A Bus Ride Toward a Zero Emissions Future
Posted on April 30, 2019 by Sudeshna Pal
Tags, Energy
Oregon’s first battery electric bus (BEB) is now officially on the road in the greater Portland area. I spent a little over two hours on a round trip in the bus in mid-April. The ride went smooth and, more importantly, clean!
TriMet is targeting a zero-emissions bus fleet by 2040. This was the first of the fleet; four more are scheduled to hit the road in the next few months. A fully charged bus is able to cover up to 80 miles. The battery-driven buses are powered by Portland General Electric (PGE) and are being built by New Flyer. PGE has agreed to provide and maintain the charging infrastructure. The bus in service is TriMet line 62, which is running 26 miles each round trip and is estimated to run an average of 63,600 miles per year.
At a market price of $1 million, the electric bus costs about twice as much as a similar diesel bus, however, the electric bus has an efficient energy use of 2.14kWh/mile which is equivalent to 15.75 MPG of diesel. The electric bus also has lower fueling costs, lower maintenance costs, and significantly lower carbon emissions. The switch to BEBs would earn TriMet higher clean fuel credits provided by the state. The estimated net present value (NPV) over the life cycle of TriMet’s targeted zero-emissions fleet, including replacement, expansion, and operation, is almost $1.8 billion. That amounts to a cost savings of approximately $69.1 million, or 3.7 percent of the total cost through the year 2055, in 2018 dollars. Additionally, there are significant reductions in social costs arising from lower emissions and noise. The NPV of these external benefits are estimated to be approx. $79.6 million over the lifetime of the fleet. That amounts to a social cost savings of about 100-140 tons of greenhouse gas emissions per year compared to a 40-foot diesel bus.
TriMet would be paying for its electricity use for these buses based on PGE’s Schedule 85 rate structure that applies to large non-residential customers. This pricing corresponds to PGE’s Time of Use rates. TriMet plans to schedule about 75 percent of its charging overnight, while scheduling the remainder of charging during the peak window of 6am-10pm. As part of its electric bus project, TriMet is also buying wind credits through PGE’s Clean Wind Commercial & Industrial program. That is a significant contribution to one of the country’s largest renewables programs.
The electric buses are a big step in the right direction. A 2016 EPA study shows that the transportation and electricity sectors each contribute about 28 percent of greenhouse gas emissions across the US. The collaboration between TriMet and PGE in bringing these buses into service, complemented by the generation of wind credits, will help mitigate their respective shares of GHG emissions. The BEBs also have significant noise-related benefits relative to traditional diesel buses.
In addition to the high capital costs of these buses, there are other challenges yet to be met. US experience with BEBs is limited. Hence, much remains to be learned regarding practical experience, maintenance techniques, and operational best practices. Electrical outages pose a major challenge, and PGE is assisting TriMet in avoiding these situations. Many of TriMet’s maintenance facilities are located near major PGE substations and transmission facilities. Since these are the first equipment restored during outages, the outages experienced by TriMet are of short duration.
The looming question as of now regards the projected useful life of the batteries. Currently the manufacturers project a 14-year useful life, which coincides with transportation property life of most US transit companies. TriMet, however, retires its buses after 16 years, to keep vehicle life cycle costs low. A long-term BEB adoption strategy would require batteries lasting 16 years; this remains to be achieved.
Acknowledgement: I would like to thank Robert Aldstadt for providing me with useful information on TriMet’s electric bus project.
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04/30/19 | 0 Comments | A Bus Ride Toward a Zero Emissions Future