David MacPhee

Recent Advances in Rotor Design of Vertical Axis Wind Turbines

The following work represents the most recent advances in design and testing of vertical axis wind turbines (VAWT) rotors. VAWTs have received much attention as of late due to proposed advantages in small scale and off grid wind power generation. Thus, many recent works have surfaced involving analysis, design and optimization of VAWT rotors in order to more efficiently convert wind energy to electricity or other readily usable means. This paper is a collection of most of the recent literature works involving VAWT rotor design and testing, the majority of which published after 2005. We discuss research in the designing of various lift based rotors as well as some drag based rotors, hybrids, and various others. The recent work in this area suggests VAWT capacity could dramatically increase in the near future, and play a vital role in obtaining cleaner, more sustainable energy when global energy demand is increasing at an unprecedented rate. HIGHLIGHTS A review of various works involving rotor design and testing of both lift and drag Vertical Axis Wind Turbines (VAWTs) is presented; Benefits of vertical axis wind turbines in small scale and off grid wind power generation is summarized; Much of the recent work, published after 2005, has been directed towards analyzing, designing, and optimizing rotor shapes. The body of this recent work suggests that research on VAWT rotor design continues to flourish and could make VAWTs a viable competitor to more traditional Horizontal Axis Wind Turbines (HAWTs) worldwide.

A flexible turbine blade for passive blade pitch control in wind turbines

We present a flexible wind turbine blade that effectively pitches itself according to variable wind loading. In contrast to rigid turbine blades, where active controls are often required to pitch blades, the flexible or morphing blade adjusts its geometry passively, eliminating the need for costly electromechanical systems. We analyze the airfoil using a robust and accurate fluid-structure interaction routine, and introduce two morphing scenarios: one where rigid and flexible blade are identical when unloaded, and one where they are identical at the stall angle. We choose a single Reynolds number and a flexible airfoil material for a case study, and simulate over a range of attack angles, noting the lift and drag coefficients as well as the attack angle change through passive pitching of the flexible airfoil. It was found that the flexible airfoil can delay stall as well as significantly increase lift/drag ratios compared to the rigid blade. In addition, negligible increases in drag and large increases in lift were realized. This suggests that flexibility can be used as a design parameter for wind turbine blades, and would likely increase the operational range and/or part- or over-load efficiencies significantly.

Integrating wind and wave energy conversion

This paper presents a scenario where wind and wave energy conversion techniques are collocated, enhancing per unit energy cost. Wave energy is one of the largest renewable resources in the world, but is largely untapped. By capitalizing on the already proven structural components of offshore wind conversion systems, efficient wave turbines could be implemented for lower total cost, and lower per unit energy cost, than if the two systems were separate. In this paper, we propose further integration of wave energy conversion with off-shore wind energy. The benefits of this synergy are illustrated based on the spatially overlapping two resources — wind and wave.

Performance Investigation of a Small Horizontal Axis Wind Turbine Equipped With Flexible Blades

Wind turbine technology has improved dramatically over the past decade, to the extent where wind turbine diameters are expected to soon exceed 160m and top 10MW in rated power output. While the development of these larger turbines has become immensely sophisticated, relatively little effort is being put forth to improve performance of smaller wind turbines, typically used in applications otherwise unsuitable for large installations. In this paper we investigate both computationally and experimentally the feasibility of a morphing turbine rotor, wherein blades are constructed of a flexible material and permitted to bend passively in response to external loading. The results indicate that the flexible blades can act as a passive pitch control device, resulting in significant improvements in efficiency when compared to a traditional rigid-blade design.Copyright

International Perspective on the Basin-Scale Water-Energy Nexus

This chapter addresses the current state of water and energy resources management in different regions of the world using basin-scale case studies from North America, Latin America, and Africa. It focuses on the characterization of the current state and future projections of water and energy resources available in each basin as well as management of information gaps and potential links for integrating water and energy management. Agriculture demands large amounts of water in each basin and tends to be a priority when water distribution decisions are being made. Overall, this chapter provides a worldwide view of the state of water and energy in semiarid regions, showing cases of water management strategies that are being carried out in the case study basins considered in this chapter.

Energy, water and global climate change as a regional agenda of the Americas

This paper is the result of a US National Science Foundation funded conference, titled “PASI 2010: Energy, Water, and Global Climate Change as a Regional Agenda of the Americas”, which took place in the summer of 2010. Distinguished faculty and scientists from a diverse range of backgrounds came together to discuss the importance of linking energy, water and climate change on a number of social, political and scientific platforms. The topics covered in this paper highlight the importance in bringing together researchers from different areas to collaborate and agree on solution strategies for such a large scale problem such as the impending energy and water crisis, and its effect on climate change.