The basic difference between the sunlight available on earth and outside in the space is that in space the light is undiffused by atmosphere. So the energy available is more.
Unlike earth, in space there are no winters and no cloudy days, sunlight is available for 24 hours a day.
Earth solar power plants can be set up only in deserts, whereas using SSP this energy can be transmitted to any point on earth.
Production of SPS does not require any kind of fuel and does not create any waste products like CO2, thus does not add to global warming.
The concept of solar power satellites seemed very farfetched in the days when it was just conceived. But today it is no more a remote possibility with many space centers working on this project. This technology could be a perfect solution to the power hungry earth in the near future.