In the May 12, 2015 “G7 Hamburg Initiative for Sustainable Energy Security”, the energy ministers of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States, plus the European Commissioner for Climate Action and Energy, said this:
An increasing number of countries are following the path of a rapid expansion of renewable energy. There (are) a number of challenges as energy systems change and related greenhouse gas emissions are reduced, one of which is how to integrate growing shares of variable renewable energy into electricity systems.
The G7 energy ministers are correct in their assessment. Integrating growing shares of variable renewable energy into electricity systems is indeed a challenge – and so far one without a good solution.
A few quick facts before proceeding. In 2013 renewables supplied the world with 21.7% of its electricity, according to BP. Take out hydro and they supplied the world with only 5.3% of its electricity. Then take out “other” renewables such as biomass and geothermal and the percentage falls to 3.3%.
Why take out hydro and “others”? Because their growth potential is limited by resource availability – too few good hydro sites, too few high-temperature geothermal fields, not enough wood to make biomass pellets etc. – and for these reasons they may never make a significant contribution to future global energy needs. Their growth performance since 1997, the year the Kyoto Protocol set the renewables bandwagon rolling, has certainly been less than impressive, as illustrated in Figure 1. “Others” have gained market share, but at a painfully slow rate, and hydro has actually lost ground:
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