4WD MODIFICATIONS - TECH TORQUE
As vehicle makers enter a new era of propulsion based on electric motors it’s timely to look at the fuel cell. This cold (or warm) combustion power source is already in service in several areas, including portable electricity generation and vehicle power.
The concept of a fuel cell was demonstrated in the early nineteenth century by a number of scientists, including Humphry Davy and Christian Friedrich Schönbein. William Grove, a chemist, physicist and lawyer, is generally credited with inventing the fuel cell in 1839.
The fuel-cell generator is an (expensive) alternative to a petrol or diesel portable generator, but recent developments in fuel cell technology are reducing pricing to the point where major vehicle makers, headed by Toyota, Hyundai and Honda, have released fuel-cell-powered production vehicles.
In early 2017 Honda and General Motors announced a plan to produce hydrogen fuel cell power systems in the United States from 2020. The companies said they will jointly invest $85 million to add a production line at a GM battery plant in Brownstown, Michigan and create 100 jobs.
The US military already uses fuel-cell electricity generators in large numbers and is evaluating a fuel cell ute: https://outbacktravelaustralia.com.au/announcements/fuel-cell-colorado-on-test
So, where does the fuel cell fit into the electric vehicle hierarchy?
The most common partially-electrically powered vehicles are hybrids that combine a battery pack, one or two electric motors and an internal-combustion engine.
Battery electric vehicles (BEVs) are predominantly battery powered, but some have a small auxiliary powerplant to charge the battery while the vehicle is moving, known as a ‘range extender’.
Fuel-cell electric vehicles (FCEVs) are driven by electric motors, with power from a battery bank that’s charged by an on-board fuel cell. The fuel for the cell is hydrogen that reacts with air.
Because of range issues, hybrid and fuel-cell power systems are the ones most likely to be fitted to 4WDs in the near and long-term future. Hybrids are short-term solutions, because they use fossil fuels, whereas the fuel-cell emits nothing but water vapour and nitrogen that enters the fuel cell with air.
There is no hot combustion in a fuel cell, so no nitrogen oxides are formed and because there is no carbon in the fuel there are no hydrocarbon, carbon monoxide or carbon dioxide emissions either.
Rather than relying on combustion to drive pistons that power an electric generator as in a hybrid car, a fuel-cell vehicle uses electro-chemistry to generate electricity. Compressed hydrogen gas is stored in a vehicle ‘tank’ and combined with oxygen from the air in the fuel cell.
It works like this:
In addition, a fuel-cell electric vehicle is more than three times as efficient as today’s average hydrocarbon-fuel-powered automobile and its range and fuelling time are comparable to those of conventional automobiles.
The FCEV electric drivetrain and battery pack is similar to that in a BEV and both use regenerative braking, a key energy-saving feature of electric vehicles.
Although the hydrogen fuel cell generates electric power, FCEVs need a battery pack to supply acceleration energy to the drive motors and to absorb electricity created by regenerative braking. In contrast to BEV batteries, however, FCEV batteries are only of modest size, like those in hybrid cars today.
Where FCEVs and BEVs differ is in the source of electricity, the time required to recharge or refuel, the driving range and the ability to scale up the size of the vehicle. All BEVs are small vehicles and a full-sized 4WD BEV is unlikely, unless there’s a breakthrough in battery size, weight and cost.
The electric driving range of mid-priced BEVs falls between 60 and 320 kilometres. Tesla is a (higher priced) exception, with claimed range up to 480 km. FCEVs and conventional vehicles typically travel 500-800km on a tank.
FCEVs are the base of Toyota’s plan to rid 90 percent of carbon dioxide emissions from its vehicles by 2050. The company has long contended it’s more likely to convince consumers to use petrol-electric hybrids and fuel-cell vehicles rather than battery-electric autos that have less range and take longer to recharge.
A BEV takes half an hour to more than four hours to charge when a high-voltage source is available and more than six hours using off-peak household power.
Toyota’s Mirai FCEV production vehicle looks like this under the skin: