
Solar powered airships - TelmoMenezes
http://green.autoblog.com/2011/10/22/solar-ship-sails-the-skies-schlepps-supplies/
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SagelyGuru
I always thought this a great idea worth pursuing, especially if you are
'sailing' down the prevailing winds/jetstream, i.e. from North America to
Europe it is practically a free ride.

It can be a lot more problematic 'beating upwind' the other way, especially as
there is not much sunshine in northern Europe due to its considerable
latitude.

This craft may be heavier than air but it still has considerable wind
resistance.

Also, the dangerous static electricity buildup has to be considered seriously
and solved.

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dimitar
Isn't it _lighter_ than air? The article also claims its heavier, but I
assumed it was a mistake.

~~~
TelmoMenezes
Heavier. The article is about an hybrid vessel that uses helium to decrease
its weight but is still heavier than air. I'm not a physicist, but I assume
that lighter than air objects tend to have more wind resistance than heavier
than air objects.

~~~
rbanffy
> lighter than air objects tend to have more wind resistance than heavier than
> air objects.

They have a larger cross-section relative to their mass than heavier than air
vehicles. The larger the cross-section, the larger the force wind exerts on
it.

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knowtheory
The more we use helium for stupid shit like this, the less helium we'll have
in the future for MRIs and anything else that requires super-cooling.

Forget peak oil, we are, in fact, sitting at peak Helium, and selling that
shit for children's balloons and crap like this.

(And for the historical context, Congress in its infinite wisdom, during the
deregulation boom in the 90's, decided to mandate a price to dump all of the
US's Helium reserves. As a result we are selling it at way below market rate,
depleting a finite reserve of an element which we have no means of recapturing
once it's released into the atmosphere. Quite a number of scientists have
lamented this insanity, and begged the government to do _something_ even if it
is just allowing the rate at which the government sells Helium to float to
_actual_ market value, let alone get congress to reverse itself. Check it
yourself: <http://en.wikipedia.org/wiki/National_Helium_Reserve> )

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TeMPOraL
> The more we use helium for stupid shit like this, the less helium we'll have
> in the future for MRIs and anything else that requires super-cooling.

While I agree with the rest of your comment, could you explain why do you
think that airships are "stupid shit"? I'd say that the insane amount of fuel
we use for transportation is a big waste of oil and I really look forward to
see airships back in the sky, doing heavy lifting and maybe more.

~~~
knowtheory
Okay, i should dial it back a bit. What they're promising is cool. Low
infrastructure, high pay-load travel is indeed interesting.

But they too are depleting a natural resource, just as petrochemical fuel
usage does. And while we can find other storage mechanisms for portable energy
(batteries, flywheels, hydrogen, what-have-you), there literally is no
substitute for Helium cooling, by virtue of the laws of physics as we know
them.

This is not worth giving up cryogenics.

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TelmoMenezes
I always wonder why helium-based airships never took off. Are there any
technological limitations I'm not aware of? Seems to be such a simple and
powerful idea (even more now that oil prices are soaring).

~~~
astine
They did. Ever hear of the Zeppelin? They took off all the time in their hey-
day. It's a myth that they were filled with hydrogen; the Hindenburg was only
had hydrogen in it because at the time helium was not available in Germany at
the time because it was only produced in the United States and the US was
refusing to export it.

Anyway, the reason we don't see airships much anymore is because for most
things heavier than air craft are more economical. A Boeing 747 is a third the
size of a Zeppelin but much faster, more reliable, and with much more usable
space and lifting capacity. There's really no economic reason that an Airship
should be preferred.

~~~
TeMPOraL
> There's really no economic reason that an Airship should be preferred.

What about the fuel usage per unit of mass carried?

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pnathan
I dug into the website of the company and the low-end model goes about 70 MPH
in hybrid mode, and 35MPH in solar mode.

I would love to have a flying car. Fuel infrastructure could be awkward
though. :)

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pxtreme75
Once in a while we should stop and think that Sun is the major energy supplier
for the planet. Nature has found a way to turn it to plants, life, wind,
petroleum etc. I truly belive we can perform equally well.

~~~
MichaelApproved
Thats an empty tree hugger comment. The amount of energy required to grow a
plant over several weeks/months is much less than what's required to move a
truck around.

I also don't like the argument that the amount of sunlight that hits the Earth
in one hour can power the world for who cares how long. I don't like It
because it assumes its actually possible to capture all the sunlight that hits
the Earth, nevermind that we're actually already using a large part of that
energy to grow our food and warm the planet.

The Sun should play an important part in replacing fossil fuels, which I
believe we must do, but make good arguments for it, not empty ones.

~~~
hugh3
Yes and no. I don't think it's an empty tree hugger comment, but I do think we
need actual numbers in order to discuss these things.

World energy usage: 474 exajoules per year

Incident solar flux: 1000W per square metre

Let's suppose (optimistically but not unrealistically) we can get 10%
efficiency (over day and night, so more like 20% during the day).

How much land (or indeed, water) do we need to cover with solar cells? About
150,000 square km.

So, while the cost of building all these solar cells is significant, the
proportion of the Earth's surface they take up isn't.

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jerf
When people propose the "cover 150,000 km^2 with solar cells solution", I like
to see them go on the record as saying that if we actually _tried_ , they
would not immediately turn around and start screaming about the 150,000 km^2
of Mother Earth we just converted to industrial land.

Solar of any form has a major power density problem. At least, it does in the
biosphere, which it should be observed is only a rather small percentage of
the universe....

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hugh3
_I like to see them go on the record as saying that if we actually tried, they
would not immediately turn around and start screaming about the 150,000 km^2
of Mother Earth we just converted to industrial land._

Oh, don't get _me_ confused with a tree-hugger. I'm about as anti-greenie as
you can get. I'm just here to do the mathematics.

I'm for whatever source of energy is cheapest.

