Guest post: Roger Andrews

Renewable energy, particularly wind and solar, continues to set records for electicity generation and installed capacity in many parts of the world, and as shown in Figure 1 wind and solar growth in recent years has indeed been quite spectacular (the data used to construct this and following Figures are from the 2014 BP Statistical Review of World Energy):

Figure 1: Electricity Generated from Solar and Wind, 1965-2013

But Figure 1 doesn’t tell the whole story because solar and wind are only two of the four main sources of renewable energy. Adding the other two – biomass and hydro – puts the solar and wind contributions in better perspective (Figure 2). Electricity generated by renewables has increased by a factor of over five since 1965 but 70% of the increase has come from hydro. Wind contributed half of the remaining 30%, biomass, which in the BP data set includes geothermal and “other”, contributed 12% and solar brought up the rear with 3%.

Figure 2: Electricity Generated from All Renewables, 1965-2013

But while renewables generation has grown, so has electricity consumption, and when this is taken into account we find that increased contributions from solar, wind and biomass have been offset by the declining overall contribution from hydro to the point where the percentage of the world’s electricity supplied by renewables is only marginally higher now than it was in 1985 (BP doesn’t provide global electricity consumption data before 1985).

Figure 3: Percentage of Global Electricity Generated by Renewables, 1965-2013

And because electricity supplies only about 40% of world energy consumption the percentage of world energy consumption supplied by renewables is correspondingly lower. Electricity consumption, on the other hand, has grown faster than energy consumption, so renewables do supply a higher percentage of world energy consumption than they used to – up from 5.6% in 1965 to 8.9% in 2013, with increased “market penetration” by wind, biomass and solar responsible for most of the increase:

Figure 4: Percentage of Global Energy Generated by Renewables, 1965-2013

Figure 4 in fact provides a reasonably good perspective on the actual contribution of renewables to global energy supply since 1965. Expanding the Y-scale to 100%, however, gives a better perspective on the size of the contribution:

Figure 5: Percentage of Global Energy Generated by Renewables, 1965-2013

There’s also the question of where hydro fits in. Unlike solar, wind and biomass its market share hasn’t increased much since 1965 and isn’t thought likely to increase at all in the future (the IEA projects that hydro’s share of global electricity generation will in fact decrease from ~17% to ~14% by 2050). So while we can expect that hydro will continue to provide most of the energy generated by renewables for some time to come it isn’t likely to contribute to decarbonizing global energy generation any more than it already has. If decarbonization is to be achieved by expanding renewables the expansion will have to come in wind, solar and biomass. So let’s take hydro out and see how far growth in wind, solar and biomass has carried us along the decarbonization path so far:

Figure 6: Percentage of Global Energy Generated by Wind, Solar & Biomass, 1965-2013

Clearly they still have a long way to go.