While wind power is talked about as the power source that will get us off fossil fuel, as a renewable energy source, wind energy has one big flaw: even in the windiest of places, the wind does stop. Variable wind speeds timed at the same time of day that our demand for power spikes (afternoon) and the reduced efficiencies it presents is one of the biggest obstacles for the industry to expand as many would like to see.
The University of Wisconsin-Milwaukee has received a $422,266 grant from the U.S. Department of Energy for a project that may help improve the efficiencies of wind turbines. This first phase of research is to study ways to make wind turbines work better and improve the stability of power sent to the grid with varying wind speeds. The team is looking at mechanical changes to current gearbox technology.
It is interesting to note that European turbine manufacturers build turbines based on a direct-drive to get around the frequent need to replace gearboxes. It is reported that the direct-drive makes for a quieter turbine, since they produce no mechanical or tonal noise. It can also limit output during the night when the wind is up but power demand is low. The generator operates at a varying frequency, directly proportional to the rotor speed. A converter modifies this variable frequency output to a fixed frequency corresponding to the grid frequency.
BWEA is a good source for information on the industry in the UK. Read more about direct-drive turbines and wind turbine noise.
Comments
Existing wind machines are operating close to the Betz efficiency limit. A useful improvement would be to use two blades instead of three so the power head could be hauled to a shop for maintenance. The inability to easily do shop major-repairs limits both the life and utilization of windmills.
The real "renewable energy" efficiency need is to figure out how to make backup power as efficiently as base load power. According to CA ISO, Spain, and US DOE, wind machines run roughly 20% of the time. That meaans backup power runs 80% of the time.
Wind machine backup power is typically simple cycle gas turbines, AKA airplane motors. These are roughly 35% efficient, burning natural gas. They can be any size.
Alternate to owning any wind machines, a utility can install CCGT, essentially "airplane motors" firing into boilers. These are 45% efficient, but break when quickly shut down.
80%/35% > 100%/45%. Until this "efficiency" is problem fixed, wind energy is almost useless.
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