Headquartered within the south of France, near Nice, MDI has been promoting compressed-air engine technology more than a decade. The small, innovative company employs about 50 people, and is managed by its founder, Guy Nègre. In 2007, against all odds, the company signed its first partnership agreement with a major car maker, Indian conglomerate Tata.
This partnership will permit MDI to complete the development and optimization of its technology for the Indian market. Tata Motors is the company that acquired Jaguar and Land Rover from Ford at the start of 2008, and it is the maker from the $2,500 car. In its homeland, this large industrial group is the number one commercial vehicle manufacturer and also the number two for private vehicles. There are over four million licensed Tatas on the road today.
With this agreement, MDI should be able to thumb its nose at European automakers who’ve ridiculed their engine’s highly unusual features. There are few who believe that such a system could be an effective power source for a car, even though motors running on compressed air are definitely the norm for industrial power tools. Another stumbling block is the fact that air-powered cars, unlike air-powered tools, must carry along their own supply of compressed air, which includes resulted in numerous complications.
Changing minds through innovation
MDI AirPod (© Photo: Philippe Psaila)
Photo: Philippe Psaila
MDI been able to get around the limitations of ordinary air motors with an exclusive technology; their system limits the compressed air supplied in the vehicle’s tank with each cycle for increased vehicle range. Two major features differentiate MDI’s engine from any other air-powered engine.
First, the piston engine draws ambient air to fill its cylinders and injects a small amount of compressed air following the compression cycle to boost total pressure within the engine’s cylinder. After “inhalation,” the environment is warmed up. This further boosts the pressure within the cylinder, boosting power and gratification. MDI claims that its prototypes can travel 200 km with a tank of compressed air, which rivals that of a standard electric car.
Second, MDI’s air engine features a unique connecting rod system which improves the engine’s efficiency. Unlike the pistons of the regular gasoline-powered engine, that happen to be linked to the crankshaft by rigid connecting rods, the compressed-air engine’s pistons are connected by a hinged mechanical link that MDI calls a “crank rod”. This patented system stops the piston for a few milliseconds at the top dead center position – the limit from the travel – without interrupting the crankshaft’s rotation. This pause allows more time for pressure to enhance in the cylinder, even when the automobile is accelerating. The result is certainly a stable torque curve at any speed. Although air-powered engines are typically weak and small, MDI’s engine offers decent performance as its peak torque is generated at low engine speeds.
Compressed air: Method to obtain energy or storage system?
MDI AirPod (© Photo: MDI)
Photo: MDI
MDI is marketing its air-powered engine as an alternative to electric-powered cars rather than fossil-fuel powered vehicles. Although they may seem totally different (air v. electricity) these two “green” technologies share many things in common.
First, supporters of both engines claim the enhanced green factor, arguing that the power of their vehicle does not pollute and could (one day) be developed from the wind or the sun. However, unlike hydrocarbon, neither compressed air nor battery power is a supply of energy by itself. They are energy storage strategies as well as the energy they store originates from alternative sources, usually coal or oil-fuelled powerplants which can be not necessarily environmentally-friendly. The generation of electricity needed to run the car will not be as kind to the environment, even though the car may not emit any tailpipe emissions.
Second, this energy to power the car needs to be stored somewhere: One system requires large, heavy and expensive batteries and the other needs huge air tanks, limiting its application to small, lightweight vehicles. The range of either vehicle type is seriously compromised as soon as the greater demands are put on your vehicle (for performance, or range); fitting larger batteries or bigger air tanks can be quite a potential solution, but it would seriously reduce passenger and cargo-carrying abilities.Finally, there is the number one question that MDI’s detractors love to ask: “What is the reason for using electricity to compress air (an activity known to be ineffective) instead of using electricity to charge the batteries directly? “
A comparison of kilowatts and horsepower gives weight to this energy-efficiency argument. Compressed-air engine supporters argue that even if your technology seems less efficient on paper, the weight of the batteries required by electric cars limits their performance and leads to higher energy consumption for similar abilities.
The compressed-air car features a few advantages over the electric car. It takes less than three minutes to fill an aura tank versus six to eight hours to charge the batteries of an electric car. The compressed-air car also comes equipped with its own electrical compressor to recharge the vehicle in some hours only, simply by plugging it in. And it wins hands down within the electric car for air-con as the electric car uses a large quantity of its precious energy to drive an air conditioning compressor the vehicle while MDI’s car reuses frigid air expelled from the exhaust. If this cold, decompressed air – which happens to be clean and safe for passengers to breathe – was sent into the car, its occupants would freeze in just 20 minutes, MDI says that!
However, there are some drawbacks. The present compressed air engine is all about as noisy as one of the early diesels and its particular numerous loose parts do not bode well for reliability, bringing back fears of the piston engine. There is no comparison using the quietness and ideal reliability of electric engines.
Adding fuel to the equation
MDI AirPod with MDI founder Guy Nègre (© Photo: Philippe Psaila)
Photo: Philippe Psaila
Apart from the compressed-air engine – explained by MDI as a “mono-energy engine” – the corporation is refining the idea of a 2nd generation, “”dual-energy”” engine. The engine could be identical to the mono-energy version, powered by compressed air only when the automobile runs at low speed, but it would also have a combustion chamber to warm up the atmosphere before its injection, which would significantly raise the car’s power.
Since the fuel – or perhaps the energy adjuvant, as MDI calls it – would only be used to heat up the air, several other solutions which wouldn’t require any huge modification to the engine’s basic mechanics could be considered, from bio-diesel to hydrogen. With this system, MDI expects speeds up to 90 km/h with a fuel consumption of about 1.7 L/100km. This engine can even recharge its compressed-air supply while on the streets!
For the time being, MDI is planning the introduction of the AirPod, a car or truck whose size is about as small as its price (lower than $ten thousand), or its operating cost. In accordance with MDI, is futuristic and playful, this four-seater will not exceed 45 km/h and the design. It can provide an alternative choice to the problems of traffic jams and urban travel, although the AirPod won’t pretend to switch a regular automobile. This joystick-controlled vehicle could have its rear passengers facing backward. Large lift gates will serve as doors to the rear passengers, and will double up as a door and windshield for front passengers.