On Monday, Q-Cells announced it is terminating a long-term supply agreement with the company. Other worst performers included advanced materials producer Rubicon Technology ( RBCN), falling 9.66 percent; energy storage and power delivery system maker Maxwell Technologies ( MXWL), losing 8.09 percent; lithium battery maker China BAK Battery ( CBAK), down 5.17 percent; and developer of advanced energy delivery technology American Superconductor ( AMSC), losing 4.89 percent. QWND -- up 1.89 last week -- includes companies that are primarily manufacturers, developers, distributors, installers, and users of energy derived from wind sources. QWND's 24 pure-play components were evenly split, with 12 seeing gains and 12 losing ground. QWND's best performer for the week was wind turbine gearbox maker Hansen Transmissions Intertnational ( HSN), gaining 9.38 percent. Other top performers included composite materials producer Gurit Holding ( GUR), climbing 5.81 percent; turbine manufacturer Vestas Wind Systems ( VWS), up 5.23 percent; Australia-based wind farm owner Infigen Energy ( IFN), growing 5.21%; and project developer Iberdrola Renovables ( IBR), rising 4.95%. QWND's worst performers were wind farm operator Terna Energy ( TENERGY), down 4.92 percent; American Superconductor ( AMSC), losing 4.89 percent; wind turbine manufacturer Clipper Windpower ( CWP), falling 3.17 percent; wind farm operator Japan Wind Development ( 2766), down 3.06 percent; and carbon fiber maker Zoltek Companies ( ZOLT), declining 2.69 percent. QGRD -- up 2.63 percent last week -- is composed of companies that are primarily involved in the electric grid; electric meters, devices, and networks; energy storage and management; and enabling software used by the smart grid and electric infrastructure sector. Last week, 10 pure play QGRD components saw gains and 7 lost ground. QGRD's best performer was EnerNOC, gaining 12.22 percent. Rounding out the top five performers were power conversion device maker Power-One ( PWER), rising 12 percent; energy demand management company Comverge ( COMV), up 9.11 percent; transformer manufacturer Jinpan International ( JST), climbing 8.17 percent; and developer of energy data systems ESCO Technologies ( ESE), growing 5.91 percent.