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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: 5, Interesting) by Runaway1956 on Friday September 04 2015, @12:46AM
I've always thought that solar and wind were complementary systems. You install the solar for semi-reliability, and the wind is a kind of backup system. That is, when you get the least solar, is when you are probably getting the most wind, and vice-versa. Installing them side by side should ensure that you never need the grid again.
(Score: 0) by Anonymous Coward on Friday September 04 2015, @12:57AM
That's just insane thinking. Obviously, there must be one single best choice that will work at all times in all places and if we spend any resource pursuing other energy sources we're fools.
(Score: 2) by subs on Friday September 04 2015, @01:05AM
you are probably getting the most wind
That's the crucial word. What happens when you get least solar and the wind goes away, sometimes for weeks at a time?
(Score: 2) by Runaway1956 on Friday September 04 2015, @01:35AM
Sounds like a regional thing to me. In the temperate zones, overcast skies go hand in hand with storms and high winds. Bright sunshiny days are generally calm days. Sure, there are exceptions to every rule, but those exceptions don't seem to last for weeks at a time.
Of course, for redundancy, you can stay attached to the grid, and sell your excess electricity when you have it, then pull in electricity when you need it. There are claims that people actually pocket money doing this. Alternatively, you can keep a traditional generator ready, to fill in when nothing else works.
Bottom line, if you have money to invest in your own infrastructure, you really ought to look at multiple sources of electricity. Remember, TANSTAAFL. Energy costs, no matter what approach you take to exctract energy from the environment.
People who live in regions such as you describe need to balance their options, and go with the alternative that is most likely to meet their needs. If that means staying on the grid, then that's what they need to do. No single source of energy is likely to prove "best" for everyone in the world.
Well - not until we have reliable, cheap cold fusion, anyway.
(Score: 2) by subs on Friday September 04 2015, @07:57AM
Sounds like a regional thing to me. In the temperate zones, overcast skies go hand in hand with storms and high winds. Bright sunshiny days are generally calm days. Sure, there are exceptions to every rule, but those exceptions don't seem to last for weeks at a time.
Unfortunately, they exist and they're not rare either. See for example this study [fraunhofer.de]. On page 40 you can see daily production from the whole of Germany. Between Feb and March you can see a week long period when output drops by nearly 90%. Then it happens again at the end of March. Interspersed are 2-3 day periods of similar low production. At other times, there are days when production is easily 20x that low. There is no storage system on the planet that can deal with this kind of intermittent production and mind you, this is data averaged over all of Germany, not just one locale. Locally, it'd be much, much worse.
Alternatively, you can keep a traditional generator ready, to fill in when nothing else works.
Besides on-demand generation being usually very dirty, you'll also be running it a good portion of the time, largely offsetting the benefit you're getting from the renewable source. Until the intermittency problem is solved, wind & solar can only ever be of benefit on the periphery. You'll still need reliable low-carbon baseload production and ATM that's only nuclear or hydro (where resources are available - unfortunately, in places like Germany, they're pretty much all exploited already).
(Score: 2, Informative) by stingraz on Friday September 04 2015, @01:53PM
Between Feb and March you can see a week long period when output drops by nearly 90%. Then it happens again at the end of March. Interspersed are 2-3 day periods of similar low production. At other times, there are days when production is easily 20x that low. There is no storage system on the planet that can deal with this kind of intermittent production and mind you, this is data averaged over all of Germany, not just one locale. Locally, it'd be much, much worse.
That can happen at the scale of a country like Germany, yes. However, The European power grid is fairly well integrated at a scale much larger than this; the UCTE continental synchronicity zone spans an area from Portugal to Turkey, and from Italy to Denmark. Significant power flows (at multi-gigawatt levels) are possible within that zone, and the EU is pushing for a further buildout of cross-border transmission capacities, which should happen in the next 10-15 years. This should increase transmission capacity into and out of Germany alone by around 100%. Connections to the Nordic zone (Scandinavia) and the British Isles are also available today in multi-gigawatt capacities, and further buildout to connect either to (mostly) Norway better is happening as we speak.
