Re: Solar powered lasers in space

On Sep 11, 10:50 pm, Alan Anderson <arand...@xxxxxxxxxxxxx> wrote:
Are you really William Mook with a new address that isn't yet in my
killfile, or are you merely an impostor trying to set off a flamefest?





Willie.Moo...@xxxxxxxxx wrote:
In 1996 I wrote in these newsgroups about an idea I had worked out
about using thin film reflectors inflated on orbit to concentrate
sunlight onto a solar pumped laser. That laser beam would be beamed
to receivers on the ground which would convert the power to
electricity and thermal energy for industrial use. Overall efficiency
would be 40%

I was roundly attacked by all - and so, it was with great interest
that I read the following on yahoo news service in 2007;

http://green.yahoo.com/index.php?q=node/1521

I am fully justified in my earlier statements - and all those who
mercilessly attacked me have been proved dead wrong in their negative
assessments of my ideas.

The earlier "attacks" were not casting aspersions on the technical
feasibility of space-based laser power beams.

Yes they were.

They were bringing up
legitimate concerns about the ability to send beams of high power
density through the air without risking damage to anything passing
through the beam.

(By the way, Hank Green's blog isn't a "news service".)- Hide quoted text -

- Show quoted text -

You've mischaracterized the active control system to make what I've
proposed seem outlandish and to force a negative conclusion.

4-wave mixing systems that use active holographic techniques to
control a powerful laser have allowed lasers to penetrate sputtering
vapor and maintain focus on a target by avoiding the sputtered
particles. The same techniques have been used to track targets.
These systems are easily adapted to controlling beams from space and
having the beams avoid unwanted targets while at the same time
illuminating desireable targets.

Furthermore, you are not clear about what constitutes a powerful beam
and what constitutes a dangerous beam. These can be distinctly
different.

Proponents of microwave systems have promoted microwave beams that
1/10th to 1/100th as powerful as sunlight. The great advantage is
that these sytems can operate 24/7 and deliver electricity as
efficiently as solar panels without the need for storing energy.

So, a powerful beam is something that's more powerful than 1/10th
solar intensity. Also, the color of the beam is an important factor.
Invisible beams can pose far less risk at a given intentisity than
visible beams for example

So, details count. The right details make a safe reliable system.
The wrong ones are easily shown to be infeasible, dangerous or
expensive. Willfully choosing the wrong details and from that arguing
that the whole idea is ludicrous - is a maddening and dispiriting
exercise - and leaves any advance open to others who are not so narrow
minded and mean.

For the record, I have proposed large central solar collector arrays
in sunny regions of low cost silicon solar panels.

A laser operating at 1 micron would be nearly perfectly converted to
electricity - since the bandgap wavelength is 1.1 micron for silicon.
1 micron is also in one of the low dispersion atmospheric 'windows'
that permit the energy to travel largely unaffected. 1 micron is
invisible.

Sunlight falls on the Earth at about 1,000 watts per sq m. Silicon is
about 18% efficient at converting sunlight to electricity. So, 180
watts per sq m ELECTRICAL is produced.

Laser light at 1 micron can fall on the Earth at any power density we
design. Looking at the solar spectra,we can see that the sun emits
about 380 watts per sq meter in the infrared portion of the spectrum.
Shining an infrared laser at this intensity causes no harm in to the
environment, since its what the environment has adapted to.

But 1 micron laser energizes silicon with about 85% efficiency after
passing through the air. so,that 380 watts IR becomes 323 watts per
sq m ELECTRICAL. Since the satellite operates 24/7 - the ground
system does too, with the exception of the occasional weather
interruption and that's minimized if the proper site is chosen.

The advantage of the satellite is easily seen.

Lets say we build a 8 million acre (32.4 billion sq m) solar collector
array 5 miles wide and 2,500 miles long along our Southern border, in
the high Sonoran desert there. This is exposed to about 1,600 hours
of sunlight per year. At 180 Watts per m2 this array produces 9.332
trillion kWh per year. Used to desalinate seawater drawn from the
oceans near the border and decompose it into hydrogen and oxygen, this
solar panel array from sunlight alone would produce 186.6 million tons
of hydrogen gas each year. This has a heat value of 1.2 billion tons
of coal. So, by piping hydrogen gas made in this way to coal fired
power plants, those plants can immediately be converted to hydrogen
gas eliminating pollution from this source. In fact,using 123 million
tons of hydrogen to displace 800 million tons of coal and then using
62.6 million tons of hydrogen to hydrogenate the stranded coal,
produces 5.6 billion barrels of liquid fuels each year (gasoline,
diesel fuel, jet fuel) - largely severing our reliance on foreign
sources of oil. In fact this amount of oil plus the oil produced in
the US, provides for ALL US needs for liquid fuels - while reducing
our carbon emissions by half.

But lets add solar powersats to the picture - as described.

We add light-weight inflatable powersats to the picture that beam
energy reliably and safely to the 8 million acre ground site. Another
323 Watts per sq meter electrical is produced by the same solar panel
array - IN ADDITION to the solar influx - and this is available 24/7
with only slight interruptions due to weather in some spots on rare
occasion. So, this 323 watts is available 8766 hours a year - so each
square meter has added to the 288 kWh/year, 2.83 MWh/year - a 10 fold
increase!!! Which is well worth the cost of the satellites, if
they're made and launched cheaply enough.

With no increase in the 32.4 billion sq m array footprint (merely
designing the entire system to operate at 3x nominal solar output)
total energy output is 101 trillion kWh per year. This is enough to
create 2.02 billion metric tons of hydrogen gas.

Now, a ton of hydrogen has the same energy value when burned as;

4.5 tons anthracite
6.0 tons bituminous
10.2 tons lignite
23.4 barrels crude
1,190.0 gallons gasoline

Humanity currently uses 30 billion barrels of crude oil each year. So
converting the heat value of this hydrogen to barrels of oil
equivalent - obtains 47.2 billion barrels equivalent.

This means that the US following this sort of program would not only
become energy independent with completion of the ground station
portion of this program, but would rise to dominate the world's energy
markets with completion of the space portion of this program - at
first by hydrogenating low rank carbon sources, and later, by selling
liquid hydrogen throughout the world.

Later still, advances in laser control could lead to direct beaming of
energy from space to users on the ground, stationary users at first,
and later mobile users. Finally, lasers could power large spacecraft
and space propulsion systems, as well as space based factories.

I proposed this more than a decade ago - and have been ignored or
ridiculed while at the same time others have developed elements of
what I proposed without seeing the larger potential. Too bad we
haven't jumped onto this more agressively. A (Japanese) sociologist
told me once at a conference that a culture in decline, will avoid any
possibility for growth - he felt the US, and Europe generally were in
decline, whilst Asia was rising. It need not be that way I replied.
But I'm not a sociologist.


.

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