Thread: [Question] How much methane would it take to lift 1lb?

Disclaimer: I'm by no means a professional scientist, and do not have any scientific backing for this idea, It's just pure creative speculation.

What if we could use a renewable gas lighter than air such as methane to raise objects, and then drop them onto some sort of friction plate to collect the kinetic energy from the fall?

Is this viable in your opinion? Would it be able to produce more energy per cubic foot than other uses for methane? Or is this a terrible idea?

Edit: useful calculator
http://hyperphysics.phy-astr.gsu.edu/hbase/flobj.html

Or, have the weight attached to a chain that turns a rotor on the way down.

The methane would not have enough buoyancy to do very much work. It would be trivial compared to the fuel value of burning the methane. And, once the methane has floated up, it would take energy to get it back down, equal to the energy that was extracted on the way up.

ETA: The density of air is about 1.15 kilograms per cubic meter. Methane is 0.66. This means that a cubic meter of methane in air would have a buoyancy of 1.15-.66=0.49 kilograms *2.2lb/kg=1.078lb. So you need a bit less than a cubic meter to lift a pound.

Another of my asides: As a teenager, I filled one of the U.S. Gov't. Surplus weather observation balloons, about 5 feet in diameter, with natural gas in our basement. The smell of the gas was quite noticeable as it permeated the balloon's pores, the material having been claimed to be Neoprene. I quickly realized that should anything suddenly ignite this thing, I would be dead! I flattened it enough to get it through the doorway and outdoors, the buoyant force being surprisingly great, and let it go; It disappeared upwards quite quickly, and as an afterthought, I wondered if my friends and I could get away with releasing one thusly, then shooting it while aloft with a .30-06 tracer round. I pictured the Chicago Tribune headline stating a huge explosion had taken place in the atmosphere! Some things we conceived were realized to be just too far out to take to fruition! (fortunately). I have never been sent away to jail, thankfully! jocular

Edit: Just realized my balloon was close to one cubic meter; got a calculator handy?

perpetual motion, again? repeat after me, "There is no free lunch", "There is no free lunch" etc...."

Originally Posted by Sealeaf

perpetual motion, again? repeat after me, "There is no free lunch", "There is no free lunch" etc...."

Depends on your definition of "perpetual". For example, if you purchase a cemetery lot, the contract may provide "care for the lot in "perpetuity". If your definition fits theirs, yer the guy to sell a big bridge to! jocular