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.
Doug
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!