Micro-wind turbines
by Chris Woodford. Last updated: August 25, 2011.
If small is beautiful, micro-wind turbines—tiny power generators perched on a roof or mast—should be the most attractive form of renewable energy by far. Some manufacturers have pushed the technology aggressively, hinting to consumers about big savings on electricity bills and major benefits for the environment. The reality is a little different: microturbines do indeed bring economic and environmental benefits if they're sited in reliably windy areas, but they're less helpful in towns and cities where buildings make "energy harvesting" more of a challenge. So are micro-wind turbines really worth the investment? How do they compare with their big brothers? Let's take a closer look!
Photo: A micro-wind turbine in the process of being raised into position. The propeller part is at the front and the mast is stretching away into the distance behind it. Photo by Warren Gretz courtesy of US Department of Energy/NREL (DoE/NREL).
Power to the people
Photo: Micro power to the people! Now in position, the small mast-mounted wind turbine from our top photo can produce 900 watts of power with a wind speed of 45km/h (28mph). Photo by Warren Gretz courtesy of US Department of Energy/NREL (DoE/NREL).
Our electricity infrastructure is remarkably centralized, with huge power plants sending electricity vast distances across grid networks to factories, offices, and homes. It sounds good in theory: you don't have to worry about where your energy is coming from—just plug in your TV, pay your bill, and you'll be fine.
Most people don't realize how wasteful this centralized system can be. Large power plants (especially old ones fuelled by coal) can be hugely inefficient. Energy is wasted both in the plants themselves and in the process of sending their electricity down cables to our homes; according to a Greenpeace report (Decentralising Power: An Energy Revolution for the 21st Century), about two thirds of the energy produced in the first place can be lost in this way. That's a very serious problem if you bear in mind that the vast majority of our energy currently comes come from a very limited reserve of fossil fuels—and every ton of coal and liter of oil or gas we burn puts the planet at greater risk of global warming and climate change. Centralized systems, though proven to be extremely reliable over many decades, also lock us into a dependence on foreign energy (oil from the Middle East, gas from Russia, coal from Colombia, and so on).
Wouldn't it be great if we could produce all our own electricity without worrying about energy prices, global warming, oil crises, and the rest? In theory, that's exactly the promise that renewable energy—wind turbines, solar power, and other technologies such as heat pumps and tidal power—is offering us.
What are micro-wind turbines?
If you've ever seen a conventional wind turbine, you'll know it's a towering beast of a machine. A typical turbine is about 80m (260ft) high with rotor blades about 70m (230ft) across. Imagine 40 adults standing on top of one another and you can visualize the height; now picture them standing with their arms outstretched in a line, all touching, and you can visualize the rotor span as well. One single wind turbine makes about 1–3 megawatts (MW) of electricity, which is enough to supply about 500–1500 homes. You need about 1000 turbines like this to generate as much electricity as a big nuclear or coal-fired power plant. That's why wind turbines are often built in clusters called wind farms.
Single wind turbines are effectively mini power plants that supply whole communities. So, what we achieve by erecting a large wind turbine is to scale down and decentralize the process of power generation from the city or town to the community level. But why not take that a step further? Instead of having one big wind turbine to supply 1000 homes, why not give each home its own small wind turbine and let it make its own power? That's the basic idea of micro-wind turbines—scaled down versions of the towering turbines in wind farms.
