Solar Sunday Photo of the Day April 22, 2018

What better Solar Sunday Photo of the Day to post on Earth Day than this photo taken April 25, 1954, of the world’s first feasible working solar cell. Happy 64th Birthday! The proud inventors are (L-R) Gerald Pearson, Darryl Chapin and Calvin Fuller of Bell Laboratories.

They needed to stand on the shoulders of a few giants to get there, but when this engineer, chemist and physicist started working together they came up with what The New York Times said “may mark the beginning of a new era, leading eventually to the realization of one of mankind’s most cherished dreams–the harnessing of the almost limitless energy of the sun for the uses of civilization.”

The Times was right, but they probably didn’t suspect it would take this long.

An 1883 solar cell had 1% efficiency

The first solar cell was actually constructed in 1883 by a fellow named Charles Fritts using a material called selenium. But it was less than 1% efficient at turning the sun’s light energy into electrical energy. (BTW, you can find out a lot about the history of solar cells and solar energy by listening to a couple of 7minutesolar podcasts: A Brief History of Solar Power and How Does a Solar Cell Work?

Fritts even had an array of solar panels constructed on a New York rooftop. In 1884! But that 1% efficiency rate was obviously going to be a bit of a problem.

Solar array on a NYC Roof 1883
Solar array on a NYC Roof 1883

Then in 1940 a fellow named Russell Shoemaker Ohl of Bell Labs was working with a piece of silicon that cracked and when he shone light on it he quite accidentally discover that silicon might be a better element to use for photovoltaics (tunring light into electricity). He showed that silicon could create an electric current that has an efficiency of a full 1%!

Move on to the 1950s at Bell. Engineer Darryl Chapin is working on potential power sources for telephones in remote places with high humidity. The batteries of the time went dead too quickly. He’s experimnting with selenium as a possibility.

On a totally different project  chemist Fuller and physicist Pearson, a physicist, are trying to improve on Ohl’s work by mixing silicon – ‘doping’ it – with small amounts of fancy sounding chemicals like gallium and lithium.

Pearson was friends with Chaplin and told him to drop the selenium, that silicon looked like the more promising material. So the three started working together, trying to conquer some other problems that came along with using lithium aa the doping agent. They eventually solved that with arsenic and boron and filed their patent in 1953.

Their solar cell was 6 times as efficient ( 6%!), and they proudly introduced it to the world by demonstrating how sunlight could run a little toy ferris wheel.

From 1 watt at $300 to 300 GigaWatts at $1 per watt

Like any new technology, none of this was cheap. In fact, a 1 watt solar cell coast about $300. And it wasn’t really until the space race of the 60s that there was a use for them. But the price kept dropping and the efficiency kept going up. Simple silicon cells are now at about 25% efficiency, getting close to silicon’s maximum theoretical efficiency of about 33%. But lots of other types of cells are in use or under development.

As for price, greentechmedia reported in September that “U.S. utility-scale fixed-tilt system pricing fell below $1.00 per watt earlier this year”

The chart on the left shows the cost of solar cells dropping. The chart on the right demonstrates ‘Swanson’s Law’: the more cells and panels produced, the lower the cost per unit.

Price of solar cells and panels drop under Swansons Law


Let’s skip ahead 64 years now.

Here’s a 2017 chart from The Guardian, based on data from SolarPower Europe that shows the exponential growth of solar power around the world since 2000.

SolarPower Europe - worldwide growth of solar

And the International Energy Association says “Solar PV is entering a new era. For the next five years, solar PV represents the largest annual capacity additions for renewables, well above wind and hydro. This marks a turning point and underpins our more optimistic solar PV forecast which is revised up by over one-third compared to last year’s report.

You can read the whole article here, but a couple of other highlights:

In the Renewables 2017 main case forecast, total solar PV capacity around the world reaches 740 GW by 2022 – more than the combined total power capacities of India and Japan today.

Under an accelerated case – where government policy lifts barriers to growth – IEA analysis finds that renewable capacity growth could be boosted by another 30%, totalling an extra 1,150 GW by 2022.

IEA - Growth of Renewable Energy Sources

Back in 1883, when Mr. Fritts put together that selenium cell and put the array on Manhattan rooftop, he had the idea that solar power could compete with coal-fired power plants.

It’s taken a long time, but as the IEA’s charts show…we’re getting there!

7minutesolar Solar Sunday and Wind Power Wednesday Photos of the Day

 Know of a photo you think should be a 7minutesolar POTD? Let us know. Wednesdays are Wind Power POTD and the weekend has the Sunday Solar POTD.

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