Semi-solid flow cells aim to replace the gas-guzzling internal combustion engine with electric motors driven by pumpable fuels that bear electrons as their active elements.
Electronics has already transformed society. By harnessing electricity to perform the operations that were once performed manually, computers have made obsolete legions of mechanical devices, from adding machines to carburetors. Now electronics is poised to replace the gas-guzzling internal combustion engine with electric motors driven by pumpable fuels that bear electrons as their active elements.
Indeed, if an ambitious startup with MIT roots and DOE funding has its way, within five years you may see a new pump, labeled Cambridge Crude, appear next to those for the lead-free and diesel at your local service station.
|Cambridge Crude (in bottle) is a liquid electrolyte that flows through a reactor, where a copper electrode (top) and an aluminum electrode (bottom) extract electrons to power an electric motor or any other dc load. The reactor draws the electrons as they blow through its center. The nanoscale carbon particles in the liquid complete the circuit between the Cu and Al collectors. SOURCE: MIT
Ever since Italian physicist Alessandro Volta invented the electrochemical cell in 1792, voltage per cell has been restricted by the chemical reaction. The typical limit for the vast majority of battery chemistries is 1.5 volts; modern lithium-ion batteries achieve 3.6 V per cell, albeit at a trade-off of a much higher cost per kilowatt-hour.
The term battery predates even Volta’s work. It was coined by Benjamin Franklin, who in 1748 used Leyden jars to capture electrons discharged during lightning storms, yielding what were effectively the first manmade capacitors. Franklin came up with the idea of wiring individual cells in series to vault the voltage-per-cell barrier. Volta subsequently wired his own electrochemical cells into series, which he called piles. Unfortunately, this description of common battery structures is as true today as it was in the 19th century; wiring cells in series remains the only way to boost voltage, at the cost of limiting the battery’s overall reliability to that of its weakest cell.
Though the battery landscape hasn’t changed much in 200 years, it hasn’t been for lack of trying. Since 2009, the Department of Energy’s Advanced Research Projects Agency for Energy (Arpa-E) has averaged more than $350 million in funding per year for investments in hundreds of three-year projects. Experiments thus abound to improve battery technology, but none has yet achieved energy densities anywhere near the $50/kWh cost point that would permit widespread commercialization.
In its report for fiscal year 2010, Arpa-E indicates that one of the biggest awards was for a $7.2 million effort at EaglePicher Technologies LLC (Joplin, Mo.), in cooperation with Pacific Northwest National Laboratory, to develop a planar version of the tubular high-temperature sodium beta battery that would increase that battery technology’s reliability and lower its currently high cost for large-scale grid storage applications.
The second biggest award, $6.9 million, was for another grid-battery project at the Massachusetts Institute of Technology. Called Electroville, the liquid battery technology is designed to buffer usage fluctuations in neighborhoods, much as a bypass capacitor does for printed-circuit boards.
Arizona State University (Tempe), meanwhile, has a $5 million Arpa-E-funded project under way to perfect metal-air ionic liquid batteries that substitute earth-abundant materials for the rare lithium used in hybrid vehicles today, with a promise to increase the range of electric vehicles to almost 1,000 miles while potentially decreasing the cost compared with those incurred by today’s grid-recharged vehicles.
Two other Arpa-E-funded efforts are aimed at improving the performance and lowering the cost of today’s state-of-the-art lithium-ion batteries. A $4 million project at Envia Systems (Hayward, Calif.) aims to increase the energy density of Li-ion from 150 Wh/kg to more than 400 Wh/kg through the use of nanopatterned silicon-carbon electrodes. And a nearly $2 million project at Inorganic Specialists Inc. (Miamisburg, Ohio) is developing silicon-coated carbon nanofiber paper material that promises to boost the storage capacity of Li-on batteries fourfold.
None of these efforts, however, hold a candle to the promise of Cambridge Crude, a $2.5 million Arpa-E funded effort at 24M Technologies Inc. (Cambridge, Mass.) to perfect a battery technology for all-electric vehicles that would turn electrons into a fuel that could be pumped like diesel or gas. The ultimate aim is to render gasoline obsolete.