Active Power Controls from Wind Power: Bridging the Gaps

This paper details a comprehensive study undertaken by the National Renewable Energy Laboratory, Electric Power Research Institute, and the University of Colorado to understand how the contribution of wind power providing active power control (APC) can benefit the total power system economics, increase revenue streams, improve the reliability and security of the power system, and provide superior and efficient response while reducing any structural and loading impacts that may reduce the life of the wind turbine or its components. The study includes power system simulations, control simulations, and actual field tests using turbines at NREL's National Wind Technology Center (NWTC). The study focuses on synthetic inertial control, primary frequency control, and automatic generation control, and analyzes timeframes ranging from milliseconds to minutes to the lifetime of wind turbines, locational scope ranging from components of turbines to large wind plants to entire synchronous interconnections, and additional topics ranging from economics to power system engineering to control design

The effects of physiological age on bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) have great potential in tissue engineering as they can be easily isolated, differentiated into several lineages (cartilage, bone, fat), and allogeneically transplanted without immune response. For developing therapies to be clinically translated, it is imperative to understand how donor characteristics, such as age, affect the efficacy of MSC- based treatments. The overall aim of this study was to characterize age-related changes in MSCs from bone marrow using a murine model. First, the conditions for isolation and in vitro expansion were optimized for bone marrow- derived MSCs; MSCs were isolated from C57Bl/6 mice of varying age (three-week, two-month, six-month, ten-month, and thirteen-month old). Second, donor age-dependent changes in expansion ability were determined by investigating the population doubling time and colony- forming capability of MSCs from various age groups. Cell populations from older mice proliferated more quickly and produced more colonies than their younger counterparts. Finally, age-related changes in MSC functionality and differentiation potential were investigated. Migration rate, antioxidant levels, and cytoskeletal dynamics of each population were determined. It was found that the older populations had faster migration and more dynamic cytoskeletons, while the younger cells had higher antioxidant activity. The cells were also subjected to chondrogenic, osteogenic, and adipogenic assays. The intermediate-aged cells consistently underwent more adipogenesis, while osteogenesis increased until a peak age then declined, and chondrogenesis was not affected by ag