Clean Power

Published on January 6th, 2015 | by Glenn Meyers

7

Einstein: The Father of Photovoltaics — Part 1

January 6th, 2015 by  


Einstein and photovoltaics, the sixth entry in our CleanTechnica miniseries launching the new year continues by celebrating the UN’s 2015 Year of Light. Here, physicist John Perlin, author of Let It Shine: The 6000-Year Story of Solar Energy, reveals that Albert Einstein is the father of modern photovoltaics.

Perlin’s expertise on solar energy is considerable. Let It Shine is the only book that has thoroughly chronicled the development and application of solar throughout time, focusing on key themes, people, and events that have laid the foundation for an enduring Solar Age.

Perlin first solar array Old Solar Pictures 01-3

The first solar array — 1884 — installed on a New York City rooftop by Charles Fritts.

We have reported on Willoughby Smith and his startling experiments proving the photosensitivity of selenium. The year: 1872. It was this discovery that stirred keen interest in two British scientists, William Grylls Adams and Richard Evans Day. (Other previous posts in this miniseries: Author John Perlin Celebrates the Coming Year of Light, Author John Perlin & the Solar Cell, The Pathway to Today’s Solar Revolution: Discovering the Photosensitivity of Selenium, Photovoltaics Discovered in 1875: Interview with Author John Perlin; and Photovoltaic Dreaming: First Attempts at Commercializing PV.)

Our fifth post concerned what happened after news of the photovoltaic effect had reached other scientists, inspiring a Charles Fritts, an American inventor, who built the first solar panels in 1881. Of his work, Fritts reported a current “that is continuous, constant and of considerable force not only by exposure to sunlight but also to dim, diffused daylight.”

In our last episode on English scientist George Minchin, Minchin suggested that the energy of light might differ with wave length and therefore might provide the scientific explanation for photovoltaics. Perlin pointed out that such a viewpoint was nothing short of heresy, as the wave theory of light, a basic precept of 19th century science, required the notion that light’s intensity depended on the incoming amount, not the variation, of its length. Here is our interview with Mr. Perlin:

CleanTechnica: Please elaborate on why Minchin’s concept might be regarded as scientific heresy.

Perlin: A newly discovered phenomenon – light causing materials to shed electrons – called the photoelectric effect – brought into question the wave theory.

Physicist Philip Lenard, for example, discovered in 1902 that increasing the amount of light striking a material did not intensify the energy of the electrons it shed in the process; but by increasing light’s frequency, i.e., decreasing the wave length, it did.

CleanTechnica: Were there other experiments like this?

Perlin: Yes. In another experiment, no matter how much light of long wave lengths poured onto an object no reaction occurred while just the faintest exposure to shorter wave light a photoelectric effect could be measured. These observations did not jibe with wave theory where merely adding more light should have sufficed.

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CleanTechnica: How does Albert Einstein become related to such heretical theories?

Perlin: Einstein, among all his contemporaries, came up with the simplest yet the boldest and most revolutionary explanation. In one short but elegant equation, Einstein demonstrated what Minchin had earlier alluded to, that science had hitherto failed to account for all the energy flowing from the sun.

CleanTechnica: Can you share his equation, and elaborate?

Perlin: E=hv, where E is energy, h is Plank’s constant, and v is the frequency of light.  In his simple equation, containing only two variables, he showed that light waves carry packets of energy he called light quanta and presently referred to as photons. Einstein went on to show that intensity of light quanta, as Minchin had suspected, vary according to the wave length – the shorter, the more energy they pack.

CleanTechnica: Obviously, Einstein’s work was not initially embraced?

Perlin: Absolutely. Einstein’s colleagues made no rush to embrace his radical revision of light. Seeing light as both waves and energetic particles stunned even his strongest supporters. His closest colleagues charged that he had “missed the target in his speculations [concerning] light quanta.” Like everyone else in the field, they saw it as an attack on one of the pillars that held up the edifice of 19th century science.

CleanTechnica: Did the list of naysayers include the renowned American physicist, Milliken?

