Powering Titan... Everywhere the Wind Blows
Last month, we discussed the possibility of powering Titan through importing fossil fuels or solar panels from Earth. We concluded that those methods are probably not very viable, and any plan to colonize Titan will need to exploit Titan’s huge reserves of liquid methane (as well as having gaseous methane make up over 1% of its atmosphere). This post will explore some issues involved in exploiting these methane reserves, but first we will look at two other potential power sources that have gained attention recently back here on Earth. This month we will discuss wind power and we will discuss nuclear power next month.
Wind Power: Wind turbines (pictured below) are machines that extract the energy from wind. Wind is moving air, and the moving particles in air contain energy that can be extracted by a wind turbine. Air comes in moving at a certain speed, and the air coming out of the turbine is moving slower, but over a wider area. The wind moving at a slower speed contains less energy and the leftover energy can be extracted and turned into electric power.
The fraction of energy that can be pulled out of wind is independent of the density of the air, so we should expect that the basic principles of wind turbine design on Titan should look similar to that on Earth. The energy in wind is proportional to the density of air, so for the same speed wind, a turbine on Titan should produce 4.5 times as much power as a turbine on Earth, as the air on Titan is about 4.5 times as dense.
It is common to see large wind turbines on Earth capable of producing about 2 Gigawatts of power, enough to power well over 1 million homes- and a good size settlement on Titan. A similar-sized turbine on Titan could produce close to 10 gigawatts or enough to power more than 5 million homes. The turbine would need to be built stronger to withstand the heavier air, but it’s clear that turbines are of the right scale to provide power needs for Titan.Titan and Wind Speeds
The question is whether winds blow at the right speed on Titan. Low wind speed (less than about 5 mph) cannot generate power, and as you increase speed, more power is generated, with optimal speed around 35 mph. Above a certain limit, usually less than 50 mph for large turbines, turbines turn off for self-preservation. These can change a little based on design, but are a good guide.
The probe Huygens descended through Titan’s atmosphere, taking wind measurements the entire time. In the upper atmosphere, winds raged as fast as 270 mph. As Huygens descended to the surface, the wind speed tapered down. By the time Huygens got to the surface, the wind speeds were under one mile per hour. The question of wind raises another one of the mysteries of Titan: there is evidence of wind from sand formation, yet Titan’s methane oceans shows no signs of waves, even though waves would form as a result of even very slow winds.
One potential explanation for this is due to seasonality on Titan. Because it takes 29 years for Saturn to orbit the Sun, winter lasts for half that time, or close to 15 years, on Titan. Since Cassini arrived in 2004, Titan’s northern hemisphere, where most of the lakes are, has been in winter. Could the cold, settled air be preventing strong winds from blowing? If so, things should change around 2017, as Titan’s northern hemisphere enters summer and the wind is expected to blow.
So there are some favorable considerations to wind turbines, but it is possible that the wind doesn’t blow on Titan foro 15 out of 30 years! That’s certainly a very major negative consideration...