Seite - 134 - in Clean Water Using Solar and Wind - Outside the Power Grid

134 Clean Water Using Solar and Wind: Outside the Power Grid To use hydrogen for energy storage is not new. Dr Allan Hoffman has been one of the key scientists working in Washington DC to influence the development of renewable energy and the awareness of the water- energy nexus. In 1995 he served as Associate Deputy Assistant Secretary and then Acting Deputy Assistant Secretary for DOE’s (Department of Energy) Office of Utility Technologies (OUT) in the Bill Clinton administration. This Office had responsibility for developing the full range of renewable electric technologies as well as hydrogen and energy storage technologies. In 1995 he wrote an OUT report: “I also believe that over this time period, hydrogen will emerge as an important energy carrier to complement electricity, given its ability to be used in all end use sectors and its benign environmental characteristics.” The main attraction of hydrogen is that excess energy can be stored for a long time, not only from day to night, but also between seasons. For example, at northern latitudes excess renewable energy can be produced during the summer. Battery power cannot supply energy for any longer than a few days. If the excess energy is stored as hydrogen, it can be reused as electricity during the cold winter. Prototype systems using this facility are already in use. Hydrogen is one of the most promising ways of dealing with longer-term energy storage. Simply explained, excess electricity is used to electrolyse water into hydrogen and oxygen. The hydrogen is stored and later used in fuel cells that generate electricity. 10.5.1 Electrolysis of water In electrolysis, water is split into hydrogen and oxygen using electricity. Using excess electric power from solar PV or wind does not create any greenhouse gas to produce the hydrogen. At the same time the cost for extra energy is practically zero. The electrolysis takes place in a device called an electrolyser. There are a lot of different configurations, but the principle and the key reactions are shown in Figure 10.3. Different The main attraction of hydrogen is that excess energy can be stored for a long time and then reused as electricity. Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user