Electrically Powered Ultralight Aircraft

On Tue, 7 Aug 2007 18:09:36 -0400, "Morgans"
wrote in :

I think I recall seeing someone do the calculations of how much solar energy
hits the top surface of a sailplane and wing, and it was still not enough to
motor without thermals, if it was all converted to electrical energy.

Here's one that flew across the US seventeen years ago:
http://www.solar-flight.com/sslink.html

On Tue, 07 Aug 2007 23:14:59 GMT, wrote in
:

Current conversion technology is about 22% at best.

Technologies in the works are promising 50-60%



http://www.boeing.com/news/releases/...60828a_nr.html
ST. LOUIS, Aug. 28, 2006 -- The Boeing Company [NYSE: BA] has signed a
contract to provide 600,000 solar concentrator cells to SolFocus,
Inc., a California-based renewable energy company that is developing
renewable terrestrial energy alternatives.

"Companies on the cutting edge of the renewable energy revolution come
to us because we are the world's leading manufacturer of solar cells,"
said Charles Toups, vice president of engineering for Boeing Space and
Intelligence Systems. "Our Spectrolab subsidiary has leveraged its
expertise in space photovoltaic products to create solar cells with
record-breaking efficiencies for Earth-based applications."

Under the 12-month contract from SolFocus, Inc. of Palo Alto, Calif.,
Spectrolab will build and deliver 600,000 solar concentrator cells
that will be used to convert the sun's rays into affordable
electricity for homes and businesses. The cells produced for SolFocus
will be capable of generating more than 10 megawatts of electricity,
or enough to power about 4,000 U.S. homes. With the average solar cell
efficiency above 35 percent at concentration, Spectrolab's
concentrator photovoltaic cells generate electricity at a rate that
can be more economical than electricity generated from conventional,
flat panel photovoltaic systems.

"Our mission is to deliver reliable solar-generated electricity at
wholesale energy prices, and Spectrolab's multi-junction concentrator
solar cells are key to making that possible," said Gary D. Conley, CEO
of SolFocus. "Spectrolab's cells will be integrated into our upcoming
solar concentrator field test program and then into the first phase of
active deployments."

A significant advantage of concentrator systems is that fewer solar
cells are required to achieve a specific power output, thus replacing
large areas of semiconductor materials with relatively inexpensive
optics that provide optical concentration. The slightly higher cost of
multi-junction cells is offset by the use of fewer cells. Due to the
higher efficiency of multi-junction cells used in the concentrator
modules, only a small fraction of the cell area is required to
generate the same power output compared to crystalline silicon or
thin-film, flat-plate modules.
================================================== ===================

http://www.boeing.com/news/releases/...60815b_nr.html

ST. LOUIS, Aug. 15, 2006 -- The Boeing Company [NYSE: BA] today
announced it has signed a multi-million dollar contract to supply
concentrator photovoltaic (CPV) cell assemblies to an Australian
company that produces renewable solar energy.

Under the contract with Solar Systems Pty. Ltd. of Hawthorn, Victoria,
Boeing will deliver 500,000 concentrator solar cell assemblies for use
at power stations that generate renewable energy for small, remote
Australian communities. Spectrolab, Inc. of Sylmar, Calif., a
wholly-owned Boeing subsidiary, will manufacture the cells. Deliveries
will begin later this year.

The solar cell assemblies will be capable of generating more than 11
megawatts of electricity -- enough to power 3,500 average-sized homes.
"For the past 50 years, Spectrolab has been a leader in space-based
solar cells," said Dr. David Lillington, president of Spectrolab, the
world's leading producer of space and terrestrial concentrating solar
cells. "We have leveraged our expertise in space photovoltaic products
and created terrestrial concentrating solar cells with record-breaking
efficiencies averaging above 35 percent. We are now partnering with
the best of industry and making great strides in reducing the cost of
solar energy to homes and businesses worldwide."

This contract with Solar Systems continues an earlier relationship
between the two companies. In April, Spectrolab and Solar Systems
brought the world's first full-scale ultra high efficiency 35-kilowatt
solar generator online in Australia. The system created a new
benchmark for solar concentrator systems both in system efficiency and
cost, and showed great promise for the future of renewable energy.

"The breakthrough demonstrated by this fully operating, full-scale
system shows the potential for CPV to dramatically change the
economics of solar power. We expect this to be the first commercial
phase of a very large and valuable relationship," said Solar Systems
Managing Director Dave Holland. "Our partnership with Spectrolab
represents a new level of cooperation toward the common goal of
meeting the community's power needs with clean, green electricity."

Solar Systems' concentrators resemble a satellite dish with curved
reflecting mirrors shaped to concentrate sunlight onto the solar
cells. A sun-tracking mechanism allows electricity to be produced from
morning to late afternoon. Small, remote communities are using a
number of concentrator dishes in "solar farms" for energy during the
day and switching to diesel generators at night.

