“Prediction,” goes an old Danish proverb, “is difficult, especially about the future.”

Most of us will recognise this laconic observation from our private life, and it also applies to predictions made regarding the development of renewable energy.

For decades, the World Energy Outlook report published annually by the International Energy Agency (IEA) has predicted how the contribution to electricity production would evolve for all major technologies. Fact-based energy policymaking needs solid references, and the annual report has served and serves as a key reference for both political and economic decisions of governments and stakeholders.

Yet, a review of the predictions made in the World Energy Outlook over the past 20 years makes for a sobering reminder of the proverbial statement. Projections for wind energy have been strongly underestimated, as if the IEA has been unable to grasp that renewable-energy technologies tend to grow exponentially. Some have suspected that an initial pro-fossil bias permeated the IEA for a long time.

The wind industry itself has not fared much better than the IEA with its own predictions. In 2015, a team led by Ryan Wiser at the Lawrence Berkeley National Laboratory in California conducted a global expert elicitation seeking to predict future wind energy cost reductions.

IEA World Energy Outlook forecasts for wind power capacity. Photo: IEA/Henrik Stiesdal

The predictions of more than 150 leading experts were way off the mark. Taking offshore wind as an example, the average cost of electricity from representative projects being built in the first five years of the 2020s is way below even the most optimistic experts’ predictions for 2050.

Fortunately, time has passed since these earlier predictions, the renewable energy industry has matured, we have the benefit of larger datasets, and we are now much better positioned to look into the future.

Turning first to the IEA, things have changed dramatically since 2015 when Fatih Birol took over the leadership of the organisation. It is now a leading and vocal proponent of climate change mitigation, and this his has never been clearer than in its new report, Net Zero by 2050 - A Roadmap for the Global Energy Sector.

Key observations of the Net Zero report include:

  • The energy sector is the source of around three-quarters of greenhouse gas emissions today and holds the key to averting the worst effects of climate change, perhaps the greatest challenge humankind has ever faced.
  • Reducing global carbon dioxide emissions to net zero by 2050 will serve to limit the long-term increase in average global temperatures to 1.5°C.
  • Net zero by 2050 hinges on an unprecedented clean technology push to 2030.
  • Most of the global reductions in CO2 emissions through 2030 come from technologies readily available today, particularly solar and wind. Annual additions must reach 630 GW of solar PV and 390 GW of wind by 2030, four-times the record levels set in 2020.
  • Two thirds of total energy supply in 2050 is from wind, solar, bioenergy, geothermal and hydro energy. Solar PV capacity increases 20-fold between now and 2050, and wind power 11-fold.
  • Net zero means a huge decline in the use of fossil fuels, and there is no need for investment in new supply.
  • With investment in clean energy and energy infrastructure more than tripling already by 2030, we will have significant economic benefits, putting global GDP 4% higher in 2030 than it would be based on current trends.

Turning next to the wind industry experts, Ryan Wiser and his partners have recently published in Nature Energy their findings from a new expert survey conducted in 2020, which differ radically from the 2015 study, and the fit to reality is very good.

Furthermore, the underlying cost assumptions of the IEA Net Zero Roadmap correspond well with the expert predictions reported by Berkeley, particularly when taking into account regional cost variations that are accounted for differently in the two reports.

All in all, we now have good consensus on the future cost trajectory of offshore wind, and this is likely to apply also for onshore wind and solar PV.

Latest offshore wind cost forecasts from the IEA and a group of wind experts. Photo: IEA/Henrik Stiesdal

What is more, the consensus is that even offshore wind, the most expensive of the three technologies driving the future energy system (offshore and onshore wind, and solar PV) is already at a cost level that is not going to place any significant burden on any society relying now on conventional energy sources. On the contrary, the job creation opportunities of offshore wind will create benefits in the transition, not burdens.

We have a tremendous climb ahead of us. To meet the 1.5℃ limit, the IEA suggests annual offshore capacity additions of 80GW by 2030. In 2020, we added 5GW.

We can only hope that governments across the world will stand by their words in accordance with the Paris Agreements, heed the advice of the IEA net zero report, take note of the overall cost advantages of renewables, and act accordingly.

Still the future does remain difficult to predict! Personally, I would love to see our industry do it once more, beating the cost predictions and further enhancing all the arguments for the rapid transition to a viable future.by reducing costs even further.

· Henrik Stiesdal is a pioneer of the modern wind industry with his late-1970s turbine designs accounting for a large percentage of today's onshore fleet and the entire offshore wind sector traceable to the first projet at sea, Vindeby, project Denmark, which he led. The former chief technology officer of Siemens Wind Power is now CEO of his eponymous company Stiesdal A/S, which is developing next-generation offshore wind substructures, thermal energy storage, electrolysers and carbon-negative aviation fuel