Space-based power

[pfrit]

If I was designing this, I would use mylar (Really light) and reflect the light to my high efficiency solar cells.

That gets you the problem of heat dissipation. Always a problem in space for concentrated sources.

Solvable. The reflectors are going to make a lot of shade for radiative coolers. And they do not need to weigh all that much. Maybe not a pretty solution or an easy one, but should be lighter.

[gblaze42]

One other issue with solar cells is the limited lifetime of the cell, they tend to degrade over time, in the radiation and heat of space, I would think it would degrade quickly. So all these SPS units would need to be replaced at some point.

Is it doable, you bet. Something like this would need a space launch infrastructure that was cost sensitive and reliable and reusable. The technology exists, if just on paper, whats needed is a purpose to build it, before this we had one shot deals, majority are scientific payloads, which have different launch characteristics.

A SPS would drive a new purpose for space launches, based solely on economic reasons, I can think of a few companies stepping up to provide the solution.

[KitemanSA]

For a brief discussion on the launch possibilities, check out this topic in the "General" forum. viewtopic.php?t=1220

[D Tibbets]

Good points in above posts
.
The solar wind could be a problem or a solution depending on engeneering and navigation.

Using mylar (or graphine?) reflecters with high efficiency solor panels as opposed to larger less efficient panels might have benifits in survivability and weight.

I don't know how much daytime gain you would get at 35,000 mile Geostationary orbit. The inclination of Earth's rotation would help some, except on the equanoxes. Having the collecters in non synrinized orbits would require beam aiming equipment to switch between ground stations and/ or multiple relay satallites with resultant increased complexity and cost.

There ar alot of questions. A few:
How transparent is the Earth's atmosphere to selected microwaves? Obvously, certain wavelengths can punch through the ionosphere or we would not be able to communicate with satallites, but at what efficiency?How massive would the power converting and transmitting equipment have to be? How would the presumably large waste heat loads be handled? What contigency plans would be needed to handle masive coronal mass ejections, or large micrometeorite bombardment from passing through the tail of a recent comet? It would be a bummer to have your multiple trillion doller systen destroyed or seriously degraded by inevitable (but hopefully rare) astronomical events (Earth's atmosphere and magnetic field do remarkable things to protect us here on the ground).

Dan Tibbets

[pfrit]

One other issue with solar cells is the limited lifetime of the cell, they tend to degrade over time, in the radiation and heat of space, I would think it would degrade quickly. So all these SPS units would need to be replaced at some point.

Actually, they degrade slower. Solar cell degradation comes mostly from fogging of the covering material. That comes from oxygen. Older cell coverings also had problems with UV, but for space based systems, that has never been an issue. My understanding of current systems is that life time in space is a function of dust collection on the cells. You can't hose them off in space and they tend to have an unavoidable magnetic charge that attracts dust.

[pfrit]

Good points in above posts
.
The solar wind could be a problem or a solution depending on engeneering and navigation.

This is a non problem. Every push in one direction is a push in the opposite direction 180 degrees in orbit.

I don't know how much daytime gain you would get at 35,000 mile Geostationary orbit. The inclination of Earth's rotation would help some, except on the equanoxes. Having the collecters in non synrinized orbits would require beam aiming equipment to switch between ground stations and/ or multiple relay satallites with resultant increased complexity and cost.

The satelites would be in the dark for hours a year in GEO.

There ar alot of questions. A few:
How transparent is the Earth's atmosphere to selected microwaves? Obvously, certain wavelengths can punch through the ionosphere or we would not be able to communicate with satallites, but at what efficiency?

Very transparent. Very high efficiency, though, to be honest, I would expect some atmospheric bloom if you tried to send very large amounts of power to one site. My guess is that for practicle use, 5-10 GW would be the ceiling for a single beam. After that, you would want a different transmiter to beam to a new spot.

How massive would the power converting and transmitting equipment have to be?

I would expect that it would scale nicely. If we expect a 1 ton refrigerator sized transmiter for every 100 MW, we would not be far off. Could an engineer chime in on this?

How would the presumably large waste heat loads be handled?

Tru dat! It is a solvable problem, but might be heavy. I would have to run some numbers on it, but my gut says that a cooling system would not have to weigh that much. The trick would be keeping the radiators as close to the heat source as possible, but at the same time keeping it in shade.

What contigency plans would be needed to handle masive coronal mass ejections, or large micrometeorite bombardment from passing through the tail of a recent comet? It would be a bummer to have your multiple trillion doller systen destroyed or seriously degraded by inevitable (but hopefully rare) astronomical events (Earth's atmosphere and magnetic field do remarkable things to protect us here on the ground).

Dan Tibbets

Satelites routinely shut down during a hit from a flare. That would be bad if you are depending on the power. A large flare could also push you severly off station and damage cables. On the other hand, how often is the Earth hit by a large flare directly? Once every 25 years? Large meteorite hits are EXTREMELY rare (Thats why they call it space). Small hits are expected and why you would want redundency and gradual expansion and replacement. The one thing that you don't have to worry about is space junk. For all intents and purposes, there is none in GEO. That is a LEO problem.

I have always liked Spaced based solar as there are other benefits to it. It could help mitigate hurricanes by breaking them up before they form and are a great military boondoggle. Yes, they would be an amazing weapon. No, they would not be the least bit survivable against any attack. That has never stopped congress from spending money on a system before. Does anyone remember the mission for the B2 bomber? They sold that. This is no less ridiculous as a weapon.

[MirariNefas]

The biggest unproven in all this is the magical "beaming the power back to earth" fantastical technology ... or is that fantasy tech.?

