Ships moored at Naval Base San Diego are tied into shore power via cables and mounds on the pier. These power mounds allow the ship to power down its engines and run its systems on shore power. This reduces emissions from the fuel burning engines that generate power when the ship is at sea. The flexibility of going from shore to ship's power has also enabled the Navy to reduce the strain on the grid during peak energy demand during the summer months, reducing the need for rolling blackouts in areas near the base. (U.S. Navy photo by Mass Communication Specialist 2nd Class Aja Bleu Jackson.)