Caustics as an Alternate of Ray Tracing to Evaluate Heliostat Mirrors

Marios D Georgiou,Aristides M Bonanos,John G Georgiadis

doi:10.1155/2013/395659

Abstract

Solar thermal power generation is based on the concept of concentrating solar radiation to provide high temperature heat for electricity generation via conventional power cycles. The high relative cost of optical subsystems necessitates a careful study of their components. The capital cost of the heliostat field in central receiver power plants is significant, reaching up to 50% of the capital investment. Therefore, it is essential to maximize the energy yield from a heliostat with a given mirror area. Solar collector fields are typically modeled by ray-tracing or convolution methods; however, no general method is available for engineering analysis. We propose the use of caustics to predict the image of the sun reflected by an arbitrary mirror of focal length F and aperture a on a target. The method of caustics was validated against SolTRACE, a ray-tracing code developed by the US National Renewable Energy Laboratory (NREL).

Highlights

The global energy demand is increasing due to growing population, climate change, and depletion of fossil fuels
Caustic surfaces were employed in order to compute the solar image size and flux density on a stationary and predefined target corresponding to the receiver
There is no question that renewable energy, in particular solar energy, has an important role to play in meeting our future energy requirements

Summary

Introduction

The global energy demand is increasing due to growing population, climate change, and depletion of fossil fuels. This trend has given impetus to the search of efficient methods for the production of energy from renewable sources. The technologies currently under investigation are based on the concept of concentrating solar radiation to central receivers and generating steam to power cycles and generate electricity. The most common component employed for collecting the solar radiation is mirror reflectors. The mirrored surfaces assume different shapes depending on the ultimate concentration desired. The mirrors are integrated into fixed reflectors or dishes, or sun-tracking reflectors called heliostats, which improve the concentration efficiency of the system (cf Figure 1).

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Conclusion