AWE systems (AWES) materials run the gamut from “energy drones” with composite airframes, complex power electronics, and advanced avionics, to “rag & string only”, pure engineering polymer, like UHMWPE or nylon as examples. Obviously the high-complexity platforms entail less than 100% structural material with recycling challenges for a truly sustainable circular economy.
High-complexity advocates hope to achieve key operational advantages, like longer service life and superior control. They seek high performance at max L/D. CAPEX is high. Maintenance resembles conventional aviation, with high OPEX. Every sort of material finds a place in these designs, including toxic unrecyclable elements, with diverse materials science applicable. Composite AWES airframes and conventional HAWT blades are built very similarly, with common O&M and lifecycle properties. Most of energy drone type jobs are inside a factory. Repairs and regular inspections are slow and complex. Control is demanding, at high speed, with scant margin for error. Crashes are generally dangerous, with a total loss of the platform.
The Rag & String AWES camp seeks highest power-to-mass, using the highest strength-to-mass material kept at its working-load. Any non-structural material aloft is parasitic to raw performance. The idea is “a truck not a sports-car”; max-power by max-area, rather than highest L/D. Generators and controls are kept on the ground. This AWES archetype has converged on single-skin (SS) fabric wings derived from NASA’s Apollo program, notably the NASA Power Wing (NPW) and SS derivatives. The scaling path is simply a fractal load-path network, from the fabric weave with rip-stop threads, to as many stages of load path networks needed to reach extreme-scale wing dimensions. Crashes are generally benign, and the wings hop right back up.
Cheap polymer fabric reaches pay-back very fast, in a few weeks, while advanced polymer lifetime is indefinite, if over-tensioning and abrasion is avoided. Some (careful) kite pros use the same lines for years. UV life is no longer a major issue when fabric is properly specified for UV-protecting pigmentation (carbon black, iron oxide, titanium white) and/or sealer (like sunblock lotion). Construction of fabric wings is sewn or taped. In principle, simple sails made from polymer roll-stock polymer could be made at many meters a second, in one super-factory, to power the world in a year or two of production. Field repairs are fast and cheap. Its mostly outdoor jobs, “sailing in the sky”, based on supervisory auto-piloting rather than full control autonomy.
This video is great because it shows SpaceX using SS NPW-derivative wings to return large launch components from the edge of space to a precise landing. Andre Bandarra recreates a SpaceX SS wing at subscale, with a bit of advice from Ozone, a top fabric wing maker for extreme sports. It shows how one can make a good AWES platform with nothing but a sewing machine and some polymer fabric and line. One can also buy cheap COTS TRL9 polymer SS kites, to instantly be working at the frontier of AWE, the next wind energy revolution.