Taller, faster, better, stronger: wind towers are only getting bigger

Wind towers are getting taller.
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Con Doolan, UNSW

Former Australian Greens leader Bob Brown made headlines this week after he objected to a proposed wind farm on Tasmania’s Robbins Island. The development would see 200 towers built, each standing 270 metres from base to the tip of their blades.

Leaving aside the question of the Robbins Island development, these will be extraordinarily tall towers. However, they fit right in with the current trend for wind turbines.

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Wind turbines come in many designs, but the most common is the so-called “horizontal axis” kind, which look like giant fans on poles. This type of turbine is highly efficient at turning the energy in the wind into electrical energy.

Keen observers will have noticed that these turbines have been gaining in size over the years. In the 1990s, wind turbines typically had hub heights and rotor diameters of the order of 30m. Today, hub heights and rotor diameters are pushing well past 100m.

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Bigger is better

When it comes to wind turbines, bigger is definitely better. The bigger the radius of the rotor blades (or diameter of the “rotor disc”), the more wind the blades can use to turn into torque that drives the electrical generators in the hub. More torque means more power. Increasing the diameter means that not only more power can be extracted, but it can be done so more efficiently.

Larger and longer turbine blades mean greater aerodynamic efficiency. Creating more power in one turbine means less energy is lost as it is moved into the transmission system, and from there into the electrical generator. The economies of scale provide an overwhelming push for wind energy companies to develop larger rotor blades.

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Wind turbines are also growing taller because of the way wind travels around the world. Because air is viscous (like very thin honey) and “sticks” to the ground, the wind velocity at higher altitudes can be many times higher than at ground level.

Hence it is advantageous to put the turbine high in the sky where there is more energy to extract. Hilly terrain (like a mountain ridge) may also distort the wind, requiring engineers to design the wind turbines to be even taller to catch the wind. Wind turbines used offshore are generally larger and taller because of the higher levels of wind energy available at sea.

Typically, onshore turbines (most common in Australia) have blades between 40m and 90m long. Tower heights are usually in the range of 150m. Offshore turbines (those situated at sea and common in Europe) are much larger.

Offshore turbines are typically much larger than onshore towers.
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One of the largest wind turbine designs in the world, General Electric’s offshore 12-megawatt Haliade-X, has 107m blades and a total height of 260m. As a comparison, Sydney’s Centrepoint tower is 309m tall.

If the Robbins Island turbines are indeed built to 270m, as reported in the media, they would eclipse General Electric’s behemoths. I cannot speak to the likelihood of this, but I would assume engineers will have to select the best turbine for the prevailing wind conditions and existing infrastructure.

Challenging heights

The quest for bigger and taller turbines comes with its fair share of engineering challenges.

Longer blades are more flexible than shorter ones, which can create vibration. If not controlled, this vibration affects performance and reduces the life of the blades and anything they are attached to, such as the gearbox or generator.

Materials and manufacturing techniques are constantly being refined to create longer, and longer-lasting, turbine blades.

The longer the turbine’s blades, the more pressure is put on internal mechanisms.
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Taller turbines generate more power, which puts greater loads on the gearbox and transmission system, requiring mechanical engineers to develop new ways of converting the ever-increasing torque into electrical power. Taller wind turbines also need stronger support towers and foundations. The list of challenges is long.

As turbines grow, so too does the noise they make. The dominant source of noise occurs at the outer edge of the blades. Here, turbulence caused by the blade itself creates a “hissing” sound as it passes over the trailing edge. More noise is created when the blade chops through atmospheric turbulence in the wind as it blows into the tower.

Noise isn’t just a matter of size. If one turbine is placed in the wake of another, the sound of its blades passing through the highly turbulent air created by the upstream turbine will be very loud.

Keeping noise under control requires inventive solutions, such as borrowing ideas from nature: the silent-flying owl uses serrated feathers to control noise and these are now being used to make noisy turbines quieter.

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Of course, engineering challenges are not the only considerations for creating wind farms. Environmental effects, noise, visual impacts and other community concerns all need to be considered, as with any large infrastructure project. But wind turbines are one of the most cost-effective and technologically sophisticated forms of renewable energy, and as the developed world comes to grips with climate change we will only see more of them.

