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Transit-Based LPG Microturbine Rapid-Intervention Project,

Phase I

Project Objective
Two mass transit authorities (Island Transit in Galveston, TX and LADoT in Los Angeles, CA) experienced a number of problems with their propane (LPG) powered microturbine hybrid buses and considered project termination. ADEPT's goals were to: (1) intervene to promote the continuation of the projects, (2) ensure that the quality of LPG and LPG fuel in general were not blamed for problems encountered, and (3) facilitate the use of LPG in other similar microturbine applications.

Background Information
At the two project sites, on-board Capstone microturbines are used to charge batteries on hybrid electric vehicles (HEVs). The microturbine acts as a range-extender for the HEV by recharging the batteries during bus operation. These HEVs have ultra low emissions when operated on LPG. The microturbines are expected to be low-maintenance due to a modular design that encourages swap out service as well as a design that utilizes only one moving part.


Galveston Hybrid Electric Bus

Los Angeles Hybrid Electric Bus


Project Outcome
ADEPT, with the Propane Education and Research Council's (PERC) support, successfully conveyed to the microturbine manufacturer, bus/shuttle integrators, and the bus/shuttle operators the LPG industry's support for this pioneering effort. ADEPT conducted in depth site investigations in Galveston and Los Angeles to troubleshoot various problems. ADEPT conducted safety inspections and constructively addressed immediate safety concerns. Fuel quality analyses indicated that the LPG fuel was within HD-5 specifications. However, oily residue discovered in the fuel system was identified as a possible cause of fuel system performance problems. The Capstone microturbine fuel system inlet has specific pressure and temperature requirements. The LPG must be delivered to the microturbine in vapor phase. With the on-board fuel delivery system, there may have been instances during bus operation where pressure and temperature conditions would cause the LPG to re-condense to liquid phase.

A Phase II extension was recommended to address outstanding safety issues, continue to troubleshoot LPG fuel system problems, explore options to remove oily residues from LPG fuel, as well as reduce the probability of LPG re-condensing to liquid phase in the fuel system.

Duration: August - November 2001

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