by John Spears, Toronto Star
For better or worse, wind turbines have become the symbol of renewable energy in Ontario because of their sheer physical presence. After hydroelectric power, they’re also the main producers of renewable electricity in Ontario. Here’s how they work.
The structure: Big turbines need a firm anchor. That means a reinforced concrete base up to five metres in diameter. A crane then lowers the main tower into place. Towers are made of rolled steel, concrete or a mixture of the two. They’re usually built in three sections. When fitted together, the larger towers reach about 80 metres high, although the biggest towers can go up to 100 metres.
Sitting atop the tower is the nacelle — the cone-shaped apparatus that acts as the hub for the blades. The nacelle houses the generator itself, along with a braking system to keep the turbine from spinning too fast. It also houses a “yaw drive” that turns the nacelle so it’s facing directly into the wind. The nacelle can rotate 360 degrees.
The turbine blades are made of fibreglass or carbon fibre. They’re up to 45 metres in length, so they reach up to 125 metres above the ground at the top of their sweep.
The power output: Output depends on the size of the turbine. The turbine at Exhibition Place in Toronto is small by today’s standards, producing 750 kilowatts of power at full speed.
Many big turbines now being erected in Ontario are produce up to 2.5 megawatts. Offshore turbines can be even bigger.
Location and spacing: Generally, developers try to scatter the turbines so they’re not directly behind each other when the prevailing winds are blowing. If they are directly in line, they need to be 10 turbine blade lengths apart to avoid turbulence. If they’re staggered, three to seven blade lengths is sufficient spacing.
Economics: A turbine with a feed-in tariff contract receives 13.5 cents a kilowatt hour, or $135 a megawatt hour for its output. (One megawatt is 1,000 kilowatts.)
A two-megawatt turbine running at full speed, 24 hours a day for a year, would therefore produce 17,520 megawatt hours of power. Assuming it operates at 35 per cent capacity, in the real world it will produce about 6,132 megawatt hours.
At $135 a megawatt hour, that means revenue of $827,820 annually.
Assuming a more conservative capacity of 27 per cent, it would generate revenue of $638,604.
Offsetting the revenue are very high capital costs. The cost of purchasing, erecting, financing and connecting a turbine runs at about $2,500 a kilowatt of capacity, although prices are declining and in some cases are now below $2,000 a kilowatt, according to CanWEA. That means a two-megawatt turbine costs $4 million to $5 million to install. Included in the cost is rent of more than $19,000 a megawatt — paid to the landowner where the turbine is erected. That works out to about $38,000 annually for a two-megawatt turbine.
Not counted in these costs is the price of having backup plants standing by to fill in the gaps when wind speeds oscillate or die. Increasing numbers of wind turbines require more quick-starting, gas-fired generating stations, which are paid to be on standby even if they’re not operating.