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Is there any hang glider with solar sheets on top that can charge the e-trike or the e-Lift's battery in flight ? Just like the Sunseeker...

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I think you've got your terminology crossed here (but it's not your fault - your sources don't seem to clear on it either).

A hang glider is by definition a solar vehicle: They're non-motorized, and the pilot keeps them aloft by seeking thermal lift (created by the sun shining on the ground and heating it up) or ridge lift (created by wind striking the side of a mountain/hill (ridge) and being deflected up.
Both of these rely on the sun (either directly heating the local ground, or unevenly heating various parts of the Earth's surface, ultimately creating wind).

What you're referring to would be a solar-powered ultralight aircraft -- basically a hang glider with a motor strapped to it, or possibly an electric powered paraglider.

One could conceivably create a solar-powered ultralight using flexible solar cells on the wing - in fact a little Googling reveals that it has apparently been done with an electric paramotor (a type of powered parachute) (A little more Googling reveals this wasn't as cool as I previously thought - they seem to have been using a support vehicle to recharge their battery packs (with solar cells).

As far as I'm aware no such vehicle is commercially available at this time (May 2014), but the materials and technology to construct such a vehicle are certainly available (the folks over at the Experimental Aircraft Association could probably provide guidance on building something like this), and it wouldn't surprise me if commercial or kit-build solar ultralights become available at some point in the future.

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  • $\begingroup$ I wish they had posted a clear image of the solar paraglider... $\endgroup$
    – Ayan Mullick
    May 30, 2014 at 9:16
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    $\begingroup$ @AyanMullick I did a little digging and it turns out that solar paraglider isn't as cool as I thought it was (they didn't mount panels on the wing or cage - they hard a support vehicle doing the charging). The principle of solar cells on the wing still seems sound though (effectively making the vehicle a motor glider - charge the batteries while the motor isn't running, draw from them when it is). $\endgroup$
    – voretaq7
    May 31, 2014 at 18:29
  • $\begingroup$ @voretaq7: i'm trying to define the relation between a paraglider and solar energy. Is the definition of solar vehicle actually correct? Wikipedia defines a solar vehicle as one that can use solar energy directly. A hang glider or a paraglider can't directly convert the sun energy. It happens on the earth's surface. $\endgroup$
    – mxlian
    Aug 20, 2015 at 9:05
  • $\begingroup$ @mxlian I am deliberately using the term imprecisely in my answer, but if you want to get really pedantic about the definition I would argue that the Wikipedia article is wrong in its premise: The only true "solar vehicles" are ones using solar sails. Anything else is doing some kind of conversion (and if conversion is OK at that point we're just artificially constraining the definition so it doesn't include an engine powered by Jet-A refined from oil made from dinosaurs that ate plants that grew because of sunlight millions of years ago :) ) $\endgroup$
    – voretaq7
    Aug 20, 2015 at 15:56
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    $\begingroup$ @voretaq7, I think the definition is that conversion is allowed as long as it is happening on board, which sounds reasonably self-consistent to me. $\endgroup$
    – Jan Hudec
    Sep 17, 2015 at 19:08
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I don't believe it can be done. The area of a tandem wing isn't large enough. With solar power at 1kW per square meter that will be 15 horse power but the conversion efficiency is not 100%. It is more like 20% so you are looking at 3 horse power. A typical trike needs a minimum of a 25 horse power motor. For example the electric Icaro uses a 10kW motor and it's not even Tandem. The wing area would only be enough to provide 20% of the needed power.

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Solar power on Earth peaks at somewhere between 400W and 1.3kW per square metre, in theory, at midday.

In practice, we can typically expect more like 40-70% of this to be available due to inefficiencies in the solar panels and the fact the wing wouldn't be pointing directly at the sun. This is discounting clouds, and only at midday. At any other time, the amount available is lower.

Taking the best case scenario (1.3kW at midday at the equator, 70% available) then we still only have ~910 watts, or a little over 1.2 horsepower, per m^2

Let's take a typical hang glider: a Wills Wing Alpha 210 has 19 square metres of wing area. That would give 17 kW, or 22.5 BHP. In theory, that's more than enough to get a microlight into the air, if you can keep the weight of the battery, motor, and solar panels down.

In practice, though, are you really going to be flying at the equator, with your wings perfectly level, at midday?

And more importantly, are you really going to get a 17kW motor, 20 m^2 of solar panels, wires, and a battery (pretty much required) into the weight of a hang glider that weighs, itself, less than a typical person?

It's theoretically possible to make some kind of small ultralight type aircraft solar powered, but probably not until we find a way to make lighter motors and lighter solar panels that can take advantage of the wing area without causing weight/stability issues

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  • $\begingroup$ By solar hang glider I mean ; 1. the hang glider would take off on its fully charged battery 2. It'd have solar panels on the wing that would charge the battery while one is soaring with the engine off and also in normal cruise flight. How substantially would that improve the endurance of that machine.. $\endgroup$
    – Ayan Mullick
    Apr 27, 2016 at 23:37
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    $\begingroup$ If you're just looking to use the battery to extend the range then that's more feasible - but the weight of batteries, solar panels and motors, even if the solar panel area required is reduced, would still be significant. Hard to say exactly, but I'd still put it under the 'not quite feasible yet' category $\endgroup$
    – Jon Story
    Apr 28, 2016 at 1:22
  • $\begingroup$ Even with these light weight flexible panels....? $\endgroup$
    – Ayan Mullick
    Apr 30, 2016 at 0:21
  • $\begingroup$ Even if we believe their claims on the capabilities of those panels, which seem... Astounding... You'd still need well over 100 of their largest panel to power an ultralight $\endgroup$
    – Jon Story
    Apr 30, 2016 at 1:22
  • $\begingroup$ But with just the wing area with solar panels; wouldn't that charge up the battery considerably while the pilot is soaring with the motor turned off for a couple of hours...? $\endgroup$
    – Ayan Mullick
    Apr 30, 2016 at 12:51
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If you only need a few minutes prop power to gain altitude and have flexible lightweight panels on top charging the batteries for several hours then you could theoretically travel anywhere without an aerotow or hill thermal to get you up each time. The others replying here seem to be assuming continuous power capable of supporting the engine at full revs is necessary when actually you only require a few minutes to reach enough altitude. Then you can catch thermals and only fall back on the motor if you lose too much height.

These small motors taken from model aircraft give 10 minutes of thrust but can be used intermittently for hours. Combined weight of 4.4kg I think including the batteries. That is without adding a 1.8kg flexible 100 watt panel.

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    $\begingroup$ Welcome to Aviation! Please expand on your answer with technical details to help it move from being a comment (and downvoted/deleted) to an actual self-contained answer. $\endgroup$
    – CGCampbell
    Mar 21 at 13:26

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