Fuel cell tanks
The M1 Abrams tank is the main battle tank of the U.S Army and is really good at two things — blowing stuff up while not getting itself blown up. It's not so great at getting places efficiently. It takes almost 10 gallons of gas just to start it up and goes less than 1 mile per gallon burned. It gobbles up 12 gallons per hour just idling! A lot of that fuel is used to power the electronics that run a modern-day tank — the sensors, computers, lights and life-support systems. The Army is exploring the use of fuel cell technology that would eliminate the need for gas while producing a silent tank. The Army still needs to figure out how to create enough fuel to power the fuel cells, but that's another problem it’s working on.