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  (Source: Treehugger)
Raising the cut-in speed to 11 mph could result in as much as a 93 percent reduction in bat-turbine related deaths

Wind power has become an important competitor in the race for clean energy, but like many newer developments, it needs some work. One issue associated with wind power is bat and bird-related fatalities due to the spinning blades of the turbines. However, researchers may have solved this problem with a slight change in speed

Edward Arnett project leader from the Bat Conservation International in Austin, Texas, along with John Hayes, co-author of the study from the University of Florida, have studied bat fatalities associated with wind turbines and concluded that altering the speed slightly would reduce a large percentage of these deaths.

Wind turbines within the United States are programmed to start producing power when wind speed reaches 8 or 9 mph. The speed at which wind turbines begin producing power is the cut-in speed, and those with a low cut-in speed tend to run more often than those with a high cut-in speed because they begin running at lower speeds in the first place. 

Arnett, Hayes and their research team recorded bat fatalities while observing 12 out of 23 turbines at the Casselman Wind Project in Somerset County, Pennsylvania. They stayed for 25 summer and fall nights in 2008 and 2009 (because wind speeds are low this time of the year), and found that the less time a wind turbine is running, the better because bats cannot be harmed by blades that aren't in motion. Following this logic, Arnett suggests raising the cut-in speed of wind turbines to 11 mph, which would result in a reduction of bat fatalities by approximately 44 to 93 percent and an annual power loss of less than one percent. 

"This is the only proven mitigation option to reduce bat kills at this time," said Arnett. "If we want to pursue the benefits associated with wind energy, we need to consider the local ecological impacts that the turbines could cause. We have already seen a rise in bat mortality associated with wind energy development, but our study shows that, by marginally limiting the turbines during the summer and fall months, we can save bats as well as promote advances in alternative energy."

Arnett notes that reducing bat fatalities is essential because bats help with pollination and pest management, making them an important part of ecosystem health nationwide. 

"Rarely do you see such a win-win result in a study," said Arnett. "There is a simple, relatively cost-effective solution here that could save thousands of bats. This is good news for conservation and for wind energy development." 

This study was published in Frontiers in Ecology and the Environment on November 1.



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By smartalco on 11/3/2010 1:48:55 AM , Rating: 2
quote:
And from one of my family members who is an environmental biologist working with oil companies to maintain the raptor population in the northern plain states

Wat?

I'd also be curious as to how exactly they decided that increasing the start speed from 8mph to 11mph only decreased production by 1%


By chromatix on 11/3/2010 6:40:52 AM , Rating: 2
Raptor: bird of prey.

I suspect that the logic includes the low yield of turbines running in low wind speeds. Less wind, less power available. Cutting out the lower speeds could indeed have a smallish effect on total power generation while having a disproportionate benefit in terms of reduced duty cycle.


By Calin on 11/3/2010 7:52:35 AM , Rating: 2
First of all, depends very much on the wind speed in the area. The energy contained in wind depends with the cube of its speed (energy is half the mass multiplied by the speed squared, and mass thru turbine working area varies with velocity).
Assuming the efficiency of the turbine is the same at all speeds, you have the power available at 8, 9, 11 and 50 mph wind speed growing about from 1 to 1.4 to 2.6 to 244 (that is, a wind turbine that is equally efficient at 8mph and 50mph wind speed would produce about 250 times more power at 50 mph wind speed). Realistically, wind turbines are not really optimized for the very low wind speed (as there isn't much energy to be harnessed anyway) and the friction losses are disproportionate at very low wind speeds, and you get a lower power at 8mph wind speeds that what the above ratio suggests.
So, increasing the cut in speed in many cases might be almost free of energy cost, and it might reduce the working time and so increase the maintenance intervals. And if this 90+ reduction in bats killed is true, this might allow installation where a higher total efficiency turbine would be forbidden.


By Calin on 11/3/2010 7:52:47 AM , Rating: 2
First of all, depends very much on the wind speed in the area. The energy contained in wind depends with the cube of its speed (energy is half the mass multiplied by the speed squared, and mass thru turbine working area varies with velocity).
Assuming the efficiency of the turbine is the same at all speeds, you have the power available at 8, 9, 11 and 50 mph wind speed growing about from 1 to 1.4 to 2.6 to 244 (that is, a wind turbine that is equally efficient at 8mph and 50mph wind speed would produce about 250 times more power at 50 mph wind speed). Realistically, wind turbines are not really optimized for the very low wind speed (as there isn't much energy to be harnessed anyway) and the friction losses are disproportionate at very low wind speeds, and you get a lower power at 8mph wind speeds that what the above ratio suggests.
So, increasing the cut in speed in many cases might be almost free of energy cost, and it might reduce the working time and so increase the maintenance intervals. And if this 90+ reduction in bats killed is true, this might allow installation where a higher total efficiency turbine would be forbidden.


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