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V.2. Wind Power

(originally published June 18, 2007)

In this series on the electron economy, I’ve already reviewed some but not all of the issues related to building an electron economy, a clean energy economy that can be run using technologies available today, scaled to replace fossil fuels. The electron economy concept suggests that the current emphasis placed upon hydrogen fuel cells and biofuels is not supported by the basic science and the state of current technology. Within the series on the electron economy, I’ve just started a sub-series on the feasible alternatives that might provide the primary energy to generate electricity cleanly. In the first post in this review of renewable energy sources, I reviewed some of the promise and challenges facing solar energy. Next on board is another fast-growing renewable energy source with huge potential, wind power.

From the Bronze Age through the current fossil fuel age, people have used the power of wind to supplement or replace their own muscle power or the muscle power of livestock. On land, wind power has been used as a source of mechanical energy to pump water or as it is being increasingly applied, to generate electricity. The physical force of wind turns the vanes of a wind turbine that in turn provides the rotational momentum to turn a dynamo contained within the body of the turbine. In large installations, wind power is at current prices the least expensive renewable electricity generator per kilowatt-hour. While PV solar installations can be built cell by cell and retain the same efficiency, wind turbine efficiency goes up with rotor diameter and turbine height. Currently the largest wind turbines are 6-megawatt (MW) turbines that stand 186m (610 ft.) tall and with rotors that span 114m (374 ft.).

Wind power has grown very quickly, a 12-fold increase over the past 10 years and currently at rate of 30% per year worldwide. Europe leads the world in wind power installations with wind supplying 3 % of Europe’s power needs. Denmark is the percentage leader in wind power with currently over 20% of its energy needs supplied by wind, while Germany has the largest portfolio of wind power with over 20,000 MWs installed as of the end of 2006, supplying 5.7% of German electric demand. The European Wind Energy Association hopes to supply 22% of European electric demand by 2030. In the United States, wind has also been taking off rapidly, though it still only accounts for less than 1% of electricity generation, with 10000 MW installed as of the end of 2006.

Potential of Wind power

As with solar power, the potential for wind power far exceeds the energy needs of current world population. Also, as with solar, there are local and regional differences in potential, which is measured on a 7-point scale that takes into account wind speeds and frequency traditionally measured at 10 meters off the ground. Sites with a rating of 3 or above are considered good candidates for wind power production though modern utility-strength wind turbines are taller than 10 meters and therefore benefit from higher wind speeds. Wind speed and wind power potential is greater higher off the ground, on ridges and open plain areas. In general, offshore areas have greater potential than inland areas. The United States has a very large wind power potential, with onshore potential greatest in the Great Plains states. South Dakota alone has the wind power potential to supply 50% of the nation’s energy needs. Currently there are only 44 MW of wind turbines installed in South Dakota, even though its potential is estimated at 465,000 MW.

The maximum power rating of wind turbines does not mean that they produce maximum power any appreciable portion of the time. A capacity factor is measure of the average percentage of a turbines maximum power output over time that is actually produced at a given site. A capacity factor of between 25% and 40% is typical for a well-sited turbine, though turbines are usually working 65% to 90% of the time. This means that wind turbines are not often working at full power but continue producing less than their full potential for electricity at lower wind speeds. You get the actual annual electricity production of a wind turbine installation in megawatt-hours by multiplying the rated power of the installation in megawatts by the capacity factor and then by 8766 (the number of hours in a non-leap year).

Economics of Wind

Wind in utility-scale installations now produces electricity at a cost in the range 4-6 cents/kWh, a price competitive with natural gas and coal. If carbon emissions start to be assigned a price either via governments or by some market mechanism, wind (as will other renewables) will become even more competitive. Utility scale wind farms are fairly large investments involving a number of cost factors including land lease or purchase as well as the cost of the turbines themselves and installation. Current costs are estimated at around $1million per MW for a large scale wind farm, with the majority of the cost represented by the manufacture and installation of the turbines themselves. Wind turbine manufacturers include the major electric equipment manufacturers, General Electric and Siemens as well as Repower, Enercon and Vestas. Additional costs that may be shared with utilities and public agencies are the extension of transmission facilities (i.e. the grid) to the wind farm itself. These costs can be substantial depending on the remoteness of the wind farm from existing high-voltage lines and the available capacity in those lines for increased power production. The maintenance cost of modern wind turbines is currently estimated at 1 cent/kWh.

Farmers and large land owners are usually quite enthusiastic about the siting of wind turbines on their land as royalty payments from the electricity generated can add substantial income streams from land that can still function in part as grazing or cropland. In urban or suburban settings, the use of land for wind power installations competes with human occupancy and commercial evaluation of land sites. Despite its ability to produce electricity fairly cheaply, wind power does face the challenge of producing electricity intermittently and unpredictably, more so than solar. Thus the electricity produced cannot necessarily be classed as baseline or peak power in the electric grid, leading to more uncertainty about how to accommodate and price the electricity that wind produces.

Wind power investment is and should be supported by financial incentives such as the 1.9cent/kWh tax credit for the first 10 years of generation in the United States or guaranteed feed-in pricing as can be found in Europe. The more secure this type of support is, the more profitable and secure are investments in wind.

Transmission Facilities

The growth of wind power is limited in part by the lack of sufficient power transmission facilities in the often-remote areas where wind potential is the greatest. In the United States, some of the highest potential areas do not have high-voltage transmission facilities conveniently located nearby. The construction of high-voltage transmission facilities for the Great Plains areas is a high priority for those who are committed to tap into the wind-rich areas in the band from Texas to the Dakotas. Offshore installations require underwater transmission facilities that bring the generated electricity to consumers on land.

Drawbacks and Criticisms of Wind

Wind energy’s main drawback is the unpredictability of wind in even very favorable locations. While a capacity factor of 40% is acceptable for a technology that is relatively inexpensive per unit energy produced, when the energy is produced varies from day to day and different times of the day. A secondary drawback are the remoteness of the best locations for wind generation, which means that major capital investments in the billions of dollars needs to occur for many societies to exploit wind to an extent that will make a large dent in their carbon emissions.

Wind turbines also require some maintenance and are vulnerable to environmental stresses including icing, lightning strikes, and extreme cold temperatures. Age also leads to higher maintenance costs though newer generations of turbine are said to have lower maintenance requirements.

Other criticisms revolve around the ecological costs of wind turbines, which are tall, large structures with substantial concrete foundations and giant moving rotors. If, as has happened at an installation in Europe, the foundations of these structures disturb a carbon-rich ecosystem like a peat bog, the construction of the wind farm incurs a carbon debt that is difficult for the operating wind farm to make up (usually wind farms are estimated to achieve carbon neutrality within 3 years). In certain locations, wind turbines have killed birds and bats in greater than acceptable numbers though proponents point out that modern wind turbines are usually no more destructive of wildlife than other large human-built structures.

Certain high profile projects like Cape Wind in Massachusetts also highlight the varying reactions that people have to the prospect of large wind turbine farms within view of their homes or vacation spots, a.k.a. NIMBY-ism. With Cape Wind, the first US offshore wind farm project, turbines would be placed 4 to 11 miles from the shore of Nantucket Sound, but some local residents, including the usually pro-environmental Kennedy family, have opposed the project on largely aesthetic grounds. Within distances less than a mile, wind turbines can make noise that may be disturbing to some people and wildlife though at higher wind speeds (8 m/s or 18 mph), the sound of wind blocks out the sound of the turbines. The placement of wind turbines in remote locations has generally been uncontroversial for residents of those areas. Still, a sober assessment would indicate that the capture of natural energy flux for human consumption will involve some costs and disturbance of natural and cultural landscapes, we hope with broader positive effects for planetary ecosystems.

