The sun is not enough

Let’s talk our turbine’s energy needs. Koski & Grcevich (p. 83) mooted solar. For the following, I'm not even looking at alpha: aerofoils force surface-area, so it's surface-area only I'm lookin' at. I'm also assuming magically powerful propellers sans propellant because why not. UPDATE 8/13/2020: perovskite and organic may let us get away with light solar panels, at least.

Venus unclouded in thin-atmo with the sun straight overhead gets 2620 Wm^-2 irradiance - maximum. (We know it's cold up there, so the exosphere is blocking quite a bit of the infrared.) Say I have a 20% efficient solar panel (assuming no windows; although transparent solar panels do exist, currently at 10% efficiency). The rest of the radiation will reflect away or heat the payload. If I coat the top half of my 300 m² wing with that: 2.620 * 0.2 * 0.5 * 300 = 78.6 kW. Since we're right over the clouds we get the full Venus' 3/4 albedo, so we coat the bottom too: add 58.4 kW to that. I assume we fly at 11 AM (forever), relative to the sun, rather than at noon; so we can use the front of the perma-plane so's to free up the back for the turbine. For drag, we were requesting 2025 N: to overcome that in this wind: 200 kW.

So for solar, I’ve got 458 * A of wattage - again, maximum - to counter 675 * A watts of drag.

It may seem counterintuitive but we’re not fixing this with wing surface area, nor with a better turbine. As mentioned lightening the load and/or hoping for that Hadley updraught aren’t relevant either; such just shortens the wingspan we need. If we had 40% efficiency on the solar panel, and/or drag coefficient much less than 0.015, we could do this. But even a robot drone lacking life-support gotta carry a payload beyond just a wing and a turbine, raising the drag. And I class 40% solar efficiency as Unobtainium. Especially once we start sacrificing efficiency for alpha, which we will need to do.

And nah bro, or (here) sisses: we ain't fixin' this by letting these planes run further below. That gives us air density but we're in the acid cloud layer. So we've not only shadowed our cells from the sun's full(ish) 2620 Wm^-2 but we've had to roll up a plastic shield over them, too.

One option is to use a WORSE turbine. I'll deal with that tomorrow - here I'll just note we've already lost Koski's & Grcevich's (tantamount) hope for forever flotilla, let alone raised up an escape-velocity rocket.

Solar power up here is useful, but insufficient to carry an aeroplane in daylight. Additional energy to do runs from vessel-to-vessel, or just to entertain tourists, will require batteries at the very least.

UPDATE 8/12/2020: Solar from L1?