Clean Power

Published on October 27th, 2014 | by Guest Contributor

13

Why Is There So Much Confusion About “Small Wind”?

October 27th, 2014 by  

Pic1-Chava 12KW turbine sunset Miami

Have you ever noticed energy blogs or articles about small wind turbines comparing them directly with big wind technology and solar? I am writing this article to provide a little background on where small wind turbines can be very successful and where they make absolutely no sense. It also explains why the market for “Small Wind” is vastly different from that of “Big Wind.”

First of all, “Small Wind” has been defined by the American Wind Energy Association (AWEA) as any turbines under 100 kW of rated power. As we all know, 100 kW wind turbines aren’t small! Therefore, others have decided to define them as anything up to 10 kW. For the purpose of this article, we use the same definition as AWEA, up to 100 kW.

Pic2-graph power over windspeedLet’s start with the nameplate rating of the wind-turbines. The internationally acknowledged standard is to rate turbine power at a wind speed of 11 m/s (24.75 mph, or 39.6 km/h). As most insiders know, the power of the wind (and therefore the power of the wind-turbines) goes up by the cube of wind-speed (double the wind-speed means 8 times the amount of power). We have noticed many “inventive” marketers of small turbines rating their product at wind-speeds higher than 11 m/s (we’ve seen ratings at up to 15 m/s), which effectively means they are overstating the turbine’s performance. In order to illustrate how “effective” (or misleading) this marketing can be, you can do the simple math on the cubed function of power versus wind-speed. The wind-power at 13.86 m/s is roughly double compared to 11 m/s, meaning if someone declares a power rating of 10 kW at 13.86 m/s, they are selling effectively a 5 kW turbine.

For more wind turbine basics, here is a pretty nice summary from MIT: MIT-Wind-Power-Basics.PDF

There are a few common beliefs that we have noticed from talking to interested buyers from all over the world.

wind turbine mountains

Common belief #1: “Small Wind is more expensive than Big Wind.” That is generally a true statement, if one compares only the installed cost per rated W. For onshore Big Wind the cost is generally around $2/W of rated power (offshore Big Wind is up to $9/W) and that of onshore Small Wind currently spans from $3 to $7/W. However, Big Wind requires massive grid infrastructure and long-term Power Purchase Agreements (PPAs) to be negotiated with utilities (or determined by regulation), whereas Small Wind typically offsets the customer’s full retail cost of electricity, which can be up to 5 times higher than long-term PPA rates. My home country of Germany is a good example where utility grid capacity is causing some major hurdles for the evolving “Energiewende” (loosely translated the “Transition to Clean Energy”) and more distributed power could lessen the strain on the existing grid. Feed-in tariffs for Big Wind have been declining continuously, whereas the consumer cost of electricity (which is the cost that Small Wind can offset) has almost doubled over the last 10 years.

small wind turbineCommon belief #2: Small Wind is not worth the effort taking into consideration the hassle of zoning and building permits. Well, that really depends on how small the turbine is. Generally speaking, most turbines under 5KW nameplate power rating (at 11 m/s) installed at low height in residential areas with many obstructions leave their owners disappointed with their Annual Energy Production (AEP). In most cases, this is caused by a low “quality” of the wind at the specific location (the site was not chosen for its wind properties, but simply because the owner happens to live there…). A 5 kW rated wind-turbine can cost anywhere between $15,000 (total cost with shipping, installation, inverter, mast, building permits, and electrical work) and $25,000. In bad residential locations, the AEP can be as low as 5 MWh, which would result in a very long ROI (return on investment), of up to 25 years or more, dependent on the cost of power. However, if one looks at the higher end of Small Wind (i.e. 25 kW), the locations are chosen wisely, and an efficient turbine at $3/W is chosen, the Return on Investment can be as short as 3-4 years.

rooftop solar panels wind turbinesCommon belief #3: Small Wind cannot compete with the (currently low) cost of solar. Well, that is true in many areas, even in some areas with low insolation. However, due to the cubed function of power vs. wind speed, as explained above, the AEP for wind has an unequally larger range, dependent on the location.

Here is an example comparison of a 25 kW rooftop solar installation at $3 per Watt (installed, with building permit, inverter, and all electrical work), and a 25 kW wind installation at $3/W installed (which we have verified is feasible, although the price range can go up substantially).

  • Scenario A: 25kW solar is installed on a rooftop in Arizona, producing over 5 kWh/day per kW-peak installed (annual average), resulting in an AEP of roughly 43 MWh. If the wind-turbine is installed at a low-wind location with annual average winds of let’s say 5 m/s, the AEP would only amount to 31 MWh at 95% system availability. In this case, the solar investment would clearly yield better returns.
  • Scenario B: The exact same solar and wind product would be installed at a fairly good wind location in Japan with annual average winds of 7.5 m/s (there are many such locations, especially in coastal areas, mountain ranges, and islands), the numbers would be as follows: Solar would yield an annual average of around 2.7 kWh/day per kW-peak installed resulting in an AEP of roughly 23.4 MWh. The wind turbine, however, would produce an AEP of 74 MWh at 95% system availability. In this case, the wind investment would yield 3 times more annual energy than solar.

