By 2050 vast photovoltaic arrays in the Southwest would supply electricity instead of fossil-fueled power plants and would also power a widespread conversion to plug-in electric vehicles. Excess energy would be stored as compressed air in underground caverns. Large arrays that concentrate sunlight to heat water would also supply electricity. A new high-voltage, direct-current transmission backbone would carry power to regional markets nationwide. The technologies and factors critical to their success are summarized at the right, along with the extent to which the technologies must be deployed by 2050. The plan would substantially cut the country’s consumption of fossil fuels and its emission of greenhouse gases (below). We have assumed a 1 percent annual growth in net energy demand. And we have anticipated improvements in solar technologies forecasted only until 2020, with no further gains beyond that date.
—K.Z., J.M. and V.F.
| Technology | Critical Factor | 2007 | 2050 | Advances needed |
| Photovoltaics | Land area | 10 sq miles | 30,000 sq miles | Policies to develop large public land areas |
| Thin-film module efficiency | 10% | 14% | More transparent materials to improve light transmission; more densely doped layers to increase voltage; larger modules to reduce inactive area | |
| Installed cost | $4/W | $1.20/W | Improvements in module efficiency; gains from volume production | |
| Electricity price | 16¢/kWh | 5¢/kWh | Follows from lower installed cost | |
| Total capacity | 0.5 GW | 2,940 GW | National energy plan built around solar power | |
| Compressed-air energy storage (with photovoltaic electricity) | Volume | 0 | 535 billion cu ft | Coordination of site development with natural gas industry |
| Installed cost | $5.80/W | $3.90/W | Economies of scale; decreasing photovoltaic electricity prices | |
| Electricity price | 20¢/kWh | 9¢/kWh | Follows from lower installed cost | |
| Total capacity | 0.1 GW | 558 GW | National energy plan | |
| Concentrated solar power | Land area | 10 sq miles | 16,000 sq miles | Policies to develop large public land areas |
| Solar-to-electric efficiency | 13% | 17% | Fluids that transfer heat more effectively | |
| Installed cost | $5.30/W | $3.70/W | Single-tank thermal storage systems; economies of scale | |
| Electricity price | 18¢/kWh | 9¢/kWh | Follows from lower installed cost | |
| Total capacity | 0.5 GW | 558 GW | National energy plan | |
| DC transmission | Length | 500 miles | 100,000- 500,000 miles | New high-voltage DC grid from Southwest to rest of country |
