It is the only solar mirror construction that forms a solid flat structure. This is the basic requirement for the huge sun-protected oases - sun cities. Fresnel - Solar mirror Simple linear mirrors, stably clamped between 2 points. Simple actuator motor drives many mirrors simultaneously. Static receiver tube Very few moving parts Extremely low maintenance Tower power plant Thousands of individual mirrors - so-called heliostats - are set up around the tower. Over 1000°C working temperature makes the receiver at the top of the tower very vulnerable to repair. Requires a lot of space Heliostats Solar Mirrors Very complex tracking mechanism for each of the thousands of mirrors Very susceptible to mechanical failure and defocusing Extremely high maintenance Rinnen-Kraftwerke Trough power plants require a lot of space Parabolic solar mirror Very complex mirror construction Complex assembly Defocusing due to wind loads Fragile movable receiver tube Extreme maintenance costs