Though solar energy has found a dynamic and established role in today’s clean energy economy, there’s a long history behind photovoltaics (PV) that brought the concept of solar energy to fruition. With the way the cost of solar has plummeted in the past decade, it’s easy to forget that going solar had a completely different meaning even just 15 years ago. Let’s go back a few centuries to the origins of solar PV and explore the history of solar energy and silicon solar technology. Inventors have been advancing solar technology for more than a century and a half, and improvements in efficiency and aesthetics keep on coming.
Long before the first Earth Day was celebrated on April 22, 1970, generating awareness about the environment and support for environmental protection, scientists were making the first discoveries in solar energy. It all began with Edmond Becquerel, a young physicist working in France, who in 1839 observed and discovered the photovoltaic effect— a process that produces a voltage or electric current when exposed to light or radiant energy. A few decades later, French mathematician Augustin Mouchot was inspired by the physicist’s work. He began registering patents for solar-powered engines in the 1860s. From France to the U.S., inventors were inspired by the patents of the mathematician and filed for patents on solar-powered devices as early as 1888.
Take a light step back to 1883 when New York inventor Charles Fritts created the first solar cell by coating selenium with a thin layer of gold. Fritts reported that the selenium module produced a current “that is continuous, constant, and of considerable force.” This cell achieved an energy conversion rate of 1 to 2 percent. Most modern solar cells work at an efficiency of 15 to 20 percent. So, Fritts created what was a low impact solar cell, but still, it was the beginning of photovoltaic solar panel innovation in America. Named after Italian physicist, chemist and pioneer of electricity and power, Alessandro Volta, photovoltaic is the more technical term for turning light energy into electricity, and used interchangeably with the term photoelectric.
Only a few years later in 1888, inventor Edward Weston received two patents for solar cells – U.S. Patent 389,124 and U.S. Patent 389,425. For both patents, Weston proposed, “to transform radiant energy derived from the sun into electrical energy, or through electrical energy into mechanical energy.” Light energy is focused via a lens (f) onto the solar cell (a), “a thermopile (an electronic device that converts thermal energy into electrical energy) composed of bars of dissimilar metals.” The light heats up the solar cell and causes electrons to be released and current to flow. In this instance, light creates heat, which creates electricity; this is the exact reverse of the way incandescent light bulb works, converting electricity to heat that then generates light.
That same year, a Russian scientist by the name of Aleksandr Stoletov created the first solar cell based on the photoelectric effect, which is when light falls on a material and electrons are released. This effect was first observed by a German physicist, Heinrich Hertz. In his research, Hertz discovered that more power was created by ultraviolet light than visible light. Today, solar cells use the photoelectric effect to convert sunlight into power. In 1894, American inventor Melvin Severy received patents 527,377 for an “Apparatus for mounting and operating thermopiles” and 527,379 for an “Apparatus for generating electricity by solar heat.” Both patents were essentially early solar cells based on the discovery of the photoelectric effect. The first generated “electricity by the action of solar heat upon a thermo-pile” and could produce a constant electric current during the daily and annual movements of the sun, which alleviated anyone from having to move the thermopile according to the sun’s movements. Severy’s second patent from 1889 was also meant for using the sun’s thermal energy to produce electricity for heat, light and power. The “thermos piles,” or solar cells as we call them today, were mounted on a standard to allow them to be controlled in the vertical direction as well as on a turntable, which enabled them to move in a horizontal plane. “By the combination of these two movements, the face of the pile can be maintained opposite the sun all times of the day and all seasons of the year,” reads the patent.
Almost a decade later, American inventor Harry Reagan received patents for thermal batteries, which are structures used to store and release thermal energy. The thermal battery was invented to collect and store heat by having a large mass that can heat and release energy. It does not store electricity but “heat,” however, systems today use this technology to generate electricity by conventional turbines. In 1897, Reagan was granted U.S. patent 588,177 for an “application of solar heat to thermo batteries.” In the claims of the patent, Reagan said his invention included “a novel construction of apparatus in which the sun’s rays are utilized for heating thermo-batteries, the object being to concentrate the sun’s rays to a focus and have one set of junctions of a thermo-battery at the focus of the rays, while suitable cooling devices are applied to the other junctions of said thermo-battery.” His invention was a means to collecting, storing and distributing solar heat as needed.
In 1913, William Coblentz, of Washington, D.C., received patent 1,077,219 for a “thermal generator,” which was a device that used light rays “to generate an electric current of such a capacity to do useful work.” He also meant for the invention to have cheap and strong construction. Although this patent was not for a solar panel, these thermal generators were invented to either convert heat directly into electricity or to transform that energy into power for heating and cooling.
By the 1950s, Bell Laboratories realized that semiconducting materials such as silicon were more efficient than selenium. They managed to create a solar cell that was 6 percent efficient. Inventors Daryl Chapin, Calvin Fuller, and Gerald Pearson (inducted to the National Inventors Hall of Fame in 2008) were the brains behind the silicon solar cell at Bell Labs. While it was considered the first practical device for converting solar energy to electricity, it was still cost prohibitive for most people. Silicon solar cells are expensive to produce, and when you combine multiple cells to create a solar panel, it’s even more expensive for the public to purchase.
The year is 1956, and the first solar cells are available commercially. The cost however is far from the reach of everyday people. At $300 for a 1 watt solar cell, the expense was far beyond anyone’s means. 1956 started showing us the first solar cells used in toys and radios. These novelty items were the first item to have solar cells available to consumers.
In the late 1950s and early 1960s satellites in the USA’s and Soviet’s space program were powered by solar cells and in the late 1960s solar power was basically the standard for powering space bound satellites.
In the early 1970s a way to lower the cost of solar cells was discovered. This brought the price down from $100 per watt to around $20 per watt. This research was spearheaded by Exxon. Most off-shore oil rigs used the solar cells to power the waning lights on the top of the rigs.
The period from the 1970s to the 1990s saw quite a change in the usage of solar cells. They began showing up on railroad crossings, in remote places to power homes, Australia used solar cells in their microwave towers to expand their telecommunication capabilities. Even desert regions saw solar power bring water to the soil where line fed power was not an option!
Today we see solar cells in a wide variety of places. You may see solar-powered cars. There is even a solar-powered aircraft that has flown higher than any other aircraft with the exception of the Blackbird. With the cost of solar cells well within everyone’s budget, solar power has never looked so tempting.
Recently new technology has given us screen-printed solar cells, and a solar fabric that can be used to side a house, even solar shingles that install on our roofs. International markets have opened up and solar panel manufacturers are now playing a key role in the solar power industry.