Albert Einstein played a vital role in the development of modern solar technology!

Solar energy is not a new technology. Humans and the sun share a long history that spans many centuries. Thousands of years ago, we used magnifying lenses to ignite the kindling that warmed our caves. Today, we use solar energy to power our homes, our businesses and our streetlights. Heck, we even strapped solar panels onto the rovers that traverse the Martian landscape.

In this article, we break down this vast history of solar power into 12 significant milestones. We discuss the most important scientific breakthroughs in solar technology, but we also leave a little room to share a few light-hearted mile markers, including the fabled solar-powered “death ray.”

Solar power truly is the stuff of legends.

Milestones in the Development of Modern Solar Technology

7th Century B.C.E.: Humans Used Magnifying Glass to Light Fires

Hand lens — A very ancient technology, convex and concave lenses refer to how the glass refracts (or changes the direction of) light.

When you think of “B.C.E.,” The Flintstones, cave drawings and primitive living arrangements come to mind. But quite the contrary, my friend. In the 7th century B.C.E., humans discovered that, by concentrating the sun’s rays onto a small area using a convex lens (thicker in the center and thinner at the edges), they could focus enough heat to create fire.

Also known as burning glass or fire lenses, this technology is as simple as solar energy gets. It’s the first significant form of solar technology other than drying fruits and meats under the sun.

212 B.C.E.: Archimedes and the Legendary Solar Death Ray

The next significant milestone was the invention of burning mirrors. Similar to burning glass, this form of technology involves reflecting the sun off of mirrors rather than concentrating it.

This can be best illustrated through the lens of none other than Greek mathematician Archimedes and his fabled “death ray.” Consisting of giant mirrors that concentrated the sun’s rays onto enemy ships, this tool was so powerful that Archimedes allegedly decimated an entire Roman fleet!²

Many wonder whether this historical account was just a tall tale. The Massachusetts Institute of Technology conducted a successful experiment in 2005.³ However, the death ray was tested on Mythbusters in 2006, but it was declared “Busted” after having failed twice.²

Fun fact: This is still how the Olympic flame is lit: Through concentrated solar rays via a parabolic mirror.⁴

Whether it was truth or trick, it’s not ours to say. Our point is that this technology, which was indeed not a myth, serves as the direct precursor to concentrating solar power (CSP) plants. They use highly reflective mirrors to concentrate sunlight on a single point then heat water to drive steam turbines and produce electricity.

1839: Edmond Becquerel Discovered the Photovoltaic Effect

While solar power was a recognized thermal energy source for centuries, the building blocks for modern photovoltaic (PV) solar panels didn’t arise until the early 19th century with Alexandre-Edmond Becquerel, a French physicist.

While many have debated who should receive credit for solar cell technology, nearly everyone acknowledges that Edmond Becquerel discovered the photovoltaic effect. This process generates an electric current when a material is exposed to sunlight. Becquerel’s experiment involved two metals, either gold or platinum, being placed in an electricity-conducting solution and exposed to sunlight.⁵

In essence, this is how modern PV cells within solar panels work, and it would later be the basis of Einstein’s photoelectric effect (check it out below).

1876: William Grylls Adams Discovered Certain Metals Produce Electricity When Exposed to Light

A few years earlier in 1873, English electrical engineer Willoughby Smith discovered that the element selenium has photoconductive properties. This meant it had increased electrical conductivity caused by the presence of light. This finding led to William Grylls Adams and his student, Richard Evans Day, to discover that selenium could produce electricity.⁶

Although they didn’t generate enough electricity to power anything, it did prove that materials didn’t need to be dunked in any solution or heated. Instead, they could produce electricity with only sunlight.⁷

1883: Charles Fritts Created the First Solar Cell with 1% Efficiency

Photo of the very first solar cell created by American inventor Charles Fritts — This conglomeration of white tiles was actually the very first solar cell created by Charles Fritts (Smithsonianmag.com)

The very first solar cell was created by Charles Fritts. The American inventor took selenium wafers, similar to the silicon wafers used in today’s solar panels, and wrapped them in thin gold foil. This setup was sufficient enough to generate an electric current with a little less than 1% efficiency!⁸

Today’s silicon solar cells operate at around 15 to 18% efficiency, so Fritts hadn’t solved everything.⁹ Still, his discovery would have many applications — even today. The element is still used to test light exposure for photography, so, next time you snap a pic, remember Charles Fritts!

1921: Albert Einstein Won the Nobel Prize for His Discovery of the Photoelectric Effect

Black and white portrait of Albert Einstein — Albert Einstein invented more than just E= mc² and the theory of relativity.

