Wind Turbines by Jacqueline McBride at LLNL

Lawrence Livermore National Laboratory scientist Sonia Wharton and colleague Julie Lundquist of the University of Colorado at Boulder and the National Renewable Energy Laboratory are looking at that issue calling it “stability”.  Their paper appeared in the Jan. 12 edition of the journal Environmental Research Letters, where Wharton and Lundquist examined turbine-generated power data, segregated out the atmospheric stability, to determine the power performance at a West Coast wind farm.

The pair has found by looking at the stability of the atmosphere, wind farm operators could gain greater insight into the amount of power generated at any given time.  The result is surprising; while it seems obvious that power generated at a set wind speed is higher under stable conditions and lower under strongly unsteady conditions, the average wind power output difference is as high as 15% less wind power generation when the atmosphere is unstable.

Wharton said, “The dependence of power on stability is clear, regardless of whether time periods are segregated by three-dimensional turbulence, turbulence intensity or wind shear.”

The pair rolled in time to the research, while turbulence is a relatively well-known term in assessing turbine efficiency, wind shear – which is a difference in wind speed and direction over a relatively short distance in the atmosphere also plays an important role when assessing how much power a turbine generates over certain time scales.

The study offers up a challenge to improve performance.  Wharton and Lundquist show that wind farm operators could better estimate how much power is generated if the wind forecasts included atmospheric stability impact measurements.

The research follows on earlier research that looked at atmospheric stability effects on power output.  But few studies have analyzed power output from modern turbines with hub heights of more than 60 meters, a small unit by today’s standards.

For the new research, Wharton and Lundquist gathered a year of power data from upwind modern turbines (80 meters high) at a multi-megawatt wind farm on the West Coast. They considered turbine power information as well as meteorological data from an 80-meter tall tower and a Sonic Detection and Ranging (SODAR), which provided wind profiles up to 200 meters above the surface, to look at turbulence and wind shear. Looking at upwind turbines removed any influence that turbine wakes may have on power performance.

Mean Seasonal Normalized Power and 80m Nacelle Wind Speed

They also found that wind speed and power production varied by season as well as from night to day. Wind speeds were higher at night (more power) than during the day (less power) and higher during the warm season (more power) than in the cool season (less power). For example, average power production was 43 percent of maximum generation capacity on summer days and peaked at 67 percent on summer nights.

The research at the West Coast location also offered new operational data.  Wharton said, “We found that wind turbines experienced stable, near-neutral and unstable conditions during the spring and summer. But daytime hours were almost always unstable or neutral while nights were strongly stable.”

Lundquist winds up the press release saying, “This work highlights the benefit of observing complete profiles of wind speed and turbulence across the turbine rotor disk, often available only with remote sensing technology like SODAR or LIDAR (Laser Detection and Ranging,).  Wind energy resource assessment and power forecasting would profit from this increased accuracy.”

The ladies have made an important point.  While wind might seem free, leaving 15% of the efficiency out of the performance is a major opportunity for production and profit.  Without a fuel cost the operation expenses and amortization cost can always use reductions and speeding up.  Income per operating hour would be an operator’s watchword so adding 15% to income by increasing output could add market share and a chance to drop rates to consumers.

Thanks to Wharton and Lundquist for a more, better and cheaper potential from wind power.

With funding support from the U.S. Department of Energy through the University of Minnesota Wind Energy Consortium, the Syracuse University’s L.C. Smith College of Engineering and Computer Science (LCS) research team is testing new intelligent-systems-based active flow control methods.

The situation now is the aerodynamic performance of a wind turbine is best under steady wind flow, while the efficiency of the blades degrade when exposed to conditions such as wind gusts, turbulent flow, upstream turbine wakes and wind shear.  Variability of wind offers considerable challenges.

The new Syracuse approach estimates the flow conditions over the blade surfaces from on blade surface measurements, and then uses this information in an intelligent controller to implement real-time actuation on the blades to control the airflow and increase the overall efficiency of the wind turbine system. The work may also reduce excessive noise and vibration due to flow separation.

The Syracuse researchers, Guannan Wang, Basman El Hadidi, Jakub Walczak, Mark Glauser and Hiroshi Higuchi designed and operated a lab simulation.  The initial lab work shows that flow control applied on the outboard side of the blade beyond the half radius could significantly enlarge the overall operational range of the wind turbine with the same rated power output, or considerably increase the rated output power for the same level of operational range.

The measured improvements are significant, suggesting that either the overall operational range of the wind turbine could be effectively enlarged by 80 percent with the same rated power output, or the rated output power could be increased by 20 percent while maintaining the same level of operational range when the control is on. One might envision even smarter software in the controller that could choose which optimization would pay off best in real time. The lab work also shows the optimal location for the actuator is found to be on the outboard of the blade beyond half of the radius.

The Syracuse team has an advantage with a new anechoic wind tunnel facility at SU to determine the airfoil lift and drag characteristics with appropriate flow control while exposed to large-scale flow unsteadiness.  That’s quite a change from a wind tunnel set up to drive airflow at high speed for airplane aerodynamic tests.  The chamber also allows study of the effects of flow control on the noise spectrum of the wind turbine.

