A mash-up of techniques at the bleeding edge of quantum physics and genetic engineering could radically boost the efficiency of solar cells.
Electrical engineers and materials science researchers have for years striven to boost the efficiency of solar panels—in other words, the percentage of solar energy that is received by a photovoltaic cell (the basic unit of a solar panel), that is transformed into usable electrical energy. Typical solar panel efficiency ratings hover around 14-18 percent efficient—a capture rate that leaves over 80 percent of incoming energy “on the ground”. Even the best panels only operate at just under 45 percent efficiency, and only in laboratory conditions. Although this is a major barrier to wider solar adoption, the good news is that advances in efficiency tend to lower the cost, as higher efficiency means fewer panels need to be installed for a similar output .
Plants work differently. They harness energy from the sun via photosynthesis with near 100 percent efficiency. Replicating such levels has long been the Holy Grail of the photovoltaic energy sector, a quest that has largely remained within the realm of fiction. In 2010, Booker-Prize-winning writer Ian McEwan published “Solar”, a novel whose main character was a physicist who purported to have achieved precisely this breakthrough.
When a photon of visible light hits a plant’s light-sensitive chromophores – parts of certain molecules that can absorb specific wavelengths–– it is converted into an ‘exciton’. In essence, an exciton is an electron that moves from its lowest energy state to a higher one, whereupon it engages in a ‘quantum walk’, jumping from chromophore to chromophore until it gets to the part of a cell where it is trapped and converted to chemical energy that can be used later. During the quantum walk, the exciton’s weird property of existing as both a particle and a wave at the same time permit it to simultaneously ‘try out’ many different routes, and then ‘choose’ the path that has the greatest probability of getting to its terminus in the least time.
It is this quantum walk that allows plants to achieve such incredible efficiencies, and it was that natural phenomenon that captured the interest of MIT researchers who reported this week in a paper published in Nature Materials that they had synthetically replicated the process. Following a chance meeting at a conference, an expert in re-engineering viruses, Angela Belcher, and one of the world’s leading theoretical physicists, Seth Lloyd, began to work together to alter viral DNA so that it would bind to chains of synthetic chromophores. The correct spacing of the chromophores is key, and by matching different engineered varieties of a virus with different chromophore spacings, they eventually doubled exciton speeds over those in existing solar cells.
The viruses currently can only transmit energy, but not harness it, so the next step will be to add a reaction centre to the end of the virus, as in plants, where such capture could take place.
The MIT researchers are not the only ones pushing forward with advanced solutions to our clean-energy needs. A profile of Burnaby-based General Fusion appeared in the Vancouver Sun this week, cheering on its aim of building the world’s first commercial nuclear fusion reactor. Nuclear fusion, the process that powers the Sun, works by merging two or more atomic nuclei of light elements together to form the nucleus of a heavier element. Matter is not conserved in light-element fusion reactions; some of the matter of the fusing nuclei is converted to energy that ideally can be captured and used.
Commercial-scale fusion has long been the other Holy Grail of advanced energy technologies. But the enormous energies, pressures and temperatures required to “mimic the Sun” and overcome the powerful repulsion between two or more protons at the heart of an atom has for decades kept commercializing the technology ‘just a few decades away’. The European Union is currently leading an international effort to realize the fusion dream via its ITER project, which is already billions of euros over budget. Meanwhile, Burnaby-based General Fusion has spent just a fraction of such sums, albeit more than $100 million, on an approach known as magnetized target fusion. The company’s technique is based on establishing nuclear densities, temperatures and confinement times via common industrial technologies that offer a much lower cost path to the production of viable fusion power.
The Climate Examiner speaks to BC-based Carbon Engineering about the technology, the business and the policies that could make direct air capture, synfuels and carbon sequestration work.