A tornado has several orders of magnitude less energy than a hurricane, but both can kill people and create enormous damage to lives and property. It would be good to be able to reduce their force by sapping away their energy. The extractor does that. The energy extracted would be in electrical form and could be beamed by microwave to a rectenna array. These would be spread around the areas that suffer most and their costs offset by the high value of the energy collected.
An extractor would be large scale engineering in the sense that it would be very large, but it need not be especially heavy. It would actually be a fairly free-moving but tethered aerial wind farm. Size would be a few kilometres across up to 50km. Depth would be 200-300m.
It could be made entirely of carbon – carbon foam for buoyancy of the structure, graphene or carbon fibre supports and beams to hold the structure together and give the rigidity needed to sap energy from the storm, graphene capacitors for the vertical axis micro-turbine blades, and super-capacitors to store energy pending transmission, graphene string as the spindles for the blades and as wires to conduct the electricity around.
The pieces holding the structure would have a very strong graphene core, lined with buoyant carbon foam, and therefore need little weight still to be supported, so could easily be floated up from the ground and assembled mid air, using carbon foam balloons to hold the assembly platforms, and a high altitude carbon foam balloon could drag it into place and hold it in the storm vicinity once ready.
The struts all lock together to form a fairly rigid structure, but one that could bend a great deal before any damage would result. An extractor could be fifty kilometres across to sap energy from a large storm such as a hurricane, but just a few kilometres would do for a more tightly focused event such as a tornado.
100m square sails would be hung between the struts. Each sail would be made of hundreds of thousands of small S-shaped carbon capacitors, held on a graphene string spindle. As the wind blew on them, the concave side of each capacitor would catch the wind and be forced through a narrow gap. That would bend it further. When it cleared the gap, it would spring back to its normal curvature before being bent and straightening again as it passed through the gap on the other side. The difference in drag between the concave and convex sides provided the force to push the blades through the gaps, and the flexing of the carbon capacitors made the separation between the plates vary, thus creating a voltage change and electrical current. That electrical energy extraction meant less energy for the storm. The electricity was passed through graphene strings to a collector cable which carried the huge aggregated current from each sail.
The overall force on each sail would be high, but the super-strength carbon materials they are made from are easily up to the job. The enormously strong winds in a tornado or hurricane would create massive forces that should normally cause a large sail to be carried with the wind, but due to the massive size of the overall extractor structure, the wind movements at each sail are very different and forces in one direction on the wider structure would be balanced against forces in another. Overall the array creates massive drag that slows the winds. The individual tiny rotating vertical axis vanes don’t care which way they were heading. As long as there is some local relative movement of the air, they would be able to extract energy from that area. High stresses would be generated but the strength of the graphene struts would withstand them. The overall effect would be that the whole array would wander around a bit, but its overall position would be determined by the balloon supporting it far above. The powered balloon would follow the path of the storm and extract as much energy from it as possible, transmitting it by intense microwave beams to earthbound rectenna arrays that have been situated in the areas usually affected.
In this way, huge energy could be extracted from a storm. A tornado could quickly be drained of almost all of its energy and rendered harmless. A hurricane would take longer. Its total energy was many orders of magnitude greater than a tornado, and its overall force would be more gradually siphoned away. Each 100m square sail could extract a few megawatts, and there were a thousand of them on the largest extractors. Siphoning off several gigawatts from a large hurricane could downgrade it substantially within a matter of hours, saving many lives and enormous saving of property damage. The free electricity is just an added bonus. Tornadoes are far smaller and easier to deal with than hurricanes and could quickly be made totally harmless.