In recent years, there has been more and more talk of a transition to renewable energy on the grounds of climate change, and an increasing range of public policies designed to move in this direction. Not only do advocates envisage, and suggest to custodians of the public purse, a future of 100% renewable energy, but they suggest that this can be achieved very rapidly, in perhaps a decade or two, if sufficient political will can be summoned. See for instance this 2009 Plan to Power 100 Percent of the Planet with Renewables:
A year ago former vice president Al Gore threw down a gauntlet: to repower America with 100 percent carbon-free electricity within 10 years. As the two of us started to evaluate the feasibility of such a change, we took on an even larger challenge: to determine how 100 percent of the world’s energy, for all purposes, could be supplied by wind, water and solar resources, by as early as 2030.
• Solar power. While sunlight is renewable -- for at least another four billion years -- photovoltaic panels are not. Nor is desert groundwater, used in steam turbines at some solar-thermal installations. Even after being redesigned to use air-cooled condensers that will reduce its water consumption by 90 percent, California's Blythe Solar Power Project, which will be the world's largest when it opens in 2013, will require an estimated 600 acre-feet of groundwater annually for washing mirrors, replenishing feedwater, and cooling auxiliary equipment.
• Geothermal power. These projects also depend on groundwater -- replenished by rain, yes, but not as quickly as it boils off in turbines. At the world's largest geothermal power plant, the Geysers in California, for example, production peaked in the late 1980s and then the project literally began running out of steam.
• Wind power. According to the American Wind Energy Association, the 5,700 turbines installed in the United States in 2009 required approximately 36,000 miles of steel rebar and 1.7 million cubic yards of concrete (enough to pave a four-foot-wide, 7,630-mile-long sidewalk).