Mark Glauser, Professor of Mechanical and Aerospace Engineering at Syracuse said, “This is a wonderful opportunity to transition our expertise in intelligent systems for flow control, developed largely through support from the aerospace sector, to this important and growing area of the renewable energy sector.’’

Scientists at the University of Minnesota, Roger Arndt, Leonardo P. Chamorro and Fotis Sotiropoulos, are looking at another inefficiency with wind energy – the drag, which is the resistance felt by the turbine blades as they beat the air. The team, at the University of Minnesota’s Saint Anthony Falls Lab (SAFL), looked at drag reduction from effect of placing tiny grooves on turbine blades.

The grooves are in the form of triangular ‘riblets’ scored into a coating on the blade surface. They are so shallow (between 40 and 225 microns) that can’t be seen by the human eye – thus the blades look perfectly smooth. Through wind-tunnel tests of 2.5-megawatt turbine airfoil surfaces (becoming one of the popular industry standards) and computer simulations, they have looked at the grooves’ efficacy for various groove geometries and angles of attack (how the blades are positioned relative to the air stream).

The ‘riblets’ suggest a wind turbine efficiency increase of about 3 percent from the surfacing technique.  At these depths, is seems a kind of etching effect on a coating or paint would be the practical technique if the optimal designs can be built with the optimum geometry.

The two new ideas were recently presented at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, Calif. On Nov. 21, the SU research team presented “Benefits of Active Flow Control for Wind Turbine Blades,” and researchers at the University of Minnesota presented “On the skin friction drag reduction in large wind turbines using sharp V-grooved riblets.”

One’s impression from such developing research suggests that the field of moving air or fluid dynamics is getting going on wind turbine research in sophisticated ways.  While 3% efficiency gains doesn’t sound like much, if a cheap application solution comes out, a serious amount of air drive as well as air driven tools could get a worthwhile refit.

But for retrofitting, the Syracuse team’s controller system seems likely to get development and market legs quickly.  The numbers noted above, an operational range increase of 80% would make an enormous difference on wind turbine production.  An assumption for many is that operating time loss is from light or no wind, when in reality highly variable or gusty winds take operating times down in a very significant way as well.

The numbers will vary on geographic location, but that 30% general operating time assumption could quickly become obsolete.  We’ll see if 30% can get to 30 + 24 for an uptime of 54%.  But even getting half, to 42%, would be a massive improvement.

Moore is an aerospace engineer, centering his focus on advance concepts in the Systems Analysis Branch at NASA’s Langley Research Center.  Now he’s set with a $100,000 grant from the federal government to research what it will take to judge the value of tethered winds aloft energy generators.  This is the guy who is setting up the measures for what works best.

Moore explains, “It’s the first federally funded research effort to look at airborne wind capturing platforms. We’re trying to create a level playing field of understanding, where all of the concepts and approaches can be compared — what’s similar about them? What’s different about them, and how can you compare them?”  Useful stuff, getting a set of metrics set up will be critical.  Moore knows the field is just being born comparing wind aloft to powered flight, “this is like being back in 1903. Everybody’s got a dog to show. Everybody’s got a different way of doing it.”

Magenn Power Air Rotor System Graphic. Click image for the largest view.

NASA and Moore are not alone in the regulation of the skies.  The Federal Aviation Administration (FAA) has the power over what goes on overhead.  At the beginning of flight there weren’t crowded skies or an FAA to keep things safely organized.

Moore pints out, “Airspace is a commodity. You have to be able to use airspace without disrupting it for other players. Smaller aircraft are still going to need to fly around. Larger airplanes, you can’t expect them to fly around every wind turbine that has a two-mile radius as a protected flight zone.”

Joby Energy System Illustration. Click image for more info.

Winds aloft generation does deserve some consideration which Moore hastens to say is not THE answer to clean energy, but deserves consideration with most all other forms of alternative power generation.  As of this writing only ethanol has a competitive shot for economical fuel production with fossil fuels.  But as land issues continue to press for food, fiber and fuel, everything else has a shot at the market.  Sound metrics will help everyone make sensible choices.  (More images.)

Winds aloft have some important advantages.  Anchors and tethers for airborne wind generation assets don’t require a lot of ground space, nor are they labor intensive, and they don’t pollute.  Moore sees potential, “They could stay up a year, then come down for a maintenance check and then go back up, or they could be reeled down in case of a storm. Or one operator could watch over 100 of these.”

The main economic point is the power available in a swept area.  Here Moore has some important information to keep in mind.  “At 2,000 feet (610 m), there is two to three times the wind velocity compared to ground level. The power goes up with the cube of that wind velocity, so it’s eight to 27 times the power production just by getting 2,000 feet (610 m) up, and the wind velocity is more consistent.”

Higher up, into the 150 mph (240 kph) jet stream at 30,000 feet (9,150 m), and “instead of 500 watts per meter (for ground-based wind turbines), you’re talking about 20,000, 40,000 watts per square meter,” Moore said. “That’s very high energy density and potentially lower cost wind energy because of the 50-plus fold increase in energy density.”

