This series is an extended musing on what might happen with a really robust solar energy industry that, instead of trying to outcompete all of the other electricity providers, using the relatively low-cost energy, both heat and electricity, to create a product that otherwise is relegated to irrelevence because of scarcity – carbon nanotubes and nanowires.
I discussed blimps – airships without internal structure – as an application of carbon-nanofabrics, because of their great strength and light weight.
In this part, I will briefly explore the uses of carbon-nanomaterials in the construction of balloons and tethers. Like blimps, a super-light, super-strong fabric can create a balloon that can be bigger than those currently employed as weather balloons, which loft very high in the atmosphere.
Currently, balloons are not used much because they lose helium (which is expensive) and fall back to earth, and they could be at their most useful very high in the sky, which means that they cannot be easily tethered to the ground, because the tether, if made with steel cables, would be so heavy it would drag any balloon made of conventional materials back down to the ground.
A carbon-nanofabric balloon, filled with stronger-lifting hydrogen, could be very large. Large enough to support several key pieces of infrastructure – a moisture-capture mechanism of some kind, a suite of photovoltaics and you have a hydrogen-generating plant. This way, as the pressure drops as hydrogen is lost through the balloon’s membrane, it can be replenished without coming down. Also, a cable of carbon nanomaterials can be made incredibly strong without much weight.
So now we have a balloon that can stay high in the atmosphere, above most of the clouds (but not all, because then it wouldn’t be able to make its own hydrogen) and tied to the ground with an essentially unbreakable cable. What is that good for? This brings us to a neat feature of carbon – it is an electrical conductor. In naturally occuring forms like graphite, carbon has a lot of resistance, so it is used for lighting elements, but early research with nanotubes and nanowires suggests that they can be quite efficient conductors. So what we’ve got is a wire leading into the sky as a permanent installation, 12,000-20,000 metres long. As the wind acts on this it pushes against it a bit, but if the balloon is lifting strongly enough it will resist the effects of the wind, and a huge amount of friction gets generated across the whole length of the tether. This is do two things – one, it will create a very strong static charge – more free electricity. Unfortunately, the other thing is draw lightning. This is free electricity happening rather faster than easily managed. However, we have spent a lot of time getting good at redirecting lightning that hits our power lines, so we have a temporary solution. Ultimately though, we may be able to build capactity to capture lightning strikes and use them more productively.
So free power is one use, but there are many others. Tethers could be used as launchers for gliders, blimps, and drones of all types. A set of electromagnets could be wrapped around the tether, and use the same principles as a monorail to lift almost any payload (assuming a large enough balloon). It could be used in the same way to bring blimps and dirigibles down, against their lift, so they wouldn’t have to power themselves down with their maneuvering engines, which would make them lighter and leave more lifting power for cargo.
A tethered balloon is a major hazard to navigation of air traffic, but it might be possible to put sensors along the length of the cable, and use stored electricity to “flex” the cable out of the way of flying hazards.
In part four of this series, I will discuss dirigibles – blimps with an internal frame structure – one of the most interesting applications of these carbon nanomaterials.