It should be noted that these scenarios only compare the Annual Energy Output of an equivalent investment amount (wind/solar) in different locations. However, any investor in distributed clean energy will look at the existing federal, state, and local incentives and the specific feed-in-tariffs (FITs) at the site. For example, the present FIT for Small Wind in Japan is roughly double that of Small Solar, making the wind investment of scenario B roughly 6 times more profitable in Japan.

Pic6-daily electric use curvesOn the other hand, it has to be mentioned that solar energy production matches the typical average daily energy usage peak between 2:30 pm and 6:30 pm (which is the combined peak for industrial, commercial, and residential use) more predictably, at least in summer. So dependent on the net metering scheme available, solar will provide the advantage of peak pricing, which Small Wind could only achieve that with the use of storage. In many net metering schemes, the offset of consumer retail cost will depend on when the energy is produced and how closely it matches the usage patterns. Solar is obviously not a great match for the usage pattern of a parking structure’s lighting system, but it is definitely more predicable than wind.

Pic7-size comparison Small VAWT with peopleDue to the sheer size, a 25 kW wind turbine is not really suitable for the average single family home in urban areas, nor is it suitable for the average residential rooftop. The target application (good winds is obviously always a given) would be on suburban or rural properties, commercial and industrial buildings, off-grid properties (the US alone has over 500,000 of those), agricultural, large billboards, parking structures, remote telecommunications equipment, freeway lighting, and islands. In many of those instances it could very well interact with solar and a reasonable amount of storage to allow for complete grid autonomy. Japan is of course an exceptional opportunity with its currently unbeatable FITs for Small Wind (guaranteed by the central government for 20 years), but it is to be expected that they will eventually follow the declining trajectory of solar FITs over the next 10 years.

Generally, the success of Small Wind has not been as consistent as that of Solar, mostly because it is a lot more complex to understand and evaluate. We recommend that any property owner, business owner, developer, or investor interested in Small Wind seek advice from a professional and conduct a wind survey at the location to improve the prediction of the AEP and the success of the installation.

Our conclusion: Despite its higher complexity, there are plenty of locations and applications all around the world where Small Wind is superior to any other distributed clean energy technology currently available. And for those who choose any of the more aesthetic turbine designs, you will be pleasantly reminded of your investment, not only by the monthly energy reports….

About the author: Hagen Ruff is the founder and CEO of Chava Wind LLC and Chava Energy LLC.

More info: www.chavawind.com or www.linkedin.com/in/hagenruff

Top two images and last image by Chava Wind/Hagen Ruff; wind turbine in mountains, small wind turbine, and small wind turbines behind rooftop solar panels via Shutterstock


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  • Johan

    Just a quick question what is the average service cost of a wind turbine and when must it be serviced?

  • Vampnet

    I have a 16 foot 3 legged concrete base to which my 80 foot pole is anchored to. I have a 5kv wind generator sitting on the pole, installed in late 2011 it has had zero repairs, it produces 5-7kv ph 24 hours a day. Ive only had to shut it down once when winds surpassed 100 knots. My location is not suitable for solar.

    • palomarbob

      5kv = ? to me this means 5,000 volts
      5-7kv = ? to me this means 5,000 volts to 7,000 volts
      ph = ? to me tis means phase

      • Vampnet

        correct.. is phase 3. I sell roughly 4-6k volts back to the utility company. My close neighbor has 2 wind generators on his property He uses 1500-2kv and sells the remaining 15kv back to the local power company.

  • BruceMWilliams

    One key missing piece of info (perhaps due to word limits on the article) is that utiltiy scale turbines have active pitch control, which means their output is limited to their rated capacity (within a few percent), since they automatically use servomotors to feather the blades above the rated wind speed (which can vary, but avg around 12 m/s). Small wind turbines have passive pitch control (stall regulated or centrifugal hammers that pitch the blades with increasing rotational speed), so their output is not exactly flat-capped, but continues to increase somewhat above the rated wind speed.

  • VelvetElvis666

    Another considerable problem with small wind is the specious claims of power production numbers for turbines. The biggest issue the industry faces is one where all turbines need to be certified via something like the Small Wind CErtification Council here in the US. Until then, the overstated/unverifiable power production claims and various new designs and cutting edge/break through” technologies of the next generation vertical or roof mounted turbine will constantly muddy the waters against PROVEN technologies.

