Winds of change

G Magazine

They’re touted as the next big thing in renewable energy and could be coming to a neighbourhood near you. G investigates the viability of micro wind turbines.

Micro Wind Turbines

The process of connecting wind energy to the grid is not as simple as it is for solar, so the initial cost of such a system is quite high and the payback period fairly lengthy.

Credit: iStockphoto

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Despite our optimistic reliance on the corporate world and our governments to instigate large-scale change, sustainability is still very much a personal crusade. We each strive to limit our own eco-footprint and become as self-sufficient as possible. And so it is with generating renewable energy. While the major players are busy constructing commercial sources of clean energy, those of us at grassroots level are just as concerned with generating clean power for our homes.

Backed by a mature market, a sizeable Federal Government rebate scheme and the hallmark of consumer acceptance - predictability - solar is the preferred choice to date in the domestic arena. But in recent years a change has begun to blow in the wind… literally. Domestic micro wind turbines (MWTs) have sparked the interest of clean energy manufacturers and homeowners alike in our cities and towns.

Introducing MWTs

Historically, there is nothing new about wind turbines. In the 1930s and 1940s, MWTs were hugely popular in rural Australia and America in the absence of grid connections, but the mass electrification of rural areas saw the industry made virtually redundant.

Recently, their commercial cousins have hit centre stage in country areas as Australia's cheapest and fastest growing renewable energy source, competing head to head with coal in terms of cost.

The technology of MWTs is very similar to commercial wind farms, but it offers two alternatives, each with its pros and cons. Horizontal axis MWTs are miniature versions of commercial turbines. They resemble a fan and spin around a horizontal point to generate energy. Contrastingly, vertical axis MWTs spin around a vertical point and can pick up the wind from any direction, rather than having to turn to face the wind like the horizontal varieties.

"Vertical axis MWTs operate better in turbulent environments as they're less impacted by turbulence than horizontal axis turbines," says Craig Memery, energy policy advocate for Australia's Alternative Technology Association (ATA). "However, the big disadvantage of vertical axis turbines is that they're very, very inefficient - they don't put out a lot of energy. It's very unlikely that a vertical axis turbine will even pay back the amount of energy that goes into making it in a lot of cases."

So which is the better option? "In simple terms, horizontal wind turbines are definitely the way to go," Memery says. "They mimic the way it's done in large-scale wind farms and they're cheaper and more efficient."

The trouble with wind

In theory, it makes perfect sense: use a weather phenomenon common to all climates to generate energy. The reality, however, is that wind is unpredictable and inconsistent. As such it is also difficult to capture in urban environments full of obstructions. And unlike solar, where sunshine hours are virtually identical across a large geographic area, the intensity and amount of wind can change from one city block to the next.

"In terms of harnessing wind energy, two metres difference in the location of the turbine can affect whether the wind turbine operates efficiently or not," says Damien Leclercq, managing director of Cyclopic Energy, a wind power consultancy with office in Adelaide and Melbourne. He recommends proposed MWT sites be assessed for suitability prior to any installation.

"For me, putting in a wind turbine is a bit like drilling for oil - you don't drill for oil anywhere, you drill for oil where you know there is oil in the first place. Then you do a really detailed measurement to make sure that where you're going to put a hole in the ground has a big reserve of oil under it. It's the same for wind. You really need to have a good site and do your homework to ascertain if it's viable."

The Australian Bureau of Meteorology has collated 30 years of wind data. This information gives a good indication of general trends but doesn't account for individual site variance, which can be sizeable. For example, if your neighbours build a second storey or chop down a large gum tree in their backyard, it will alter the nature of your wind generation significantly.

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