I think the future looks great! Where do i sign, i want one! Get a model T horn oouuuga and cruise.....

Very old idea. Air motors have been around for decades. Any steam engine could also be run on compressed air.

Overall efficiency of compressed air systems runs about 65%, give or take. When the air is initially compressed, it gets hot. While in storage in the tank, it cools. This is lost energy and cannot be recovered. It is interesting to note that the 65% efficiency is just about the same as that of electrical storage batteries.

Charon wrote on 07/12/12 at 05:16:49:


True, but carbon fiber compressed air tanks would cost 10% of what high-tech batteries would cost, they would last ten times as long, and weigh 1/4 as much,... so the energy storage situation for a vehicle would be much more efficient. Also, using solar panels to restore energy for compressed air at home would be more efficient and cheaper than electricity for the same reasons.

a solar powered stirling engine would be a better solution for generating compressed air.

Actually  I think the "storing energy as air" has a value, esp if NOT for a transportation.  But for those not willing to move to compressed air as a store of energy there is this:

http://www.youtube.com/watch?v=THOy-DAerGY

VRB: Vanadium Redux battery. Scales to any size, and lasts much longer than other chemical battery designs. Talks are to use this technology for power companies to store power for the grid! Thats pertty dern big!

Back to air. Someone had the bright idea to store not compressed air... but vacuume! As I recall the idea was to use wind energy to pump air out of natually occuring cave-like structures. Then during low wind, the vacuume would turn turbines as the air was drawn back in.


To me though it goes to political end.. the efficiency of the grid versus the security of a more distributed power generation grid. ... another topic for another forum..

Well I'll tell ya whut, a couple of advantages a scuba tank might have over a conventional battery are 1) no loss of energy by just sitting there.  Airtight = Energytight   and 2) the adiabatic heating/cooling of air that causes the energy loss on filling the tank could make for a nifty air conditioner.. just expand the air partially through an AC coil on its way to the engine.

I think the usually stated efficiency of delivering electrical power to your house is about 22%, from chemical energy in the fuel to electrical energy at your house. The overall efficiency of fossil fuel fired plants is about 30 - 33%, depending on the age and size of the  plant. That does not account for energy used in transporting the fuel from its source to the plant. It is estimated that a coal train on an "average" run burns the equivalent of 1 - 2% of its load. It isn't clear whether that includes the fuel used getting the empty train back to the mine. Nuclear plant efficiency is similar, but accounting for the amount of energy used to produce the fuel is much more difficult. A percentage of the generated electricity is wasted in line resistance, one reason why electric utilities like to build plants near the point of use. Funny enough, that 22% overall efficiency comes close to the efficiency gotten by burning gasoline in cars.

Thing about electric golf cars (current terminology is "cars" and not "carts" - "carts" being unpowered vehicles usually drawn by animals) is that they are purpose-designed machines. They are designed to go a few miles at low speed, and to be plugged in back at their shelter when not in use. That make them great for golf courses and compact residential areas, but not too good for actual commuting. Add a set of lights, brake lights, turn signals, and the range drops even more simply due to limited energy storage. Heaters or air conditioners can be forgotten completely.

Electric cars as originally designed over a hundred years ago were also urban vehicles. They were designed for a speed of 20 mph or so, and a range seldom exceeding twenty or thirty miles - enough to visit people and run errands in a small town. The problem then, as now, was energy storage. That confounded the likes of Henry Ford and Thomas Edison, and decades of their successors. The problem never was the motors or the controls - it was and is the batteries.

Air powered cars have no doubt been experimented with. Air powered trams have been used in mines for a long time, where distances are short, speeds are low, there is a considerable risk of fire or explosion, and air is conveniently available. The problem is the same as electric vehicles. There is a limited amount of energy available in a given sized air tank. To get more energy for either more speed or more range, bigger and heavier air tanks are required. Yes, carbon fiber air tanks can be made and yes, pressures can be higher. Yes, air tanks can be less expensive than batteries. I have (a long time ago) gone through the math involved in using air starters for diesel engines, including the size of tank (receiver) required, the amount of air required for a start, and the time required for recharge for another start attempt. Most of that would be applicable for an air-motor powered vehicle. By the way, given an air-powered vehicle, what would you use for a heater/defroster in cold weather?