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Makani source code released

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Re: Makani source code released

#91

Post by londons_explore »

krisoft wrote: post #81
londons_explore wrote: post #77

Earlier quoted context omitted.

So what's to stop me cobbling together something like the Wing 7 and just leaving it unattended in a field to launch and generate whenever the wind conditions are suitable? If I did, and I got typical government subsidies for wind power, I might earn $10k/year. That ought to pay for all the machines parts if I buy everything hobby grade from AliExpress. The 2nd year is pure profit assuming the craft lasts that long.…

The FAA (or your local alternative) might want to check your paperwork and licensing too.

While it stays tethered to the ground, I don't believe the FAA would be interested? Am I mistaken?

Re: Makani source code released

#92

Post by ZephyrBlu »

winrid wrote: post #33

Some of the code for the tools is fun to read https://github.com/google/makani/blob/c421e4497dd09c86b01725... This is not proper Java, at all. But it's what a lot of Java code looks like because it's a good choice for inexperienced devs or rushed projects.

Other than it being a 2400 line file, what's wrong with the Java code?

Re: Makani source code released

#94

Post by pas »

nikitaga wrote: post #74
cloudwalking wrote: post #56

Earlier quoted context omitted.

X is what Google used to be.

X is still X and Google is still Google. Outside of X, Google was never known for crazy moonshots. Google was always an ad platform with a search engine.

Gmail seemed kind of crazy at the time.

Re: Makani source code released

#95

Post by pas »

londons_explore wrote: post #91
krisoft wrote: post #81

Earlier quoted context omitted.

The FAA (or your local alternative) might want to check your paperwork and licensing too.

While it stays tethered to the ground, I don't believe the FAA would be interested? Am I mistaken?

It depends on how high it gets, because even high buildings/structures can be problematic. (They need a blinky light of course, but maybe more importantly a radar reflector.)

Re: Makani source code released

#96

Post by pas »

fluffy87 wrote: post #86

What was the back of the envelope calculation that suggested this would work?

In the film they explain that since wind turbines extract power based on the area they sweep, their kite would be able to sweep a bigger area more easily. (No need for so much material, no need for a 150m tall tower, etc.)

https://www.youtube.com/watch?v=qd_hEja6bzE&t=6m40s

Re: Makani source code released

#97

Post by ntucker86 »

brandmeyer wrote: post #47
tobinfricke wrote: post #38

Earlier quoted context omitted.

The use of those processors and ethernet were not major cost drivers. There's a very nice technical document describing the network topology titled "A Low-Cost Fiber Optic Avionics Network for Energy Kites" in the collection of technical documents: https://storage.googleapis.com/x-prod.appspot.com/files/Maka...

At this scale, no of course not. But at 100 kW or 10 kW? Remember that the argument is about applicability to other kite energy systems. Margins get very thin when power electronics costs only 0.03 USD/watt for the entire system. It gets harder to hide signal processing costs as the size of the system decreases.

System scale is a crucial component of a cost competitive energy system. I lay out the argument for this in the early part of my section - Airborne Wind Turbine Performance - of the released documentation.

A 100 kW system may prove useful to some niche, but I don't think can be competitive with the utility energy market at large, even if you give away the system for free.

At the larger scales, these electronics are not meaningful cost drivers at all.

Re: Makani source code released

#99

Post by ntucker86 »

tinco wrote: post #84
tobinfricke wrote: post #64

Earlier quoted context omitted.

While our code might be too specialized to help out other crosswind kite power companies in particular, I think the technical document might be quite impactful: https://storage.googleapis.com/x-prod.appspot.com/files/Maka... The chapter "Airborne Wind Turbine Performance" contains some sobering lessons for the field and deserves a close read.

Thank you so much for that document it's so interesting. Interesting lesson from the exec summary: The real world kite underperformed the model by nearly half, and from the numericals it seems like the main reasons we're that the turning radius was about double that what you were trying to get, and that the tether drag was a significant loss that was not accounted for. The next gen model would be the same span but wi…

The Airborne Wind Energy section is general, and discusses energy kite performance in a broad way - the tether drag was well predicted and wasn't a surprise for our prototype.

The inability to turn the necessary tight paths and some degraded aero performance are responsible for most of the performance miss. Also hugely concerning was the struggle to saturate power at high winds.

It is important to separate and highlight tether drag in the context of the purported big benefit of airborne wind turbines accessing higher, faster winds. While they do indeed access higher winds, they do so via tether length and elevation angle, both of which carry losses. The net effect in almost all scenarios isn't a win.

Re: Makani source code released

#100

Post by ntucker86 »

yourapostasy wrote: post #90
tinco wrote: post #84

Earlier quoted context omitted.

Thank you so much for that document it's so interesting. Interesting lesson from the exec summary: The real world kite underperformed the model by nearly half, and from the numericals it seems like the main reasons we're that the turning radius was about double that what you were trying to get, and that the tether drag was a significant loss that was not accounted for. The next gen model would be the same span but wi…

> ...tether drag was a significant loss that was not accounted for... I wonder if some of the losses to tether drag could be made up for by re-purposing some of the wave energy tech to capture energy from the base of the tether as the kite pulls and slackens on the base, or if the tether could be made rigid on demand with some tech in the future.

There isn't a large amount of energy stored in the tether catenary or elasticity. Any hardware to recoup it probably wouldn't pay for itself.

Offshore, there can be a lot of energy stored in buoy motion, and utilizing this can help, but probably in a resonant way that doesn't require additional hardware.

"Rigid" is a relative term. The tether already utilized a carbon fiber core. It doesn't get much stiffer, short of going to exotic fibers or more of them, both of which degrade performance in other ways.

The optimum is going to be closer to a strength limited tether than an overly stiff one.

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