Robert Wilson addressed the captioned question in Wind Turbines and Fuel Used in Creation. Robert summarized the materials required for wind nameplate generation capacity:
On average 1 MW of wind capacity requires 103 tonnes of stainless steel, 402 tonnes of concrete, 6.8 tonnes of fiberglass, 3 tonnes of copper and 20 tonnes of cast iron. The elegant blades are made of fiberglass, the skyscraper sized tower of steel, and the base of concrete.
I think of the captioned question from a slightly different angle:
If we have a grid powered only by wind power — will we be able to replace the aging turbines at their 20 to 25 year end-of-life?
I think the answer to my question is
- We must synthesize a substitute for the diesel fuel.
- We will still need coal and/or natural gas for steelmaking and cement.
- Regardless of chemistry we will need a LOT of reliable, clean energy to manufacture the replacement wind turbines every 25 years or so.
To synthesize all those fuels you will want to have plenty of low-carbon nuclear electricity. And the chemistry of both steel and concrete production will continue to produce large volumes of CO2 (absent innovations I’m not aware of).
Robert walks the reader through the steel supply chain from ore mining and transport, to the blast furnace that converts the iron ore into steel. Every step requires (steel) heavy machinery and copious fossil fuel to power the engines. The final stages require either or both coal (coke for the iron ore to iron reduction) and natural gas. From Chemistry Explained:
Steel furnaces. In the steel furnace, sulfur and phosphorus impurities and excess carbon are burned away, and manganese and other alloying ingredients are added. During the nineteenth century most steel was made by the Bessemer process, using big pear-shaped converters. During the first half of the twentieth century, the open hearth furnace became the main type of steel furnace. This gave way mid-century to the basic oxygen process, which used pure oxygen instead of air, cutting the process time from all day to just a few hours. In the twenty-first century, most new steel plants use electric furnaces, the most popular being the electric-arc furnace. It is cheaper to build and more efficient to operate than the basic oxygen furnace. In the electric-arc furnace a powerful electric current jumps (or arcs) between the electrodes, generating intense heat, which melts the iron scrap that is typically fed into it.
The most modern process for making steel is the continuous process, which bypasses the energy requirements of the blast furnace. Instead of using coke, the iron ore is reduced by hydrogen and CO derived from natural gas. This direct reduction method is especially being used in developing countries where there are not any large steel plants already in operation.
The 402 tons of concrete per MW of nameplate capacity requires the similarly challenging cement supply chain (from US EIA)
(…snip…) the most energy-intensive of all manufacturing industries, with a share of national energy use roughly 10 times its share of the nation’s gross output of goods and services. (…snip…) Cement is also unique in its heavy reliance on coal and petroleum coke.
And because wind capacity factors are typically 25 to 35% in excellent productivity areas, and because we are assuming that the electric grid depends entirely on 100% wind power, then we will have to build 3 to 4 times as many wind turbines as the nameplate capacity promises. That’s a lot of concrete and a lot of steel. Back to Robert Wilson, who concludes with this:
Total cement production currently represents about 5% of global carbon dioxide emissions, to go with the almost 7% from iron and steel production. Not loose change.
In conclusion we obviously cannot build wind turbines on a large scale without fossil fuels.
Now, none of this is to argue against wind turbines, it is simply arguing against over-promising what can be achieved. It also should be pointed out that we cannot build a nuclear power plant, or any piece of large infrastrtucture for that matter, without concrete or steel. A future entirely without fossil fuels may be desirable, but currently it is not achievable. Expectations must be set accordingly.