The Damage Done, Part 7 — Wind Power — Really Green, or Is It Just Spin?

Wind farm in SpainWind might seem like a no-brainer as a source of green energy. As with hydro and solar, what could be more renewable and sustainable than to erect a turbine and let the wind spin it around to generate electricity? What could be more environmentally friendly? (Photo: Wind farm in Spain. Credit: Chris Barber, CC BY 2.0.)


But here at ThomasNet Green & Clean, we don’t like to make assumptions about these things. What about the manufacture, construction, and maintenance of wind turbines and their components? Don’t those processes cause pollution and emit greenhouse gases (GHGs)? What about the disposal of the equipment when it reaches end of life? What about those poor birds and bats that get caught by spinning wind turbines?

Given these issues, how do we know that wind power is really any cleaner than coal, natural gas, or nuclear as a way to generate electricity? And how does wind compare to other renewables such as solar, hydro, and geothermal in its environmental effects?

Wind energy is this week’s target in the series of articles we’re doing on “The Damage Done” by sources for electrical power generation. To review what we’ve done so far, take a look at our articles on coal, gas, nuclear, and hydro.

The World Wind Energy Association (WWEA) in its “World Wind Energy Report 2010” says that worldwide nameplate capacity for wind power reached 196.6 terawatts (tW) in 2010. The report says that all wind turbines installed by the end of 2010 can generate 430 terrawatt hours (tWh) yearly, representing 2.5 percent of world electricity consumption.

The chart shown here, constructed from Energy Information Administration (EIA) data, shows that hydroelectric generation dominates the renewables market and is expected to do so through 2035. However, even that chart shows wind growing very fast.

Global electric generation from renewables

This second chart, taken from the EIA’s “Annual Energy Outlook 2011,” takes hydro out of the picture. In that chart you can see the dramatic growth rate of wind generation expected through 2035. EIA data project that electrical generation from wind will grow almost 600 percent from 2008 to 2035, while hydro will grow only 80 percent during that same period.

Non-hydro renewable generation

Source: Energy Information Administration

The strong projected growth for wind generation emphasizes that whatever the environmental impacts of generating electricity from wind, they will likely multiply rapidly over the next 25 years.

Does Wind Power Damage the Environment?

Wind turbine nacelleIt’s easy to say that renewables are good and fossil fuels are evil. But our purpose in this series is to look for ways to actually measure the environmental effects of electrical-generation technologies rather than just take things for granted. So I’ve been looking for information sources that provide actual figures to go by. (Photo: Wind turbine nacelle, the assembly on top of the turbine housing the shaft, gearbox, and generator. Credit: Hepburn Wind, CC BY 2.0.)

Martin Pehnt of the Institute for Energy and Environmental Research in Heidelberg, Germany, has conducted dynamic life cycle assessments for a number of renewable energy technologies, including wind. In his paper “Dynamic life cycle assessment (LCA) of renewable energy technologies” (Renewable Energy, 2006), Pehnt explains that LCA “investigates environmental impacts of … systems or products from cradle to grave throughout the full life cycle, from the exploration and supply of materials and fuels, to the production and operation of the investigated objects, to their disposal/recycling.” For more details on what LCA involves, see my previous article on hydropower.

The following chart presents some of the measurements set out by Pehnt, comparing the life-cycle environmental effects of several renewable sources, alongside those of a conventional energy mix (coal, gas, nuclear, etc.):

 

Environmental Impact Conventional Energy Mix impact/kWh Hydro impact/kWh (large facility) Wind (on-shore) impact/kWh PV Solar impact/kWh Geothermal impact/kWh
Non-Renewable Energy Demand in megajoules (MJ)

8.91

0.10

0.12

1.50

0.54

Iron Ore in grams (Proxy for non-energy resource consumption)

2.60

1.70

3.30

3.30

3.20

Global Warming (g CO2 equiv.)

566.00

10.00

11.00

104.00

41.00

Acidification (mg SO2 equiv., or sulfur dioxide equivalents)

1,083.00

42.00

61.00

528.00

190.00

Eutrophication (mg PO43- equiv., or phosphate equivalents)

59.90

5.00

4.00

44.00

24.80

 

By most of the measures given here, wind power compares favorably with other renewable technologies, and especially so against the conventional energy mix.

Wind uses much less non-renewable energy than the conventional mix; the obvious reason for this is that wind power’s life cycle uses relatively little non-renewable energy such as coal, natural gas, or uranium. Pehnt uses iron ore as a proxy for physical resource consumption overall, as a technology’s use of iron is a pretty good indicator of the volume of physical resources required during the technology’s life cycle. Wind power consumes considerable physical resources because of the manufacture and construction of the turbines and towers.