A significant advantage of concentrator systems is that fewer solar
cells are required to achieve a specific power output. Large areas of
semiconductor materials now can be replaced with lower cost
concentration devices. The higher cost of ultra high efficiency
multi-junction cells is offset by the need for fewer cells. Because
multi-junction cells are so efficient, only a fraction of the cell
area is required to generate the same power as crystalline silicon or
thin-film flat-plate designs.
================================================== =============

Orval Fairbairn wrote:
In article ,
Orval Fairbairn wrote:

In article . com,
James Sleeman wrote:

On Aug 6, 4:52 am, Larry Dighera wrote:
Electrically Powered Ultralight Aircraft
It's a nice idea, but realisitically there are too many problems, not
the least of which is battery size, weight, cost and safety. I don't
really see batteries as a viable in the near future (I struggle to see
them as viable in the distant future either).
Look at the problem this way: In an all-electric machine, you carry ALL
of your energy supply with you: fuel and oxidizer -- to make electricity.

With any IC engine, you carry the fuel only -- the air is free (20%
oxygen), so, at 15:1 air/fuel ratio, you would need 90 lb of air for
each gallon of fuel.

Therefore, for a nominal 50 gallon fuel capacity (300 lb), you would
have to carry an additional 7500 lb of air.

That is a lot of weight for a 3000 lb aircraft!

DUH! I meant 4500 lb of air! That is still a lot of weight penalty.


Well, to be fair Orval, you do get the 90% efficiency in an electric
motor, vs the 30% in an IC engine. You'd only have to drop 1500lb of
useful load with the electric motor.

Isn't the useful load of most light airplanes somewhere between 600 and
2000lbs?

wrote:


Just too much hype and inconsistancy for me.



Has anyone done an analysis on the amount of energy required to
produce a vehicle like this vs what it will actually "save" during
its supposed lifetime? Some of these exotic battery materials and
manufacturing techiques take a lot of energy on the front end to
produce, and dispose of and/or recycle on the back end. You have
to factor that into the net energy gain or loss of actual use of
these vehicles.

Gattman wrote:

I agree. It's on the way. Wasn't too long ago that terms like "lithium
ion" and "nickle metal hydride" were unheard of to the common consumer.


It takes a lot of energy to manufacture those batteries ... and recycle
them when they are used up. You have to factor that into the equation.

These batteries have high energy per unit volume but they cost a lot
of money because it takes a lot of energy to produce them.

Larry Dighera wrote:

There is a 14 HP Powered Paraglider (PPG) engine offered he
http://www.poweredparasports.com/Par...#Jet%20Details
They also state that the weight of their engines ranges from 46 lbs.
to 68 lbs.

If a 14 HP electric propulsion system weighing 46 lbs could be
constructed, apparently it would permit the use of PPGs by pilots up
to 180 lbs.

Yeah sure, but its not practical for anything but an hour or two of
playing around on a Saturday afternoon. You can't carry anything or
go anywhere to accomplish anything except maybe brag about how little
energy you used goofing off for a few hours. Its like blasting around
on a jet ski... basically a total waste of energy without producing
any useful work or benefit to mankind.

Don't get me wrong, I love new technology and if you can afford to
spend money on extra curricular stuff like aimlessley cruising about
in solar powered paragliders or jet skis fine. But don't think you
are doing the world a big favor because you used something other
than gasoline to power it.

jimp wrote

In rough numbers, you get about 1 kW/m^2 of energy from the sun on
a clear day.

Current conversion technology is about 22% at best.

Technologies in the works are promising 50-60% (the check is in the
mail and I will respect you in the morning).

One presumes a sailplane is going to spend most of its time sailing
and only using the motor (with batteries) to get off the ground
and occassionaly cruise between thermals.

So most of the time you are just charging the batteries.

That is why I specified cruising with the motor without thermals; to get a
feel on how the extra surface area and high aspect ratio (efficiency) would
mimic a cross country, motor cruise.
--
Jim in NC

On Tue, 7 Aug 2007 21:08:12 -0400, "Morgans"
wrote in :

That is why I specified cruising with the motor without thermals; to get a
feel on how the extra surface area and high aspect ratio (efficiency) would
mimic a cross country, motor cruise.



