"If 2 percent of the continental United States were covered with photovoltaic systems with a net efficiency of 10 percent, we would be able to supply all the U.S. energy needs," said Bulovic, the KDD Associate Professor of Communications and Technology in MIT's Department of Electrical Engineering and Computer Science.Well, lets do my favorite thing and Run The Numbers!
Let us start off with the Knowns:
1) Insolation for the United States - Previously looked at this is 4 kWh/sq. meter/day which is 1, 460 kWh/sq. meter/year. This is on average, mind you.
2) Area of the Continental United States - To everyone who is wondering this *includes* Alaska- The Land Area is 9,158,960 sq. km or 3,536,294 sq. mi.
3) 1 sq. km = 1,000,000 sq. m.
4) Two percent of the land area of the Continental US is 183,179.2 sq. km round off to 183,180 sq. km.
5) Total insolation of this two percent solution: 1,460 kWh/sq. meter/year x 1,000,000 sq. meter/sq. km x 183,180 sq/km = 267,442,800,000,000 kWh/year or 2.67 E14 kWh/yr. This is actual energy delivered on average to this 2% of the US per year.
6) Net efficiency of the energy storage and distribution system is 10%... which is about the current best on low-end silica photovoltaics, so a slight improvement there and a complete superconductive system end to end would be 10% delivered. So net energy delivered is 2.67 E13 kWh/yr.
7) For fun, daily production is: 7.14 E11 kWh/day.
8) As previously looked at current energy delivery to gasoline powered motors is approximately 9.16 E11 kWh/year and this does take all of their inefficiencies into mind. Thus the daily use of energy by vehicles and other gasoline powered devices is: 2.509 E09 kWh/day. Now, assuming a vehicular system delivery system that delivers 90% of the stored electricity for actual vehicular use, this then adds a bit of overhead into the system, so this puts total need at 1.02 E12 kWh/year or 2.78 E09 kWh/day.
So far so good!
9) Total energy consumed by the United States, including all motor vehicles and all petroleum products and all of the fun stuff included in (8) above : 99.74 Quadrillion Btu. And the short scale quadrillion is 1 E15 (the numbers would get all out of whack with the UK Quadrillion). Thus, the amount is 9.974 E16 Btu/yr.
10 ) Convert Btu to kWh: 1 Btu = 0.000293071 kilowatt hour or 2.93 E-04
11) So Total Energy Consumed by the US per year in kWh: 2.92 E13 kWh/yr or 8.00 E10 kWh/day.
Ahh! In the same ballpark with some quibbles, here and there. I handed the 2% folks a bit more land, to be sure, but the rest is pretty cut and dried.
The large problem with this solution: such a small fraction of the industry actually produces photovoltaic cells that it could not ramp up at any decent rate to meet this need. A truly large scale production system that could augment itself quickly over time would be an ideal solution.
And the land mass of that 183,180 sq. km? Well from this 2000 statistical abstract we can find a few close to this in total land area:
North Dakota 178,647
South Dakota 196,540
So there you have the idea of the collected geographic size of such a thing. Luckily this can also be done with a shade-grown crop as not all photovoltaic cells use the entire spectrum and even with good spacing there is always a lot of reflected sunlight on the ground. Desert is good for this, too. And space, of course, is best.
If you had a research initiative that looked into using differing technologies and incentivizing them, you might actually be able to start working on this. Unfortunately there is no political will for this as it would require innovative thinking and new approaches to problems and that is NOT a hallmark of the two party system or, apparently, the Republic these days.