Engines of Our Ingenuity

No. 402:
SOLAR ENERGY

by John H. Lienhard

Click here for audio of Episode 402.

Today, let us find a place for the heat of the sun. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

"Fear no more the heat of the sun; nor the furious winter's rages," said William Shakespeare. In fact, our bodies are very closely matched to the heat of the sun and to the cold of its absence. Sunshine pours just about as much energy upon us as we can bear. It can provide all the energy we really need. The heat of the sun has given us most of the energy we've ever used.

Yet we pay the sun very little heed when we want energy for everyday use. We exhaust the store of energy that the sun has heaped up for us. We burn our ancient coal, oil, and gas, while we overlook the direct use of the sun itself. We forget the 170 trillion kilowatts that steadily rain down upon us.

We forget a hundred ways we can lay our hands on that energy. Hydroelectric power is sun-driven. An engine can draw heat from the warm ocean surface and reject it to the cold ocean deeps. We can arrange for the sun to warm our homes directly. We can burn fast-growing plants for fuel. We can tap the energy of the wind and ocean waves. We can microwave energy down to earth from solar collectors in space. Photovoltaic cells can change the rays of the sun straight into electricity.

None of this is free. The capital costs of solar systems run high, even if the sun's rays do not. And solar systems can lay a heavy hand on the environment. The watershed behind a dam eats huge tracts of real estate. The dams that've collapsed have wrought as much havoc as the worst natural disasters.

But the real threat to our well-being isn't the dam or the nuclear reactor or the coal furnace. What threatens us are the terrible concentrations of energy in our power systems. To save ourselves, we must put our eggs in many small baskets. We must divide our attention. We must put a nuclear plant here, a dam there, and a windmill in our back yard.

That's hard thinking for us. We make heroes and villains of energy systems. We forget everything but the cheapest source at any moment. As prices change, so does our short attention span. We lurch from oil to coal to the sun to natural gas.

Right now oil is so cheap that we've put everything else out of our minds. We're apt to see solar energy as the posing of flower children. It is not. It is a rich gallery of possibilties and the least assailable long-term alternative.

Solar energy is no knight on a white horse. By itself, and on the same scale as our other power plants, it can be just as dangeous and expensive as they are. The sun belongs in a more diverse and sophisticated equation of energy use. The heat of the sun is subtle stuff, and it will serve subtle minds.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


J. H. Lienhard IV and J. H. Lienhard V, A Heat Transfer Textbook. 3rd ed., Cambridge, MA: Phlogiston Press, 2004, Click here for a free copy. Section 10.6.

Somerville, D. Whatever Happened to Solar Energy? American Scientist, Vol. 77, No. 4, 1989, pp. 328-329.

The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.


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