The amount of energy from the sun that reaches Earth each day is enormous. But only a small portion of the energy radiated by the sun into space strikes the earth. About 15 percent of the sun’s energy is reflected into space before reaching the earth’s surface. Another 30 percent of the energy is used in the planet’s heat cycle, evaporation of water to run the water – weather cycle, wind, and waves. Only a small fraction of the energy is actually utilized for photosynthesis in plants. The rest could be used to supply our energy needs.