Concentrated Solar Power Plants (CSP) use steam to make energy. This is very much like a conventional power plant except in CSP plants there is no unwanted emissions such as those found in conventional coal power plants. Solar radiation is used to produce heat instead of fossil or nuclear fuels. A popular type of CSP is the parabolic trough power plant. In order to gain the high temperatures required, troughs made up of parabolic mirror segments, track the sun and focus the solar radiation the onto receiver tubes. A heat transfer fluid runs through these receivers and is heated up to 750F (400C). This fluid is used to produce the steam required for a steam turbine to generate electricity.