High-flying drones on a leash could blow traditional wind turbines away We may be inching closer to a post-turbine wind energy future if a grant awarded to a University of Bristol boffin for wind-harvesting, ground-tethered drone research is any indication of things to come. Bristol flight dynamics and control lecturer Dr Duc Nguyen was awarded £375,000 ($479,000) from the UK's Engineering and …
It's the weight of the 'leash' that I think will be the issue here.. The same reason the 'space elevator' never happened.
Yes, it can get to high altitudes, but what force will that piece of string need to withstand, and how long will it need to be? What happens when it goes out of control and cheesewires a nearby town?
https://energypedia.info/wiki/Introduction_to_Airborne_Wind_Energy
In the "ground generation" and "rotary" concepts, the generators would be wincghear at the ground station, so there isn't any need for power transmission along the tether (except for control and monitoring etc.). For the airborne generation yes, you are right.
But for the two ground-generating concepts the tether still needs to be mechanically strong and flexible enough to transmit megawatts of energy. For just one megawatt, it would need to be unrolling at 10 metres/sec while tugging 10 tonnes (100kN) or 1 m/s pulling 100 tonnes (1MN). It can only produce short bursts of power until the string is fully extended, and the kite then changes tack to a lower-force configuration while the winchgear turns motor and reels it in for another go.
Sort of ok in theory, but a 100 ton crane rope is not light, and it would weigh the 'kite' down to the ground. Never mind if the line has to be many kilometres long.
Carbon nano-tube cables are in development for lift systems where failures could be arguably more catastrophic but I agree that potential for problems due to the multidirectional stresses for such systems will hinder any kind of regulatory appoval.
But anything that allows wind capture in the 200m sweetspot above the ground that doesn't require building massive concrete towers and transporting massive 100m rotor blades should be welcomed.
…the generators would be wincghear at the ground station…I'm sorry, I can't for the life of me figure out what was typoed here. It looks like 'windshear', and that broadly fits the context, but doesn't fit that sentence grammatically. What was it supposed to be?
ETA: Ah, you do mention 'winchgear' further down, which still doesn't quite fit grammatically, but is close enough that I'll assume it was intended.
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In the "ground generation" and "rotary" concepts, the generators would be wincghear at the ground station, so there isn't any need for power transmission along the tether (except for control and monitoring etc.). For the airborne generation yes, you are right.
It's fine. First we re-invented windmills. Now they're reinventing barrage balloons. People shouldn't be so negative. These will greatly contribute to the reduction in carbon from air travel, because who in their right minds would fly anywhere near these things? But like barrage balloons, these would also contribute to UK air defence and preventing pesky Russians (or anyone) flying into our airspace. They may also provide free hedge and forest trimming when cables snap, and create jobs for roofers when the aircraft land.
I can't imagine insurers being very keen on this solution in a densely populated island like the UK.
(on the plus side.. Starship landed! Sort of.)
The initial use case would be much smaller; I'm betting that they're more expensive per watt generated than turbines sitting on the ground and would mainly be of use for generating a bit of power when the wind's low at ground level, to smooth out the variability there. 10% of a medium-large advanced economy's power budget isn't 'modest' by anyone's standard.
I'm a former keen model flyer who used to fly F1A class self-towed tow-line launched gliders and so know just how much line tension a even a 420g, 2.5m span model can generate (I set my tow hooks to open at 16kg line tension) so I like the concept as applied to power generation and understand the sort of energy thats available.
However, with my other hat on, that of a glider pilot, I'd want to know a lot more about the governing regulations, where these devices would be operated, what, if any, height restrictions would be applied to them, and also what visibility aids and on-board conspicuity electronics would be mandatory. From the pictures I've seen, these devices look as though they'd be quite hard to see when in the air without these devices: I'm very well aware of how difficult an airborne 15m single-seat glider is to see from a km or two away and these things would have much less cross section than any glider when viewed from approximately the same flying height.
Around here (within sight of Emley), modellers normally only fly with line of sight on relatively clear days. Hang gliders similar, some launch from the same hill as Holme Moss mast or other hills around but don't normally go cross country. The nearby airfield (Crossland Moor, also known as Huddersfield International Airport) handles larger light aircraft but they look at the maps as pointed out above. Balloons pass by occasionally, but again on calm clear days. None of the above should be flying at night, and we are pretty much smack on the approach to MAN and sometimes LBA so there are various other limits. A large, well known, static mast is the least of your worries.
For your examples: I read my maps. I've installed a scrolling GPS mapping system which shows forbidden air space of various classes as well as current NOTAMS and tall obstacles as well as my task fot the day. I also carry an up-to-date paper map as a backup for thre GPS system. Consequently I can say that I would not be close to either of your examples because:
- Sandy Heath is inside the London Control Area, so private pilots won't be allowed in although you *might* get permission on a slow day. For instance I know (personal communication) that the replica Alcock & Brown Vickers Vimy was allowed to cross London CTA on a ferry flight soon after it had repeated Alcock & Browns Transatlantic flight.
- The Emley Moor TV tower will be on the relevant 1:500,000 UK air chart along with other similarly tall structures, Danger Areas and no-fly zones such as Salisbury Plain.
You can probably stick small turbines almost anywhere. The sides of buildings, storm drains, water pipes, estuaries, underwater anywhere with a tide, sewer pipes. You'd need to filter what passes through them to avoid them getting clogged, but a lot of smaller ones may be better than a few bigger ones. Easier to maintain too.
I've always wondered whether we should be using better lenses for solar cells and maybe looking at using the focused heat rather than the light. Someone has probably bagged a grant for it.
Heliostat-based solar energy plants are a thing. As are long lines of parabolic mirrors to boil water in pipes and turn a steam turbine.
