Ann: CEO Shareholder Update, page-57

Just a comment on efficiency. For fossil fuels a typical modern coal plant is about 35% efficient. A gas turbine is around 60% (CCGT) which is one reason there is a move from coal to gas powered plants. Even fast start gas OCGTs are around 40% efficient.

A typical solar power system is about 15% efficient (150 Watts per m2).

An Enviromission solar updraft tower has a theoretical efficiency of under 1% (5-10 Watts per m2). That is why such huge collectors, each covering many square kilometers, would be needed.

The oft mentioned solar updraft test plant in Spain had an efficiency of under 0.1% (1 Watt per m2).