It's beginning to look like the 21st century indeed:

http://www.solar-impulse.com/en/index.php
Bertrand Piccard and the EPFL unveil project to fly around the
world in a solar powered airplane

Lausanne, Switzerland -- A team of aviators and scientists led by
Dr. Bertrand Piccard, the first man together with Brian Jones to
circle the earth non-stop in a balloon in 1999, announced plans in
Lausanne, Switzerland Friday to develop an aircraft powered by the
sun and capable of circling the earth. The Piccard team envisions
being able to spend full nights in the air by 2007. Piccard will
be assisted by Jones, his co-pilot in their Breitling Orbiter 3
balloon, and André Borschberg, engineer and jet plane pilot. Their
new project, dubbed Solar Impulse , is aimed at demonstrating the
role of high technology in sustainable development. The EPFL
(Swiss Federal Institute of Technology in Lausanne/ Ecole
Polytechnique Fédérale de Lausanne ) is the official scientific
advisor to the project. The EPFL conducted thermodynamic research
in support of the Piccard/Jones 1999 balloon flight, and is the
official scientific advisor to Alinghi , current holder of yacht
racing's prestigious America's Cup.

EPFL, November 28th 2003


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http://radio.weblogs.com/0105910/2004/04/01.html

Solar Impulse Will Circle the Globe in 2009

Bertrand Piccard, the Swiss adventurer who was one of the two
first men to fly around the world non-stop in a balloon in 1999,
wants to achieve the same goal again. But next time, he will use a
pollution-free, single-pilot solar-powered aircraft. The plane,
named Solar Impulse, will look like a glider, but its 70-meter
wingspan will exceed the one of a Boeing 747. Universe Today says
a prototype will be ready next year and that the plane should be
ready for its flight around the world in 2009.

The proposed aircraft resembles a glider, but with a mammoth
70-metre wingspan, exceeding that of a Boeing 747. Completely
covered by solar cells and equipped with possibly two tail-mounted
propeller engines, the plane will be capable of unassisted
take-off and will carry the necessary batteries for night flying.
...

----------------------------------------------------------------


http://www.universetoday.com/am/publ...und_earth.html
Solar Plane Will Attempt to Go Around the Earth

Summary - (Mar 31, 2004) The European Space Agency will be
supplying technology to assist adventurer Bertrand Piccard's
attempt to fly a solar-powered plane around the world. Piccard was
part of the team that successfully flew a balloon around the
Earth. The solar powered plane will have a 70-metre wingspan
(larger than a Boeing 747), and carry enough batteries to be able
to fly in the night as well. The plane would fly at an altitude of
10 km; well above the clouds to capture all the available
sunlight. The first round-the-world attempt will be made some time
after 2009.

Full Story -
Image credit: ESA
ESA's Technology Transfer Programme is to supply state-of-the-art
technologies to assist adventurer Bertrand Piccard's flight around
the world in a single-pilot solar-powered aircraft, ...

The EPFL study says that current off-the-shelf lithium-ion
batteries provide just under 200 watt-hours per kilogram (Wh/kg),
enough to support a single-pilot plane, while a two-pilot solution
would require a capacity of at least 300 Wh/kg.

The plan is to design and construct the first prototype aircraft
in 2004-2005, with initial test flights in 2006. The next step is
to complete night flights in 2007, initially at least 36 hours
including one full night. From then on flying lengths are to be
increased. . Innovative solutions will be required to store the
necessary food and water while reduce weight to a minimum –
familiar problems for ESA engineers designing space missions.

When will the Solar Impulse fly around the world, non-stop? "It is
planned to cross the Atlantic in 2008 and fly around the world
with stop-overs in 2009," says André Borschberg, "To fly around
non-stop depends very much on how quickly we will have higher
energy density batteries…but not before 2009." ...

On Wed, 08 Aug 2007 01:05:16 GMT, kontiki
wrote in :

Yeah sure, but its not practical for anything but an hour or two of
playing around on a Saturday afternoon.

I'll bet you would have said something similar to the Wrights. :-)
Where's you vision, man?

Now here's an electrically powered aircraft that really is playing
around: http://www.nesail.com/videos/jazz.wmv

On Aug 8, 2:21 am, Larry Dighera wrote:
I see what you mean. Unfortunately, the highest power requirements of
aircraft engines are during the takeoff and climb phases of flight.

Hence why i was thinking more along the lines of a electric motor +
reasonable battery coupled to a stirling. The battery provides the
oompfh for takeoff (and other moments of urgency) from stored energy.
The stirling charges the battery, or passes current through to the
motor when the battery is at peak charge (hand waving the bajillion
technical details which I don't know), it doesn't matter that the
stirling doesn't run at peak efficiency at all times, in cruise mode
you'd want it to be at peak and providing more than enough current to
the motor with some spare to charge the battery.

The article I linked to was more along the lines of a direct-drive,
but I think hooking the output shaft from a stirling straight to a
gearbox/prop would not be a good idea, you are stuck with too many
disadvantages and it makes the engine design more complicated than
necessary.

The main advantage of the stirling+battery versus just battery, is
that you remove the requirement for major infrastructure change
(abundant charging points at airports), the stirling just needs some
fuel (which could be anything from mogas to radiant solar heat) and
that's it, no infrastructure change is necessary in the interim, and
minimal in the long term. As an added benefit, you get much better
cruise endurance than battery alone.