Aplanats and analytic modeling of their optical properties for linear solar concentrators with tubular receivers

We analyze the performance of aplanats as linear solar concentrators for tubular receivers, principally whether, relative to parabolic troughs, they can boost concentration at high intercept factor. For the two basic viable categories of aplanats, we derive an analytic model for calculating the intercept factor: the first such exact solution, which obviates the need for raytracing. The aplanats admit collection both from single- and double-reflection rays - fully accounted for by the analytic model. Illustrative designs that achieve high intercept factor and can increase concentration substantially are presented.