Satellite-Based Laser Power Generation BS

Satellite-Based Laser Power Generation BS
From Ted Twietmeyer
1-25-10

First we had the space elevator madness, and then microwaves beamed from space to generate power.

Now it's lasers. It was just a matter of time that this had to happen sooner or later. But we shall see that everything you can imagine is wrong with this idea including safety, cost and efficiency.

I'll swear that marketing people have so much BS that when they dream at night their dreams are brown, not full color or black and white. Having dealt with too many of them in my life, I speak from experience.

Astrium is the company with mad scheme to use sunlight to power a laser in the 20KW class, and they claim it will be safe. (That was also said about depleted Uranium, Aspartame, GM food, etc)

SAFETY

Mr. Perren of Astrium which is certain this idea is safe proclaims the following:

"We are concentrating on developing something that is safe. While the laser beam will have some heat in it, we intend for it to be safe for people to walk through unaffected." [1]

"Something that is safe?" They better disconnect their phones, faxes and shut off cell phones so they can concentrate enough on this one. Let's take a closer look at their statement. Lasers excel at concentrating high energy into a very small beam. If a satellite will contain the laser, obviously the beam must be small. Standards to prevent eye damage exist for a reason.

The American National Standards Institute (ANSI) has safe power standards for all types of lasers. These standards define exposure limits to the human eye of less than 1 watt, and in some cases just thousands of a watt for laser light.

Here's a brief list of USA safety standards for lasers:

* ANSI Z136.1 - Safe Use of Lasers
* ANSI Z136.3 ­ Safe Use of Lasers in Health Care Facilities
* ANSI Z136.4 ­ Recommended Practice for Laser Safety Measurements for Hazard Evaluation
* ANSI Z136.5 ­ Safe Use of Lasers in Educational Institutions
* ANSI Z136.6 ­ Safe Use of Lasers Outdoors
* ANSI Z136.7 ­ Testing and Labeling of Laser Protective Equipment

Near infrared light has a wavelength of about 850 to 900nm. Higher numbers (such as 1400nm) represent longer wavelengths in the infrared. People cannot see this type of infrared but feel it simply as heat. I have added some comments in the following text someone else wrote using curly braces to help clarify a detailed statement on eye damage taken from [2]

"The coherence, the low divergence angle {that laser light does not spread out very much over distance}of laser light and the focusing mechanism of the eye means that laser light can be concentrated into an extremely small spot on the retina [the back of the human eye.} A transient {sudden} increase of only 10 °C can destroy retinal photoreceptors. If the laser is sufficiently powerful, permanent damage can occur within a fraction of a second, faster than the blink of an eye. Sufficiently powerful visible {and ultraviolet}to near infrared laser radiation (400-1400 nm) will penetrate the eyeball and may cause heating of the retina, whereas exposure to laser radiation with wavelengths less than 400 nm {ultraviolet} and greater than 1400 nm {far infrared or heat} are largely absorbed by the cornea and lens, leading to the development of cataracts or burn injuries.

Infrared lasers are particularly hazardous, since the body's protective "blink reflex" response is triggered only by visible light. For example, some people exposed to high power Nd:YAG laser {solid rod laser} emitting invisible 1064 nm radiation {heat} may not feel pain or notice immediate damage to their eyesight. A pop or click noise emanating from the eyeball may be the only indication that retinal damage has occurred i.e. the retina was heated to over 100 °C {boiling point of water, or 212 °F} resulting in localized explosive boiling accompanied by the immediate creation of a permanent blind spot." [2]

Note that a temperature increase of just 10 °C causes damage to the retina by destroying photoreceptors. Yet Astrium claims people will be able to look up at the beam without eye damage? Perhaps they have found a way to change the laws of physics!

Let's look back at another Astrium statement ­ "While the laser beam will have some heat in it, we intend for it to be safe for people to walk through unaffected." Ridiculous.

