As for lightning, The device could be built to be completely insulated on the outside, with coated cables as well. Either that or you make it have a conductive outer shell which redirects lightning through the tethering cables to the ground safely.

Spuffler: So what if helium isn’t common? There’s such technological advances nowadays like trucks and planes which transport goods for us. Also, the device isn’t going to fall to the ground when the wind dies, because it’s held up with helium. It’s not like a kite, it’s like a balloon.

Helium is not common in rural Manitoba; generation devices capable of several megawatts are neither common nor are they likely to survive a drop to the soil when the wind fails and no system retrieves the MARS. You see, computers fail, battery backup systems can fail to be ready, and then … lightning. Lightning often strikes the higher objects before any other objects…. a 600 – 1000 foot high MARS which is tethered from the top of a hill is the object most likely to be struck first. And then there is the problem of winds that start shifting to such a degree that nothing can winch the MARS in quickly enough. Or maybe you make a MARS which is more robust, and allow it to swivel 360 degrees, which means the problem of the rotor swath of the land based bladed turbine has now become a hemispherical restriction of much larger cubic volume.

@Faranya: The winching down of the turbine during storms will reduce its vulnerability. For particularly vulnerable locations, the turbine and spool can be placed in a retractable lean-to that is grounded independently from the turbine. Otherwise, the turbine can be winched to a rest upon a (separately grounded) pedestal which surrounds the winch but does not touch it. This should help keep the winch assembly dry and direct some of the errant lightning through the pedestal – reducing the chance of the tether cable frying from the shock.

@Bryan J Blevins: I imagine some creative engineering can result in a design that maximizes the turbines perpendicularity to wind direction. I also imagine that it will be impossible to achieve a constantly perfect orientation. Changing wind directions will not only hurt efficiency, but twist the tether. One possible solution to reduce twists is for the spool to be mounted on a rotating pedestal. I’m not a materials engineer, but nifty things have been done with fiber optics being embedded in materials to monitor for stress.

@ikkonoishi: All renewable energy sources have some impact. They all require some disruption of environment to the detriment of local species, and all require raw materials which are themselves disruptive to acquire. Geothermal power is possibly the least species-disruptive, but it’s simply not feasible in many parts of the world.