What is a distinguishing feature of a parabolic trough concentrator?

A distinguishing feature of a parabolic trough concentrator is that it focuses sunlight to a line, not just a point, where a receiver captures the concentrated solar energy. This design consists of a long, parabolic-shaped mirror that reflects sunlight onto a receiver positioned at the focal line of the trough. The concentration of sunlight significantly increases the temperature, allowing for efficient energy collection, often used for heating fluids which can then be used to produce steam and drive turbines for electricity generation.

The other choices do not accurately describe this specific type of solar concentrator. While it is true that parabolic troughs operate using mirrors, their defining characteristic is the effective focusing mechanism which is best described by their linear concentration capability. This means they capture sunlight over a length rather than capturing it at a uniform angle, as stated in one of the choices, which characterizes lens systems rather than troughs. Additionally, parabolic troughs are typically not compact and portable; they are designed for large-scale solar energy production and require significant space for installation.