Research and development for shrouded wind turbines

https://centaur.reading.ac.uk/36014/1/1-s2.0-S0167610513002808-main.pdf

Unsteady flow simulation of a vertical axis augmented wind turbine: a two-dimensional study

Effects of the duct thrust on the performance of ducted wind turbines

As part of a large project aimed at finding the optimal configuration for an aerogenerator to exploit wind power, an investigation was launched to find the most compact shroud possible. The dominant contributor to the shroud length is the structure downstream of the turbine (the diffuser). This component has an ever increasing cross-section as one progresses downstream, however, fast rate of area divergence will cause flow separation and the significant reduction in output power associated with it. It is the purpose of the present paper to demonstrate ways to overcome this difficulty. This can be achieved either by proper diversion and introduction of the shroud's external flow into the diffuser's inner boundary layer or alternatively, by the usage of a ring-flap.

Compact shrouds for wind turbines

A new class of diffuser augmented wind turbines (DAWTs) is presented. The new diffuser concept exploits aero-dynamic principles for the creation of high-lift airfoil configurations known from the aircraft industry. Combining this with our objective of obtaining a compact power-efficient design has enabled creation of a family of DAWT designs with energy capture potentials which exceed the power efficiency based on the diffuser exit area by 50%. The paper presents the 1D momentum theory governing the DAWTs, and discusses upper limits for power extraction, similar to the Betz limit applicable for bare Horizontal-Axis Wind Turbines (HAWTs). Inviscid axisymmetric panel code calculations are then used to drive the diffuser design towards higher power coefficients. Axisymmetric actuator disk Navier-Stokes calculations reveal the types of stall that inhibit the functionality of the ideal inviscid optimum, leading the design towards the new class of DAWTs. DAWT performance has been differently measured over time, creating confusion. Proper comparison with performance of existing DAWT designs is therefore emphasized. This involves reference to established literature results, and recalculation of earlier DAWT designs in an attempt to project all results onto a common metric.

https://www.mdpi.com/1996-1073/7/5/3256/pdf

A Multi-Element Diffuser Augmented Wind Turbine

Investigation of diffuser-augmented wind turbines

Information on diffuser-augmented wind turbines is presented concerning the development of efficient and compact diffusers, economic analysis, and analytical demonstration of two-stage constant speed rotor concepts.

/pdf/investigation-of-diffuser-augmented-wind-turbines-part-ii-9wic8r21p5.pdf

Investigation of diffuser-augmented wind turbines. Part II. Technical report

The Diffuser-Augmented Wind Turbine (DAWT) is one of the more promising advanced concepts for decreasing the cost of wind energy conversion. The first results of an investigation designed to determine the most effective configurations for DAWT's and to assess their ultimate performance in large units are presented. Two types of compact diffusers have been analyzed and tested, using screens to simulate the turbines. A 20/sup 0/ half-angle conical diffuser with two tangential boundary layer control slots provided a measured augmentation ratio of 1.7 at an area ratio of 2.8, while a double ring-wing diffuser gave 2.1 at an equivalent area ratio of 3.8. Results indicate potential for considerable improvement and further size reduction. Several analyses related to diffuser development are given.

Investigation of diffuser-augmented wind turbines. Progress report, June 25, 1975--December 24, 1975

The Diffuser Augmented Wind Turbine (DAWT) is one of the advanced concepts being investigated to improve the economics of wind energy conversion. The project is aimed at increasing the output and reducing the cost, the off-duty time, and the technical risk of wind energy conversion systems (WECS). The DAWT appears to be best suited to large WECS for commercial power production because it permits a significant increase in the unit power output without extending the size of rotating machinery into the range where rotor dynamics cause excessive costs.

/pdf/investigation-of-diffuser-augmented-wind-turbines-part-i-1yha6fvmfm.pdf

B.L. Gilbert

Papers

Investigation of diffuser-augmented wind turbines

Investigation of diffuser-augmented wind turbines. Part II. Technical report

Investigation of diffuser-augmented wind turbines. Progress report, June 25, 1975--December 24, 1975

Investigation of diffuser-augmented wind turbines. Part I. Executive summary