A new design

'Your team could be in for quite a bit of experimentation.'

I hope so! It's a great way of learning.

To be fair Eric's reply on wing sections was in reply to a query by crash happy.

Fantastic project, I've got a string of ideas but haven't got the time to list them all right now, I'll post them ASAP.
One thing I would like to know is some data on the solar cells.
What is their weight per square meter?
What is their typical output on a bright but overcast day and a sunny day? ... in fact as much tech data as possible.
What dimensions are available?
How flexible are they?
Any idea of their tensile strength?
What batteries are you using? ... According to my Google Home Mini, Lithium Polymer are sleeker and thinner, but Lithium Ion have a higher energy to weight ratio and cost less to make. ..... Worth thinking about.

You've got my brain working again!

Pol.

Steady on there Pol ! How many other projects have you running at the moment ?

Hi Phil.

These are the solar cells that I have in mind. www.altadevices.com/wp-content/uploads/2...rporate-Brochure.pdf. at 280 gm/sq m and 26 % efficient they really are amazing.

I've been in contact with the company and the bend radius around X and Y axes is a lot tighter than the expected curvature of a wing. If the wing was to be curved to the bend radius of the cells it would suggest that the aircraft had crashed! I don't think curvature is an issue, but fatigue in the wiring might be if long duration flights are considered.

LiPo just doesn't cut the mustard for specific energy. 150 W-hr/kg is far too low. Lithium-Sulphur batteries are starting to emerge with specific energy of around 350W-hr/kg with potential to go up to 500. There are life-cycle issues with this technology which might limit the mission life, but there's a lot of money being out into the tech by the electric car industry. One advantage of Li-S is they appear to be much less susceptible to temperature effects than LiPo so they may be good for high altitude flights in the distant future.

I've done thousands of simulations of these flights over the last few years based on bright sunlight. The best flight profile for this type of aircraft is to fly high and well above weather, 18-25km is ideal, so I'm tending to ignore cloud & shadowing for now. Clearly we can't fly that high in the UK without a lot of paperwork so that phase of testing will have to be overseas. You can see why temperature effects on battery chemistry become important as the outside air temp will be around -60C to -70C. LiPo will die at that temp.