CNG Compressor Los Angeles Area: Packages used to refuel CNG transit bus fleet, significant energy savings over electric driven systems

Diesel Progress North American Edition, Nov, 2001 by Debbie Low

While many companies have shied away from natural gas engine applications in Southern California because of strict emission requirements mandated by the South Coast Air Quality Management District (SCAQMD), one company has quietly developed a fleet of large horsepower gas-- engine driven compressor packages in the Los Angeles area to fuel compressed natural gas (CNG) transit buses while successfully passing all emission requirements.

Air quality control mandates issued by both federal and state governments began forcing the Los Angeles County Metropolitan Transit Authority (LACMTA) to replace its fleet of 2400 diesel buses with alternative fuel vehicles eight years ago. The MTA's fuel of choice was natural gas. Initially, one of the biggest challenges appeared to be adding infrastructure capable of supporting the second largest transit fleet in the country with equipment that could make the switch from diesel to CNG transparent to the end user. Issues such as finding equipment to meet emission requirements, maintain units economically and be reliable, soon required continuous focus.

Previously LACMTA built its own refueling stations with electric driven compressors. However, in 1998 it began outsourcing the construction and operation for each bus yard or division through a public-bid process that required outside companies to install, operate, maintain and own the facilities for a 10-year period. This process allows LACMTA to focus on its core business of running a transit operation and shifted the responsibility for the CNG equipment to the vendor.

In the past, electric driven compressors were favored because of their simplicity and they avoided all emission issues. In addition, electric drives handle the rigorous amount of starts and stops the compressor package incurs during a fueling period easier than gas engines. However, with the high cost of electricity in Southern California, they are very expensive to operate.

Salt Lake City-based Trillium USA, owned by Westcoast Energy Inc., headquartered in Vancouver, Canada, quickly made a name for itself in the CNG industry as a leader in large transit installations after it was awarded three separate divisions by the LACMTA. Each site was installed ahead of schedule and were compliant with all environmental regulations. The first site was completed in late 1999, the second in early 2000 and the third site went on line March 30, 2001.

The dramatic move by the LACMTA to depart from the traditional model of purchasing refueling equipment through a lowest acquisition cost approach forced Trillium to review not just the initial investment cost, but the 10-year life cycle expenses including consumables. spare parts, overhauls, and energy costs. One fact was self-evident. The energy required to run large horsepower compressors with electricity was more than twice the cost of running gas-engine driven compressors. Trillium elected to use gas as the principal energy source at a time when electricity appeared to be in abundant supply Since then, with the well-known electricity crunch in California, that decision has proven to be a good one.

Don Ott, LACMTA director, facilities maintenance said, "Trillium has designed fueling facilities that are state-of-the-art design and they perform better than any that have been previously built by the MTA. Trillium has shortened design and construction periods from previous installations as well as allowing us to get on line quicker. Trillium also has outstanding service after start-up and its maintenance record to date has far exceeded our expectations."

Trillium is one of a few companies to successfully pass the SCAQMD emission tests for CNG compressors. The first two LACMTA sites installed by Trillium both passed the required third party source test of its Caterpillar G3412 TAA engine rated 607 hp at 1800 rpm on the first attempt. The newest site will be tested later in the year.

Trillium has been an owner/operator of CNG fueling facilities in the Los Angeles area for two years. In addition to supplying CNG to LACMTA, Trillium supplies gas to smaller fleet vehicles at Los Angeles Unified School District, United Parcel Service and the fleets servicing the San Francisco Airport. Each LACMTA fueling site, or division, fuels an estimated 200 buses per night in a fueling period of eight hours. Each bus consumes between 40 and 90 equivalent gal. of fuel daily. Trillium is currently averaging fill times of less than five minutes.

Trillium operates three bus yards for LACMTA. Each yard uses three Caterpillar 607 hp stoichiometric engines supplied by Darr Equipment driving Ariel JGJ-4, 1280 hp three-stage compressors at 1800 rpm. They are equipped with noise-sensitive coolers manufactured by Air Cooled Exchangers Inc. Each compressor is controlled by FWMurphy Series 500A Selectronic Micro Controller and interfacing with Murphy Master Buffer/ Sequential Communicators at two sites and at the newest facility an Allen-Bradley SLC-5/04 System Master Control Panel with a PanelView 1000 keypad screen for monitoring and displaying shutdowns and temperatures.