Seite - 126 - in Clean Water Using Solar and Wind - Outside the Power Grid

126 Clean Water Using Solar and Wind: Outside the Power Grid 620 MW in 2013 and 1,719 MW in 2016. In the year 2016 global battery capacity grew by 50% (REN21, 2017a). This rapid battery development, together with low-cost solar PV systems, is seen by many experts as a potential disruptive technology that could dramatically change future energy markets. The number of electric vehicles is increasing and as a result automotive companies are expanding into energy storage research and development. Tesla has released the Powerwall battery and companies like Mercedes-Benz and BMW are now marketing stand-alone batteries. This development will hopefully have a positive influence on the solar energy market. Not all batteries are created equal, even batteries with the same chemistry. Batteries can be designed either to be high-power or high- energy and are often classified as one or other of these categories. We concentrate on three categories of batteries: lead-acid, lithium and saltwater. Lithium batteries have the longest lifetime, saltwater shorter and the lead-acid batteries the shortest lifetime. Batteries are often evaluated according to their energy density (kWh/ litre of battery) or total weight. This is important in transportation and in many consumer products like mobile telephones. By this measure lithium batteries have so far been the most successful. However, their cost is relatively high. A stationary battery can be assessed in a different way: even if its energy density is less the battery may still be successful; the total weight is not critical, so other properties can be considered. Consequently, a lot of attention is directed towards flow batteries and saltwater batteries. 10.3.1 Lead-acid batteries The cheapest and most common battery is a standard car battery of the lead-acid type. These batteries are a proven technology that has been used in off-grid energy systems for decades. This is probably the least expensive alternative available for households. A drawback of deep- cycle lead-acid batteries is their expected short lifetime. Even if they Stationary batteries should be evaluated differently from batteries for transportation. Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user