Speaking on behalf of a panel of experts convened by the National Association of Engineers to address the 14 “grand challenges of the 21st century,” Ray Kurzweil said solar power will scale up to produce all the energy needs of Earth’s people in 20 years.

Members of the panel are “confident that we are not that far away from a tipping point where energy from solar will be [economically] competitive with fossil fuels,” Kurzweil said, adding that it could happen within five years.