You might know Albert Einstein for his theory of relativity and famous equation, E=mc². However, his Nobel Prize was for neither of those — it was actually for discovering the photoelectric effect in 1905. This principle states that, when sunlight shines on a metal, it emits electrons from the surface of the material. The energy from sunlight (photons) then transfers to the atoms’ electrons and knocks them loose.

This discovery was so significant that it has influenced the development of many types of technology, from electron microscopes to modern solar cells as we know them today.¹⁰

1941: Russell Ohl Patented the First Silicon Photovoltaic Cell

However, that’s not exactly what Einstein intended to do with his discovery. Thus, in 1927, American engineer Russell Ohl went to work at Bell Labs to improve radio broadcasting capabilities. Most of Ohl’s research involved purifying silicon crystals so radio tuners could handle higher frequencies.¹¹

Little did he know that he would accidentally discover the p-n junction, the building block for how solar panels work to this day!¹² Here’s what happens:

The “p” side of the metal is positively charged silicon.
The “n” side is negatively charged.
When the negative silicon is exposed to light, it knocks loose the negative electrons, which are attracted to the positive side.
This creates an electric current between the two panels.

Voila! Electricity!

This discovery is why many modern solar panels, including the ones we operate at Chariot, are made from ultra-pure polysilicon.

1954: Bell Labs Unveiled the First Practical Solar Cell

Next, it’s time to introduce the first silicon solar cell that could provide significant amounts of electricity. On April 25, 1954, Daryl Chapin, Calvin Fuller and Gerald Pearson demonstrated a solar cell that was 4% efficient. More efficient than any other solar-powered device of that era, it produced several hours’ worth of photovoltaic (PV) power.⁸

From this point on, solar would grow exponentially, and PV cells would only get more efficient. This was a major breakthrough in the history of solar power.

1958: The First Solar-Powered Satellite Successfully Launched into Space

One of NASA's Vanguard satellites — Source: NASA

We mentioned the Mars Rover above, but many other events had to happen before that was possible. The first and most significant of these was the launch of space satellite Vanguard 1. It was the first successful satellite to use solar power, and it’s actually the oldest satellite still orbiting Earth. Although the satellite used a small solar array, the cells produced around 1 Watt with 10% efficiency. This is why solar energy remains a main source of power for space applications.¹³

1973: The University of Delaware Built the World’s First Solar Photovoltaic Powered Home

The Institute of Energy Conversion at the University of Delaware created one of the world’s first homes that converted solar energy into heat and electricity for domestic use. The house utilized rooftop PV systems as well as solar thermal energy (i.e. solar heating and cooling) during the day. At night, the house used power from the grid since solar electricity generation doesn’t work at night.¹⁴

This setup would eventually morph into the concept known as net metering. This is where a homeowner’s solar panel provides electricity during the day — and often sells back excess generated electricity to the grid — and the electric company provides power at night.

2013: President Obama Installed Solar Panels on the White House

Technically, the 43rd president was the third one to do so, as solar panels were installed two other times before Obama’s time in office. In 1979, Jimmy Carter was the first president to install solar panels on the White House — 32 of them!¹⁵ However, the Reagan administration dismantled them due to a roof leak and chose not to reinstall them, with his chief of staff calling them “a joke.”

In 2003, President George W. Bush brought solar power back to the White House by installing a photovoltaic system, as well as two solar thermal systems that heat water.¹⁵ Obama bolstered that setup with even more solar panels in 2013.¹⁶

Here’s why we included this: These acts were largely political. According to the Department of Energy, Obama wanted to show that solar technologies were available, reliable and ready to install in homes across the country.¹⁷ In 2016, Obama furthered his commitment to clean energy by announcing the Clean Energy for All Americans Initiative. Through this initiative, the administration announced a goal to bring 1 gigawatt (GW) of solar electricity to low- and moderate-income families by 2020.¹⁸

For reference, 1 gigawatt of electricity is equal to 3.125 million PV panels.¹⁹ Wow!

Present Day: Solar Energy Powers Millions of Homes Around the World

So, this brings us to the present. You must be wondering, “What is the state of solar energy today? More importantly, where is the industry expected to be five years from now? 10? 20?”

According to the Solar Energy Industries Association, the U.S. has 69.1 GW of total installed solar PV capacity as of September 2019. This is enough energy to power more than 13 million homes! By 2024, more than 15 GW of PV capacity will be installed annually.²⁰

Keep in mind this is just the U.S. PV capacity, which doesn’t include Concentrated Solar Power plants and passive solar. Plus, this is with panels that operate at an average of 15 to 18 percent efficiency.

Clearly, solar still has a ways to go — but we’re so excited about what the future entails! Average solar panels by 2040 may be operating at 30 or 40 percent efficiency. Solar panels might also become the most affordable energy resource out there. The sun is the limit when it comes to innovation in solar tech.

Sources:

Looking Back at the History of Solar Energy