The analyzed system is a Tethered Aerostat Radar System, as a rope break occurred.
Presentation of the device:
The aerostat consists of four major parts or assemblies: the hull and fin, windscreen and radar platform, airborne power generator, and rigging, and tether; they are kite balloons obtaining aerodynamic lift from relative wind as well as buoyancy from being lighter than air.
Presentation of the accident:
From the EXECUTIVE SUMMARY:
The mishap aerostat (MA) was launched on 15 August 2011 from the Lajas Tethered Aerostat Radar System (TARS) Site, Puerto Rico at 1241 ZULU (Z) (0841 local time) and remained aloft until the mishap. At approximately 1637Z on 16 August 2011, a line of thunderstorms hit the site from the SE. Heavy winds blew the MA abruptly to the NW of the site, pulling the mishap winch truck (MWT) off of the pad and into an embankment at the site perimeter. The MA tether was pulled along a steel anti-fouling cable and snapped. The MA broke away, climbed to 7,000 feet and ruptured, causing the associated equipment to impact the ground and be destroyed with total loss and damage estimated at $8,159,917.86. There were no injuries and no significant damage to private property. Clean up costs are pending for 71 gallons of spilled diesel fuel.
Perhaps some ideas in AWES conception could come from this experience. Using architectures with only one tether? With several tethers?
For security and safety reasons, air space around aerostat sites is restricted for a radius of at least two to three statute miles and an altitude up to 15,000 feet (4,600 m).
Also an indication for AWES safety requirements. We can observe that the TARS requires a large restricted zone in spite of being a (more or less according to wind direction) stationary system.
I’m just guessing that during normal weather the real reason for such a large radius is the purpose of the aerostat, which has to do with “national security”-type stuff (which drug-runners to allow through, etc.). During storms, yeah, probably best to stay away.
Then again, a wind energy system would normally be placed in a high-wind area, so maybe best to stay clear. Probably any AWE system reliable enough to come into common use would be fairly safe even in a high wind zone though. If it were very dangerous, it might not even be chosen to fly because investors don’t want to fund self-destructing wind energy systems if possible.