(Note: The audio and the PowerPoint presentations of these talks are posted on the MRS website)
A special Energy Forum was held on Monday, March 24, at the 2008 MRS Spring Meeting in San Francisco. Four speakers, George Whitesides (Harvard University), Chris Somerville (University of California—Berkeley), Daniel G. Nocera (Massachusetts Institute of Technology), and Martin Green (University of New South Wales, Australia) presented talks on various aspects of Energy to a packed and overflowing room. Below is the report on the forum published in the MRS Meeting Scene E-Newsletter.
MegaMonday got off to a strong opening with four lectures focusing on the critical problem of energy. The MRS Bulletin has just released a special expanded issue of the MRS Bulletin on the topic of "Harnessing Materials for Energy." The Energy Forum was organized to complement this special issue and featured four talks by scientists and researchers exploring different areas in energy. Using the metaphor of energy as a large puzzle, with various technologies forming pieces of this puzzle, the forum explored how these pieces could fit together to solve what is arguably humankind's greatest near-term challenge, namely energy generation with minimal impact on the environment.
Delivering the opening remarks to a full house, George Crabtree from Argonne National Laboratory emphasized the role of materials in possible solutions to the global energy crisis. He stressed that global energy needs are expected to double by 2050 and triple by 2100, driven especially by the growing energy needs of developing countries.
George Whitesides from Harvard University delivered the first lecture of the Energy Forum and succinctly outlined the opportunities for materials science in energy, sustainability, and global stewardship. He emphasized that issues such as energy, climate, water, and sustainability are fundamentally interconnected and that these are enormous problems with the potential to bring great conflict. Whitesides proposed the formula, well-being = available energy/number of people, and stressed that there is a great need to both produce more energy as well as conserve energy that is currently being produced. In particular, the scarcity of water threatening several parts of the world has the potential to further exacerbate the energy crisis since significant energy may have to be invested in water production in the future.
Whitesides went on to outline the major sources of energy that are currently used along with the outlook for these energy sources over the next few decades. Fossil fuels such as hydrocarbons, coal, and gas are the mainstay of our current energy needs, but it may well be that their role in inducing deleterious climate change makes them unviable options in the very near future. Furthermore, nuclear energy is plagued by concerns about proliferation and waste disposal, whereas hydroelectric power generation is currently almost at peak capacity. Solar energy represents a promising alternative but very significant improvements in the design and cost of solar cells are required to harness the dilute energy of the sun. Whitesides emphasized that notwithstanding the claims of a hydrogen economy, it is important to realize that hydrogen is a method of transporting energy and not a source of energy. In that sense, hydrogen is really like electricity—it is not a solution by itself to the global energy problem.
In the short term, he proposed that more research attention be focused on the conservation of energy, such as the development of materials that reduce the tremendous power losses during transmission and the design of better illumination sources such as bright light-emitting diodes. There is also a great need to globally develop carbon management strategies to deal with the CO2 being released into the atmosphere by burning fossil fuels. Whitesides outlined several topics that he believed are fertile grounds for the next generation of material scientists, including catalysis, separations, development of materials with extreme properties, being able to move electrons more efficiently in matter, scaling to nanoscale dimensions, and matching the complexity of biological processes such as photosynthesis. Given the current corporate atmosphere that emphasizes short-term returns, Whitesides stressed that this effort will have to be lead by research universities, perhaps in collaboration with venture philanthropic organizations and local and federal government. “The good news is that this is an issue that the public deeply cares about in one form or the other”, said Whitesides, “the problem is that even if we apply all that we know, we still come up short,” adding that since the basic knowledge does not exist, we have no alternative but to go out and create new knowledge to solve these problems.
BIOFUELS and BIOMASS
Chris Somerville of the University of California—Berkeley discussed the area of biofuels. With the recent world-wide increases in the cost of petroleum and related fuels, ethanol has very much been in the news. However, grain-based ethanol directly affects the food chain. Somerville then focused on cellulosic fuels as an alternative to grain-based sources. In particular, he discussed Miscanthus, which is a perennial grass and which can yield over 26 tons/acre of land without irrigation, which two and a half times as much as switchgrass. He ran though the process of producing syngas using cellulosic sources. He also discussed the problems and issues associated with breaking down cellulose to yield fuel. Somerville touched upon an alternate to ethanol in the form of alkanes.
He concluded by describing his visions for the field. This includes replacing grain-based fuels by cellulosic fuels thereby disassociating biofuels from the food chain. It also includes greater use of sugarcane which reduces the area of land used and which yields both sugar and cellulose. He hopes that biodiesel can be obtained from cellulosic sources rather than vegetable oils. He also believes that ethanol as a fuel can be replaced by other options such as alkanes. Finally, synthetic catalysts can make a big difference in the business of producing fuels from biological sources.
