The turbines will stand 584 feet high when the blade is pointing straight up. The bottom will serve as a water reservoir. Illustration credits: Max Boegl Wind AG

The four wind turbine sites will be connected by a channel that takes the water down to the valley. Image credit: Max Boegl Wind

Wind is a clean, cheap source of renewable energy, but it’s also fickle. You can never be sure whether the wind will blow. But engineers in Europe have now found a way to crack this shortcoming by combining it with hydropower. The big idea here is that the wind will generate electricity when it’s, well, windy, and the water will act as a giant battery that will discharge and modulate output when it stops blowing.The German firm Max Boegl Wind AG approached GE Renewable Energy to collaborate on the first wind farm with an integrated hydropower plant in March. The four-turbine pilot project will be connected to the grid by the end of 2017, and the hydropower plant should be operational by the end of 2018.These won’t be ordinary wind turbines. They will be the world’s tallest, standing 584 feet high when the blade is pointing straight up. The base of the turbines—the bottom 131 feet—will double as a water reservoir holding 1.6 million gallons of water, and the whole turbine will sit in another reservoir holding an additional 9 million gallons.The setup essentially works as a hydro pump station (see image above). When electricity is needed, water flowing downhill from the reservoirs will power the hydro plant. When the energy supply is high, the hydro plant will pump the water back up the hill to the reservoirs and will act as the giant battery. The hydro plant will benefit from this arbitrage, making power when the price is high and using power when the price is low, while complementing the wind farm. The combination of the two power sources (which will work in parallel to each other) will ensure that electricity is always flowing from the plant.For it to work, the wind turbines must sit at the top of a hill, and there must be room in the valley for a man-made lake — in this case 600 feet below the wind farm—that will store the water when it’s not being used by the turbines.The Swabian-Franconian Forest, in Germany, proved the perfect location. Built into the hills will be a hydroelectric plant capable of producing 16 megawatts of power, while the wind farm on its own will produce 13.6 megawatts.The team behind the farms says the innovative design provides a very fast increase in output, allowing the hydro plant to react immediately to fluctuations in the German energy market. “Germans in this area are known as tinkerers and inventors,” says Cliff Harris, general manager for onshore wind in EMEA at GE Renewable Energy. “So the mentality of this technology really fits with the population.”GE is supplying the wind turbines as well as the software, which will make the wind plant more efficient. Software such as the Digital Wind Farm suite already runs on the company’s Predix system, a cloud-based platform for the Industrial Internet. The system collects data from different sources, including the wind turbines, the grid and even weather forecast services and analyzes it in the cloud. The insights help operators predict maintenance needs, optimize production throughout the day and control how much power can flow into the grid at any given time. This is important because too much power could result in a dangerous a surge, and too little power would turn off the lights.The German project is the first of its kind and, if it proves successful, could pave the way for future wind-hydro combinations. Boegl expects to do one or two projects per year in Germany after 2018. (The reservoirs can also saltwater, which means the plants can be built close to the sea.)Because the wind doesn’t always blow and the sun doesn’t always shine, all forms of renewable energy need some kind of backup source to ensure reliability. By using hydropower, the combined plant keeps power flowing without turning to fossil fuels. This innovative plant will also help Germany move toward its goal of generating at least 45 percent of its energy from renewables by 2030.“It’s a bit risky, and it can’t work everywhere,” says Harris of the new combo plant. “But the plant will run for several decades, and we expect the benefits will be felt over that time.”