It all started with Albert Einstein.
In the late 19th century, scientists had observed that certain metals, when exposed to bright light, became electrically charged. Why this happened was a mystery until 1905, Einstein's "Miracle Year." At the same time he was figuring out the theory of relativity, he discovered that light was made of distinct energy packets called photons. When a photon hits an atom of silicon, it dislodges an electron, and when electrons move, we call it electricity.
Einstein's 1905 discoveries reshaped the world. "General relativity" opened up the past and future of the universe and led to indispensable modern innovations, such as GPS. Mass-energy equivalence, the famous E=MC ² equation, led to the atomic bomb, which would threaten the very existence of civilization. But in 1922, it was the photovoltaic effect that won Einstein his Nobel Prize. And it is this idea that might just save civilization.
Behind his Germantown home, Brian Siler has a shed. "It's way back in the yard," he says. "It's where the lawn mower and all that stuff is. I just wanted to be able to go out there at night and flip on the light. I don't need a huge amount of power." To electrify the shed, he says, "We'd have had to dig up the yard, bury a cable, and the circuit box."
So Siler decided to try solar power. "I'm not an electrical engineer. I've had no training," the software consultant says. "A large part of my childhood was going to Radio Shack and picking up some stuff and then coming back to the house and learning how to use it. I like to tinker."
Siler scoured YouTube for ideas and then turned to Amazon to buy the components: a solar cell to convert sunlight to direct current (DC), a charge controller to direct the power, a battery to store the trickle of electricity, and an inverter to convert the DC into the alternating current (AC) that powers the shed's fluorescent lights.
After a sunny day, the lights in Siler's solar shed will shine for about three hours on battery power. He can also use the energy to run power tools. The old car stereo he hooked up to the system will play "forever," he says.
The total cost of the system was less than $200. "There are a lot of people on YouTube who are into solar power, hooking up stuff to it," he says. "You're not like Elon Musk, but you're still building something innovative and kind of cool."
Globally, March 2016 was the hottest month since modern meteorological record-keeping began in 1850. It was the 11th straight month of record-shattering heat, part of a pattern of accelerating global warming that stretches back to the dawn of the Industrial Revolution. Earth has been this hot in the distant past, but not in the 200,000 years modern humans have been here.
The culprit is carbon. Humanity evolved in a world where carbon was in balance: The amount released from natural sources was roughly equal to the amount consumed by plants and absorbed into the oceans. But power-hungry humanity is burning fossil fuels at an increasing rate: oil for transportation, coal and natural gas for electricity. The primary byproduct of these fuels is carbon dioxide (CO2), which is released into the atmosphere from smokestacks and tailpipes. And so, the carbon cycle is thrown out of balance, and, because CO2 traps heat more efficiently than the nitrogen and oxygen that make up most of our air, the world grows warmer.
In 2011, the last year for which we have reliable numbers, about 9.4 billion metric tons of carbon were added to the atmospheric balance, an increase of 3.4 percent over 2010. In 2015, U.S. energy generation released 1.9 billion metric tons of carbon — 71 percent from burning coal and 28 percent from burning natural gas.
Scientists say the consequences of unchecked climate change will be Biblical in scope. Rising sea levels will drown coastal cities like Miami and New Orleans. Drought-induced crop failures will starve billions. If we want to avert catastrophe, we must de-carbonize our energy generation.
"We as a church had decided that one of our focus ministries was to become as green as we could be," says Julia Hicks, director of mission for First Congregational Church. "This goes along with food justice and peace work — all of this is in vain if we don't have an Earth to live on. As a spiritual journey, we believe that the Earth was created by God, and it's our duty to care for it."
About five years ago, Hicks and First Congo's pastor, Rev. Cheryl Cornish, saw an ad for LightWave Solar. "They were working with TVA [Tennesseee Valley Authority] on opportunities to purchase solar panels," Hicks says. "That's a whole new way of going green. It's not just about using less energy, but about finding ways to create new, clean energy.
After much soul searching, the church decided to install solar panels on their building's roof. "The hardest part is that it was expensive to invest in solar energy at that point, because it was not widely done," Hicks says.
Residential and commercial users who install solar can qualify for a federal tax break equal to 30 percent of the cost of the equipment, but as a church, First Congo doesn't pay taxes. They did qualify for a pilot program in which TVA and MLGW would buy the excess energy produced by the solar panels at a premium over the prevailing market rate. "For the amount we were able to do, it only pays back about $125 a month. On bills that range between $6,000 and $8,000, that's a drop in the bucket."
The panels are expected to last for 40 years, and at the current rate, it will take approximately 20 years for First Congo to pay off the $30,000 they invested, leaving 20 years of pay-back for the church in the form of lowered electric bills. But Hicks says the economics are not the point of the project. "It says, do what you can do. Don't say no just because you can't pay your bill with it, or that this is an awful lot of money. The point is the point. Solar energy is the future, if we're going to have a future. And it's the faithful thing to do."
