Space Based Solar Power

[Chirios]

Just got finished reading the Department of Defence "Space‐Based Solar Power As an Opportunity for Strategic Security" notice. (Yes I know it's been around for a while but, I'm new here). Anyway, my problem with this idea is that while it could be built, is it really scalable without cheaper launch capabilities i.e. space elevators etc? Also, could you maintenance one of these things unless there was a permanent manned (or robotic) presence in space? Also how good is the wireless power transmission that you would need to have one of these things in orbit? And finally, once you've got all of these things down, how expensive would it be to get something like this up and running? For it to be feasible, it would have to be at most as expensive to build, set up and maintain as a nuclear power plant.

If a country managed to get a program like this up and running within the next ten or twenty years it would change the political game massively. It would (to borrow the term) be a geopolitical singularity. I can imagine the country that first developed this becoming like a modern day Saudi Arabia, only more so, since no developing countries have space capabilities and most European industrialised countries would be far more willing to buy another countries SSP system than spending the billions required to develop their own. If the Americans did it first then their power would be effectively be completely consolidated since they would control, practically, the worlds energy supply, and if another country or union did it then they would be brought into conflict with the States, since America would be unwilling to place something as important as it's energy supply in the hands of a European or Asian nation. Russia would immediately lose a lot of it's clout amongst the former Soviet Union and Europe, their links with Germany would be all but severed; all the oil producing nations in Africa; the Middle East (which to be fair is the entire Middle East); and Latin America would see their economies crumble.

So is this a feasible option within the next say, fifty years? Can the above problems be surmounted? And are there any other implications of this technology becoming widespread that I've missed?

[Temujin]

Regarding oil, it's used for a lot more than just energy. So until a viable replacement for petrochemicals is developed, it will still be a valuable resource.

[kc8tbe]

Wouldn't nuclear power still be much cheaper, especially if we move to a Thorium fuel cycle?

[Junghalli]

PERMANENT has some information on them.

The advantage over ground based solar panels is you get more light (because the atmosphere absorbs some sunlight) and you can have the equivalent of 24/7 high noon equatorial sunlight. The disadvantage is you have to build the facility in space, and with present technology putting stuff in space (especially a high orbit like GEO) is going to be expensive. Ultimately (neglecting other competing energy sources like nuclear and hydroelectric) it would come down to which is cheaper: building ~55,000 km^2* of solar panel in orbit or building several times that on the ground.

*Calculated enough to satisfy current world energy demand with 20% efficient solar panels, realistically we'll probably be getting energy from multiple sources so it would be less. For perspective, this is equivalent to a single square panel ~235 km on each side.

[Sea Skimmer]

Nuclear plants need a lot of cooling water; that limits just how many we can build for a given land area even with very elaborate and thus expensive dry cooling towers. Almost all current nuclear plants use wet cooling towers that evaporate very large amounts of water, thus the huge steam plums you can see from 25 miles away. Solar planets on the ground guzzle up land, and not everyone has a giant desert to spare for that. The down link antenna for space based power would be very large too, but it would also have a very high capacity and one down link antenna could easily get power from multiple large solar arrays in space.

It’s no coincidence that the main proponent of space solar power is Japan, which has little land and an already very densely exploited sea coast, with no water supplies on land really fit for nuclear cooling needs. Also building nuclear plants in earthquake zones is not cheap, and nothing can assure the safety of a plant if a fault line runs right under it.

Lots of options exist for reducing the cost of space launch, without using infeasible concepts like a space elevator. The main requirement to make lower costs happen though is a large secure market for the launch capability to make it worth spending the money to develop and deploy it. National level space solar power efforts would be ideal stimulus. However they’ve got to make the downlink antenna technology work first, and that hasn’t happened yet.

[Simon_Jester]

What are the difficulties on the downlink end?

[Sea Skimmer]

All the details of engineering unprecedented size electronically steering antennas that need to continuously handle hundreds of megawatts, placing them immensely beyond any radar technology ever and with a requirement for high efficiency on top of it all. Otherwise the orbital satellite component will need a huge mass of expensive heat sinks to cool itself. This also matters for the ground antenna component, since a 1+ gigawatt capacity antenna is going to end up with the same kind of cooling demands as a nuclear plant unless its high efficiency too. Though shear size would allow for a fair measure of direct air-wind cooling anyway.

Conventional dish antennas would actually make this work easier, electronic beam steering is not easy even after 40 years of work, but then you would have lots of moving parts in space which are going to limit the lifespan of the satellite. If anything breaks you can’t track the ground antenna and the whole system is worthless. So far testing has demonstrated 100 mile class ranges for microwave power transmission, but only at power levels of about 20 watts. No one has come even remotely close to prototyping even a scale model of the required hardware. IIRC Japan says 2020 to place such a prototype in orbit, to be hopefully followed by full scale prototype hardware in 2030.