From the Wind energy: On the grid, off the checkerboard
WASHINGTON D.C., April 1, 2014 — As wind farms grow in importance across the globe as sources of clean, renewable energy, one key consideration in their construction is their physical design — spacing and orienting individual turbines to maximize their efficiency and minimize any “wake effects,” where the swooping blades of one reduces the energy in the wind available for the following turbine.
Optimally spacing turbines allows them to capture more wind, produce more power and increase revenue for the farm. Knowing this, designers in the industry typically apply simple computer models to help determine the best arrangements of the turbines. This works well for small wind farms but becomes less precise for larger wind-farms where the wakes interact with one another and the overall effect is harder to predict.
Now a team of researchers at Johns Hopkins University (JHU) has developed a new way to study wake effects that takes into account the airflow both within and around a wind farm and challenges the conventional belief that turbines arrayed in checker board patterns produce the highest power output. Their study provides insight into factors that determine the most favorable positioning — work described in a new paper in the Journal of Renewable and Sustainable Energy, which is produced by AIP Publishing.
This insight is important for wind project designers in the future to configure turbine farms for increased power output — especially in places with strong prevailing winds.
“It’s important to consider these configurations in test cases,” said Richard Stevens, who conducted the research with Charles Meneveau and Dennice Gayme at JHU. “If turbines are built in a non-optimal arrangement, the amount of electricity produced would be less and so would the revenue of the wind farm.”
How Wind Farms are Currently Designed
Many considerations go into the design of a wind farm. The most ideal turbine arrangement will differ depending on location. The specific topology of the landscape, whether hilly or flat, and the yearlong weather patterns at that site both dictate the specific designs. Political and social considerations may also factor in the choice of sites.
Common test cases to study wind-farm behavior are wind farms in which turbines are either installed in rows, which will be aligned against the prevailing winds, or in staggered, checkerboard-style blocks where each row of turbines is spaced to peek out between the gaps in the previous row.
Staggered farms are generally preferred because they harvest more energy in a smaller footprint, but what Stevens and his colleagues showed is that the checkerboard style can be improved in some cases.
Specifically, they found that better power output may be obtained through an “intermediate” staggering, where each row is imperfectly offset — like a checkerboard that has slipped slightly out of whack.
This work was funded by the National Science Foundation (grant #CBET 1133800 and #OISE 1243482) and by a “Fellowship for Young Energy Scientists” awarded by the Foundation for Fundamental Research on Matter in the Netherlands. The work used XSEDE (NSF) and SURFsara (Netherlands) computer resources.
The article, “Large Eddy Simulation studies of the effects of alignment and wind farm length” is authored by Richard J. A. M. Stevens, Dennice F. Gayme and Charles Meneveau. It will be published in the Journal of Renewable and Sustainable Energy on April 1, 2014 (DOI: 10.1063/1.4869568). After that date, it can be accessed at: http://tinyurl.com/n9o282o
Regardless of anyone’s views on AGW, pushing efficiency of energy production should be a goal we can all agree on.
Absolutely correct. I’ve become skeptical of the global warming story for a number of reasons, but the misuse of climate modeling by no means invalidates modeling, science, or engineering. It dictates humility, ongoing inquiry, rigorous integrity, and the willingness to re-engineer.
I have mixed feelings about wind turbines. I think they’re eyesores and therefore should be sited in places with lots of wind but without scenic value. Most of North Dakota comes to mind. There are other places as well. And while they’re of limited utility with respect to providing baseload, they can be a very cost effective supplement.
http://www.eia.gov/forecasts/aeo/pdf/electricity_generation.pdf
The same applies to solar power if, and only if, it’s deployed at low latitudes in sunny places. Rooftops in the American Southwest come to mind. Also, solar hot water heating can be very effective, and far cheaper than PV cells, as well as useful at much higher latitudes. And ground-source heat pumps are an excellent way to improve the efficiency of HVAC systems.
None of these things need conflict with skepticism of global warming. True, some of the eco-fakers take them too far, and they need to be resisted, but with facts rather than reflexive bile. There shouldn’t be any resistance to the most efficient use of resources wherever they come from.
And some physics to explain why windmills are eternally inefficient:
“Betz’ law (Year 1919) says that one can only convert not more
than 16/27 (or 59%) of the kinetic energy in the wind to
mechanical energy using a wind turbine.”
