By Noel T. Braymer
Recently there was excitement among techno-geeks about a patent application by the Tesla electric car company for a hybrid metal-air/lithium ion battery car. The speculation was this could be Tesla’s 400 mile range electric car it has been working on. So what is a hybrid metal-air/lithium ion car? The idea is to use both batteries in an electric car. The metal-air battery would be used to keep the lithium-ion battery charged to extend the car’s range like a gasoline motor does on a plug-in gas-electric hybrid car. The lithium ion batteries would still be regularly charged for day to day driving of under 50 miles per day. But with both batteries such a car could have a non-stop range of 400 miles or more.
Tesla is not alone thinking along these lines. An Israeli company called Phinergy recently demonstrated a converted Citroen car that ran on battery power for 1,000 miles. Phinergy has developed an aluminum-air battery which they claim will be on the market by 2017. The advantage of metal-air batteries is they can produce much more electricity per pound than other batteries. The problem with them is they have been impossible to recharge or reuse. The Phinergy battery is good for about 1000 miles and then will need to be exchanged with a rebuilt battery. Phinergy plans to use their aluminum-air batteries to keep the lithium-ion batteries in an electric car charged to extend their range. A rechargeable metal-air battery is the “holy grail” of inventors to create electric vehicles fully competitive with fossil fueled powered vehicles. A rechargeable metal-air battery is likely to be produced in the near future. It might take the form of a molten liquid metal-air battery which is recharged by replacing the molten liquid metal.
Greatly improved lithium batteries will be available in the near future. Using quick charging batteries means fewer batteries are needed to for a full day of service. This is being tested now by running electric transit buses which are charged at layover stops between runs. In South Korea there are experiments to recharge electric buses on the run with electromagnetic induction. This is done with power transmitted from cables buried in the road to the bus overhead. The cables produce magnetic waves which the bus is equipped to convert into electricity. Power on the run could also be done with overhead wires for trolley buses or electric trains to recharge batteries.
What would be the advantages of adding batteries to electric trains? One big advantage would be that service wouldn’t shut down if there is a power outage or damage to a short section of overhead catenary wires which happens more often than is desired. We have just seen this on Metro-North in New York which has impacted the entire North East Corridor for over a week. Another issue is construction of an overhead catenary electrical system is very expensive. Often there are branch lines which it is not economical to extend catenary on an electric railroad. While it is possible to add pantographs to diesel-electric locomotives it is expensive to do.
With battery equipped electrical trains it will be possible to extend electric rail service to more places economically. There are many places where construction of cantenary is not welcomed. For many places using battery equipped trains means that an entire line wouldn’t have to be fully electrified which would save money. This would also allow rail service from future busy electrified rail lines to continue on to non-electrified areas. An example of this would be future electrified Caltrain service not needing diesel locomotives to continue serving Gilroy.
Having battery equipped electric trains for California High Speed Rail can mean trains could continue in 2025 past Burbank at the planned end of catenary to Los Angeles Union Station, Anaheim or even San Diego. With recharging capability trains could be extended past Merced to Sacramento and even Oakland using the existing tracks. This wouldn’t eliminate the need for all transfer trains, but would attract more riders from day one with more direct service.
Another advantage of extending electrical rail passenger service is this might earn credits on the California Cap and Trade Exchange to reduce carbon emissions. These credits could be sold for cash to companies exceeding their allowed carbon emissions. Allowing more train service to use electricity which local agencies could produce with solar arrays on their property would also save money and insulate rail service from future uncertainties about the cost of fuel.