A version of this article was originally published in Railway Age.
The rail industry is struggling to determine what the locomotive of the future will look like. Railroads have committed to carbon emission reductions, but there still is much uncertainty about the feasibility of various energy solutions.
One problem may be that the industry is too focused on mutually exclusive options. Biofuels or electric? Hydrogen internal combustion engine or hydrogen fuel cell? While all of these choices are under review, there is one technology that could be beneficial across the board in increasing the energy efficiency of both current and future locomotives: battery-electric.
Although unlikely to be a solution on its own for road locomotives (but being deployed already in yard/local service), the potential benefits of battery-electric technology at every step in the green energy transition make it worth greater rail industry focus and investment — regardless of the ultimate direction the industry chooses for lowering emissions.
How battery-electric technology can reinvigorate the locomotive market
Is the search for the perfect locomotive solution getting in the way of continuous improvement in fuel efficiency/emissions reduction for the rail industry? The breaking of the “virtuous cycle” of locomotive purchases would suggest the answer is yes. There have been few new locomotives bought in the past decade, since Tier 4 broke the cycle of efficiency gains from each new generation of power (Exhibit 1).
Most, if not all, future locomotive concepts could leverage battery-electric technology to further improve their efficiency — and in the process reignite the virtuous cycle, so that railroads would once more have a reason to upgrade locomotives regularly — with ensuring cost, fuel, and emissions benefits.
The primary benefit of battery-electric technology is that it can recapture and store braking energy, which is currently burned off as heat in today’s locomotives. Incorporating battery-electric into new locomotive designs (or multiple-locomotive consists) could reduce overall energy consumption. Wabtec for example has seen 11% fuel savings by including its FLXdrive battery-electric locomotive (BEL) in a diesel consist (capturing only the braking energy of the BEL itself). Other studies suggest that 15% could be achievable, based on the cost and space required for current batteries. Of course, future battery technology might push this number much higher.
Another consideration is that alternative fuels (such as biofuels and hydrogen) are more costly to make than diesel fuel, at least for the foreseeable future. Including battery-electric in new locomotives would not only further reduce emissions but would mean buying less fuel — thereby reducing operating costs and putting less strain on future fuel supply chains.
Adding battery-electric technology to improve future locomotive options
At present, railroads are heavily focused on “drop in” biofuels as a potential solution. Capturing braking energy using battery-electric technology at the same time would double emissions reductions, compared to 20% biofuel usage alone. Given limitations on biofuel feedstocks and competition from other industries (particularly aviation), however, it is unlikely that rail will be able to expand biofuels usage to 100%.
Hydrogen fuel cells (HFC) also are being considered as a power source, but these don’t scale output up and down as easily as a diesel engine. Thus, hybrid battery technology is being incorporated into HFC locomotive design to provide a buffer for power adjustment – as well as to recapture braking energy. Another type of hydrogen-fueled locomotive — the hydrogen internal combustion engine, which would be more like a diesel engine — also would see a drop in fuel requirements by incorporating battery-electric.
Then there is the potential for electric trains. What if catenary systems end up being the best choice for future power? We know from the experience of increasing clearances for doublestack intermodal that modifying problem areas where clearances are tight, such as tunnels and overpasses, can be expensive, disruptive, and time-consuming. A more viable solution might be discontinuous catenary, in which battery-electric is used to push trains through gaps.
Regenerative braking energy also has been captured and fed into overhead catenary systems for instant use by other trains for decades; the next step will be figuring out how to store this “free energy” for non-catenary applications.
Extending the value of diesel engines with battery-electric technology
Battery-electric also could extend the value of today’s diesel engine technology while new fuel solutions are in development (Exhibit 2). It looks increasingly like diesel will be in use for at least another locomotive generation. Hybrid diesel-battery technology could potentially scale down the horsepower requirements for diesel engines from 4,400 hp to perhaps 3,000-3,200 hp, making space for batteries that surge power as well as recapturing braking energy.
Sophisticated modern control systems could then be used to optimize the engine efficiency of such hybrids. And with hybrid locomotives, it would be possible to recapture the braking energy from all locomotives in a consist. Canadian National is acquiring an SD70H hybrid locomotive from Progress Rail to test in British Columbia, while NS and Alstom are converting two GP 380/40’s to this hybrid design.
Hybrid consists are another way that battery-electric could be leveraged to improve emissions reduction and fuel efficiency for diesels. Today’s multiple-locomotive consists rarely need all the power available to them, except when running uphill or starting from a cold stop. BELs could be an ideal booster unit instead, eliminating the need for at least one diesel locomotive and providing a fuel efficiency benefit.
Most critically, using BELs in consists now would allow more time for the industry to develop a diesel engine replacement without creating a stranded investment — since a BEL could provide benefits to any future locomotive consist. The BEL might not even need a cab, if always used in the middle of a consist, providing more space for batteries and eliminating the cost of cab components.
These units also can be partially built from recycled assets: In Australia, Aurizon is working with Progress Rail to retrofit a BEL from one of its own 4000-class diesels. And BELs are expected to have lower maintenance requirements than diesels, just like electric vehicles have lower maintenance needs than conventional vehicles.
Achieving next-generation efficiency in rail through hybrid innovation
Battery technology is improving rapidly, both in capacity and cost. It is important for the rail industry to invest in this technology now and continue to leverage it as the technology improves. Regardless of what the rail industry ultimately chooses for a solution — even if that is sticking with diesel for another 20-plus years, battery-electric technology can play an important role.
The rail industry could reap cost and efficiency improvements and lower both fuel consumption and emissions quite quickly by including battery-electric in hybrid locomotives and consists.
A final consideration: Trucks have improved their fuel efficiency by nearly 15% since 2015, while railroads have barely moved the needle. Battery-electric could be a crucial stepping stone to the breakthroughs in locomotive design the industry needs, not only to trigger new locomotive buying, but to maintain and improve the competitive economics of railroading.
Read the original piece here.