Silent Flight: PV Powered Blimps

Even with a pv-solar situation where you only realize 50 watts/m^2 the
blimp would still go 17 mph which allows for a lot of options not
possible with a balloon.

In the summer vacation season in the Grand Canyon or some other SW
desert area, the airship would go considerably faster.

There are no economies of scale as far as speed is concerned.
Increasing size only increases lift.

The cost might not be prohibitive. Covering half a 30 m dia sphere
with 1400 m^2 of $300/m^2 pv would cost half a million dollars, but
would displace 14 tons of air.

A lot of recreation related industries can spend that.

The only other alternative for silent flight is to have something like
a hybrid electric vehicle drive train with a good sized battery.

Economies of scale would definitely allow for a heavy battery in a
larger blimp with a longer range.

When you approach the area of interest kill the engine and use the
battery to power the motor for awhile.

Maybe get a police dept to replace a helicopter with an electric hybrid
electric blimp. Not only does the noise wake everyone up but it alerts
the criminals.


Bret Cahill

Even with a pv-solar situation where you only realize 50 watts/m^2 the
blimp would still go 17 mph which allows for a lot of options not
possible with a balloon.

Yeah - but travel by balloon is pretty rare.

This thread was never about commercial aviation but scenic tours. Hot
air balloon tours are quite popular. One got tangled in a high voltage
power line near Phoenix just last year.

Blimp tours with their greater range, flexibility and safety should be
even more popular.

If you have a blimp that
can do 17 mph, you're facing a lot of days where you can only fly
downwind.

What's the point of quiet propulsion on windy days?

The only other alternative for silent flight is to have something like
a hybrid electric vehicle drive train with a good sized battery.

Or a really good muffler on a regular, internal combustion engine. Can
you tell if a Lexus is running from 200 feet away?

Some might want to get closer to a charismatic animal than 200 feet. I
was thinking of flight where you could only hear your own breathing.

The other thing
you need is a large, slow moving prop.

A large slow moving prop is quiet.

Have you ever seen the props on ballistic subs? They are a unique
design that is supposed to be ultra quiet, but I've never seen them on
trolling motors. DoD takes forever to declassify technology.

Anyway we need the compressible flow equivalent. In fact, the quietest
low rpm large diameter air prop is probably has pretty much the same
size and shape as a ballistic sub prop.

A LOT of the noise from an
airplane is from the prop.

Heavier than air aircraft generally require higher speed propulsion
which is inherently noisy.

Most of the work that's made helicopters
quieter has been with the tail rotor.

Still way too loud. Hikers complain about choppers in the Grand
Canyon.

Maybe get a police dept to replace a helicopter with an electric hybrid
electric blimp. Not only does the noise wake everyone up but it alerts
the criminals.

But they want something that can fly faster than a criminal can
run/drive.

Give those meth heads a real workout!


Bret Cahill

Richard Riley wrote:
On Sun, 14 Jan 2007 04:27:40 GMT, wrote:
If you covered the entire surface of the envelope with solar cells,
you'd need to _average_ 0.172 kW / m^2 to get that much power. If
you assume that everything is great and you're getting 1 kW / m^2
coming in, that's 17.2% efficiency.

Total solar flux of 1 kw/m2 assumes noon on a clear day at the
equator.

That's part of what I meant, but didn't make explicit, when I said
"everything is great".

Average flux in North America throughout the year is between
125 and 375 w/m2 depending on where exactly you are.

I found those same numbers at http://en.wikipedia.org/wiki/Solar_power ,
which cites http://www.nrel.gov/gis/solar.html . But that apparently
also includes night and cloudy days, so what's actually coming in on a
sunny day will be more than that. I agree that it won't get all the way
up to 1 kW / m^2. Since the proposed blimp will apparently be day VFR
only, using the higher daytime insolation should be OK. What happens
when clouds blow in or you stay out too late is left as an exercise for
the student.

Matt Roberds

Bret Cahill wrote:
Even with a pv-solar situation where you only realize 50 watts/m^2 the
blimp would still go 17 mph which allows for a lot of options not
possible with a balloon.

How do you figure on the 17 mph? Looking at the Aztec, NM profiler data
at http://www.profiler.noaa.gov/npn/pro...p?options=full , it does
appear that in the summer, the winds aloft don't often get over 15
knots, which is about 17 mph. But they also seem to regularly be around
10 knots, or about 11.5 mph, so if you're flying into the wind, you're
only making about 5.5 mph. I've piloted an aircraft where the wind was
greater than the available thrust; going backwards is about four different
kinds of no fun.

