Compressed Air Vehicle
How would you like to drive a car with zero emissions and only costs a few dollars to fill up? It may be possible in the near future with vehicles employing compressed air engines. The air compression is simply a way of storing energy similar to a rechargeable battery. Indian manufacturer Tatamotors is planning a limited production run of compressed air vehicles for use in India and a few other countries. Unfortunately, this particular car model will not meet U.S. safety standards primarily due to the construction of the vehicle. Moteur Development International (MDI), the French manufacturer of compressed air vehicles, is planning a larger vehicle for the U.S. market in 2010. The Mexican government has ordered 40,000 air powered vehicles to be used as taxis in Mexico City.
One advantage of the compressed air engine is the use of few moving parts, resulting in a light engine that is almost 100% efficient delivering power to the wheels. In contrast the traditional car’s engine only delivers about 16% of power to making the wheels turn. The rest of the energy is used to move all of the engine parts (pistons, cams), transmission, accessories or lost generating excess heat. Another advantage that compressed air has over other technologies is the environmental impact. There are no concerns regarding battery disposal compared to an electric vehicle since there are no batteries to power the car. The vehicles will remain operational longer since the engine has far fewer parts and few moving parts. The lighter weight implies that the tires will last longer, another disposal concern.
Although the compressed air solution sounds like a godsend there are some disadvantages. First of all, use of air compression to store energy is not particularly efficient. Second disadvantage is that the required air pressure is significantly higher than what is provided at a typical gas station for filling tires. Electricity is required to fill the tank and thus the carbon emissions problem is transferred from the vehicle to the electric power plant. It could take up to 4 hours for a refill at home through the electrical grid (although this could often be done during off-hours at night). Using a high pressure air pump this time could be reduced to approximately 3 minutes. It all comes down to availability of high pressure air pumps. The infrastructure is not there for mass use. Another problem is that the Air Car, like the HEV, suffers with low temperature usage. These cars likely won’t be used in cold weather climates. The final concern is the safety of driving around with compressed air tanks.
Auto manufacturers should be looking at combining air with other technologies (such as hybrids and stop-start) but nothing of this nature has come out of the laboratory yet. All in all a very interesting technology that is starting to be employed in selective niche markets.
Copyright 2008