One of the biggest hurdles for renewable energy is making it more reliable and consistent. With wind power, wind turbines run as long as the wind is blowing at a high enough speed to generate electricity, but when the wind lags, they stop. That intermittence means that areas that are suitable for wind power can't rely on wind power alone.
Today's wind turbines also have a maximum speed at which they can rotate and harness the energy of the wind and convert it to electricity. This cap is there to protect the wind turbines themselves so that they aren't damaged by high winds. This might extend the life of the turbines, but it also results in wasted wind energy, known in the industry as "spillage."
A new technology developed by University of Nebraska-Lincoln electrical engineering doctoral student Jie Cheng solves both of those problems by harnessing the excess wind energy usually wasted as spillage and storing it for use when wind speeds dip, making wind turbines more efficient and consistent.
Cheng's system converts and directs the extra wind energy to an air compression tank, where the energy is stored until wind speeds dip below the maximum capacity. Using a rotary vane machine that is connected between the turbine's gearbox and generator, excess energy is diverted and stored in the air compression tank. When the wind dies down, the tank then kicks in and reverses airflow back to the rotary vane machine to generate electricity.
In a recent study of his prototype, Cheng found that a 250-kW system would produce an additional 3,830 kWh of electricity per week or an additional 16,400 kWh per month based on historical wind data from Springview, Nebraska. That extra electricity is about 18 times the monthly energy use of a typical American household.
The extra electricity would help bring down energy costs and it would help to prevent major dips in electricity generation.
Cheng sees a lot of potential for his design in Nebraska where there are consistently strong winds and large areas of open land for installing wind turbines. He is collaborating with Lincoln Electric System, the American Public Power Association and UNL's NUtech Ventures office to help further develop his technology and market it to the industry.