Presentation on theme: "Alternative Fuels for Transit Buses Institute of Transportation Studies University of California, Davis Marshall Miller UC Davis June 3, 2008."— Presentation transcript:
Alternative Fuels for Transit Buses Institute of Transportation Studies University of California, Davis Marshall Miller UC Davis June 3, 2008
2 CARB Transit Bus Emissions Standards Original CARB regulations required very strict NO X reduction 2003 4.0 g/bhph 2004-2006 2.4 g/bhph (NO X + HC) 20070.2 g/bhph Later CARB modified regulations to be equivalent to US EPA 2007 –20091.2 g/bhph 20100.2 g/bhph
3 Fuel Technologies Battery electric Stoichiometric Natural Gas Diesel Gasoline Hybrid Hydrogen Enriched Natural Gas Fuel Cells (hydrogen)
4 Battery Electric Niche Markets Small buses + daily mileage < ~ 100 miles Lower energy storage No emissions (Zero Emission Bus), Meet CARB 2010 standard Problems Low range Long charge times New Battery Technologies (Lithium Ion) Significant range ( > 200 miles) > 7000 lbs > $100,000 - $200,000 (might be optimistic) Charge times still very high or MW chargers
5 Stoichiometric CNG Cummins Westport ISL G engine Only engine certified to CARB 2010 standard for NO X Stoichiometric operation with 3 way catalyst Concerns about high heat production causing maintenance issues
6 Diesel No current engine certified to CARB 2010 NO X standard Selective Catalytic Reduction (SCR) using urea Concerns Contaminants (O 2 or sulfur) in exhaust stream may reduce effectiveness Temperature control of exhaust is critical On board urea storage (space) Urea not required for proper vehicle operation, but necessary for NO X reduction.
7 Gasoline Hybrid ISE Corporation Certified at 0.4 g/bhph NO X Hybrid driveline increases fuel economy ~ 20-25% (roughly equivalent with diesel on energy basis) Ford V10 engine New engine (3 value V10) and better controls expected to meet 2010 standard (0.2 g/bhph) Diesel Hybrid Results vary considerably 25-50% increase in fuel economy ~ 40% NO X reduction
8 Hydrogen / Natural Gas Blends Blends with < 20% hydrogen called hythane ® Blends with > 20% hydrogen are called HCNG Hythane ® NO X reductions are limited but physical changes to bus engine are not required HCNG must be used to reduce engine out emissions to meet the CARB 2010 standard but requires engine modifications
9 Hydrogen / Natural Gas Buses Issues Range reduction (hydrogen less energy per volume than natural gas) Tradeoffs between emissions, power, efficiency Hythane ® (20% hydrogen by volume) NO X emissions reductions up to 50% Range reduction ~ 10-15% HCNG (30% hydrogen by volume) NO X emissions reductions up to 95% (meets CARB 2010 standards Range reduction ~ 15-20%
12 Hydrogen / Natural Gas Blend Buses (Transition Strategy) Present transit: Diesel fleets with CNG fleets growing Present Problems: emissions, global warming gases, imported fuel dependence Future Solution: Hydrogen fuel cell buses Problems 2 new technologies: Fuel cells and Hydrogen Infrastructure high cost, fuel cell lifetime questions
13 Hydrogen / Natural Gas Blend Buses (Transition Strategy) How do we get from the present to Hydrogen fuel cell buses? Hydrogen / Natural Gas Blend fleets significantly reduce emissions Hydrogen infrastructure Transit agencies can prepare for introduction of fuel cell buses when they are both affordable and available
14 Fuel Cell (hydrogen) Future of Transit Buses? Benefits Zero emission Bus (Zero greenhouse gas emissions if hydrogen produced renewably) Hydrogen can be produced from many feedstocks (natural gas, coal, electrolysis, biomass) and produced locally Future hydrogen cost ~ $2.50 - $4.00/ gallon gasoline equivalent Very efficient, quiet Central fueling (less infrastructure than light duty vehicles) Problems Cost Fuel cell lifetime Less interest than light duty vehicles
15 Summary Strict CARB regulations difficult to meet Many potential fuel technologies could play role Fuel cells (as with light duty vehicles) considered future of bus technology What fuel path(s) will ultimately be taken? What is timescale for various technologies?