Abstract:Compound parabolic concentrators are relevant systems used in solar thermal technology. With adequate tailoring, they can be used as an efficient and low-cost alternative in residential water heating applications. This work presents a simulation study using a ray tracing analysis. With this technique, we simulate the interaction between solar rays and solar concentrator to quantify the amount of energy that impinges on the receiver at a particular time. Energy availability is evaluated in a comparison of two configurations throughout the year: static setup at 21 • and multi-position setup; tilted with respect to the horizontal, depending on three seasonal positions: 0 • for summer, 16 • for spring/autumn, and 32 • for winter, with the aim to evaluate the amount of available energy in each season. The fact that a tracking system can be dispensed with also represents an economical option for the proposed application. The results showed that at 21 • , the proposed solar Compound Parabolic Concentrator (CPC) works satisfactorily; however, by carrying out the selected angular adjustments, the overall energy availability increased by 22%, resulting in a more efficient option. The most effective design was also built and analyzed outdoors. The obtained thermal efficiency was of~43%. The optical design and its evaluation developed herein proved to be a valuable tool for prototype design and performance evaluation.

One of the problems of designing a solar compound parabolic concentrator (CPC) is related to its manufacturing shape accuracy. The complexity of curving and holding the CPC profile in place is indeed a challenging issue, especially because there are no standardized molds and the process is typically handmade. It is very easy to provoke misalignment on the CPC surface and in consequence, divert the solar incident rays, severely affecting the optical efficiency of the system. This work presents a novel, inexpensive methodology to manufacture a CPC with accuracy by using basic tools. The design starts with the acquisition of a pair of medium density fiberboard wooden templates of the CPC profile that are used later to make a Styrofoam CPC mold then cut with a hot-wire technique. A high-reflectance anodized aluminum sheet is curved to approximate the CPC shape, and is then coupled with the temporary Styrofoam mold. The last part consists of the elaboration of a housing system to contain the parts. This is consolidated by a polyurethane resin that expands and fills all enclosure cavities, offering high stiffness and stability. A photogrammetry analysis was implemented for the validation of the surface shape accuracy. The results from the optical analysis show that this technique achieved a high degree of accuracy and homogeneity on the CPC surface shape.

Compound parabolic concentrators are relevant systems used in solar thermal technology. With adequate tailoring, they can be used as an efficient and low-cost alternative in residential water applications. This work presents a simulation study using a ray tracing methodology. With this technique we simulate the interaction between solar rays and solar concentrator to quantify the amount of energy that impinges on the receiver at a particular time. Energy availability is evaluated in a comparison of two configurations: stationary at 21° throughout the year and multi position setup; tilted with respect to the horizontal depending on three seasonal positions: 0° for summer, 16° for spring / autumn and 32° for winter, with the objective of increasing the amount of available energy in each season. The fact that a tracking system can be dispensed with also represents an economical option for the proposed application. The results showed that at 21°, the proposed system works satisfactorily; however, by carrying out the selected angular adjustments, the overall energy availability increased by 22%, resulting in a more efficient option. The methodology developed herein proved to be a valuable tool for prototype design and performance evaluation.