The Wind, The Sun and The Nuclear – Part 3

In Part 1 we evaluated three quite different, ultra-low emmission power generating technologies that are more or less feasible in South Australia based on their expected overall performance: an ideally-located windfarm; treatment pond-cooled, efficient solar photovoltaics (PV); and the commercially-offered fuel-recycling PRISM small modular nuclear reactor.

Image credits: windturbines.com, adelaidenow.com, midweststudios.com

In Part 2, it became apparent that the relative popularity of each technology, and the notable and concerning reluctance of women to support modern, safe nuclear designs reflects a failure to communicate accessible, accurate and pertinent knowledge to the folks who are going to need it in the future. Energy can be a dense subject but comprehension beyond cents per kilowatt hour (kWh) or choosing solar instead of fossil fuels becomes necessary as we get involved in deciding how to clean up our supply while providing at least as much access and opportunity for our children as we have enjoyed.

As such, in this final part – more of an appendix – we can highlight a few more unnavoidable consequences of needing all this energy, and the technology mix we support for providing it. We’ll just worry about electricity, which meets a substantial proportion, though not all, of what we require in our day-to-day lives. And we’ll bear the challenge of future climate disruption – which must be met with ample sources of energy and the resilience they confer – firmly in mind as something we should not leave to our children to address.

The technology, the machinery, needed to convert our preferred energy source into electricity, needs to be built out of materials. This has never been more clearly illustrated than in this 2013 Scientific American article. This is the graphic:

The article mentions “hidden costs”, but it’s usually more that the costs are overlooked. Yet it is intuitive that the sophisticated and highly purified electronics underlying solar PV technology would charge a price in metals required, such that the massive circle for silver – plus those for aluminium, tin, copper and zinc – do make a lot of sense. In case it’s not clear, the size is an indication of how much more metal will be demanded when we want a kilowatt hour just from solar instead of from the average global electricity mix.

What about silicon? Fortunately, the required quartz is effectively inexhaustible, though the energy-intensive refining is substantial.

On this basis, the sort of wind energy we’ve looked at might seem preferable, though as before it’s important not to forget the other characterisitics we’ve already considered: capacity factor, average availability to meet peak demand, and so on. Pursuing a reliable but ultimately decarbonised electricity supply isn’t necessarily the same thing as aiming to minimise the amount of materials used. However, it will have to be a consideration, as described in a 2013 commentary in Nature Geoscience.

The construction and operation of technologies that harness renewable
sources of energy will consume large quantities of raw materials. The growing demand for rare metals, including selenium and neodymium in photovoltaic panels and wind turbines, risks derailing the shift to renewable energy. However, wind turbines (and photovoltaic panels also require enormous amounts of common metals such as iron, copper and aluminium, as well as sand and industrial minerals to make concrete and glass, and hydrocarbon derivatives to create resins and plastics.

…Humanity faces a tremendous challenge to make more rational use of the Earth’s non-renewable raw materials. The energy transition to renewables can only work if all resources are managed simultaneously, as part of a global, integral whole. Designs of new products need to take into account the realities of mineral supply, with recycling of raw materials integrated at both the creation stage and at the end of a product’s life cycle. Research is crucially needed to anticipate the total material requirements and environmental impacts of any new technologies.

A case can be made for more metal production near centres of demand, similarly to the locavore movement that proposes looking closer to home for our food. It seems unreasonable to shun green beans grown in Kenya while using copper from the Congo.

The authors rightly stress the potential for recycling of materials, but do not ignore the energy requirements involved, nor the vital research and development still needed to make it at all realistic.

What they do not acknowledge is the role of nuclear energy, both as a potential supply for these future recycling requirements, and also as a partner to the renewable technologies that are demanding all of this refined material. Take another look at the SciAm graphic. The bubbles for nuclear are for conventional reactors, the ones which consume a few percent of the uranium fuel. Even at this efficiency they are brilliant for reliable and safe electricity supply. But we have been looking at a fast reactor which is designed to run on both spent nuclear fuel and the refined uranium left over from enrichment. It can recycle this fuel until virtually every kilowatt hour is extracted. Even with the steel, copper and everything else used to built it, what would its materials requirements look like?

It would have to be at least this good.

One other thing, and this ties in to the unavoidable mining and recycling which our Nature authors have warned us about. Technology wears out, and at some point must be decommisioned and replaced. This is a looming problem for conventional nuclear plants, recognised especially in countries like the UK where a large number of reactors are planned to help with replacement. But for much of the rest of the western world commitment to new nuclear is largely lacking. So what are the alternatives? Well, the same lifespan issue comes with solar and wind, only it’s even more limiting. The efficiency of PV panels is known to degrade at a fairly constant rate, such that we can’t expect more than 90% of a solar installation’s efficiency after 20 years, and possibly less. But as any rooftop system owner knows, it is the supporting hardware like the inverter that is expected to wear out first and require outright replacement.

The International Energy Agency highlighted data from their 2014 World Energy Outlook that considered what this means for wind.

Pay attention to both axes. By 2040, the global share of generation from wind is expected to be visibly levelling off at well below 10%. This isn’t because of lack of popularity, or capital-inflating heavy regulation as suffered by nuclear energy (which was still nearly 11% in 2012). It’s because wind turbines – necessarilly exposed to the weather to function – have an expected lifetime of twenty-five years. After some inescapable future point, at a respectable but still relatively low global penetration, countries can expect no better than to be, on average, building wind farms no faster than they’re tearing them down.

I don’t know anyone who likes the implications, but in my view our children will have enough to occupy their energies without being committed to “treading water” in the replacement of their sources of electricity. Maybe it won’t come to that, but it depends heavily on how informed we want to be now in the choices we make for their sakes. Yes, reactors too come up for renewal but their supreme energy density makes all the difference.

Nuclear energy is estimated to provide 1000 watts per square metre.

The issue is that there’s good reason to expect the shares of solar PV and wind to meet quite clear material limits, while the traditional limits on nuclear are at best arbitrary and at worst populist, but in either case may ultimately serve to restrict resilience for subsequent generations – unless ours stands up for the arithmetic.

 

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