A model that estimated the plateauing of nuclear and hydropower to within 20 percent of reality suggests that absent a technological breakthrough, the growth of new renewable energy – that is, wind and solar – will saturate and end when these new power sources, taken together, amount to no more than about ten percent of the world’s energy supply. This is the startling and fearsome conclusion of recent study by Hansen et al. (2016).

I previously wrote in length about that nemesis of optimistic prognosticators, the technology S-curve, and noted that there are no reasons to believe renewable energy revolution won’t be subject to the same forces that so far have stalled every previous energy revolution before they’ve been complete. In that article, I showed how the still unmatched initial growth spurt of nuclear power convinced many reasonable observers up until late 1970s that the age of cheap atomic energy was inevitable and that other energy sources would soon simply vanish before this juggernaut of unlimited power and potential. The similarities to today’s discussion and hype about the potential of renewable energy sources, largely based on their relatively rapid initial growth rates, are direct and worrisome: the nuclear revolution entered the steady phase of the S-curve and stalled long before being complete, and there are many signs the renewable revolution is in danger of stalling.

Now, Hansen et al. provide some further evidence for my claims. They used a simple logistic model (“S-curve”) to estimate the final plateau of various energy sources, including hydropower in Europe and nuclear power globally. Using data from the growth years of these power sources, they found that the logistic model predicted the ultimate extent of both nuclear and hydropower generation to within 20 percent of reality. Then, using the same model with similar data about the recent growth of renewable energy, and factoring in optimistic estimates until 2020, they concluded that the similar flattening in growth rates would occur with renewables by about 2030, resulting to global power generation of about 1.8 terawatts (TW) at most.

Because global energy use exceeds 17 TW at the moment and is projected to increase until 2050 at least, this presents a very stark warning to everyone interested in stopping dangerous climate change and weaning the world from the scourge of fossil fuels. The idea that we can stop dangerous climate change, and particularly the idea that we only need renewable energy and energy efficiency to do so, are almost entirely predicated on the assumption that renewable energy growth will be exponential rather than logistic, and/or that the plateau of slow growth will take decades to achieve. However, every technology has followed the logistic S-curve in the past, and Hansen et al. note that the observed data fits the logistic model better than it fits an exponential one.

This is potentially a very serious issue indeed.

Logistic fit for energy sources growth, from Hansen et al. (2016)

Hansen et al’s warning echoes what we’ve been saying for some time now: there is a troubling slowdown in new renewable energy installations in precisely those countries and regions that have been the most advanced in this respect. In other words, RE installations are slowing down in places that have installed the most RE – long before installation rates, let alone total capacities, that decarbonisation requires have been achieved. These slowdowns could be an early signal that renewable revolution is stalling, although it’s still too early to say for certain. However, renewable energy faces some unique challenges, the chief among them being probably the tendency of additional installations to cannibalise the revenue streams of all the similar generators after the penetration roughly equals the average capacity factor of the generators in question. (See this excellent treatise by Alex Trembath and Jesse Jenkins for more detail about this problem.)

Solar PV installation rates in forerunner Europe took a plunge after a peak in 2010, even though global installation rates increased. This could be a troubling signal. Figure from our book, Climate Gamble (see sidebar).

It’s still too early to say for certain whether Hansen et al. are right. I sincerely hope they’re wrong, and that renewable energy revolution continues as the optimists hope. This may well be possible, if – and that’s a major if – energy markets are restructured to truly value low-carbon energy, and price decreases for both renewable generators and storage systems continue unabated. Still, we’re likely to need more subsidies (implicit or explicit) for our energy systems, not less, and as the authors note, the trend is unfortunately towards phasing out the subsidies.

Despite fervently hoping that the authors are seriously in error, I cannot, in good conscience, ignore the extremely troubling similarities to previous hype cycles about energy revolutions, nor can I ignore the potential early warning signals that may indicate that renewable revolution isn’t going to be such a smooth sailing as its proponents still often claim it to be. We need more effort to promote clean energy, and more alternatives. Consider that even if Hansen et al’s prediction turns out to be wrong by a factor of 7, we’d still require more than just wind and solar power. Ignore warning signs such as this only at our peril.

As a bonus: my previous article about S-curves did not include data about the growth of new renewable energy sources, but thanks to a helpful table in the aforementioned study, here comes. It represents an estimate of total power generated by each source during the first 30 years of their expansion, i.e. installed power corrected by (estimated) capacity factor. The capacity factors used are as follows: hydro, 0.8; solar, 0.1; wind, 0.27; nuclear, 0.5 from 1965 to 1980, rising to 0.8 by 2015. You can access the data from this Google Sheet and view the interactive version of the graph below here. As you can see, the nuclear energy revolution is still unprecedented (and particularly so if we’d look at growth relative to existing generation), although wind power growth shows some signs of catching up.

Actual power generation (installed capacity * capacity factor) from different energy sources during up to 30 years of expansion. Data from Hansen et al. (2016), capacity factor estimates my own.

References

Hansen, J. P., Narbel, P. A., & Aksnes, D. L. (2016). Limits to growth in the renewable energy sector. Renewable and Sustainable Energy Reviews, 70 (October 2016), 769–774. https://doi.org/10.1016/j.rser.2016.11.257