As the use of liquefied natural gas (LNG) and compressed natural gas (CNG) advances toward widespread commercial application, the need for LNG and CNG refueling stations with low construction and operating costs becomes more urgent.
At present, the cost of a typical LNG refueling station is high, between $350,000 to well over a $1,000,000 for the mechanical systems alone. These costs compare unfavorably with the cost of a conventional gasoline station, at about $50,000 to $150,000. Several issues tend to create the large difference in cost. The primary one is the need for specialized equipment for storing and handling the cryogenic liquid (mostly methane) that constitutes LNG fuel. [The methane is maintained in a liquid state in a vacuum-insulated tank at a temperature of about -130 to -160°C (-200 to -260°F) and at a pressure of about 25 to 135 psi.]
The purpose of this research is to develop the avenues by which natural gas can be dispensed economically so that the commercial acceptance of LNG and CNG as vehicle fuels can be enhanced. The primary objective is to provide natural gas fueling stations designs that are comparable in cost and performance to conventional filling stations.
The “newness” of LNG as a fuel also contributes to the higher cost, as research must be conducted to develop new equipment and improved methods to handle the fuel. Finally, these issues must be resolved: “The cost will decrease when purchasing volume goes up,” versus “Purchasing volume will not go up until the cost decreases.”
The research is supported by public (U.S. DOE) and private (Gas Research Institute, Pacific Gas and Electric, and Southern California Gas) funding. Collaborations with other private sector parties will contribute funding for the construction and demonstration phases. The research will demonstrate new technologies and fuel management strategies to further establish natural gas as a viable, economical, technically sound, and environmentally friendly alternative to diesel fuel and gasoline.
The LNG/CNG refueling station will have the following features:
- Ease and safety of use and operation. Attendants and drivers with little or no specialized training will be able to operate the facility to refuel vehicles.
- Consideration of fuel management. The station will be able to dispense fuel at temperatures and pressures compatible with the vehicles' various fuel tank conditions.
- Capability to refuel warm and high-pressure vehicle tanks. The station will include provision for dispensing cold fuel into a warm vehicle tank or a tank at high pressure, without great inconvenience and without significant delays.
- Flow capacity. The station will be able to dispense fuel to heavy-duty vehicles at 30 to 50 gal/minute.
- Upgradeable. The station design will be modular in nature, allowing for economical configurations that can be used for small private operations to large municipal transit fleets.
Innovation and simplification will achieve the lower cost goals. For example, most current designs for LNG fueling stations use a high-volume, high-pressure pump to transfer fuel from the station tank to the vehicle tank. These pumps are very expensive, and their use contributes significantly to the high cost of conventional LNG refueling stations. To provide CNG fuel, a separate compressor station with associated mechanical and storage system is required at a cost roughly equivalent to the LNG stations.
INL researches intend to reduce the cost of the fueling station by using a design that avoids the need for the high-volume pump and uses the high-pressure pump to provide CNG as needed providing an integrated LNG and CNG fueling station.