compressed and requires a special high-pressure fueling station," (Moore, 92). "Natural gas fuel is stored on the vehicle in either compressed or liquefied form." CNG autos store at 16 to 25 MPa, and LNG's (liquefied natural gas vehicles) use pressures of 70 to 210 kPa and -160 C (Reed, 74). However, this installation of high pressure fueling stations is not an unrealistic idea; for example, Italy's countryside is inundated with high pressure natural gas fueling stations for their 250,000 natural gas powered automobiles. Many Italian citizens with CNG vehicles purchase compressors so that they may fuel their vehicles overnight. In the U.S., "natural gas utilities are expanding the infrastructure of delivery systems to make their fuels more available," (Valenti, 42). Finally, as required by law, many company fleets are converting or have converted to CNG fleets, proving that the change is indeed possible (Kisiel, 3). This renewable energy approach is feasible.Propane, or LPG (liquefied petroleum gas) is one other option similar to CNG but with less viability (due to vehicle manufacturers not for technical reasons). LPG has been used in vehicles since the 1920's and powers nearly 500,000 vehicles in the U.S. (Moore, 93), over 350,000 vehicles (Reed, 74). Conversions to LPG powered vehicles peaked in the early 1980's due to the gasoline price increase, (Reed, 74). Benefits include the benefit of reducing CO and hydrocarbon emissions, and the fuel is readily available in regions with natural gas or petroleum refining industries, (Reed, 74). "There is a substantial infrastructure in place and advanced technologies for storing and dispensing LPG," (Moore, 93). The cost of storage devices is also less for LPG than for CNG, or LNG, (Moore, 93).Propane does however have its disadvantages. It does not burn as cleanly as CNG. "In addition, propane vapors are heavier than air and tend to collect in low spots in explosive concentrations. Vehicle co...
