The most plentiful energy source sits above our heads every day, and since the invention of the first solar cell in 1883, we’ve been working to harness the sun’s energy.
Today, it’s easy to spot solar farms from a mile away, often looking like a lake in the distance. Spread out through open fields are rows and rows of photovoltaic modules, colloquially called solar panels.
Enel, an international renewable energy company, began development of the Lily Solar and battery storage site in Kaufman County, Texas, in 2020. Today, it operates 421,400 panels on 1,400 acres just outside Scurry, a town of 690 residents about 40 miles southeast of Dallas.
Most of the sprawling site is used for solar arrays, or groups of panels that harness energy from the sun and convert it to useable electricity. The rest of the space is a BESS paddock, or a battery energy storage system.
Jonathon Parras, who has been with Enel for three years and in the renewable energy industry for eight, serves as site lead for Lily and manages a small team of technicians who keep the site running smoothly, pumping power from the sun onto the Texas grid.
The entire site can be run by as few as two people, one for the panels and one for the batteries, but on most days there are anywhere from four to ten technicians that keep an eye on the equipment, scientific readings, grid conditions and cleaning.
“Everybody needs energy, and I feel like if you can source it from something that’s unlimited, that’s the best way to do it and provide for everyone,” Parras said. “It’s a nice clean source and it’s unlimited.”
The Lily team is just part of the state’s growing solar energy workforce of over 11,000. As the industry expands, more solar fields are popping up across Texas.
In a field like Lily’s, solar cells are combined to create solar modules, which, when lined up in rows are called solar arrays. Together, an array the size of Lily creates 180 megawatts of power— enough to keep the lights on and the air conditioning running for 33,000 homes annually.
Inside a solar cell
The workhorses of solar energy are cells stacked with five layers of glass, an anti-reflection material, a metal conduction grid plate, two layers of semiconductors, and a metal conduction plate.
The top glass layer is for protection, keeping out dust, dirt, and bugs, and makes the cells easy to clean.
The anti-reflective material under the glass allows light to pass through, but not reflect on the internal metal parts and back out into the environment. That ensures the panels are collecting as much sunlight as possible.
The metal plates and semiconductors make a sort of electricity sandwich. Metal plates on the top and bottom of the semiconductors allow current to move through them, acting as street signs to direct the current.
But the power generation comes from the semiconductors.
Two semiconductor layers sit on top of one another, one made of silicon and phosphorus, the other of silicon and boron. When light hits the cell, it excites electrons in the phosphorus, known as valence electrons, with enough energy that they break free from their element, and go on the search for an element close by that has fewer electrons, like boron. The free-floating electrons bond to boron in the other semiconductor layer, creating a migration of electrons between layers. When the electrons move, they create energy in the form of a current.
It’s the current that’s harnessed by the metal plates and collected as voltage.
Enel’s arrays are unique because they can collect solar power on both sides of the module.
“They produce from both sides,” Parras said. “They can harness energy from the reflection off of the next row or even from the ground. It will increase the production of those cells.”
Getting power on the grid
The next step is getting the voltage from the cells onto the grid, a process that requires the power to be transformed to the right voltage.
To do this, Parras explained, the electricity from solar panels flows along feeder transmission lines, bringing the power to a conversion unit. There, the power is “cleaned,” meaning DC waves are chopped up to create AC waves, and sent to a transformer box. In the transformer, the power enters on the low side and is “stepped up” to a high side so the voltage matches that of the grid.
All the electricity comes together at the substation where it is prepared to enter the ERCOT system.
At the substation, the electricity goes through batteries, where it could be stored indefinitely.
“[Solar] panels provide the solar power to the substation, which then goes from the substation to the transformers in the [battery storage] yard and then to the power conversion systems and then to the batteries themselves, at which point they are charged,” Parras said. “We have the ability to then discharge those batteries as needed or as necessary back onto the grid.”
From the batteries, electricity flows to a Rayburn Electric substation and onto the grid.
The Lily facility overproduced what was expected internally from Enel during the month of July, meaning it was able to operate as normal and keep all systems online to match demand, Parras said.
Unlike a natural gas plant, solar fields have built in downtime at night. Its staff completes maintenance at night when the sun isn’t shining so the system can stay online during the most productive parts of the day.
By keeping up on maintenance every day, Parras said technicians are able to catch potential issues long before they lead to a bigger problem.
“We get ahead of that stuff. We plan for it,” he said. “Just like the maintenance, we can schedule repairs for nighttime. We can get them in, and it doesn’t affect anything.”
