Solar Power from Space

<groan> Beaming energy again.
Whatever happened to the KISS principal?
"The beams could be directed to specific areas or regions that ... need obliterating power.
Cmon guys, we can't even distribute water across a small country... Lets try to master the simple stuff first.
Del

OK, so why not beam it from desert areas at ground level instead?

Increasing the collector area (by installing large collectors in space) without increasing the area of the waste heat radiator (the surface area of the earth) can only lead to one thing: higher surface temperatures!

Back in the seventies, NASA investigated converting sunlight to microwaves in space and beaming the microwaves to a "rectenna" on earth which would produce low voltage DC. One needs a large array of PV cells to collect the sunlight and make low voltage DC. One needs a large array of transmitter elements to focus a relativeely narrow beam of microwaves on the rectenna. One approach would be to drive each transmitting antenna element with an efficient magnetron vacuum tube, which could be cooled with a pyrolytic carbon radiator about the size of a 45 rpm phonograph record. Overall DC to microwave conversion efficiency could be better than 90 per cent. Management said that vacuum tubes were unacceptable, too old fashioned. The transmitter must be solid state, transistors. Given that transistors are less efficient and must run cool (say 100C), the PV array area would be five or six times larger,and the waste heat radiator would be larger than the solar array. The conductors (copper?) for DC and heat would be about as massive, or more, as the rest of the system, so the mass needed to be launched into space would be ten or twenty times as much as the magnetron system. Oh, they hadn't thought of that. Cancel the program. It wasn't the first time NASA had been burnt by discarding old-fashioned technology. They had a tube type communications transmitter on the space shuttle, 16 Watts as I recall, which they replaced with a transistor transmitter. True, the transistor was smaller and lighter than the tube, but the heat sink was humongous (tens of kilograms), and the shuttle's environmental control system couldn't the additional waste heat.

While this technology may not provide energy cost efficiently, once it is in operation, it will decisively put an end to any debate over the existence of anthropogenic global warming.

Who is going to pay more for electricity? Will you? How about those on fixed incomes?

Yes, we have the technology to one day put up a large enough structure to power a large city. What about the thousands of other large cities?

I doubt that this technology could put much of a dent in our world-wide power consumption and if it we did power a city or two via this means it would hardly provide decisive evidence for or against global warming.

You need to go scratch your chin a little longer. It will come to you when you have thought it over.

(By the way, I am not advocating this technology. Also, the relative efficiency and affordability are not necessarily the main factors dictating how power is produced. You are a bright fellow, you should realize that the energy market is a long way from a free market. I'm sure you can think of several examples where funds have been allocated to less than optimal power projects, often with government help.)

This is more than just a simple solar farm in the desert.

Incidentally, telling someone, "It will come to you," is not a rebuttal to an argument. State your point clearly so that everyone understands what you mean.

I think that money drives most of the decisions on energy production. While the taxpayer may subsidize some of the burden, ultimately we are all paying for these investments (either by tax or directly).

Given the current state of economics world-wide you would be hard pressed to see the substantial funding required to pull off such a project, much less the vehicles needed to get the payload to geosynchronous orbit.

'It will come to you' wasn't intended as a rebuttal. I wasn't engaged in an argument. It was a suggestion that you might reconsider.

So, I'll spell it out:

You and I are in agreement that this project is unlikely to be economically advantageous...whoever foots the bill.

You and I disagree somewhat on what drives decisions for alternative power projects. I can think of several cases of solar and wind where huge sums have been invested in projects that are not economically advantageous. Your glasses are definitely more rosy in this area.

As far as settling the debate over man's contribution to global warming....using satellites to collect solar energy and send it to earth will definitely be adding heat. My assumption here is that the satellites will not be in between the earth and sun creating large shadows.

Not too tough. Certainly not worth several paragraphs...which is why the original comment was much shorter.

Ah! Now I understand your point.

I guess it depends on the type of energy beamed to Earth and the net efficiency of the conversion on the ground.

It seems obvious that the satellites are not simply beaming sunlight back to Earth, but converting it to microwave or laser.

Nevertheless, the conversion on the ground can not be 100%, so there will have to be waste heat and that is an excellent observation on your part.

Quite.

This looks like a cool project, at least from theory, but what about a cost analysis? This thing has to be extremely expensive and I would doubt that the payback would be justifiable.

How will it perform when the weather is inclement? Obviously, a laser is not going to cut it through heavy cloud cover. Microwave may be another story.

I think there is often a disconnect between what is technologically feasible and what is prudent. In this case that gap may be a very wide one

First of all, what would happen if the micro-wave beam deviated off course, a loss of a lot of life, second, who is going to pay for all this, because the electricity bills will rocket to an enormous amount????

Spencer.

The BBC source mentions the frequencies of the beams would be tuned to avoid dangers like you brought up, the same tuning that will allow them to pass through clouds.

Supposedly.

But they will still carry an enormous power, so much so that it would kill a person instantly, if not then they will be useless!!!

Check out this pdf, page 3 under the header Microwave Exposure. They argue the EM exposure would still be below accepted environmental safety levels.

As has been mentioned, though, none of the articles go into much detail about the predicted costs of the SSP (space solar power) concept, which is its biggest problem.

The collector array would have to be massive, like thousands of meters square...How much did it cost, and how long did it take to get the space station built? The scope and cost would be overwhelming.....even if the technology could be made to work...