SBSP = space baded solar power

[neilsox]

We need to pursue all promising alternative energy sources faster than seems prudent except nuclear which has extreme down side if we fast track. The main objection to thorium nuclear reactors is even massive funding would require more than a decade to get to the second gigawatt except at high risk. This is especially true as powerful people want thorium to fail.
If the properties of liquid nitrogen super conductors can be optimised, they are likely practical for long distant power lines. Near term, HVDC = high voltage direct current power lines are operational and superior to 60 hertz three phase power lines for up to about 1500 kilometers. We could build a town that uses dc instead of ac appliances, as avoiding the conversion back to ac may reduce losses if not improve cost effective. Can dc wind turbines be operated in series to produce a million volts dc? Likely, but it may be impractical for several reasons. Yes, electric vehicles can help stabilize a dc grid, but the concept is not well established for ac nor for very high voltage dc. The cost is unknown and vehicle owners who decide at the last minute to take a trip will be unhappy, if the grid just halved the range of their vehicle. This will upset most consumers even if it happens rarely.
For SBSP = space based solar power, I like sun synchronous orbit as the satellite can stay over the sunshine terminator, and thus be able to beam power approximately straight down to cities that are experiencing peak demand. (Ten degrees above the horizon, in all possible directions means the rectenna must have lots more area than for a beam coming from directly above) Early evening is when the power is worth up to 25 times the midnight price. Other advantages are the satellite is at lower than GEO orbit so the aiming is less critical and the transmitting array can be smaller and all the nations of Earth can be served at least rarely by a single solar synchronous satellite in a semi polar orbit. About 12 satellites are needed to provide hundreds of rectennas every late afternoon and every early evening.
Lasers may be available soon as an alternative to micro waves. Existing solar sites can receive, up to several megawatts of laser energy, as small as 4000 square meters = a 64 meter square, while rectennas need to be much larger because microwaves illuminate a larger spot. A receiving site dedicated to the transmitted frequency/wave length will be about twice as efficient, but we can tolerate reduced efficiency for demonstration purposes. Neil

 

[theridane]

There was a war about this more than a century ago, I suggest you read up on the subject before talking about DC power grids (a couple of hints: DC is really hard to upvolt into megavolt ranges, whereas with AC it's relatively trivial, DC devices like motors and gennies are inherently more complex and less efficient, etc.).

"Several megawatts" from an orbital laser using a 4000 m² collector array? An off-the-shelf (35% eff.) solar panel would get you about 1.4 MW from that area. How much is several, is it worth it?

 

[MeteorWayne]

This is a duplicate of a few other discussions, so might be merged with one of them.

And what does baded mean anyway?

 

[neilsox]

Hi theridane: I got 1.9 megawatts instead of 1.4 in space, but I was typing about a 4000 square meter solar panel on Earth's surface that would average perhaps one megawatt at noon in New Mexico. About 0.1 megawatt at 6 pm plus perhaps 3 megawatts from the Sun synchronous satellite. I agree the sun synchronous satellite needs about 10,000 square meters of 35% efficiency PV = photovoltac to deliver a 3 megawatt beam, due to conversion losses from dc to microwaves and beam losses in the atmosphere. Lasers are presently somewhat less efficient than magnetrons, but perhaps better due to smaller transmitting and receiving arrays. Lasers can also carry high speed data, which may be more valuable than the electricity since a modest antenna can pick up the data over about half of Earth's surface and about half of the inner solar system due to scattered energy.
Modern electronics can change voltage up or down to a million volts dc at about the same efficiency as a transformer and line losses are about half for long dc power lines compared to 60 hertz 3 phase plus we avoid the problems of phase lock using dc. The line loss of 60 hertz can be reduced by using thicker copper wires, but Earth may not have enough copper production to double the length of the average high tension power line using ac. Large amounts of electricity are used to produce aluminum wire. Neil