Powering Human Civilization in the 21st Century: Unfolding Trends

During the 20th century, world primary energy consumption has increased over ten times, leading to an unprecedented improvement of the quality of life in some regions of the world. This was made possible thanks to a massive exploitation of fossil fuels that, in the decades to come, has to be significantly moderated due to environmental constraints, particularly anthropogenic climate forcing.1 Solar energy, in its multifaceted forms, is the most abundant, reliable, sustainable, and safe primary energy source that can profitably replace fossil fuels.2,3 The transition to a solar-powered world will be a long and difficult process4 in which some key trends can be envisaged: (1) growing share of electricity in energy end use;5 (2) increase of efficiency in energy production and consumption;2,3 (3) establishment of technologies for the manufacturing of "solar fuels";6,7 (4) recycling of the equipment used for converting renewable energy flows, that is often made of materials available in very limited supply (e.g. precious metals).8 The solutions to the tremendous challenge of energy transition require the mobilization of huge human and economic resources in all scientific and technological fields. In this wide context, one selected example will be briefly presented, related to materials for energy-efficient lighting technologies.9 1N. Armaroli and V. Balzani, The legacy of fossil fuels, Chem.-Asian J., 2011, 6, 768-784. 2N. Armaroli and V. Balzani, Energy for a sustainable world. From the oil age to a sun powered future, Wiley-VCH, Weinheim, 2011. 3N. Armaroli, V. Balzani and N. Serpone, Powering planet earth - energy solutions for the future, Wiley-VCH, Weinheim, 2013. 4N. Armaroli and V. Balzani, The future of energy supply: Challenges and opportunities, Angew. Chem. Int. Ed., 2007, 46, 52-66. 5N. Armaroli and V. Balzani, Towards an electricity-powered world, Energ. Environ. Sci., 2011, 4, 3193-3222. 6J. Barber, Photosynthetic energy conversion: Natural and artificial, Chem. Soc. Rev., 2009, 38, 185-196. 7RSC - Royal Society of Chemistry, Solar fuels and artificial photosynthesis: Science and innovation to change our future energy options, 2012, http://www.rsc.org/ 8B. K. Reck and T. E. Graedel, Challenges in metal recycling, Science, 2012, 337, 690-695. 9R. D. Costa, E. Orti, H. J. Bolink, F. Monti, G. Accorsi and N. Armaroli, Luminescent ionic transition-metal complexes for light-emitting electrochemical cells, Angew. Chem. Int. Ed., 2012, 51, 8178-8211.