Another motivator is promoting research in the private sector.  Answers like where the optimal locations are and the kinds of vehicles are prohibitive to small start up companies.  Moore says, “All you have right now are small companies doing the research, and all you can expect of them is to focus on one little piece. They have enough trouble just analyzing their concept without worrying about geography, about ‘where should I mount these so that the wind is optimal?’ ”

The geographical turf is after all the skies above us so it is reasonable to expect that government has a role and acts on it.  Moore realizes the oddness, “that there isn’t federal investment in this area, because the questions are just too great for small companies to answer.”  The wind energy guys are not all out in the private sector.

The grant money is being used to do two things.  One involves the technology and geography. The other involves the interaction between those elements and other competitors for airspace.

That brings us back to the FAA.  It’s going to get complicated.  The regulations of today will need addressed to accommodate an airspace that includes manned aircraft, the unmanned aircraft in the future, plus wind-borne energy turbines.

Here is Moore’s quote, something to have in mind, “It’s important to understand the concept without regulatory constraints because it lets decision-makers and investors understand the topology of the solution space. We don’t want to just look at the problem with regulatory blinders on, but we don’t just look at it with no blinders on, either. We have to look at it both ways.”

Moore has an insight worth some intense examination – “Offshore deployment of these airborne systems probably makes the most sense in terms of both airspace and land use, because there is little to no demand for low altitude flight over oceans 12 miles (19 to 20 km) offshore. Also, unlike ground-based turbines, there is almost no additional cost for airborne systems offshore because huge platforms are not required to support the structure or resist large tower bending moments.”

What all this has to do with NASA involves some of the core capabilities of the agency in aeronautics, composite materials and air space management.  “We’ve shown in the past that NASA’s expertise can help broker and bring an understanding to the FAA as to how these technologies can map into constructive purposes,” said Moore, who has met with wind power energy industry leaders, as well as officials from the National Renewable Energy Laboratory and Department of Energy in undergoing this project.

Moore is offering the FAA NASA’s aeronautical expertise with flying systems.  Moore said. “You can’t come up with advanced concepts until you understand the requirements well, and frankly, I don’t think anybody understands the requirements well.”

That humble honesty points out the fundamental value of the study and why a grant is important – it will get the winds aloft questions a sense of what’s going to be necessary to harvest power from the wind.

There should be a huge opportunity offshore as Moore points out.  For the coast states doubling up on the grant would make great sense.

The only weakness, not a function of study at this time, is the anchor matter and power transmission.  The wave and tidal research has made some progress here.  Perhaps the most interesting thing will be to see the design ideas for wind aloft generation.

Go Mr. Moore.  Lets get some metrics and geography facts in hand and see where this could go.

Honeywell's Blade Tip Windturbine

The company says its turbine has “higher performance output and lower installed cost per kilowatt than any other unit on the market today in class and size.”  The Honeywell Wind Turbine is a gearless wind turbine that measures just 6 feet in diameter, weighs 185 lbs (84kgs) and is able to produce 2752 kWh/yr in Class 4 winds.   The power magnets that flow the electrons are at the outer tips of the blade wheel and inside the shroud around the blade set.

Honeywell's Turbine Comparison. Click image for the largest view.

The Honeywell Wind Turbine’s multi-stage blades allow the system to react quickly to changes in wind speed, ensuring that the maximum wind energy is captured, without the typical noise and vibration associated with traditional wind turbines. It is designed to be installed where power is consumed, allowing home and business owners to harness wind energy in a cost effective and efficient manner.

Class 4 wind is a very large part of North American making a quite large geographical sales area.  The potential is for a volume sales number that coud\ld well drive down the production costs for even more affordability.  And 2700+ kWh a year is worth some effort.

WindTronics decided in 2009 to manufacture the machines in Windsor, Ontario, which has been battered by the auto crisis and recession and suffered from huge unemployment. In that context it was a good-news story because the Michigan-based parent company, EarthTronics, said the facility it was taking over was a former Magna International auto parts plant where 200 new jobs would be created.

The company web site says that the turbine’s installed cost is about half the cost of a traditional small wind turbine. It sells as part of a package that includes a computerized smart box, the inverter and an interconnect switch for wiring the system into a household panel. The MRSP is $6,495US, what Canadian pricing is – isn’t announced. Also not certain is what the installed cost would be, which is important if you want to compare it to, say, putting solar panels on your roof.

From an economics point of view small wind is very hard to justify.  2,700 kWh at say $0.10 isn’t going to get you very far – $270 against perhaps as much as $10,000 up front.  But for sites with need, or little solar potential, expensive grid access and situations where the net meter rate is very good the numbers can change for the better.  That and having one puts surety in service, way out at the end of a rural phase line, weather makes power matter of some concern.

For the money though, and with essentially no volume to start pricing or drive to lower production costs, the Honeywell is a powerful contender.
The other point that many reviewers overlook is the generation parts out in the shroud aren’t moving, nor is the mass moving, nor is the whole airfoil set heavily built to support it all.

