Not Clearly Pro or Con to the question "Can Alternative Energy Effectively Replace Fossil Fuels?"
"In our plan, by 2050 photovoltaic technology would provide almost 3,000 gigawatts (GW), or billions of watts, of power. Some 30,000 square miles of photovoltaic arrays would have to be erected. Although this area may sound enormous, installations already in place indicate that the land required for each gigawatt-hour of solar energy produced in the Southwest is less than that needed for a coal-powered plant when factoring in land for coal mining."
Cowritten with Ken Zweibel and Vasilis Fthenakis, "A Solar Grand Plan," Scientific American, Dec. 2007