However, to the authors' knowledge, it has not been shown how this approach could be implemented at a scale commensurate with CSP. Water is required for mirror washing, steam cycle maintenance and often cooling. Air cooling is technologically feasible but lowers the plant efficiency and increases capital costs by roughly 10 per cent (USDOE, 2009,2012). The trend is toward more freshwater-efficient cooling technologies for CSP and other thermo-electric generation.