    Until the small wind industry adopts better practices overall and stops selling “prototypes” and un-certified designs, it will make adoption of solar – even in most windy places – the easiest cost benefit analysis to prove to a consumer.

  • Hans

    Small wind turbines can be effective at remote locations where wind conditions are good. The problem is that the media keep on hyping miracle turbine types for the built environment, where the wind conditions are poor. More often than not there is not even a prototype, and the turbine is based on some principle that has been tried and failed many times before.

    • Hagen Ruff

      Yes, valid point. It is crucial to look at the power and AEP ratings with a critical eye, verifying the rated wind-speed and verifying who did the certification. The certification process in the US can be done by UL or by NREL and will typically take 1 year. Unless you have extensive technical skills, it would be wise to stay away from self-assembly kits or vendors or who are not willing to invest in proper certification. For larger ‘Small Wind’ units above 20KW you would definitely want to hire a professional regional installation firm who will take full ownership of the installation success.

  • Offgridman

    From the sounds of this the price of low power wind hasn’t changed much in the past nine years, or I saved a whole lot by not having to worry about permitting, and grid tie thanks to my rural location, and backwards state regulations that didn’t have any requirements at the time.
    My 2 Kw turbine was 2800$ including pole tower mounting kit and charge controller. So with another grand max for wire, pipe and the neighbor helping out for a week ,mine was up for under 2$/watt.
    As for specific ROI I can’t be sure, because at the time power tracking equipment was beyond my means. It doesn’t contribute much during the summer except when a storm comes through, but is a very nice balance against the 2.7 Kw in panels during the winter time. Of course my location is very fortunate, with the hundred foot tower on top of the hill where we live with views for miles resulting in very little turbulence..
    Not sure how it works out in meters/sec, but it is designed for low wind conditions, starting generation at just 7 mph and producing peak at 12.
    Tip it down once a year by myself with the tractor to check and grease the bearings, connections, and blades, which takes 4-5 hours, but haven’t found any noticeable wear yet. So don’t see any reason it shouldn’t last us another ten to twenty years or longer, unless a blade cracks or breaks, but they are replaceable quite easily just being a fibre plastic composite.

  • Great article. Useful info. Thanks.

  • Larmion

    Winds at low hub height are extremely turbulent and seldom very strong. The result are low capacity factors in all but the best sites – so low in fact that small wind cannot compete with small solar or big wind despite having relatively competitive cost per nameplate kW.

    Another thing not mentioned in the article is maintenance: wind turbines have many moving parts and it’s an iron law of engineering that moving parts fail. That’s not too big an issue for large scale wind (wind farms typically have dedicated technicians and the turbines are large and expensive enough to warrant expensive wear mitigation techniques and sensors), but it can be problematic for small wind. Compare to small solar which is entirely solid state and thus inherently low maintenance (except for the inverter).

    For a wind turbine to be truly effective, it needs a considerable hub height. Even assuming you can indeed get a planning permit and your property has an appropriate site, the cost of such tall masts all but rules them out.

    Fortunately, there is a far simpler solution for those who, like me, believe in wind (at least in Europe): invest in big wind. I (and thousands of other individuals and businesses in my community) jointly invested in the construction of large (MW-scale) turbines. The amount of energy produced per invested euro is far, far greater than any small scale wind scheme ever could – and the production is less intermittent due to the turbine’s low cut-in speed.

  • RrobertMiller

    No one can be simultaneously an honest businessman and a dishonest businessman. One must choose to be either one or the other. Hagen Ruff decided five years ago to be a dishonest businessman, when he took Mark Goldes for a partner, co-founded Chava Energy LLC with Mark Goldes, and instantly set about swindling people using nearly all the same false and fraudulent claims that Goldes had already used to swindle people for years. Hagen Ruff has never ceased to be a dishonest businessman. His company Chava Energy has never ceased to make false and fraudulent claims in the hope of deceiving and swindling people. For example, they pretend to be developing “energy solutions” that “tap Zero Point Energy,” even though they have no such devices and are not developing any such devices.

  • RrobertMiller

    Hagen Ruff’s Chava Energy LLC has made a great many utterly false and fraudulent claims and statements, showing very unscrupulous dishonesty, on the matters of “Fractional Hydrogen” engines, Ambient Temperature Thermionic Converters, and “MagGen” generators that supposedly harness Zero Point Energy, “Ultraconductor” wire and “Ultraconductor Magnetic Energy Storage Systems.”

    The relentless and pervasive dishonesty, fraudulence, and unscrupulousness, that characterized Mark Goldes’ use of his company Magnetic Power Inc for over twenty years prior to the founding of Chava Energy LLC, has also characterized Mark Goldes’ and Hagen Ruff’s use of Chava Energy LLC and Aesop Institute since 2009.

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