Wednesday, November 14, 2007

Should Solar Powered Satellites Be Built Over Land Or Over Water? Authentic NASA Toys and Replicas
When one looks at the heavens above us, at its utter vastness, you can not help but be humbled by its glorious potential. Whether its exploiting asteroids or water ice, one can only imagine the untapped resources just waiting at humanities finger tips.

One resource that seems to be on every ones mind is energy. With the cost of fuel accelerating faster than the rate of inflation, individuals, companies and governments are turning to fresh alternatives to power our rowdy planet.

Recently the US government has taken a fresh look at the possibility of constructing solar powered satellites (or SPS), which would be able to collect energy from the sun and beam it down back to Earth. If doable, these power stations would be able to deliver unlimited energy in a clean, efficient manner (provided the sun does not explode of course).

While launching and building one of these satellites in space may have its own engineering and problems above, constructing the receiving rectenna on land may provide even more nightmares below. In order to avoid these concerns, scientists may want to consider building a solar satellite rectenna over the ocean instead of on top of land.

In order to receive energy from our celestial star, solar powered satellites have to be able to safely convert the energy they collect from the sun and transmit it into microwave radiation. But in order for the entire system to be profitable, the rectennas have to be huge, (about 14 kilometers) in order to be competitive against the fossil fuels that we heavily depend upon.

In order to avoid ugly fights over property rights, some have suggested that these rectennas be built over remote farmlands, with the intention of avoiding major population centers. While this idea may sound wise, farmers will probably not be thrilled with some government object hindering their view of the sky, and express their disappointment by filling the bottom of the structure with holes.

By constructing it over the ocean scientists would be able to avoid worrying about their pet project being attacked by rural neighbors, terrorists or kids pulling a cool Halloween prank. A remote location on the sea would make it harder for outsiders to tamper with the rectenna, which would lower the cost of insurance for the SPS.

Another reason why choosing water over dirt may be more logical can be summed up in one word--lawyers. In order for the government to actually build a rectenna over sovereign soil, they are going to need an army of lawyers, backed up by a literal army enforcing the law.

Despite the fact that the American government (like all governments) has the right to take away property from their own citizens, it does not mean that separating these citizens from their lands will be easy.

In order to avoid everlasting lawsuits, as well as rioting citizens, the government may want to choose building a rectenna on top of the ocean, as constructing in international waters may be easier than on national soil.

Last but not least, if the government (or any company with their blessing) is able to avoid the two former pitfalls, then they may find themselves suffering from the wrath of nature itself. Hail, tornado's and violent thunder storms can easily damage an enormous rectenna at "the best" and partially reduce it into expensive rubble at the worst.

By comparison constructing a rectenna over a calm ocean (i.e. the Pacific) may avoid most of the weather fallout that asualts us land dwellers.

Even though solar powered satellites may be unable to satisfy the growing hunger of developed nations, they may be able to inspire our world population to go solar themselves. Combined with our friends in space, SPS's and quality solar power on Earth could enable our species to live on this planet independent of the black gold that plagues our "tiny" world.

Note: Due to lack of time, images will be added later.

Update: Images (with credit) added to the post.

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  1. How do you get the power to where you need it?

    The ocean is thin on people who consume power, and rather short on power transmission lines . . .

  2. Brian's Concerns are valid. Transmission of electricity requires an expensive infrastructure and doing so over long distances via wires results in considerable loss.

    Additionally water vapor absorbs microwaves. Oceans at subtropical to tropical latitudes tend to be humid places. (

    Oceanic platforms are expensive. You are talking about Texas towers 14 clicks across.

    The ocean is corrosive, and exceedingly non-friendly to electronics. It is also violent. The oil rigs in the Gulf of Mexico are quite well built and intended to withstand the many hurricanes that pelt the area, yet Katrina sank several and knocked others so far into the bayou that the Coast Guard is still finding them.

    Pacific is just a name.

    A Typhoon would ruin your whole day...and the days of many many people who would lose power.