Small-scale Wind

Wind turbines also come in smaller sizes, though unlike with photovoltaic, smaller turbines are less efficient than their bigger brethren and rotate more rapidly. Whatever their efficiency, businesses and property owners with wind resources can generate their own clean electricity using turbines as small as 1 kW, equivalent to a small photovoltaic solar array, though as with larger turbines, it is best to mount these turbines on tall towers. Bergey, a marketer of smaller turbines, offers towers from 60 to 120 ft. tall as well as a larger 10kW rated turbine with a 22 ft/7m rotor diameter.

Alberici, a St. Louis area construction firm, is generating 20% of its electricity needs through a 65kW turbine located on the 13 acre campus of their LEED Platinum certified headquarters. The turbine has a diameter of 52 feet and sits on a pole that is 124 feet tall.

Speculative Wind Technologies

Technologists and businesspeople that see the potential in wind are working to overcome some of the drawbacks associated with wind. As I have mentioned in a previous post, the notion of a supergrid has been introduced as a way for wind farms at widely dispersed locations, as many as 4000 miles apart, to generate a more even and predictable supply of clean electricity. Airtricity, a leading wind farm developer and operator based in Ireland, has proposed a offshore supergrid that would connect wind farms dispersed around the perimeter of Europe, relying on the observation that the wind is always blowing somewhere. Potentially such a supergrid could allow for a higher percentage of wind resources in the production mix. A similar grid could be built connecting any widely dispersed areas with favorable wind resources. The challenges associated with building a supergrid are primarily financial and political facilitation of cross-border electricity transmission; no technological leaps are required.

A more speculative technology covered recently by Wired magazine is Kitegen, proposed by the Turin-based Sequoia Automation and physicist Massimo Ippolito. Kitegen is projected to tap into the always-available high-level high speed winds that circle the earth at the level of Europe and the US at heights between 500 and 10000 meters. Ippolito’s calculation is that this ribbon of wind has the power of 95 million megawatts. Rather than use a rigid windmill, Kitegen proposes using a large horizontal merry go-round type turbine that is driven by computer-controlled kites at altitudes of 1500 to 2000 ft. pushed by these winds. A wide diameter (2000 meter) horizontal turbine with such kites occupying several square kilometers, is calculated to have a power rating of 5000 MW with a high capacity factor and availability. If Kitegen is successful, wind could function as baseline power in the United States and Europe at what they claim will be a very moderate cost.

Wind and the Electron Economy

In his 2006 book, Plan B 2.0, noted environmental visionary Lester Brown proposes a way out of the climate and energy crisis we are facing by relying largely on wind resources. He believes that the worst of the climate crisis can be averted if we engage in a type of mobilization previously only seen in wartime, where the tasks at hand to set the economy on a greener path are given first priority in both the public and private sectors. His choice of wind is significant in that wind turbines could potentially be produced on a mass scale, as there are few resource constraints in scaling up production and we have already located where wind resources are most abundant.

While Brown’s emphasis on wind is I believe undervaluing innovation and upcoming cost reductions in solar power, energy companies, utilities and investors should pursue wind very aggressively where there is a wealth of wind resources. The old shibboleth of wind’s variability and therefore lack of fitness for utility-scale production has been debunked by Northern Europe’s experience with wind even without the stabilizing effects of electricity storage or a continental supergrid. Denmark’s electric grid has not shown any ill effects from its 20% reliance on wind power and is driving towards 50% wind energy by 2025, so the many countries that lag behind have a long way to go before there may run into uncharted territory with regard to managing a grid with a high percentage of wind power. We also have the resources to produce wind turbines en masse as they do not require exotic materials or production processes.

As a thought experiment on the other hand, if we were to limit ourselves to using only wind power to generate electricity, a number of technologies would need to be built out to provide for both baseline and peak power. Conventional wind turbines would need to be linked together in a supergrid, as proposed above or a technology like Kitegen would need to be able to produce copious baseline and/or peak power on demand. In addition, some form of mass energy storage would be necessary to be able to meet peaking local demand.

In the next posts in this series, I will discuss other clean energy options available to power the electron economy including the old but controversial standby hydropower.

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