Oh please. Only 59% efficient? That’s a GREAT number if true. Compare it, if you will, to the efficiency of an internal combustion engine, which sends more than 75% of the energy content of gasoline into the air as heat and vibration. We tolerate this because of the extraordinary energy density, portability, and relative cheapness of gas. But it’s terribly inefficient.
Electric vehicles are much, much more efficient, converting at least 75% of the electricity at the plug into motive power even after losses in conversion and storage. The issue there is the low energy density and high cost of batteries.
Battery technology remains relatively primitive, but even primitive lithium-ion batteries will soon make electric commuter cars a viable mass-market proposition. Stick a 60 kWh battery in a car and find a way to make that battery for $5,000 and you’re off to the races. I think that’ll happen through a combination of manufacturing scale economies and reduction of rare earth materials.
If there are further breakthroughs, the advantages of electric motive power will become unmistakable and undeniable. None of this is one bit incompatible with skepticism with respect to (what I see, anyway) as the collapsing AGW hypothesis.
One point that wind plant proponents always seem to forget is this. If you have a wind power plant it is taking energy out of the wind (energy can only be in one place at one time). That is going to affect weather patterns as in change the climate. Do you see the hyprocrisy here? To stop climate change we need to use wind power that will cause … climate change. By the way if wind power is not affecting weather patterns, then it is not extracting enough energy to make any useful contribution to energy production anyway so it is only killing birds and bats.
“…into best arrangement of wind turbines on large installations.”
The best arrangement for securing more tax credits and government subsidies?
Greg says:
April 1, 2014 at 3:16 pm
A windmill is a windmill.
A turbine in reality is a fancy name for a machine that employs the Brayton cycle.
To call a windmill a turbine is disingenuous at best.
Jake J says:
April 1, 2014 at 7:48 pm
======================
I’ve seen electrics outrun NASCAR cars in one lap because they generate maximum torque at any speed. However, that battery thing is still a problem. When the all knowing gubmint finally puts 100,000,000 electrics on the road, I’m going to get a big box of popcorn and an adult beverage, pull up a chair in the cool evening air, and watch the sky light up when 100,000,000 chargers kick on. Should be quite a show for at least a few seconds. The view from space should be fantastic watching all those HV lines melt. Shutting down power plants and exponentially raising the demand is a stroke of pure genius.
Jake J,
The focus of battery research for the last hundred years has been smaller, lighter, and higher capacity. However, after a hundred years of development, there is still nothing that can beat yea olde lead acid battery for charge/discharge cycle lifespan for rechargeable batteries. This is why Lead acid batteries are still the go to storage medium for uses where weight and bulk don’t matter such as building level backup power.
A truly practical electric car requires a major change in the direction of batter research.
Here are the things that I would look for to call an all electric car practical:
1. Range equivalent to similar size / category gas cars. Getting close but not quite there yet.
2. Recharge time no more than 2-3 times what it takes to fill the gas tank on a similar size / category gas car. Recharge stations as ubiquitous as gas stations. Current tech is nowhere near this one. I do a couple of trips a year where it takes 2 or more tanks of gas to reach my destination, overnight charging after 200-300 miles is not acceptable.
3. Battery lifespan similar to the lifespan of the car’s chassis. How often do you hear about someone having to replace the gas tank on a 10 year old car.
What you need to convince me to actually buy an electric vehicle:
1. All of the above in SUV or Pickup class vehicle with minimum 7000lb tow capacity.
2. Must match the range of the gas version at max tow capacity as well as empty.
3. Price premium over equivalent gas vehicle no more than 5%.
“”””””……Box of Rocks says:
April 1, 2014 at 8:25 pm
Greg says:
April 1, 2014 at 3:16 pm
A windmill is a windmill…….””””””
I have always considered the word turbine, to apply only to the mechanical contrivance that converts the energy of a moving fluid, into rotary motion of a mechanical shaft.
This definition fits the description of that mechanism at the back end of a “jet” engine, aka a gas “turbine”, and also the device in the exhaust of an ICE, that is used to drive a “turbocharger”, and it fits the device that is water driven, and is used to rotate an “alternator” in a hydro-electric power station.
So in my view, a windmill is simply a turbine that is used to drive a grain grinding machine (mill) ; but it is still a “turbine.”
Well a lot of “windmill” turbines, are actually driving crude reciprocating pumps for well water.
So where’s the disingenuity, in calling a windmill, a turbine.
As for those huge “wind turbines”, they are just fancy windmills, that are also used to drive an alternator, to generate electricity. I’m sure they also do some grinding on the gears in their gear boxes, because of the rotary and axial oscillations of the windmill propeller blades due to vertical wind shear. They eventually shake themselves to pieces.
