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  • John A. Mathews and Carol X. Huang


In the vast world energy system, and in particular the world electric power system, it is critical in understanding the pace and direction of change to identify the key drivers. The system as a whole is slow-moving – the world is still burning a lot of coal for power, a lot of oil for transport, and a lot of gas for industrial processes. But if we look at the changes in the system year on year, and in particular at additions to electric generating capacity in the world electric power system, we can read trends that are having a profound impact on the future direction of the total system.

Recently published data from both the International Energy Agency (IEA) in the form of the Renewables 2018 report, and the International Renewable Energy Agency (IRENA) in its Renewable Capacity Statistics 2019 report, reveals how rapidly the world’s electric power system is greening.[1] The most recent IRENA report on renewable (electric power) capacity statistics, issued in April 2019, reveals that the world had built electric power grids generating power from renewable sources rated at 2.4 terawatts (TW) capacity by 2018 – that’s 2.4 trillion watts. So the world is already meeting the “terawatt challenge” posed by renewables.[2] Using the data on capacity additions to the global electric power sector provided by IRENA, we can update the chart published in this blog on Nov 15 2017, as shown in Fig. 1.[3]

Fig. 1 Global electricity capacity, 2001-2018

The chart reveals how the world’s electric power system has been growing steadily, to reach a capacity of 7,122 GW(7.1 TW) by 2018 . Within this total, the renewables capacity level has been growing exponentially at an average annual rate of 11.4% from 2001 to 2018-- faster than the system overall. But the most interesting feature is what is happening to the renewables’ capacity as a proportion of total capacity. The rising proportion of electric capacity sourced from WWS sources (water, wind and sun) which had reached 32% in our earlier blog, now reaches 33% by 2018. This proportion has risen from 23% in 2009 to 33% in 2018 – or a 10% increase in the proportion of WWS capacity in a decade. In absolute terms, WWS sources rose from 1,136GW in 2009 to 2,351GW in 2018. This is one important indicator of the greening trend in the world’s electric power system.

The IRENA report allows another approach to the issue of the greening of the world electric power system in terms of capacity additions year on year, from 2001 onwards. These data are shown in our new Fig. 2.

Fig. 2. Year on year addition of electrical capacity, greening vs blackening

This chart 2 shows how yearly additions of thermal sources generating capacity (burning mainly coal) exceeded yearly capacity addition from renewable (WWS) sources every year up until 2012, which was the turning point in greening for the world electric power system. After 2012 capacity additions from WWS sources each year exceeded additions from thermal sources (apart from the anomalous year 2014, when capacity additions from thermal and WWS sources were neck and neck). We follow IRENA in depicting a green line which shows the rising proportion of annual capacity additions from WWS sources, passing 50% in 2011/12 and reaching 63% by 2018. For good measure we add the corresponding proportion for additional capacity sourced from thermal sources (not shown by IRENA for unexplained reasons) in the black solid line, which is trending downwards and reaches 37% by 2018. This crossing of the lines depicting the proportion of power capacity based on green sources overtaking the line depicting proportion of capacity sourced from thermal sources, is the clearest possible indicator of the greening trend of the world’s power system.

If the proportion lines are extrapolated, we can see that the yearly additions from WWS sources will in all likelihood rise from the current 63% to more than 90% by perhaps 2040 while the additions of thermal sources will slow to zero and then to negative growth as coal-fired power stations are closed and not re-opened. This chart 2 reveals how the greening of the electric power system worldwide is actually accelerating, as the additional capacity added each year is sourced to a rising degree from WWS sources. This is one indication of the changing global electric power system, where the leading edge of the system (capacity additions year on year) is steadily getting greener rather than blacker.

We can go further to demonstrate that this greening tendency is accelerating. For some reason IRENA emphasizes how the blackening of the world power system has been waxing and waning, with average yearly increase of 115 GW and “no discernible trend upwards or downwards”. On the contrary we wish to point out that there are two clear trends evident in the chart, with thermal power capacity additions increasing each year up to 2014 and then decreasing each year beyond 2014.

When we plot the difference between the greening trendline and the blackening trendline, as we do in Fig. 3, we can see that the greening dominates the blackening, and the gap is increasing – indicating the extent to which the greening tendency is accelerating.