The broad field of catalysis was discussed by Daniel G. Nocera of the Massachusetts Institute of Technology. In terms of the environmental issues relating to fossil fuels, it is the CO2 content that is of concern. The only solution is to cut the tie between energy use and carbon. Solar energy is the only sustainable, renewable, and carbon-neutral source of energym, whether it is biomass or photovoltaics. The highest energy density is achieved in chemical bonds. Nocera described photosynthesis and attempts to create artificial photosynthesis. At its very essence, solar energy conversion boils down to water splitting. The basic science for this requires multi-electron proton-coupled electron transfer. He described in some detail work done by his group as well as other groups on O-O bond manipulation which is important in biological photosynthesis.
In conclusion, Nocera offered several take-home thoughts. The current need for energy is so enormous that conventional, long-discussed sources will not be sufficient. New science is required for this purpose. Solar (direct) + water (indirect) has the capacity to meet future energy needs. However, large expanses of fundamental science need to be discovered. According to him, renewable energy research not an engineering problem, rather, it needs to be tackled as a basic science problem and new materials, catalysts and many new modes of reactivity await discovery. Finally, as per Nocera, Chemistry is the central science of energy because it involves light capture and conversion with new materials, and energy storage in bonds or new materials.
The fourth presentation of the MRS Energy Forum was on Solar Technology by Prof. Martin Green, Research Director at the Photovoltaic Centre of Excellence at the University of New South Wales, Australia. Green gave a comprehensive overview on the current and future opportunities of photovoltaics, predictions and new trends in solar technology including inorganic, organic and hybrid systems thereof. “Can Photovoltaics power the Future?” was his provocative question to introduce his talk in front of a packed auditorium with over 400 attendees and commenced with a clear “Yes”! The green energy market is booming with growth rates around 40% over the last decade with direct water heating being the largest application due to an Australian process that the Chinese adopted and continue to implement rapidly which represents by far the largest market. The picture on solar cell production gives a similar picture: Japan with 36%, followed by Germany with 20% and China with 15%. Asia overall has a market share of over 63% in 2006 compared to the USA with just 6.8%. The world energy needs could be satisfied by a square with a 700 km baseline (10% efficiency). Comparing concentrator cell technology and just looking at the mirror cost (troughs at $250/m2; flat mirrors at $40/m2) not to mention durability in a dessert climate with significant erosion indicates that direct conversion with low cost thin film solar cells appears the solution to become economical competitive. However, current installation costs are too high and only competitive in remote areas where grid connection would be even more expensive. PV power cannot compete on wholesale but at retail price. In Italy for example, the current power cost per kW is with 22 cts already overlapping with PV power cost. The demarcation line of profitability has started to move up through Europe. The cost of power in Germany has actually dropped over the years and the government has tapped into that funding source by raising taxes and using some of those funds to support green energy development and implementation especially wind and solar power. In the US, Macy's, as the first large corporation, has gone green with 26 stores.
Silicon is still the predominant solar cell material now outpacing computer applications by volume, which has put pressure on supplies. This has led to efforts for making solar cells as thin as possible, currently at 200 microns and targeting 100 micron thickness in the near future. In addition, metallurgy grade still works well for solar cells moving away from the much more expensive semiconductor grade material. This has led to the search for cheaper alternatives such as amorphous, microcrystalline, and polycrystalline materials, however, they do come with an efficiency penalty (~10% efficient) Other promising systems are CIS and CIGS [Cu(In,ga)(Se,S)2] with ~18% efficiency and CdTe (however, produced a Te shortage), dye sensitized (Grätzel) and organic solar cells. Green pointed out desirable properties such as low materials cost, abundance, non-toxic, large manufacturing capability, fully integrated modules, ruggedness and durability as well as high efficiency. He then took a look at reduction in cost per kW over the last 20 years to estimate future competitiveness: The early PVs were at 20,000/kW (1981) down to 3,000/kW (2002) with thin film systems having the potential to actually reach competitive prices with current gas turbines at some future point. Silicon is unlikely to get us there since the wafer costs are just too high and will not come down much further. He closed his presentation by touching upon several new concepts that show promise such as circulator approaches, hot carrier systems, thermal PV, thermionics, quantum dot systems, interband converters. Due to the high installation cost, market support is needed to help commercialize PVs with projections of 1% solar cell power generation by 2020 (Bavaria, Germany, not exactly a desert with a lot of sun, is already at 1.4%!), 25% by 2050 and 64% by 2100. We are already ahead of the first prediction. We can do our part to help continue to accelerate that trend.
Dr. Gopal Rao
Web Science Editor
Materials Research Society (MRS)