Beyond the tailpipe: Factors in the green equation

Cummins has always believed in the power of choice. Whether it’s providing our customers with cleaner, greener diesel technology or leading the charge in alternative power, we’re passionate about providing customers — and the world — with the best power solutions. 

There’s no one single “fits-all” solution when it comes to transportation technology. That’s why we’ve invested in a wide range of emerging and established technologies. Just like in many other industries, different challenges in transportation require different solutions. As we continue to develop battery electric technology and hydrogen fuel cells, we’re committed to educating the public on the differences and opportunities that come with these forms of alternative power. 

Battery electric vehicles (BEVs) and fuel cell technologies, both in the form of fuel cell electric vehicles (FCEVs) and electrolyzers, create zero emissions as they’re being used. Electricity produces no emissions, and fuel cells release only clean water and water vapour, which do no harm to the environment. This is a major advantage that both electric and fuel cell technologies share: they’re completely green at the tailpipe. But to understand the true carbon footprint of any technology, it’s important to look at the entire process of powering a green vehicle. Where your energy comes from, how it’s stored and how it’s transported are often-overlooked factors that affect the sustainability and environmental impact of any given form of transportation or power. Let’s take a look at some of the factors that go into the “green equation” of battery electric and fuel cell power. 

Sourcing Power 

What differentiates battery electric technology and fuel cells’ overall emissions is the generation source of the power stored in the battery or within hydrogen. The process by which the energy is generated ultimately determines the overall carbon footprint of the application. 

Most BEVs use power from the public electricity grid to recharge. A public grid can also be used to power an electrolyzer to produce hydrogen. Because grid electricity often comes from coal or other methods that do produce emissions, the energy stored in either a battery or hydrogen is only as clean as the power grid it’s running on. If the power grid is supplied from coal, natural gas or other carbon-emitting generation sources, the energy that the application uses has its associated emissions. 

In the U.S., about 30% of grid power comes from coal, 30% from natural gas and 40% from clean sources including nuclear, hydropower, wind, solar and geothermal. But not all states and counties have the same mix — some are dramatically greener than others. For example, New York uses a lot of hydropower, whereas Colorado uses a lot of coal. That’s why it’s important to look at the power that’s available in your own area as opposed to national averages. The good news is that things are changing fast. Overall, the U.S. power grid has continued to get greener over time. Even coal is being made cleaner with a lower carbon footprint, but the availability of clean coal still varies from technology to technology. 

What we’ve found in pioneering some of these technologies is that application makes a difference in overall emissions. It’s difficult to make overarching claims about one power source being cleaner or greener than the other — it depends on factors within each application and its supply. It’s important to think about where the electricity or the hydrogen comes from as the overall carbon footprint. Hydrogen can be generated from a wide variety of sources like natural gas, oil, coal, electrolysis, radiolysis and thermolysis, which all have different environmental impacts. The same goes for BEVs. Even within the Class 8 short-haul heavy duty class, carbon impact depends on the application and the powertrain itself.  

The source of electricity and hydrogen matters. If electricity is used to generate hydrogen, the carbon footprint of the electricity source is greater than if it was used directly in the vehicle (i.e. BEV) because of the various efficiencies and added steps in the conversion of energy to vehicle propulsion. As you can see, the “green equation” often becomes quite complicated — but we’re committed to exploring ways to make battery electric and fuel cell power as clean as possible. 

Going Renewable 

There are many ways to produce cleaner power for both technologies. Batteries can recharge directly from clean renewable energy sources outside of the public electricity grid — including private sources like wind and solar. Clean energy combined with clean technology is an ideal state for the applications that can run on technology like batteries or fuel cells. But the economics, stability and availability of suitable renewable sources are often very limiting. 

In many cases, renewable energy sources outside of the public grid are not stable enough to provide the consistency required to recharge fleets of BEVs on a large scale. Sources such as wind and solar only produce power when the wind is blowing or the sun is shining. That’s why stationary power storage can be equally as important as the renewable energy sources themselves. 

