Wind & Water Power Newsletter Aug/ Sept 2015

In this Issue: Sandia's Wind & Water Power Update for Aug/ Sept

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Sandia’s Wind and Water Power Technologies Program Newsletter highlights key activities, articles on current research projects, latest reports, papers, and events published by Sandia. This monthly newsletter is intended for wind industry partners, stakeholders, universities and potential partners.

This issue contains recent news stories related to both wind and water power in support of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Wind and Water Power Program.

Recent Publications

Richard G. Hills, David C. Maniaci, Jonathan W. Naughton. "V&V Framework". September 2015. 

Wind Energy

Wind Plant Optimization

Large-Eddy Simulation of SWiFT Turbine Array

The total energy produced by a wind farm depends on the complex interaction of many wind turbines operating in proximity with the turbulent atmosphere. Sometimes the unsteady forces associated with wind negatively influence power production, causing damage, and increasing the cost of producing energy associated with wind power. Wakes and the motion of air generated by rotating blades need to be better understood. Predicting wakes and other wind forces could lead to more effective wind turbine designs and farm layouts, thereby reducing the cost of energy, allowing the United States to increase the installed capacity of wind energy.

The Wind Energy Technologies Department at Sandia has collaborated with the Uni­versity of Minnesota to simulate the interaction of multiple wind turbines. By combining the validated, large-eddy simulation code VWiS with Sandia’s HPC capability; this consortium has improved its ability to predict unsteady forces and the electrical power generated by an array of wind turbines. These quantities were found specifically for the Sandia Scaled Wind Farm Technology (SWiFT) facility, aiding the design of new wind turbine blades being manufactured as part of the National Rotor Testbed project for the Department of Energy.

Three specific areas of research were addressed with different simulation cases. First, researchers investigated the persistence of the wake for unique distributions of force along the wind turbine blades. Unique force distributions produced unique wake contours; however turbulence removed any differences beyond 4 rotor diameters downstream. The next simulation investigated the effect of scale on wake persistence and showed that two wind turbines of the same design but different scales will produce different wakes. Finally, the simulations of the experimental SWiFT facility quantified the potential for increased power and force fluctuations of downwind turbines.  The research findings have already influenced the aerodynamic design of new wind turbine blades being considered at Sandia. This research was presented at NAWEA 2015 Symposium.

Xiaolei Yang, Daniel Foti, Christopher L. Kelley, Fotis Sotiropoulos , “Large-Eddy Simulation of SWiFT Turbines Under Different Wind Directions,” North American Wind Energy Academy 2015 Symposium, June 9—11, 2015, Blacksburg, VA.

Chris Kelley, (505) 845-9036.


Figure 1. Velocity contour of a southwest wind for the three SWiFT wind turbines.

Offshore Wind

MOU Agreement with the Technical University of Denmark (DTU) Extended until 2020 for Continued Cooperation in Wind Energy Technology Development

Recently, Sandia and the Technical University of Denmark (DTU) signed a new MOU (Memorandum of Understanding) agreement to continue cooperation on wind energy technologies research and development.  The agreement involves Wind and Water Power technologies programs at Sandia and the Wind Energy Division and Composites & Materials Mechanics Programme in the Materials Research Division, both at the Technical University of Denmark.  The original MOU was executed in 2010 for a period of 5 years.  The current extension, which highlights continued interests and opportunities for cooperation, will be in effect until 2020.  The new agreement was signed by Peter Hauge Madsen, Head of Department at DTU Wind Energy, and by David Corbett, Acting Vice President of Sandia Division 6000.

The MOU agreement calls for general areas of collaboration including but not limited to:

  1. Collaborations between Sandia and DTU staff and students,
  2. Involvement of DTU students in Sandia projects,
  3. Projects requiring sharing of complementary capabilities,
  4. Pursuit of joint funding opportunities,
  5. Involvement of Sandia staff in directing graduate students,
  6. Opportunities for collaborative use of specialized research equipment,
  7. Pursuit of joint ventures, and
  8. Coordination of education and research in areas of common, strategic interest to both organizations.

