[MarkR]

Won't those massive solar panels cast a shadow on the earth.

I'd be well narced if they installed one of those sats above my house

[JohnDenver]

$this->bbcode_second_pass_quote('Anonymous', 'T')his proposal is so full of holes it seems to me a distraction from addressing the issue of sustainable energy supply.

[Concerned]

$this->bbcode_second_pass_quote('', '
')America doesn't need to pay for it. It can likely be financed by a consortium of private investors. Or by the Chinese, or the Japanese. You seem to think energy is "optional" for the future. It's not. The Chinese are not going to regress to the Ching Dynasty just to satisfy greens like yourself. If satellite solar power is economically viable, they will implement it. Doing without energy is not an option for them. In fact, it's not an option for any of us.

[small_steps]

$this->bbcode_second_pass_quote('Ted', 'B')eaming power through space via microwave or laser is clearly more efficient than passing it through the atmosphere, and much more efficient than using power lines.

[Ted]

100% beats 90%, no?

Also, wiring takes a relatively huge amount of effort to produce, install, and maintain.

No contest here, really.

[Ted]

Earth's deserts receive petawatts of solar energy. Humanity's demand for oil power is a few terawatts. Terrestrial solar from deserts can thus completely replace oil as a power source, assuming we can build cheap enough solar collectors.

Here's a link to another thread page containing a desert solar calculation:
http://peakoil.com/fortopic1698-0-asc-15.html

[backstop]

Ted - if you want to live in a desert that's your choice, but most people don't. This is very fortunate because the energy costs of delivering water, food, raw materials, air conditioning, etc, to even a single city of a million people would be massive.

Conversely, if people don't choose to move, then bringing energy from deserts to the world's population centres would involve such losses in transmission as to make the option pretty meaningless.

Personally I've no interest in seeking ways to maintain 3% growth since, with the planet's limits to growth, the goal is not achievable and the longer the present system lasts, the greater will be the crash and the damage to future generations resources.

regards,

Backstop

[Ted]

A big parabolic reflector could be used to focus light on another device that would convert the intense radiation into some usable form of power. One option would be a device that beamed microwaves to earth. Another would be a light-pumped laser of some kind that transmitted power over interplanetary distances, for use by spacecraft or remote stations in the solar system.

The reflector would comprise two spiral ribs in parallel, between which a reflecting membrane is stretched, at an angle which varies with the radius so as to function as a parabolic mirror, and which is determined at each point by the distance between the ribs. If the spiral begins far enough from the reflector axis so that the distance across the reflector ribbon between adjacent coils is small enough, compared to the radial distance, that the ribbon could rotate fully 90 degrees from an axial alignment to a radial one, then the membrane could be stored on spools. Now the trick would be to uncoil the spool or spools from storage into the functional reflector. When expanded, the ribs of adjacent coils would tend to move together and would have to be held apart (especially near the edges of the relector where the angle is greatest) by some structure that is under compression. Moreover, the tension along the ribbon would have to be balanced by stays piercing the reflector. (This piercing could be avoided by using not two, but three spiral ribs.)

The spiral design would facilitate a one-dimensional assembly procedure that could be executed by a single robot. A variation of this design would employ a number of separate ribbons simultaneously payed out (or perhaps secreted as a fast-hardening liquid) by the same number of robots, starting in a circle around the center and moving
outward.

[small_steps]

$this->bbcode_second_pass_quote('Ted', '1')00% beats 90%, no?

Also, wiring takes a relatively huge amount of effort to produce, install, and maintain.

No contest here, really.

[Ted]

Whups, strike ", and which is determined at each point by the distance between the ribs". The details of how to hang the membrane are secondary, there are clearly a number of different options. The idea is to hang the reflecting membrane on an Archimedean or arithmetic spiral so that it can be constructed by simply repeating a few operations.

[Ted]

The best option for long-distance transmission seems to me to be light and microwave through vacuum. Microwaves through the atmosphere to and from a network of satellites, which would perhaps transmit power among themselves via laser.

