engine Is Much Cheaper Than Electric Hybrids And Almost As Economical

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Physics laboratory technician Till Coester works on the new hybrid engine being checked thoroughly on the test stand. (Credit: Photo: P. Rüegg / ETH Zurich)

ScienceDaily (Feb. 4, 2009) — A pneumatic hybrid engine could be used to power vehicles in the future. The benefit of this technology: it is much cheaper than today’s electric hybrids and almost just as economical.

The Japanese automobile manufacturer Toyota has built a car, the “Prius”, which is seen as a concept for the future. It uses an electric hybrid engine to save fuel while still offering the usual drivability standards. However, this vehicle has a serious disadvantage. It is expensive and is unaffordable especially for consumers in up-and-coming countries such as China and India that are increasing rapidly their mobility demands. In addition, the battery needed by the electric hybrid as an energy storage device is heavy and expensive. Last but not least, the technology in the coupling between the gasoline engine and the electric drive is very complicated.

Simpler and cheaper

This is why Lino Guzzella, Professor of Thermotronics, does not think the electric hybrid is the only solution. As an experienced engineer, he therefore looked for an approach that was simpler than an electric hybrid but remained affordable even for people with less purchasing power. Guzzella explains that “The apple must be ripe but still hang just low enough to stay within reach.” The ‘fruit’ ripening in his group is the pneumatic hybrid drive. The concept is simpler than that of an electric hybrid: the new hybrid engine has a compressed air tank connected to the engine instead of a battery unit. When required, e.g. when starting from rest or after changing gear, compressed air flows into the engine through an electronically controlled valve. If fuel is also injected, the engine responds quickly. Although the system used to control the valve is also technologically complex, this challenge can be mastered nowadays thanks to powerful algorithms and computer systems.

The compressed air supply also allows the engine constructors led by Lino Guzzella to achieve extreme downsizing. Conventional car engines can have peak powers of 150 hp or more, but usually need no more than 30 hp for everyday driving. Downsizing the engine halves the number of cylinders from four to two. This also halves frictional losses and increases the engine’s average efficiency. To keep the maximum power and thus satisfy the consumer’s drivability demands, the engine is highly supercharged by a turbocharger – which exploits the exhaust gas enthalpy as an energy source, and which boosts the to the desired levels..

Efficiency up by a third

Initial tests on the test stand in the ETH Zurich Machinery Laboratory show that Guzzella and his group are on the right track. They were able to increase the engine’s average efficiency in the European Test Cycle from 18 to 24 percent. This corresponds to a fuel saving of one third. Energy savings of up to 50 percent are achievable in purely urban traffic, because the engine can pump air into the compressed air tank during braking, thus recovering the kinetic energy.

Although the fuel saving achieved by the pneumatic hybrid is not as large as that of an electric hybrid, it still amounts to 80 percent of the latter. In return, the price-performance ratio is distinctly better. So good, in fact, that Guzzella can imagine the pneumatic hybrid also being suitable for use in poorer countries. He estimates the additional costs compared to a conventional gasoline engine to be approximately 20 percent. On the other hand, the additional costs for an electric hybrid are calculated to be at least 200 percent.

Motor manufacturers interested

The new engine concept has aroused the interest of several major motor companies and automitive suppliers, who have obtained information on-site. Some of the ideas of the new concept have already been patented. Only the financial crisis and the global recession worry Guzzella slightly. He says that these are difficult times in which to launch a new drive concept. Nevertheless, he is convinced that he will find people interested in adopting this system, since no other technology is on the horizon that could replace the internal combustion engine, even in the next two decades. This is why the way leads via hybrid concepts, which remain affordable while retaining the advantages of a gasoline or diesel engine.

Source:  http://www.sciencedaily.com/releases/2009/01/090131113216.htm

Saw this blog entry this morning and thought it made some interesting points. Check it out at http://gas2.org/2008/09/30/volt-over-tesla-series-and-plug-in-hybrids-more-likely-to-be-game-changers/. Especially scroll down and look at the comments others have already made.

Volt Beats Tesla: Series and Plug-In Hybrids More Likely to be Game Changers
Written by Andrew Gilbertson
Published on September 30th, 2008
9 Comments
Posted in Engines, Hybrid-electric EVs, Plug-in hybrid EVs

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Editor’s Note: This is a guest post by Andrew Gilbertson who is a 2008 graduate of Vermont Law School.
A senior economist at the Argonne National Laboratory has come to an interesting conclusion: vehicles that rely on internal combustion engines are superior to electric vehicles in terms of what consumers would buy and what would save significant fuel.

