Renewable energy commercialization:

According to a 2011 projection by the International Energy Agency, solar power plants may produce most of the world's electricity within 50 years, significantly reducing the emissions of greenhouse gases that harm the environment. The IEA has said: "Photovoltaic and solar-thermal plants may meet most of the world's demand for electricity by 2060 – and half of all energy needs – with wind, hydropower and biomass plants supplying much of the remaining generation". "Photovoltaic and concentrated solar power together can become the major source of electricity".

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Photovoltaic and solar-thermal plants will never meet most of the world's demand for electricity by what year?
unanswerable