Reproduced with kind permission of Dr Louis Arnoux from his e-book "Peak Oil, Climate Change & All That Jazz"

One of the most exciting point-of-use emerging technologies is that developed by Moteur Development International (MDI). MDI’s technology has received much publicity (because of the famous “air car”) without its importance being well understood.

Dr Louis Arnoux considers that the MDI technology,  has the potential to be used as a catalyst for the radical transformation of point-of-use energy systems as well as for the revolution of all forms of transport. That is to say, the MDI Technology enables the extremely cost effective harvesting of solar energy, mostly on the customer’s premises, and the close matching of the qualities and quantities of energy supply and use at their point of use. It has the potential to enable achieving the objective of shifting from less than 20% to over 80% energy efficiency in a competitive market-wide fashion. It is for this very reason that IndraNet Technologies has invested significant time and resources into assisting MDI in it’s development and commercialisation effort as part of their aim of developing a cost-effective converged ICET package for the emerging Post-Oil, Solar Era.

The MDI Technology encompasses four components: the MDI Compressed Air Engine, the MDI Power Generator, the MDI Transport Applications and the MDI Manufacturing Process.

MDI Compressed Air Engine

Unlike petrol or diesel engines, the MDI technology does not use any form of internal combustion. Instead, it incorporates four key breakthroughs.

  • First, the use of compressed air (or other gases or combination of gases) as energy carrier and storage medium. Compressed air is a clean, low cost and efficient form of energy storage. MDI uses pressures of around 300 bar in carbon fibre composite storage cylinders. As an energy carrier, compressed air is used at 30 bar or less to push pistons in the MDI engine.

  • Second, the primary energy input is taking place outside the engine by the heating of compressed air (or other gases, such as combustion gases).

    Physics tells us that heating a gas at constant pressure results in its expansion. In the MDI power block that incorporates the MDI compressed air engine, the heated, compressed air and/or combustion gases expand by a factor of three to five.

    Moving the energy input from inside an engine to the outside provides a wide range of substantial advantages. High temperature explosions inside the combustion chambers of internal combustion engines result in the production of nitrogen oxide gases (NOx), uncombusted volatile organic compounds (VOCs) and particulates (soot).76 Instead, in the MDI system combustion takes place in a steady state fashion at much lower temperatures (typically less than 900°C) in an excess of oxygen. The combustion is
    “lean and clean”, with near nil NOx, uncombusted particulates or VOCs, and if biofuels are used, it is also “green”.

    For mechanic buffs here, in essence, is how an MDI Engine works when configured to operate in a multi-fuel mode. With the inlet valve open
    5, compressed air at 30 bar pushes the smaller of the two pistons during its entire down stroke while the larger piston stays put at the top of the two piston chamber (it can stay like that because of the special configuration of the connecting rod). The inlet valve is then shut and the compressed air located on top of the first piston and in the active chamber common to both pistons now expands and pushes the second larger piston. When the latter is all the way down the pressure is about 1.2 bar and the air exhausts into the atmosphere on the upstroke of that larger piston.

    The larger piston is also associated with a small extension on top of it that functions as an air compression piston used to produce the initial volumes of compressed air that are then expanded by heating outside the engine. On the down stroke of the larger piston air is “breathed in” and on its upstroke the larger piston causes the air compression piston to compress the air intake to 30 bar and push it through the external heater/combustor where it will be heated at constant pressure.

    This heating at constant pressure expands the compressed air by a factor of 3 to 5 before it is injected on top of the smaller piston.

    The functioning of the MDI active chamber, as described above, achieves twice the amount of work produced in an ordinary internal combustion engine, for the same amount of compressed gas used to push pistons. Put another way, the combination of two pistons pushes on the crankshaft over 270 degrees rotation instead of just 180 degrees.

    The MDI active chamber also means that the engine’s torque curve is very flat, that is, the torque and engine efficiency both remain essentially the same from very low to high revs. This allows for much simplified clutch and gear box components in the case of automotive applications and substantially higher performance for point-of-use power generation applications.

