[nickhalfasleep]

In it's favor, a solar power satellite can get light nearly 100% of the time, while on the ground you are luck to average 50% with rotation and weather.

[cvbncvbncgbc]

In what orbit, that doesn't require propulsion, do you get constant line of sight?

[danielweber]

They nearly always call for geosynchronous orbit, because they want to always be over the rectenna on the ground.

The Earth will occasionally put such a satellite into shadow, but remember that the Earth is tilted, and so is the equator.

Getting up to GEO is hella expensive.

[mikeash]

Just to put some numbers on it, GEO doesn't intersect the Sun-Earth line most of the time. The Earth's shadow touches GEO for a couple of weeks around the equinoxes, resulting in up to 70 minutes of shadow per day in that period. The rest of the time, they're in sun 100% of the time. So, as low as a 95% duty cycle at the worst point in the year, and 100% for most of the year.

[oh_sigh]

L1

reference: http://en.wikipedia.org/wiki/Lagrangian_point#L1