Solar panels are rapidly becoming a common sight on homes, but once upon a time they were little more than a rare curiosity. How did we get from using solar energy on satellites to it becoming the most affordable source of electricity? Is there anything about its historical trajectory that might suggest where it’s headed next?
To dig into these juicy questions, we spoke with the guy who wrote the book on solar power’s history, John Perlin. The history he took us through had some unexpected twists.
How do solar panels even work?
Let’s start with the basics of photovoltaics. Trust me, this is helpful context for explaining how the technology evolved over time.
Fundamentally, electricity is the flow of electrons. Some molecules are missing electrons compared to their stable state. Other molecules have too many electrons. With enough energy, electrons can hop off a molecule with too many and onto another with too few. That movement of electrons can become an electrical current.
Solar panels harness this by having one silicon wafer with too many electrons (called N-type because electrons introduce a negative charge) sandwiched on top of another with too few (called P-type because it’s effectively positively charged). When sunlight hits the N-type layer, the panel can absorb enough energy to dislodge an excess electron. At first, those electrons will go right to the the P-type to fill any available holes, but those gaps are filled pretty quickly. This leaves a depleted area where the two layers meet. The nearby electron holes are filled, and more electrons can’t easily go through.
Luckily, there’s an alternative route. It just so happens that taking that route is going to power all of our stuff in the process. Thin conductive strips are applied along the top of the N-type layer to send electrons down this road.
After being whisked from the upper silicon layer, an electron goes through an inverter, which turns the direct current into an alternating current that’s usable by everyday devices. Then the electron is run though whatever needs electricity.
After the electron has done its work, the circuit is completed when it returns to the bottom layer of the silicon. Outside of the depletion area, the P-type layer still has too few electrons and is ready to receive at the other end. Things might end there with electrons finally finding their home, but the N-type layer of a solar panel is thin enough that light can reach through to the P-type, dislodge the electrons there, and bump them back to the upper level to go through the whole process again.
If you want to dig into the nitty-gritty, we have a longer explainer on how solar panels work here.
A bumpy start
The first recorded photovoltaic solar panel was installed in New York City in 1884 by Charles Fritts. It was built upon the work of French physicist Edmond Becquerel, who had made the first individual solar cell just a few years prior. Fritts’ panel wasn’t terribly efficient, capturing just 1% of solar energy as electricity.
Another inventor, George Cove, took a different tack. Instead of using the sun’s light, his machine used the sun’s heat to generate electrical current. That concept wasn’t new at the time, but the theory is still in use today with thermoelectric generators. It appears as if Cove took over Fritts’ lab, but this was short-lived. Cove’s work was marred by controversy.
Following significant external investment in his solar power company, Cove was abducted by American capitalists with an aim to get him to stop his work. That might have had something to do with claims that his solar panel was actually just drawing power from the electrical grid rather than generating any of its own, constituting fraud. Others think Cove wasn’t actually abducted at all, and simply sought publicity. It equally may have been the work of nervous competitors whose business depended on fossil fuel power.
Whatever the case may have been, by 1911, the rise of coal and oil buried the promise of these early solar panels for decades to come.
Einstein changes everything
Classic Einstein, upending everything we know. Before he came strutting along, wiry locks flowing in the breeze, it was generally accepted that light acted as a wave. For example, light coming from two different sources doesn’t bounce off one another, as would be the case if light was a particle. The light from either source just passes through one another, like a wave.
Einstein, however, was able to prove that light acts both as a particle and a wave. He did this by observing how a metal reacted when subjected to light at certain wavelengths. In short, he demonstrated that some kinds of light had enough particle properties to knock electrons from metals out of place.
The implications for solar panels were huge. Einstein showed that shorter wavelengths carried higher energy. That shorter wavelength didn’t penetrate as deeply into a material, however. This meant solar panels needed to have their more active elements (like where P-type layer and the N-type layer meet) closer to the surface so light particles, photons, could knock out electrons at that junction. The potential for improved efficiency reignited interest in solar technology.
Silicon gets an upgrade
The promise of solar panels re-emerged in the world of telecommunications. In the 1950’s, Bell Labs was tasked with finding an alternative to dry cell batteries that kept degrading in tropical climates and impacting local telephone service. The lead researcher, Daryl Chapin, set about exploring solar power as a solution.
The word “doping” doesn’t exactly have a positive connotation, but it was an important advancement in solar panel technology. At that point, solar panel semiconductors were rather limited. The element selenium was being used, and was still not efficient enough to be practical. After some experimentation, Bell Labs had discovered that introducing impurities to silicon significantly improved its performance as a semiconductor.
It was found that adding (or doping) the upper layer of silicon with phosphorous added many more electrons to the mix. Likewise, adding boron to the lower layer added more electron holes to fill. This greater disparity in charges increased electron flow between the two layers where they met. At 6% efficiency, solar panels were finally ready for real-world use.
The Space Race
Well, maybe just a little outside this world. At this point, the Soviets and Americans were locked in The Space Race. Satellites had been launched, but their lifespans were limited to weeks by the batteries they launched with. The U.S. government was keen to fund solutions that would put them ahead in the Cold War. An ex-Nazi, Hans Ziegler, had come to the U.S. under the auspices of Operation Paperclip. Paperclip was a secret American program aimed at bringing German scientists into the fold following World War II, while evading domestic bans on Nazi immigrants.
“The irony of this whole history is considering the solar cell as something hippy-dippy. It was actually pushed by the military-industrial complex in America.” — John Perlin
Ziegler sought to introduce solar cells to satellites. Despite internal skepticism, Ziegler’s first test on the Vanguard 1 satellite was approved and launched in 1958. Though the mission was scheduled to last 90 days, it was able to communicate back to Earth for over six years thanks to its solar panels. Vanguard 1 is actually still up there in orbit today. The case was made for solar power, and it quickly became the standard for all satellite launches moving forward.