Why doesn’t Large Eddy get an author credit when they were his studies?
Green energy waste steam of rare earths tosses away enough Thorium yearly to power the entire planet. Building bird blenders makes no sense on energy efficiencies, densities, 24×7 power, blight of hillsides, human impacts and only by government subsidies.
“””””…..James the Elder says:
April 1, 2014 at 8:44 pm
Jake J says:
April 1, 2014 at 7:48 pm
======================
I’ve seen electrics outrun NASCAR cars in one lap because they generate maximum torque at any speed. …..”””””
Well actually, electric cars generate maximum torque, only at zero speed, with the rotor stalled.
Once they are moving, the electric motor becomes a generator, producing a back EMF that opposes the applied Voltage; so the torque must drop, since it is directly proportional to the current flow. Unless you have some fancy variable Voltage battery, that raises the applied drive Voltage, with the rotor RPM, you can’t maintain the maximum rotor current once it is rotating.
None of which refutes your statement that an electric can outrun a NASCAR auto in one lap.
per Jake J
“””””…..Electric vehicles are much, much more efficient, converting at least 75% of the electricity at the plug into motive power even after losses in conversion and storage. The issue there is the low energy density and high cost of batteries.
Battery technology remains relatively primitive, but even primitive lithium-ion batteries will soon make electric commuter cars a viable mass-market proposition. Stick a 60 kWh battery in a car and find a way to make that battery for $5,000 and you’re off to the races. I think that’ll happen through a combination of manufacturing scale economies and reduction of rare earth materials…….”””””
So what are we converting to “motive power” ? The electricity available at the battery “plug”, or the electricity available at the plug in the garage, that feeds the battery charger ??
When you say conversion and storage, that to me implies that your 75% includes the house AC to DC conversion, the charging efficiency of the battery, and the battery to electric motor, and transmission losses.
The Tesla model S has a gear train, including a differential, just like an ordinary auto has, although their gear train is apparently just a fixed rpm step down conversion. I assume their differential is at about 92% efficiency, just like other autos.
Today’s computer power supplies are at about 85% efficiency, and I don’t see that going up, if you raise the power to 60 KW which would take over an hour to charge your 60 KWh battery. I don’t know what the charge-discharge efficiency is for Li-ion batteries, but my laptop batteries get quite hot, so I doubt they are very high recycle efficiency (like >90%).
But why ignore all that nastiness that goes on at the coal fired power plant.
And what to rare earths have to do with battery technology ??
Want to meet spivs?
Go to a wind “farm” (dis)information day.
Roger Sowell Apr 1 6:46pm says “[Buffett] has never purchased a nuclear utility even when they were the darlings of the utility industry. He could have, but he did not. Surely, that says volumes about the profit potential of nuclear power plants.“. There’s often an alternative explanation. Buffett only invests in businesses he understands.
However, that battery thing is still a problem. When the all knowing gubmint finally puts 100,000,000 electrics on the road, I’m going to get a big box of popcorn and an adult beverage, pull up a chair in the cool evening air, and watch the sky light up when 100,000,000 chargers kick on.
That’s just foolish. An electric car recharges on an electric dryer circuit. If every car was electric (something that wouldn’t happen for 50 years at the very least), the total electricity demand would grow 20%. If THAT many people charged ’em at once, those telephone pole transformers might need upgrades. No biggie.
@Matt S, the market for electric cars is not going to be all-or-nothing, Very few things are. It started with hard-core geeks 20 years ago. Now it’s early adopters, the curious, and status-seekers, i.e., the Tesla Model S buyers.
Stick a 60 kWh gas tank in the vehicle, and make it cheap enough, and the next segment will be second-car commuters. Not all of them, but a much bigger segment than today. (A 60 kWh battery will deliver a rock-sold 140-mile practical winter range in 90% of the United States, “practical” meaning how far it’ll go on 80% of the battery’s power.)
Your requirement is for a does-everything car, i.e. one you can take out of town. I completely agree with your specifications for such a vehicle, and think it’ll be a long time before electrics can fulfill them. But there are 250 million passenger vehicles out there; 35% of households own two vehicles, and 20% own three or more.
There is definitely a market for shorter-range commuter cars. Electrics aren’t quite there yet, but they are close. Because of their efficiency, electric drivetrains get 3 to 3.5 times the fuel economy as gasoline. The fuel is cheaper, and the mechanics are far simpler and cheaper (no oil changes; engines much simpler; no transmissions; no exhaust systems). The issue is the expense of the gas tank, and the low energy density of the battery. Period.
