Engineers call the technology the Hybrid Electric Gas Turbine, or Hybrid EGT, if you really want to get technical. A topic of keen discussion at this week's CIGRE power conference in Paris, it has helped SCE solve an issue that has vexed the renewable energy industry since its inception — it must yield to Mother Nature’s whims. A covering of clouds or windless afternoon can result in little or no power generation for several hours — something even renewable energy’s most avid fans cannot abide.
That’s why about a decade ago, utilities began installing small natural gas turbines next to wind and solar farms to spring into action when the weather ceases to cooperate. These “peaker” plants helped bring solar and wind power mainstream, but the turbines still took 10 minutes to ramp up — too long for anyone watching a football game or racing to finish a paper on a deadline to be without electricity. To avoid unexpected blackouts, even short ones, utilities left their peakers on at times, burning fossil fuels even when demand was low because reliability concerns were high. SCE, its fellow utilities, and the environment were stuck with a partial solution.
That started to change around 2015 when SCE began throwing batteries into the mix. Working with GE Power’s Grid Solutions and Power Services businesses, SCE paired a 10 MW GE battery system assembled from lithium-ion cells that can supply the electrical grid with power for up to 30 minutes with GE’s LM6000 peaker gas turbine, which can reach 50 MW in about 5 minutes. (The turbine is really a modified jet engine.) Now, if the wind dies down or clouds form, the battery takes over instantly, giving the peaker ample time to get up to speed. When the wind kicks in again, the battery goes off duty and starts recharging so it’s juiced up for the next windless or overcast day.
It’s a system akin to a hybrid car, where the battery charges off the gas engine and then the two alternate so smoothly that the driver never knows which power source is propelling her down the street.
GE engineers also added sophisticated power-management software to optimize how Hybrid EGT shifts from wind to battery to natural gas. The software keeps constant tabs on supply and demand on the power grid. “In an idle period, we will be watching voltage or frequency and responding to deviation as if the turbine were online,” explains Joe Heinzmann, senior product manager of battery hybrid electric gas turbines at GE’s Power Services division. “Then if there’s a need for energy, we immediately respond by discharging the battery and starting up the gas turbine to provide the required energy.” Once the urgent need passes, operators quickly stop the gas turbine, while the battery system remains online and active. As a result, peaker plants connected to the hybrid system are activated half as often they once did, reducing emissions and wear
This elegant system will benefit California’s environmental health. SCE estimates it will use 2 million fewer gallons of water to operate each power site and reduce greenhouse emissions for the lifecycle of its peakers by 60 percent. It’s also paying off handsomely for SCE itself. Not only does using less water and natural gas drive down operational costs, but the type of power Hybrid EGT produces is very much in demand. Spinning reserve — the term used for power that can become available in less than 10 minutes — is currently valued between $5 and $7 per megawatt an hour (MWH), whereas its slower counterpart, known as non-spin reserve, only sells for 10 cents per MWH. Thanks to its new batteries, SCE can easily and cheaply generate spinning reserve for the grid.
As Vibhu Kaushik, director of grid technology and modernization at SCE, explains it, “Renewable and energy storage provide the perfect combination where you can harness renewable energy and match the supply to how the demand is shaped on the grid.” All of that should help shepherd California closer to its goal of renewables supplying half its electricity by 2030. At a total usage of 28 percent now, the state is already comfortably en route to hitting 30 percent by 2020.
No wonder industry experts continue to shower SCE with honors and accolades. However, unlike many other award-winning stars in Los Angeles, the secret to Hybrid EGT is invisibility. After all, electrical power is at its height when no one even notices it’s there.