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Oxford
Brookes University
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Different kinds of vertical axis wind turbines (VAWT): (a) Savonius; (b) Darrieus with "egg beater" design rotor; (c) H-shape blades; (d) helix shape blades. (Researchgate)
The now-familiar sight of traditional propeller wind turbines could be replaced in the future with wind farms containing more compact and efficient vertical turbines.
A
research team from the School of Engineering, Computing and Mathematics (ECM)
at Oxford Brookes led by Professor Iakovos Tzanakis conducted an in-depth study
using more than 11,500 hours of computer simulation to show that wind farms can
perform more efficiently by substituting the traditional propeller type
Horizontal Axis Wind Turbines (HAWTs), for compact Vertical Axis Wind Turbines
(VAWTs).
Vertical turbines are more efficient than traditional windmill turbines
The
research demonstrates for the first time at a realistic scale, the potential of
large scale VAWTs to outcompete current HAWT wind farm turbines.
VAWTs
spin around an axis vertical to the ground, and they exhibit the opposite
behaviour of the well-known propeller design (HAWTs). The research found that
VAWTs increase each other's performance when arranged in grid formations.
Positioning wind turbines to maximise outputs is critical to the design of wind
farms.
Professor
Tzanakis comments "This study evidences that the future of wind farms
should be vertical. Vertical axis wind farm turbines can be designed to be much
closer together, increasing their efficiency and ultimately lowering the prices
of electricity. In the long run, VAWTs can help accelerate the green transition
of our energy systems, so that more clean and sustainable energy comes from
renewable sources."
With
the UK's wind energy capacity expected to almost double by 2030, the findings
are a stepping stone towards designing more efficient wind farms, understanding
large scale wind energy harvesting techniques and ultimately improving the
renewable energy technology to more quickly replace fossil fuels as sources of
energy.
Cost
effective way to meet wind power targets
According
to the Global Wind Report 2021, the world needs to be installing wind power
three times faster over the next decade, in order to meet net zero targets and
avoid the worst impacts of climate change.
Lead
author of the report and Bachelor of Engineering graduate Joachim Toftegaard
Hansen commented: "Modern wind farms are one of the most efficient ways to
generate green energy, however, they have one major flaw: as the wind
approaches the front row of turbines, turbulence will be generated downstream.
The turbulence is detrimental to the performance of the subsequent rows.
"In
other words, the front row will convert about half the kinetic energy of the
wind into electricity, whereas for the back row, that number is down to 25-30%.
Each turbine costs more than £2 million/MW. As an engineer, it naturally
occurred to me that there must be a more cost-effective way."
The
study is the first to comprehensively analyse many aspects of wind turbine
performance, with regards to array angle, direction of rotation, turbine
spacing, and number of rotors. It is also the first research to investigate
whether the performance improvements hold true for three VAWT turbines set in a
series.
Dr
Mahak co-author of the article and Senior Lecturer in ECM comments: "The
importance of using computational methods in understanding flow physics can't
be underestimated. These types of design and enhancement studies are a fraction
of the cost compared to the huge experimental test facilities. This is
particularly important at the initial design phase and is extremely useful for
the industries trying to achieve maximum design efficiency and power
output."
