I have been involved in several long debates within the alternative energy community about the advantages and disadvantages of both FCEV (fuel cell electric vehicle) ans BEV’s (battery electric vehicle)
I want to make a quick post with the important factors of both of these systems, and their applications in the real world.
In sence both of these power-trains are rather similar. The FCEV is essentially a BEV but instead of a large battery, it uses a much smaller high voltage traction battery (sometimes no battery) with the addition of a membrane fuel cell energy converter (Proton exchange membrane) on board that mixes 2 gases, usually hydrogen and oxygen (other gasses can be used, but these are by far the most common) and creates a reaction where bonds are broken and atoms are traded to form another substance, usually water is the by-product. During the reaction of breaking these covalent atomic bonds, energy is released. We can capture most of this energy using a fuel cell device, use it on demand, or store it in a battery until needed.
Now lets look at the in’s and outs of using hydrogen on board a vehicle as a FCEV.
–Acquiring Hydrogen– You may be thinking, where am I going to re-fuel my fuel cell car with hydrogen? And honestly its a very good question, there are only a handful of actual re-fueling stations available at this moment, mostly in California and you pay a premium (about $4.00 a gallon equivalent to gasoline)
–Fuel Reformer– But their is another option, using a fuel reformer. This will allow you to re-fuel your vehicle with gasoline, diesel, or natural gas (depending on its design) and then it will use a very complex system to convert it to hydrogen gas on-board your vehicle to feed the fuel-cell. The disadvantage is this reformer uses energy as well, bringing the total efficiency down even further then 80% and also forcing you to purchase gasoline (and isint the goal of alternative fuels to avoid using foreign fossil fuels?)
–Efficiency– Some of the best fuel cells that are commercially available are only 80% efficient. (only 80% of the hydrogen energy is actually captured) where BEV’s are usually upwards of 90% efficient with its on-board energy.
–Cost– one of the currently available FCEV’s the “Mercedes-Benz F-Cell” can be leased in only certain areas for $849/month! Full review here- http://www.roadandtrack.com/car-reviews/first-drives/2012-mercedes-benz-f-cell. Given that current BEV’s are fairly expensive, but the price has come down a lot over the past few years. Note the new lower price of the 2013 Nissan Leaf at $28,800!
–Rare metals– Most current designs of fuel cells require the use of very pure platinum in its construction. This is a very rare and expensive metal for something to be intended for wide spread adoption. Advancements in using less platinum, and shaping it differently has come a long way, but it’s still necessary. Lithium batteries require some special materials too, but luckily they are in abundant supply and getting more common due to their current demand.
Fuel cell enclosure and membrane
–Complication– The well-to-wheels operation of the FCEV goes something like this.
1. Electricity > Electrolysis process > Hydrogen gas storage > Transportation > Compression to vehicle tank > Fuel Cell membrane exchange > Electrical Inverter > Electric drive motor > Wheels
—or using a fuel reformer—
2. Oil drilling operation > Transportation > Refinery > Transportation > Fuel reformer (gasoline to hydrogen conversion) > Fuel Cell membrane exchange > Electrical Inverter > Electric motor > Wheels
compared to a BEV’s well-to-wheels goes like this.
1. Electricity > High voltage storage battery > Inverter > Drive motor > Wheels
It takes energy to perform every step listed above (>), reducing the overall efficiency. if you notice also in the FCEV number one, the cycle begins as electrical energy and ends as electrical energy. The hydrogen is just a “carrier” of energy in this method making MANY inefficiencies during the process, where as a BEV uses direct electricity during the entire process, eliminating many inefficiencies.
–Time of re-fueling– This is the only area where the FCEV shines, it can be re-fueled rather quickly in minutes. Where as the fastest BEV charger can return 150 miles in 30 minutes (Tesla supercharging station) still fast, but not as fast as the FCEV.
Understand that I am not intentionally trying to dismay the use of fuel cell vehicles, I think anything that is more efficient then our current ICE engines is great. And any invention that can operate on a non fossil fuel is great! Although the FCEV has some serious infrastructure and efficiency issues currently it doesn’t mean that in the future these can be advanced and improved. These inefficiencies of FCEV’s compared to battery electric vehicles can sometimes be overlooked for the quick re-fuel time in cases like the trucking, and construction industry where downtime in unacceptable, and fossil fuel usage is currently way too high.
prototype FCEV semi-truck