Graphic of the Week: The hidden “fuels” of renewable energy

Image

Figure 2 from Vidal, Góffe & Arndt (2013:896) shows the demand of some raw materials based on WWF’s prediction for wind and solar energy production reaching 25 000 TWh by 2050. Open and closed symbols correspond to different volumes of raw material required to construct different types of photovoltaic panels.

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.

Calculated after Vidal & Arndt (2013b) and various sources for mining requirements. Uranium mining is assumed to take place at the poorest primarily uranium-producing mines (ore grade 0,1%); other materials are computed using average ore grades and average recycling levels (30% for steel, 10% for concrete, 22% for aluminum, 35% for copper).

Calculated after Vidal & Arndt (2013) and various sources for mining requirements. Uranium mining is assumed to take place at the poorest primarily uranium-producing mines (ore grade 0,1%); other materials are computed using average ore grades and average recycling levels (30% for steel, 10% for concrete, 22% for aluminum, 35% for copper). Geological repository mining requirements are estimated according to Posiva reports.

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.

References

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.

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About J. M. Korhonen

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This entry was posted in Energy, Economy and the Environment, Infographics, Scarcities and constraints and tagged , , , , . Bookmark the permalink.

11 Responses to Graphic of the Week: The hidden “fuels” of renewable energy

  1. Cold Air says:

    Reblogged this on Cold Air and commented:
    An important reminder “renewables” refer to the energy source being converted to electicity, and not the materials required to build the machines needed to do the conversion.

  2. Hannes Tuohiniitty says:

    There are major flaws on the graph. The amount of concrete assumed for PV is ridiculous. The overwhelming majority of PV are assembled to roof tops of existing buildings. Those figures only could apply to PV-farms on ground.

    And where is the vast amount of concrete and steel used for building nuclear plants?

    Actually PV is doing well on that respect if looking at here: http://thebreakthrough.org/index.php/programs/energy-and-climate/nuclear-has-one-of-the-smallest-footprints/ as you have obviously done already.

    • Concrete and steel for nuclear power are included; it’s just that per MWh, they’re so small that they’re not visible in the graph. (Concrete use per MWh is approximately 0,46 kg, steel use is approximately 0,04 kg. 1 kg of steel requires approximately 4,2 kg of iron ore and coal, assuming that 30% of material is recycled.)

      Rooftop solar would indeed require less concrete, but rooftops are a scarce resource, if the goal is to produce more than marginal amounts of energy from solar.

      • Susi Lehtola says:

        Yes, what you need to realize is that while a nuclear power plant does require a pretty large amount of concrete in a single place, the thing is that for renewables (wind & photovoltaic) the sheer amount of modules that need to be installed to generate the equivalent of one nuclear reactor is HUGE (e.g. ~3000 wind turbines@2MW to create the equivalent amount of electricity as Olkiluoto III will produce.)… but this will be scattered pretty much all over, so you probably don’t realize it first.

  3. Nevertheless, it’s instructive to redo the calculations using higher recycling percentages and postulating that solar PV does not need any concrete at all. At the same time, we can extrapolate some trends of nuclear power, include CSP, and add coal as a comparison and as the principal enemy that, I feel, everyone interested in the environment or human prosperity should unite against.

    Assuming 95% recycling rate for all materials (which, in my view, is highly optimistic) and assuming increase of uranium production as a byproduct and from in-situ leaching, as well as reduced demands due to increase in fast reactors, the numbers look as follows (in kg/MWh for selected materials and omitting infrastructure requirements):

    Hydro 1.1
    Wind 1.5
    PV high 44.6
    PV low 4.5
    CSP 3.2
    Coal 350.2
    Nuclear (EPR) 1.2

    Then, assuming 95% recycling rate for everything except concrete, which is assumed to be recycled at current average of 10%. Further, assuming that concrete foundations for wind power are reused thrice, and that solar PV does not require any concrete at all:

    Hydro 19.2
    Wind 3.8
    PV high 40.4
    PV low 2.8
    CSP 16
    Coal 351.2
    Nuclear (EPR) 1.7

    For nuclear, any one of the following developments already underway, or a modest combination of these, can potentially reduce uranium mining requirements to the levels in these calculations:

    - Increasing uranium recovery as a by-product
    - Increasing in-situ leaching at the expense of open cast mining
    - Increasing the % of fast spectrum reactors

    The cutoff ore grade, where the uranium mining requirement is less significant than geological depository requirement (currently ca. 1.1 kg/MWh) is about 1.5-2%. Even at the ore grades more typical at dedicated uranium mines (often around 0.7% U), the total kg/MWh value for EPR-type nuclear power falls to around 4.3.

    For fast reactors, concrete and steel use per MWh will probably be somewhat lower, and both uranium mining and final disposal requirements will fall at least 90%.

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