The Solar Tomorrow
There is a certain danger in asking a science fiction writer to speculate on the scientific feasibility of a future technology. He might take you seriously and answer.
Here are my back of the envelope calculation, based on two assumptions:
- Today, most solar panels convert about ten percent of the available energy from sunlight. Some companies claim fifteen, but be that as it may.
- The USA uses about 4 petawatt-hours per year. This is 4000000000000000 Watts or 4*10^15
I note that in a previous comment, I said this was 4.03 terawatts, and I calculated a surface area the size of Texas would be needed. But when I looked it up just now, the sources I found said the year USA energy need was 4.03 petawatts, a thousandfold more.
I am not sure which is correct.
Let us assume the higher figure, because we are talking about the future use, which may be much higher than our present.
My math skills are the weakest of anyone I know, so I would be delighted to be shown where I have erred.
The solar panel equation is this:
Total Power Output = Total Area x Solar Irradiance x Conversion Efficiency
Solar Irradiance is measured by flux of radiant energy per unit area.
The measured Solar Irradiance for a surface perpendicular to the Sun’s rays at sea level on a clear day is about 1000 Watt/m^2 or (10^3) and the Conversion Efficiency is 10%.
Plugging these number in the above equation we get:
4*10^15 Watts = Total Area x 1000 Watts/m^2 x 0.18
or
Total Area = 4*10^12/0.18 = 22*10^12 m^2
This is equal in land area to the largest extent of the Roman Empire, or roughly the size of Australia. That means no roads, no chimney, no croplands, no open spaces: just a blank sheet of black glass from Persia of the Pillars of Hercules, from Ethiopia to Ultima Thule.
When you assume an earth that rotates since the slanting sun delivers less energy, and at nighttime, none at all, and once we factor in cloudy days, you might easily increase the needed surface areas by another order of magnitude: so now we are talking about somewhere between paving the entire surface area of a continent like Africa, and paving a surface area equal to a small planet like Pluto.
I am only listing the energy needs of the United States, not the rest of the world.
I leave it as an exercise to the reader to determine the environmental impact of a world with a continent -sized patch of mirrored glass coated its surface, and the change in the albedo on global warming.
Again, math is not my strong suit, so I welcome corrections to the glaring errors I no doubt made in my calculation.
About John C Wright
John C. Wright is a practicing philosopher, a retired attorney, newspaperman, and newspaper editor, and a published author of science fiction. Once a Houyhnhnm, he was expelled from the august ranks of purely rational beings when he fell in love; but retains an honorary title.
