Tata Motors hopes to release its compressed-air car in India by August.

Air-powered cars have been on the cusp of reality for more than a century. Sure, compressed air is a clean fuel, but it’s not efficient enough to power a car engine that will take you very far or very fast.

Here’s the gist of how it works. The driver steps on the accelerator, opening a valve that releases compressed air into the engine. The air expands, pushing against the engine’s pistons and turning the car’s crankshaft. Unfortunately, air power will accelerate you only to about 55 kilometers per hour.

Tata Motors may have dealt with this problem by adding a small gas motor that kicks in at 55 kilometers per hour. Tata plans to deliver its air-powered MiniCAT, which stands for Compressed Air Technology, to customers in India by August, according to the Australian Web site The Motor Report. They claim that it’ll cost just $2 to fill the air tank, and that a full tank lasts about 300 kilometers. Of course, they also said the car would be ready in 2009.

Given the history of air-powered cars, let’s hope Tata’s plans for this summer aren’t just a lot of hot air.