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Ancient History of Solar

The history of using the sun as a source of heat and energy probably dates back to the very dawn of humanity. Without knowing it, early humans relied on the sun for everything from plant growth to passive heating to light. Of course, the sun and moon have always been used to tell time for as long as knowing time was important. For thousands of years, the sun was the only real source of energy that humans had available. It is easy to see why so many cultures worshipped our nearest star.

Early Solar

The active exploitation of solar energy began as early as the 7th century BCE when glass that could magnify the sun’s rays was used to make fire. In essence, this was the first use of magnification to create fire from sunlight.

The Greeks

The Greeks had a profound understanding of the sun and were the first culture to knowingly use passive solar heating. Their homes were built with window openings facing south so as to take full advantage of both the heat and light provided by the sun, particularly in winter. Though they had no glass, the Greek’s form of passive solar heating was the beginning of more substantial endeavors.

It is thought that Greek use of solar energy was an effort to reduce their reliance on wood and other fuels. As their cities grew, nearby supplies of wood became less common and the price of wood increased dramatically. In an effort to conserve, the Greeks began to build their homes to maximize passive solar heating.

Their structures clearly indicate an understanding of solar heat. The awnings and roofs of their homes were built such that sun could not enter the windows in the summer, but could easily enter in the winter when it was lower to the horizon.

The use of solar by the Greeks included battle applications as well. Around 200 BCE, Archimedes used bronze shields to reflect and concentrate sunlight on Roman ships, thus setting them afire. Though this use of sunlight is legend, it has been demonstrated to be effective, with the Greek navy setting fire to a wooden boat 50 meters away.

The Romans

Like many other things that they borrowed from the Greeks, the Romans borrowed the concept of solar heating. However, they were able to take the concept one step further with the assistance of glass. Glass windows became a standard in Roman culture because they allowed sunlight to shine through and heat structures, but impeded the flow of heat back out. Thus, the effects of passive solar heating were magnified.

Passive solar heating was so important in Roman civilization that laws were passed to prevent the obstruction of another’s sunlight. These laws were outlined in Justinian Code and made it illegal in Rome to build a structure or plant a tree such that it blocked the sunlight that another person used.

The Romans even used glass enclosed greenhouses to grow crops and maintain exotic plants that they imported from around the world. This use of passive solar is still common today as many homes in the Northern Hemisphere are built so that the majority of their windows face south.

Early Settlers of North America

The use of solar for heating and light was not unique to Europe. Early settlers of North America, such as the Anasazi built their cliff-side homes so that they faced south. Not only that, they allowed for large rock overhangs above their homes. This clever trick meant that less sunlight reached the dwellings in the summer when the sun was almost directly overhead while more light entered during the winter when the sun was nearer to the horizon. The Anasazi had a very clear understanding of passive solar heating and cooling, employing techniques that are still commonly used in the planning and construction of solar homes today.
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