I’ve followed electrics closely. I am not an “EVangelist” but rather a rock-hard realist about them.
When you say conversion and storage, that to me implies that your 75% includes the house AC to DC conversion, the charging efficiency of the battery, and the battery to electric motor, and transmission losses.
All of that except for transmission losses, which are 6-7%. I don’t include them because to include electricity transmission losses would require including the energy expenditure in moving gasoline from refineries to pumps. I don’t know that number, or where to find it. Therefore, when comparing efficiency I compare gas pump to wheels to electric outlet to wheels.
But why ignore all that nastiness that goes on at the coal fired power plant.
I don’t. What I do, however, is think about how we generate electricity in this country.
– 39% coal
– 28% natural gas
– 19% nuke
– 7% hydro
– 4% wind
– 3% other (solar, biomass, geothermal, oil)
Over time, coal will go down towards 30% and natural gas will rise toward 35-40%. Wind will rise toward 10%. Solar will rise toward 5%.
And what to rare earths have to do with battery technology ??
Rare earths have been a required component of lithium-ion batteries, but the amounts are steadily declining. If you believe press releases (a big “if”), rare earths might be eliminated entirely, which would make batteries somewhat cheaper.
One other thing I’d point out. The only reason diesel train locomotives are diesel is because batteries are so weak relative to hydrocarbon fuel energy density. The diesel engines don’t power the wheels; that’s done by electric motors because of their torque. The diesel engines run generators that feed the electric motors that turn the wheels.
The point to explaining this is that electric transportation has been around for a very long time. The issue has ALWAYS been that batteries can’t hold enough juice. That’s changing for cars. We’re getting very close to the point where electricity will peel away a substantial segment of the car market.
If batteries ever do get the energy density of gas or diesel, at a reasonable cost, there’d be no reason to burn petroleum distillates in cars and trucks. And this would have absolutely nothing whatsoever to do with whether or not (probably not, in my view) the AGW hypothesis is true.
Jake, electric cars for short journeys are a technology that may come – the problem is, as you have clearly stated, the batteries. But it is not just the capacity that is the issue (in fact that is a minor issue for short ranges), the problem is the longevity of the battery pack and the enormous cost, both financial and in natural resources, of replacing them every few years.
And I already know the best arrangement for wind turbines. It’s in a scrapyard, lined up side by side, waiting to be recycled into something useful.
Bertram, we’ll see what the longevity winds up being. Near as I can tell, after 100K miles a lithium-ion battery will have 80% of its original capacity, so I think a full life will approach if not equal that of the car. I don’t particularly worry about natural resource costs, if rare earths can be reduced or eliminated. But yes, cost is a big issue.
Journal of Renewable and Sustainable Energy
Are these windmills renewable?
Not really, they are made of:
Steels.
Concrete,
Carbon fibre.
As far as I am aware, concrete is not recycled into new concrete.
Carbon Fibre blades are not recyclable.
Steel or metals of various types can be recycled at a cost.
Energy use in construction and the small amount of recycling of these devices.
Cement uses lots of electricity in its manufacture.
Carbon Fibre is oil based.
How, in any way shape or form, can windturbines be called renewable or efficient?
@redc1c4
There is one peculiar feature of the USGS Wind Turbine Map I can’t comprehend.
Why former Confederate States are almost completely free of these industrial devices while the rest of the country is infested by them? Can anyone help me out on this puzzle?
It seems David Cameron is turning against wind farms, at least the onshore variety. According to a report in today’s Telegraph, he wants to go into next year’s general election with a pledge to virtually stop further onshore wind farms. It even mentioned the possibility of some wind farms being dismantled.
Well, that’s a step in the right direction.
Another extraordinary report in the Telegraph: apparently the House of Commons Climate committee wants the BBC’s climate coverage to be more balanced. That should bring a smile to any sceptic’s face. But wait a minute. They seem to think that the BBC is biased in *favour” of the sceptics, and that the BBC’s coverage should be more pro-global warming/AGW.
Absolutely unbelievable and sickening in equal measure. Do these morons really think that the Guardian’s broadcasting arm is on the side of the sceptics? This really takes the biscuit!
Chris
john says:
April 1, 2014 at 3:20 pm
Edit: Reduce should be ‘increase’.
It will [reduce] the fuel you use substantially (efficiency), AND more importantly, beat the hell out of you car.