We have attempted to estimate the contribution of photovoltaics to global energy production. Currently the installed base of photovoltaics worldwide has an output of about 5.0 gigawatts. Since the sun doesn’t shine 24 hours per day, the actual yield is probably about one-third that amount, call it 2.0 gigawatt-years in 2005. While this installed base is probably set to double every two years, and this amazing pace may be a conservative estimate, it is accurate to say photovoltaics do not currently contribute to global energy production in any meaningful way.
We are moving to an electricity future – and since 33 gigawatt-years equals one quadrillion BTUs, and since global energy production in 2005 was about 400 quadrillion BTUs, today we are only getting about one-6,000th, or 1.7 hundredths of one percent of our energy from photovoltaics.
What about wind power? According to the Global Wind Energy Council, the installed base of windmills in the world today have a cumulative output of 59.1 gigawatts. Since the wind doesn’t blow 24 hours per day, the actual yield, again, is probably a bit more than one-third that amount, call this 24 gigawatt-years in 2005.
So wind power is currently producing nearly 12 times more power than photovoltaics, which brings their share of global energy production up to a measurable but still paltry one-500th, or 20 hundredths of one percent.
Which of these eminently clean sources of energy are increasing faster? In 2005, 11.5 gigawatts of windmill generators were manufactured. In the same year, about 1.5 gigawatts of photovoltaics were manufactured. But the costs of windmills are not likely to drop in the future as much as photovoltaics. We predict that by 2010 global production of photovoltaics will outstrip that of windmills, and that will just be the start.
It is reasonable to assume wind power has the potential to increase output by an order of magnitude, to perhaps 1.0% of global energy production. This is based on the assumption that mega wind farms such as those just announced in the Thames Estuary, will continue to get built. Should decentralized, silent, ducted wind-generators be developed and widely adopted for use in commercial buildings and urban high-rises, perhaps wind energy could even reach 2.0% of total global energy production within a generation, perhaps much more. But there is an upper bound to how many places are truly suitable for windmills; there are problems with aesthetics; there are problems with birds; there aren’t windy regions everywhere; there are clean energy alternatives.
Because the price of photovoltaics continues to drop – thin film costs are already approaching the magic $1.00 per watt level – combined with lower maintenance costs compared to windmills, our money is on photovoltaics. There appears to be no limit to how much energy will eventually be produced by photovoltaics, and production of photovoltaics is poised to experience sustained exponential growth.