Utility-scale Wind Turbines and Wind Farms

Wind power is a pillar of low emission energy systems. Designing more efficient wind turbines and farms, and increasing reliability and flexibility, is an area of intense research and development. In order to overcome the intermittent character of wind power, both the individual turbines and the wind farm as a whole must be considered. Many recent advances have been achieved in multiple aspects of utility-scale wind power. This structured research review conveys recent progress, with chapters written by an international team of experts. Organized into five parts, the book covers the aerodynamics of turbines and farms including layout; control techniques; environmental concerns including noise and bird and bat collisions; the intermittency issue including forecasting, storage and hybrid wind-PV plants; and offshore wind farms. From the general principles of aerodynamics to detailed and systematic coverage of the latest developments, Utility-scale Wind Turbines and Wind Farms provides a convenient and up-to-date source of information for academic researchers and R&D professionals working in this field

Structural analysis of an underwater energy storage accumulator

A full-scale three-dimensional simulation was conducted to investigate structural response of an underwater compressed air energy storage (UWCAES) accumulator to the hydrodynamic loads at Reynolds number of 2.3×105. The accumulator was assumed to be spherical, non-distensible and fixed to the bed of a water body via a cylindrical homogeneous isotropic elastic support. The simulation was carried out for three different supports with aspect ratios AR of 5, 10 and 20 where AR was defined as the ratio of the length to the diameter of the support. The effects of the aspect ratio on the frequency and amplitude of the vibrations of the solid structure induced by hydrodynamic loading were investigated. It was observed that the amplitude of the vibrations increases with the aspect ratio of the support, whereas the frequency decreases. The displacement of the spherical accumulator was illustrated on the X-Y plane for each case

Flow past an accumulator unit of an underwater energy storage system: Three touching balloons in a floral configuration

An LES simulation of flow over an accumulator unit of an underwater compressed air energy storage facility was conducted. The accumulator unit consists of three touching underwater balloons arranged in a floral configuration. The structure of the flow was examined via three dimensional iso surfaces of the Q criterion. Vortical cores were observed on the leeward surface of the balloons. The swirling tube flows generated by these vortical cores were depicted through three dimensional path lines. The flow dynamics were visualized via time series snapshots of two dimensional vorticity contours perpendicular to the flow direction; revealing the turbulent swinging motions of the aforementioned shedding-swirling tube flows. The time history of the hydrodynamic loading was presented in terms of lift and drag coefficients. Drag coefficient of each individual balloon in the floral configuration was smaller than that of a single balloon. It was found that the total drag coefficient of the floral unit of three touching balloons, i.e. summation of the drag coefficients of the balloons, is not too much larger than that of a single balloon whereas it provides three times the storage capacity. In addition to its practical significance in designing appropriate foundation and supports, the instantaneous hydrodynamic loading was used to determine the frequency of the turbulent swirling-swinging motions of the shedding vortex tubes; the Strouhal number was found to be larger than that of a single sphere at the same Reynolds number

Underwater compressed air energy storage improved through Vortex Hydro Energy

A power generating energy storage system is presented. The proposed self-powered energy storage technology (UWCAES-VHE) is a hybrid of Underwater Compressed Air Energy Storage (UWCAES) and the Vortex Induced Vibration Aquatic Clean Energy (VIVACE) converter invented by Bernitsas and Raghavan [1] to harness Vortex Hydro Energy (VHE). The present technology significantly improves the roundtrip efficiency of conventional UWCAES. Through this hybridization, the energy conversion efficiency of the VIVACE converters performing as the accumulator-converters of the UWCAES-VHE is expected to be higher than that of the conventional VIVACE converters. It is further demonstrated that the round trip efficiency of the UWCAES-VHE and the VHE conversion efficiency of the VIVACE are linearly related. UWCAES-VHE and conventional UWCAES are quantitatively compared. © 2014 Elsevier Ltd

Correlating Flow Pattern with Force Coefficients in Air Flow past a Tandem Unit of Three Circular Cylinders

Air Flow past three circular cylinders in tandem arrangement is simulated at 20 different Reynolds numbers ranging from 20 to 300. The spacing ratio L=D is set at 2, where L is center to center distance. The drag of all three cylinders is assessed with varying Reynolds number. Accordingly, pressure and velocity distribution in the near vicinity of cylinders is closely examined. It is found that Reynolds numbers of 42, 63 and 150 are critical Reynolds numbers for pressure, viscous and total drag forces respectively. Moreover, time evolutions of force coefficients are investigated to find the transitional Reynolds number at which the flow becomes unsteady and vortices are shed from the cylinders. It was observed that transition starts at Re = 101 and vortex shedding occurs at Re = 105 for the first time. Flow pattern is illustrated at a specific moment for all steady, transitional and unsteady states at various Reynolds numbers. Also, the time evolution of flow pattern is depicted for unsteady cases. It was observed that frequency of vortex shedding and also Strouhal number increase with Re. © 2013 Begell House, Inc

Energy storage using weights hydraulically lifted above ground

Renewable energy sources constitute an ever-growing share of the total electrical market; but, the intermittency and instability issues make it difficult to dispatch these sources directly into the grid. Energy storage represents a promising solution to overcome this obstacle. Among energy storage solutions, pumped hydro energy storage is largely considered the most technologically and financially feasible, though having some drawbacks. In this paper, a new design is introduced to address the major challenges associated with the conventional pumped hydro energy storage. The proposed storage solution does not require tall water tank towers or long piping; rendering it more cost effective and implementable. It is also scalable to operate over a wide range of capacities depending on the electrical surpluses. Beyond this, the design provides a constant pressure and faster discharge, furnishing a quick response to instantaneous demand fluctuations. © 2013 Taylor & Francis