California has a problem: It’s producing more renewable energy than it’s able to use. Solar and wind energy production ramp up in the middle of the day, when electricity demand is low. And because that renewable energy doesn’t have anything to power, it gets wasted.
Folks in the solar industry call the dilemma the “duck curve” because of what the difference between energy supply and demand looks like on a chart when renewables are over-contributing to the mix of power—sort of like a duck. And the duck curve is an issue other states will face as they bring more and more renewables online, PG&E Principal Project Manager Trevor Udwin told Tech Brew.
But excess clean energy doesn’t have to go to waste: It can be distributed to consumers and homes via virtual power plants (VPPs). That extra solar and wind energy can be taken from the grid and put into VPPs to be used at a later time or date—through projects like PG&E’s Seasonal Aggregation of Versatile Energy (SAVE) VPP, which Udwin worked to bring to life—which in turn helps stabilize the amount of energy the grid is taking in and pumping out. And that, Udwin said, transforms the duck curve from looking like mountains and valleys to smaller dips and hills.
“It’s not just about shaving the peak; it’s about filling the trough,” Udwin told Tech Brew.
OK, so what’s a VPP?
A VPP is a network of batteries that pull energy from the grid at specific times based on signals from utilities or homeowners. More broadly, though, a VPP is any type of load management, so a VPP can also be a network of batteries that store renewable energy generated by solar panels and wind turbines and redistribute it to a network of homes, separate from the grid.
Though a single stationary battery can store energy, one battery alone can’t solve the duck-curve issue. Because so much renewable energy is coming into the grid from different locations at a time when demand for power is low, multiple, connected batteries are needed to soak up the excess energy.
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“Different parts of energy transition call for different solutions,” Blake Richetta, the CEO of VPP provider Sonnen, told Tech Brew, “sustainable solutions to handle the intermittency of renewables and the difficulty of electrification.”
And the reason VPPs are called virtual power plants is because they’re a virtual replacement for a power plant: Instead of using an extra power plant, the grid can turn to the virtually networked batteries as a power source. In this way, VPPs replace power plants (and even more importantly, peaker power plants) and other general electrical infrastructure, which the US doesn’t have enough of in an era of increasing electricity demand.
What do VPPs do?
Beyond providing flexibility for where extra energy can go, VPPs also help avoid power outages by balancing the frequency of the grid and preventing electrical abnormalities. In addition to helping ensure the excess renewable energy being produced gets used, VPPs can help balance increasing amounts of renewables being added to the grid and more electric-powered products needing to charge from it—electrical loads that are only going to grow.
“You have…this crazy new erratic load that’s coming out of the electrification of all things—specifically electric vehicles, heat pumps, things like this—that makes the grid even more difficult to manage. You put those things together, there is a wall that we hit,” Richetta said. “When you have a certain amount of renewable energy in the grid and a tremendous increase in load, the grid no longer can manage itself in the way that it has for a really long time.”
That’s why it’s important to use load-shifting products—like VPPs—to “harmonize” the erratic nature of renewable energy with the grid’s needs.
“We’re going through a major energy transition,” Richetta said. “[The way] we can evolve into this kind of renewable, electrified energy system that’s fossil fuel-free is to harness renewable energy and harmonize it with the actual grid’s needs and dispatch it only in a way that serves true value to the grid.”