Perlin: Yes. Even after proving the validity of Einstein’s light quanta equation in explaining the photoelectric effect, Milliken dismissed the physicality of the photon as “untenable.” In 1923, 18 years after Einstein published his light quanta piece, American physicist, Arthur Hailey Compton, created a collision between a stationary electron and a short wave of light. Just as in billiards, when the cue ball strikes its target, the light wave transferred some of its energy and momentum to the electron. This is exactly what happened in Adams and Day’s experiment: sufficiently energized photons radiating from the candle’s flame struck electrons in the selenium. They transferred energy and momentum to the electrons. Science defines electricity as the movement of energized electrons. After the Compton Experiment, the reality of Einstein’s photon and the photovoltaic effect gained universal acceptance in the scientific community.

 

In the next episode, we show the role that Einstein’s most famous equation, E = mc2 , explains how the sun generates solar PV’s fuel.

Photo Credits: First solar array, via Let It ShineWax figure of Albert Einstein in Berlin, via Shutterstock






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About the Author

is a writer, producer, and director. Meyers was editor and site director of Green Building Elements, a contributing writer for CleanTechnica, and is founder of Green Streets MediaTrain, a communications connection and eLearning hub. As an independent producer, he's been involved in the development, production and distribution of television and distance learning programs for both the education industry and corporate sector. He also is an avid gardener and loves sustainable innovation.



  • DaveW.

    Typo: that’s Arthur Holly Compton

  • Michael G

    The discovery of Photovoltaics is attributable to many people working on the same problem. Einstein’s contribution was in the understanding of what was going on, not the equation itself. Being able to make it work is great. Knowing why it works is essential to making any improvements. That it was astounding to many scientists of his day shows that it isn’t the math, it’s the physics that is tough. The full equation is E = hv – “phi” (the work function) which also partially explains electron levels in atomic structure. Even now, the wave-particle duality of everything (energy and matter) is difficult to comprehend.

    Similarly, in “Special relativity”, he interpreted the results from the already known Lorentz equation in a revolutionary way. Lorentz correctly described what was happening with his equation, but couldn’t make the leap to provide a coherent reason for it working. Einstein simply said there is no “ether” – that is, there is no single universal reference frame, the laws of physics are the same in all inertial reference frames. A simple and elegant explanation of what had puzzled brilliant physicists of his time. Sounds simple but the implications are astonishing. The general theory of relativity was quite a bit more mathematically complicated and predicted light photons (which have no mass) would be bent by gravity which was experimentally verified later. Einstein took years to work out the laws of general relativity – finished in 1916.

    http://en.wikipedia.org/wiki/Annus_Mirabilis_papers

  • Larmion

    Isn’t the Plank-Einstein relation E = h*nu an invention of Max Planck himself rather than of Einstein? While I’m not sure he ever wrote it down in that notation, he used this relation to calculate the value of Planck’s constant.

  • Tam Hunt

    And it’s good to mention that Einstein eventually won the 1921 Nobel Prize primarily for his work on the photoelectric effect.

  • Marion Meads

    Great and simple is Einstein’s equation, i wouldn’t attribute him to be the father of Photovoltaics. Einstein did not make a single usable one PV, and regardless of his equation and influence PV were manufactured and has progressed tremendously. Being the “father” means that without your discovery, the industry would be nothing. The fact is, someone else, named Fritts, long before Einstein have made the first PV, so how can Einstein be the father of PV?

    Next, you want to celebrate Perlin as the father of something in clean energy history?

    • Joseph Dubeau

      CleanTechnica: Isn’t the Einstein connection really just name dropping.
      Perlin: Well yes, you got me there. 🙂

    • Larmion

      Providing a fundamental understanding of the underlying science behind a phenomenon is usually an essential step in the transition from hobby project to world-changing invention.

      Do you really think that progress in PV would have come at half the rate it has if we didn’t understand the physics behind PV and thus knew what we had to improve or change?

      If you randomly let monkeys bash a typewriter, chances are they’ll eventually type a poem by accident – but not before ruining a few typewriters and wasting thousands of sheets of paper. And that’s what attempting to engineer/invent something without understanding the fundamental science behind it really is. Randomly pressing buttons in the hope eventually something happens.

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