Learn the History of Solar Energy

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Solar energy isn’t new. It is at the root of our existence. Several million years ago, early humans first harnessed solar energy when they learned how to control fire and release the energy that plants had trapped when they were growing. Since then, most developments in harnessing energy were simply improved ways of capturing solar energy, with the exception of nuclear and geothermal power (which ultimately come from pre-solar stars) and tidal energy (from orbital rotation).

From the first water wheels of Ancient Greece to the Three Gorges Dam, hydroelectric power derives from the water that the sun’s energy moves around through the water cycle. The first sailors depicted in Egyptian hieroglyphs and the Gigawatts of offshore wind turbines in the North Sea both depend on the wind energy that comes from the air that the sun’s energy moves around. All the oil, gas and coal on which we still depend release solar energy that was captured in previous eons.

Concentrated solar power also isn’t new. The sun’s energy has been exploited for heating or lighting fires through magnifying glasses since ancient times, such as when Archimedes used giant mirrors to burn Roman ships in the 3rd century BC. Solar thermal energy continues to play a role in technologies such as sunrooms and solar water heaters, but the real game changer for solar energy has been photovoltaics, which convert solar energy directly into electricity.

Directly harnessing the sun’s energy for electricity production became possible with Edmond Becquerel’s discovery of the photovoltaic effect in France in 1839. By illuminating silver chloride in an acidic solution with platinum electrodes, he generated a weak current that was mainly useful for measuring light. American inventor Charles Fritts improved on this through the first selenium solar cell, installed on a New York City rooftop in 1884. It had an efficiency of 1%. Keep reading to see how far we’ve come since then.

Albert Einstein’s 1907 theoretical explanation of the photoelectric effect (for which he won the Nobel Prize) showed that light was not just a wave, but also consisted of packets of energy (photons) that cause electrons to be emitted when they hit a material. This sets the foundation of our understanding of how solar panels ultimately work.  

In 1939, American scientist Russell Ohl discovered the p-n junction, which is the interface between two types of semiconductor materials, and is at the heart of modern electronics and computing. The silicon based solar industry of today traces its roots to Ohl’s experiment with a purified silicon crystal that had been cracked. Ohl noticed that the amount of current passing through the crystal would increase when light shone on it, and he eventually figured out that this was due to different levels of impurities (doping) on either side of the crack. Ohl’s work on the p-n junction also led to the invention of the transistor by William Shockley and his team at Bell Labs, which enabled the creation of integrated circuits and the modern computing industry, including the device on which you are reading this.

The next major breakthrough came in 1952 with the invention of a 6% efficient solar cell by Daryl Chapin, Calvin Fuller and Gerald Pearson at Bell Labs. By introducing gallium-rich silicon into a lithium bath, they created a solar cell that was way ahead of any of the selenium solar cells that existed at the time. By 1954, Fuller had improved on this design with a solar cell that was made by doping silicon with a minute amount of arsenic prior to heating it in a furnace to coat it with boron. Solar panels were soon used to power the radios of the Vanguard I satellite, which was launched in 1958. Several other satellites with a few watts of solar panels soon followed (Vanguard II, Explorer III, Sputnik-3, Nimbus). The next step would be to find applications here on earth.

When the 1970s brought the oil crisis, the world started to realize that alternatives to fossil fuels had to be found, if not for environmental reasons, then at least for geopolitical ones. Countries around the world searched for different alternative energy solutions. France started a buildup of civilian nuclear power that reduced the role of fossil fuels for electricity generation to a minimum. Denmark created a wind energy industry, in which they still play an outsized global role today. In the United States, President Jimmy Carter installed solar thermal panels on the roof of the White House in 1979 to provide hot water. As he presided over the first presidential administration that supported renewable energy (which at the time was called “alternative”), he remarked:

“In the year 2000 this solar water heater behind me, which is being dedicated today, will still be here supplying cheap, efficient energy.... A generation from now, this solar heater can either be a curiosity, a museum piece, an example of a road not taken or it can be just a small part of one of the greatest and most exciting adventures ever undertaken by the American people.”

All of President Carter’s intuitions proved to be correct, if at different moments in history. Unfortunately for solar energy, President Reagan presided over a reactionary backlash against “alternative” energy, and had the solar panels removed from the White House. They were then installed at Maine’s Unity College, where they produced hot water between 1990-2005, after which they became a museum piece at the Smithsonian and in China. So in the last two decades of the 20th century, these panels were indeed an example of a road not taken, since solar panels only found niche uses for watches, calculators and off-grid power systems. President Reagan eviscerated the Department of Energy’s budget for renewable energy research and eliminated tax breaks for solar and wind energy, but could not stop the nascent solar energy industry from slowly growing.

From the late 1990s through the 2000s, solar energy leadership shifted to Japan and Germany, where feed-in tariffs and other favorable legislation spawned the first mass deployment of solar panels. These countries became the first to reach 1 GW of installed capacity, and economies of scale pushed solar energy forward on the experience curve, resulting in sharp cost reductions. In the United States, the solar revolution came a few years later, and it took until 2010 for solar panels (which included both a photovoltaic and water heating system) to return to the White House upon President Obama’s request. From this moment on, we can say that Jimmy Carter’s solar panels now represent the exciting adventure with solar energy that we are living through to this day. In the United States, the Investment Tax Credit (ITC) for solar energy, enacted in 2006, helped drive a rapid expansion of solar energy, but this technology has now matured enough that when the ITC expires in the coming years there will be no slowdown in solar energy.

Another major technological breakthrough that paved the way for solar industry growth was the solar (non-islanding) inverter, invented at Sandia Labs in 2000. This device converts DC (direct current) to AC (alternating current) and, unlike previous designs, automatically curtails electricity production from grid-connected PV systems in the event of a blackout. This is essential to ensure that a power line is de-energized after a blackout and can be worked on safely by line workers. Before the solar inverter existed, utilities would often refuse to connect solar arrays to their networks, since the safety of the line could not be assured in the event of a blackout because the solar array would keep feeding energy to the grid.

When Obama brought back solar panels to the White House in 2010, solar energy was still an emerging technology that depended on subsidies in most applications. Since then, it has grown exponentially (more than 30% in most years), not only becoming an established part of the grid, but also the cheapest source of energy in many countries. As of the start of 2020, solar energy capacity was 586 GW globally, and over 107 GW were added by the start of 2021. As more and more countries adopt renewable portfolio standards and net zero emissions targets, solar energy is expected to continue to grow, surpassing wind energy in 2021 and becoming the top source of energy in the coming decades. The Coronavirus pandemic has only accelerated this trend; despite a 5% drop in global energy consumption in 2020, renewable electricity output (including solar) has increased 7%. This happened because the marginal cost of solar and wind is 0, while that of fossil fuel sources is significant and depends on the fuel being burned. When energy demand is reduced, the first generation source to be shut off is the one with the higher generation cost, so anytime solar energy is available it will be consumed as a first priority.

Solar energy is now an integral part of our energy system, and its growth is no longer a question of prioritizing the environment at the cost of economics. Building a new solar plant is now often cheaper than operating existing fossil fuel generating assets. Although energy storage will certainly play a key role in the further growth of solar energy, we are well on the way to a sustainable future.