Solar Impulse. Nice page for those who do not yet know it.

Solar Cells: Status at Iowa Thin Film (Jan. 06)
State of the art are self adhesive modules with 0.7Wp which weigh
in at 5.9g with dimensions of 270 x 90mm. Taking an average 25 of
them for each cell of a standard M-sized 35-celled paraglider gives
5.2kg of solar cells - which is acceptable - and a peak power output
of 630W - which is low.

Projected area-fill factor is not optimal with 15m² for a 30m²
flat area glider. Power output of the cells is not yet really good, but,
well, we talk about state of the art cells you can actually purchase
(at guessimated €8000). Now double the values for an area-optimized
glider and optimize the area-fill factor and you get 2.5kWp with
off the shelf cells....not bad!

Still, a factor of 2 from better efficiency would be great, note that
Iowa cells clock in at only about 2.9% efficiency, a factor of 6 below
state of the art c-Si cells.

Motor Progress: Discussion on German Board (Nov. 2005)
Since E-Motors grow larger for modell airplanes, the discussion
on electrically powered paragliding is starting and looks very
promising with state of the art components. LiPo batteries
weighing 4kg should allow for about 500m climb. Look into
the discussion here.

Solar-Powered Blimp for Wireless Communication (Dez. 2004)
Just wanted to hand over the report of Economist on 13km high
flying solar-powered blimp to be test soon.

Some Discussions (Okt. 2004)
Discussion on low powered flight with some nice links(German).

Another solar plane (Feb. 2004)
Completing the links below to manned heavier than air solar planes,
have a look at the SUNSEEKER. It looks gorgeous! (sorry we missed
it before).

Brushless motors for 1:2 large scale model air planes (Feb 2004) 

Paper-thin c-Si solar cells with 20% efficiency (Jan 2004)
The Fraunhofer Institute in Freiburg, south-west Germany has
presented a 37µm thin solar cell with an efficiency of 20.2%.
Their objective is to reduce the amount of material used in
producing the solar cells and they were using a cheap laser
technique for backbonding. Here, we are talking c-Si cells, so
whether the flexibility is compatible with a solarparaglider has
to be seen. But note: according to the estimates, such cells
would make a solar paraglider fly with a safety margin of 2 !
Download their press release PDF or go to their homepage.
 
 
   

Update on VHF-Tech solar cells, now "FlexCell" (Jan 2004)
VHF-Tech has moved to a new site an is offering a battery charger
based on their 50micron thin solar foil technology. Together with the
textile it weighs 500g for 4W and 0.17m². Makes 2.3% efficiency.
Specs for the solar modules which are extensively coated also comes
to 800g/m² although as we reported before the solar cell itself would
weigh about 50g/m².

Thin film solar cells on steel or below glass (Jan 2004)
Although we aim for plastic-foil based a-Si solar cells, it might be
interesting to note that Uni-Solar is making stacked solar cells on thin
stainless-steel sheet: "Using a roll of flexible stainless steel sheet that is a
half-mile long and 14 inches wide, nine thin-film layers of a-Si alloy are
deposited sequentially in a high yield, automated machine to make a
continuous, three-cell stacked structure." Although much too heavy for
our purposes, it is an interesting step in the right direction. They claim
"... our triple-junction products deliver more energy per rated power
than the conventional crystalline products." which would mean 14-17%,
an excellent value for a-Si solar cells. Their specs are 60W from 1m²
which means only 6%, with comparable better performance at low light
intensity. However a (fully packaged!) flexible module weighs 3.5kg/m² !
Shell is also delivering CIS thin film solar cells, the modules however are
conventionally packaged below glass.

Large-cell paragliders with high performance (Jan 2004)
Nova demonstrates with a clever line plan that paragliders with wide cells
can be very performant. The new Syntax is claimed to have a 8.3-glide.
For the Syntax L we estimate a cell width of almost 40cm. Also Skywalk
is showing with its Mescal a performant low cell-number paraglider.
 
 

Transparent Paraglider, 1994 (Jan 2004)
The most practical design for a solar powered paraglider would involve the
solar cells below a transparent top surface. Here is a link to Jérome Daoust's
homepage showing a transparent (albeit heavy) paraglider which actually flew.
Jérome writes: "A transparent plastic wing, flown by the "invisible man" at
St-Hilaire du Touvet, France, 1994. Made of a thick gage plastic, it is heavier
than a normal wing (hard to inflate), but still flies."
 
 
 

Additional Area from "Solar Ladder" ? (Sept 2003)
Janez Kriznar notes that one should think about more 
area to attach solar cells and points to examples of huge appendixes
shown at St. Hilaire. To quote his mail: "My idea is to make layers of sol-cells
swinging on a "rope ladder", like some kind of an up side down dragon-kite.
The pilot would just unroll the "ladder" underneath on some decent height."
(see picture to the right). There might be more efficient ways to do this,
but for sure its a start. Janez also doubts whether even 10hp would be
enough to allow for a decent ride in sink conditions.

Solar Powered Paraglider for 4th generation mobile network? (Aug. 2003)
There is a large need to install flying platforms at a height of 20km for
the next generation of mobile phones. Besides planes (see below) driven
by solar power, it might be even possible to use a paragliding-based
approach. Scientists at the University Stuttgart, Germany, have probed
in this direction and have a functioning rescue paraglider. While this is nice
for delivering food or medicine from the air (and to rescue any flying
platforms), one might fantasize about solar paragliding driven flying
platforms. However the conditions are not easy: -60°C, winds of up to
130km/h and an air pressure of about 7% as compared to normal.
Phil Pesavento (inquire for email) notes that high flying Paragliders were
investigated beginning of the 90s by John D. Nicolaides, published in the
AIAA proceedings, 90-3282-CP and 95-1851CP. Experiments show that
paragliders could even fly at the supersonic speeds up there.