Beyond their transportation applications, both batteries and fuel cells, in the form of electrolyzers, are also used for reliable stationary power storage. As background, electrolyzers manufacture commercial hydrogen using electrolysis to harvest hydrogen from water through a chemical reaction that splits water into hydrogen and oxygen. The hydrogen acts as an energy carrier and the oxygen is released into the air. The hydrogen can then be stored in a gas or liquid state to be used in a multitude of applications, including fuel cell electric mobility. By using hydroelectricity, renewable hydrogen is produced with no carbon associated with the production or consumption of the fuel.  

This allows for the storage of power that may otherwise be wasted and creates a more reliable power supply out of typically inconsistent power sources like wind and solar. A recent example of this is Cummins developing the largest electrolyzer in the United States. If renewable energy sources were used to directly charge BEVs, the ability to use the vehicle would be dependent on the weather — and this is not a condition many transportation operators can accommodate. 

When electricity is available and not being used, it’s wasted, and storing electricity in stationary batteries is expensive and inefficient. That’s why we may be better served by converting unused electricity into hydrogen in order to preserve it. However, this does mean that the hydrogen may need to be compressed or liquified, and possibly transported to a dispensing site if it’s for transport use, which comes with its own complexities. 

We can, however, use existing infrastructure in other ways. Hydrogen can be mixed into pre-existing natural gas pipelines (in volumes below four percent) to be consumed by systems already consuming natural gas. This is a promising solution that makes use of existing pipelines and natural gas-powered applications without the need for major investment in new transportation methods or technology. 

Regardless of the compression, liquefaction and transportation challenges, electrolyzers that generate hydrogen are also a promising choice for energy storage. They’re designed to accommodate the intermittent nature of renewable energy sources, so you can have power to rely on rain or shine, wind or calm, without restriction. This ability to store mass amounts of renewable power is one of key differentiators between BEV and fuel cells in the form of electrolyzer technologies as we know them today. 

Investing in Infrastructure 

There are also infrastructure and supply considerations for FCEVs. To support a large fleet of FCEVs, a sufficient hydrogen fuel supply is vital. As our industry stands now, that can be costly to come by. Hydrogen fuel can be delivered from a remote hydrogen production plant or produced 24/7 onsite at a refueling station using an electrolyzer — but this requires a significant upfront investment in purchasing the infrastructure needed for hydrogen generation. It’s the flexibility of this electrolyzer to work inside and outside of the energy grid that has massive implications on decarbonization. 

While hydrogen infrastructure may not be as widespread as the electric grid, it gets more complicated when dealing with dispensing. When electricity is made, it can be readily moved around the country or the world through the existing power grid. It can also be “dispensed” by a charger without the need for any storage, assuming the grid is sufficiently resilient. 

On the other hand, hydrogen will require trucks or pipelines to transport it. We must also consider compression and storage, which are necessary at the dispensing station. While all this makes it seem like hydrogen’s lack of infrastructure would make it a non-starter, the trade-off comes when you explore the time it takes to fill a tank. Electric vehicles need long charge times. Even passenger electric cars can only go a few hundred miles before needing to charge for an hour or more. But hydrogen is much, much faster, so there’s less fueling downtime for a fuel cell vehicle than its all-electric counterpart. The chart below shows that while diesel is much more efficient in terms of fueling time to driving time, hydrogen’s low-end capability is very similar to EV’s high-end capability. 

Long story short, judging a power source’s “greenness” is complicated. Myriad factors go into the green equation, with myriad additional compounding factors. No one has all the answers yet, but at Cummins, we’re still innovating day in and day out to create reliable, sustainable power options for our customers and our planet.  

Cummins uses electrified power technologies to power school buses and commercial buses and uses fuel cell and hydrogen technologies to power a variety of applications, including transit buses, semi-trucks, delivery trucks, refuse trucks and passenger trains, and has made several announcements in the past year related to hydrogen and fuel cell technologies. You can see more examples of how Cummins has supported new firsts in the fuel cell and hydrogen industry.   

Customers have never had more power options to choose from to accomplish their goals. That’s how Cummins is powering a world that’s always on. 

Read even more about batteries and fuel cell similarities and differences.