“6,000 Years of Solar” is a series about the history of solar energy technology drawn from John Perlin’s new book Let It Shine: The 6,000-Year Story of Solar Energy. The series profiles the fascinating people, from ancient Greece and China to late 19th century New York to today, who have made the present day solar revolution possible.
John Perlin is an analyst in the physics department of the University of California, Santa Barbara and is a former CEC Staffer. He oversees solar installations at the university, and he writes, speaks, and lectures about solar energy.
Six thousand years ago, Neolithic Chinese villagers had the sole opening of their homes face south. They did this to catch the rays of the low winter sun to help warm the indoors. The overhanging thatched roof kept the high summer sun off the houses throughout the day so those inside would stay cool.
BY JOHN PERLIN, AUTHOR
Two thousand years later, the Chinese began to formally study the movement of the sun throughout the year in relationship to the earth. Knowledge gained from these studies stimulated Chinese urban planners to construct the main streets of towns to run east-to-west to allow every house to look to the south in order to catch the winter sun for supplementary heating. Since then, most Chinese cities have followed such planning. The city of Peking, though relatively young, was laid out no differently than older Chinese cities built thousands of years before. “Its streets are all so straight, so long, so broad and well-proportioned,” an astonished Gabriel de Magalhaes, a Portuguese visitor to China during the seventeenth century, remarked, “that it is easy to see they were marked out with a line.”
Such rational planning simplified large-scale solar housing in urban settings. Every building on an east-west street would have its south exposure assured, leading Magalhaes to observe, “You shall rarely see a palace or any great person which does not face that point of the compass” Traditional Chinese architecture invariably had a courtyard directly south of the main rooms which opened onto it.
Energy efficiency measures also emerged. The kang – a heated bed – for example, consisted of a platform built of excellent thermal absorbing and radiating material. When cooking in the late afternoon, a flue captured the waste heat from the stove and conducted it to the kang, keeping the bed and those sleeping in it warm throughout the night.
As the importance of solar architecture grew, the southern aspect took on great stature in Chinese life. Ancient wisdom associated the south with fire and warmth, while the north came to be synonymous with winter and somberness — hence, with things cold and dark. Ritual also required the Emperor to face south whenever holding an audience. Sages explained the custom, pointing out, “The diagram of the south conveys the idea of brightness . . .” The Emperor facing south therefore shuns darkness and embraces enlightenment to govern. The Chinese to this day prefer a southern orientation for housing.
This post, summarizing Chapter 1 of the author’s Let It Shine: The 6,000-Year Story of Solar Energy, was published on November 29, 2013 on the Renewable Energy blog of Mother Earth News.