Abstract of Solar Power Towers
• Solar power towers also known as Concentrated Solar Power (CSP) Towers generate electric power from sunlight by focusing concentrated solar radiation on tower mounted heat exchangers.
• The system uses hundreds to thousands of sun-tracking mirrors called heliostats to reflect the incident sunlight onto the receiver.
• These plants are best suited for utility-scale applications in the 30 to 400 MW range.
• The limited supply of fossil hydrocarbon resources and the negative impact of CO2 emissions on the global environment dictate the increasing usage of renewable energy sources.
• Concentrated Solar Power (CSP) is the most likely candidate for providing the majority of this renewable energy, because it is amongst the most cost-effective renewable electricity technologies and because its supply is not restricted if the energy generated is transported from the world's solar belt to the population centres.
• In power tower systems, heliostats (A Heliostat is a device that tracks the movement of the sun which is used to orient a mirror of field of mirrors, throughout the day, to reflect sunlight onto a target-receiver) reflect and concentrate sunlight onto a central tower-mounted receiver where the energy is transferred to a HTF.
• This energy is then passed either to the storage or to power-conversion systems, which convert the thermal energy into electricity.
Heliostat field, the heliostat controls, the receiver, the storage system, and the heat engine, which drives the generator, are the major components of the system. For a large heliostat field , a cylindrical receiver has advantages when used with Rankine cycle engines, particularly for radiation from heliostats at the far edges of the field. Cavity receivers with larger tower height to heliostat field area ratios are used for higher temperatures required for the operation of turbines. These plants are defined by the options chosen for a HTF, for the thermal storage medium and for the power-conversion cycle.
HTF may be water/steam, molten nitrate salt, liquid metals or air and the thermal storage may be provided by PCM (phase change materials) or thermally insulating materials.. Power tower systems usually achieves concentration ratios of 300-1500, can operate at temperatures up to 1500 o C.