It doesn't exist, hasn't been developed or proven for GEO to surface ... the ionosphere and atmosphere are not layers significant radiation powers just "beam through" magically, that's why we're able to live on this ball of rock, relatively close to a massive, fusing ball of gas.

The science behind it is known, the technology a logical extension of that science. The only thing that hasn't happened is testing with the exact wavelengths and scale that would be needed in a full system. This is a small issue.

No, a Lagrange point would be BAD. From the earth, Lagrange points move through the sky in orbit. Your plant would be beneath the horizon 12 hrs a day

Yeah, I wasn't thinking there. I was caught up in agreeing that leo was bad and didn't think about the destination. Geosynchronous orbit is best. And yeah, solar wind would cancel across the orbit, so stationkeeping would be minimal.

As for mylar and all that, sounds good. I'm don't know which combination of technical details would work best, and I'm glad that you're giving it serious thought.

One other issue with solar cells is the limited lifetime of the cell, they tend to degrade over time, in the radiation and heat of space, I would think it would degrade quickly. So all these SPS units would need to be replaced at some point.

The example I cited was a technology designed specifically for space use, with a high radiation resistance. Yes, nothing lasts forever, but with the right choice of materials, 20 years is not unreasonable.

[MirariNefas]

There ar alot of questions. A few:
How transparent is the Earth's atmosphere to selected microwaves? Obvously, certain wavelengths can punch through the ionosphere or we would not be able to communicate with satallites, but at what efficiency?

Very transparent. Very high efficiency, though, to be honest, I would expect some atmospheric bloom if you tried to send very large amounts of power to one site. My guess is that for practicle use, 5-10 GW would be the ceiling for a single beam. After that, you would want a different transmiter to beam to a new spot.

Wikipedia mentions 85% as an expected transmission efficiency. I believe I've read that we can go above 90%, but maybe that's harder to do.

[pfrit]

There ar alot of questions. A few:
How transparent is the Earth's atmosphere to selected microwaves? Obvously, certain wavelengths can punch through the ionosphere or we would not be able to communicate with satallites, but at what efficiency?

Very transparent. Very high efficiency, though, to be honest, I would expect some atmospheric bloom if you tried to send very large amounts of power to one site. My guess is that for practicle use, 5-10 GW would be the ceiling for a single beam. After that, you would want a different transmiter to beam to a new spot.

Wikipedia mentions 85% as an expected transmission efficiency. I believe I've read that we can go above 90%, but maybe that's harder to do.

As I recall, the loss appears mostly on the ground (failure to recieve) and not in the atmosphere or transmitter. However, any way you look at it, 85% is more than good enough for government work. How much loss do you have in high tension tranmission lines? Something like .5% per mile?

[MSimon]

.5% per mile seems excessive. That says that a 300 mile transmission system loses about 80% of the energy transmitted.

[pfrit]

.5% per mile seems excessive. That says that a 300 mile transmission system loses about 80% of the energy transmitted.

OK, this is a real tangent. AC lines lose upwards of 1% per mile. A typical line length is 40 miles. I forget the business length for HVDC, but it is something like 300 miles. At that point HVDC saves more than it costs. Less for underwater cables (They are mostly HVDC if they are more than 40 miles). Less if you use pure copper cables (or anything that reduces resistance). The numbers get even more complicated when you include planned length. The cables are sized for the leg of the line that they are on. The other big part is how close you are running to capacity of the line. The lower percentage you use, the less the line loss. I am not an expert in this and I don't play one on tv either. .5% turns out to be generous. One of the reasons I like the idea of the polywell is it has the potential to build a distributed generation system. The list of reasons that that would be good is long and I am sure I don't need to elaborate them. The main reason that we have a centralized power generating system is economics. 1 4GW coal plant is much, much cheaper to build and operate than 4 1GW coal plants.

[icarus]

mirifaras: "The science behind it is known, the technology a logical extension of that science."

Oh yeah, now where I have heard that before?

Cartoon engineering by cartoon engineers ... anything's possible with these guys.

Commercial electric-power scale microwave transmission is a HUGE unknown. You are ignorant, naive or worse if you think this is just "technology a logical extension of the science".

[pfrit]

mirifaras: "The science behind it is known, the technology a logical extension of that science."

Oh yeah, now where I have heard that before?

Cartoon engineering by cartoon engineers ... anything's possible with these guys.

Commercial electric-power scale microwave transmission is a HUGE unknown. You are ignorant, naive or worse if you think this is just "technology a logical extension of the science".

Actually, it is not quite the stretch that you imagine. We beam microwaves to space and back all the time. Look at the dish on the TV news van. That part is mature engineering. I can't disagree with you about the problems with scaling it up multiple GWs of power. That is a real issue. Not as big an issue as getting it up into GEO and getting all the political authorities to agree to it. That's the pie in the sky part. Not the science and engineering part as much.

[MSimon]

mirifaras: "The science behind it is known, the technology a logical extension of that science."

Oh yeah, now where I have heard that before?

Cartoon engineering by cartoon engineers ... anything's possible with these guys.

Commercial electric-power scale microwave transmission is a HUGE unknown. You are ignorant, naive or worse if you think this is just "technology a logical extension of the science".

Actually, it is not quite the stretch that you imagine. We beam microwaves to space and back all the time.

At 85% efficiency?

Currently I believe the efficiency is in the 1E-6 range. Roughly .0001% That is a lot of zeros to make up with better engineering.

[KitemanSA]

Folks,
Go to the source. SSI has been into this for DECADES. Their data should help this discussion.