That one half mile per hour start speed could have impressive returns as wind class locations of better speeds and more total annual wind time get installations.  At Class 6 and running twice as long the Honeywell is b\going to look much different economically.

If you’re thinking of getting a small wind turbine the Honeywell is a must consider item.

If the WindTronics designs can last as long as the old Aeromotor windmills of old – decades on end, then the Honeywell is a small wind turbine turning point.

Odds are, Dabiri is right.  That would be a bit unsettling for those who can’t grasp wind as a viable alternative energy source.  Its unsettling as the case against wind today is correct – its expensive, has an intermittancy and storage problems.  Wind is good, but problematic.  Increased density would solve part of the transmission line issue and allow closer less costly storage, however that matter comes to maturity.  But without doubt – wind is here to stay, so any piece of the cheaper, better, more reliable issues solved is great news.

Wind harvesting requires substantial land resources in order to extract appreciable quantities of energy. This limitation of land use is especially acute in the case of wind energy, which currently faces an additional constraint in that the conventional propeller-style wind turbines seen in horizontal-axis wind turbines (HAWT) designs must be spaced far apart in order to avoid aerodynamic interference caused by interactions with the wakes of adjacent turbines. This requirement has forced wind energy systems away from high-energy demand population centers and toward remote locations including, more recently, offshore sites.  There’s the transmission issue in a distance illustration.

To get to the 90% of the performance of an isolated HAWT, the turbines in a HAWT farm must be spaced 3 to 5 turbine diameters apart in the cross-wind direction and 6 to 10 diameters apart in the downwind direction. The overall performance of such wind farms, as quantified by the power extracted per unit of land area, is between 2 and 3 watts per square meter.

Dabiri and his colleagues suspected that counter-rotating arrangements of wind turbines whose airfoil blades rotate around a vertical axis (VAWT) can benefit from constructive aerodynamic interactions between adjacent turbines, thereby maintaining the performance of the turbines when in installed close up. By accommodating a larger number of VAWTs within a given wind farm area without adversely affecting the performance of the individual turbines, the power density of the wind farm is increased.

Vertical Axis Wind Turbine Test Site. Full details in the research paper link above.

The field tests indicate that power densities approaching 100 watts per square meter can be achieved by arranging vertical-axis wind turbines in layouts that enable them to extract energy from adjacent wakes.

That number is now experimentally shown as factual.  Take those results out to the world view calculation and the global wind resource available to small 10-m tall turbines based on the present experimental approach is approximately 225 trillion watts (TW), which significantly exceeds the global wind resource available to 80-m tall, propeller-style wind turbines, approximately 75 TW. This improvement is due to the closer spacing that can be achieved between the smaller, vertical-axis wind turbines. The results suggest an alternative approach to wind farming, in which many, smaller vertical-axis wind turbines are implemented instead of fewer, large propeller-style turbines.

All this from just an experiment.

Now this is only an experiment, that doesn’t address the practical limitation a direct evaluation of turbines surrounded on all sides by neighboring VAWTs, as would be the case for the majority of turbines in a wind farm.  But a comparatively simple extrapolation can show using the experiment’s 1.2-meter diameter wind turbine set at 4 diameters apart with a conservative estimates for both the total aerodynamic loss in the array at a doubled 10 percent and the capacity factor (i.e. the ratio of actual power output to the maximum generator power output) set at a low 30 percent. The calculated power density for a VAWT farm with these parameters is still approximately 18 watts per square meter. This performance is 6 to 9 times the power density of modern wind farms that utilize the HAWT design.  There might be something way wrong with plunging forward with those giant propeller wind turbines.

Even more concerning is it is straight forward to compute combinations of VAWT rated power output and turbine spacing that can achieve 30 watts per meter getting 10 times a modern HAWT farms output or even 200 watts per meter yielding 66 times the modern HAWT farm by using 1.2-m diameter VAWTs like those used in the study. Higher VAWT rated power outputs can be achieved by taller turbine rotors than the 4.1-m structures used in these experiments, and by connecting the turbine shaft to larger generators. Indeed, in initial field tests with 6.1-m tall rotors, the captured wind power exceeded the capacity of the 1200 Watt generator on each turbine.

The modern VAWT designs can really crank out the power.

Now this is just a seed, but the gauntlet is thrown between the horizontal shaft builders and the vertical shaft builders.  Today the horizontal shaft builders are on a run.  But investors, lenders, landowners and power buyers can’t remain the suckers for long.  Something has to give, and a war of sorts is sure to come.

It will be interesting to see what imaginative words will support the two sides.  Dabiri and his team have set out some very hard facts using elegantly simple experimentation and measurements. There are practical landscape issues and a wealth of inputs to consider, one being a vertical farm could install within a horizontal farm.  Wind power is going to get far more interesting in new ways and fast.  Lets go.

