The sun releases ample energy to power all of mankind’s energy needs, but that energy is fairly diffuse by the time it reaches earth (~ 100 W/m^2). This means that large areas of land would be required to meet all of our energy needs with solar, land that might otherwise be used for other purposes like agriculture or development.
One solution to easing this land-use debate is to put the solar panels on water. The French company Ciel et Terre has developed technology that allows arrays of solar panels to float directly above bodies of water such as lakes or reservoirs: http://www.ciel-et-terre.net/floating-solar-system/
Recently, it was announced that the world’s largest floating solar power plant would be installed in Japan: http://news.discovery.com/tech/alternative-power-sources/worlds-largest-floating-solar-plant-planned-for-japan-141224.htm
Besides avoiding competition for land, floating solar panels offer the additional benefits of i.) decreasing evaporation of water and ii.) allowing the solar panel to operating at lower temperature, and thus higher efficiency.
Esposito Research Group Blog 