The cost might not be prohibitive. Covering half a 30 m dia sphere

That's a volume of about 14,100 m^3 or 499,000 ft^3. That's over twice
as big as the current Goodyear blimps. Do we know how to build blimps
that big?

with 1400 m^2 of $300/m^2 pv would cost half a million dollars, but
would displace 14 tons of air. A lot of recreation related industries
can spend that.

I guess the blimp itself is free and so is getting it certificated to
fly.

The only other alternative for silent flight is to have something like
a hybrid electric vehicle drive train with a good sized battery.

Maybe. I haven't run any numbers, but you might be able to make this
work if you charged the battery on the ground before takeoff (plug-in
hybrid). Batteries are really heavy, though. In a nearby thread, I
figured that to get the same mechanical work out of 1 kg of gasoline,
you'd need 20 to 27 kg of Li-ion batteries.

Matt Roberds

I found those same numbers at http://en.wikipedia.org/wiki/Solar_power ,
which cites http://www.nrel.gov/gis/solar.html . But that apparently
also includes night and cloudy days, so what's actually coming in on a
sunny day will be more than that.

In May and June in Arizona before the monsoon season when r. h. is 8%,
you are guaranteed 800 + watts/m^2 during the day.

You _will_ be going 25 mph with conventional PV.

I agree that it won't get all the way
up to 1 kW / m^2. Since the proposed blimp will apparently be day VFR
only, using the higher daytime insolation should be OK. What happens
when clouds blow in or you stay out too late is left as an exercise for
the student.

Even on a cloudy day the speed wouldn't drop off all that much because
of the propeller rule in propulsion, power ~ u^3. If the power drops
off by a factor of 8, the speed only falls by 50%.

But "just in case" have some good old fashioned fuel engine backup.


Bret Cahill

"Bret Cahill" wrote in message
ups.com...
I found those same numbers at http://en.wikipedia.org/wiki/Solar_power ,
which cites http://www.nrel.gov/gis/solar.html . But that apparently
also includes night and cloudy days, so what's actually coming in on a
sunny day will be more than that.

In May and June in Arizona before the monsoon season when r. h. is 8%,
you are guaranteed 800 + watts/m^2 during the day.

You _will_ be going 25 mph with conventional PV.

I agree that it won't get all the way
up to 1 kW / m^2. Since the proposed blimp will apparently be day VFR
only, using the higher daytime insolation should be OK. What happens
when clouds blow in or you stay out too late is left as an exercise for
the student.

Even on a cloudy day the speed wouldn't drop off all that much because
of the propeller rule in propulsion, power ~ u^3. If the power drops
off by a factor of 8, the speed only falls by 50%.

But "just in case" have some good old fashioned fuel engine backup.

Remember, we're talking about a lighter than air (or at least neutral
buoyancy) craft here. You can't afford to have the "belt and suspenders"
approach of redundant propulsion systems. You do want to carry a payload,
right?



Bret Cahill

Even with a pv-solar situation where you only realize 50 watts/m^2 the
blimp would still go 17 mph which allows for a lot of options not

How do you figure on the 17 mph?

Drag calculators.

Power = drag X velocity.

Looking at the Aztec, NM profiler data
at http://www.profiler.noaa.gov/npn/pro...p?options=full , it does
appear that in the summer, the winds aloft don't often get over 15
knots, which is about 17 mph. But they also seem to regularly be around
10 knots, or about 11.5 mph, so if you're flying into the wind, you're
only making about 5.5 mph. I've piloted an aircraft where the wind was
greater than the available thrust; going backwards is about four different
kinds of no fun.

It was better than being in a balloon, wasn't it?

Most mornings at this time of year I look out at the mountains and a
balloon is going over them. Apparently the balloonists have figured
out the morning wind.

The cost might not be prohibitive. Covering half a 30 m dia sphere

That's a volume of about 14,100 m^3 or 499,000 ft^3. That's over twice
as big as the current Goodyear blimps. Do we know how to build blimps
that big?

Make it any size that will hold one or more people.

with 1400 m^2 of $300/m^2 pv would cost half a million dollars, but
would displace 14 tons of air. A lot of recreation related industries
can spend that.

I guess the blimp itself is free and so is getting it certificated to
fly.

There is a new ultra thin [light weight] copper alloy PV that
supposedly will cost only $1/watt and has a somewhat higher efficiency
than conventional Si PV. Some even believe it will be cheap enough to
shut down the grid, even in the Pacific NW. The Google guys -- we
really need to stop calling them the "Google guys" and get their names
-- are building a big plant in downtown S.F. to produce dozens of
megawatts/year.