But, they are often less efficient than plain photovoltaics, and more complicated to maintain. Heliostats need movable mirrors with individual servos to track the sun onto the target, whereas PV panels just sit there..
Small wind turbines are also inefficient and don't catch nearly as much wind as big ones - partly due to the altitude. Wind near the ground suffers drag from the ground, i'd guess.
Turbines in sewer pipes? I hope you're joking. The sewers are bad enough as it is. There's not much head of pressure either.. And as for water supply pipes, you'd only be taking energy out of the pumping system.
There are a lot of bonkers green ideas floating about that are completely infeasible, but nevertheless get funding because investors (often from the oil industry) want to boost their green credentials, while having a few loss-making businesses on their books means they pay less tax. And they know it'll never actually work and challenge their core business, so it's a win-win.
Lenses for solar panels though, i'm with you on that one. Silicon manufacturing is one of the biggest pollution sources on the planet, and large portion of that is from photovoltaics. If we used lenses to concentrate onto smaller more power-dense chips, then we'd need less silicon, and the chips themselves could be more advanced and capture a broader spectrum than the basic panels (which can be made broad-spectrum, but it's expensive to do so for huge multiple square-metre panels)
But then with lenses, they'd still need to tilt into the sun with servos, so probably that's one reason why this isn't common practice
Yeah trouble is photovoltaic efficiency tails off dramatically with heat, which will also increase with lenses, ever used a magnifying glass on a piece of wood? Heliostat based solar energy seems to be a good idea until you see what happens in practice with the decimation of local bird populations via fiery death when they venture into the path...
Solar thermal circulation systems don't lose efficiency in the heat and can even be used to provide cooling. You can even use them in combination with ground-based heat pumps to "store" heat in the ground in the summer and draw it out in the winter… But basically we really need to develop domestic synthetic fuel units that can use a combination: solar thermal to provide steam and photovoltaic to power reactions. Unfortunately, little or no money is going into the relevant research.
You can probably stick small turbines almost anywhere. The sides of buildings …
You can but the vibrations will drive the occupants mad, especially in towns where all the buildings around you produce unpredictable vortices, and eventually the brickwork will fall apart. At which point you'll find you've invalidated your building insurance by sticking the wind turbine on the wall. Simple ideas are simple until you get into the details. (See also: nuclear powered aircraft.)
Would these work as an alternative to land-based turbines where the latter are rejected due to the visual impact / supporting infrastructure needed ?
I'm wondering if they could be run in a similar way to community-funded small water turbines which round here are typically in the 300..600 kW range.
I guess the ongoing supervision overheads would be too much, even if the tether length was limited to, say, 100m.
Would these work as an alternative to land-based turbines where the latter are rejected due to the visual impact / supporting infrastructure needed ?
Nope. I very much doubt they'd ever get regulatory approval or insurance to operate anywhere near a populated area. It's one of those crazy Green ideas that is pointless when there are far safer and cheaper alternatives.
I worked in wind turbine controls/designs for 10 years. While I applaud the development and research of this technology, I really struggle to see how you could have grid-level (GW class) power supplies using these things as the researcher suggests ("$76bn by 2050"). At 25kW that could possibly be useful on a remote windy island without too much birdlife migration (to pass the environmental impact studies) and what happens when the wind stops blowing, does it crash down? Does it need manual interaction to get it back in the air?
If these things are going to be MW class then we're really talking about a 50+ metre wide device. So basically a plane without an operator.
That would get tedious if you had to send a technician out to reset 100+ drone turbines at 3am in the morning during a snowstorm to prevent a power grid blackout, having some quite serious operational and safety challenges (do they collide in mid air?).
My guess if there is going to be a wind rival to the traditional 3-blade horizontal wind turbines, the most likely design candidates would be VAWTS (vIertically rotating devices, that can theoretically be scaled up to MW sizes, I think 1MW is the largest current design, but I suspect you could improve this by several multiples in future generations).
https://reneweconomy.com.au/vertical-axis-floating-wind-turbine-gears-up-for-1mw-trial-in-norway/
Okay, so we're going to repeatedly pull on the tether to spin a generator. It follows that after each 'pull', the kite will have to be re-wound to its starting position - so the power delivery is, at best, intermittent. This means the ground station will probably need to have storage capacity to even-out the delivery. The system will also have to be monitored to ensure it can launch and land safely - so we also need to factor-in a couple of employees on hand for every operational hour.
Now, there's no real point launching one of these in the bottom of a valley unless you spool out enough tether to get above the local hills so it stands to reason that we'll launch these things from a local high spot. We now have a problem delivering that power to the people that want to use it - a long temporary cable, you say? Good luck getting THAT across any highways.
Notwithstanding, you're going to be placing something into the kind of airspace that is used by general aviation. This isn't a major problem as long as you inform the CAA so they can update their NOTAMS accordingly (oh, and avoid any of their pre-defined airspaces) but it does mean usage will need to be carefully considered and definitely pre-planned.
At best, this can only deliver modest power before the tether becomes unmanageably heavy so it favours multiple, small devices rather than one super-scale unit. Remember that feed cable? It's just got more complicated!
So, the ideal use-case is a music festival in a field: I can spec. a handful of these things to help power it. I can run the cables over fields back to HQ so that's trivial. I even have the time to make the airspace requests - but the emergency services will probably veto the application because I'd effectively have a set of barrage balloons blocking access and the speedy evacuation of injured people becomes a nightmare.
In short, who could use this kind of tech.? I don't think the costs and practicability add up.
Anybody remember Makani? It was one of the more speculative ventures by Google. Makani did essentially this. It was shut down by Google a few years ago. They had the drone in the sky, and it worked. It was generating electricity. However, it just wasn't practical enough to be commercialized, I read.
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