Optimising wind turbines to harvest energy in cities

Vertical axis wind turbines use a design where the generator is vertically oriented in the tower rather than sitting horizontally on top.
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Engineers from the University of Utah’s Department of Mechanical Engineering have investigated the performance capabilities and financial benefits of vertical axis wind turbines for deployment in urban and suburban areas.

Engineers from the University of Utah’s Department of Mechanical Engineering have investigated the performance capabilities and financial benefits of vertical axis wind turbines for deployment in urban and suburban areas.

Vertical axis wind turbines (VAWTs) use a wind turbine design where the generator is vertically oriented in the tower, rather than sitting horizontally on top. There are many VAWT designs, but the engineering team studied the straight-blade Darrieus type, also known as a H-rotor turbine.

Small VAWTs are able to effectively operate in the presence of high turbulent flow, which makes them ideal energy harvesting devices in urban and suburban environments. According to the researchers, an optimally designed VAWT system can financially compete with fossil-fuel based power plants in these areas, and can even contribute to the develop of buildings or cities which consume net-zero energy.

The researchers input actual, time-resolved wind speed data into a numerical simulation that determined the total amount of energy captured by a turbine over a year of operation. They took data that had been accrued over the year 2009 from anemometers mounted on the top of traffic posts around Oklahoma City.

The researchers simulated 13 different wind turbine configurations, with a focus on four particular design parameters: height-to-diameter aspect ratio (H/D), blade airfoil shape, turbine solidity and turbine moment of inertia.

They identified the optimum design configuration by considering the percentage of energy captured by the turbine over the course of the year relative to the available energy in the turbulent wind during the same period.

Of the 13 design configurations, the optimal turbine design had the lowest moment of inertia.

The researchers also analysed the effect of the various turbine designs on the levelised cost of energy (LCOE) at one of the test sites, and found the blade characteristics that would yield economically viable options. The optimal design configuration at the site produced electricity at a cost 10 per cent lower than the average national electricity unit price.

“This is not the end of our research, and I think that we have more to study on the turbine design configuration and its operating conditions that would allow for enhancing the amount of energy captured by the turbine,” said Lam Nguyen, one of the lead researchers on the project.