To determine watts per square foot of a solar module.  First, multiply the length by the width of the panel, these are found in the manufacturer's data sheet.  Convert this number to square feet by dividing by 144.  Then divide the module's rated power wattage by this number.  This is the watts per square foot, the more power per square foot the greater power production for the space used.

Example:  A 175 watt solar module has dimensions of 62" X 39".  62 x 39 = 2418.  Divide 2418 by 144 = 16.79 (sq. ft. of module).  Divide 175 by 16.79 = 10.42 watts per square foot.

The earliest known record of the direct conversion of solar radiation into mechanical power belongs to Auguste Mouchout, a Frenchman in 1860.  He was concerned about his country's dependence on coal.

Have you ever wondered why pro golfers look in the hole before they putt?  It's not to see if the group before left a ball in the hole.  It's to see which way the grass is growing.  The small blades of grass on the putting surface, like other plants, follow the movement of the sun during the day.  You can add a tracking device to a ground mounted PV array, it follows the movement of the sun, just like the blades of grass.  By the way, the direction of the grass blades effects the movement of the ball.

One of the most famous quotes on renewable energy is by Thomas A. Edison.  Reportedly, Mr Edison made the statement in March 1931, to Henry Ford and Harvey Firestone.  He said, "I'd put my money on solar energy...I hope we don't have to wait till oil and coal run out before we tackle that".