An 'air car' sure sounds like an environmentally friendly mode of transportation. After all, air is pretty clean! But it takes energy to compress air, so the question becomes, how do compressed air cars stack up against electric vehicles and hydrogen cars?
One example of a compressed air car is the Zero Pollution Motors (ZPM) MDI Air Car. This car is a hybrid which operates on compressed air alone under 35 mph, and uses gasoline to compress more air above 35 mph. The company claims their air car is "the worlds cleanest car" with "half the CO2 per mile as a Toyota Prius" at speeds over 35 mph. However, both of these claims are based on just the gasoline emissions and ignore the emissions associated with compressing the air in the first place. A bit sketchy.
So how much energy and CO2 emissions are associated with compressing the air? Well, according to the car's specifications, it has a 5.5 kW charger which takes 4 hours to fully refill the tank. This means it requires roughly 22 kWh to replaced the compressed air. The company also claims the car has an 848 mile range on both a full tank of compressed air and 8 gallons of gasoline, and that the gasoline emits 0.141 lbs/mile of CO2 from just the gasoline.
Over those 848 miles, it's also responsible for the 22 kWh of energy required to replace the compressed air. So how much CO2 is associated with that energy? Well, of course it depends where you get it from. According to the EPA, the average CO2 emissions from power generation in the US are 1.363 lbs/kWh. So on average, you're creating 30 lbs of CO2 emissions over those 848 miles, or a further 0.035 lbs/mile for a total of 0.176 lbs/mile of CO2. This is roughly half the CO2 emissions associated with a Toyota Prius. If the compressed air is powered by a more environmentally friendly energy source, it will produce even lower emissions. For example, Pacific Gas & Electric (PG&E) in California produces 0.52 lbs CO2 per kWh, which would bring the ZPM down to 0.155 lbs/mile of CO2.gas versorgerwechseln heidelberg
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