Imagining the World’s Largest Solar Array to Power a Nation

What if the US were to commit itself, before this decade is out, to meeting its entire 3 terawatt power demand using only solar cells? Stanford University Professor Mark Jacobson advocates an “Apollo Program” for hydrogen production using wind-generated electricity. Professor Martin Hoffert of NYU has called for a state-funded Manhattan-Project-style approach to tackle the energy crisis. What would be the hallmarks of a solar power facility on the scale of the Manhattan Project or Apollo Program?

A reasonable approach would be to distribute PV arrays throughout the country, taking advantage of distributed energy topology. In addition to solar, we would certainly need to harness the broader mix of available renewable energy: wind, waves, geothermal, etc. Nonetheless, this is my fantasy; so, we are going to do it my way. Let’s assume that the US set aside a huge parcel of land devoted entirely to solar energy generation in much the same way as land is conserved for national parks.

This solar real estate would be located somewhere with a lot of sunlight, and it would be reasonably unpopulated so as not to encroach on cities; perhaps the Arizona or Nevada desert would suffice. Forget for a moment about the challenges of energy storage and distribution, and ignore complications associated with cloud cover, seasons, and all those pesky non-idealities plaguing solar energy generation. The sun never sets on my hypothetical mega solar array. And why not? This is my fantasy, after all.

Given many simplifications, I calculate that roughly 11,600 square miles (3×10¹⁰ m²) would require silicon paving to generate 3 peak terawatts. As a comparison, the state of Maryland is about 12,407 square miles. Created in 1980, Gates of the Arctic National Park in Alaska is about 13,238 square miles, demonstrating that the Federal Government has a recent precedent of setting aside enormous tracks of land for environmental preservation.

Given a solar cell thickness of about 1 micron, roughly 30,000 cubic meters of poly-silicon would be required to produce my hypothetical mega array. Despite the “silicon shortage” stunting growth of the solar industry, the current annual global production capacity of poly-silicon is 30,000 metric tons. If all that capacity were diverted to the mega array, it would take about two and a half years to produce the all required raw material. If we started today, the array could be on-line before New Year’s Eve 2009.

To compare my fantasy against reality, I located the world’s largest photovoltaic array. It is a project based in Beja, Portugal with a collection area of 250 hectares (0.965 square miles) and a peak output of 116 megawatts, less than 0.0039% of my increasingly-hypothetical mega solar array.

Oh well. As long as I am dreaming, I might as well dream big.