Thousands of mirrors track the sun in two dimensions and reflect the sunlight to a boiler that sits atop a tower. When the concentrated sunlight strikes the boiler’s pipes, it heats the water inside to 550°C – more than 1000° F – creating superheated steam at the temperature necessary to achieve the industry’s highest operating efficiencies. This high-temperature steam is then piped from the boiler to a standard turbine where electricity is generated. From here, transmission lines carry the power to homes and businesses. Nothing is wasted in this process. In order to conserve precious desert water, the steam is air-cooled and piped back into the system in a closed-loop, environmentally-friendly process.
BrightSource’s smaller, flat mirrors are more efficient, simpler to manufacture, and cost less to install than parabolic mirrors used in solar troughs. The heliostats are highly accurate and have over 35 years of longevity with practically zero maintenance with the exception of cleaning. The average 100 megawatt BrightSource Energy solar plant will consist of 50,000 mirrors.
The aiming control system and the layout of solar fields are optimally designed to collect sunlight and send it to the receiver in a manner that maximizes steam output.
The receiver is a traditional high-efficiency boiler positioned on top of the tower. The boiler converts the concentrated energy of the sun reflected from the heliostats into superheated steam. The boiler is supplied by conventional boiler manufacturers and complies with standard boiler design parameters, providing performance warranties and industry best practices. The boiler’s tubes are coated with a material that maximizes energy absorbance. The boiler has steam generation, superheating and reheating sections and is designed to generate superheated steam of 550 C of temperature and 160 bars of pressure.
The power block consists of a conventional steam turbine generator with a reheat cycle, and auxiliary functions of heat rejection, water treatment, water disposal and grid interconnection capabilities. The integration of high-efficiency pre-existing turbine technologies provides performance warranties and enables the system to maximize thermal to electricity efficiencies. By using air, rather than water, to cool the steam, the power block uses 90 percent less water.