In the key environmental-impact measurements, acidification and eutrophication, wind scores very well, on a level with hydro power. Acidification refers to the decrease in pH and increase of acid formation in water, particularly seawater, an important environmental concern. Eutrophication refers to excessive growth of algae, or “blooms,” caused by the deposition of nitrates and phosphates.

Are Greenhouse Gases Blowing in the Wind?

On the face of it, you might think a renewable energy source like wind wouldn’t generate greenhouse gases (GHGs). But to really compare wind power with other electrical generation technologies, you need to consider the entire life cycle of the technology. A spinning wind turbine isn’t directly giving off carbon dioxide (CO2) or other GHGs. However, the turbine had to be manufactured, transported to the site, and erected. It has to be maintained, and it has to be disposed of at the end of its life. (Photo: Erecting a wind turbine. Credit: Tibor Hegedis and Hepburn Wind, CC BY 2.0.)

Erecting a wind turbine

All of those activities involve some emission of GHGs. Benjamin J. Sovacool of the Vermont Law School, in his study “Valuing the greenhouse gas emissions from nuclear power: A critical survey,” (Energy Policy, 2008), compares the carbon footprints of a number of electric generation sources. The following chart based on his article shows how wind energy compares with other sources:

Source/Technology Lifecycle CO2 Equivalents (gCO2eq/kWh)
Coal 960 to 1,050
Natural gas 443
Nuclear 66
Solar Photovoltaic (PV) 32
Hydroelectric 10 to 13
Wind 9

As you can see, wind power compares very favorably with other technologies when it comes to GHG emissions. The chart shows measurements in carbon dioxide (CO2) equivalents, expressed as gCO2eq/kWh. For an explanation of this metric, see my previous article “The Damage Done, Part 3 — Is Coal Really So Bad for the Environment?

In his study “A guide to life-cycle greenhouse gas (GHG) emissions from electric supply technologies” (Energy, September 2007), Daniel Weisser of the International Atomic Energy Agency writes that

For wind turbines most of the GHG emissions arise at the turbine production and plant construction, which vary between 72% and 90% of cumulative emissions. Significant differences lie mainly in the foundation of the power plant. For instance, offshore wind turbines require significantly higher amounts of steel and cement than an on-shore counterpart for construction. For onshore plants however most of the GHG emissions relate to the turbine production (mainly for the tower and the nacelle). GHG emissions not related to construction and production arise during [operation and maintenance], decommissioning, transport of materials and turbine, and range between 10% and 28% of cumulative emissions.

And Those Giant Spinning Blades?

Concerns over ecological effects of wind power tend to focus on destruction of flying creatures. In its report “Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use,” The National Academy of Sciences (NAS) writes that

Bird deaths attributable directly to wind generation of electricity probably are less than 100,000 per year in the United States… The only bird deaths considered to potentially reflect a population-level problem currently are of raptors, occurring mainly in older installations in California.

Bat killed by a wind turbineNAS says that total human-caused bird deaths in the U.S. probably number at least 100 million per year and possibly as many as 1 billion. This means that, at current levels of wind power, turbines are causing perhaps one out of 1,000 human-caused bird deaths, and possibly as few as one out of 10,000. That number would naturally rise as more wind farms get built. (Photo: Bat reportedly killed by a wind turbine in Tennessee. You’re welcome. Credit: Chris M, CC BY 2.0.)

NAS also points out that the construction of wind farms has similar effects on the land as construction of conventional power plants. The report says that

The overall footprint of a wind-energy plant tends to be larger than for others, but the intensity of land-use change can be lower, because in many cases, the land between the turbines is not affected.

In the next installment of “The Damage Done,” I will examine the environmental effects of active solar power.

Want to get caught up on our previous articles on “The Damage Done” to the environment by both renewable and conventional sources of electrical power? Here are links to the previous installments:

The Damage Done, Part 1 — Is Green Energy Really Better for the Environment?

The Damage Done, Part 2 — How Do You Measure the Environmental Effects of Energy?

The Damage Done, Part 3 — Is Coal Really So Bad for the Environment?

The Damage Done, Part 4 — Natural Gas, Green or Dirty?

The Damage Done, Part 5 — Nuclear Power, the Green That Glows?

The Damage Done, Part 6 — How Green Is Hydro Power?

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