Back at the July fourth weekend, but Rick Cavallaro and the crew at fasterthanthewind.org proved a wind-powered vehicle traveled downwind faster than the wind speed.  Naysayers said it couldn’t be done, but the anarchist in this writer can’t help but spread the word.  It’s official – impossible but done.  The North American Land Sailing Association made it official July 27th, 2010 when it ratified the results.  And at better than 2.8 to 1 as well.

The achievement means physics texts, record books, and a pile of assumptions all have to be rewritten and reevaluated.  A new frontier, indeed.

Richard Jenkins wrote in part, “My heart is split between belittling idiots, and saluting eccentrics, and this downwind quest lay somewhere in the middle. These loonies were pursuing a pointless goal, doomed to failure, but there was some genuine merit in the myth and their enthusiasm . . . Traveling through zero apparent wind, with no stored power? Impossible. Why would you even attempt it?

A few months later I actually met the idiots in question and, to my surprise and concern we not only have a few mutual friends, but they seemed to be rather technically credible. But, everyone makes mistakes, and I let them off as decent people with a blinkered view of fundamentally flawed engineering . . .  A few months later they were claiming success!

There was, however, a growing momentum of technical people (who should have known better), saying that these idiots have actually proven that it is possible to travel faster than the wind going directly down wind.”

Jenkins shot the video:

The backing for the record attempts isn’t full of dopes either. The list includes JobyEnergy, Google, MetOne Instruments, and SportVision.  Some eccentric press picked it up including Wired Magazine, Popular Science, Discover, Sail Magazine, Discovery Channel, and Thin Air Designs.  Let the skeptics rest.

Cavallaro and his crew designed an innovative ultra-lightweight, aerodynamically sound cart with a 17-foot propeller that’s driven by the vehicle’s wheels. The wheels turn the prop, while the prop turns the wheels – possible thanks to an incredibly heavy-duty transmission – with the wind acting as an external power source that propels the cart faster than the wind itself.

The team set out to prove such a feat was possible and now that they’ve set a record they’ve fixed their sights on breaking it. Cavallaro hopes to reach three times the speed of the wind within a few weeks.

The counterintuitive idea that you can travel downwind faster than the wind is casus belli for aerodynamic arguments from Internet forums to college classrooms. The concept DWFTTW (Down Wind Faster Than The Wind) can cause world-renowned physicists to throw their Nobel Prizes in fits of rage.

Cavallaro explains, “If you’re on a bike and you’re going downwind, you don’t feel any wind anymore at all. You lose the power of the wind when you reach the wind speed, because there is no relative wind at that point.”   Working with a hang-gliding buddy, Cavallaro did the math and built a model to prove DWFTTW is possible.  The equations didn’t persuade anyone, “I thought people would say, ‘That’s cool,’ but they didn’t. They said, ‘Wow, you’re an idiot.’ So we decided to build a full-size one. That’s when we approached a couple of sponsors.”

Cavallaro lined up help from Google and JobyEnergy and set to work with the San Jose State University aero department on an ultralight, four-wheeled vehicle with a 17-foot-tall propeller. The vehicle is made mostly of foam and parallels the aerodynamics of a Formula 1 racecar.  The propeller is key to how it is possible to travel downwind faster than the wind. It’s also the source of the biggest misunderstandings about how the vehicle works.

Cavallaro goes on, “Skeptics think that the wind is turning the prop, and the car is turning the wheels, and that’s what makes the car go. That’s not the case. The wheels are turning the prop. What happens is the prop thrust pushes the vehicle.”

“It sounds like a perpetual motion machine – the wheels turn the prop, which turns the vehicle’s wheels, which turn the prop, which turns the vehicle’s wheels – but you’ve got the wind as an external power source,” Cavallaro said.

Building a transmission capable of transferring power from the wheels to the prop was almost as hard as convincing skeptics that the vehicle would work. It took longer than a year and a lot of trial and error to make it work. “You’ve got to come up with a transmission that can handle those loads, even though it’s not at a high horsepower,” Cavallaro said. “You break some things, and then you build bigger.”

Sometimes it’s the laws that break.  The anarchist in this writer is pleased; other laws can fall, too.  Many things, from BlackLight and cold fusion in physics on to chemistry and biology there’s a wealth of laws that need sent back to being ideas with new frontiers in their place.

WestConnect System Map. Click image for the largest view.

The wind is packed with kinetic energy – molecules in motion that can be used to make other molecules move such as commonly seen windmill water pumps, or used to compress gas and converted into electricity.  When it blows.  When the wind is becalmed, there isn’t any energy other than the latent heat. When the NREL made its assertion one had to read the study.

Dr. Debra Lew, project manager for the study, said in her statement, “If key changes can be made to standard operating procedures, our research shows that large amounts of wind and solar can be incorporated onto the grid without a lot of backup generation.”

The situation now has it that large coal, natural gas or nuclear plants would always need to stand ready to provide backup power whenever the wind ceased to blow or clouds blocked the sun.

The NREL scientists looked at that supposition head on and found that ‘stand ready’ would be largely baseless when the parameters were optimized.  It concluded that in the West, a broad distribution of wind turbines and solar generation would essentially smooth out the supply of renewable power.  Lew explained simply, “When you coordinate the operations between utilities across a large geographic area, you decrease the effect of the variability of wind and solar energy sources, mitigating the unpredictability of Mother Nature.”

