Lisbon water taxi makes use of Millennium Cell on-demand hydrogen system
You would think they have it easy. Gasoline sets a low standard indeed for futurists wanting to replace it with renewable fuel. It's flammable, toxic enough to kill grass on contact, and so explosive you might face less danger with dynamite in your fuel tank. If anyone had had environmental concerns when the automobile was invented, we would still be saddling Bessy for a ride to the mall.
The prime contender for the fuel of the future remains hydrogen, and engineers are still striving for a way to make it a convenient, safe and trouble-free as - yes - gasoline. But hydrogen remains an intractable, colorless, odorless, explosive and elusive lighter-than-air gas that not only wants to hiss away from any fuel tank but also escape away into outer space.
A new, quiet and environmentally conscious water taxi slipping through Cais do Sodre harbor in Portugal may hold the key to containing hydrogen. The 30-foot launch, one of the first fuel-cell-powered boats, runs on a hydrogen-rich liquid fuel made from a substance any mule-driver would love, borax.
The boat itself is unassuming, even old-fashioned. Except for its power source, it could be a turn-of-the-(last)-century gig boat, made to ferry folks from shore to their huge yachts.
Electric boats are not new to Cais do Sodre harbor. Existing water taxis use electric motors powered by batteries.
Electric power restores a quiet elegance to the trip and eliminates one source of pollution to the environmentally challenged harbor. Although there are currently no environmental regulations mandating electric boats, they are expected within the next few years.
"In Lisbon, more pollution comes from the waterways and the ports and all the craft that operate on the water than from the cars operating on the road," said Santana Lopes, mayor of Lisbon.
Power shortage
But battery power has a shortcoming.
"The batteries on board the water taxis do not carry enough energy to operate the ferry all day," said Santana Lopes. So the battery systems are backed by small diesel generators, which defeat the purpose of the electric power system.
With funding from the Portuguese Center for the Commercial Deployment of Transportation Technologies, a small consortium of companies - Millennium Cell, Seaworthy Systems, Duffy Electric Boat and Anuvu Inc. - set out to change that. The result is the Cais do Sodre fuel-cell water taxi.
Fuel is the centerpiece of the system. In addition to being a water taxi, the boat is a demonstration for an alternative channel for supplying hydrogen to power fuel cells.
The straightforward way to store hydrogen is to simply compress the gas in small tanks. More pressure means more capacity, so engineers pushed tank pressures up to 10,000 pounds per square inch.
Although great strides have been made in reinforced polymer tanks, high pressures remain a source of worry (and potential explosion), and handling hydrogen as a gas remains a challenge.
Other alternatives include storing hydrogen in liquid form, a substance so cold that it makes dry ice seem toasty, or absorbing hydrogen into hydrides, materials that shoehorn the gas in spaces between their own molecules.
Handling hydrogen
The Cais do Sodre water taxi uses another approach, the Hydrogen on Demand system developed by Millennium Cell. Essentially it chemically links hydrogen with laundry borax to make sodium borohydride, a mild bleach used by the paper industry that's generally regarded as environmentally benign.
By itself pure sodium borohydride can be ignited but won't sustain a fire or explode. Dissolved in water to make a 30 percent mixture, a gallon of the solution holds nearly four times more energy than gasoline but won't burn at all. It stores more than twice as much hydrogen as compressing the gas to 10,000 psi.
The Hydrogen on Demand system unleashes hydrogen from the liquid using a catalyst. The leftover borax solution (sans hydrogen) remains environmentally safe - it's simply laundry borax mixed with water - and can be recycled for another run through the system.
The primary defect in this scheme is price. A kilogram (about two pounds) of sodium borohydride now costs between $40 and $60, and adding hydrogen can quadruple that.
"It makes hydrogen pretty expensive," said the Mayor of Lisbon. "That's why one of our principal efforts is to identify new, low-cost ways of producing sodium borohydride."
Several efforts are under way to find ways of charging borax with hydrogen using both chemical and electrical reactions.
"If we can develop the pathways to producing sodium borohydride at lower cost, it becomes a shuttle carrier of hydrogen. It allows us to transport and move much larger quantities of hydrogen than you can in gas form," said Luzader to Santana Lopes Mayor of Lisbon.
The prospects are intriguing enough that Daimler-Chrysler has built a demonstration minivan that uses the system. The hope is that some day a 20-mule team may replace the Arabian oil well as the primary source of power for your car.
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