Over the past couple of decades, the share of utilized renewable energy (ie. wind, solar, hydroelectric, geothermal) has been increasing worldwide. There are some places, like Iceland, that have either attained getting 100% of their energy from renewable sources or have come very close (Norway and Costa Rica). Are these 100% renewable economies possible on a more global scale? There is still at least some uncertainty in the scientific community. A recent article, though, addressed these uncertainties head-on, showing that they are already solvable with today's technology.
The first area of uncertainty addressed is the projection of future energy demands, and whether there is enough energy available from renewable sources to keep pace. A 2015 study illustrates just how vast the potential is for renewable energy. The first figure (provided) shows the 2015 world energy usage (orange circle on the left, 16 terawatts) dwarfed by the yearly supply of available solar energy (large yellow circle, 23,000 terawatts). Just from that comparison, renewables have an extraordinary amount of potential to keep pace with current energy demands, but what about the future? Some estimates put the increase in energy demand by 2050 at nearly double what it is now. Again, from the first figure, even if world energy consumption is doubled, it is still dwarfed by the combined renewable energy reserves, especially solar.
Cost is another issue to consider. According to the International Renewable Energy Agency, many utility-scale renewable sources are already comparable to fossil fuel sources in cost or even cheaper. In the second figure, the cost range of fossil fuels is the green-grey box at bottom, with the circles representing the cost of various renewable facilities. Furthermore, they project that as soon as 2020, all the renewable power generation technologies will fall within the cost range of fossil fuel sources. Thus, switching to an economy using a greater percentage of renewables for power generation not only brings environmental benefits, compared with burning fossil fuels, but is also projected to be cheaper than fossil fuels in the very near future.