    There are vast areas of farmland in this country to the extent that there is little or no need to place one of these over peoples houses. Even if that was done it would not reduce one view of the stars overhead as these are open arrays. Certain angles would be affected.

    Your characterization of rural people is insulting. It is also pointless as they don't make a shotgun big enough to damage these big metal poles. :)

    Additionally, there is a huge amount of land in the US, including stretches of desert (where the low humidity would greatly reduce microwave adsorption) that is tied up in national parks. This could be leased or sold outright to the power companies that are doing this. The environmental impact should be minimal.

    One problem with SSPS arrays is the fact that the transmission rates are orders of magnitude greater than the allowed safe doses of microwaves.
    Luddite hysterics are freaking out about POWER LINES.
    This is going to be a tougher sell.

    It is not likely to be greatly diminished by putting the arrays over water. The same people will lobby and sue hard to put the kabosh on this for the sake of the fish, just as they have nuclear power plants. Given the strains the ocean ecosystems are under, this is actually a defensible position.

    Also, there will be some leakage due to atmospheric dispersion (this will be greatly increased in a marine environment). The frequencies that work best for this are used now by Wi-Fi. No Wi-Fi with SSPS. Cellphones are likely to be affected too.

    If this is doable we likely missed the window of opportunity in the late '70s.

    I hope I'm wrong and this is doable. If we get launch costs down the obsticals are likely to be political and not technical. Unless we try doing it at sea.

  3. @ Brian: Great point to consider.

    I wonder if building the power cables under the watery soils solve that?

    @ Ken: I guess building it over oceans is kinda moot now, if the vapors will absorb the energy. I guess deserts are looking fairly tempting right now.

    As far as rural farmers go, I didn't mean to be insulting, although I do wonder if someone (whether they be from the city or elsewhere) wouldn't attempt to put holes in one of those rectinas. ;-)

  4. A couple things - Agree with ken about the irradiation concerns. Scientifically speaking, you can polarize the things in such a way that they won't heat up water molecules (I think it's circular polarization which is ok, and linear which makes popcorn, but not sure). However, at the power levels and exposure times we're looking at, there will almost certainly be chronic-exposure type health and environmental effects. And if not, there will be a random cluster of cancer deaths near one of them some day and someone will freak out and sue.

    There are certainly some places that it would work though - certainly in the Southwest US, you could do this. Probably in the Northwest there's enough BLM land too. One thing of note is that the wavelengths of these microwaves are quite macroscopic - so you can put a pretty coarse mesh, like chicken wire, and catch them. Theoretically at least, you can then plant crops or graze cattle underneath - in fact, "underneath" will probably be the safest place for miles around the rectennas.

    And finally, you note that eminent domain might be difficult - but you don't mention that it would also be unethical to evict farmers from their property so that city dwellers can watch TV.

  5. I wonder if building the power cables under the watery soils solve that?

    Man, I don't know. I know that building submarine cables for telecom is very difficult and fraught with peril. The distances we're talking about would seem to make it impractical at best.

    A Typhoon would ruin your whole day...and the days of many many people who would lose power.

    I agree with your points - there is a reason why 'maritime' electronics are more expensive than their terrestrial counterparts. I've messed around with boats my whole life - it's amazing how fast the various bits on a boat rust, decay and simply fall apart.

    And I've been in several typhoons - luckily on land. The amount of wind and rain was impressive.

    But typhoons don't wander across the equator.

    And finally, you note that eminent domain might be difficult - but you don't mention that it would also be unethical to evict farmers from their property so that city dwellers can watch TV.

    That doesn't keep the government from doing that when they see the need. But a better solution would be to buy the farmer out.

    Yes, ancestral lands and all that. All I can tell you is that I lived next door to a cotton farmer for a few years. He lived there his entire life - and happily sold out when the price was right. His farm is now a subdivision near Dallas.

    Most of his windfall went into the bank. Some of it bought a bigger farm further out.


You can either visit the stars or watch them from afar.

But if you choose the former, you'll definitely get a better view.

~Darnell Clayton, 2007

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