Storing the Sun's energy in zinc-based fuel cells
The Energy, Environment and Sustainable Development Programme sponsors R&D projects that aspire to make Europe more energy efficient and thus more competitive. Solar energy is a promising source of renewable energy, but since the Sun doesn't shine at night it is necessary to store the energy captured during the day. A prototype solar reactor was developed in the context of the SOLZINC project that utilises the Sun's energy to reduce zinc oxide to zinc. The zinc can then be used to make fuel cells that later release the stored energy. Plasma specialists with ScanArc in Sweden were assigned the task of converting the zinc vapor produced by the reactor into a form usable for constructing the fuel cells. The use of carbon as a reducing agent in the solar reactor means that carbon monoxide (CO) and hydrogen gas (H2) can contaminate the zinc vapor conversion process. The Swedish engineers resolved this issue by dissolving the zinc vapor into liquid lead using spray condensers. Tests indicated that ScanArc's own spray condenser was the most efficient due to its low sensitivity to oxidizing gases. Once condensed into metal form, the zinc must then be powderised. Trials by ScanArc revealed that while this procedure is possible, it is expensive and reduces the attractiveness of the entire solution. Thus, they turned their attention to direct conversion of the zinc vapor into powdered form. Fine-tuning of a commercially available powderiser (Harzer Zinc) enabled stable production of high quality (95% purity) micron-sized particles. Securing this result marks an important step towards demonstrating the overall viability of the solar reactor concept.
