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Imagine That Wind Energy and Birds All human activity affects natural surroundings, and renewable energy is not without environmental impacts. These impacts are only meaningful in comparison to the alternatives. The threat of wind turbines to birds and other wildlife is very small when compared to impacts of traditional energy sources. Leading studies find wind energy has a tiny impact on birds. Only .01% of human caused bird fatalities can be attributed to windpower..

Why wind and power depends on petroleum and natural gas

You need a good breeze, of course, but there’s

wind farms in the US

something else that’s essential, something that you might not associate with wind power. And that something, would be oil or natural gas. Yep. Wind power depends on the hydrocarbon. That’s because inside those turbines are gears, axles, a generator – all sorts of moving, turning parts – and moving parts need lubrication – and lubrication means oil. Which shouldn’t be surprising. Petroleum products are in all sorts of other products, including other sources of energy. And those moving parts? The windmill blades have been getting longer and longer, which is good for the work of catching the wind – but the only way to make blades like that, is through carbon-reinforced resins made from petrochemicals. Wind power in the U.S. produces about 5.5% percent of our electricity these days, so long as you’ve also got the oil to keep those turbines lubricated and running (and to make those windcatching blades). The Worlds Largest on Shore Wind Turbines

The GE 4.8-158 turbine’s rotor diameter is more than one-and-a-half American football fields. Each blade is as long as the entire wingspan of a Boeing 747 and would take the average human two minutes to walk end to end.

They Call the Wind Mariah

Southwest Minnesota, has become known for its efforts to generate clean, renewable energy from the wind. The wind towers stand hundreds of feet tall and generate energy on a virtually nonstop basis. This energy is supplied to various electricity providers from all across the nation. Why build wind farms here? This area of Minnesota, called Buffalo Ridge or Coteau de Prairie, is a glacier-deposited ridge that runs diagonally across the state. Because of its higher elevation of 1950 feet, the area experiences continual wind speeds of 18 mph. This and the plentiful open farm and pasture land make it an ideal place for wind turbines. How big are the turbines? To the hub, the turbines are 229 ft. tall with 136 foot blades, meaning the height from the base to the tip of the blade is 365 ft. The bases of the turbines are 11-16 feet in diameter and the foundations, which run 30 ft. into the ground, are 15.6 ft. across. Each wind turbine weighs roughly 1450 tons. How do they work? Wind Turbines operate on a simple principle. The energy in the wind turns two or three propeller-like blades around a rotor. The rotor is connected to the main shaft, which spins a generator to create electricity. How fast do the blades turn? At the optimum wind speed of 25-35 mph, the blades will rotate at 14 rpm. That gives them a speed of 105 mph at the tip. How much electricity do they produce? Each turbine produces about 2,000,000 kilowatt hours (kwh) per year, enough energy to power as many as 500 typical homes at 12,000 kwh per year. How strong do the winds have to blow for the blades to rotate? Wind turbines start operating at wind speeds of around 8 mph and reach a maximum power output at around 33 mph. When there is not enough wind to turn the blades, or when there is too much wind, the turbines shut down. How much do wind turbines cost? It costs over $2.5 million to set up a 1650 KW turbine. How many turbines are there in Minnesota? There are somewhere between 1000 and 1200 wind turbines in Minnesota, with over 200 in Pipestone County alone. Who owns the land the turbines are on? Much of the land is leased from local farmers. Each unit takes up roughly 1/3 of an acre for the equipment and access road. The farmer receives a percentage of the revenue from the sale of the electricity from each turbine. Why just 2 or three blades? The conventional answer to this question is that three blades minimizes the shadow effect that each leading blade has on the blade that follows. You want more blades to reduce the starting torque required to get your turbine spinning (this is analogous to having more cylinders in an engine making it run smoother) but, if you have too many blades, the shadow effect hurts efficiency and drops the total yield. Three blades peak at about 48 percent efficient, which isn’t 59.3 percent (Albert Betz of Germany creeated Betz’s Law,which states that no turbine can capture more than 16/27ths or 59.3 percent of the wind energy passing through the turbine disk). 48% is near enough and happens to be the practical output, so it must be right, right? Put another way, Rotor power (= 2π M n) is proportional to the torque M acting on the shaft and the rotation frequency n. The tip speed ratio λ = vu / v1 from the ratio of tip speed vu of the rotor and the wind speed v1. Optimal tip speed ratio is 7-8 for the three-bladed rotors where they achieve a cp value of 48 percent. Four blade turbines have higher torque but lower tip speed ratios. Turbines with two blades have even higher tip speed ratios but lower torque. In the end, three-blade turbines command the sweet spot and so that’s what are mostly built.

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