From the Wind energy: On the grid, off the checkerboard
WASHINGTON D.C., April 1, 2014 — As wind farms grow in importance across the globe as sources of clean, renewable energy, one key consideration in their construction is their physical design — spacing and orienting individual turbines to maximize their efficiency and minimize any “wake effects,” where the swooping blades of one reduces the energy in the wind available for the following turbine.
Optimally spacing turbines allows them to capture more wind, produce more power and increase revenue for the farm. Knowing this, designers in the industry typically apply simple computer models to help determine the best arrangements of the turbines. This works well for small wind farms but becomes less precise for larger wind-farms where the wakes interact with one another and the overall effect is harder to predict.
Now a team of researchers at Johns Hopkins University (JHU) has developed a new way to study wake effects that takes into account the airflow both within and around a wind farm and challenges the conventional belief that turbines arrayed in checker board patterns produce the highest power output. Their study provides insight into factors that determine the most favorable positioning — work described in a new paper in the Journal of Renewable and Sustainable Energy, which is produced by AIP Publishing.
This insight is important for wind project designers in the future to configure turbine farms for increased power output — especially in places with strong prevailing winds.
“It’s important to consider these configurations in test cases,” said Richard Stevens, who conducted the research with Charles Meneveau and Dennice Gayme at JHU. “If turbines are built in a non-optimal arrangement, the amount of electricity produced would be less and so would the revenue of the wind farm.”
How Wind Farms are Currently Designed
Many considerations go into the design of a wind farm. The most ideal turbine arrangement will differ depending on location. The specific topology of the landscape, whether hilly or flat, and the yearlong weather patterns at that site both dictate the specific designs. Political and social considerations may also factor in the choice of sites.
Common test cases to study wind-farm behavior are wind farms in which turbines are either installed in rows, which will be aligned against the prevailing winds, or in staggered, checkerboard-style blocks where each row of turbines is spaced to peek out between the gaps in the previous row.
Staggered farms are generally preferred because they harvest more energy in a smaller footprint, but what Stevens and his colleagues showed is that the checkerboard style can be improved in some cases.
Specifically, they found that better power output may be obtained through an “intermediate” staggering, where each row is imperfectly offset — like a checkerboard that has slipped slightly out of whack.
This work was funded by the National Science Foundation (grant #CBET 1133800 and #OISE 1243482) and by a “Fellowship for Young Energy Scientists” awarded by the Foundation for Fundamental Research on Matter in the Netherlands. The work used XSEDE (NSF) and SURFsara (Netherlands) computer resources.
The article, “Large Eddy Simulation studies of the effects of alignment and wind farm length” is authored by Richard J. A. M. Stevens, Dennice F. Gayme and Charles Meneveau. It will be published in the Journal of Renewable and Sustainable Energy on April 1, 2014 (DOI: 10.1063/1.4869568). After that date, it can be accessed at: http://tinyurl.com/n9o282o
Electric cars are cheap and common in North America, we call them golf carts. However traffic regulations usually prevent their use in cities.
Hmm, so 125,000 pretty expensive doorstops have been sold since 2010. (By the way, I only counted the pure battery EVs in those lists even though I’d probably include the Chevy Volt given what I’ve heard about how their owners actually use them.)
Oops, the list.
http://insideevs.com/monthly-plug-in-sales-scorecard/
Matt, the average commute is 25 to 30 miles a day. The average car is driven 13,000 miles a year, or 35 miles a day. If, as you plausibly argue, a multi-car household fully uses each vehicle, I’d still suggest that only one of those cars usually gets driven out of town.
True, there are plenty of exceptions. That’s what makes cars so great. They are tools of freedom, so the averages only go so far. So no one can make a blanket statement about every car. There isn’t one car market but multiple car markets.
I don’t think today’s mid-priced EVs, i.e. the LEAF, have enough range for the commuter car markets. The average “80%” range is 65-70 miles, but you have to subtract 15 miles for winter. Given the standard deviations involved, it’s just not enough.
But if you double that, or even better, double-and-a-half it, and wind up with a minimum dependable “80% range” of 95 miles at double and 120 miles at double-and-a-half, and I think there’s a substantial market. Not every American is scraping along on a shoestring budget. True, the middle- and upper-middle classes ain’t what they were in the 1970s and ’80s, but they are far from vanished.
Janice Moore says:
And some physics to explain why windmills are eternally inefficient:
“Betz’ law (Year 1919) says that one can only convert not more
than 16/27 (or 59%) of the kinetic energy in the wind to
mechanical energy using a wind turbine.”
No form of energy conversion is every going to be totally efficient.
A more important issue with wind power is that it varies effectivly at random. In an electrical grid it’s a requirement for supply to meet demand. Without some huge batteries wind power just isn’t a sensible replacement for a steam turbine power station. The only kind of such “batteries” which are currently available are pumped hydro stations. In which case wind driven water pumps might be a better oftion than wind driven electrical generators.