Fig. 3 Global: Greening vs blackening trends, 2001-2018

Source: Data from IRENA

Of course capacity additions are not the only way to describe greening/blackening trends in the global electric power system. When we look at actual levels of electricity generation, we find the same trends but with less emphasis than those found in the capacity changes. We depict the changes in global electricity generated in Fig. 4, building on Chart 2 as published in our blog of Nov 15 2017 and adding in the details for 2017 provided by the IEA. For reasons best known to the IEA, the clear statement and depiction of trends in electric power given in the Renewables 2017 report is not followed up in the Renewables 2018 report. What we can glean from the 2018 report is that the electricity generated globally from renewable sources reached just over 6000 TWh in 2017, which the IEA calculates as representing 25% of global electricity output in 2017. (Our earlier blog post is in accordance with this figure.) The IEA then make a prediction that electricity generated from renewable sources will rise to just over 8000 TWh in the five years to 2023, accounting for 30% of the electricity anticipated to be generated at that time.

It is odd how the IEA makes these 5-year projections the centrepiece of its analysis of renewable trends. Our preferred way of depicting the trends is to use actual historical data, which reveal that the proportion of electric power generated from renewable sources has risen from 20% in 2008 to 25% by 2017 – or a 5% increase (shift) in a decade. This is a solid shift in the past ten-year period – a better indication of the trend than the IEA projection forwards assuming a 5% shift over the next 5 years, from 2018 to 2023. World Energy Outlook 2018 predicts another 2% shift from 2023 to 2025, reaching a predicted 32% with the electric power generated from renewable sources advancing to a predicted 9,644TWh. As noted, the trends in actual power generated are not as spectacular as the trends in capacity added. The trends are shown in Fig. 4.

Fig. 4 Global electricity generation: greening trends

Can we make reliable predictions based on these greening vs blackening trends? Based on the capacity shifts, we can take the shift in the proportion of power capacity sourced from renewables as 10% over the past decade (from 23% in 2009 to 33% in 2018) and take that forward over the decade 2020 to 2030, by which time the world electric power system should have continued its greening to reach the point where it is almost as green as it is black. After that, the proportion of power sourced from thermal sources should be expected to fall rapidly, when the world moves to renewable power beyond a level of 50%, then 60% and 70% by perhaps the year 2040 and nearing 100% green power by 2050. By that time, transport and industry should also have become almost 100% electrified, and with this power being sourced from close to 100% green sources, the entire world energy system would be approaching a green rather than a black system. This is the optimistic view based on the historical analyses provided here, based in turn on a critical reading of the IEA and IRENA reports.

What is driving the world power system trends?

We need look no further than China to see what is driving these world power system trends. Updating the charts for China electric power trends carried earlier in this blog, we show in Fig. 5 how China’s greening of its power system is the dominant tendency in driving the world trends. Chart 5 shows the changing proportion of electric power capacity sourced from WWS sources in China, from 2001 to 2018.

Fig. 5. CHINA: Change in proportion of electric power capacity sourced from WWS, 2001 to 2018

Fig. 6 CHINA: Change in proportion of electric power generated sourced from WWS, 2001 to 2018

Figures 5 and 6 reveal that China has effected a green shift in its electric power sector over the past decade that is of precisely the same form as the trends visible at a global level. In terms of generating capacity changes shown in Fig. 5, China’s capacity sourced from WWS sources rose from 20% in 2007 to 37% in 2018 – or a 17% increase in WWS capacity achieved in just a decade. In terms of electricity generated (Fig. 6) power generated from WWS sources rose from 15% of total power in 2007 to 25% in 2018 – or a 10% green shift in the past decade. The similarity of the charts for the world and for China provide the demonstration that China is driving the changes at a global level.

Indeed China is now the undisputed world super power in renewable energy. This can be demonstrated in terms of power generated, or investment, or manufacturing prowess. In this post we show China’s renewables dominance in terms of WWS capacity in Figure 7, sourced from the recent IRENA Renewables Capacity 2019 report. Of the world renewables capacity total of 2.4 trillion watts, China by 2018 had built 696 GW, followed by the US at 245 GW, Brazil at 136 GW, Germany at 120 GW and India at 118 GW. It is notable that China’s renewables capacity by 2018 had surpassed the total of the next four countries combined.

Fig 7. Generating capacity from WWS sources: China compared with other countries

Source: Data utilized from IRENA 2019, Table 1


IEA 2018. Renewables 2018. Paris: International Energy Agency, available at:

IRENA 2019. Renewable Capacity Statistics 2019. Abu Dhabi, UAE, available at:

Smalley, R.E. 2005.Future global energy prosperity: The Terawatt challenge, MRS Bulletin, 30 (6): 412-417.

[1] The IRENA report Renewable Capacity Statistics 2018 can be found here:

The IEA report Renewables 2018 can be found here (behind a paywall):

[2] The “terawatt challenge” is the phrase used by Nobel laureate Richard Smalley in his overview of the world energy system published in 2005 (Smalley 2005).

[3] Our blog post ‘Global green shift in the electric power sector: IEA data’, Nov 15 2017, can be found here:

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