    Furthermore, the heating of the compressed gas stream can be achieved through a wide variety of means including the combustion of fossil or biofuels, the recycling of waste heat from other processes, or the use of direct or indirect solar energy, all carried out in low cost, highly efficient and environmentally sound fashions. Ordinary engines are devoted to one type of fuel. A diesel engine only burns a diesel type of fuel. Most petrol engines can only accommodate a maximum of 10% ethanol without risking substantial damage. The MDI engine can accommodate any type of fuel. For example, bio-oils do not have to be refined into biodiesel. Ethanol can contain significant traces of water without this being a problem. This means that one can begin to use those higher efficiency engines well ahead of biofuel supply chains being fully in place and thus achieve a smooth transition from fossil fuels to biofuels.

  • Third, the MDI Active Chamber (incorporating two pistons per modular engine head).
    The MDI Active Chamber enables the energy efficiency of an engine, relative to an internal combustion engine, to be more than doubled (see figure 16).

  • Fourth, “Cool Combustion” using the Giant Magneto-Caloric Effect to drastically cool the air (or other gas) intake. The use of GMCE, dubbed “Cool Combustion” by MDI, aims, when implemented, to achieve further substantial energy efficiency gains. Much less work is required to compress to 30 bar the substantially cooled air. The drastic cooling of the air also substantially reduces the temperature of the primary energy input at the level of the heater-combustor to below 350°C. This means that biofuel requirements are greatly reduced. It also means that a wide range of other sources of relatively low-grade heat can be used, including the advanced forms of thermal solar.

The fully configured MDI engine (as diagrammatically opposite) combines the four above breakthroughs with the use of heat exchangers enabling solar energy inputs from both direct thermal solar and also from the ambient heat stored in the atmosphere (as we have seen earlier, this is the largest source of solar energy on Earth).

The MDI Active Chamber alone results in around 40% energy efficiency.

The integration of the Cool Combustion and solar heat exchangers are expected to increase efficiency to over 80%. Efficiency here means energy output versus purchased energy input. Those high efficiency levels do not contradict Carnot Cycle maxima since the MDI power block combines a compressed air (or other combustion gases) engine with a GMCE heat pump (or more specifically an “entropy pump”). In this configuration, the system extracts and mobilises solar energy stored in the atmosphere as ambient heat, hence the label of “solar augmented cool combustion”.

The implementation of solar augmented cool combustion, in commercial versions of the engine, offers the prospect of a drastic reduction in fuel requirements. For vehicles, the prospect is a progressive reduction in fuel uses from the present level of around 2.5 litres per 100km in the current engine model down to 1 litre per 100 km or less through a planned series of new engine releases and upgrades.

MDI Power Generator

MDI has also developed a variable speed point-of-use power generator designed to be fully integrated with its advanced compressed air engines.

The generator makes full use of the near constant torque and efficiency of the engines at a wide range of rotation speeds. The electronics operating the system sense the point-of-use power demand and power the generator up or down to constantly match that demand. This means that only the minimum of fuel required is used at any time.

Through a series of product and service releases, this technology has the ability to shift domestic, commercial and industrial energy costs from current retail costs in the order of AU$0.15 to $0.20 per kWh to below AU$0.10/kWh and then to substantially below AU$0.05/kWh in parallel with a progressive shift towards 100% solar energy as the primary energy source and 100% sustainable outcomes. Similar orders of magnitude also apply to the use of the MDI technology for land, sea and air based transport.

Reproduced with kind permission of Dr Louis Arnoux from his e-book "Peak Oil, Climate Change & All That Jazz"

Compressed Air Engines
Thermodynamic Cycle

MDI Compressed Air Engine
  • Based on the new MDI thermodynamic cycle.

  • External heat source combined with compressed air as the energy carrier and storage medium.

  • Air storage pressure 300 bar, engine operating pressure 30 bar.*

  • Efficient, clean and clean external combustion, multi-fuel capable, enables
    competitive use of biomass fuels and direct thermal solar.

  • Surplus power used to recharge the compressed air storage.

  • Overall energy efficiency more than twice that of internal combustion engines and
    capable of reaching over 70%.

  • Enables impressive cost reductions for manufacture, operation and maintenance of low cost, zero emission vehicles and environmentally sound distributed power generation.

This compressed air engine reached international recognition in February 2007 when Tata Motors Ltd of India announced it had concluded an agreement with MDI to apply the MDI technology to its Indian markets, corroborating that the MDI technology has the potential to open up the way to the rapid and highly competitive commercialisation of alternatives to oil and other fossil fuels for electrical power and transport.

