- CARB Evaluates Battery Electric and Hydrogen Fuel Cell Locomotives
CARB staff analyzed available zero emission locomotive technologies and determined the minimum number of locomotives required to pull 130 double stacked rail cars from the Port of Los Angeles to Barstow.
Key Takeaway
The CPKC hydrogen fuel cell locomotive has similar traction power to Wabtec’s FLXdrive, however, the total range that the CPKC locomotive can travel is considerably more. Hydrogen carries more energy than current batteries and a fuel cell locomotive utilizing a tender car can carry even more hydrogen along its route to extend the locomotive range. CPKC’s fuel cell locomotive utilizing a tender car can carry more than four times the amount of energy of Progress Rail’s SD70J-BB battery electric locomotive. Utilizing a hydrogen fuel cell locomotive with a tender car may be beneficial to some operators if they intend on traveling distances further than Barstow and do not want to stop to refuel, or recharge, in the case of battery electric locomotives.
Staff analyzed the feasibility of using current battery electric and hydrogen fuel cell zero emission (ZE) locomotive technologies from the Port of Los Angeles (POLA) to Barstow, a high-traffic freight route in California. For a train to complete a trip from POLA to Barstow, there must be sufficient power and energy supplied from the locomotives throughout the trip. To determine the number of current ZE locomotives required to pull 130 double stacked railcars from POLA to Barstow, power and energy required to complete the trip needed to be calculated while taking into account length of trip, track grade, rolling resistance, and drag. Once the power and energy required to complete the trip were calculated, staff were able to determine the minimum number of ZE locomotives required to supply the power and energy needed. The ZE locomotive models being evaluated in this analysis are Wabtec’s FLXdrive Heavy-Haul battery electric locomotive, Progress Rail’s SD70J-BB battery electric locomotive, and CPKC’s hydrogen fuel cell locomotive with a tender car to carry hydrogen fuel. These models were chosen as they are rated for line haul operation and could be used by Class I railroads.
Analysis Assumptions
Route from Port of LA to Barstow
The route from POLA to Barstow is approximately 174 miles with elevation as low as 17 feet and as high as 3,800 feet above sea level. The analysis splits the route into five segments as shown in Figure 1. The five segments were defined based on significant differences in elevation change. For example, Segment 1 has no elevation change, while Segments 2 and 3 have elevation changes with hill grades of 0.6% and 2.2%, respectively. Segments 4 and 5 are downhill portions of the route.
Power and Energy Requirements
The power and energy required to travel along each segment of the route from POLA to Barstow were calculated. Power  was calculated by finding the net force required for the locomotives to pull the train multiplied by the train’s velocity. The net forces calculated along each segment considers the force to overcome a hill against gravity, drag force, and rolling resistance (frictional forces).  Energy requirement was calculated by multiplying power by the time it takes to travel along that segment based on the train’s velocity.
The mass of the 130 double stacked railcars, with each container weighing 19 tons, used in the analysis was calculated using the methodology found in CARB’s Truck vs. Train Emissions Analysis. The total mass of the train is equal to the sum of the railcar mass with cargo and locomotive mass. To determine the number of ZE locomotives required to complete a trip from POLA to Barstow, a minimum energy and power requirement was determined. Staff found that Segments 1-3 require the use of energy from the locomotive, while Segments 4-5 do not. Therefore, the minimum energy required to complete the trip is the sum of the energy needed in Segments 1‑3. A minimum power requirement was determined by determining the most power required by a segment. Segment 3 has the largest power requirement due to its steep grade, so the Segment 3 power requirement was set as the minimum power requirement for the train to complete the trip from POLA to Barstow.
Analysis Results
The table below shows the minimum number of ZE locomotives required to complete the trip from POLA to Barstow for different locomotive types and models. The analysis also compares the number of locomotives required for different factor of safety (FOS) values to account for errors (up to 20%) in power and energy calculations.
| Locomotive Model | Type | Weight per locomotive (MT) | Traction Power per locomotive (MW) | Usable Energy Capacity per locomotive (MWh) | Minimum Number of Locomotives Required | |
| FOS: 1 | FOS: 1.2 | |||||
| Typical Diesel Locomotive | Diesel | 218 | 3.2 | 65.2 | 7 | 8 |
| SD70J-BB | Battery Electric | 245 | 5.7 | 13.05 | 4 | 5 |
| FLXdrive Heavy-Haul | Battery Electric | 189 | 3.2 | 7.65 | 6 | 8 |
| CPKC Line-Haul (with tender car) | Hydrogen Fuel Cell | 167 | 3.3 | 55.8 (per hydrogen tender car) | 6 | 8 |
The major limiting factor that impacts the number of locomotives required to travel from POLA to Barstow is traction power. Due to the steep inclines along the Cajon Pass, a locomotive with higher traction power is favorable. The analysis concludes that for a train consisting of 130 double stacked railcars, an equal amount or fewer ZE locomotives are required complete the trip compared to diesel locomotives, which further demonstrates the capability of ZE locomotives along routes like POLA to Barstow.
Progress Rail’s SD70J-BB battery electric locomotive will require the least number of locomotives (4 locomotives with factor of safety of 1) to travel from POLA to Barstow as it offers the highest traction power compared to the other locomotive models. When using typical BNSF diesel locomotives, 7-8 locomotives are required to complete the trip. CPKC’s hydrogen fuel cell locomotive and Wabtec’s FLXdrive Heavy-Haul have a similar power output, and thus the number of locomotives required are similar between the two models.
Staff also estimate that the analysis result is scalable to heavier or lighter trains. That is, a 50% increase in the number of double stacked railcars will result in approximately 50% more locomotives required for all three zero-emission models (when factor of safety is 1 and not including combinations of different types of locomotives within a train). While the relationship between train mass and number of locomotives needed is not exactly linear, the trend generally holds. The weight of railcars and containers contribute most to the power required to complete the trip, thus affecting the number of locomotives needed.
Key Takeaway
The CPKC hydrogen fuel cell locomotive has similar traction power to Wabtec’s FLXdrive, however, the total range that the CPKC locomotive can travel is considerably more. Hydrogen carries more energy than current batteries and a fuel cell locomotive utilizing a tender car can carry even more hydrogen along its route to extend the locomotive range. CPKC’s fuel cell locomotive utilizing a tender car can carry more than four times the amount of energy of Progress Rail’s SD70J-BB battery electric locomotive. Utilizing a hydrogen fuel cell locomotive with a tender car may be beneficial to some operators if they intend on traveling distances further than Barstow and do not want to stop to refuel, or recharge, in the case of battery electric locomotives.
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