Optical concentration obtained by light confinement bears unique features that can increase the efficiency of a
photochemical reactor. A suitable implementation of this method for a solar reactor is a series of parallel tubular
receivers sealed in a slab-shape reflective cavity, in which light is trapped thanks to a self-adaptive optical filtering
mechanism. To predict the concentration in such a generic configuration, we had previously established an analytical
model based on idealistic assumptions, which are not valid in our real configuration. Here, we use analytical calculations
and numerical ray-trace simulations to investigate how the finite size of the latter impacts the prediction of our model
and extrapolate design guidelines for minimal departure from ideality. We apply these guidelines to design an optical
concentrator maximizing flux density on tubular receivers and discuss the upper bound to the method, as well as the
benefits from its unique features. Accounting for practical and technological limitations, this method can provide optical
concentration in the order of ten suns in our generic configuration.
A thorough knowledge of the angular distribution of light scattered by an illuminated surface under different angles is
essential in numerous industrial and research applications. Traditionally, the angular distribution of a reflected or
transmitted light flux as function of the illumination angle, described by the Bidirectional Scattering Distribution
Function (BSDF), is measured with a point-by-point scanning goniophotometer yielding impractically long acquisition
times. Significantly faster measurements can be achieved by a device capable of simultaneously imaging the far-field
distribution of light scattered by a sample onto a two-dimensional sensor array. Such an angular-to-spatial mapping
function can be realized with a parallel catadioptric mapping goniophotometer (CMG).
In this contribution, we formally establish the design requirement for a reliable CMG. Based on heuristic considerations
we show that, to avoid degrading the angular-to-spatial function, the acceptance angle of the lens system inherent to a
CMG must be smaller than 60°. By means of a parametric study, we investigate the practical design limitations of a
CMG caused by the constraints imposed by the properties of a real lens system. Our study reveals that the values of the
key design parameters of a CMG fall within a relatively small range. This imposes the shape of the ellipsoidal reflector
and drastically restricts the room for a design trade-off between the sample size and the angular resolution. We provide a quantitative analysis for the key parameters of a CMG for two relevant cases.