We are faced with a range of choices when it comes to energy technology. One basic one is between renewables and nuclear. On that, here’s is nice perspective that I came across recently. Photoelectric interactions occur trillions of times for each silicon atom over a PV cell’s lifetime. By comparison, with nuclear, there is just a one-off fission of each U-235 or Pu-238 atom. Bang and it’s done, some heat and radiation out and the fission fragments are just left as active waste. That’s a primary reason why solar PV energy is better than nuclear energy, cheaper and safer, as also are the other renewables.
Here’s another nice bit of high level thinking about what sort of energy to use from Amory Lovins, in relation to fossil fuels. He talks of ‘replacing fiery molecules with obedient electrons’. It can be argued that we should always go for using the simplest energy source and carrier, which, in atomic terms, is the electron, or failing that, hydrogen (one proton, one electron), and we should avoid messing with complex molecules- hydrocarbons. Especially we should not be burning them, whether they are old fossil-derived, or derived from live biomass. Indeed, it may be that we should not be burning anything - we should be aiming for gentler, lower impact, direct conversion processes, and, as energy guru Walt Patterson has been arguing, move from fire to electricity.
However, while we are now looking to electrification of many end uses and to hydrogen for some others, there is also the more constraining strategic picture. Some say that renewables, of whatever sort and however used, cannot expand fast enough to see off fossil fuel: mitigation of climate effects by avoiding carbon dioxide production via the use renewables and by avoiding energy waste, will not be enough. Some say that greenhouse gas removal (GGR) and solar radiation management (SRM), so-called geoengineering options, are also likely to play interim roles. In a review, Prof. Ben Sovaccol says ‘the socially optimal level of geoengineering is dynamic—a constantly moving target—and will perpetually change based on active levels of mitigation, investments in adaptation, and even the deployment of other GGR or SRM options’. So they will all be jostling for a share, with some conflicting with each other, and also with renewables, but some possibly being mutually supportive- a view I explored in a post (and book chapter) a while ago.
It maybe that some GGR and SRM options will find roles. For example, painting roof surfaces bright white to reduced solar heat absorption makes sense in some areas, and CCUS may be the best option for some hard to decarbonise industrial processes, assuming they can’t be revamped. However, given the cost and eco-problems with most GGD and SRM, it would seem best to push instead for renewables and energy saving as the priority options. We can offset some CO2 by growing more trees, although they can’t store CO2 for ever, and there is not enough room for that, or BECCS, to help much. Indeed there may be fundamental limits to what can be done this way. There are also limits on how much suitable geological space is available to store captured CO2 underground in the hope that it will stay put for ever and allow us to burn yet more fossil fuel. That’s also a problem for Direct Air Capture (DAC). It doesn’t use much land, but it does need CO2 storage space- and it is also an energy intensive system. Renewable power could be used to run the DAC systems, but wouldn’t it be better to use that power direct to replace carbon emitting generation? Unless you are keen on nuclear powered DAC!
All in all, with the technology far from proven and the cost looking likely to be very high, the carbon capture based net zero carbon model based on compensating for emissions by post- combustion carbon removal, seems to fatally flawed as a viable long-term approach. And so too is most SRM- a series of short-term technical fixes with uncertain long term implications. In any case, surely we shouldn’t be trying to block out sunlight with aerosol particles, orbital sun shades or whatever- instead we need to use the sunlight.
Of course that still means we have to decide which renewables to use and at what scale. Large scale hydro seems an unlikely choice, given it eco-impacts, although it offers good pumped storage grid balancing potential, unlike small less environmentally invasive run-of-river hydro schemes. Biomass can be used at a variety of scales, and is storable, but in some cases its production can lead to significant land-use conflicts. So in some cases can the use of wind energy, unless it is from units sited offshore. Wave and tidal stream systems may avoid land use problems, and can offer power cycled differently to that from wind, so helping with grid balancing, but the resources are usually sited in locations remote from large energy demand. That means long expensive grid links.
Though there may be answers to some of these impact and operational problems, environmental impacts may increase as we move up-scale with offshore wind and other marine renewables. Welcome to the modern energy world of difficult choices and trade-offs on the supply side, and also on the demand side, with energy efficiency measures, though mostly very desirable, not always delivering what was expected!
A newly emerging bottom line issue is the environmental and resource costs set against carbon emission reduction potentials. Most renewable energy technologies (biomass apart) have zero direct carbon emissions and low embedded carbon debts, but some do use scarce materials, including rare earths, and that may well become a key issue in future. To some extent though, dealing with mineral scarcity is just a technical and economic issue - as prices rise, substitutes may be found and recycling will become cleverer and more attractive. But there can also be environmental issues adding further pressure and limiting growth - some mineral extraction activities are very ecologically invasive, polluting and hazardous to health. It’s another constraint on the development of renewables. It’s also of course an issue for nuclear. Uranium reserves are not infinite, but the IEA says nuclear needs fewer other minerals (apart from chromium) than renewables. That’s a bit surprising- certainly some see its exotic mineral requirements (hafnium, beryllium zirconium, niobium) being one reason why its growth may be limited.
For the moment though, the main materials issue in the energy area seems to be lithium for EV batteries, although the IEA suggests that mineral use will become an increasing issue for renewables. For example, it claims that ‘an offshore wind plant requires thirteen times more mineral resources than a similarly sized gas-fired power plant’. However, in such statements we have to wary of lumping together minerals of very different kinds and scarcity. In the case of offshore wind, the main issues in mineral kg/kW energy terms seem to be for copper and zinc- not rare earths. Even so material availability and extraction problems may be an important issue for renewable expansion- they are another constraint. That may be true even in the case of PV solar- although there is plenty of sand to make silicon, some other types of cell use scarce elements. You can’t get something for nothing and materials issues and extractivation problems have to be faced.
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