Con Doolan, Professor, School of Mechanical and Manufacturing Engineering, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Who tilts at windmills? Explaining hostility to renewables

Marc Hudson, University of Manchester

Studying the catastrophe that has been Australian climate and energy policy these past 30 years is a thoroughly depressing business. When you read great work by Guy Pearse, Clive Hamilton, Maria Taylor and Phillip Chubb, among others, you find yourself asking “why”?

Why were we so stupid, so unrelentingly shortsighted? Why did the revelation in 2004 that John Howard had called a meeting of big business to help him slow the growth of renewables elicit no more than a shrug? Why did policy-makers attack renewable energy so unrelentingly?

About now, readers will be rolling their eyes and saying either “follow the money, stupid!” or “they are blinded by their marketophilia”. Fair enough, and they have a point.

My recently published paper, titled “Wind beneath their contempt: why Australian policymakers oppose solar and wind energy”
outlines the hostility to renewables from people like former treasurer Joe Hockey, who found the wind turbines around Canberra’s Lake George “utterly offensive”, and former prime minister Tony Abbott, who funded studies into the “potential health impacts” of wind farms.

It also deals with the policy-go-round that led to a drop in investment in renewables.

In a search for explanations for this, my paper looks at what we academics call “material factors”, such as party donations, post-career jobs, blame avoidance, diminished government capacity to act, and active disinformation by incumbents.

I then turn to ideological factors such as neoliberalism, the “growth at all costs” mindset, and of course climate denial.

Where it gets fun – and possibly controversial – is when I turn to psychological explanations such as what the sociologist Karl Mannheim called “the problem of generations”. This is best explained by a Douglas Adams quote:

Anything that is in the world when you’re born is normal and ordinary and is just a natural part of the way the world works.
Anything that’s invented between when you’re fifteen and thirty-five is new and exciting and revolutionary and you can probably get a career in it.
Anything invented after you’re thirty-five is against the natural order of things.

Over the past 50 years, white heterosexual middle-class males with engineering backgrounds have felt this pattern particularly keenly, as their world has shifted and changed around them. To quote my own research paper:

This loss of the promise of control over nature occurred – by coincidence – at the same time that the British empire disintegrated, and the US empire met its match in the jungles of Vietnam, and while feminism, civil rights and gay rights all sprang up. What scholars of the Anthropocene have come to call the “Great Acceleration” from the 1950s, was followed by the great (and still incomplete) democratisation of the 1960s and 1970s.

The rising popularity of solar panels represents a similar pattern of democratisation, and associated loss of control for those with a vested interest in conventional power generation, which would presumably be particularly threatening to those attracted to status, power and hierarchy.

Consider the cringe

Here are a couple more ideas and explanations that didn’t make the cut when I wrote the research paper. First up is the “biological cringe” – analogous to the “cultural cringe”, the self-loathing Australian assumption that all things British were better.

In Ecology and Empire: Environmental History of Settler Societies, the historian Tom Griffiths notes that:

Acclimatization societies systematically imported species that were regarded as useful, aesthetic or respectably wild to fill the perceived gaps in primitive Australian nature. This “biological cringe” was remarkably persistent and even informed twentieth-century preservation movements, when people came to feel that the remnants of the relic fauna, flora and peoples, genetically unable to fend for themselves, should be “saved”.

Second, and related, is the contempt and hatred that settler colonialists can feel towards wilderness, which in turn morphs into the ideology that there should be no limits on expansion and growth.

This means that people who speak of limits are inevitably attacked. One good example is Thomas Griffith Taylor (1880-1963), an Australian scientist who fell foul of the boosters who believed the country could and should support up to 500 million people.

Having seen his textbook banned in Western Australia for using the words “arid” and “desert”, Taylor set sail for the United States. At his farewell banquet at University of Sydney, he reinterpreted its motto Sidere mens eadem mutate (“The same spirit under a different sky”), as “Though the heavens fall I am of the same mind as my great-great-grandfather!”

I am anticipating that at least four groups will object to my speculations:
(vulgar) Marxists, for whom everything is about profits; positivists and Popperians, who will mutter about a lack of disprovability; deniers of climate science, who often don’t like being described as such; and finally, those who argue that renewables cannot possibly provide the energy return on investment required to run a modern industrial economy (who may or may not be right – we are about to find out).

Reader, of whatever category, what do you think?

Marc Hudson, PhD Candidate, Sustainable Consumption Institute, University of Manchester

This article was originally published on The Conversation. Read the original article.