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

Wind towers are getting taller.
Shutterstock

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.

---

Read more:
Wind and solar cut rather than boost Australia’s wholesale electricity prices

---

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.

---

Shutterstock/The Conversation

---

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.

---

Read more:
Are public objections to wind farms overblown?

---

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.
Shutterstock

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.
Shutterstock

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.

---

Read more:
Wind turbines aren’t quite ‘apex predators’, but the truth is far more interesting

---

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.

Advertisement

Dog owners could take the lead on dingo conservation with a ‘Fido fund’

Dingo puppers. A small levy on dog costs could help create more ethical management of dingoes.
Shutterstock

Neil R Jordan, UNSW and Rob Appleby, Griffith University

Humans and dogs go way back. From wolf totems to the big bad wolf of fact and fairy tale, through sheepdogs, lap dogs, and labradoodles, our relationships with these animals are complex, emotionally charged and sometimes contradictory.

The split between humanity’s lavishing of affection on domestic dogs and our contrasting animosity towards their wild relatives is well-documented. But what of domestic dogs and dingoes?

Our research, published today, found similarly contrasting relationships in Australia, where the dingo, Australia’s native dog, is frequently killed for management. We suggest that an inexpensive “dingo conservation levy” on domestic dog costs could fund more ethical management of dingoes. In this way our affection for domestic dogs could be harnessed to improve conservation outcomes for their wild relatives.

Dingoes have an ecotourism appeal in places like K’gari (Fraser Island)
Shutterstock

Canine economics

Australians collectively spend over A$10 billion each year on their domestic dogs – housing, feeding, and sometimes even giving them the status of honorary family members. Meanwhile, government and landowners jointly spend at least A$30 million on large-scale exclusion fencing and lethal control of dingoes.

Industry funded research suggests that dingoes killing livestock, especially sheep, and efforts to control dingoes, cost at least A$145 million annually. What’s more, such losses also come with psychological stress, which you can’t always put a price on.

Other research suggests dingoes, as top predators, provide considerable economic benefits. For example, dingoes prey upon kangaroos and other herbivores that may compete with livestock for food and water. In fact, some estimates suggest dingoes improve gross margins by $0.83 per hectare in this context.

They also help biodiversity by suppressing feral cats and foxes, and dingoes have considerable ecotourism appeal in locations like K’gari (Fraser Island) and Kakadu National Park.

Managing dingoes

Australia’s current approach to dingo management highlights the paradox of an animal viewed both as a valuable native predator that should be conserved, and as a pest to be destroyed. And this makes it a nightmare to manage.

The dingo fence stretches for thousands of kilometres in the Australian outback to try to keep dingoes away from sheep and livestock.
Shutterstock

Current dingo management relies heavily on exclusion fencing and lethal control, and around 200kg of 1080 powder (poison) is administered to baits and peppered across the continent annually.

Countless bullets are also fired, and traps set, as the lion’s share of management budgets is allocated to business as usual. To break this deadly cycle, there is a clear need to provide farmers and governments with good evidence that different approaches could work. This can only be done through substantial parallel investment in robust, independent experimental tests of alternative approaches.

Despite broad support in society for non-lethal management, accessing sufficient funds to support such a transition remains challenging.

A modest dingo conservation levy could fund this. With a levy on the A$10 billion domestic dog industry, we could harness humanity’s affinity for domestic dogs to improve conservation and welfare outcomes for their wild counterparts.

It wouldn’t need to be prohibitively expensive either.

A levy on the sale of pet dogs, dog food, or both, of only about 0.3% of the amount that pet owners spend on this annually – or A$7.36 per dog – would generate A$30 million each year.

That is similar to the lowest estimates of current national spending on dingo control, which means we would potentially see the current spending doubled.

Why should dog owners pick up the tab?

Applying a levy to all dog owners may seem unfair, and perhaps it is. But as Australia’s “dingo problem” is, arguably, at least in part caused by domestic dogs gone feral, such a levy would seem no more unfair on conscientious dog owners than third-party insurance is on careful drivers.

Given that pet owners tend to view wild animals more positively and show more concern for their welfare, such a levy might actually be well received by dog-owners anyway.

An alternative approach might be to seek the voluntary involvement of pet-food manufacturers in such a scheme, giving consumers choice over whether to support it.

Dog-lovers generally also love wild animals, and may be happy to pick up the costs for ethical dingo conservation.
Shutterstock

A dingo conservation levy – perhaps supplemented by a voluntary fund for donors without dogs – might also be more acceptable and attractive if it were clear the funds would be specifically channelled towards research and uptake of non-lethal tools.

Generally, we are broadly in favour of any techniques designed to reduce the animosity towards dingoes, reduce the costs and negative impacts of living alongside them, and boost the positive effects dingoes have on ecosystems.

As some have already argued, they are all dogs at the end of the day. Perhaps then it is time that we treated them as such.

---

We would like to gratefully acknowledge the contributions of Mike Letnic, Henry Brink, Brad Purcell and Hugh Webster to this article.

Neil R Jordan, Lecturer, UNSW and Rob Appleby, PhD student at the Environmental Futures Research Institute, Griffith University

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