Called ‘The Western Wind and Solar Integration Study” it examines the benefits and challenges of integrating enough wind and solar energy capacity into the grid to produce 35 percent of its electricity by 2017. The study finds that this target is technically feasible and does not necessitate extensive additional infrastructure, but does require key changes to current operational practice. The results offer a first look at the issue of adding significant amount of variable renewable energy in the West and will help utilities across the region plan how to ramp up their production of renewable energy as they incorporate more wind and solar energy plants into the power grid. (Pdf download – 20.6MB)

The technical analysis performed in the study shows that it is operationally possible to accommodate 30 percent wind and 5 percent solar energy penetration. To accomplish such an increase, utilities will have to substantially increase their coordination of operations over wider geographic areas and schedule their generation deliveries, or sales, on a more frequent basis. Currently generators provide a schedule for a specific amount of power they will provide in the next hour. More frequent scheduling would allow generators to adjust that amount of power based on changes in system conditions such as increases or decreases in wind or solar generation.

Being a government animal the NREL looks at the policy issues rather than the costs to the ratepayers.  But one can infer some significant fuel costs will be taken out from the calculation when the study says integrating wind as suggested “would also decrease fuel and emissions costs by 40 percent.”  That assertion deserves some testing considering the governments record in making predictions.

The study suggests the results would come with other benefits.  Existing transmission capacity can be more fully utilized to reduce the amount of new transmission that needs to be built.   Coordinating the operations of utilities to facilitate the integration of wind and solar energy can provide substantial savings by reducing the need for additional back-up generation, such as instant on natural gas-burning plants.

And the fly in the thinking is that use of wind and solar forecasts in utility operations to predict when and where it will be windy and sunny is essential for cost-effectively integrating these renewable energy sources. Yet the meteorologists are getting quite good when only looking hours out.

When one looks at a map of the territory involved it doesn’t seem farfetched at all.  While not using the deep resources of the Midwest or the Northwest the five states when combined for managing intermittency do have what looks like a solid 35 percent or better power resource potential.

Event though the study is from a government agency, the study was undertaken by a team of wind, solar and power systems experts across both the private and public sectors.  It’s a long list of contributors.  The work is mainly an operations study, rather than a transmission study, although different scenarios model different transmission build-outs to deliver power. Using a detailed power system production simulation model, the study identifies operational impacts and challenges of wind energy penetration up to 30% of annual electricity consumption.

The NREL page links to the pdf as well as the earlier Eastern Wind Integration and Transmissions study page with a pdf link to the 17.8 MB download.

Many thoughtful people discount wind for valid reasons.  But the fact remains the energy in moving air is significant and one way to overcome the intermittency issue without having massive electron storage is to well, get organized.

Getting organized and planning things out over a big resource base has great potential that mustn’t be overlooked.

Energy Bag Lab Prototypes in Testing. Click image for more info.

Professor Seamus Garvey at the University of Nottingham, UK, is leading a new spin-off company, Nimrod Energy Ltd., aiming to prove that far from being just a pipe dream, the compressed air form of wind energy could be in widespread use within 15 years and at a fraction of the cost of its nearest competitor.

The undersea bags or geological formation stored high pressure air would be expanded into special turbo-generator sets to provide electricity as required – not just when the wind is blowing. The technology could become vast floating offshore ‘energy farms’ created off the coastline around the UK and many other places around the world.

Over the past year, Professor Garvey’s research has proven that by taking offshore wind turbines to a scale never before imagined – a 230 meter diameter model is the baby of the family – and considering some radical redesigns, the total amount of structural material per kW of rated power can be slashed, effectively cutting costs by a factor of four or more. He believes it is possible to store energy at costs well below £10,000/MWh – less than 20 per cent of pumped hydro energy (returning water back behind a dam), the cheapest competing technology.  The technology offers a full power energy saving to metered energy release system, something that levels the intermittent nature of wind.

The testing of scale-model prototype Energy Bags ™ has already commenced. A research project funded with €310,000 from the EON International Research Initiative has already funded the development of analysis and design tools for the energy bags and will provide further prototype testing in seawater leading to an energy storage product that will be ready for use in energy systems by May 2011.

Professor Garvey observes, “This is a classic case of a little foresight leading to technology becoming available exactly when the demand appears. The signals have been out there for years that offshore wind turbines need to grow much larger and that energy storage is going to become the key to integrating large amounts of renewable energy into the UK and world electrical power systems.”

And he astutely points out, “Moreover, the fact that wind turbine diameters were growing exponentially up to 2005 and then stopped fairly abruptly is a strong indication that conventional designs have come to the natural limit of size and that a major rethink is needed. While wind power contributes only a few percent of total UK electricity, we don’t really need to be able to store energy coming from the wind. By 2020, that will have changed profoundly for the UK – so much so that if we do not implement such storage in large measure, we will have to stop putting up wind turbines.”

