Since last spring, a new locomotive has been shuttling cargo around the ports of Long Beach and Los Angeles – and it would probably be turning heads, except that it’s so quiet no one can hear it coming.

Similar to cars and trucks that run on rechargeable batteries, the zero-emissions electric locomotive known as the Joule operates almost noiselessly (although it’s got a necessarily loud horn).

“When it is running, unless the air compressor motor is turning, it’s dead silent,” said F&M Rail Service President Kevin Masters; F&M handles maintenance of trains for Pacific Harbor Line, which is currently testing and troubleshooting the Joule in the San Pedro ports.

If the battery electric model proves satisfactory, Pacific Harbor Line could add more of them to its fleet of about 25 locomotives, which would move the Port of Long Beach another step toward its goal of zero-emissions goods movement by 2035.

The effort that led to the Joule’s creation started about five years ago, when employees at Alabama-based Progress Rail “saw the rapid advancement of battery technology and started to consider, how can this technology be used in the rail space,” said Michael Cleveland, Progress Rail’s director of advanced energy. (The company is a division of engine, turbine and construction equipment maker Caterpillar Inc.)

Built in Brazil, the Joule (with an appropriately green and white paint job) looks like any modern locomotive – but instead of a 4,000-gallon fuel tank that would occupy the entire underside of the vehicle frame, it’s packed with 244 battery modules that give it 2.4MWh of battery storage.

A new charging station in PHL’s yard has cut the time to power up the locomotive from 20 hours to just five hours. As to performance, Masters said, “It pulls basically like a regular diesel locomotive,” although the battery electric model doesn’t have the same range between fueling/charging as a traditional engine.

Maintaining the Joule is not as much work as a diesel engine, Masters said – it’s mostly about keeping the electronics working and fine-tuning the software. Because the ports are in constant operation, F&M mechanics have had to learn on the fly how to fix the Joule, a job initially complicated by the fact that its operating manual was in Portuguese.

The addition of an all-electric locomotive is part of a progression for PHL, which has been regularly upgrading its fleet to reduce health-harming diesel emissions since about 2007.

Last January, the company switched from low sulfur fuel to renewable diesel, and “now we’re progressing to no diesel at all,” PHL President Otis Cliatt II said.

And with the Joule, he joked, “It’s so clean that if there were any more (pollution) reductions, it would actually be putting oxygen back into the atmosphere.”

There are still some kinks to be worked out, such as how many charging stations would be needed for a battery electric fleet, where they should be positioned around the ports – and how to power those charging stations in an eco-friendly way.

And cost may be a challenge as well. Cleveland and Cliatt declined to discuss the Joule’s price tag, but some news reports put electric locomotives in the low-seven-figure range. Cliatt said one issue PHL officials didn’t anticipate was that because they’ve been early adopters of cleaner technology, it’s gotten harder to find grants since much of the money is aimed at upgrading the oldest and dirtiest rail equipment.

Experts said the capabilities and shortcomings of battery electric locomotives can depend on what they’re being asked to do.

Ida Posner, vice president of strategic planning at Railroad Development Corporation, said a battery-powered locomotive makes sense at the San Pedro ports, where reducing harmful emissions is a major concern and the limited range is less of a problem.

“It might not make sense to put a battery locomotive out in the middle of a rural area because you’re not as concerned with that point source pollution,” but some other option – such as a hydrogen-fueled model – might be more suitable, she said.

“What the future of propulsion looks like depends on where you are, what you’re moving and what resources you have around you,” she said.

Cliatt and Cleveland agreed that while battery electric locomotives appear promising, they’re unlikely to be the end of the line. Posner predicts “a bunch of different solutions in different areas,” based on the cost of the technologies and how they will be used.

The revolution that shifted railways from steam-powered locomotives to much more efficient diesel ones started nearly a century ago, Cleveland noted. And as industries that depend on transportation consider which technologies to pursue, he said, today we’re at a similar inflection point but “it’s a much more complicated moment than that transition.”

For now, what matters to South Bay residents who want cleaner air is whether PHL’s new locomotive reduces diesel particulates and other harmful emissions. Based on the testing to date, so far, so good.

And what’s most important to Cliatt and PHL is whether it works: how well can it handle tight curves and hills, and does it have any limitations or drawbacks?

“That’s absolutely what we’re here to find out,” Cliatt said.

The Joule’s testing period in the ports of Los Angeles and Long Beach will wrap up in the next few months, but Cliatt said it could be extended up to 12 more months.