dimanche 14 décembre 2014

Is renewable energy really inexhaustible?

By Prudence Dato, prudence.dato@univ-savoie.fr, IREGE/University of Savoie (France).

  There exists a myth about renewable energy (RE) and the large benefit that our society could gain from renewable energy. Usually, we heard that renewable energy-let say solar energy or wind energy- is a clean energy and also a good alternative for oil because it is not polluting environment and is inexhaustible. It is true that our society could not escape the climate change consequences without adopting renewable energy which is seen as a promising solution. We always avoid some characteristics of solar/wind energy may be because we want to be optimistic. Those characteristics are for instance, the availability of inputs that could serve to produce renewable energy (solar/wind, metals, etc.). We commonly assume that solar/wind is always available (it is not so true), but clearly one should care about the availability of rare materials such as metals that need to be used to produce solar panels or wind turbines. For instance, Alonso et al. (2012) [1] projected that neodymium demand for wind turbines could grow by as much as 700 percent over the next 25 years; demand for dysprosium, also needed for wind turbines, could increase by 2,600 percent. Moreover, the production of 4 gigawatts (GW) of peak power using thin-film cadmium telluride photovoltaic requires 340 tons and 390 tons of cadmium and tellurium, respectively. However, it represents 2% and 82% of 2008 estimated world refinery production of cadmium and tellurium from primary sources[2]. The issue of exhaustibility of RE is close to the entropy pessimist view or strong sustainability arguments developed by Ayres (2006)[3] in the sense that a self-reproducing industrial system producing PV cells is not possible.

 For many centuries ago, the society was thinking that non-renewable energy such as oil was abundant and consequently they did not need to care either about its depletion or about the pollution it induces. At the end of the day, we get ourselves trapped by the challenge of climate change. So, now that we hope that an alternative is possible to escape the drama, are we going to get ourselves into the same situations as before? How are we going to produce renewable energy if in the future we completely deplete all the rare metals (that exists in a limited quantity)? Are we not just moving the problem of oil depletion to that of metals depletion? Also, note that all the manufacturing processes of solar panels or wind turbines are energy-intensive and partly rely on “dirty energy sources” with potential negative environmental implications.[4]Although, energy transition to clean energy is the ultimate solution for sustainable growth, we should start looking for how to optimally design the materials that serve to produce renewable energy in order to reduce the pressure on rare metals. Otherwise, the opportunity cost is going to be high in the case our society solely relies on renewable energy and misses rare materials.

[1] Alonso, E., Sherman, A. M., Wallington, T. J., Everson, M. P., Field, F. R., Roth, R., & Kirchain, R. E., 2012. Evaluating rare earth element availability: A case with revolutionary demand from clean technologies. Environmental science & technology, 46(6), 3406-3414.
[2] http://pubs.usgs.gov/circ/1365/Circ1365.pdf
[3] Ayres, R. U., 2007. On the practical limits to substitution. Ecological Economics, 61(1), 115-128.
[4] Tsoutsos, T., Frantzeskaki, N., & Gekas, V., 2005. Environmental impacts from the solar energy technologies. Energy Policy33(3), 289-296.

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