Hydrogen for fuel cell electric vehicles
By Nick Ni – Verde LLC, Massachusetts, USA
The concept of fuel cell electric vehicles (FCEVs) has been promoted for several years. Compared to conventional vehicles, fuel cell powered vehicles generate zero greenhouse gas emissions and air pollutants at point-of-use. In addition, they can greatly reduce global dependence on gasoline, which may be exhausted in the near future.
With the development of fuel cell technology, fuel cell electric vehicles are more than twice as efficient as internal combustion engines, promise equivalent durability with a refueling range of 300 miles (480 km), and have 60% fewer parts and 90% fewer moving parts.
These great features leave us a lot of imagination for FCEVs. But wait – there are still several obstacles to overcome on the path towards a bright future for fuel cells.
The first problem is onboard hydrogen storage. Unlike gasoline, hydrogen is normally in gaseous form, and not suitable for storing large amounts under normal pressure and temperature. Therefore, one solution is applying high pressure (5000–10 000 psi, 350–700 bar) to compress the hydrogen gas into a sealed tank. Such a compression system is unavoidably heavy and large, but this is the most cost-effective solution in the near term.
Another solution is reducing the temperature to –423°F (–253°C) to liquefy the hydrogen. Since hydrogen is densest as a liquid, this solution allows more hydrogen storage than gaseous storage under high pressure. However, several issues remain in using this method, such as hydrogen boil-off, high energy requirements for hydrogen liquefaction, and the cost of cryogenic tanks.
Recently, hydrogen adsorption in solid materials has become a very promising solution towards effective hydrogen storage. Systems based on this technology have the potential to be small and lightweight, and may prove to be the best solution in the long term.
Daimler has presented a research fuel cell electric vehicle, the Mercedes-Benz F125!, utilising metal-organic framework (MOF) technology to store hydrogen. This technology builds up metal-based porous structures, and can efficiently adsorb/release hydrogen as needed. Further research in this area is ongoing, and hopefully it will replace high-pressure hydrogen storage in the next 10 years.
Then what’s the next problem? Aha – where can I refuel my fuel cell car if I have one? The extensive system used to deliver gasoline from refineries to local filling stations cannot be used for hydrogen. New facilities and systems must be constructed for producing, transporting, and dispensing hydrogen to consumers.
Currently, there are only 10 hydrogen stations in the US (excluding private stations), and nine of them are located in California. Nobody will buy a fuel cell electric vehicle if there is no hydrogen station nearby. Therefore, how to conveniently deliver hydrogen to consumers is a big challenge for FCEV commercialisation.
The idea of home hydrogen stations is then prompted as an alternative solution. The home hydrogen station generates hydrogen from natural gas or water electrolysis using solar or wind power. It is designed to provide heat and electricity for the home, and to supply hydrogen fuel for a hydrogen powered vehicle.
This approach can not only support the hydrogen supply for the vehicle, but also reduce CO2 emissions from a household. Even using natural gas, CO2 emissions can be reduced by 30% compared to an average household using a gasoline-engine car and with commercial electricity and heat.
Now, more and more companies such as Honda, Ballard Power Systems, Verde LLC etc. are focusing on designing and constructing home-sized hydrogen generation stations with simplicity of use. With the increasing popularity of public and private hydrogen stations, fuel cell electric vehicles will be widely used around the world.
As well as these two main issues related to FCEVs, there are other limitations, such as vehicle cost, fuel cell durability and reliability, public acceptance etc. However, with the development of the technology, these problems can soon be solved. For example, the cost of fuel cell systems for vehicles was reduced from $248/kW in 2002 to $47/kW in 2012, almost reaching the US Department of Energy’s cost goal of $30/kW.
Fuel cells can become more durable and reliable by utilising modified catalysts, such as those reported by Radoslav Adzic et al. at Brookhaven National Laboratory. And while the public has shown initial concerns with the safety of fuel cell electric vehicles, in fact they are as safe as gasoline-powered cars. It just takes time for the public to accept a new technology.
Based on the above discussion, it is very reasonable to predict that within 20–30 years, fuel cell electric vehicles will finally replace conventional vehicles as the main ground transportation technology. It’s not outlandish to dream that airplanes or ships might soon be powered by fuel cells either… The third industrial revolution is really happening right now!
Based in Braintree, Massachusetts, Verde LLC designs and deploys residential, commercial, and industrial-scale electrolysers for renewable energy storage, industrial processing, transportation fuel, natural gas plant peaking and cooling, fertiliser manufacture, and distributed generation. The company – a subsidiary of Angstrom Advanced Inc – has products in operation around the world, and an extensive network with national laboratories, commercial/industrial partners, and universities.
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