Rotational Speed

The aim of the wind turbine designer is the production of energy at minimum cost, subject to constraints imposed by environmental impact considerations. However, blade designs optimized for a number of different rotational speeds but the same rated power produce substantially the same energy yield, so the choice of rotational speed is based on machine cost rather than energy yield.

One of the key cost drivers is the rotor torque at rated power, as this is the main determinant of the drive train cost. For a given tip radius and machine rating, the rotor torque is inversely proportional to rotational speed, which argues for the adoption of a high rotational speed. However increasing the rotational speed has adverse effects on the rotor design, which are explored in the following sections.

6.4.1 Ideal relationship between rotational speed and solidity

Equation (3.67a) in Section 3.7.2 gives the chord distribution of a blade optimized to give maximum power at a particular tip speed ratio in terms of the lift coefficient, ignoring drag and tip loss:

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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