The following post from Skeptical Science is by Dana Nuccitelli.
We recently examined how Australia can meet 100% of its electricity needs from renewable sources by 2020. Here we will examine how that goal can be scaled up for the rest of the world.
Energy consulting firm Ecofys produced a report detailing how we can meet nearly 100% of global energy needs with renewable sources by 2050. Approximately half of the goal is met through increased energy efficiency to first reduce energy demands, and the other half is achieved by switching to renewable energy sources for electricity production (Figure 1, below).
Figure 1: Ecofys projected global energy consumption between 2000 and 2050.
To achieve the goal of 100% renewable energy production, Ecofys forsees that global energy demand in 2050 will be 15% lower than in 2005, despite a growing population and continued economic development in countries like India and China. In their scenario:
Industry uses more recycled and energy-efficient materials, buildings are constructed or upgraded to need minimal energy for heating and cooling, and there is a shift to more efficient forms of transport.As far as possible, we use electrical energy rather than solid and liquid fuels. Wind, solar, biomass and hydropower are the main sources of electricity, with solar and geothermal sources, as well as heat pumps providing a large share of heat for buildings and industry. Because supplies of wind and solar power vary, "smart" electricity grids have been developed to store and deliver
energy more efficiently. Bioenergy (liquid biofuels and solid biomass) is used as a last resort where other renewable energy sources are not viable.