Willett Kempton on offshore wind farms

How do wind turbines generate energy when the wind doesn’t blow? The answer might lie in connecting wind turbines together. Willett Kempton, director of the Center for Carbon-Free Power Integration at the University of Delaware, likes to describe a chain of interconnected offshore wind farms.

Willett Kempton: We’ve solved a lot of the problem of wide fluctuations – from none to full power, none to full power. You don’t see that when you connect wind farms like this.

In a study published in the Proceedings of the National Academy of Sciences in April 2010, Kempton described a chain of 11 offshore wind farms – each made up of 100 wind turbines – along the U.S. East Coast. They’d be connected by a transmission cable buried beneath the ocean, so if one wind farm falls idle, the other wind farms would transmit their excess energy to it. Kempton said this system is ideal for East Coast weather patterns.

Willett Kempton: Storms tend to move up along the coast. So connecting wind farms in a line along the coast tends to give you fairly level power.

Kempton said that although backup energy sources would still be needed on occasion, this system could one day provide the majority of the East Coast’s power.

Willett Kempton: Even just using conventional technology, there’s enough power to run the whole East Coast – all those coastal states, from Massachusetts to North Carolina.

Kempton and his colleagues based their study on 5 years of wind data from meteorological stations along the East Coast. They found that by creating an interconnected system informed by weather patterns, over the 5-year period, the output from all the stations rarely reached either low or full power, and never completely stopped.

Willett Kempton: What was new for us was saying, we’re not just going to build some wind farms and connect them to where people need power, and we’re not going to connect wind farms only because they happen to be owned by the same company. Instead, we’re going to design this to minimize the fluctuations of wind.

Kempton said the idea of transmitting the power via a cable is an alternative to storing the power in a giant battery, which is more expensive. He added that these long underwater cables are already in use – for example, a similar cable connects Tasmania to Australia.

Willett Kempton: Basically, it’s just a big wire with two conductors that gets buried under the ocean, maybe 6 feet down.

In a previous study, Kempton found that tapping into the wind resources off the Atlantic Coast could provide all electricity, including energy for light-duty transportation (cars and light trucks), and building heat from Massachusetts to North Carolina. But the timeline for implementing such a plan could vary, depending on the direction of US energy policy.

Willett Kempton: It depends on how fast we want to develop this economy and how fast we want to get off carbon producing fuels. If we just do it when each power plant wears out… and build wind turbines only when we need a new power plant, then it’s probably a 50-year process.

He added that if the US decided to act quickly to reduce CO2 in order to prevent climate change, the system could be implemented in ten years.