Considering its -50.C at that altitude but with 50% more sunshine, the
temperature
difference seems ideal for sterling generators (rather than solar).
-----------------------------------------------------------------------
Ashley Clarke
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"habshi" <habshi@anony.net> wrote in message
news:42f0f61d.10074701@news.clara.net...
Jim try and say something useful in this thread except the usual islamic
moaning and
whingeing. Just as a sail can tack into an oncoming wind , why cant these
planes do the same to get
the energy to stay afloat forever?
excerpt
European efforts
In 2000, the Belgian Flemish Institute for Technological Research (Vito)
set up the Pegasus project.
Pegasus (Policy support for European Governments by Acquisition of
information from Satellite and
UAV-borne Sensors) was designed to spearhead Europe's development of
solar-powered UAVs that can
stay airborne for long periods.
Mercator: The craft has a wingspan of 16m
"One of these craft could get anywhere in the world in 24 hours," explains
Dr Rogoyski.
"A UAV will be able to keep up over a particular part of the world for
months at a time, whereas
satellites have to continue travelling in orbit."
Precise, high-quality images and data can be sent back in under 30 minutes
to a mobile ground
station which can then disseminate images online.
But for a solar eternal plane to be exactly that it needs an efficient
energy harvesting, conversion
and storage system that will work when the Sun has set.
"We use a lightweight solar array coupled to lithium-based rechargeable
batteries. They are
incorporated into the carbon fibre airframe which gives us a low-mass
structure capable of flying at
high altitude," says Dr Davey.
The challenge is to make the craft as light as possible, carrying payloads
of 2kg, while making it
robust enough to withstand the extreme conditions it has to navigate.
Temperatures at the altitudes
UAVs fly drop to 50 degrees below zero.
Based on computer modelling, the craft QinetiQ has developed thus far
could complete a day-night
cycle. It would use solar power during the day, while recharging the
batteries, which would then
provide enough "juice" to fly at night.
It seems straightforward, but it is only the improved efficiencies in
solar cell and battery
technologies, even over the last year, that has made this at all possible.
The light weight is achieved by using paper-thin solar panels
"The key technologies are solar cells and batteries. Battery technology is
receiving billions
worldwide and it is a very rapidly evolving technology," says Dr Rogoyski.
The solar panels on the craft are paper thin and deformable so they hug
the surface of the plane
itself, cutting out excess material.
Initial tests on a 40% scale model of the QinetiQ Mercator UAV have proved
successful.
"The technology we have right now will enable us to stay up in the air for
60 hours, but we will not
be trying that tomorrow," says Dr Davey. "Trials are planned for next
year."
By then, Dr Davey expects improvements in battery efficiency of about 20%.
.
