New Frontiers
Wind Research Center to Launch

Katie Johnson, assistant professor of engineering, collaborates closely with NREL researchers.
Wind energy is the fastest-growing energy source in the world. Worldwide investments of $18 billion recorded in 2006 are expected to expand threefold to $60 billion by 2016. Although wind currently provides less than one percent of electrical power in the U.S., generation capability is plentiful and 20 percent could be supplied by wind without making any major changes to the grid.

Modern wind turbine technology is both sophisticated and effective; the most powerful wind turbines peak at about 6,000 kW, sufficient for about 3,750 average U.S. households. Nevertheless, wind power producers experience their share of headaches. Sitting high atop a steel tower in exposed locations, these self-contained units must deliver power under a wide range of operating conditions. Rain, snow, hail, temperature ranges of over 100 degrees, not to mention constantly shifting winds that in some locations exceed 100 mph, all combine to make turbine design a complex engineering challenge. Not surprisingly, the industry still has plenty of problems to solve.

To support scientific and engineering research into wind power, the Colorado Renewable Energy Collaboratory will launch a new research center focused on wind in spring 2009. The Collaboratory, a partnership between Mines, the National Renewable Energy Laboratory, CU-Boulder and Colorado State University, has already launched two such research centers: the Colorado Center for Biofuels and Biorefining (C2B2), and the Center for Revolutionary Solar Photoconversion (CRSP). The third research arm, the Center for Research and Education in Wind (CREW), establishes a special partnership with two additional Front Range research institutions: the National Center for Atmospheric Research and the National Oceanic and Atmospheric Administration.

“Understanding where wind blows, how often it blows, and how it is likely to arrive at a given site are all important factors in optimizing the design of wind turbines,” says Katie Johnson, assistant professor of engineering and CREW’s site director for Mines. After conversations with representatives from the wind industry, CREW’s Project Management Team identified five thrust areas for research: turbine modeling, electrical systems, turbine testing and certification, atmospheric sciences, and control of wind energy systems. The list isn’t exhaustive and isn’t intended to limit the scope of CREW’s work. “There are many other capabilities; these are just the five primary ones identified in consultation with the wind industry,” said David Hiller, the Collaboratory’s executive director.

While experimental turbines remain critical for research, computational models allow researchers to test new ideas in a virtual reality for a fraction of the cost. In the course of their research, CREW scientists have developed a wide array of models to analyze phenomena such as aerodynamics, acoustics, load prediction, electrical systems, performance of mechanical components, grid interactions, wind farm effects on airflow, and hydrodynamics for offshore wind turbines.

CREW’s research into electrical systems includes three main areas: the conversion of wind into electrical current, delivering power onto the grid, and overarching grid design. One of the key problems wind operators face is uploading power that surges with each gust of wind onto an electrical grid that operates at a constant 60 hertz. To tackle this problem, CREW scientists may consider adaptations to electrical generation systems in the turbine and improvements to the design of transformers.

Turbine testing and certification will be offered by CREW through specialized facilities at NREL. Here blades can be examined for fatigue and strength, a wide range of tests for drive trains and generators are available, and turbines can be set up and field-tested for power quality and acoustics. CREW’s atmospheric science capabilities, supported by NCAR and NOAA, include environmental sensing and measurement technologies that feed real-time data into regional forecasting models. With accurate wind prediction, operators can give utility companies advanced notice of how much power they can supply to the grid, allowing modifications to be made to the rest of the power generation mix. Accurate climate data is also important for determining wind turbine specifications; if you know the maximum strength of the wind in a given location, you know how strong a turbine situated there must be. That said, designing a turbine to withstand the most extreme conditions expected in a given location based on material strength alone is costly, and, according to Johnson, not necessary.

Johnson works on control systems, CREW’s fifth focus area, which enable turbines to adjust to a wide range of conditions. Turbine control systems will, for example, feather turbine blades to reduce wind loads under extreme conditions. Equipped with active control systems, the tower and blades don’t have to be as sturdy and turbines are less costly to produce. These same control systems also increase power generation by optimizing blade angle and torque with changing wind conditions, as demonstrated in a recent field study Johnson conducted with colleagues from CU- Boulder. “The results of our testing surprised even us,” says Johnson. “We expected maybe a one or two percent efficiency increase. We had no idea it would jump by five percent.”

In addition to her work on individual turbine control systems, Johnson is also working on coordinated wind farm controls. The performance of an individual turbine on a wind farm is influenced by its location relative to wind direction and the other turbines: one day it may have unobstructed exposure to the wind, while the next it might be three or four rows back. Rather than incorporate isolated control systems in such cases, a coordinated control system that governs the entire facility is likely to harness greater efficiencies.

Hiller anticipates that by spring 2009 CREW will have an operating agreement in place among a group of private partners and CREW. With commitments from Vestas, Siemens and RES Americas, the center is targeting small and mid-sized companies to achieve a representative cross-section of the industry. With the agreement in place, founding partners and CREW scientists will work together to formulate a set of shared research projects, to be funded by private partners’ membership fees matched dollar for dollar by the state of Colorado.