"This is the first time that the maximum growth rate in individual countries has been accurately measured, and it shows the enormous scale of the challenge of replacing traditional energy sources with renewables, as well as the need to explore diverse technologies and scenarios", says Jessica Jewell, Associate Professor in Energy Transitions at Chalmers University of Technology.
The Intergovernmental Panel on Climate Change (IPCC) has identified energy scenarios compatible with keeping global warming under 1.5°C or 2°C. Most of these scenarios envision very rapid growth of renewable electricity: on average about 1.4 per cent of total global electricity supply per year for both wind and solar power, and over 3 per cent in more ambitious solar power scenarios. But the researchers’ new findings show that achieving such rapid growth has so far only been possible for a few countries.
Measuring and predicting the growth of new technologies like renewable energy is difficult, as they do not grow linearly. Instead, the growth usually follows a so-called S-curve. This means that when production of wind or solar power begins in a country it first accelerates exponentially, then stabilizes to linear growth for a while, and in the end slows down as the market becomes saturated.
"Scholars typically assess technological growth by measuring how fast a given technology reaches market saturation. But for wind and solar power this method does not work, because we don’t know when and at what levels they will saturate. We came up with a new method: to use mathematical models to measure the slope of the S-curve, i.e. the maximum growth rate achieved at its steepest point. It is an entirely novel way to look at the growth of new technologies", says Jessica Jewell.
Analysis of 60 countries
The researchers use these mathematical models to estimate the maximum growth rates achieved in the 60 largest countries which together produce ca 95% of the world’s electricity. They show that the average rate of onshore wind power growth achieved at the steepest point of the S-curves is 0.8% (with half of the countries falling within the 0.6-1.1% range) of the total electricity supply per year. For solar power, these estimates are somewhat lower: 0.6% on average (range 0.4-0.9%).
Higher rates, comparable to those required in climate scenarios, are indeed sometimes achieved, but typically in smaller countries. For example, wind power in Ireland expanded at some 2.6% per year while solar power in Chile has grown at 1.8% per year. However, fast growth is much rarer in larger countries. Among larger countries, only Germany has so far been able to sustain growth of wind power comparable with median climate scenarios (above 1.5% per year).
"In other words, to stay on track for climate targets, the whole world should build wind power as fast as Germany has recently" says Aleh Cherp, a professor in Environmental Sciences and Policy at Central European University and Lund University.
(As a side-note, Sweden has been growing wind power (including offshore) at about 1.6% per year in the last decade but this is at the upper end of the growth we observed in other countries.)
Why late adopter grow equally slow
To investigate future prospects of renewables, the researchers have also compared their growth in the pioneering countries (mostly in the European Union and other high-income industrialised nations) and in the rest of the world, where solar and wind power were introduced later. The latter group includes most developing and emerging economies that would be responsible for the bulk of global energy use and thus need to deploy most of wind and solar power in the 21st century. It is hypothetically possible that these countries could skip the trial-and-error stage which slowed down the early adopters, and thus leapfrog to higher growth rates. Unfortunately, the researchers discover that this is not the case.
"There are usually reasons why they are late to enter the race. It can be because of vested interests, weaker institutions, and an investment environment that doesn’t support new technologies as well as from unsuitable geography. Those reasons have prevented renewable energy from taking off in the first place and make it especially difficult to replicate or exceed the growth rates achieved in leaders. Thus, we cannot automatically assume that the countries which introduce wind and solar power later would learn from prior experience and grow these technologies faster", says Cherp.
Challenges for policy makers
The study highlights several policy challenges. One is for high-income countries to avoid the slowdown of solar and wind expansion, recently observed in several places. Another is for major Asian economies such as India and China to increase the growth rates so that renewables start growing faster than electricity demand and eventually push out fossil fuels. This can be achieved by widening the cost gap between renewables and the fossils, which include subsidies, phasing out or taxing competing technologies and supporting grid integration.
"Finally, we should recognize that there may be natural limits to how fast wind and solar can be expanded and thus we should systematically investigate the feasibility of other climate solutions", says Cherp.
Text: Christian Löwhagen
Image credits: Main photo: Pixabay. Jessica Jewell: Udo Schlög. Aleh Cherp: Johan Persson.
The article National growth dynamics of wind and solar power compared to the growth required for global climate targets was published in the journal Nature Energy, written by Cherp, A., Vinichenko, V., Tosun, J., Gordon, J. & Jewell, J.. Nature Energy 6, 742–754 (2021).