Scientific American published a grand plan for nationwide terrestrial solar power generation system in the January issue. Its highlights:

• A massive switch ... to solar power plants could supply 69 percent of the U.S.’s electricity ... by 2050.


• A vast area of photovoltaic cells [and solar concentrator power plants] would have to be erected in the Southwest.


• Excess daytime energy would be stored as compressed air in underground caverns to be tapped during nighttime hours....


• A new direct-current power transmission backbone would deliver solar electricity across the country.


• But $420 billion in subsidies from 2011 to 2050 would be required to fund the infrastructure and make it cost-competitive.

It's an ambitious plan that could sharply decelerate CO₂ emissions and increase the US output of "green" power. Heroic plans require heroic proof. A critical analysis follows.

Some high level critiques are the following:

• Shifting peak load from day-time to night-time would not occur until solar displaced all natural gas plants and other swing units--i.e., all of excess air-conditioner demand over night-time demand, and all of the additional day-time usage that would occur as the price between day-time and night-time power usage equilibrated. This obviates the need for any wind-storage of solar power until well later.


• Compressed-air energy storage will become less useful as the price gap between day and night power diminishes. This undermines the case for near-term night to day storatge and will only be economical under this plan for day-to-night storage after day-time power is sufficiently cheaper to support the capital outlay. (Ironically since the solar installation is of the hockey-stick variety, compressed air storage may become viable for night-to-day energy storage well before solar becomes a relevant portion of energy supply.)


• Current photovoltaic production is about 2 GW of which US installation is about 8%. The plan calls for 84 GW of US installation by 2020 which would require 45% increases in solar installation every year for 13 years. Capping the installation at 10 GW/year installed, the ramp up becomes 70% per year 2006-2014.


• These growth rates are implausible without a $2.80/watt subsidy taking the installed price of $4/w to $1.20/w which is equivalent to $0.05/kwh. That would mean $234 billion in subsidies just to get to 3% of needed installed capacity by 2050.


• Polysilicon shortages are holding back photovoltaic growth so in 2007 and 2008 a growth rate of 20% is more plausible. That would require doubling production every year from 2009-2014 to hit the installed base of 84 GW by 2020.


• 84 GW by 2020 would be just 16% of average load and with a peak watt of electricity generating only 6 or 7 hours per day in the Southwest, it would be about 5% of total electric power generated.


• For this 5% of energy generated, we would be subsidizing it over 200% of the value of the energy generated--that is for $0.06 of electricity, it would require $0.14 in subsidies.


• At the end of the period, there is no guarantee that prices will be low enough to compete with coal, natural gas, nuclear or wind.


• If solar becomes viable and can compete with other energy types and begins to displace other types of power, prices for those types of power will drop. The total cost of solar will have to beat the marginal cost of coal or nuclear to dismantle an existing plant.

Consider investing in terrestrial solar power for security reasons or as a contingency, but it's a lot of faith to get the case to work for half of daily electricity demand.