It's Raining Soup
Electrical engineer Steve Johnson had long been fascinated by solar power. "In 2006 I decided to jump in with both feet," says the founder of LightWave Solar. "It started growing right about that time. There wasn't any solar to speak of in Tennessee, so we've just grown along with it."
Over the last decade, Johnson has seen Tennesseans' attitudes evolve. "Early on, people were very skeptical that it really worked. Some people thought it was a gimmick. That's been overcome, because now there's a couple of thousand systems in Tennessee producing electricity every day."
Johnson says the upfront expense of solar power is the biggest hurdle he has to overcome in people's minds. "The thing about solar is that you don't have fuel costs. Those costs add up when you have to burn fuel every minute of every day. If you've ever bought a cheap inkjet printer, you go "Wow, how did they make 'em so cheap?' Then you go to buy the color ink cartridge, and it's almost as much as the printer."
Solar fuel, in the form of photons, is delivered for free every day by the sun, which delivers more energy to the earth in an hour than humanity uses in a year. As science fiction writer Robert A Heinlein said, "It's raining soup. Grab a bucket."
Finding the right bucket has been a century-long project. When Bell Labs demonstrated the first practical silicon solar cell in 1954, it converted about six percent of the light energy that struck it into electricity. "Panels today are between 15 percent and 20 percent efficient," Johnson says. "It's about the same as a car, if you look at the power that goes to the wheels. The average system we're doing these days is around $20,000 to $25,000."
During his decade of solar installation, Johnson has seen the price of the solar bucket plunge. "Three or four years ago, there was a big drop in panel prices. The price is still coming down, not as rapidly, but it's still coming down. Panels cost about 20 percent of what they did when we started."
"Currently in Shelby County, we have just over four megawatts [of solar] divided up between 82 generation sites, says MLGW's Becky Williamson. "The largest one is at the Agricenter, and that represents about a quarter of the total."
Commuters passing through Shelby Farms on Walnut Grove can easily see the Agricenter's 5.5 acres of gleaming solar panels. "The Agricenter has a half-billion-dollar impact on this community. We directly or indirectly support 2,500 jobs. People don't realize the importance of Agricenter," president John Charles Wilson says. "They don't realize the kind of research we're doing here, and the more than 30 different companies we're working with."
LightWave Solar began construction on the $4.5 million array, which was financed by Nashville solar company Silicon Ranch, in January, 2012. "Initially, back in 2008-2010, TVA had a premium purchase rate as a subsidy to spur economic development and support this new technology in the region," says Silicon Ranch's Matt Brown, who is also secretary of the industry group Tennessee Solar Energy Industries Association.
"Costs were significantly higher for a residence or small business or a church to install solar on their rooftops at that time," Brown says. "Costs have continued to come down in the installation world — and they've come down at least threefold in the last few years — so TVA has aligned what they pay for these new participants to the costs."
Brown credits the TVA and federal incentives for kicking off solar's explosive growth. "I talk about the free market, but I acknowledge the benefit the federal tax credit has had on this industry. It's done exactly what it was intended to do, which was to inspire the economic engine that [solar] has become," he says. "That created enough demand, and the simple supply-and-demand curve drove the price down. It has really helped make solar much more cost-effective in a much more accelerated time frame than a lot of the people even inside the industry expected."
When the Agricenter's Wilson saw how successful the programs were, he decided to build a 56-panel solar array of his own. "I live on a farm, so I had the acreage to do it. ... I haven't paid a utility bill since then. In fact, I think they owe me some money. But I had to put all of the cost up front, so I have about $60,000 in the two sets of panels. With the economy like it is and interest rates like they are, I started looking at it from a standpoint of, I'm ready to retire, and I wouldn't have a utility bill to pay. So I invested the money in the solar panels, which should pay itself back in about six years."
One of the largest solar installations in Tennessee sits beside I-40 in Haywood County. "The West Tennessee Solar Farm was funded through the Department of Energy's State Energy Program as part of the American Recovery and Reinvestment Act of 2009," says Stacey Patterson, University of Tennessee associate vice president for research. "Those funds were specifically requested by the state to fund two projects. One was the West Tennessee Solar Farm. The other was the Tennessee Solar Institute, which gave out grants to Tennessee for-profit and not-for-profit companies for the installation of solar across the state. The West Tennessee Solar Farm ended up as a five-megawatt, utility-scale array that's all in one place, and through the Tennessee Solar Institute, there was another eight megawatts of solar that was installed across the state — we consider that distributed solar — for commercial entities to help their businesses in Tennessee."
The two parallel projects define one of the great debates in the solar industry: distributed vs. centralized production. Is it better to follow the traditional utility model of giant power plants feeding the grid, or should every home and business have panels on the roof to produce power where it's needed?
