So you think that "tapping the sun" is all new these days? Well, think again. Some 2,500 years ago the ancient Greeks were facing a serious shortage of fuel. Simply, they were running out of wood.
Their response: to tap the natural energy of the sun.
Socrates was an early advocate of solar planning and the Greeks gradually opened their homes to the south. The extensive use of sundials had made every Greek aware of the path of the sun and its position in the sky according to the season.
A properly oriented home would let in the winter sunlight when low on the southern horizon during winter and exclude most of it during the torrid months of summer. So the Greeks planned their homes accordingly. The ancient city of Priene was even relocated in its entirety on the southern slopes of Mt. Mycale to take advantage of the sun. It was probably the world's first totally planned solar community.
A few hundred years later the Romans faced a similar energy crisis. Most of the indigenous wood had been stripped from the Italian Peninsula and Roman wood ships, like oil tankers today, brought the needed energy from North Africa and France, sailing 1,000 and more miles in the process.
So, like the Greeks before them, the Romans quickly discovered the sun. But they improved significantly on the Greek design, as Roman technology had by then developed glass. This glass (or in many cases thin translucent waters of mica) let in the sun's warmth while excluding the cold winds.
Greenhouses, not rediscovered in Europe until the 18th and 19th centuries, were commonplace fixtures for the Roman nobility. So valuable was the sun to the early Romans that laws were enacted which prohibited new construction form infringing on the sun rights of existing structures.
This pattern has been repeated through succeeding centuries. Whenever fuel shortages have threatened a society, it has responded by turning to solar power.
In virtually every instance, however, new sources of cheap fossil energy have been discovered, promoting a temporary energy binge. This, in turn, has largely erased from memory the solar advances of the past. So, with each occurring energy crisis, man has had to reinvent a solar technology that was perhaps widely appreciated by earlier generations.
In short, solar energy is far from the new, exotic energy source that many people consider it to be. The Romans even understood the value of thermal mass. They recommended that pits beneath the floor be filled with broken pottery and other wasted earthen ware. These absorbed the sun's heat during the day and fed it back to the home during the colder nights.
In the first century of the Christian era, Hero of Alexandria invented a syphon that transferred water from one vessel to another by using sun power alone; and medieval scientists distilled alcohol and manufactured perfume through the use of solar furnaces (concentrating mirrors).
Copper ore "could be melted in one second and lead in the blink of an eye" by burning devices developed in Europe in the 1700s, according to a research worker of the day.
In 1860 the French solar advocate, Augustin Mouchot, surprised his colleagues , then searching for a solar engine, when his research revealed that solar power had been so extensively practiced by previous generations. It was thought to be a new concept, just as many today are amazed that solar engines of the last century pumped irrigation water (the Meadi power plant in Egypt, opened in 1913, developed 55 hp. and pumped 6,000 gallons a minute), or that solar water heaters were commonplace, first in California and then in Florida, up to World War II. Moreover, they were as sophisticated as current models now returning to the American scene.
Ken Butti and John Perlin, California-based authors and solar researchers, were equally surprised at the depth of solar history and of the sophistication of solar applications far back in history.
"I knew some very sophisticated solar communities were built by the Pueblo Indian tribes of the American Southwest 800 years ago," Mr. Butti says, "but I never dreamed the art went back 2,500 years to Socrates and the ancient Greeks!"
Messrs. Butti and Perlin's interest in solar energy surfaced in the early 1970s. Initial research into older solar applications soon turned up far more depth to the subject than they had ever believed possible, and the search was on in earnest.
The result of all this effort is entitled, "A Golden Thread -- 2,500 YEars of Solar Architecture and Technology" (Cheshire Books and Van Nostrand Reinhold Company. $15.95).
In many respects the book mirrors today's societies as they turn, like the Greeks and the Romans before them, to solar applications in the face of diminishing and increasingly expensive conventional fuel.
Just a century ago the French led in the development of a solar engine, because coal-short France was falling rapidly behind Britain in the Industrial Revolution.
About the time Lever Brothers, the British soap company, built Port Sunlight, near Liverpool, for its workers. The community was laid out so that the sun could stream in and warn every home. Between the two world wars of this century several communities sprang up in continental Europe designed to take the most advantage of the sun.
Neubuhl, near Zurich, is one example. But it was in the US in the late 1930s that the term "solar home" was first coined. At the time several companies were marketing prefabricated homes that were heated substantially by the sun.
In 1932, a Chicago architect, George Fred Keck, visited one of his homes in the process of construction and found men behind large glass windows working in shirt sleeves despite bitter winter temperatures.
"It was below zero outside," Keck recalled. "There was no heat on, and the men were working with just their shirts on and were comfortable in the house -- it was the heat of the sun."
Amazed by the heat trapped by the sun, Keck began experimenting with passive solar designs. One of Keck's heat-trapping houses was called by a reporter "a solar home," and the term stuck.
Now, in the oil-expensive last quarter of the 20th century, builders are turning their homes to the sun again, just as the Greeks did 2,500 years ago.