Prerequisites:

Description:

    This is the technology of putting solar power devices in orbit (either of a planet or solar orbit), and beaming the power (via masers) to a place where it's being used.  This technology is also used for almost any power transmission technology across the solar system, as this also includes the technology of sending and receiving electric power via microwaves.
    Orbital solar power devices consist of a huge (truly vast, as several square miles is kind of a minimum) layer of material to intercept quite a lot of light coming off of the sun.  The idea is to convert this light into a usable electric current at the site where the power is needed.
    The Photovoltaic version turns the extra energy of photons hitting the black side into a potential difference between two plates on that side.  The Heat Engine version relies on the incoming solar energy to heat one side, and has a passive radiative cooling system on the other side.  Various heat engine methods can then be used to turn this difference into usable energy.
    The ultimate solar power satellite is a hybrid device; relying on a combination of the two above technologies.  It consists of a layer of photovoltaic panels, which are both electrified directly, and in effect heated the surface, and that heat works as the hot side of a heat engine.  This version is the most efficient in terms of power produced per unit of area of sunlight obstructed, and is thus what you want to use once you've filled up most of the good orbital locations around your star.  Either photovoltaic or heat engine designs (depending on contributory development) will be most efficient in terms of manufacturing work and launch mass and is what you want to use for early development when you have lots of good orbits left.
    This technology along with a whole lot of power satellites can eventually lead to a Dyson Sphere, which consists not (as is sometimes erroneously stated) in a solid shell all the way around a star, but is actually any manmade construction that completely blocks all of the light coming out of a star.  A really big swarm of power satellites should be capable of doing just that.  Before the Dyson Sphere technology is researched, there is a pretty sharp limit on the percent of the star's light your satellites can effectively block (picking the correct orbits can be difficult).