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Lighten Up: 21 Solar Facts for the Summer Solstice

To celebrate the summer solstice, we put together this list of facts about solar power.


June 21 is the summer solstice – or, for the unenlightened, the longest day of the year in terms of daylight. To celebrate, we thought we’d share some facts on solar energy, and illuminate why the industry is advancing at light speed.

1.More energy from the sun lands on the face of the earth in just one hour than the entire global population uses in one year.

We have all the solar power we could want. Plus, unlike fossil fuels, it’s renewable and will never run out – at least not for a few billion years.

2. The US Department of Energy estimated that 90 percent of the electricity used by the US could be generated from solar panels installed in abandoned industrial sites in our nation’s cities.

The Department of Energy put this figure out in 2003 – and in the ~15 years since, solar panel efficiency has risen and costs have fallen. Across US cities, there are millions of acres that are occupied by abandoned industrial sites – factories, plants, etc. Installing solar panels would put that space to a productive use and create a significant amount of clean energy.

3. Elon Musk projects that solar energy will become the world’s largest energy source by the year 2031.

He’s not alone. The International Energy Agency has also projected that it won’t be long before solar dominates global electricity production. 

Musk, in addition to having founded Tesla and SpaceX, is a strong environmental advocate – he even served as an advisor to the White House and advocated for clean energy, before quitting his role after the announcement of the US pulling out of the Paris Agreement.

4. Costs for utility-scale solar panels have dropped 85 percent since 2009.

With rapidly falling costs and new business models, solar panels are becoming an increasingly financially viable option for average Americans – increased popularity and demand helps to drive down costs as they become more common across the country.

5. The solar industry was responsible for creating one in every 50 jobs added in the US during 2016.

In fact, the US solar industry now employs more than double the number of people that the US coal mining industry does – and that number is growing every year. 

6. The solar industry employed more US military veterans in 2016 than the workforce average – 9 percent compared to the national rate of 7 percent.

The same report from the nonprofit, The Solar Foundation, shows that 67 percent of all jobs in the solar industry do not require a bachelor’s degree, which makes it an especially viable career option for people who have not been able to attend college.

7. The photovoltaic effect – which converts sunlight into electricity – was first observed by physicist Alexandre-Edmond Becquerel in 1839.

In fact, much of the Becquerel family was populated by physicists – Alexandre-Edmond’s father, Antoine Cesar, and his other son, Henri, were both noted in their fields for various discoveries and inventions. However, the photovoltaic phenomenon was not fully articulated until 1873 by engineer, Willoughby Smith.

8. The first practical solar cell was unveiled in 1954 by Bell Laboratories in New Jersey – and converted solar energy at an efficiency of about 6 percent.

Three scientists at Bell Laboratories – Daryl Chapin, Calvin Fuller, and Gerald Pearson – were primarily responsible for engineering the original silicon solar cells. Chapin was originally focused on engineering solar cells made of selenium, but silicon was quickly found to be significantly more efficient.

9. The current record for solar panel efficiency, 26.6 percent, was set in March 2017 by Japanese scientists.

The panel still uses the same principles in the original silicon cell design pioneered by Bell Labs in the 1950s, with a few significant innovations to minimize the space where electrons can’t exist and allowed for the collection of a greater number of light particles from the sun (known as photons).

10. In 2016, an average of 31,000 solar panels was installed every hour worldwide.

By the end of 2016, the Solar Energy Industries Association reported that there were 1.3 million solar panel installations across the US alone.

11. Of all the US states, California ranks first in both the number of solar PV systems installed and total amount of capacity.

Bonus fact: a megawatt is equivalent to 1 million watts, and a gigawatt is equivalent to 1 billion watts. At the end of 2016, California had a solar capacity of nearly 18,300 megawatts, while North Carolina comes in at a distant second with a capacity of roughly 3,000 megawatts.

12. According to the National Renewable Energy Laboratory, Los Angeles and New York City have the “largest potential installed capacity” for solar energy of any US cities.

This is due in large part because of the vast amount of rooftop space in each city that remains unutilized. Specifically, the report estimates that Los Angeles has 9 gigawatts and New York has 8.6 gigawatts of rooftop solar power potential.

13. Cooler temperatures actually make solar panels process sunlight more efficiently than at hotter temperatures.

This is due to the way that the photovoltaic effect works. Normally, electrons at rest on the solar panel (low energy) are excited by photons from the sun (high energy), and the difference between their excited and rest energies is the potential difference that you get from a solar panel (i.e., the size of the electrical current you can generate). However, if the electrons have more energy at rest (meaning your solar panels are already hot), the difference between the rest energy and excited energy you can create is smaller, and the solar panels will produce less energy.

14. According to one estimate, the surface area we would need in order to power the entire globe with solar would only cover approximately the same amount of surface area as Spain.

The entire planet has a surface area of about 197,000,000 square miles, while Spain has just 195,000 square miles – or about 0.09 percent of the total surface. Spreading solar panels across the globe, rather than keeping them condensed in one area, makes it even more feasible.

15.  According to one projection, the cost of solar panels is projected to continue falling at a rate of about 10 percent per year.

The rapid decline of solar costs in recent years now means it’s increasingly becoming financially competitive or cheaper to use than fossil fuels in more and more places around the world.

16. The US Energy Information Administration states that, unlike fossil fuels, solar energy “[does] not produce air pollutants or carbon dioxide”.

The agency also states that “solar energy systems on buildings have minimal impact on the environment”.

17. The first solar-powered car was unveiled in 1955 … but it was only 15 inches long.

Like Chapin’s initial experiments, the solar panels on the car used selenium rather than silicon. Although an adaptation into an actual commercially viable automobile has yet to materialize, advancements happening this century give us reason to believe that solar-powered cars will one day be available in the future.

18. Solar angle affects how much power is generated by a panel.

A panel produces the most electricity when the sun is directly perpendicular to it. Solar panels are often installed at a tilted angle in order to receive the most direct amount of sunlight throughout the day – and some advanced solar panels are even calibrated to turn and follow the sun across the sky.

19. NASA began using solar cells almost immediately after they were invented.

The Vanguard 1 satellite was launched in 1958, and was the first of its kind to use solar cells – and, as a testament to the reliability of solar power, it still orbits the Earth today!

Solar panels are still being used for space equipment.

20. Solar panels were first installed on the White House in 1979 by then-President Jimmy Carter.

President Carter is still a strong advocate for the use of solar energy. In fact, he now uses a solar PV system on his old farm land to harness sunlight, which is capable of supplying more than half of his town’s annual electricity needs.

21. Solar panels don't require moving parts to operate.

This means that it requires much less maintenance than other traditional forms of energy generation, which do require moving parts.


Why Does This All Matter?

Well, the more people that switch to solar, the better – as clean energy increasingly replaces dirty fossil fuels, less and less carbon pollution goes into the atmosphere. Not only that, but the solar industry is booming. It is creating jobs at an extraordinary rate, and as solar energy keeps getting cheaper and cheaper, it becomes accessible to more and more people.

Solar energy is the future, plain and simple.

Here's how you can help get us there: