Resisting the Solar Impulse

If modern politics teaches us anything, it is that one needs to frame political debate around a “poster child” that illustrates the point to be made. In the case of solar energy as a serious alternative to more dense energy sources – such as oil, coal, natural gas, fission, or fusion – the poster child is the Solar Impulse, a sun- powered airplane prototype.

In June, a Swiss team, headed by Bertrand Piccard announced the completion of the $98-million (USD) Solar Impulse airplane (left), which has a wingspan of a Boeing 747, weighs less than a small car, and powers itself through energy gathered by approximately 12,000 solar cells. The airplane has four engines, which develop 40 horsepower (viz., the power of the Wright Brothers’ original aircraft), allowing the craft to takeoff at 22 mph and cruise at a maximum speed of 44 mph. Its payload: two men in cramped quarters and a 400 kg (880 lb) lithium ion battery, which supplies power during periods of no sunlight. The goal: circumnavigation of the world in 2012 over a 25 day period. Oh, I forgot to mention that it cannot be flown in adverse weather: it is too delicate.

While the Solar Impulse is a technological novelty, it truly illustrates the practical limitations of solar energy. All one has to do is compare the Solar Impulse to planes that are conventionally powered and of similar wingspan … like the Boeing 747 to which its designers have compared it. According to the official Boeing website, the 747-200 (2 class-configuration)with a wingspan of 195 ft., 8 inches, carries 452 passengers, 6,190 cubic feet of cargo, with a maximum lift off weight of 833,000 pounds. It flies at Mach 0.84 (555 mph), with a range of 7,900 statute miles. For the math challenged, this performance would allow circumnavigation of the earth, by 452 passengers and 6,190 cubic feet of cargo in approximately 2 days.

So let’s bring this rainbow down to the ground: the sun’s energy – while it may be plentiful and even prove technologically feasible AND economical to accomplish some tasks – cannot provide a practical, continuous source of production grade energy for aviation or most other commercial purposes, which is the mother’s milk of an advanced, technological, competitive society.

To further illustrate my point, in May 2009, Obama promoted the government’s construction of a 140-acre solar array at Nellis Air Force Base, at a cost of $100M USD. The installed capacity is 14 megawatts of power or 30.1 gigawatt-hours of energy per year. Compare this to the three-unit Arizona Public Service Palo Verde nuclear plant built in the late 1970s, built at a cost of $5.6B USD (in 1970s dollars). In 2007, the three Palo Verde units produced 26,782 gigawatt-hours of electricity. Correcting the construction cost of the reactors for inflation, each reactor unit costs approximately $4.35B in 2009 dollars or 41 times the cost of the solar array but produces 297 times more electricity, while occupying far less land. An equivalent Nellis Air Force Base solar array would require approximately 125,000 acres. Considering the nuclear plants have a projected operating lifetime of 50 years versus 30 for the solar array and the fact that nuclear plant design is cheaper by half to build today than it was thirty years ago, the life cycle cost of the solar alternative is about 15 times more expensive than the nuclear one.

According to Access to Energy, (October 2008, Vol. 36, No.3), “[i]f one ten-reactor Palo Verde nuclear plant were built in each of the 50 states, the United States could be a net exporter of $200 billion per year of energy rather than a net importer of $300 billion per year." While some might say this is electric energy and our dependence is principally on oil and therefore an unfair comparison, cheap nuclear electric energy (estimated at 1.6 cents per kilowatt – hour) can be used to directly power vehicles as well as transform carbon-based fuels such as oil shale, tars, coal, and methane calthrates, into fossil fuel. This would require an investment of approximately $2T USD, which would produce jobs, prosperity, and energy independence. Instead, our government is planning to spend $2T in stimulus, TARP, and social program deficit spending and proposes to transition our country to a energy infrastructure that, at best, might support the Gross Domestic Product of a third world country.

My advice to Obama: resist the Solar Impulse and place your bet on proven technology. Unfortunately, in the end , I do not believe the president or many on the left will take my advice. “Political” science always overshadows engineering science.