By David Warren
With a battery-electric bus, reducing emissions and greenhouse gases in our communities is the ultimate goal. Pilot programs for electric buses are being planned at small to large transit fleets across North America. Each opportunity for electric buses has unique considerations when it comes to the operating duty cycle and transit service characteristics.
Battery electric buses have inherent challenges compared to diesel or CNG buses. They are typically heavier, more expensive, and require unique infrastructure to cover the same range with the same passenger load carrying capability as a non-electric bus. With adequate planning and analysis, the added capital costs for electric buses and infrastructure can be offset by operational savings and funding strategies to ease the impact of the incremental upfront costs.
The following are some considerations and tips for the early planning of an electric bus deployment:
Range
Battery electric buses ranges are tested by the Federal Transit Administration (FTA) test protocol which includes three types of duty cycles – central business district, arterial and commuter routes. A limitation of the FTA range test is the exclusion of heating and air conditioning (HVAC) energy loads; a very significant factor in hot and cold regions. Additionally, range should be calculated using “useable battery capacity;” typically 80-90 percent of the manufacturers rated battery capacity. And finally, gradeability and the number of stops on the route will adversely affect range. Consult the bus manufacturer on the energy consumption for the specific application and routes under consideration. All of these variables can be simulated in computer models to more accurately determine the real-world range capability of the electric bus.
Passenger load carrying capability
Passenger carrying capability is determined by the number of seats on the bus plus standees. The number of allowable standees is based on the available floor space while not exceeding the gross axle legal load ratings. The latter becomes a major challenge on an electric bus, even with the most advanced next generation automotive batteries on the market. It’s important to have the bus manufacturer conduct detailed passenger load weight studies to determine if the electric bus will carry the same number of passengers as the CNG or diesel bus it’s replacing.
Energy cost
Electricity use is metered and electric price charged is dependent on several factors which must be considered. Demand charges may be imposed based on highest capacity required during the given billing period, typically a 15-minute interval during that billing cycle. The electricity price may also depend on Time-of-Use (TOU) energy to power the electric bus, including winter and summer rate schedules. Consult the utility company to fully understand the rate structures and strategies to manage both Demand and TOU electricity rates.
Charging infrastructure
There are two types of electric bus charging stations and equipment infrastructure – 1) Depot Plug-in Charging, and 2) On-Route Charging (either overhead or in-ground wireless). The type considered directly depends on range, passenger loads and energy costs. If carrying the highest number of passengers is the top priority and the route chosen is conducive for on an on-route charger, this strategy would allow the bus to operate around the clock and carry as little as 25 percent of the batteries of an extended range bus. If energy cost is the primary consideration, an extended range bus, potentially carrying fewer passengers and charged overnight with plug-in charging, may be the most economical alternative.
There are many options to configuring the electric bus specifications to the ideal charging strategy. The key to a successful electric bus deployment is to start the technical and infrastructure planning discussions early to identify the best solution before establishing the budget and project scope.
Funding electric buses and infrastructure
Once the best electric bus and charging strategy is identified, there are several paths available to assist transit agencies offset the incremental capital costs. Industry programs, such as the Federal Transit Administrations’ Low or No Emissions Program (Low-No Program), state rebate programs, and partnerships with utility and infrastructure partners can help offset the costs to deploy zero emission technology. Battery leasing, an option endorsed by the FTA, can offset initial costs with ongoing payments. Seek the assistance of non-profit clean transportation organizations such as CALSTART or the Center of Transportation and the Environment to identify funding strategies to acquire zero emission electric buses.
David Warren is the director of sustainable transportation for New Flyer and oversees activities related to the company’s commercial and technical support for low and zero emission bus programs. New Flyer is the only manufacturer in North America that offers three types of zero emission electric buses – battery electric, trolley electric, and fuel cell electric.