When Solar Power Plants and Wind Farms Talk to the Grid

A new full power converter for renewables from Finland is all about communication.

Vanguard engineers at The Switch, a world-class Finnish company that specializes in machines that transform energy into electricity, have advanced power conversion by making the communication between a wind turbine or solar power plant and the transmission line to which it is connected more effective.

Climate change, peaking fossil fuels and energy security issues make the better engineering done by The Switch urgent. Just do the math.

Replacing U.S. fossil fuels would, it is estimated, require four million wind turbines (twelve three-megawatt turbines every hour for three decades), or 160 billion square meters of PV or CSP. A recent International Energy Agency plan said that to beat climate change, the world must build, every year between 2010 and 2050, 35 carbon capture and sequestration (CCS) coal plants and 20 CCS-equipped natural gas plants, 30 nuclear plants, 12,000 onshore and 3,600 offshore wind turbines, 45 geothermal facilities, 325 million square meters of PV and 55 solar power plants. That’s a lot of engineering.

The Switch took its name, Jukka-Pekka Mäkinen, President and CEO of the company, said, “from the big change that will take place in how people consume energy and in how it’s produced.” Foreseeing a global switch to distributed renewable energy generation, three Finnish engineering innovators formed the company in 2006 to apply their skills to renewables.

Expertise with advanced drives, generators and motors made The Switch a fit with Europe’s booming wind industry. “Permanent magnet motors have been applied by Kone Elevator Company for fifteen years,” Mäkinen said. Such permanent magnet direct drive transmissions, on a much larger scale than those in elevators, are now the cutting edge in wind turbines. Mäkinen said he has been working with such drives since 1986.

“The penetration of the permanent drive generator will be four times bigger in three years,” Mäkinen said. Adoption of the technology for wind turbines is limited only by the logistics of the drive’s size.

“Our bet was very much technology-driven,” Mäkinen said. The new power converter The Switch is debuting, which Mäkinen said costs in the hundreds of thousands of dollars and weighs on the order of 2.5 tons, is designed to make direct drive technology capable of delivering more output.

“The generator makes the raw power and the power converter matches it to the line and makes it compatible with the requirements of the utilities,” Mäkinen explained. This includes changing the power from a variable frequency direct current (DC) to 50- or 60-Hertz alternating current (AC). The Switch’s new converter, equipped with a new level of information technology, is at least two percent to four percent, and perhaps as much as seven percent, more efficient than those currently in use, according to Mäkinen.

Sensors and measuring capabilities in the full power converter, he said, make it able to communicate both with ongoing conditions in turbine operations and fluctuations in the transmission system. Through enhanced intelligent operations, it can get the turbine to adjust output to “faults in the line” or make adjustments in turbine operations to keep power flowing.

“You could say it’s smarter,” Mäkinen said. With the full power converter, a turbine processes more about its surroundings. “Nobody likes it if the turbine isn’t turning,” he said. “In some cases, by reducing five or ten percent of the power, you may be able to continue running.”

“A wind turbine is a pretty complex operation,” Mäkinen said. “We have a couple of thousand turbines running with our power converters and we have collected all that application information.” The engineers brought that experience, he explained, “and made a new generation product.”

The product has undergone rigorous testing, Mäkinen said. “It’s not like we make a new product just to see how it flies in the marketplace,” he said of the product’s acceptance. “With the combination of the permanent magnet generator and the full power converter, we are saying you can get up to seven percent more power per turbine.” Customers include world-class turbine manufactures such as U.S.-based GE Wind and China’s Xinjiang Goldwind.

A similar kind of conversion is needed to feed electricity from a utility-scale PV installation into the grid, Mäkinen said. The Switch’s technology can serve that need in a way that similarly enhances efficiency.

In both utility-scale solar and wind applications, the challenge is matching output to what is happening in the transmission system. The new full power converter from The Switch is designed to address that challenge.

Though The Switch has not, Mäkinen said, “delved into” concentrating solar power (CSP) plants, he was confident the new full power converter could produce increased outputs, though not as large, in “behind-the-fence solar” PV and CSP applications. “Traditional solar inverters are moving into this arena,” he said. “We are already in this arena.”

“The neatest thing we’ve done,” Mäkinen added in describing what is next for The Switch, “is the fusion drive,” a hybridization of the industry-standard gearbox. “Inside of the gearbox, we put the permanent magnet generator.” Industry insiders say the gearbox is going the way of the stagecoach, ceding to the direct drive permanent magnet transmission. Mäkinen said the fusion drive might give the stagecoach “chrome alloy wheels.”