Do wind turbines use more energy for their fabrication than the energy they produce? By U.Bonne, MNF, 21 Aug.2008

The short answer is “no,” and contrary to a recent blog by Britain’s Carbon Trust[4] Our estimate below shows that energy to fabricate and install wind turbines may be less than 12 – 19 % of the energy they produce.

To prove it, lets see if the can estimate the amount of energy needed to fabricate a wind turbine. Lets assume that all the price associated with a device XXX is due to energy cost alone and no cost is due to labor and materials. This is surely an extreme assumption, although there is a small chance that some very energy-intensive material or component is not allowed for properly.

        Using a value of 12.6 - 20 million Btu/ton for the energy cost to fabricate steel [http://www.climatevision.gov/pdfs/Saving_1005.pdf], a steel price of 1000 $/ton [ http://www.thesteelindex.com/ ]  and an energy cost (natural gas) of 13 $/million Btu, we can estimate what steel would cost if only energy was needed to make it: (12.6 - 20) x 13 = 164 - 260 $/ton, i.e. `3-4x lower than the real cost. So, if a device xxx costs 1 million $, we would err on the excess energy side, by assigning it a manufacturing energy quantity of 1,000,000 $ / (13 $/million Btu) = 77,000 million Btu, i.e. this may be ~ 3-4x too high.

        Lets further assume that 1 M$ wind-turbines can be installed and connected for 2 $/W(avg) and then see how long they would have to operate to make up for its manufacturing energy "cost": Average electricity production rates for 1 M$ wind turbines would be (1,000,000 $) / (4 $/W(avg)) = 250 kW(avg) = 250000 /1054 *3600 = 0.85 million Btu/h.  To make up for the above “too-high energy fabrication cost” of 77,000 million Btu, the 1 M$ wind turbine would need to operate for 77,000/0.85 = 90,000 hours = 10.2 years. If we allow for the 3-4x factor above, we get 3.4 – 2.6 years to break even, or 12 – 18% of its 20-year service life.  

        The nominal 20 years service life is from ref.[3], before adding from 1(direct drive)-2(with gear box)%/y maintenance cost to the budget[3], for which the first oil change may be made after 25,000 to 50,000 service hours[1], which is long compared to cars, which get oil changes after only 300-600 hours (equiv. to 3000-5000 miles)

References

[1]. Wind power stations make specific demands on lubricants [ http://www.kluberfood.com/pdfs/LubepointsJune2007_Siebert.pdf ] Plant operators require that the lubricants applied to these machine elements deliver prolonged service life and extended re-lubrication intervals. Although the engine oil of a car is changed after 3,000 to 5,000 miles, which corresponds to an oil service life of 300 to 600 hours at an average speed of 31 mph (50 km/h), the gear oil in a wind turbine is not changed until the unit logs as many as 25,000 to 50,000 service hours.

[2] http://www.metaefficient.com/renewable-power/worlds-largest-wind-turbine-order-2-billion.html Texas oilman T. Boone Pickens  ordered 667 wind turbines from GE, each costing $3 million dollars, making the total order $2 billion. The $2 billion order is just one quarter of the total amount he plans to purchase. Once built, the wind farm would have the capacity to supply power to over 1,200,000 homes in North Texas. Each turbine will produce 1.5 MW of electricity. The first phase of the project will produce 1,000 MW, enough energy to power 300,000 homes. GE will begin delivering the turbines in 2010, and current plans call for the project to start producing power in 2011.Ultimately, Picken’s company, Mesa Power, plans to have enough turbines to produce 4,000 MW of energy, the overall project is expected to cost $10 billion and be completed in 2014.  (Note by UB: 1) The above assumes that the listed MW are average MW and not peak MW. However, see also: Acciona SA of Spain said its Acciona Windpower unit has been awarded an order worth more than €300 million to supply 200 wind turbines to a wind farm in Montana being built by Spanish renewable energy group Naturener. The turbines, with total installed capacity of 300 MW, are to be installed at Naturener's McCormick Ranch wind farm in 2008. So, if 1 Euro ~ 1.5 $US and the above installations benefit from 40% (high) capacity factors, the wind power installations will cost 1.5/0.4 = 3.75 $/W avg. 2) The latest (May 2008) EERE report states:  “U.S. wind power capacity surged by 46% in 2007, with 5,329 MW added and $9 Billion invested”, which equates to 4.22 $/Wavg for capacity factors of 40%; see http://www1.eere.energy.gov/windandhydro/pdfs/43025.pdf

[3] Mick Sagrillo, Sagrillo Power & Light http://www.awea.org/faq/sagrillo/ms_oandm_0212.html

[4] CleanTechnica.com , a recent study put out by Britain’s Carbon Trust, found that: “domestic windmills in urban locations are actually net carbon emitters, as more energy goes into their production, shipping, and maintenance than is saved by their use.” See: