In 1977 I bought a 2,000
square foot uninsulated house in upstate New York which got me interested in
solar space heating. After the usual insulating and weather-stripping, I added
an attached greenhouse and built a window box solar space heater. These worked
well enough to make me want to explore further solar possibilities.
After reading everything I could on the subject, I decided to build a passive solar earth sheltered home in Tennessee. I researched the subject by reading magazines and books and visiting every solar building I could. The book that gave me the best perspective on the history of solar design and its uses was "A Golden Thread; 2,500 Years of Solar Architecture and Technology". I'd like to give you a summary of what I've learned.
Solar powered home and water heating technologies have been evolving for thousands of years. The effectiveness of many of even the oldest solar technologies, especially the simpler ones like passive solar architecture, have been adequate for centuries.
The steady evolution of solar architecture and technology has been periodically interrupted by the discovery of apparently plentiful and cheap fuels, such as new forests or deposits of coal, oil, natural gas and uranium. Successive civilizations have short-sightedly treated this energy capitol as income. This attitude persists today.
We speak of "producing" oil, as if it were made in a factory, but we don't produce oil; all we do is mine it and burn it up. Neglecting the interests of future generations who are not here to bid on this oil, we have been squandering, in the last few decades, an inheritance of hundreds of millions of years. Only recently have we begun to come full circle to the same realization that similar boom and bust cultures have reached before us: that we must turn back to the sun, and seek elegant ways to live within the renewable energy income that it bestows on us.
It is very important to appreciate the lessons of earlier cultures, lest we repeat their mistakes. From the wood-short Greeks and Romans onward, people became aware of the limits of their dwindling fuel resources. They then rediscovered much of the earlier knowledge of permanent, practical solar energy.
At several points in history-the latest being today-observers of the energy scene have bemoaned the absurdity of having to rediscover and reinvent what should have been practiced continuously. Today we stand precisely where
several earlier cultures have stood. We have suddenly learned the transitory nature, the vulnerability, and the high social, ecological, and even economic costs of depending on nonrenewable hydrocarbons to hold our society
together. But we still play elaborate games of self-deception by giving these precious fuels (and the electricity made from them) tax and price subsidies which in the US alone total roughly $100 billion a year. Although some available solar technologies are more expensive than oil and gas, almost all cost several times less than what we would have to pay to replace them with nuclear power or synthetic fuels.
Perhaps this is the last time the inevitable solar age will be temporarily forestalled by a false sense of abundance. For unless some new form of energy now wholly unknown is discovered soon, there are no long-term energy
alternatives other than nuclear reactions kindled artificially or the natural energy flows driven by nuclear fusion sited at the appropriate distance of 93 million miles. The Greeks ravaged forests for fuel and building materials 2,500 years ago. By the fifth century BC many parts of Greece were totally stripped of trees. This led to the earliest examples of solar architecture based on the changing seasonal position of the sun.
The Greeks knew that in winter, the sun travels in a low arc across the southern sky; in summer it passes high overhead. They built their homes so the winter sunlight could easily enter the house through a south facing portico, similar to a covered porch. Overhanging roofs and eaves shaded the house from the high summer sun.
Socrates said, "In houses that look toward the south, the sun penetrates the portico in winter, while in summer the path of the sun is right over our heads, and above the roof, so that there is shade."
The Greeks planned cities so that each house had good southern exposure. In the first century AD Romans had solar rights laws.
About 500 BC the great Greek playwright Aeschylus noted that a south facing orientation was a normal characteristic of Greek homes. It was a sign of a modern or civilized dwelling, he declared, as opposed to houses built by primitives and barbarians, who, "though they had eyes to see, they saw to no avail, they had ears, but they understood not. But like shapes and dreams, throughout their time, without purpose they wrought all things in confusion. They lacked knowledge of houses turned to face the sun, dwelling instead like ants in sunless caves." Sophisticated solar communities were built by the Pueblo Indian tribes of the American southwest. The Anasazi built sky city Acoma with full sun exposure. The use of solar heat in horticulture also has a long history dating back to early Rome, where the earliest glazing materials were thinly split stone, such as mica or selenite.
During the 1600s, the French and English developed a technique of constructing fruit walls, vertical or sloping masonry walls facing south or southeast, to which they attached the branches of fruit trees or grape vines. The walls absorbed solar heat, and would greatly lengthen the growing season, even allowing tender blossoms to survive a hard freeze.
Solar water heating has a shorter history, starting with bare metal tanks painted black and tilted to face the sun. An 1891 patent combined that technique with the solar hot box, increasing the tank's ability to collect and store heat. This was our nation's first commercial solar water heater, called The Climax.
Visible light makes up only 46 percent of the total energy emitted from the sun, while 49 percent is in the infrared band, which we experience as heat. The remaining portion is in the ultraviolet band. Earth intercepts only a tiny 2 billionths of the sun's total radiant output, but this is the equivalent of 35 thousand times the total energy used by all people.
Jan 4, 2008
If you have questions, you can reach Doug at:
dougkalmer AT gmail DOT com (replace AT with @, and DOT with a period)
Doug has contributed a number of projects to Build-It-Solar covering a wide range of solar and renewable energy areas -- see them all...
Thanks very much to Doug for providing this material!