The MDI Engines are protected by many patents registered worldwide. They consist of an active chamber and are made up of modules of two opposing cylinders. These modules can be coupled to make groups of 4 or 6 cylinders for a wide range of uses from 4 to 75 hp in the following applications:

  • MDI AIROne and AIRCity Clean Cars

  • The MDI AIRMulti Urban Transport System

  • Electricity Power Generators and Emergency Generators

  • Tow Tractors, Pallet Trucks and Hoists

  • Agricultural Tractors

  • Outboard Motors

  • Light Aircraft Engines and APU units

Based on this new Technology, MDI is now in the process of developing a “thermodynamic concept” that will enhance these results even further, over the next ten years, thus initiating a genuine energy revolution.


*Tyre pumps 1 to 3 bar, Scuba tanks 150 to 200 bar, Air Car tanks 300 bar - hence the need for special air compressors

MDI Factory in Carros, Nice, France where all research & Development is taking place

MDI Compressed Air Engine, Multifuel External Burner Tests

MDI Factory, Nice France, January 2008

Test Engine Electronic Monitoring of Tests

Louis Arnoux & Guy Negre

Watch Videos and read the explanation on
Saturday January 12, 2008 By Pierre Thebault, CARROS, France --

In an interview with Guy Nègre he explains - A car that runs on air?

What seemed like a pipe dream may soon become reality, as Frenchman Guy Nègre hopes versions of his compressed air car will be produced in India this year by Tata Motors.

It follows a 15-year quest for backers for his invention.

Nègre believes the time is right for his design with oil prices at record highs and pressure on carmakers to improve the fuel efficiency of their vehicles.

"It is clear that with oil at US$100 ($130) a barrel this will force people to change their use of fuel and pollute less," Nègre said at his firm Motor Development International (MDI), near Nice in the south of France.

"My car is zero pollution in town and almost no pollution on the highways," he added, saying the vehicle could travel 100km at a cost of €1 ($1.88) in fuel.

The former Formula One motor racing engineer's invention depends on pressurised air to move the pistons, which in turn help to compress the air again in a reservoir.

The engine also has an electric motor, which needs to be periodically recharged, to top up the air pressure.

The bottles of compressed air - similar to those used by divers - can be filled up at service stations in several minutes.

The latest versions of the cars - MDI made an entire series of prototypes of engines and vehicles - also include a fuel engine option to extend the car's range when not in reach of a special power plug or service station.

Tata, India's largest carmaker with revenue of US$7.2 billion in its last financial year, concluded a deal last year investing €20 million  .Pre-production in India is set for this year, Nègre said.

The vehicle, protected by some 50 patents, will cost €3500 to €4000. Using composite materials, it will weigh no more than 330kg and its maximum speed is 241km/h.

"The lighter the vehicle, the less it consumes and the less it pollutes and the cheaper it is. It's simple," Nègre said.

He aimed to set up mini factories in regions where the car is used.  "No transport, no parts suppliers. Everything will be made at the place of sale in production units that can make one car per half hour," said Nègre.

"That is more profitable, more ecological than the big factories of the large carmakers." MDI Air Car will hit the roads of India and Australia first, France will have to wait until 2009

It's a whole new way of thinking about energy!
by Sudden Disruption - Saturday, January 19, 2008

Amazing New Air Car - It's NOT About the Air!

And it's not even about the car!

Every now and then an idea comes along that will change the world - and gets mostly ignored. Some of you have heard me talking about this new air powered car from MDI (Moteur Development International) in France which is now to be manufactured by Tata Motors of India.

MDI did a press release a few weeks back and it was handled like, well, another press release. The automotive press paraphrased a few paragraphs, but I wonder if they actually THOUGHT ABOUT what they wrote?

And when Tata Motors introduced their more conventional yet inexpensive Nano at the Detroit Auto Show last week, it got amazing coverage, but not ONE mention of this new air car to be manufactured by the very SAME company!

The highly touted Tata Nano is a cute little bug that will get more than 50 MPG - cool. But the MDI OneCat which is about the same size will go more than 20 TIMES farther on the same gallon of fuel! Did no one actually READ the spec sheet on the OneCAT?

To be fair, the objective of the Nano is low price, not mileage. And the OneCat is much lighter, which helps, but surprisingly, that's not the key to it's mileage advantage. Here's how they do it...

