Democratic Underground - The purpose of shifting to alternative energy

is of course to decarbonize the atmosphere. That means we need to replace the oil used by cars as well as the coal and gas used for electrical generation. Given that we won’t be able to call on nuclear power to help, how much wind power would it take to do the job?

How about an operating plant of 6,300,000 5 MW wind turbines world-wide?

Here’s how I got that number.

First, I’ll set out my assumptions:

We may need gas turbines as peaking plants, so I propose to leave 10% of the fossil fuel use intact for that and replace the other 90% of the oil, gas and coal we currently use with electricity from wind.
I propose to do it by 2050, giving us a nice generous 40 years to “git ‘er done”.
The requirement for primary energy would rise by 1% per year – this is less than half the last 45 year average of 2.5%, but we’ll give up the other 1.5% per year to efficiency improvements and conservation.
Since we’re replacing thermal power with wind electricity, we get a 60% improvement in energy converted to work, meaning we only need to replace 40% of the fossil BTUs.
We'll do it all with 5 MW turbines that run at an average capacity factor of 23%

The world currently uses 9800 million tonnes of oil equivalent (mtoe) per year of fossil fuels. A 1% growth rate puts the 2050 usage at 14,750 mtoe.

Keeping 10% of that usage intact means we have to replace the work done by 13,275 mtoe.

Applying our 40% conversion factor, we will need to replace about 5300 mtoe.

According to BP’s Statistical Review of World Energy 2010 (the source for all the data here) the conversion factor they use for electricity is 12,000,000 MWh per mtoe. So we will need to be able to generate need 63,600,000,000 MWh of electricity from wind in 2050.

A 5 MW turbine running at 23% capacity produces about 10,000 MWh in a year. In 2050 therefore, we would need to have 6,300,000 5MW turbines running world-wide.

If we installed the same number of them every year, we would need to install 157,500 turbines, or 787.5 GW of capacity every year to reach the required capacity by 2050.

Of course, 40 years is beyond the life cycle of a turbine. Assuming a 20 year life cycle, we need to replace all the 20-year-old turbines at the same time as we’re installing the new ones. So by 2050 we’d be re-installing 5% of the operating plant each year, or 315,000 turbines a year, which we would need to continue forever.

That means installing 1575 GW of new capacity every year. Last year we installed 37.5 GW. We will need to maintain 40 times that installation essentially forever to get the job done.

Given our addiction to fossil fuels, how probable is this scenario? Personally, I have to put on my green glasses to keep the emerald brilliance from blinding me.

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