Even though Tesla is delivering their cars to consumers several years before the Volt hits the show rooms, from the perspective of Dan Santini, you and I are more likely to get our hands on Volt-style vehicles first.

Some of the main obstacles that stand between us and pure EVs were identified at the 1st International Conference on Advanced Lithium Batteries for Automotive Applications, sponsored by the Argonne National Laboratory (where Dan Santini works).

First and foremost, the cost of the batteries boost vehicle prices too high for the average consumer. Recharging time, coupled with the lack of a national system of quick-charge stations, would make the vehicle unattractive to most consumers who want the freedom to travel across the country without long stops for recharging.

The Volt, with its series hybrid design, reduces the importance of these two concerns. By relying less on batteries, the cost of the batteries becomes less of a factor, while having a combustion engine that uses an established distribution system as a backup gives the owner the freedom to drive wherever they want.

It seems to me that more car makers should read the writing on the wall and go the series hybrid route (apparently, some are).

Even though series hybrids might not get better mileage right now, it should be obvious that at some point an energy storage technology will be developed that will be cheaper, denser, and cleaner than gas or diesel. When that time comes, the car makers that can simply replace the combustion generators with the new storage technology will be way ahead of the ones who haven’t yet developed a electric drive system.

I saw this article in ScienceDaily and was fascinated by it. (For more on this idea, go to this article at greencarcongress.com.) It seems like such an “elegant” idea to generate electricity for a hybrid vehicle. Being the questioning person I am, I immediately wondered why they would use permanent magnets instead of an electromagnet in the core of the “alternator.” After all the alternator in modern motor vehicles uses a small wire wound electromagnet as the “rotor” and a relatively larger coil as the “stator” to produce electricity to recharge the battery and provide power for electricity needs of the vehicle. These alternators use slip rings with carbon “brushes” to transmit voltage to the rotor to energize it. In this “Linear Alternator,” instead of rings, linear strips of metal on the connecting rod with brushes attached to the case could energize the coil.  Of course proper orientation of the moving coils and their magnetic lines of flux relative to the orientation of the stationary, current producing, coils would have to be taken into consideration.  My opinion is that the engine would have to be “fatter” in the alternator section to be more effective as an alternator.  What do you think?  (I can see this as a future project for the AFV Lab.)

free-piston-linear-alternator

ScienceDaily (Sep. 17, 2008) — In an advance toward introduction of an amazing new kind of internal combustion engine, researchers in China are reporting development and use of a new and more accurate computer model to assess performance of the so-called free-piston linear alternator (FPLA).

Their study of the FPLA, which could provide a low-emission, fuel efficient engine for future hybrid electric vehicles, is scheduled for the Sept. 17 issue of ACS’ Energy & Fuels, a bi-monthly journal.

Qingfeng Li and colleagues point out that the FPLA has only one moving part and is an engine designed to generate electricity. In the device, a piston in a cylinder shuttles between two combustion chambers. Permanent magnets on the piston generate electricity by passing through the coils of an alternator centered on the cylinder. The engine can burn a variety of fuels, including natural gas and hydrogen, and seems ideal use in a future world of climate change and possible fossil fuel shortages, they suggest.

Their report describes development of a better computer model to evaluate performance of the FPLA and guide engineers in construction of the engine. Results of their initial simulations showed that the FPLA could accelerate three times faster than other internal combustion engines and burns fuel in ways that minimize air pollution. “It is an environmentally friendly power source for the future,” the report concludes.

Journal reference:

1. Li, Qingfeng, Xiao, Jin, and Huang, Zhen. Simulation of a Two-Stroke Free-Piston Engine for Electrical Power Generation. Energy Fuels, 2008; DOI: 10.1021/ef800217k

Also see: http://www.greencarcongress.com/2008/09/modeling-a-free.html

This item came to my attention this morning; I have excerpted the first few paragraphs.  To read the article, go to http://web.mit.edu/mitei/research/spotlights/slash-gas.html

It’s feasible—but challenging on many fronts

How much gasoline would the nation save in the year 2035 if lightweight hybrid and plug-in hybrid vehicles dominated the marketplace? More than 68 billion gallons, or about half the fuel currently used by today’s vehicles.

Detailed analyses in a new MIT report demonstrate that such changes are feasible. Indeed, the report concludes that over the next 25 years the fuel consumption of new vehicles could be reduced by 30-50 percent and total U.S. fuel use for vehicles could be cut to 2000 levels, with greenhouse gas (GHG) emissions cut by almost as much….

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