Nanotechnologies can be used to develop sustainable energy systems while reducing the harmful effects of fossil fuels as they are gradually phased out over the next century. This optimistic scenario is coming closer to reality as new technologies such as biomimetics and Dye Sensitized solar Cells (DSCs) emerge with great promise for capturing or storing solar energy, and nanocatalysis develops efficient catalysts for energy-saving industrial processes. Europe is ready to accelerate development of these technologies, as delegates heard at a recent conference, Nanotechnology for Sustainable Energy, organised by the European Science Foundation (ESF) in partnership with Fonds zur Förderung der wissenschaftlichen Forschung in Österreich (FWF) and the Leopold-Franzens-Universität Innsbruck (LFUI).
The conference focused on solar rather than other sustainable energy sources such as wind, because that is where nanotechnology is most applicable and also because solar energy conversion holds the greatest promise as a long-term replacement of fossil fuels. Solar energy can be harvested directly to generate electricity or to yield fuels such as hydrogen for use in engines. Such fuels can also in turn be used indirectly to generate electricity in conventional power stations.
“The potential of solar power is much, much larger in absolute numbers than that of wind,” said Professor Bengt Kasemo from Chalmers University of Technology and the chair of the ESF conference. However, like wind, the potential of solar power generation varies greatly across time and geography, being confined to the daytime and less suitable for regions in higher latitudes, such as Scandinavia and Siberia. For this reason there is growing interest in the idea of a global electricity grid according to Kasemo.
“If solar energy is harvested where it is most abundant, and distributed on a global net (easy to say – and a hard but not impossible task to do) it will be enough to replace a large fraction of today’s fossil-based electricity generation,” said Kasemo. “It also would solve the day/night problem and therefore reduce storage needs because the sun always shines somewhere.”
In the immediate future, solid state technologies based on silicon are likely to predominate the production (manufacture) of solar cells, but DSC and other “runners ups” are likely to lower costs in the long term, using cheaper semiconductor materials to produce robust flexible sheets strong enough to resist buffeting from hail for example. Although less efficient than the very best silicon or thin film cells using current technology, their better price/performance has led the European Union to predict that DSCs will be a significant contributor to renewable energy production in Europe by 2020.
The DSC was invented by Michael Grätzel, one of the speakers and vice chair at the ESF conference. The key point to emerge from the ESF conference, though, is that there will be growing choice and competition between emerging nanotechnology-based solar conversion technologies. “I think the important fact is that there is strong competition and that installed solar power is growing very rapidly, albeit from a small base,” said Kasemo.”This will push prices down and make solar electricity more and more competitive.”
Some of the most exciting of these alternatives lie in the field of biomimetics, which involves mimicking processes that have been perfected in biological organisms through eons of evolution. Plants and a class of bacteria, cyanobacteria, have evolved photosynthesis, involving the harvesting of light and the splitting of water into electrons and protons to provide a stream of energy that in turn produces the key molecules of life. Photosynthesis can potentially be harnessed either in genetically-engineered organisms, or completely artificial human-made systems that mimic the processes, to produce carbon-free fuels such as hydrogen. Alternatively, photosynthesis could be tweaked to produce fuels such as alcohol or even hydrocarbons that do contain carbon molecules but recycle them from the atmosphere and therefore make no net contribution to carbon dioxide levels above ground.
Biomimetics could also solve the longstanding problem of how to store large amounts of electricity efficiently. This could finally open the floodgates for electrically-powered vehicles by enabling them at last to match the performance and range of their petrol or diesel-based counterparts. One highlight of the ESF conference was a presentation by Angela Belcher, who played a major role in pioneering nanowires made from viruses at the Massachusetts Institute of Technology (MIT) in the US. Bizarre as it sounds, there is a type of virus that infects E.coli bacteria (a bacteriophage) capable of coating itself in electrically-conducting materials such as gold. This can be used to build compact high capacity batteries, with the added advantage that it can potentially assemble itself, exploiting the natural replicating ability of the virus. The key to the high capacity in small space lies in the microscopic size of the nanowires constructed by the viruses – this means that a greater surface area of charge carrying capacity can be packed into a given volume.
However, commercial realisation of biomimetic and other emerging technologies lies far in the future. But meantime, as delegates heard from several speakers at the ESF conference, nanotechnology has an important contribution to make, improving the efficiency of existing energy-generating systems during the transition from fossil fuels. For example, Robert Schlögl outlined how nano-scale catalysts can be used to improve the efficiency of engines or systems consuming fossil fuels.
Inspired by such presentations, delegates at the conference were unanimous in calling for a follow up. “The conference was regarded as a real success and a new proposal for a conference in 2010 (chaired by Grätzel) will soon be submitted,” said Kasemo. “In particular the conference inspired and educated young people, such as doctors, students, postdocs, young researchers, who will be the ones to realise the potential of nanotechnology for sustainable energy.”
The ESF-FWF conference in Partnership with LFUI on NANOTECHNOLOGY FOR SUSTAINABLE ENERGY was held at the Universitätszentrum Obergurgl, near Innsbruck in Austria during June 2008.