"It's very efficient to generate power at a site," says LightWave Solar's Johnson, who has a roof full of solar panels on both his home and business. "I've got a computer on and some lights in my office, and we're generating power. It's cloudy here right now, so everything we're generating will be sucked up by our business, but it doesn't have to go across miles of distribution line and transmission line and substations. To that extent, this amount of power is taking that load off the grid, which is also good for our infrastructure. The less load on the grid, the longer the grid will last."
Patterson says the problem of line loss, familiar to all utilities, came into the play at the West Tennessee Solar Farm. "The one thing this particular site had against it was that it was far from a substation where we could actually interconnect with TVA and the grid."
Nevertheless, in the four years since its 21,000 panels were connected to the TVA system, the West Tennessee Solar Farm has consistently met or exceeded expectations. And since solar plants have no moving parts, the maintenance costs have been a fraction of what you would expect from a coal or natural gas plant of a similar size.
The distributed generation portion of the experiment was even more successful. "The demand for those dollars far exceeded our expectations," Patterson says.
The $11.5 million put into the program leveraged $27.1 million from private companies, paying for more than 200 installations. "Everyone we worked with was really thrilled with the program," Patterson says. "When we ran out of money, we still had a big demand."
Patterson says in her mind, the distributed versus centralized debate is settled. "I don't think it's an either/or kind of thing. It's an all-of-the-above."
In 2015, 7,286 megawatts of solar power was installed in the United States, a jump of more than 1,000 megawatts over 2014. The booming industry still faces significant headwinds. Natural gas prices have plummeted in recent years, driven largely by a new technology called hydraulic fracturing, or fracking, which allows increased domestic production.
"The supplies are much larger than we thought some years ago," says Brenda Etheridge Brickhouse, vice president of environment for TVA. "If you think about the solar megawatts competing with the megawatts on the grid, which are comprised of a lot of different things, those prices on the grid are lower because gas prices are currently so low."
That's good news for carbon dioxide emissions, as natural gas releases 50-60 percent less CO2 than coal, when burned in a state-of-the-art, combined-cycle turbine plant, such as the one that is under construction in Memphis to replace the coal-burning Allen Fossil Plant. But that's not the whole story. Natural gas is comprised largely of methane, which is roughly 30 times more efficient at trapping heat in the atmosphere than CO2. If the natural gas distribution system is too leaky, the climate-change benefits disappear.
The other problem solar is facing is the most obvious one: The sun doesn't always shine. On cloudy days, solar plants produce less electricity; at night, they produce none. Siler's backyard solar shed has a battery to store the electricity produced in the daytime for use at night, but the electrical grid has no such storage capacity. Conventional batteries do not scale efficiently enough to store sufficient energy to power the grid overnight. Since wind, the other major renewable power source, also faces the same intermittency problem as solar, a race is on to improve batteries and develop new storage technologies. The outcome of that race could determine the future of human civilization.
Room For Optimism
A preliminary TVA study indicated that a solar plant big enough to replace the coal burning Allen Fossil Plant would cover an area roughly the size of Bartlett. That is not as daunting as it sounds, given that there are plenty of spaces inside the city where panels could be installed with a minimum of disruption. MLGW's Williamson notes that the second-largest solar array in Memphis is "on the Memphis Bioworks parking garage on Union, which is almost as big as the Agricenter."
And there is plenty more room for solar build-out, says LightWave Solar's Johnson. "We've got a lot of black asphalt parking lots that would be nice to have shaded in the summer, with solar panels producing electricity at the same time."
But TVA, tasked with supplying power to 9,000,000 people, many of whom are among America's poorest, could not afford to wait for the outcome of the battery race. Natural gas is the current fuel of choice as the utility retires its fleet of coal-burning plants. "50 percent of our power supply will be carbon-free by 2020," Brickhouse says.
Conservation efforts are also bearing fruit. "GDP and economic development used to be perfectly correlated to electricity use," Brickhouse says. "That's changing. We're decarbonizing the electric system, but energy efficiency is a big part of it. We're seeing energy efficiency really come to be material in that space."
As MLGW's Williamson says, "The greenest power is the power you don't use."
For solar industry observers, the future is brighter than ever. "[TVA] should recognize the benefits of solar," LightWave's Johnson says. "They don't have the risk of nuclear installations. It's not dirty like coal, and you're not captive to fuel prices. Right now, natural gas is down, but it's going to come back around once everybody is hooked on it. It's fuel. These are all different forms of risks that other forms of power have that solar doesn't have."
TVA is definitely warming to the logic of solar. This week, the utility announced that it is partnering with the Navy on a new 53-megawatt solar project in Millington, which will be the largest single installation in the state.
"There's not a one-size-fits-all solution," UT's Patterson says. "That's the approach that we've taken as we support research in these areas. It needs to be a situation where you're not looking to replace everything with solar, but you could replace some subset with solar. But we do need to have more energy come from renewable sources. That I'm sure of."