Undoing
Undoing
[Caption above the panel:] My Hobby:
[A large wind turbine is spinning but the electric cord has been severed and rewired to a large fan.]
[Caption in large text below the panel:] Undoing
A similar understanding of the difference between a wind turbine and a fan is presented by Megan in the later comic: 1378: Turbine .
This comic may be a continuation of Randall's mistrust of modern electric wind turbines (see 556: Alternative Energy Revolution ).

The comic (another in the My Hobby series) is a play on how energy from natural resources (wind, sun, water) gets turned into electricity. Wind turbines convert the windpower into rotational energy, which can then be used to produce electricity. The one seen in the image is the most commonly known wind turbine, which sees use on wind farms. Wind turbines provide a renewable resource for homes and cities and a common method for sustainable energy. Turbines have been referenced before in xkcd, in 556: Alternative Energy Revolution .
In this comic, Cueball has rigged it so that the wind turbine powers a fan . He cut the power cable attaching the turbine to the power grid and spliced it with the power cord of a giant fan. The nailed-together 2x4s that form the "tower" for the fan further indicate the " jury-rigged " nature of Cueball's work. The electricity generated from the windpower is then used to power the fan, which in turn produces wind. This is in reference to the complementary nature of wind turbines and fans, which was also covered in 1378: Turbine .
The undoing part refers how Cueball is using this fan to restore the wind that was used to turn the wind turbine back to the original wind flow.
Wind turbines have a theoretical limit of 59% of the portion of wind captured. You can see the wind not captured detailed in the image as dotted, turbulent curly lines; turbulent flow. Cueball has placed the giant fan in the direction of the wind so that the wind it produced combines with the windpower not captured by the wind turbine. This is indicated by the lines smoothing, like they were at the start. Thus, not only is the electrical benefit undone, but also the change in natural wind currents.
The title text explains that he performs the same undoing process with solar cells, where light energy is converting into electricity using photovoltaic cells , which is then used to power lightbulbs for producing light on the area below them that the sun would normally illuminate. Solar panels only convert 20-25% of the energy captured from the sun into electricity. However, Cueball points out that he sees this as a 20% gain rather than an 80% loss. Since it is Cueball's hobby to literally waste time and energy, this makes perfect sense.
Incandescent light bulbs only convert at most 5% of the electricity provided into light, the rest is lost as heat energy. Thus less than 1% of the energy absorbed from the original sunlight will be released as light from the bulb. LED bulbs can do quite a bit better, approaching 90% efficiency, releasing around 17% of the original sunlight, though in different frequencies.
In the case of the wind turbine and fan, the wind will unfortunately be moving at a much slower velocity than at the start as energy was lost in converting windpower to rotation energy, then to electricity, then back to rotational energy, then back to windpower. However, in the solar panel and lamp case, the light will be moving at the same speed as it entered the panel thanks to the constant nature of the speed of light, but be less bright instead.
[Caption above the panel:] My Hobby:
[A large wind turbine is spinning but the electric cord has been severed and rewired to a large fan.]
[Caption in large text below the panel:] Undoing
A similar understanding of the difference between a wind turbine and a fan is presented by Megan in the later comic: 1378: Turbine .
This comic may be a continuation of Randall's mistrust of modern electric wind turbines (see 556: Alternative Energy Revolution ).
