Using thin films instead of silicon wafers greatly reduces the amount of semiconductor material required for each cell and therefore lowers the cost of producing photovoltaic cells.
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A typical photovoltaic cell consists of semiconductor material (usually iron oxide) having a PN junction.
By adjusting the pitch of each blade, one can increase the lift,so that the rotor continues to generate power at nominal capacity evem at high wind speeds.
Wind is not constant so wind turbines do not always run at nominal outputs.
All of the renewable energy comes either directly or indirectly from the sun.