As almost everyone knows, the standard internal combustion engine is only about 30% efficient under the very best of conditions. This means 70% of the energy in a gallon of gasoline leaves the car as wasted heat.

The only heat that produces power is that narrow band of highest temperature that causes rapid expansion of air when the spark plug fires. Once the piston reaches the bottom of it's cycle, all the lower temperature energy from that cycle is wasted and must be pumped out the exhaust pipe.

If you add MORE heat at the point of ignition (higher octane), you get more power. But Newton and his second law of thermodynamics limits us from using any of the heat BELOW the temperature of ignition. THAT is the primary reason for the inefficiency of the internal combustion engine. But what if we COULD use ALL of that heat?

CAT - Compressed Air Technology

Guy Nègre of Formula 1 fame and his company, Moteur Development International have spent the last 14 years developing a new type of engine for automobiles.

Compressed Air Technology has been described as using air as fuel, but that's not quite right. The air works more like a battery. It actually uses a carbon-fiber air tank with up to 300 times normal atmospheric pressure driving a piston to give the car a range of 100 Km. You can think of this system as a standard compressor motor and air tank - except it's running backwards. The air tank drives the compressor, instead of the other way around.

So far, no big deal. Any advantage is a matter of strength, weight and volume per unit of energy stored in the "battery" - the carbon-fiber tanks helps some. But if a short range compressed air car is all they had, it wouldn't be very impressive. The next detail is the key. When you think about it, you'll discover it's the biggest advancement in thermal energy extraction since the invention of the Otto-cycle in 1860! It effectively uses "wasted heat".

Bi-Energy Breakthrough

Guy Nègre’s brilliant innovation is to add a small fuel burner between the air tank and the motor. The heat from this burner extends the range for the compressed air tank by increasing the pressure of the air even more on it's way to the motor. Properly insulated, this burner could approach 100% conversion efficiency of the burned fuel. Here's the reason...

Small amounts of heat are not enough to turn over a reciprocating motor. But when you add a compressed air tank, it provides a pressure bias great enough to drive the motor on it's own. Now add the burner. Per the gas laws, the pressure increase is proportional to the heat added - it doesn't require a critical temperature of ignition! You could run it tepid or boiling - ANY heat adds power. It's just a matter of how much.

If you double the burn rate, you'll double the added expansion. Since there's no point of ignition, there's no critical temperature before this energy is extracted. ANY heat added by a burner (or other source) will simply add proportional expansion and energy extraction. Theoretically, most of the energy from a gallon of gasoline (or stack of firewood) could be used to drive the motor.

Check the spec sheet above. I assume these are actual measurements. The OneCAT will go 100 Km on air alone, but another 700 Km on only 1.5 liters of fuel! That works out to almost 1,100 MPG!

More Than JUST an Amazing New Car

MDI has a good chance of creating an amazingly efficient little car, and that's cool. But what's REALLY exciting are all the other potential industrial applications.

Considering generation and line losses when producing electricity, it may even now be more efficient to run Bi-Energy motors at the site of the application instead of buying electricity. Or we could boost power from solar heating. Or hot sewer water for that matter! ANY source of heat could be used. It's just a matter of degree and effectiveness. Any of a thousand sources of wasted heat can now be used.

OK. You'll still need electricity to provide the compressed air bias, but the rest of the energy would be more efficiently extracted - the hotter, the better. What about recycling the heat from air conditioners to drive their OWN motors? I'm not talking about perpetual motion here. There's no free ride. It's just that the heat is no longer has to be totally wasted. This approach provides an excellent possibility of dramatically increased efficiency in anything that needs a rotating motor and has wasted heat available. (Note - MDI was WAY ahead of me - I just found this link on their site... Further Applications - WOW!)

These ideas are worth more than just a press release. We need a new college of engineering at every university!

It's a whole new way of thinking about energy!
Reproduced with kind permission from 

Back to Top

Home  Energy  Solar Energy   Sustainable Energy  Alternative Energy   Sustainability  Electricity Generation  Resources  Plan B
  IT Technology    Distributed Power Generation    Intelligent Power Networks    IndraNet Minder   
Transport       Broadband 
  MDI Technology  MDI Update  MDI Archives     Peak Oil  Coal   Nuclear     Comments   Media Comment  Historic Comment 
    Articles     Media     About Us   Links   Site Map