The same issues apply in the U.S. as well, the intermittent wind supply has no cache or buffer to up rate its value to be either base load supply or as peak supply or to inventory the energy on hand.  Wind energy is currently available “when the wind blows,” hardly a way to extract the best rate of return or drive to a lowest cost for consumers.

Professor Garvey points out, “The UK has abundant offshore renewable energy resource – enough to supply all of our energy several times over. We also have a strong internal energy market – worth well over £60 billion per year. We have an economy desperately in need of rebooting its manufacturing base and an engineering capability, which is the finest in the world. Without an initiative like this, the UK will send vast amounts of money (several times £10 billion) abroad even before 2020 to buy offshore wind turbines and much manufacturing activity will go abroad with that. Worst of all, we will pay substantially higher prices for that equipment than we really need to and the UK energy consumer is going to feel that with sharp rises in unit energy costs over the next 10 years.”  The same basis is true for most developed national economies.

Justifiably enthused Professor Garvey said, “I believe that the ethical/green investment market is effectively waiting for precisely this company to appear. We have already demonstrated that the energy storage system can work. We have not yet built a 230 meter diameter turbine, but we know what it looks like. A neat mechanical engineering concept called ‘structural capacity’ shows directly and quantitatively why these new machines will be far more cost effective.”

At the end of this quote Professor Garvey gets to the major point, “I foresee that at least 25 per cent of offshore wind power in the UK will use this integrated compressed air approach by 2025. Although I expect that the direct-generating wind turbines will catch up with us on cost per unit power output, the role for systems that put energy directly into store is clear. If you have 1MW of integrated compressed air system (including the large energy stores) for every 3MW of conventional generation, then the whole set of offshore wind equipment starts to look like a very versatile power generating system which can adjust its output to match demand – notwithstanding what the wind is doing.”

Another point not discussed in the press release is the air being compressed to an under sea bag would have a linear compression and release pressure as determined by the depth in the water.  That is a major opportunity in capacity, reduced investment and operating expenses.  A store of compressed air is as readily available as opening a valve making the energy available from base load to peak or any point in between.

Most concepts are still at an early stage of development, in which patents have been obtained. But neither business entities nor commercial-scale prototypes exist. No high-altitude wind power technology to date has produced a prototype that has been tested long enough to provide a solid record of electricity generation and associated costs.

But the lure is powerful.  The jet streams, even with seasonal movements are relatively persistent features of the mid-latitudes in both global hemispheres.  The total wind energy in the jet streams is roughly 100 times the global energy demand.  The abundance, strength, and relative consistency make jet stream winds particularly interesting in wind power development.  It’s a huge resource and it is accessible, even though a giant engineering problem.

Now twenty-eight years of wind data from the reanalysis by the National Centers for Environmental Prediction and the Department of Energy have been analyzed and interpolated to study geographical distributions and persistency of winds at all altitudes. The intermittency issues and global climate effects of large-scale extraction of energy from high-altitude winds have been investigated.  Cristina L. Archer at the Department of Geological and Environmental Sciences, California State University in Chico and Ken Caldeira at the Department of Global Ecology, Carnegie Institution of Washington, Stanford whose paper “Global Assessment of High Altitude Wind Power” covers the reanalysis with some interesting points.

As noted the technology is barely past conception stage.  One mechanical concept the authors look at is the KiteGen. KiteGen consists of tethered airfoils (kites) connected to a ground-based generator with two lines, which are pulled and released by a control unit [4-6]. The energy generated during the traction phase is greater than the energy needed in the recovery phase. A single unit of 100 square meters is expected to generate 620 kW of electricity.  Arrays of several kites can be arranged in a carousel configuration around a circular rail for electricity generation of up to 100 MW. This approach appears most suitable for the lowest few kilometers of the atmosphere.

KiteGen Carousel Concept. Click image for the largest view.

The design proposed by Sky Windpower has four rotors mounted on an airframe, tethered to the ground via insulated aluminum conductors wound with Kevlar-type cords. The rotors both provide lift and power electric generation. The aircraft can be lofted with supplied electricity to reach the desired altitude, but then can generate up to 40 MW of power, with angles of up to 50° into the wind. Multiple high altitude wind turbines (rotorcrafts) could be arranged in arrays for large scale electricity generation. For this approach, the aim would be to capture energy closer to the jet streams.

Sky Windpower's Fying Electric Generators Concept. Click image for the largest view.

The sharp reader will quickly realize that as the altitude increases the density of the air decreases so lessening the power of the wind.  The authors give a good rendition of the mathematics and the formulas needed to assess the potential power available.  That point is covered, and the results still offer lots of power to harvest.

The authors even briefly cover the interference with aviation.

The researchers found that the regions best suited for harvesting this energy match with population centers in the eastern U.S. and East Asia, but the fluctuations in wind strength still present a challenge for exploiting this energy source on a large scale.  Ken Caldeira says, “There is a huge amount of energy available in high altitude winds. These winds blow much more strongly and steadily than near-surface winds, but you need to go get up miles to get a big advantage. Ideally, you would like to be up near the jet streams, around 30,000 feet.”

