Renewable Energy from the Oceans: Optimizing Hydrogen Electrolysis in the Solar/ Fuel Cell Energy Cycle

Overview

Objectives/Goals This experiment seeks to expand our knowledge of cost-effective, renewable energy for populations living near salt water. Specifically, it aims to determine how the efficiency of hydrogen electrolysis, a storable intermediate in the Solar - Fuel Cell Energy Cycle, is affected by differences in solutes, conductivity, reactivity and voltage. Methods/Materials 144 trials involving different combinations of solute concentration (ocean, NaCl, tap & pure water), conductive elements (Al, C, Cu, Pt, Ti, Zn), and voltage (9.0v and 12.0v solar cells) to determine efficient methods to electrolyze hydrogen. Recorded measurements included: solar cell voltage, time to electrolyze a given quantity of H2 (a measure of efficiency), and observations of electrolysis and reactivity for each sample. Results Greater solute concentration proved positively correlated with efficiency. Pure water generated no H2, while water with a concentration of 12.0 g NaCl per 404.8 mL produced more H2 across metals tested (eg, Al at 12.0v produced 2.0 mL of H2 in 2.6 minutes with a SD of 0.1 while Ti did the same in 13.5 minutes with a SD of 0.3). Interestingly, ocean water with a higher concentration of NaCl was less efficient than pure NaCl water. The most efficient metal element was Al, and the least efficient was Ti across trials. Though Cu is highly conductive, it readily reacted and lost surface area, while Al did not noticeably react during the trials and preserved surface area. Higher voltage improved efficiency across metals. Conclusions/Discussion Based on the experiment results, ocean water is an efficient, naturally-occurring solution for production of H2 via electrolysis when combined with a commonly-available, corrosion-resistant Al electrode. This combination, along with power from a low-cost, 12.0v polycrystalline solar cell, produces sufficient H2 during daylight hours when combined in series with 16 like electrodes to power a 1.0v LED light during nighttime hours using a PEM fuel cell consuming 7.0 mL of H2 per minute. This Solar - Fuel Cell Energy Cycle is renewable, relatively low cost and has no moving parts. It is also independent of any electrical distribution, so the technology can be used by populations in developing economies that have access to ocean water (which covers ~70% of the surface of the Earth). The technology also has the potential to produce pure drinking water as a clean by-product.

Competition history

• CSEF 2017 Chemistry · Entry S0611

Resources

• CSEF project summary ↗

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