For each drop-down box, select the appropriate word from the drop down that best completes the sentence. Solar thermal electricity production harnesses the power of sunlight to generate electricity through the use of concentrated solar power (CSP) systems. In CSP systems, sunlight is concentrated using mirrors or lenses onto a , containing a heat transfer fluid such as molten salt. The concentrated sunlight heats the fluid to high temperatures, which is then used to produce steam in a heat exchanger. The steam drives a turbine connected to a generator, producing . One of the main advantages of CSP systems is their ability to extend the usage. Thermal allows CSP plants to continue generating electricity even when the sun is not shining, such as during cloudy weather or at night. CSP systems can be configured in various designs, including parabolic troughs, power towers, and dish/engine systems. Parabolic trough systems use curved mirrors to focus sunlight onto a receiver tube running along the of the trough. Power towers use a central receiver located atop a tall tower, with an array of mirrors, or heliostats, reflecting sunlight onto the receiver. Dish/engine systems consist of a parabolic dish that concentrates sunlight onto a receiver at the dish's , where it is used to generate steam for electricity production