Wind power becomes much more evenly available once your grid spans more than 1500km (~1000mi) in all directions (research shows that wind power aggregates over all of Europe + North Africa would virtually guarantee that power output never drops below ~30% of rated power, and rarely exceeds 50% either). This is directly linked to the size of low-pressure systems, which is to say that solar output will basically correlate in an inverse way to wind power.
Viewing a system the size of Germany is too narrow-minded a perspective; the current scale of most existing continental power grids is already beyond that, and future developments make your point even more moot. The main obstacle seems to be the people that oppose transmission capacity (line) construction in the mistaken belief that this would not be necessary for "decentralized" renewable energy scenarios, when in fact it's quite the opposite.
(Score: 0) by Anonymous Coward on Friday September 04 2015, @04:06PM
That's why you have things like regional grids...like we already have. Granted decentralized power generation through multiple sources would essentially nullify this especially once we move more to an onsite generation model. But hey why let things like intelligent infrastructure design come into a pedantic discussion about how evil renewable energy is.
(Score: 2) by Joe Desertrat on Friday September 04 2015, @02:15AM
My thinking is we need to get away from the idea of centrally produced power. Ideally, homes and developments would be built to best take advantage of solar and whatever other local sources are appropriate, with local co-ops using small generating plants to make up for any individual shortages. More efficient, better for the environment, will cost a whole lot less in the long run. Of course, big power will fight this tooth and nail, and I'm sure they will work to put every legislative impediment in the way.
(Score: 3, Informative) by Phoenix666 on Friday September 04 2015, @12:51PM
I share your philosophy. Enough with central control over every central aspects of our daily lives. Want to get to work? Pay Big Oil. Want to switch on the light in your room? Pay Big Power. Their abuse never stops, because they have everyone by the balls.
We have the technology now to put an end to it and them once and for all. So let's get on with it.
Washington DC delenda est.
(Score: 1, Informative) by Anonymous Coward on Friday September 04 2015, @04:35AM
> That is, when you get the least solar, is when you are probably getting the most wind, and vice-versa.
Not so much. Wind tends to die off at night. Wind is driven by temperature differentials and without the sun to add heat to the ground creating a differential it all dies off. It is pretty dramatic - here is this week's data for a weather-station near me. [newsday.com] Look at the 3rd graph labeled "wind speed/wind gust" you can see how each day the wind starts at around 8:30AM and stops around 9PM - which is about 2 hours offset from sunrise and sunset (currently 6:30AM and 7:15PM at that location).
Of course that phenomenon is not universally true, but it is the norm. Some areas of geography have more consistent wind, especially near bodies of water because water holds heat much better than earth so when the sun goes away, the earth cools but the water stays warm and thus you get a breeze. Other factors include height (not necessarily altitude) the higher off the ground, the more wind.
(Score: 2) by Runaway1956 on Friday September 04 2015, @02:09PM
KCALOSAN That would be coastal California? Uh-huh - I guess I should have known better. Coastal regions have their own weather patterns, and I didn't think about that at all. I don't know where to look for a similar chart, but each day, I look at the local weather from NOAA in DeQueen, Ar. We generally get a little breeze in the evenings, and it lasts most of the night.
OH NOES! Weatherunderground says I'm full of shit, and don't know what I'm talking about!
Well, not exactly, but my local chart resembles the chart you link to. Hmmmm - now I need to look at things and figure out where I've gone wrong.
Thanks for posting, man!
(Score: 0) by Anonymous Coward on Friday September 04 2015, @04:33PM
> KCALOSAN That would be coastal California
That is right in the middle of the san fernando valley. Coastal, being near a body of water, would tend to have sustained winds even at night.
(Score: 2) by RedBear on Friday September 04 2015, @07:32AM
Hey man... Hey. Are you... Are you feeling alright?
¯\_ʕ◔.◔ʔ_/¯ LOL. I dunno. I'm just a bear.
... Peace out. Got bear stuff to do. 彡ʕ⌐■.■ʔ
(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.