A new approach to storing electrical energy can store more energy than gasoline in the same volume, and could help extend the range of electric vehicles. But some experts say other approaches are more practical.
The biggest technological hurdle facing electric vehicles is their range. Even the best rechargeable batteries cannot match the density of energy stored in a fuel tank.
Combining electric power with a combustion engine to make a hybrid electric vehicle sidesteps that problem. But a new take on electrical power storage that is part , part chemical could ditch gasoline for good.
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The new design stores energy more densely than petrol, and was conceived by of the University of Massachusetts, Boston, and colleagues.
Gasoline beater
Batteries produce electricity from a closed chemical system that is eventually exhausted. Fuel cells use a constant supply of fuel, so they are continually topped up. Licht鈥檚 cell has features of each.
Its negative electrode, or anode, is made from vanadium boride, which serves double-duty as a fuel too. But unlike the flowing fuel of a fuel cell, the material is held internally, like the anode material of a battery.
The vanadium boride reacts with a constant stream of oxygen, as in a fuel cell, provided by the positive electrode, or cathode. This brings in a supply of air from outside.
The cell has a theoretical energy capacity of 27 kilowatt hours per litre, compared to 9.7 kilowatt hours per litre for gasoline. But both approaches are limited by practical factors to smaller figures.
Licht says his new system would likely have a practical energy capacity of around 5 kilowatt hours per litre. 鈥淏ut that鈥檚 two-fold higher than the practical storage capacity of gasoline,鈥� he says.
Electrode refill
He imagines drivers swapping exhausted vanadium boride electrodes for fresh ones at filling stations. The old electrode can be chemically regenerated for reuse. Consumers are more familiar with a mechanical process like that than with recharging a battery, Licht thinks.
, a fuel cell specialist at the University of Washington, says Licht鈥檚 way of thinking makes sense, 鈥渆specially the estimates of practical efficiencies鈥�.
, a specialist in fuel cells and advanced battery technology at Pennsylvania State University, says the design is interesting, but adds that vanadium boride may take more energy to create than gasoline.
, an electrochemist at the University of Southampton, UK, thinks the results are less impressive than they seem.
He says that other designs could yield even higher energy densities than the vanadium boride system. A lithium-air cell should give twice the energy density of a vanadium boride-air cell. 鈥淎luminium-air also gets close, and that is a well-established and large-scale technology,鈥� says Owen. 鈥淢oreover, aluminium recovery is already done on a very large scale.鈥�
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