The $800,000 bi-annual Millennium Technology Prize, courtesy of the Technology Academy in Finland, was granted to Swiss researcher Michael Graetzel for the development of dye-sensitive solar cells (DSCs) which mimic photosynthesis to produce energy.
Rather than using silicon to capture and transport photons, as in traditional photovoltaic cells, DSCs use dye-based ‘chlorophyll’ combined with nanostructure ‘leaves’. The light-absorptive dye forms part of an electrolyte solution which absorbs photons from the sun to create carriers. The semiconducting titanium oxide nanocrystal ‘leaves’ then carry the charges to an external circuit, creating an electric current.
As yet, the dye-based technology is not quite as efficient as silicon-based cells. However, as the process does not require direct incidence of the photons, DSCs do not lose nearly as much efficiency under cloudy or indirect light, so a comparable maximum efficiency yields higher average energy than traditional cells. Furthermore, though industrial production commenced only in 2009, DSCs will cost much less to produce than traditional cells as the materials and manufacturing process are relatively common and inexpensive. For example, titanium oxide is already used as a paint base and is much cheaper to produce than silicon.
Another major advantage of DSCs is their versatility; as the dye can be incorporated into other materials, DSCs require no additional physical space. This characteristic has already been incorporated into mobile phones to generate power. One company has even included the cells in a backpack to power mobile electronics. Unlike traditional photovoltaics which stand as a separate installation, DSCs can be incorporated into windows, walls or other surface that are currently unused for this function. Larger-scale operations in buildings and other structures are expected to be a significant contribution to renewable energy portfolios by 2020. Potential applications are limited only by our imaginations.
There are a few key lessons here for budding engineers. The original research in photosensitive dyes commenced in the early 1970s as a response to the oil crises. Revolutionary changes take time: if you’re in it for a quick buck, it is much easier to adapt an existing technology, such as finding new materials with which to combine the dyes than to invent the technology yourself.
Furthermore, research interest and funding will generally be controlled by market factors. In this case, interest rose and fell with the price of oil and was not revived until the current environmental concerns and oil scarcity. With that said, students interested in materials research, or other technology which may not have immediately foreseeable commercial applications, can take heart that research today may drive monumental technological change decades from now.
Graetzel credits his inspiration to the natural world. Rather than trying to conquer the natural environment through raw human inspiration, he looked at what billions of years of evolution have to offer and saw how the idea can be adapted to human technology. A similar inspiration is behind the YeZ (mandarin for “leaf”), a concept car designed to be powered completely by photosynthetic processes. Whether you are a civil engineer drawing inspiration from a beehive, a chemical engineer mimicking photosynthesis, or an electrical engineer learning from bioluminescence, sometimes the solutions are already out there and just need to be found.
Sources
http://news.discovery.com/tech/windows-that-work-as-solar-cells.html
http://www.millenniumprize.fi/en/2010-prize/professor-michael-graetzel/ (Read the Whole Story PDF)
http://www.millenniumprize.fi/en/2010-prize/professor-michael-graetzel/innovation-4/
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