With solar power to the Stratosphere (June 2003)
Model solar airplane Zephyr is about to start. Perhaps 8m² wing area,
12kg weight overall with a solar output of 1kW. Hm... getting there!
[read] [Thanks, Arnaud]

More from Skybrake (June 2003)
We quote from his mail: "Bob at astrolight electric motors stated " 100 watts of
available solar flux per square foot or 1000 watts per square meter " and that
"for the motor to produce 10 hp then 10 kW must be generated."  The motor
would "cost $5000". (same motor as GM sunracer, it weighs in at six pounds
and has an output of 10hp) so motor weight will not be a problem.

"Based on that info my calculations are: 1000x30m=30,000 (available solar energy
to a given 30 meter wing) then multiplied by the current effiency level of available
2003 modern silicon thin cells  which is 5% or 1.5 KW available, not enough less
you can spin a really big prop really slow which would be totally possible and feasible
if you had a folding prop and did a tow launch so that prop clearance to the ground
would not be an issue for take off portion of the flight. It would require the prop to
be slung far enough behind or in advance of pilot to be clear of the lines..and would
provide a very gangly but newsworthy demonstration craft.  This could be built
and flown today...."

"But...a 'simple'  advance of the solar cells efficiency to 34% would yield the full ten
horses needed to provide ample thrust from a  51 inch paramotor prop in a standard
cage and using standard takeoff procedures and a highly efficent wing like the ten.
All in practically silent, incredibily reliable, phenomenomally enduring (run as long as
sun is up), insanely light 3kg motor + 6kg harness/frame/redrive = 9 kg all up.
Every paramotor pilot in the world would desire one.". We agree!

Question to confirm rumor information (May 2003)
Rumor has it that there were experiments with battery powered electrical paragliders
in Germany or Austria. They were able to fly 8 minutes with a propeller of 1.4m and
a unit weight of 38-40kg (probably mostly due to the batteries). Anyone has more
information on this? Mail us.

Doubling the glider area gives 9.1 glide and 0.7m/s sink at 25km/h ! (Apr 2003)
Good news from a theoretical article in the 'Gleitschirm Magazin' March 2003
by Peter Bruggmüller. He estimates the effect of scaling the glider size.
Amazingly, his model calculations show that both the glide and the min-sink
improves nicely when he extrapolates a standard glider of today with a
projected area 24m², trim speed of 35km/h, min. sink of 1.1m/s and glide of 7.7.
Upon doubling the projected area to 50m², which is an area we would like for
a solar paraglider, he finds that not only the min-sink is much lower at 0.7m/s,
but also the glide improves. However the velocity will drop to 25km/h - which
is still not too bad. The tendency to tuck will increase, but knowledge to optimize
this has increased much over the last years. For a solar paraglider this means that
a slower, larger glider would be about 3-fold easier (due to 2 x higher area,
1.5 x lower min sink) to lift from the ground. This sounds very promising.

Electric Motor Technology from E-Bikes? (Mar 2003)
Input from Arnaud Finne confirms our understanding that electrical paragliding
must be established prior to delving into solar powered paragliding. He found a
good source for electric motor technology: Denali electrical bikes. They feature
electrical motors with average power of 1kW - yet 10kW intermittend power -
running for 15minutes to 2 hours depending on usage from a 600Wh Genesis
high density accumulator. A basic bike lists at $2800. The bikes however weigh
in for 50kg, probably 20kg coming from the bike, 15kg from the battery. First
electrical paragliding won't be a light sport unless improved solar power kicks in ...

Update of Ideas (Jan 2003)
Feedback from Skybrake confirms the basic math of power consumption of around
P = m x g x v = 120 kg x 9.8 m/s^2 x 1 m/s = 1200W if all mechanical and
electrical efficiences would be 100%. Link to research on flexible solar cells based
on CdSe can be found here (weight probably higher than VHF cells below).
Independent from this input, we want to keep up the idea that tests on electrical
powered paragliding could prove interesting for one-man electrical 'towing' with
an electrical wire to the ground.

State of the art of comp gliders (Jan 2002)
Data from recent prototypes of Airwave ('ten'), reported by Adrian Thomas
might give a min sink of about 0.75m/s at 25km/h. This would mean that
taking a comp glider might reduce the power requirements.

Strategy for first steps (Jan 2002)
One should not concentrate on a glider which can start from the ground
by itself. Establishment of techniques to reduce min sink or enhance
glide by solar cells is enough motivation for the first steps.

Second startup on foil CdSe solar cells (December 2001)
They have not yet a website. Using tricks to achieve deposition,
they can deposit CdSe thin film solar cells on foil. CdSe thin
film solar cells might have higher efficiency than a-Si.

Swiss startup on foil a-Si solar cells (November 2001) 
See at vhf-technologies. Their cell has 5% efficiency at a weight
of 1W per 1.5g or 50W/m² and estimated 75g/m². Typical dimensions 1m x 1-30m.
In terms of weight this is a breakthrough. From an area of 30m² we could
expect 1.5kW peak power.

History of Solar-powered planes (October 2001)
A nice overview over solar powered planes can be found (in german)
at www.solarflugzeuge.de. There is a nice description of the Solair II
(see also here), one of the most recent solar powered planes.