Design and testing of a medium-speed 250 kW Brushless DFIG

This paper presents the design and testing of a 250 kW medium-speed Brushless Doubly-Fed Generator (Brushless DFIG), and its associated power electronics and control systems. The experimental tests confirm the design, and show the system's steady-state and dynamic performance. The medium-speed Brushless DFIG in combination with a simplified twostage gearbox promises a low-cost low-maintenance and reliable drive train for wind turbine applications.

Performance analysis and testing of a 250 kW medium-speed brushless doubly-fed induction generator

This study presents the performance analysis and testing of a 250 kW medium-speed brushless doubly-fed induction generator (DFIG), and its associated power electronics and control systems. The experimental tests confirm the design, and showthe system's steady-state and dynamic performance and grid low-voltage ride- through capability. The medium-speed brushless DFIG in combination with a simplified two-stage gearbox promises a low-cost low-maintenance and reliable drivetrain for wind turbine applications. © The Institution of Engineering and Technology 2013.

The front-end of eco-innovation for eco-innovative small and medium sized companies

This paper studies the Front End of Eco-Innovation (FEEI), the initial phase of the eco-innovation process. Incorporating environmental concerns at the front-end of innovation is important, as product parameters are still flexible. This paper investigates the FEEI for 42 small and medium sized eco-innovators in the Netherlands by using a survey. The results show that SMEs embrace informal, systematic, and open innovation approaches at the FEEI. Teams appear to be multidisciplinary, and creativity and environmental knowledge are essential. Experimentation played a significant role at the FEEI. The paper concludes with recommendations for future research and implications for managers. © 2013 Elsevier B.V.

Porous boron-doped diamond/carbon nanotube electrodes.

Nanostructuring boron-doped diamond (BDD) films increases their sensitivity and performance when used as electrodes in electrochemical environments. We have developed a method to produce such nanostructured, porous electrodes by depositing BDD thin film onto a densely packed "forest" of vertically aligned multiwalled carbon nanotubes (CNTs). The CNTs had previously been exposed to a suspension of nanodiamond in methanol causing them to clump together into "teepee" or "honeycomb" structures. These nanostructured CNT/BDD composite electrodes have been extensively characterized by scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Not only do these electrodes possess the excellent, well-known characteristics associated with BDD (large potential window, chemical inertness, low background levels), but also they have electroactive areas and double-layer capacitance values ∼450 times greater than those for the equivalent flat BDD electrodes.

Design and performance analysis of a 6 MW medium-speed Brushless DFIG

The paper presents the design and performance analysis of a 6 MW medium-speed Brushless Doubly-Fed Induction Generation (Brushless DFIG) for a wind turbine drivetrain. Two machines with different frame sizes have been designed to show the flexibility of the design procedure. The mediumspeed Brushless DFIG in combination with a two stage gearbox offers a low-cost, low-maintenance and reliable drivetrain for wind turbine applications.

Enhancing the carbonation of MgO cement porous blocks through improved curing conditions

The use of reactive magnesia (MgO) as the binder in porous blocks demonstrated significant advantages due to its low production temperatures and ability to carbonate, leading to significant strengths. This paper investigates the enhancement of the carbonation process through different curing conditions: water to cement ratio (0.6-0.9), CO2 concentration (5-20%), curing duration (1-7 days), relative humidity (55-98%), and wet/dry cycling frequency (every 0-3 days), improving the carbonation potential through increased amounts of CO2 absorbed and enhanced mechanical performance. UCS results were supported with SEM, XRD, and HCl acid digestion analyses. The results show that CO2 concentrations as low as 5% can produce the required strengths after only 1 day. Drier mixes perform better in shorter curing durations, whereas larger w/c ratios are needed for continuous carbonation. Mixes subjected to 78% RH outperformed all the others, also highlighting the benefits of incorporating wet/dry cycling to induce carbonation. © 2014 Elsevier Ltd.