The article
here.

The news is that Southern California Public Power Authority (SCPPA
) has approved a Power Purchase Agreement (PPA) with EnviroMission Limited to
purchase power from EnviroMission's Solar Tower power station development
planned for Arizona.

The "solar chimney" is a straightforward idea. A massive tower funnels hot air
driven upwards by a temperature differential and spins turbines at the base of
the tower to create electricity. It's been demonstrated at a small 50-kilowatt
scale in Manzaneres, Spain. But to make it a reality at utility scale, the tower
needs to be 800 meters to 1,000 meters high (as a reference point, the Empire
State Building is 373 meters high) and constructed of reinforced concrete or
some other durable material. The collector base -- in effect, the real estate
around the tower -- needs to be miles in diameter. Enviromission itself
described a proposed project in Australia stretching 1,000 meters high, 130
meters in diameter and with a 5-kilometer diameter collection area. As with all
projects of this size, there is a considerable amount of embedded energy in the
infrastructure itself.