Companies like Toyota, Nikola and H2X are doubling down on hydrogen fuel cell vehicles and positioning them as alternatives to their more popular zero-emission counterparts, battery-electric vehicles. These companies and some advocates believe fuel cell vehicles could be key to decarbonising the transport sector without sacrificing range or payload, thanks to fuel cell vehicles’ smaller batteries and lower weight.
Like battery-electric vehicles, fuel cell electric vehicles promise zero tailpipe emissions. They generate electricity by pumping hydrogen from a fuel tank into one side of the fuel cell stack as oxygen from the air enters the other side. Inside the fuel cell stack, the hydrogen breaks into protons and electrons that generate electricity then re-bond to expel water vapour through the tailpipe. The electricity from the fuel cell stack feeds into a battery that operates an electric motor. According to the Hydrogen Analysis Resource Center, there are more than 20,000 active fuel cell vehicles worldwide; about 14 percent of those are buses, six percent are trucks and the remainder are light-duty passenger vehicles. In 2016, fuel cell vehicles comprised only 0.5 percent of total zero-emission vehicle sales, and most of these vehicles were operating in just a few countries (parts of Europe, the United States, China and Japan).
Fuel cell vehicles still have batteries, but they are much smaller and lighter than those in battery-electric vehicles. In general, batteries are heavier than internal combustion engines and for some classes of vehicles, the extra weight can be a problem. For example, the additional weight of 600-kWh battery in a battery-electric truck could reduce cargo capacity by three percent compared to the same truck powered by a diesel engine. Because fuel cell vehicles store energy in the form of hydrogen, their batteries can be anywhere from six to 50 times smaller than a battery-electric vehicle. The reduced battery weight can be particularly advantageous for vehicles that need a lot of power but also need to maximise their payloads, like freight and aviation.
Fuel cell vehicles also have a fuel tank. Combined with the lighter battery, this energy system allows them to operate at longer ranges than battery-electric vehicles because they store more energy at a lower density. Studies that focus on efficiency and well-to-wheel analyses find that fuel cell vehicles could be competitive at ranges over 400 kilometres.
Infrastructure is the costliest difference between fuel cell and battery-electric vehicles because of the sheer number of stakeholders involved in the hydrogen fuel supply chain. There are efforts to grow the fuel cell vehicle market in several countries, but they depend on large government investments. Fueling infrastructure and hydrogen production costs comprise between 30-60 percent of total fuel cell vehicle deployment costs today. Stations generally cost between $1-2 million, depending on geography. Station capacity generally ranges from 200 to 600 kg/day, enough to fill between 6 and 20 buses. In comparison, electric charging stations in Philadelphia cost roughly $1 million all-in for a fleet of 25 battery-electric buses.
A closer look at sustainability
Depending on the emissions from charging and from hydrogen production, both fuel cell and battery-electric vehicles emit fewer pollutants than their internal combustion engine alternatives and are the only technologies with the possibility of emitting no carbon dioxide. In the United States, the average battery-electric vehicle emits 176 grams of CO2 per mile when charging from an average electricity grid. Fuel cell electric vehicles fueled by hydrogen from steam-methane reforming emit about 241 grammes of CO2 per mile. Both technologies not only emit significantly less carbon than gasoline powered internal combustion engine vehicles, whose emissions hit 414 grams CO2 per mile, but they also emit fewer air pollutants like nitrogen oxides and particulate matter, which contribute to millions of premature deaths each year.
What makes things tricky is that while life cycle emissions and total cost of ownership are key comparisons for understanding the long-term benefits of these technologies, life cycle emissions are hard to quantify and difficult to compare across geographies. For example, emissions from electricity production and emissions from hydrogen production vary significantly depending on the prevailing infrastructure. In most places, the grid is clean enough that battery-electric vehicles can generate greater emissions reductions compared to business-as-usual scenarios and in some places, like South America where hydropower is more prominent, these reductions are even more impactful.
(Eleanor Jackson is a Research and Communications Assistant for the Global Electric Mobility team at WRI Ross Center for Sustainable Cities. This article originally appeared on City Fix.) (TheCityFix)
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