How the Air Car Functions

Gasoline may seem essential today, but it's quickly becoming a relic of the past. The petroleum it’s made from is depleting, and the air pollution it causes is worsening. Moreover, people are no longer willing to pay the sky-high prices demanded by oil companies. Automakers are well aware of this, investing heavily in discovering and creating the energy solutions of tomorrow.

The hunt is on for the energy of the future, but what could it be? Traditional fuels like petroleum are becoming harder to come by, and car makers are shifting focus to greener alternatives like batteries. While these can be charged and stored in vehicles, some manufacturers believe that compressed air might be an even better solution.

Air? The concept of running a car purely on air may sound too good to be true. But if we could fuel cars with air, why would we need anything else? Air is everywhere, it’s endless, it’s clean, and, best of all, it’s free.

Unfortunately, air on its own cannot serve as a fuel source. First, energy must be stored in the air by compressing it using a mechanical air compressor. Once released, the compressed air expands, and this expansion can power engine pistons. The concept of utilizing compressed air to propel a vehicle isn't a modern idea—early air-powered vehicle prototypes date back to the mid-1800s, before the invention of the internal combustion engine.

At least one manufacturer believes it is ready to introduce air-powered vehicles to the American market. If all goes well, these cars may soon be available in the United States [source: Sullivan]. In the following pages, we’ll examine this innovative technology, explore why you might want to use it, and also consider some potential drawbacks.

How Compressed Air Can Power a Car

The laws of physics tell us that gases will naturally expand to fill any available space. A simple demonstration of this principle is inflating a balloon. The balloon’s elastic surface keeps the air contained, but once you puncture it, the air bursts out with such force that the balloon pops. Compressing gas into a confined space stores energy, which is released when the gas expands again. This fundamental principle is what powers an air car.

The initial models of air cars will feature built-in air compressors. After a drive, you’ll be able to park the car, plug it into your garage, and use the compressor to refill the vehicle's air tank with air from the surrounding environment. However, this refueling process is relatively slow and could take up to two hours to fully recharge the tank. If air cars become popular, air refueling stations will likely be set up at regular gas stations, allowing for quicker refills with pre-compressed air. At the pump, the refueling process should only take around three minutes [source: Cornell].

The first air cars will likely be powered by the Compressed Air Engine (CAE) developed by the French company Motor Development International (MDI). These vehicles will feature tanks that can hold approximately 3,200 cubic feet (90.6 kiloliters) of compressed air. The accelerator in these cars will control a valve that releases the air from the tank into a pipe and then into the engine. The expansion of the air will push against pistons, turning the crankshaft to generate enough power for speeds up to 35 miles (56 kilometers) per hour. Once the vehicle exceeds this speed, a motor will engage to operate the air compressor, compressing more air on the go to provide additional power. The air also heats up as it enters the engine, expanding and helping the car achieve faster speeds [source: Cornell].

Benefits of Air Cars

A significant benefit of using compressed air to power a vehicle is that it produces no emissions at the tailpipe. More specifically, air-powered cars will remain emission-free until they reach speeds over 35 miles per hour, at which point the car's internal compressor will activate to boost speed. The motor driving this compressor will require fuel, which produces a small amount of pollution. Some fuel (either eco-friendly biofuels or fossil fuels) will also be used to heat the air as it enters the engine. Nevertheless, this technology is a major improvement over traditional cars powered by internal combustion engines, which produce pollution at any speed.

Air cars are designed to be much lighter than traditional vehicles. With an aluminum frame, these cars will weigh less than 2,000 pounds (907 kilograms), a key factor in their fuel efficiency. This lightweight construction also contributes to better speed and longer driving range.

One of the key benefits of air cars is their low operating cost, which is especially appealing in today's world of unpredictable gas prices. Estimates suggest that these cars could achieve the equivalent of 106 miles (171 kilometers) per gallon, though compressed air isn't sold by the gallon. A more realistic cost estimate is that it might take as little as $2 worth of electricity to fill the compressed air tank. However, you will still need gasoline to power the electric motor that compresses the air while the car is moving [source: Cornell].

The price of these vehicles will also be relatively affordable. Zero Pollution Motors, which plans to introduce the first air cars in the United States, estimates a price of around $17,800, making these cars an attractive option for budget-conscious American consumers [source: Max].

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Challenges of Air Cars

Although an air car itself produces no emissions while running on compressed air in its tank, pollution is still generated during the compression process—both while driving and during refueling. As mentioned before, the vehicle’s air compressor will likely run on gasoline, and burning that gas will release pollution into the environment.

The air compressor at a refueling station will probably run on electricity, but whether or not that electricity produces pollution depends on the energy source. For instance, coal-powered electricity can create significant pollution, whereas cleaner sources like nuclear power or hydropower generate far less. According to Gas 2.0, an air car in the U.S. would produce around 0.176 pounds of carbon dioxide per mile, considering the typical mix of electric power sources during refueling. In comparison, a Toyota Prius Hybrid, which combines a battery-powered electric motor with an internal combustion engine, emits about 0.34 pounds of CO2 per mile. While the air car is not entirely free of emissions, it is still an improvement over many popular hybrid vehicles on the market [source: Nuccitelli].

The range of an air car could also be a limitation, depending on your travel needs. The distance an air car can travel without refueling is crucial, especially since few filling stations will have compressed air pumps initially. For short trips—less than 100 miles—you’ll be fine. However, the one-to-two hour wait for the built-in air compressor to recharge the tank could pose a challenge for long road trips. Zero Pollution Motors, the American division of MDI and the company most likely to introduce the first air cars in the U.S., plans to offer a car that can travel between 800 and 1,000 miles on a single tank of air and 8 gallons of gas [source: Cornell]. However, early prototypes have only been able to go around 120 miles, which is perfect for daily commutes but insufficient for longer journeys [source: Motavalli].

What happens if an air car is involved in a crash? After all, compressed air tanks can be dangerous. To minimize risk, the tanks are made from carbon fiber and are designed to crack rather than shatter in an accident. This controlled crack allows the 'fuel' to safely escape into the surrounding air. Manufacturers were concerned that air escaping from one end of the tank could cause a rocket-like effect and propel the car forward on a jet of air. To prevent this, the valve for the fuel tank is located on the side of the car, reducing this potential danger.

Despite these precautions, there are concerns that the lightweight design of air cars could make it challenging for them to meet the strict safety standards required in the U.S. This could potentially delay the launch of air cars in the American market. Other issues have also surfaced, which we’ll explore next.

Air Cars in the Marketplace

India's Tata Motors is expected to be the first company to bring an air car to market in the coming years. Their version will also use the CAE engine. Though Tata announced in August 2008 that they aren’t ready for mass production yet, Zero Pollution Motors still plans to launch a similar vehicle in the U.S. The FlowAIR models will be priced at around $17,800, and the company, based in New Paltz, N.Y., intends to start taking reservations in mid-2009 for deliveries in 2010. They aim to produce 10,000 air cars in the first year [source: Max]. MDI has also unveiled the AirPod, a new joystick-driven air car, which, despite a top speed of just 43 mph, is very lightweight and produces zero emissions.

Big auto manufacturers are keeping an eye on the air car market. If early models gain traction with consumers, these companies will likely develop their own air-powered vehicles. Currently, a few smaller companies are preparing to release air cars following the success of MDI-based models. These include:

At first, MDI's vehicles will be the sole air-powered cars available. However, MDI has reportedly licensed its technology to manufacturers in a dozen countries, so air cars will soon be accessible worldwide.