Airborne solar wind energy systems (ASWES)

This is a preliminary study, and from
https://news.cnrs.fr/authors/jean-francois-guillemoles at
Centre national de la recherche scientifique (CNRS)
So high references.

I put a link on Makani mentioning the weight of some electric cables on Airborne solar wind energy systems (ASWES) - #25 by PierreB . This is an answer: to extrapolate from this can give a preliminary estimation of the weight of a longer cable carrying more power. Knowing the orders of magnitude is a first step towards evaluating a system.

No.

Explain this to the author. He mentions 6000 m because there are few clouds anywhere, and more time of sunlight even compared to sunny places at only 1000 m. There are clouds at 1000 m high, everywhere, except in some deserts.

In this topic several hypotheses are mentioned, including that of very low altitude (far below 1000 m).

See the first link of the initial comment: above one year lifetime in use.

We are on orders of magnitude, not yet on specifics, as for any AWES without any exception. For example I don’t yet know (after more than 10 years) the lifetime of a flexible kite operating in yo-yo mode, undergoing stress from the alternating phases. I don’t know their real LCOE, and so on.

The author should explain to the reader why he chose that altitude. All he wrote about that is:

The footnote is not relevant to the altitude claim and does not give a direct link to any laboratory study talked about in the footnote.

The author has a narrow focus of research, not including atmospheric science or hydrogen production it seems. I have not been able to find any study by him anyway to find the reasoning for any chosen altitude.

https://cv.archives-ouvertes.fr/jean-francois-guillemoles

https://www.researchgate.net/profile/Jean-Francois-Guillemoles

You’d first have to research the feasibility of using higher voltage cables, the length of the cables, and the power you would like to transmit, all of which can make an order of magnitude difference, if you would like to use a power cable at all.

The first two of those questions can be answered with literature research, so can be done at any time. Knowledge about that can also be helpful to any other architecture so would be good to do anyway, no matter what you think about this concept.

The main problem with photovoltaic energy is that sunlight can be obscured by clouds, which makes electrical production intermittent and uncertain. But above the cloud cover, the sun shines all day, every day. Anywhere above the planet, there are very few clouds at an altitude of 6 km—and none at all at 20 km. At those heights, the light comes directly from the Sun, as there are no shadows and hardly any diffusion by the atmosphere. As the sky loses its blue color, direct illumination becomes more intense: the concentration of solar energy results in more effective conversion, and hence higher yields.1

Under these conditions, the energy source is five times more abundant than on the ground,2 and production is entirely predictable.

Footnote 2:

Given 1000 KWh/year/m² of illumination on a ground-based flat-plate solar collector within the latitudes of France and a high-altitude collector with tracking at any latitude (1200 W/m² x 4380 h/year = 5.2 MWh/year/m²).

“Under these conditions”: I am not sure if the author refers to an altitude of 6 km or an altitude of 20 km. That said “five times” is compared to the illumination “within the latitudes of France”, and the given numbers seem to confirm this claim. And the explains look clear (“…there are very few clouds at an altitude of 6 km—and none at all at 20 km”.)

As mentioned on your second link:

Soper noted that existing PV technology can already achieve yields of three times the northern European average in sunny locations such as Chile or South Africa.

In this case the usefulness of a high altitude installation is reduced in these locations, in a ratio of 5 to 3 instead of 5 to 1. But, as for wind, the sun is not available everywhere in the same way, far from it, which is confirmed by examples from Chile and South Africa.

That, and the rest, are unsupported claims. It gives very little information if it were true anyway. What is the average cloud cover over Sweden at an altitude of 3 kilometers during January for example, or what is the cloud cover at different locations at 3 kilometers vs 6 kilometers. Evidence or sources would be something like satellite or weather balloon data that somehow measured cloud cover at different altitudes and at different locations and times of year.

No. it is enough to know the hours of sunshine on the ground. For example for New York:

At 6000 m altitude, sunshine hours over a year is roughly the same everywhere: 4380 h/year, as mentioned by the author. His claims are clear and fully supported. This is normal: he is a recognized scientist.

No, that’s not how that works. He would need to reference data from for example satellite data to support his claims, or perhaps you for example could find that data to support his claims. Your link is not relevant to this discussion, unless I am missing where it talks about cloud cover at different altitudes.

