; (C) differentials in salinity and pressure gradients; and (D) differentials in water temperature, including ocean thermal energy conversion. (4) National laboratory The term National Laboratory has the meaning given such term in section 2(3) of the Energy Policy Act of 2005 ( 42 U.S.C. 15801(3) ). (5) Water power The term water power refers to hydropower, including conduit power, pumped storage, and marine energy technologies. (6) Microgrid The term microgrid has the meaning given such term in section 641 of the Energy Independence and Security Act of 2007 ( 42 U.S.C. 17231 ). 633. Water power technology research, development, and demonstration The Secretary shall carry out a program to conduct research, development, demonstration, and commercial application of water power technologies in support of each of the following purposes: (1) To promote research, development, demonstration, and commercial application of water power generation technologies in order to increase capacity and reduce the cost of those technologies. (2) To promote research and development to improve the environmental impact of water power technologies. (3) To provide grid reliability and resilience, including through technologies that facilitate new market opportunities, such as ancillary services, for water power. (4) To promote the development of water power technologies to improve economic growth in the water power sector, including in coastal communities. 634. Hydropower research, development, and demonstration The Secretary shall conduct a program of research, development, demonstration, and commercial application for technologies that improve the capacity, efficiency, resilience, security, reliability, affordability, and environmental impact, including potential cumulative environmental impacts, of hydropower systems. In carrying out such program, the Secretary shall prioritize activities designed to— (1) develop technology for— (A) non-powered dams, including aging and potentially hazardous dams; (B) pumped storage