Greentech: Compression of gases for a cheaper and simpler hybrid

It is a hybrid Air, an experimental vehicle that the French automaker PSA Peugeot Citroen has been trumpeting as a model of energy efficiency. While some skeptics wonder that if the hybrid Air really is an innovative technology, the Peugeot and Citroen search cars powered by, you might be some of the most intriguing models exposed this week at the Geneva Motor Show. The show opens Tuesday for two days of previews press and runs through March 17.

Peugeot said that a compact as a Citroen C3 equipped with the technology, which combines the hydraulic drive with a conventional gasoline engine, will get about 81 miles per gallon in the city. It would be significantly better than the existing gasoline-electric hybrids like the Toyota Prius can do to stop traffic.

PSA Peugeot Citroen, the second largest manufacturer in Europe, after Volkswagen, said it plans to start rolling the Air hybrid cars by 2015 or 2016.

Like a Prius, the hybrid Air system recovers energy whenever the driver slows down or decelerates. But instead of capturing the kinetic energy of the car of slowdown with a generator that charges a battery, like the Prius, the hybrid Air system uses a reversible hydraulic pump. The pump compresses the nitrogen gas in what looks like an oversized scuba tank which also contains the hydraulic fluid; the next time the driver steps on the accelerator, compressed gas pushes hydraulic fluid, like a syringe, by a gearbox to turn the wheels.

The amount of energy stored in the nitrogen tank is low – equivalent to approximately five teaspoons of essence. While it is just enough to propel the car a few hundred metres until the gasoline engine takes over once again, when repeated during a day of driving in the city, these additional teaspoons of energy corresponds to the great improvement in mileage, said Peugeot.

The idea of using so-called hydraulic hybrid to power a car has been around for years. Peugeot prefers to call its technology 'air hybrid' because the energy is stored by compression of nitrogen gas instead of hydraulic fluid under pressure. In the U.S., Chrysler and Ford Motor each have studied the approach and the Environmental Protection Agency has encouraged research.

The United Parcel Service said dozens of hybrid hydraulic trucks to its fleet of alternative fuels. Other companies apply technology for garbage trucks, which, as vans by UPS are great, make frequent stops and can benefit from the recovery of the energy otherwise wasted in the heat generated by the brakes.

The Indian carmaker Tata has promised to produce a car powered only by compressed air, but uses a different technology, developed by Motor Development International.

Hybrid Air of 200 members team, headed by Karim Mokaddem, a Peugeot engineer, seems to move faster from one to a car manufacturer worldwide to provide this alternative hybrid technology to the production.

"The logic of a hybrid electric is completely different," Andres Yarce, another of the Peugeot project leaders, said at the technical centre of the company in Carrières-sous-Poissy, near Paris. With an electric hybrid, ' you let the car run for a few miles, have the engine cut off, and then click run silently on an electric motor, ' said Mr. Yarce. "It took a long time for people to understand that the hybrid Air works differently, but it gets the same results."

When the car is ready for the market, Peugeot plans to price at about $26,000.

Mr. Mokaddem said that the prize was intended to make the Air hybrid a viable option in emerging markets like China and India, where most gas-electric hybrids were too complex and expensive for local repair and maintenance operations.

Peugeot says it can undercut hybrids existing prices because his car does not require expensive battery and an electric motor, like a Prius, even if the hybrid Air uses a standard car battery. The hydraulic system adds about 220 pounds to the weight of Peugeot or Citroen classic. And because of the heat generated by the process of energy transfer, engineers have had to adjust the cooling system of the car.

The most obvious difference between the hybrid prototype Air and an ordinary car is the presence of two pressure tanks and a special gearbox that handles the transfer of energy between water and the 1.2 litre petrol standard engine. The designers of the system say that the configuration left room to keep a standard size trunk and fuel tank.

The accumulator or reservoir of nitrogen pressure, is about four feet long, with a volume of 20 litres, or about five litres and a maximum pressure of about 3,600 pounds per square inch. Breakage in a steel pressure tank could send metal flying, of course, but the design team said it has shielded against this install the tank under the floor and adding emergency exit valves. They also note that the nitrogen gas, which is nearly 80 percent of the air we breathe is not flammable.