The issue, anyway, is the unexplored assumptions. The assumption or claim is that 6 kilometers up is the only and best altitude to have the solar panels at. You would like to support that with data, which is not given.

In questioning the information (including the 4380 h/year at 6000 m of altitude) of this renowned scientist, you must provide your objections and support your claims, quoting the sources.

I think the recent discussion came up with a great point; On sunny days, 100 m altitude may be sufficient, with very low cable weight. On cloudy and windy days, higher altitude may be used to get above cloud cover. This would somewhat increase the operational window of the plant.

In cloudy areas, the full length of the tether will be used most of the time: it might as well be used all the time, which will result in fewer maneuvers and cost the same.

In very sunny areas, it will still be necessary to buy the full tether, even if the full length is not used often. Then a short tether (100 m) might be more appropriate and far less expensive, eliminating some few cloudy days.

As the kite will have to come down from time to time, either for lulls or storms, it might make sense to build these as kite trains rather than single kites

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If you going for flying solar? Then you might want to bear in mind that the underwing surface could be lined with reflectors. that focus the light on each section of the kite train. Or even have light collector focus/scatter the light across the wing surface. In mind that there is such things as light guides, prism, lenses and relfectors.

So I already envisaged the use of kite trains. But also the PV orientation face to the sun can to not match that of the kites in regard to the wind. Things would perhaps be easier by using Isotropic kite.

Only at low altitude (and even I am not sure) because solar tethered balloons are large and offer a lot surface to the wind, leading them to lose their thrust by convection and to lie down.There is little possibility for some additional kite to mitigate this effect.

As I mentioned the solar thermal part is also ensured by the black e-film, in addition to provide electricity (about 100 W / m²).

Solar thermal balloons are better when they are untethered.

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It may not have be oriented with the sun to if you channel the light? The top surface are mainly exposed to light. As long as the light can be channeled? It shouldn’t matter which direction it faces? Think

Easy enough too do. Should be easy for a custom set up? Might need a custom preform? Much like a corrugated wind? Im liking what I see so far! For a kw? 10m2 will be need? Which is about the size of a small tarp?
Solar thermal balloons, The untethered version you say are better? Is that because it doesn’t have to lift the massive cables? Trying to get an idea of how that works in practice? Would it ascend to altitude then return to a power dock to discharge?

As for light bending chandeliers? Could the sky train be set up to be like a chandelier?

This discussion continues here: Questions about Moderation - #114 by PierreB

It is a part of the discussion which is not public, and on other points.

So since you have publicly challenged the author, share your objections by supporting your sources publicly.

I have not challenged the author. I have given my opinion on the article.

This is unsupported. Source: no relevant sources referenced in the article.

The bolded part would be the most interesting thing to get sources for, as such a source might also tell us something about what “very few” means and how the number of clouds changes at different altitudes, different locations, and different times of the year.

Examination of wind velocities at various altitudes shows that there are regions where the velocity increase at altitude is considerable. For example one region (east coast USA), shows a doubling of velocity between 300 meters and 1500 meters. This represents an 8 fold increase in power. With wind velocities of 15 - 20 met/sec. we do not require crosswind action and can use a simple turbine system and transfer power to the ground by cable drive. The weight of an electrically conductive tether is more than a cable drive/tether, and the additional weight of a turbine system can be compensated by designing the turbine support frame to provide lift.

I will point out that the author you are quoting here was able to establish his article based on information provided by the electro-chemist Jean-François Guillemoles, producing some informed analysis, without questioning his information as you do.

This is called mutual trust, which can be found among scientists, despite expressed disagreements.

But you have challenged the author and questioned the veracity (in bold) of his article:

I am still waiting for your objections supported by sources.

I agree of course for a simple turbine. A question is if there is some possibility to combine sun and wind, knowing that they can be not aligned almost time.

Again, no, I have not challenged the author. If I had challenged the text, not the author, I would have written something like “this is wrong.” You’d be right to ask for sources then. I pointed out that it has unsupported claims, or questioned the text if you will, which you do when it has unexplored assumptions or unsupported claims.

See my previous comment. The rest of your comment is off-topic to this of-topic discussion.