Big Oil bets on solar
Exxon has a reputation as an arch nemesis of the climate movement, which is why it was so surprising when Perlin told us Exxon deployed the first commercial rollout of terrestrial solar panels.
Exxon had a multitude of off-shore drilling and other remote operations that needed power. Many of them relied on primary batteries that were rather expensive and couldn’t be recharged. Cells were sometimes dumped in the ocean when they were depleted. At one point, a bunch of that e-waste washed up on Houston’s shores, which understandably made some people angry.
In the wake of this controversy, Exxon went shopping for alternatives. Researcher Elliot Berman had been widely promoting solar power, and after working with Exxon on exploring the opportunity, he was picked to run Exxon’s wholly-owned solar subsidiary, Solar Power Corporation. Here, Berman developed a great way of reducing costs. Most silicon was made by smelting quartz (sand) into a large ingot, and then shaving wafers off it. This process created a monocrystalline atomic structure that was efficient when it came to solar power production, but there was another option.
Berman wanted to capitalize on solar panels that didn’t make the cut for space travel. He was able to tap into that inventory and generate polycrystalline silicon by combining silicon scraps. He was able to use silicon from the wider electronics industry, too. The resulting polycrystalline wasn’t quite as efficient as monocrystalline solar panels due to the mishmash of crystal growth, but they were about five times cheaper to make.
With solar’s successful use established in space and costs reduced thanks to Berman’s work, Exxon started trying solar panels on their platforms. Sure enough, solar worked great. It didn’t take long for other industries to notice and start adopting solar for other remote operations.
America’s energy independence
Oil’s role in the advancement of solar power wasn’t over yet. A global tightening of oil supply by OPEC in 1973 had the U.S. looking for ways to reduce dependence on a volatile Middle East market. While Exxon was actively working to diversify on the chance that it couldn’t stay in the oil business, solar was lower on the government’s priorities.
For all of the press Jimmy Carter got for putting a solar water heater on top of the White House, he still had a background as a nuclear engineer. While he promoted solar alongside energy conservation as means to energy independence, his policies heavily favored nuclear power and coal. Carter even shot down requests from the military to adopt solar power for its own remote operation needs. Bell Labs had encountered similar headwinds in the ’50s as Eisenhower’s Atoms for Peace program promoted nuclear power as the way of the future.
Ultimately, America ended up finding greater domestic oil reserves and had a significant surplus through the ’80s.
China steps in
Up to this point, America had established itself as the epicenter of solar panel development. After all, Americans had pioneered early research, taken the technology into outer space, and pushed for power independence. That was about to change.
See, Australian telecom service providers had been legislated into providing service in rural areas, and they encountered the same types of problems that Bell Labs once did. Vast swathes of Australia are dang hot, and running gas or batteries out to relay towers in the Outback isn’t exactly practical.
This problem prompted investment in solutions, including the eventual development of the passive emitter and rear cell (or PERC) by Martin Green at New South Wales University. Crucially, this reduced the heat absorption of solar panels so they could continue to operate at high temperatures. It also had the benefit of bouncing light back into the silicon for a second chance of absorption. This improved efficiency to up to 25%. Nowadays, about 90% of solar panels use PERC cells.
“The tragedy is that the only government that really showed any enthusiasm in solar was the Chinese government. What initially began as an American invention with the Bell solar cell, now China produces 80% or 90% of the solar material in the world.” — John Perlin
Despite the domestic need, the political landscape wasn’t conducive to Green advancing his technology. Like America, Australia had vested interests in fossil fuels, which actively opposed photovoltaics. Neighboring China had no such ties. There, Green was able to court potential students.
One of Green’s Ph.D. students, Shi Zhengrong, took the new PERC technology to China, and raised sufficient capital to start cranking out solar cells in 2002 as a manufacturer called Suntech. On top of solving Australia’s telecom power needs, most of the panels were going to Germany to take advantage of large government incentives for renewable energy production.
Many of Suntech’s investors came via Green’s contact with American technical experts. These contacts eventually led to Suntech becoming the first private company based in China to list on the New York Stock Exchange. The interest gained momentum to the point that multiple other Chinese solar manufacturers popped up to tap into American investment. Rabid competition between them drove down prices as a result.
Even with American money and Chinese government support, the 2008 financial crisis made those low prices unsustainable for some players. Still, many of these large Chinese solar panel manufacturers managed to secure American investment early and ramp up to mass production quickly enough to survive the financial crisis and ultimately secure ongoing, historically low prices on solar power. The solar panel on Vanguard 1 had cost $100 per Watt, but today is under $3 per Watt.
What’s next for solar panels?
Solar panels may seem to be have popped up everywhere in only the last few years, but they’ve been inching toward this moment in the sun for over a century. Early photovoltaic theory paved the way for Einstein’s discovery of light acting as a wave and particle. Bell Labs translated theory to reality, which got solar panels sent into space, which in turn proved the case to Exxon that it (and subsequently other industries) could use solar for remote operations. While America started drifting more toward fossil fuels, China proved to be fertile ground for investors and researchers to start producing solar panels at scale and drive prices downward.
Now solar installations across the U.S. have been accelerating at unprecedented rate. Perlin remains optimistic about the next stages. While a popular utopian vision might have a solar panel on every roof, Perlin sees the biggest progress happening at commercial-scale solar power plants. So while we may not all look up and see silicon every day, there’s a good chance it will continue to power more and more of modern life, behind the scenes.
