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Gregory Meyer reports at CNBC that electricity generated by US wind farms fell 6 per cent in the first half of the year even as the nation expanded wind generation capacity by 9 per cent. The reason was some of the softest air currents in 40 years, cutting power sales from wind farms to utilities and the situation is likely to intensify into the first quarter of 2016 as the El Niño weather phenomenon holds back wind speeds around much of the US. "We never anticipated a drop-off in the wind resource as we have witnessed over the past six months," says David Crane.
Wind generated 4.4 per cent of US electricity last year, up from 0.4 per cent a decade earlier. But this year US wind plants' "capacity factor" has averaged just a third of their total generating capacity, down from 38 per cent in 2014. The EIA (U.S. Energy Information Administration) notes that slightly slower wind speeds can reduce output by a disproportionately large amount. "Capacity factors for wind turbines are largely determined by wind resources," according to their report "Because the output from a turbine varies nonlinearly with wind speed, small decreases in wind speeds can result in much larger changes in output and, in turn, capacity factors." In January of 2015, wind speeds remained 20 to 45 percent below normal on areas of the west coast, but it was especially bad in California, Oregon, and Washington, where those levels dropped to 50 percent below normal during the month of January.
Some also speculate the the increase in the number of wind farms may be having an effect. Since wind turbines extract kinetic energy from the air around them, and since less energy makes for weaker winds, turbines make it less windy. Technically speaking, the climate zone right behind a turbine (or behind all the turbines on a wind farm) experiences what's called a "wind speed vacuum," or a "momentum deficit." In other words, the air slows down and upwind turbines in a densely packed farm may weaken the breeze before it reaches the downwind ones. A study in 2013 also found that large wind farms could be expected to influence local and regional atmospheric circulations. "If wind farms were constructed on a truly massive scale," adds Daniel Engbar, "their cumulative momentum deficit could conceivably alter wind speeds on a global scale."
(Score: 3, Interesting) by Phoenix666 on Friday September 04 2015, @12:47PM
Micro-hydro is another option for those whose property affords them access to water courses. With enough head and step-down pipes you can drive a nice little turbine to supplement what you get with wind and solar. Of course, hydro is vulnerable to drought or flood, as solar is vulnerable to clouds and wind is to wind bursts. But layered together they can work well.
Sufficient battery capacity is key to store enough surplus to get you through troughs. You can still produce more than you need or can store, which is why net-metering on a grid tie is a good thing. Utilities are starting to push back hard on net metering and even residential solar and wind as demand destruction accelerates, though. They have more political clout than all of us yokels, so they will get their way. A fallback is therefore micro-grids you set up with your neighbors. It gives you greater supply smoothing.
If you don't get on with your neighbors you can cover gaps in your supply-demand by reducing your demand. Water heaters and fridges and cable boxes consume the most electricity in most peoples' homes. Swapping the first two out for efficient models will drop your kwh's a lot. The third you can't do much about short of cutting the cable, alas. If you're up for a bolder bid for energy independence, you can switch your HVAC to a ground-source heat pump (GSHP) that also ties into your water heater, such that waste heat from the house is pumped into it. It's common for people who switch to GSHP's to report their energy bills dropping from thousands per year to about a hundred bucks.
Washington DC delenda est.