In 2012, Scientists developed photovoltaic cells that produce energy 9 meters under water. Most of us are aware of the rooftop solar systems and the rapid pace at which Australian homeowners are adopting solar power for their homes. More recently, we have also seen reports that the Victorian state government is planning to run the tram system in Melbourne wholly using solar energy by the year 2018. A common factor that links all these is the solar panels being exposed to sunlight either from the rooftop or other industrial scale installations. But, what we may not have noticed is that research on tapping solar energy is not limited to conventional uses and explores an array of other possibilities.
High bandgap solar cells
Some time ago, researchers at the NRL (Naval Research Laboratory) developed what is known as high bandgap solar cells that could produce adequate power for operating electronic gadgetry at a depth of 9 meters from the surface of the sea. This development is considered particularly significant because sensor platforms and autonomous systems working underwater are severely impacted by the absence of power source with long endurance. Up till now, these systems had to rely exclusively on power from on-shore sources, solar energy from a platform above the surface of the water of batteries. Earlier efforts to deploy photovoltaic cells were only partially successful primarily because the sunlight could not penetrate through water and solar cells that were optimised towards terrestrial solar spectrums.
Converting underwater photons
Philip Jenkins, who heads the Imagers and Detectors Section at NRL says that there is an acceleration in using autonomous systems for providing long-term environmental monitoring and situational awareness in underwater regions. He added further that as sunlight is absorbed by water, developing solar cells that could efficiently convert the underwater photons into electrical energy was the technical challenge.
Concerning absolute intensity, in marine conditions, solar radiation tends to be lower with narrow spectral content. When solar cells are matched well with the wavelength range, the conversion efficiency can be significantly higher on account of the narrow spectral content and lower solar radiation. Previously, the effort to employ solar cells in underwater environments focused on crystalline solar cells (silicone) though amorphous silicon cells were used in recent times.
Gallium indium phosphide
High-quality GalnP (Gallium indium phosphide) cells are better suited for operations underwater. These cells provide high quantum efficiency in the 400-700 nanometers wavelengths and dark current that is intrinsically low which is a critical factor to get higher levels of efficiency in conditions of low light.
Underwater, the filtered spectrum of sun rays have a bias towards green/blue portion, and therefore, the higher bandgap cells like GalnP can perform significantly better compared to the convention silicon cells, says Jenkins.
The world is indeed focusing increasingly on many more innovative ways to tap solar energy in the medium as well as large scale.
Solar panels on top of the 19,000-kilometre canal network of the Narmada canal project in the Indian state of Gujarat is considered an exceptional effort. Both, regarding its innovativeness as well as its ability to save large tracts of land, and water which would otherwise have been lost due to evaporation, by utilising the canal top for installing the solar panels over such a large length. While those are the quantifiable benefits, the project also brings along tertiary benefits like reduced carbon emission, an ability to create clean lung space for the local population, etc. This project has also received global accolades for the innovative measures adopted including, from the UN chief.
Another exciting innovation is floating solar power generation systems. This method involves installation of solar panels that float on lagoons, ponds or lakes. The performance of these panels is better regarding energy produced because they are naturally cooled. Additionally, the panels act as a shade for the water limiting the growth of algae and help reduce evaporation. This system has already been put to use in many environments where water bodies were readily available for installation of solar panels. Consequently, the owners could use valuable space which would otherwise have been taken up by the solar panels.
Solar energy gaining at the cost of fossil fuels
According to EuroSolar Group, a common thread running between these innovations is the fact that solar energy is receiving more and more attention globally. As we all do know, the raw material for solar energy – sun rays are available free of any cost and can last as long as this universe does. On the flip side, however, the proliferation of solar energy would potentially deal a body blow to those engaged in everything concerning fossil fuels. The Australian coal industry, for one, is already facing the prospects of stymied growth