Two amateur divers were able to test the prototype of the artificial kelp photovoltaic solar cell’s performance in the Gulf of Mexico off the coast near Corpus Christie, Texas. This is the second dive but the first successful test, as one diver’s buoyancy control device malfunctioned during the first dive.
The Solar Seaweed experimental equipment currently integrates four small flexible solar panels just under a meter in length (using Konarka‘s Power Plastic). The current testing panels are commercial off-the-shelf designs that are too thick for effective wave power testing, so the piezoelectric film was not employed during this experiment.
For the test, I placed two panels back to back and two lower in the water along a weighted pair of lines, each panel was enveloped in a translucent airtight bag together with a digital multi-meter able to display current and voltage readings recorded by the divers. The dive was performed between 1pm and 3pm on a cloudless day with wind speeds under 5 mph to allow data collection without additional external factors. Two rounds of data collection were conducted, each across a 30 minute window by incrementally dropping the panels from surface level to 30 feet submerged and tracking power output from each panel at 3 foot increments.
During the second test, the enclosure for one of the lower panels leaked and filled the protecting bag with seawater. This created a short-circuit in the electrical connection between the panel and its monitor, eliminating data collection on that panel during the second test period. The operation of the other three panels followed the same pattern between both tests so the loss of one panel did not invalidate the experiment’s results. This was merely a proof of concept test – obviously a full test would require additional time in the water, a larger panel extending along a greater segment of the water column, and a much higher resolution in data gathering at varying depths.
The same testing results from land-based experimentations were visible again – notably that the photovoltaic panels produce slightly higher power output when minimally submerged compared to their in-air operation before immersion due to the drop in temperature afforded by the water. Descending to a depth of 6ft, the silt and natural occlusion of solar illumination through the water was relatively minimal. The two back-to-back panels proved an interesting bit of data – the side facing away from the sunlight produced almost 40% of its normal power output due to light deflected by the waves to fall on its surface even when turned away from the sun.
One diver was able to descend and release a stream of bubbles roughly four feet in front of the panel, which increased the output slightly through greater reflection of the incoming light. Further experiments to test the effectiveness of air bubble light focusing will be performed later under controlled conditions.
Below 6 ft, the power output began to decrease fairly steadily, falling below 3% of surface level power output at the end of the 30 ft descent. A small non-flexible silicon solar cell included with the paired flexible panels showed a slightly higher rate of drop-off, but the Konarka panels are created using several layers of PV ink – which are sensitive to a different spectrum of light than the silicon cells based on experiments conducted using sunlight filtered through a prism and a narrow aperture by some of my local Boy Scouts working on their Energy merit badge.
The test was successful in proving the potential for photovoltaic solar power production in submerged panels like those in the Solar Seaweed design. I am very thankful for the Aggie divers who volunteered their time and assistance in testing this design, as well as to all of the supporters of my crowdfunding effort whose money paid for the tank recharge and boat rental fees for this test!