It is well known that lasers with power levels less than 1 WATT can cause serious eye damage.

"The U.S. Food and Drug Administration (FDA) requires all class IIIb and class IV lasers offered in commerce in the US to have five standard safety features: a key switch, a safety interlock dongle, a power indicator, an aperture shutter, and an emission delay (normally two to three seconds).[2]

"Even a laser pointer which operates at about .005 watts or 5 milliwatts, can easily damage the eye. Yet parents think nothing of giving one to their children.

Note that lasers in class IIIb and class IV are only a few milliwatts ­ not 20,000 watts. With a satellite in orbit, there would be no way for someone on the Earth to turn a key switch, trip a safety interlock or hit a big red STOP button.

For more on laser safety see Princeton University's training information. [3]

COST
Astrium's laser power satellite will cost perhaps 300 million dollars to build, and many millions more to insert it into orbit. All satellites expend fuel to reach their assigned locations, and in some cases for station keeping operation. Station keeping prevents satellites from plunging back to Earth, colliding with other satellites, losing orientation and communication with Earth and drifting out of position. Also required are a team of people who monitor and control the satellite around the clock, 365 days/year. Satellites only have about a 5 to 8 year lifetime in orbit before solar cells have been degraded by full solar UV radiation and heat to the point of no longer being efficient enough to be useful. In other words, satellites slowly become 10 ton pieces of space junk. They are either de-orbited with ground commands, or sent into the Sun for destruction. Left in space a dead satellite becomes a serious hazard.

Does all this seem worth the expense to generate a measly 20KW of power? If the cost to design, build and launch the satellite into orbit is about $350 million, a simple calculation reveals that this "free" energy from the Sun actually will cost about $17,500/ WATT - and that figure doesn't even include the cost of the ground crew and ground station to monitor and control it ­ or the tens of millions of additional dollars to build the laser power collection system on the ground. This is what would collect the laser energy and convert it to regulated alternating current.

Even the most expensive system you could ever imagine to generate electricity from ocean waves, is a tiny fraction of this cost. Even if a sea wave power generating system was made out of the finest stainless steel money can buy, it still wouldn't even come close to the laser power system cost.

20KW is only enough power to supply the conservative electrical needs of just FOUR HOMES. Laser light cannot power thousands of homes, nor can the same light be used effectively at more than one location. Laser light is very different than microwaves from television satellites. These satellites distribute microwaves at a power level of about 36 watts per transponder over an entire continent to provide television and telephone service.

EFFICIENCY

Lasers are incredibly inefficient, with the best efficiencies on the order of about 10 to 15%. This means to generate 20KW of power, the satellite's solar panels will need to generate about 200KW of power just to compensate for laser losses. Of course, this doesn't include additional power required to operate the satellite's station keeping, computers and communication systems.

To put this into perspective, the 4 pairs of solar panels on the Space Station generate only 32 KW of power. The Astrium satellite will require a solar array at least SEVEN TIMES larger than the space station has. It's hard to conceive that such a huge solar array could be carried into space with just one launch.

And we haven't yet considered how much of the 20KW of laser light will actually reach Astrium's Earth power station. Although infrared can pass through clouds there is still a loss factor for varying weather conditions that must be accounted for when engineers calculate power budgets and losses.

With all these facts exposed, does it seem that Astrium's power satellite makes sense or will be safe? Lasers are a wonderful solution for a plethora of different technologies and problems - but are not practical for beaming power back from space.

Perhaps the entire scheme is just another stock-market scheme to raise big bucks and make a few people rich. This wouldn't be the first time.

I think there's a whiff of a dead space elevator in the air

Ted Twietmeyer

[1] - http://www.telegraph.co.uk/earth/energy/solarpower/7060015/
Lasers-to-beam-energy-to-Earth-from-space.html
[2] - http://en.wikipedia.org/wiki/Laser_safety
[3] - http://web.princeton.edu/sites/ehs/laserguide/sec3.htm#class3