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Can Wind and Solar Energy Power Traffic Lights?

A University of Nebraska-Lincoln research program is trying to build a smart grid of renewable energy capable of reliably powering traffic signals.

A research team at the University of Nebraska-Lincoln is preparing to begin the second stage of a three-year green energy pilot project that’s researching the viability of integrating wind and solar power into a municipal power grid to power traffic and street lights. 

Funded by a $1 million grant from the U.S. Department of Transportation, the project is called Energy Plus Roadways. Those involved hope to develop a smart grid system for roadway infrastructure that will prove practical for widespread, large-scale use.

The end goal is negative energy consumption, said Anuj Sharma, a UNL assistant professor of civil engineering. In other words, more energy would be produced by the municipal grid than is consumed. Ideally a smart grid system would generate enough renewable energy to power all the traffic and street lights in the city and still have some left over to sell back to the power companies.

“That’s where the name Energy Plus Roadways comes from,” Sharma said.

The second phase of the project, scheduled to begin in May, involves developing the electronic control system that would allow a network of wind and solar power generators to intelligently distribute electricity where it’s needed, said Jerry Hudgins, the project’s leader and also a professor of electrical engineering at UNL. The team will run simulations to test how such a system could adapt to power grids of different sizes and layouts.

The first phase of the project, which began last summer, involved monitoring a single 30-foot Bergey XL 1.0 wind turbine connected to a traffic light at the intersection of 84th Street and Nebraska Highway 2 in Lincoln. The traffic light receives its power from a battery that’s charged by the wind turbine, but the traffic light’s power supply is still connected to the main power grid as a contingency. Any excess power generated can be sold back to the electric company for about four cents per kilowatt hour.

Hudgins predicts this type of system will become increasingly attractive as the price of energy increases and green technology improves. “Initially, it’s going to add some reliability to the system,” Hudgins said. “It’s also going to have some cost savings increase over time.”

UNL assistant professor of electrical engineering Wei Qiao will develop the control system system that will allow the grid to make decisions on power distribution and usage.

A solar panel in a shady area or a turbine that receives little wind can use the control system to borrow the power it needs from another generator in a sunny or windy area that’s experiencing an energy surplus. The system is designed to run without the help of a human operator and uses existing power lines to transmit the power from one area of the grid to another.

Each power station will be able to transition between three operating modes. In one operating mode, the power station will rely entirely on power from the main grid. This might occur when it’s cloudy or not windy for an extended period. The second operating mode will allow a station to draw power exclusively from solar and wind power on the grid. The third mode allows a working generator to isolate itself from the rest of the grid in case of a problem nearby, minimizing the scope of the problem.

In the third stage of the project, scheduled to begin in summer 2012, the team will implement a micro-grid consisting of up to eight power generators, eight traffic light poles and two intersections.

Those working on the pilot have calculated that an effective smart grid for traffic lights and other transportation infrastructure would ultimately save cities money on power costs, increase utility uptime, reduce pollution and reduce reliance on nonrenewable energy. If all 300,000 roadway intersections in the U.S. that have traffic signals were powered by renewable energy on a smart grid, nearly $50 million would be saved each year, according to University of Nebraska-Lincoln researchers.

Lauren Katims previously served as a staff writer and contributing writer for Government Technology magazine.
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