An alternative might be microwaves in low-pressure travelling wave tubes instead of high-voltage transmission wires. I haven't checked the losses inherent in this idea, but I bet it beats wires and would be comparable to laser in vacuum.

[Ted]

You have me on my 100% claim. Where's your 90% figure from? Does it really apply to transmission over global distances?

Bet I can still show that transmission of power as electromagnetic waves through vacuum and / or air is more efficient than transmission through copper wire.

[smiley]

Beaming microwaves through the atmospere is not 100% efficient. The beam will be absorbed by humidity, dust particles etc.

http://www.qsl.net/n9zia/wireless/oxy-water-atten.html

[MarkR]

I just wonder how efficient the microwave generators are.

I understand that small microwave rectennas are up to 80%-85% efficient, but they produce DC power. If you wanted to get grid power out, you'd need a suitable inverter, which lowers efficiency still further.

[small_steps]

$this->bbcode_second_pass_quote('Ted', 'Y')ou have me on my 100% claim. Where's your 90% figure from? Does it really apply to transmission over global distances?

[Ted]

MarkR and Small-Steps -

The key thing, I think, is direct conversion between electromagnetic waves and alternating current. Transformers, not rectifiers...

[small_steps]

$this->bbcode_second_pass_quote('Ted', 'M')arkR and Small-Steps -

The key thing, I think, is direct conversion between electromagnetic waves and alternating current. Transformers, not rectifiers...

[challenge]

In the abstract of his book "The oil age is over" (2004) of Matt Savinar, the author states that the technique of Beaming energy to the earth "is plagued by "major technical, regulatory and conceptual hurdles" and won't see the light of day for several decades".

In the literature reference on this subject, the sole reason stated by NASA is a financial hurdle. While in the cited article it is stated that some major problems have been solved in recent years. My Question: What questions are remaining?

In the mean time there are several initiatives, ( www.gezen.nl ) helas only in Dutch so far (a translation can be made, if wished) but it is the idea of CSP's spreaded over the world together with wind energy and bio centrals etc. Explained in the plan on the site is coverage of a great part of northern
Africa en southern Europe with CSP's (Concentrating Solar Power) centrals. CSP is allready used in a 150 MW CSP in Kramer Junction in California. Instead of using photovoltaic cells in space and converting it to microwaves that are beamed back to the Earth through a process called "wireless power transmission, mirroring techniques can be used. The cost of using mirrors is about 10% of the cost using photovoltaic cells and if used, the ground station(s) can be stationed on cloud free spaces on earth (30 degree North and 30 degree South of the equator).
As an alternative a CSP can be used in space in stead of photovoltaic cellssendin their converted (but harmless) microwaves back to earth.
In the meantime the Sovjets already experimented with a the same, but a smaller kind of system, mirroring sunlight to Siberia during the dark months of the year. Helas didn't their umbrella mirror expand as was expected, but allready in the eighties the Sovjet's have been in space for these applications,

I think an airborn CSP can be more cost efficient and can work 24 hours a day in stead of CSP's all over the deserts.

Martien Pieters, the Netherlands

[JohnDenver]

Hi Martien, welcome to the group.

Nice post! Here's a link on similar ideas in English:
Link

I find the idea of space mirrors particularly intriguing. They are an old and simple technology with no complex parts, and yet they have the potential of gathering huge amounts of free clean energy. They can also be used to attenuate global warming (two birds with one stone!), and allow humans to control the temperature of the earth.

[jato]

$this->bbcode_second_pass_quote('', '"')Space Solar Power (SSP) is certainly a technological challenge," Hoffert said. "But much less of one than, say, building a fusion power reactor."

Both methods have the potential to provide baseload electricity for Earth for millennia to come, he said. But unlike fusion, space-based power generation doesn't require scientific breakthroughs before it can be employed.

"We advocate an SSP demonstration in the next 10 years to explore the technology and potential for cost reductions aimed at power for developing nations."