Sandia and DTU Wind have made meaningful steps over recent years in cooperative and collaborative activities including organization of a joint workshop on Offshore Vertical Axis Wind Turbines (VAWTs) in 2014, DTU participation in Sandia Blade Workshops (2012, 2014), and technical exchanges on a variety of topics of common interest including offshore wind and rotor technology development.  In addition, in coming months, Sandia will travel to Denmark to participate on a PhD committee for a DTU Wind student working on offshore VAWTs (November 2015).  This trip will include discussions regarding current priorities and new opportunities for collaboration between DTU and Sandia under the framework of the MOU agreement.

D. Todd Griffith, (505) 845-2056. 

Water Power

Wave Energy: Device Performance

WEC-Sim Leveraged to Model Floating Offshore Wind Experiments

The University of Minnesota and Sandia National Laboratories have partnered together over the past three years for the DOE funded offshore wind FOA on the high resolution modeling of offshore wind turbines and farms. In 2013, the University of Minnesota performed experimental tests on a floating offshore wind turbine in the Saint Anthony Falls Laboratory wave flume. The 1:100 scale floating offshore wind turbine experimental design was based on the Sandia National Laboratories 13.2 MW wind turbine mounted on a cylindrical barge platform.  The floating offshore wind platform experimental setup is shown in Figure 2, where the platform is restricted to heave and pitch motion only since these are the primary modes of motion.


Figure 2. Floating offshore wind platform experimental test setup, restricted to heave and pitch motion only. 

The motivation behind the experimental testing was to provide a data set for validation of the University of Minnesota's high resolution VWIS code. In support of this project, Sandia National Laboratories provided Boundary Element Method (BEM) results for comparison to the VWIS code, and recently Sandia National Laboratories leveraged the open source WEC-Sim code (developed to simulate Wave Energy Converters in operation waves) to model the floating offshore wind experiments.The WEC-Sim code was used to model the hydrodynamic response of the floating platform, as well as the heave and pitch constraints. Results of these simulations are shown in Figures 3 and 4 and match the experimental data well. Since the BEM solution is a low order model, WEC-Sim is a mid-fidelity code, and VWIS is a high resolution code, these results will demonstrate the comparative accuracy of different fidelity numerical codes in comparison to the experimental data.

Kelley Ruehl, (505) 284-8724.


Figure 3. WEC-Sim Simulation of Offshore Wind Turbine Experiments.


Figure 4. Comparison of WEC-Sim Simulations to Experimental Data and BEM Solution.

PTO-Sim: A Power Performance Module for WEC-Sim

Ratanak So, a PhD student in Electrical and Computer Engineering advised by Dr. Ted Brekken at Oregon State University, worked at Sandia National Laboratories as a Summer 2015 intern. Over the past year, he has been developing PTO-Sim (Power Take-off Simulator), the WEC-Sim module responsible for accurately modeling a WEC’s conversion of mechanical power to electrical power. While the PTO used in the WEC-Sim example is modeled as a simple linear damper, PTO-Sim is capable of modeling many power conversion chains (PCC) such as mechanical drivetrain and hydraulic drivetrain. Therefore, the user can quickly see the effects of different PTO configurations. PTO-Sim is made of native Simulink blocks coupled with WEC-Sim using WEC-Sim’s user-defined PTO blocks, where the WEC-Sim response (relative displacement and velocity for linear motion and angular position and velocity for rotary motion) is the PTO-Sim input. Similarly, the PTO force or torque is the WEC-Sim input.


Figure 5. Schematic of the PTO-Sim hydraulic model.

 On August 21, 2015, PTO-Sim, as part of WEC-Sim, was released as an open source code and is available at PTO-Sim was developed to support WEC-Sim, but it is also compatible with other WEC code that is capable of simulating WECs of arbitrary device geometry subject to operational waves. A wide range of PTO components are currently available but more components are being built and will be added in the near future.

The PTO-Sim project is funded by the U.S. Department of Energy’s Wind and Water Power Technologies Office.

Ratanak So & Kelley Ruehl, (505) 284-8724.


Figure 6. Simulink model of the hydraulic system and WEC-Sim RM3 model with PTO-Sim.

In this Issue