Everyone’s got an origin story, and solar energy is no exception, but you might be surprised to learn just how far back this origin story goes.
Mankind has been using solar energy in one form or another for thousands of years. Even ancient civilizations were aware of the benefits of solar energy.
The earliest form of use mankind had for the energy coming from the Sun was in so-called solar architecture. For all its pomposity, the phrase simply means that people oriented their houses in such as way as to open to the south to gather the most heat from the Sun. The earliest evidence of this comes from 6,000 B.C. in China.
Other, later cultures also oriented their houses in a way that would help them utilize the Sun’s heat to warm the building. Solar architecture was popular in ancient Greece and in Rome, too. The Romans actually made one huge improvement to solar architecture: they discovered that glass and mica trapped the sun’s heat, and so they built their bathhouses with large windows to make the best of that heat-trapping effect of the only transparent materials they knew of at the time.
The power of mirrors
Again in China, three thousand years ago, people came up with a way to more than just heat their homes with the rays of the Sun. They made bronze mirrors and used them to capture sunrays and start fires with them. In modern times, many of us will remember experimenting with a magnifying glass to the same end.
The principle of action of the so-called burning mirrors was based on light reflection. The Chinese mirrors were in fact convex lenses, which concentrated sunlight in a point—usually in a pile of firewood—and this concentrated light eventually ignited the wood. Later, the Greeks and the Romans also discovered the power of mirrors independently of the Chinese.
Archimedes’ Death Ray
Probably the most famous example of the power of mirrors in trapping heat and intensifying it to a point where it can set things on fire is the so-called Death Ray that is believed to have been used by Archimedes to burn down the fleet of the Romans.
Many experiments have been conducted over the centuries to prove or disprove the possibility of a Death Ray. In modern times, the Mythbusters tried to replicate it and did what their name says they do. Researchers from the MIT managed to make a type of Death Ray that worked, but it only worked in limited circumstances: the system of mirrors only ignited the experimental wood at a distance of 75 feet.
Even if the Death Ray was not real, the power of mirrors is being used to this day. Solar collectors use the same principle of light concentration and reflection to heat water, start fires, and even generate electricity.
The Bill Gates Breakthrough
How far the use of solar energy has come since those first burning mirrors was demonstrated earlier this month when a Bill Gates-funded startup announced a breakthrough. Heliogen said it had succeeded in achieving temperatures of above 1,000 degrees Celsius with its concentrating solar thermal system. This means solar energy could now become a substitute for fossil fuels used in heavy industry precisely because of the high temperatures that they are capable of generating.
The Solar Panel
In 1839, a young French physicist by the name of Edmond Becquerel became the first scientist to observe and replicate the photovoltaic effect: the generation of electric current from light. He replicated the process using two electrodes that he put in a conductor fluid and exposed to light.
A few decades later, in the 1870s, three scientists consecutively discovered the conductive properties of selenium, and in 1883 the first photovoltaic cell was born. The first modern solar cell, the one that uses silicon instead of selenium, was made only last century, in 1954, by three researchers working at the Bell Labs.
To see how far the technology has come since then all you need to do is to look at some efficiency figures. The first solar panels had a conversion (light to electricity) efficiency rate of just 8 percent. This grew to 14 in just three years, but for the next major efficiency improvement the world had to wait until the mid-80s. In 1985, solar panel efficiency rates were raised to 20 percent by researchers at the University of South Wales.
To date, efficiency rates are still below 30 percent for operating solar PV technology, although several labs have announced much higher conversion efficiency rates in experimental work. The latest record-breaker came from Arizona State University, where researchers achieved a conversion efficiency rate of 25.4 percent.
The Future Has Jellyfish in It
The dominant solar power technology today still relies on silicon, but in the future silicon may get dethroned by alternative solar cells. The power generation properties of a certain protein found in jellyfish, for example, have opened up the door to a new kind of LED lighting that could one day replace lighting fixtures and provide light for free.
In organic solar cells, made from polymers, researchers recently came up with the idea of a moving solar panel, mimicking the behavior of sunflowers and following the sun across the sky, which would allow panels made from the material to potentially draw in more energy.
The renewable drive has provided a major spur to solar energy research and we are already seeing the results. Granted, a lot of what is being worked on currently won’t survive in the long term, but those technologies that do survive and prove their commercial potential will be instrumental for the transformation of the global economy into a cleaner, more sustainable one. And it all started with burning mirrors to light fires.
By Irina Slav for Oilprice.com
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