Jet streams are meandering belts of fast winds at altitudes between 20 and 50,000 feet that shift seasonally, but otherwise are persistent features in the atmosphere. Jet stream winds are generally steadier and 10 times faster than winds near the ground, making them a potentially a vast and dependable source of energy.  This is truly competition for ground based wind turbines.

Cristina Archer says, “We found the highest wind power densities over Japan and eastern China, the eastern coast of the United States, southern Australia, and north-eastern Africa. The median values in these areas are greater than 10 kilowatts per square meter. This is unthinkable near the ground, where even the best locations have usually less than one kilowatt per square meter.”  The analysis assessments included the high altitude wind energy for the world’s five largest cities: Tokyo, New York, Sao Paulo, Seoul, and Mexico City. “For cities that are affected by polar jet streams such as Tokyo, Seoul, and New York, the high-altitude resource is phenomenal,” said Archer. “New York, which has the highest average high-altitude wind power density of any U.S. city, has an average wind power density of up to 16 kilowatts per square meter.”  Now that’s like 16 100-watt bulbs in just over a square yard.  This is serious atmospheric power.

Now for the bad news.  Caldeira says, “While there is enough power in these high altitude winds to power all of modern civilization, at any specific location there are still times when the winds do not blow.”  But the comparisons with near surface winds doesn’t seem fair, even over the best areas, the wind can be expected to fail about five percent of the time. Yet, this is a big change from being offline 60 or 70 percent of the time.

Caldeira continues, “This means that you either need back-up power, massive amounts of energy storage, or a continental or even global scale electricity grid to assure power availability. So, while high-altitude wind may ultimately prove to be a major energy source, it requires substantial infrastructure.”

Maybe, perhaps even probably.  But there is a massive resource overhead and ingenuity isn’t in full play just yet.  Five percent or even ten percent down time, with the prospects of energy storage breakthroughs may well blow off Caldeira’s conclusion in the future.

High altitude wind is certainly worthy of more creativity and ingenuity.  The current examples look good.  Meanwhile the leaders in this field need to be looking into the future issues such as land and airspace rights for starters.  One has to know soon if the engineering matures can the technology get airborne at all.

Siemens Energy announced the availability of the SWT-2.3-101 wind turbine, which is suited to sites with low to medium wind speeds. With a rotor diameter of 101 meters, the new wind turbine will provide more power at lower wind speeds, significantly increasing the return on investment of wind farms.

Siemens Low Wind Speed Turbine. Click image for more.

Siemens’ new machine, for example, reaches full output of 2.3-megawatts at familiar wind speed of 12 meters per second or only 26.6 miles an hour. That’s a slower wind speed than other machines in the Siemens line, and a lot slower than the wind speeds required by rival machines such as those made by Denmark’s Vestas and Spain’s Gamesa.

On the other hand General Electric has unveiled its new 2.5-megawatt turbine that operates at full capacity with winds of 28 miles per hour. Its older workhorse, a 1.5-megawatt machine, hits full stride at the same speed as Siemens’ new wind turbine.

The importance is in the low wind speed numbers and the overall size. For those who’ve driven across Iowa and seen the huge fields of huge wind turbines that can be seen for miles off in the high wind corridors, the opportunity to go renewable and with less obtrusive designs bodes for a greatly increased market. Yet by no means is the 2.3 MW size all that small.

With a rotor diameter of 101 meters, the new wind turbine will provide more power at lower wind speeds, significantly increasing the return on investment of wind farms that can be located in the less than optimal locations. There is a lot more wind to be had than just in the fastest wind locations.

Siemens expects low to medium wind market segments to grow substantially in the future. The low-wind market, alone, is expected to represent one third of the total global wind power market in the coming years.

Another plus of the Siemens designs are the proprietary “IntegralBlade” manufacturing process, which casts blades in one piece in a closed process. This unique process is said to eliminate weaknesses from the glue processes used in the manufacturing of traditional blades. A rugged structural design, combined with automatic lubrication systems, internal climate control and a simple generator system without commutator slip rings, contributes to providing exceptional reliability.

For consumers of electrical power Siemens offers what one would expect to be a low operating cost. With the lower wind speed needed much more territory becomes able to participate in the power generation business. Those opportunities mean a lot out in the rural areas where incomes lag behind metropolitan areas. The new versatility for locating does more than offer opportunities, there’s more location flexibility, and better investment returns with planning for longer wind operating periods.

With a better than 50% productivity increase at 26.6 mph over the now aged GE 1.5 MW unit one has to wonder what plans might come to upgrade some older wind farms.

Just to poke a little fun at the WSJs Keith Johnson I might point out that with the newly improved technology coming to much more area in a more compact size maybe saying “looking down market” is the reverse of what’s true. That leads one to wonder how far off the really good product at an individual’s capital investment zone for the rural landowner might be. Lots more farmers can lease a wind location soon along with growing food and fuel.

The best part is that the total expected electrical production from wind has greatly increased. All those projections using the optimal wind zones just became obsolete.