Another way to extract energy from solar radiation is the solar concentrator (CS). A magnifying glass held in the sun can start a fire. Such a glass is acting as a miniature solar concentrator. A solar [thermal] power station is constructed by capitalizing on this principle: concentrating solar radiation on a focal point. Instead of a lens, a series of hollow mirrors is used. In the focal area of these 'solar throughs', runs a metal tube that contains water, salt or another heat transporting medium. The concentrated solar irradiation heats the tube and its contents. The heat transport medium is pumped to a steam turbine which powers an electricity generator. The solar throughs can be tilted to make full use of the daily course of the sun through the sky.

There is a preference to built CS power stations in extremely sunny locations. Several solar power stations exist already for quite some years. The most well known are the CS power stations near Kramer Junction, Mojave desert, California (see http://www.solel.com/products/pgeneration/ls2/kramerjunction/). In The Netherlands the GEZEN foundation (Stichting GEZEN) propagates an effort to construct CS power stations to reduce CO2 emissions and to decrease dependence on imported oil. The best economic opportunities for CS power stations occur in and beyond Southern Europe, e.g. Spain and North Africa. These power stations can be linked to a pan-European high voltage transmission network. Let's build such power stations!

Hot air rises. Let the sun heat air and guide this hot air through a chimney, and you have constructed a solar chimney. Next make this chimney extra high and wide, and the concept of a solar tower is born. Mount a wind turbine horizontally inside the tower and you have constructed a solar tower power station. A fantasy? Not quite. A prototype of a 50 kW solar tower power station has been tested in Manzanares, Southern Spain in 1989 (www.visionengineer.com/env/solar_flue.shtml).

The Enviromission company of Australia is in the process of building a very big, 200 MW commercial solar tower power station. An greenhouse area of 10 square kilometers will be covered with a construction with a glass canopy. Air under the glass canopy will heat up to 35 degrees centigrade. This hot air can escape via a 1000 meter high and 120 meter wide chimney. In the base of the chimney a number of wind turbines with horizontally positioned blades will turn and convert the energy in the massive airflow into electricity. Because of its sheer size, the power station will be able to operate 24 hours per day.