Most of the recent technological interest in alternative energy has been directed towards either hybrid systems or full electric vehicles. Not only are these the two main directions of development in the passenger vehicle market outside of conventionally powered cars, these technologies also represent the predominant developments in racing in terms of embracing environmentally friendly technologies. Whatever the arguments about the true environmental impact and economic viability of cars laden with lithium ion batteries, this is the way a large part of the automotive sector seems destined to go.
Usually in a hybrid car, the output of the engine is used to drive it, and this is augmented by energy supplied through an electric motor. More refined systems can bypass the engine at low car speed. This type of technology is called ‘parallel hybrid’. Diesel-electric locomotives are ’series hybrids’; the diesel engine is there simply as a means to power a generator, the energy from which is used for propulsion. Such series hybrids have a means of converting chemical energy in a fuel to electrical energy on board the vehicle. A number of car manufacturers are looking at series hybrids, and we are likely to see these on the roads in years to come.
Fuel cells follow this concept of onboard generation of electrical energy, but the process no longer involves an internal combustion engine. A fuel cell is similar in many ways to a battery: it has positive and negative electrodes, and an electrolyte, but it differs in not being able to store electrical energy like a battery can, relying instead on the flow of fuel into the fuel cell(s) to produce power. Fuel cell vehicles have proven themselves to be much more efficient than those with combustion engines. Fuel cells that use hydrogen as a fuel seem to be very popular among concept cars, and Mercedes, Toyota and Honda are notably pushing ahead with development and road trials.
The Le Mans race has recently granted one entry per year to a car, given the race number 56, which showcases radical new technologies. In 2012, the DeltaWing car had this entry, and in 2013 the GreenGT H2 will race as car 56. The GreenGT is a hydrogen fuel cell-powered car, and is featured in issue 65 of Race Engine Technology magazine. This car is eagerly awaited, as it is the first time that a fuel-cell powered car will compete in a top-level circuit race against well-developed conventional cars with internal combustion engines. There is potential to provide 400 kW (544 hp) to the rear wheels, using two motors. The car is at an early stage of development, and there is a lot of potential to save mass from the rather uncompetitive 1200-plus kg that it currently weighs.
That is not to say that fuel cells have not been used for competitive motorsport previously. At a lower level of cost, but involving strong engineering, Formula Student has had a hydrogen fuel cell-powered entry from Delft University, which competed at the Silverstone event this year. Formula Student engineers often go on to careers at the top levels of motorsport, and the Delft entry will be watched carefully in the future; it is unlikely to be the only fuel cell car.
Speed record competition embraces all kinds of motive power, and cars powered by fuel cells are no exception to this. The land speed record for a fuel cell-powered ’streamliner’ car stands at over 300 mph, held since 2009 by a team from Ohio State University.
There is some debate over the eco-friendly credentials of hydrogen-powered cars. While it is true that hydrogen can be formed by electrolysis of water, much industrial hydrogen is formed from a technique called methane-steam reforming, which liberates carbon dioxide. This process can only really be labelled as environmentally friendly if it is combined with CO2 capture.
Fig. 1 - The Buckeye Bullet is a hydrogen fuel cell-powered streamliner. It holds the fuel cell land speed record at over 300 mph
Written by Wayne Ward