Then the real cost will be in the envelope, gondola, He, hanger,
insurance, parachutes, etc., not the PV.

The only other alternative for silent flight is to have something like
a hybrid electric vehicle drive train with a good sized battery.

Maybe. I haven't run any numbers, but you might be able to make this
work if you charged the battery on the ground before takeoff (plug-in
hybrid). Batteries are really heavy, though.

Hybrids just don't go very far on battery only power. A Tesla will go
240 miles but it doesn't have the drag of a blimp.

In a nearby thread, I
figured that to get the same mechanical work out of 1 kg of gasoline,
you'd need 20 to 27 kg of Li-ion batteries.

A blimp is just _begging_ to be solar powered.


Bret Cahill

I found those same numbers at http://en.wikipedia.org/wiki/Solar_power ,
which cites http://www.nrel.gov/gis/solar.html . But that apparently
also includes night and cloudy days, so what's actually coming in on a
sunny day will be more than that.

In May and June in Arizona before the monsoon season when r. h. is 8%,
you are guaranteed 800 + watts/m^2 during the day.

You _will_ be going 25 mph with conventional PV.

I agree that it won't get all the way
up to 1 kW / m^2. Since the proposed blimp will apparently be day VFR
only, using the higher daytime insolation should be OK. What happens
when clouds blow in or you stay out too late is left as an exercise for
the student.

Even on a cloudy day the speed wouldn't drop off all that much because
of the propeller rule in propulsion, power ~ u^3. If the power drops
off by a factor of 8, the speed only falls by 50%.

But "just in case" have some good old fashioned fuel engine backup.

Remember, we're talking about a lighter than air (or at least neutral
buoyancy) craft here. You can't afford to have the "belt and suspenders"
approach of redundant propulsion systems. You do want to carry a payload,
right?

Depends on the situation. If it's just a small owner - operator - one
person craft then the extra weight and cost of aux power might not be
justified or even possible. Moreover it's not such a big deal if a
weekend hobbiest listens to the the wrong weatherman and crashes his
home made into the wash during a microburst. He'll probably just cell
phone for help to recover the PV and motor.

A commercial tour operation is different. The goal is to get a lot of
people onboard a large airship for as many days as possible. Crashing
into the Colorado River is not acceptable and the heavy lift of large
displacement allows for fuel power backup.


Bret Cahill

On 14 Jan 2007 19:39:23 -0800, "Bret Cahill"
wrote in .com:

There is a new ultra thin [light weight] copper alloy PV that
supposedly will cost only $1/watt and has a somewhat higher efficiency
than conventional Si PV. Some even believe it will be cheap enough to
shut down the grid, even in the Pacific NW. The Google guys -- we
really need to stop calling them the "Google guys" and get their names
-- are building a big plant in downtown S.F. to produce dozens of
megawatts/year.


http://www.nanosolar.com/history.htm
May 2002: Nanosolar is founded by Martin Roscheisen and Brian
Sager to make solar electricity much more cost-efficient through
much better technology. The approach taken is to develop
medium-efficient but ten times less costly solar cells -- and do
so with a Silicon Valley style team of the best and brightest
engineers. The company is incorporated in Palo Alto, California,
and receives initial financing from the founders. Initial
laboratory work commences focused on technology to produce much
thinner (100x) solar cells with much simpler (printing) processes.



http://www.informationweek.com/indus...leID=193303376
The project [the solar electrification of the entire Google
corporate campus] will involve 9,212 solar panels provided by
Sharp Electronics. A majority will be placed on the rooftops of
some of the buildings in the "Googleplex" and parking lots. The
solar energy will be used to power several of Google's Mountain
View office facilities.

Google has a strong interest in solar. A startup originally funded
by Google in June announced a $100 million financing package and
set plans to build what the company claims as the world's largest
solar-cell manufacturing facility in California.

Presently in pilot production in its Palo Alto, Calif.-based
facility, the solar-cell startup — Nanosolar — has started
ordering volume production equipment for use in a factory said to
have a total annual cell output of 430-megawatts (MW) once fully
built out, or approximately 200 million cells per year.



http://www.nanosolar.com/
Nanosolar has developed proprietary technology that makes it
possible to simply roll-print solar cells that require only
1/100th as thick an absorber as a silicon-wafer cell (yet deliver
similar performance and durability). Watch the CNN video.

A blimp has one advantage over other applications of PV on cloudy days:
The option of dumping some ballast and floating above the clouds.

Balloons can change level as well but it doesn't increase their thrust.


Bret Cahill