Saturday, August 19, 2017

Two-bladed wind turbines - continued

Photo by Clark (on flickr)
In my last post (Two-bladed offshore turbines, 12 August) I wrote about an article that claimed two-bladed offshore turbines were more efficient and more economical than three-bladed turbines. I looked for further information, and found an article from the MIT Technology Review website that had been written earlier - in June 2014. It also presents support for the advantages of two-bladed turbines, particulary those offshore.

The article is Two-Bladed Wind Turbines Make a Comeback.


Interestingly, despite the title, the article does not refer to two-bladed turbines having been used before, so it doesn't really focus on a "comeback." It focuses instead on the two-bladed model as being a recent "alternative." As a cross reference to the two-bladed turbine as being an earlier model, see the article by Martin Jakubowski in my last post.

What makes this Technology Review article interesting for me is that it has much of the same support as the first article, as well as many of the same language features. Students could read the articles, then find the advantages that are mentioned in both. They can also compare the way the advantages are described in a cause-and-effect (or "impact") style. For example:

From Jakubowski's article:
  • "...two-bladed rotors are better suited for wind turbines because of their flexible configuration -- namely, their attachement to the shaft by a flexible hinge. This allows the rotor to have a second degree of freedom. ... This flexible hinge reduces the impact of cyclic loading (fluctuating stresses and strains from the wind), and strongly reduces wear and tear -- fatigue -- on the components, thus extending the lifetime of the turbine."

From the Technology Review article:
  • "Two-bladed turbines cost less because they use fewer materials. The removal of one blade makes the rotor lighter, which in turn makes it possible to place the rotor on the downwind side of the tower. ... Light, flexible rotors translate into further materials savings in the turbine's gearbox, tower and foundation."

The advantages of the two-bladed wind turbine mentioned in both articles are:
  • reduced weight of rotor
  • lower material costs
  • lower operations and maintenance costs
  • easier to install
  • costs less to build

The articles mention a total of five disadvantages, and the one disadvantage they have in common is the louder noise:
  • "slightly higher tipspeed noise"
  • It's louder, for one thing, in part because the blades spin faster"
but both articles mention that this disadvantage is not important for offshore turbines:
  • "The only relevant disadvantages of the two-blade design ... are unimportant offshore."
  • "... although this isn't a problem offshore."
The language features I highlighted in my last post are also found in this article. By comparing the two articles, a number of the same features and phrases can be found in both.

Phrases for argumentation:
  • By some estimates,
  • More importantly,
  • In fact,
  • According to,
  • For that reason,
Collocations of technical advantages:
  • grow faster
  • costs can be brought down
  • greatly improve the economics
  • cost twice as much as
  • generate as much power as
  • costing twice as much as
  • less than those of
  • etc.

The linking and transition terms are also useful for students to highlight, since there are many in common in both articles, or terms that serve the same function. Just a few examples from the Technology Review article:
  • same as
  • as much as
  • but
  • which in turn
  • in part because
  • because of
  • however
  • for that reason
  • rather than

There are also words of comparison, superlatives, as well as adverbs.

I think that each article, or both articles compared, are good sources of information about two-bladed turbines as well as useful examples of argumentation and support, with relevant language features. It would be interesting for students to find further articles and sources of information about this turbine design for other comparisons.

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