Princeton University researchers have devised a more efficient method for harnessing sunlight to convert carbon dioxide into an alternative fuel precursor known as formic acid. The researchers in the laboratory of Andrew Bocarsly, a Princeton professor of chemistry, collaborated with start-up company Liquid Light Inc. of Monmouth Junction, N.J.

The Princeton photovoltaic-electrochemical cell system. With graduate student James White, Professor Andrew Bocarsly and principal engineer Paul Majsztrik from Liquid Light.  Image Credit: Frank Wojciechowski  Click image for the largest view.

The Princeton photovoltaic-electrochemical cell system. With graduate student James White, Professor Andrew Bocarsly and principal engineer Paul Majsztrik from Liquid Light. Image Credit: Frank Wojciechowski Click image for the largest view.

The transformation from carbon dioxide and water to formic acid was powered by a commercial solar panel that can be found atop electric poles across New Jersey, generously provided by the energy company PSE&G. The process takes place inside an electrochemical cell, which consists of metal plates the size of rectangular lunch-boxes that enclose liquid-carrying channels.

Bocarsly explained that to maximize the efficiency of the system, the amount of power produced by the solar panel must match the amount of power the electrochemical cell can handle, an optimization process called impedance matching.

The team’s research paper has been published in the  Journal of CO2 Utilization.

By stacking three electrochemical cells together, the research team was able to reach almost 2 percent energy efficiency, which is twice the efficiency of natural organic photosynthesis. It is also the best energy efficiency reported to date using a human-made device.

Photovoltaic Electrochemical Cell System Closeup and Energy Flow at Princeton. Image Credit: Andrew B. Bocarsly, Princeton University.  Click image for the largest view.

Photovoltaic Electrochemical Cell System Closeup and Energy Flow at Princeton. Image Credit: Andrew B. Bocarsly, Princeton University. Click image for the largest view.

Bocarsly said using waste carbon dioxide and easily obtained machined parts, this approach offers a promising route to a renewable fuel.

A number of energy companies are interested in storing solar energy as formic acid in fuel cells.

Note that formate salt, a product readily made from formic acid is the preferred de-icing agent on airport runways because it is less corrosive to planes and safer for the environment than chloride salts. With increased availability, formate salts could supplant the more harmful salts in now in widespread use.

The press release is pretty thin on data and the paper’s abstract even thinner. No mention is made about the CO2 source or the CO2 condition. The problems that bedevil other ideas is the CO2 purity. Atmospheric CO2 is a very small fraction of the air with an abundance of nitrogen, oxygen, water vapor and the minor gases the massive fraction. Combustion flue gas is even messier. The ideas to come out so far haven’t offered a mass market or scalable CO2 source solution.

A solid 1.8% efficiency is interesting news with congratulations earned and sent. Now if we could get a little info on the CO2 we’d know how exciting the new technology really is. Two percent efficiency might be good enough if the CO2 cost is low enough.

 


Comments

1 Comment so far

  1. Jagdish on July 3, 2014 5:11 AM

    Collection of CO2 may require more energy. CO2 is, in any case, the lowest energy form of carbon.
    It may be preferable to collect waste biomass from agriculture or forest and wet grind it to a slurry for carbon input.
    If any process can covert it to a liquid fuel with higher calorific value than the brickets made from the same substance, it might be useful.

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