A simple bit of math shows that even with the rapid expansion that solar-energy and wind-energy capacity have had in the past few years, those two sources cannot even meet incremental global demand for electricity, much less make a dent in the world's overall demand for hydrocarbons. Between 1985 and 2011, global electricity generation increased by about 450 terawatt-hours per year. That's the equivalent of adding about one Brazil (which used 485 terawatt-hours of electricity in 2010) to the electricity sector every year. And the International Energy Agency expects global electricity use to continue growing by about one Brazil per year through 2035.
How much solar capacity would be needed to produce 450 terawatt-hours? Well, Germany has more installed solar-energy capacity than any other country, with some 25,000 megawatts of installed photovoltaic panels. In 2011, those panels produced 18 terawatt-hours of electricity. Thus, just to keep pace with the growth in global electricity demand, the world would have to install about 25 times as much photovoltaic capacity as Germany's total installed base, and it would have to do so again every year.
The scale problem is equally obvious when it comes to wind.
The power density of wind energy is roughly two watts per square meter, or about five megawatts per square mile. That means that by the end of 2011, the U.S. had covered a land area of about 9,400 square miles, just slightly smaller than the state of Maryland, with wind turbines. Therefore, to keep up with the growth in global electricity demand by using wind energy alone, the global wind industry will need to cover a land area of some 35,000 square miles - about the size of Indiana - with wind turbines. And it will have to do so every year from now through 2035.
That metric's still hard to grasp, so let me put it another way: In order to merely keep up with the growth of global electricity use, the wind industry would have to cover 96 square miles every day with wind turbines. That's an area about the size of four Manhattans.
How much solar capacity would be needed to produce 450 terawatt-hours? Well, Germany has more installed solar-energy capacity than any other country, with some 25,000 megawatts of installed photovoltaic panels. In 2011, those panels produced 18 terawatt-hours of electricity. Thus, just to keep pace with the growth in global electricity demand, the world would have to install about 25 times as much photovoltaic capacity as Germany's total installed base, and it would have to do so again every year.
The scale problem is equally obvious when it comes to wind.
The power density of wind energy is roughly two watts per square meter, or about five megawatts per square mile. That means that by the end of 2011, the U.S. had covered a land area of about 9,400 square miles, just slightly smaller than the state of Maryland, with wind turbines. Therefore, to keep up with the growth in global electricity demand by using wind energy alone, the global wind industry will need to cover a land area of some 35,000 square miles - about the size of Indiana - with wind turbines. And it will have to do so every year from now through 2035.
That metric's still hard to grasp, so let me put it another way: In order to merely keep up with the growth of global electricity use, the wind industry would have to cover 96 square miles every day with wind turbines. That's an area about the size of four Manhattans.
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