Re: energy for cloud-cuckoo land
Why from space? Because except for a few days around the equinox, the satellite has sunlight 24/7 (and even then, the longest "night time" is about 70 mins in 24 hours). The Sahara has nights in between all the daytimes, which is not great if you want 24 hour power.
As far as the amount of power and birds, etc, the normal plan is to beam the power with a density of about 1kW/M^2, which is the same a normal sunlight. One thing missing from this report is efficiency - normally conversion to microwave is normally only about 50% efficient.