Proponents have looked to solar power as a potential panacea to the world’s current and future energy needs, while critics note that solar power still provides less than 1% of the world’s electricity. While wind power has grown to scale much faster, conventional wind technology has much less capacity to scale than solar power, and the theoretical limits on solar power are significantly higher . When might solar power fulfill the hype and generate much of our electricity? Solar energy has grown at a rapid clip since its infancy in the 1970′s, from 0 to 20GW (nameplate capacity) in 2009. How much of worldwide electricity demand will solar be able to fulfill if it maintains this growth rate?
Total solar power capacity continues to grow at 20-25% per year, a rate of growth it has maintained for decades. It’s not surprising that solar photovoltaic technology is advancing rapidly, as it is a cousin of traditional semiconductor technology. For almost four decades semiconductor technology advanced according to Moore’s Law, with chips roughly doubling in transistor density (and speed) every 18 months. At a 20% annual rate of growth, installed solar capacity would rise from 21 GW in 2009 to almost 6000 GW by 2040. This install base could generate 12 trillion kilowatt-hours of electricity per year, or two-thirds of today’s worldwide electricity consumption . However, the EIA estimates that by 2040 worldwide electricity demand will hit 35 trillion kilowatt-hours!
Even assuming that solar energy installations grow at a 20% clip for three decades, the total install base will not be sufficient to meet world energy demands. Despite the industry’s rapid growth, replacing a hundred years of fossil-fuel based generation capacity by mid-century may be close to impossible. Nonetheless, if solar energy manages to scale on this trajectory, its contribution would still be enormous, and would likely bring total renewable generation to over 50% of all electricity.
Can it be done? Did anyone in the 1960′s believe that a 2010 phone would have more processing capacity than all the world’s computers combined?
 From Without The Hot Air – all wind power resources worldwide could supply a significant fraction of total power needs, while solar energy in the Sahara alone could theoretically supply all world energy needs.
 The EIA International Energy Outlook shows current worldwide electrical demand of roughly 18 trillion kilowatt-hours, with this figure growing to 35 trillion kWh by 2035.