When the sun stops shining and the winds don’t blow, how do you store energy?
True confession: as a kid, I was enthralled with what would one day become known as off the grid / green / renewable energy. (Also true, I was a bit of a nerdy kid.)
When most kids spent their money on hand-held video games like Coleco’s Electronic Quarterback, I went to electronic surplus and science stores, picking up kits detailing how to construct a house into a hill that stayed cool in the summer, warm in the winter, and used little to no electricity.
The house never got built, but the fascination with sustainable, free energy remained.
Winning a science fair project at one point—I can’t remember what for—my prize was a solar-powered transistor radio. It got only AM signals, and since there was no speaker, you had to listen through a single earphone. It wasn’t fancy, but the radio, with its small round solar panel, served as a symbol of what was possible.
Typically for the times, my childhood radio’s greatest asset, its ability to use solar power, was hampered by two things. First, it needed direct sunlight to work. The moment the sun disappeared behind the clouds, the music faded too. Second, there was no rechargeable battery to store power. No sun, no fun.
As with geothermal, hydro-electric, wind, and other clean sources of energy, utilization of solar power keeps improving. Throughout history, the sun’s rays have been harnessed for purposes good and bad. It’s believed that in the 7th century B.C., mankind learned to start fires using early magnifying glasses. Centuries later, Greeks and Romans created ‘burning mirrors’ which lighted torches used in religious rituals.
One of the most unusual and destructive uses of sunlight is attributed to preeminent Greek mathematician and inventor Archimedes (287-212 B.C.). Known today to students for his works in arithmetic, mechanics, and plane and solid geometry, he’s said to have devised one of the nastiest—and most creative—ways to use solar power. According to legend, before the siege of Syracuse, Archimedes fashioned an enormous round mirror from glass or bronze, surrounded by an array of smaller mirrors. Known as the Archimedes Death Ray, it directed and concentrated rays of the sun and set a Roman fleet ablaze around 213 B.C.
For decades, solar and wind power faced hurdles—and frequently, mockery—over two issues. First, what good is solar or wind when it is cloudy or windless, and second, how do you contain and preserve the energy generated on those good days when the sun beams and the wind blows? The solution arrived in 1954, when Bell Telephone Laboratories released the Bell System Solar Battery.
An early Bell Telephone promotion was honest about the battery and its limitations.
“There is still much to be done before the batteries’ possibilities, in telephony and for other uses, are fully developed,” said the ad. “But a good and pioneering start has been made. The progress so far is like the opening of a door through which we can glimpse exciting new things for the future. Great benefits for telephone users and for all mankind may come from this forward step in putting the energy of the sun to practical use.”
A few years before the creation of the world’s first solar battery, it was discovered that free electrons were produced when sunlight struck wafers of silicon. Further experiments showed that these free electrons could be transformed into electrical current in the first practical silicon solar cells.
Over a century earlier, others had been experimenting with primitive solar cells, including French physicist Alexandre-Edmond Becquerel in 1839, English engineer Willoughby Smith in 1873, and American inventor Charles Fritts who, in 1883, created the first selenium solar cells.
As pioneering as these innovations were, Fritts’ solar cells were only one percent efficient at converting sunlight to electricity. Decades later, even the Bell solar battery was able to convert only six percent of sunlight into useful energy.
For years, scientists were challenged with making solar cells more efficient and batteries longer-lasting, lighter, and less costly. Researchers and physicists created varieties of batteries including lead-acid, alkaline, and nickel-metal hydride. Also known as ‘wet cell,’ lead-acid batteries were one of the first used for solar energy storage—and are still the most common—because they have a low cost per amp-hour.
Although technology keeps improving, lead-acid batteries require maintenance including cleaning, water, and equalizing, and must be carefully handled. Carelessness can cause explosions, and the electrolyte, being an acid, can harm people, animals, and the environment.
The storage of energy derived from the sun and wind keeps improving, and batteries are a big piece of the puzzle. Although inventor and entrepreneur Elon Musk is best known today for Tesla electric vehicles, advanced rockets and spacecraft, his team at Tesla, Inc. created the ground-breaking Powerwall storage-battery system.
Before the 2015 release of Powerwall, engineers at Tesla’s Giga Nevada (a facility dedicated to manufacturing lithium-ion batteries) were experimenting with other energy storage batteries, including the Tesla Powerpack for industrial customers. Intended for business use and for smaller power-utility projects, the Powerpack was first installed a decade ago. Never one to limit its market reach, Musk and his company later pioneered the Tesla Megapack, capable of storing up to three megawatt-hours (MWh) of electricity for the grid.
Although these devices were developed to meet different needs, the intention behind all three was the same: to store energy generated from solar power, wind, and even time-of-use (TOU) electricity from cheaper, off-peak hours, by means of rechargeable lithium-ion batteries.
For home users, the Powerwall also serves to provide back-up electricity during storms and other events that might bring down utilities. Charged by solar energy during the day, the Powerwall can also pull extra power from the utility grid as needed. Energy accumulated during the day is stored, and then used at night for clean, renewable energy.
Inspiring many imitators since its 2015 release, the Tesla Powerwall may comprise up to 10 units, including a combination of older versions and the Powerwall+.
With a worldwide push to reduce carbon emissions and fossil fuel use to a lower, defined level by 2030, and to each Net Zero emissions by 2050, renewable energy including solar and wind will play an even bigger role in meeting future power needs for everything from household appliances to electric vehicles.
Massive solar farms, such as those in Texas—today a leader in America’s solar photovoltaic (PV) power generation—and an increase in onshore and offshore wind projects globally will see more of our energy requirements met by clean, renewable sources.
One recent project, the Florida Power and Light Company’s FPL Manatee Energy Storage Center is the world’s biggest solar-powered battery storage facility. The project, in Juno Beach, consists of 132 huge battery storage containers, each weighing about 38 tons (34,473 kg). With an output of 409 MW and 900 MWh of capacity, the Center can power the equivalent of 329,000 homes for over two hours, “and enable customers to enjoy the benefits of solar even when the sun is not shining.”
To be sure, renewable energy storage has come a long way since the Bell System Solar Battery of the 1950s and will be vital in powering the future of our planet.
