As the use of liquefied natural gas advances toward widespread commercial application, the prospect of producing LNG locally at small-scale plants drawing from existing natural gas lines becomes increasingly attractive. The LNG research team at the INL is currently engaged in an effort to develop and demonstrate a small-scale methane liquefaction plant (production of 5,000 to 10,000 gallons per day). The intent is that the plant will operate in conjunction with an adjacent refueling station to supply motor fuel to buses and other LNG-powered vehicles.
One of the obstacles to widespread use of LNG as a vehicle fuel is the cost and availability of fuel. At present, LNG for commercial use in vehicles is typically produced by conventional refrigeration technologies (compressors and refrigerant loops) at large-scale liquefaction plants (peak-shaving plants, helium production plants, etc.). Conventional refrigeration technologies are well established, but the capital and operating costs are high for this kind of plant. Advanced refrigeration technologies are typically even more expensive to build, though less expensive to operate. Commercial LNG is shipped in vacuum-insulated tanks from the plant to the local filling station for dispensing. Purchase cost for LNG at a conventional plant varies from about $0.70 to $0.90 per diesel gallon equivalent, before taxes. Transportation costs run about $0.05 per diesel gallon equivalent per 100 miles.
The cost of the fuel could be reduced significantly, and the availability improved, by production at local, small-scale, low-cost liquefaction plants. The project described here will use a new technology, invented by researchers at the INL (patent pending). The design of the liquefaction plant will use off-the-shelf components where possible, energy inputs and moving parts will be minimized.
One of the advantages of the small-scale liquefaction plant is the local production of LNG at the location of use. Installations can have a fueling station adjacent to a liquefaction plant that supplies LNG to the station. Such an installation eliminates transportation costs and provides a continuous supply to the station's storage tank. Multiple stations can be located around a central liquefaction plant, with only minimal transportation costs involved.
Other identified applications for the liquefaction plants are to do local peak shaving, or provide a privately owned supply of LNG for localized distribution systems. Many small communities do not have access to natural gas; however, they can install a local distribution system and supply it with LNG brought in on trucks. A liquefaction plant can be owned by the community and located closer than normal large supply sources, thus saving on transportation costs.
Development and demonstration of the liquefaction plant is proceeding under the terms of a CRADA with Pacific Gas and Electric Company and Southern California Gas Company. The first demonstration plant will be installed in Sacramento, California, the second in Los Angeles, Califoria, and the third in Idaho Falls, Idaho. After successful demonstration, the technology will be licensed for commercial manufacture.