the gas turbine (which are used in thermal power plants due to its efficiency) outperforms pistonless rotary engines, however the production of compressed air is more energy efficient and so requires less wind power and infrastructure and also there is a loss of efficiency from gas turbine to generator and to electric motor. While batteries can somewhat maintain their voltage throughout their discharge and chemical fuel tanks provide the same power densities from the first to the last litre, the pressure of compressed air tanks falls as air is drawn off, reducing available power. Possible improvements It may be possible to store compressed air at lower pressure using an absorption material within the tank. Absorption materials like Activated carbon, or a metal organic framework is used for storing compressed natural gas at 500 psi instead of 4500 psi, which amounts to a large energy saving. Vehicles Production cars Several companies are investigating and producing prototype,s including hybrid compressed-air/gasoline-combustion vehicles. As of August 2017, none of the developers have yet gone into production, although Tata has indicated they will begin selling vehicles from 2020 and MDI's US distributor Zero Pollution Motors says production of the AIRPod will commence in Europe in 2018. Experimental cars and bikes In 2008, a compressed air and natural gas powered vehicle designed by engineering students at Deakin University in Australia was joint winner of the Ford Motor Company T2 competition to produce a car with a 200 km range and an estimated cost of less than $7,000. Australian company Engineair has produced a number of vehicle types - moped, small car, small carrier, go-cart - around the rotary compressed air engine created by Angelo Di Pietro. A compressed-air powered motorcycle, called the Green Speed Air Powered Motorcycle was made by Edwin Yi Yuan, based on the Suzuki GP100 and using the Angelo Di Pietro compressed-air engine. Three mechanical engineering students from San Jose State University; Daniel Mekis, Dennis Schaaf and Andrew Merovich, designed and built a bike that runs on compressed air. The total cost of the prototype was under $1000 and was sponsored by Sunshops (on the Boardwalk in Santa Cruz, California) and NO DIG NO RIDE (from Aptos, California.). The top speed of the maiden voyage in May 2009 was 23 mph. While their design was simple, these three pioneers of compressed air powered vehicles helped pave the way for French automaker Peugeot Citroën