On a warm and windy day earlier this month, the United Kingdom set a new record. Half of all the country’s energy on June 7 was produced by solar, wind and other renewable sources of electricity. Wind farms alone provided 9.5 gigawatts, accounting for 26.7 percent of all power produced that day.
That record is a reminder that renewables are becoming an increasingly important part of the energy equation. But renewables also come with unique characteristics. People always expect their power to be available at the flip of a switch. While engineers can control how much electricity is coming from conventional plants powered by coal, gas, diesel and nuclear fuel, renewables can be as fickle as the weather. Everyone knows that the sun doesn’t always shine and the wind doesn’t always blow.
At the same time, say, on a windy day, it’s also possible to have too much power flowing through the grid. This overabundance is not a good thing, either. The grid may be a huge system, but it always needs to maintain a delicate balance between supply and demand. Too much or too little power can lead to cascading blackouts.
Ever since the days of Thomas Edison, utilities have been working on ways to balance the grid. In the absence of utility-scale batteries that could store and release megawatts on demand — they remain expensive — the most common balancing tools today are “peakers.” These power plants, which burn either oil or natural gas, can quickly ramp up to full power and pick up the slack when renewables drop off. But even the fastest peakers take several minutes to reach full power, forcing operators to run them at minimum load to keep them ready. Idling, the turbines burn fuel, pump out greenhouse gas emissions and accumulate wear.
But engineers working at GE have now come up with a clever compromise that works kind of like a hybrid car: gas turbine peakers and batteries wrapped in a single, efficient package with sophisticated power-management software. “With a hybrid gas turbine, you don’t have to run the turbine at all,” says Brian Gutknecht, chief marketing officer for GE Power. “If power is called for, batteries can provide immediate power. Meanwhile, you can start up the gas turbine.” By the time the batteries run out of power, the turbine will be up and running — powering the grid and recharging the batteries.
In April, Southern California Edison deployed this solution — the first of its kind in the world — at two sites near Los Angeles. The system is expected to lead to a 60 percent reduction in greenhouse gas emissions and air pollution. The California hybrid combined a 50 megawatt (MW) turbine, capable of reaching full power in about 5 minutes, and a 10 MW battery assembled from lithium-ion cells that lasts up to 30 minutes. “The new system delivered what we’d been looking for: immediate response capability from the peakers,” says Vibhu Kaushik, principal manager of asset management and generation strategy at SCE.
GE is now making this solution available on all of its gas- and coal-fired power plants, some of which produce enough electricity to power the equivalent of millions of households. GE’s power plant on wheels, the TM2500, as well as the world-record-breaking HA gas turbines, are included in the expansion. The company also has plans to include wind turbines, solar PV modules and hydro plants. “The plant in California was kind of a services upgrade, if you will,” Gutknecht says. “But with all of our new plants, we’re going to give a battery option as well.”
GE engineers also developed software that allows the utility to manage, in the most optimal way, how fast the battery discharges and how quickly the turbine needs to ramp up from full stop. “Anybody can put a battery next to a turbine,” Mirko Molinari, general manager for digital grid at Grid Solutions from GE Energy Connections, told GE Reports. “The magic is in integrating the controls.”
Gutknecht is convinced this is only the beginning. As battery costs continue to drop, it will make economic sense to deploy customizable battery systems of various capacities at an ever-widening array of plants. Gutknecht imagines a future where a variety of plants — wind, solar, gas and others — are working together to produce efficient energy while lowering costs. “As an industry,” he says, “I think we’re just scratching the surface in terms of the opportunities to optimize these hybrid solutions.”