It is well known that there is no such thing as a free lunch. However, it is somewhat less known that there is no such thing as free energy, either.
Despite all the hoopla about new renewable energy sources being “free” and “practically unlimited” in a sense that no one owns the Sun nor the wind, the fact remains that in order to harness these energies, we need an immense construction effort. This, unfortunately, is neither free nor unrestricted in the material sense. As the above graph taken from a recent
study commentary by Vidal, Goffé & Arndt in Nature Geoscience (2013) shows, projected renewable energy deployments would very soon outstrip the current global production of several key materials. By the author’s estimates, if we are to follow the lead of renewables only-advocates, renewable energy projects would consume the entire annual copper, concrete and steel production by 2035 at the latest, annihilate aluminum by around 2030, and gobble up all the glass before 2020.
Certainly, material efficiency can improve greatly, substitutes can be found, and production can be increased. Nevertheless, the scale of the challenge is nothing less than daunting: the authors also provide a handy overview of material requirements per installed capacity, from which I calculated a range of figures for energy production.
If we compare renewable energies to that other low-carbon alternative, nuclear power, per energy unit produced, wind and solar electricity production requires
- 16-148 times more concrete
- 57-661 times more steel
- 43-819 times more aluminum
- 16-2286 times more copper
- 4000-73600 times more glass.
(The figures assume a lifetime of 20-30 years for renewables and 60 years for nuclear, and the following capacity factors: wind 0.3, solar PV 0.15, CSP 0.4, nuclear 0.8.)
In a very real sense, these materials can be thought of as the “fuels” or “consumables” of renewables. Without doubt, many of these materials can be recycled to an extent, but the required volumes inevitably mean that any substantial increases in renewable energy generation require corresponding increases in virgin production. Furthermore, not everything can be or will be recovered, and in any case, building the infrastructure for renewable energy generation will sequester huge amounts of steel, aluminum and copper over the lifespan of the generators.
But wait! Aren’t I forgetting something, namely the fuel that nuclear fission uses, and the huge underground caverns required for the disposal of the waste? Indeed, so here’s the second graphic of the day: the rough estimate of mining requirements for various energy sources, per megawatt hour produced.
You may note that nuclear energy’s estimate – and that’s what these are, estimates – is dominated by uranium mining. I deliberately used the low-end value for uranium ore grade, and omitted both In-Situ Leaching and byproduct mining operations, which would decrease the mining requirement considerably. In fairness, I did the same for other materials, although some appreciable amounts of iron and copper are recovered from byproducts. I also omitted the high-end estimate for solar PV, because that would have messed up the graphic: the total runs to staggering 611 kg of mining operations per MWh produced.
The figure is likely to be biased in favor of renewables, as I’ve omitted rare earths from the discussion. As shown in e.g. Öhrlund (2011), rare earths (metals used in e.g. permanent magnets and in solar photovoltaic panels) may pose a bottleneck for renewable expansion. Mining these relatively rare (hence the name) elements is a messy business, which could very easily greatly increase the “materials backpack” renewable energies have to carry around. Furthermore, the figure does not account for backup power systems, grid expansion or energy storage – all of which are significant building projects that are especially important for renewable energy.
Vidal, O., Goffé, B., & Arndt, N. (2013). Metals for a low-carbon society. Nature Geoscience, 6(11), 894–896. doi:10.1038/ngeo1993
Vidal, O., & Arndt, N. (2013). Metals for a low-carbon society: Supplementary Information. Nature Geoscience, 6(11), 15–17. doi:10.1038/NGEO1993
Öhrlund, I. (2011). Future Metal Demand from Photovoltaic Cells and Wind Turbines – Investigating the Potential Risk of Disabling a Shift to Renewable Energy Systems. European Parliament, Science and Technology Options Assessment. Brussels.