In Lesson 1, we learned that the main function and purpose of the solar energy systems is to convert sun radiation - i.e., light or heat - into electricity. However, the efficiency of such conversion is not very high. One way to make many known solar technologies feasible with respect to their efficiency, total output, environmental impact, and cost is to concentrate the incoming radiation. Concentration of light will be the main topic of Lesson 2.
Sunlight is a practically inexhaustible natural resource which is also universally available. However, one of the disadvantages or difficulties related to its utilization is a relative low density of the solar flux. To generate sufficient power to meet demands of large populated zones, a vast area should be covered by solar collectors, and a significant amount of materials and resources should be spent on production and service of those collectors. This expense raises a question about economic viability of solar and initiates the search for ways to increase the sunlight conversion efficiency one way or the other. Generally, there are two ways to solve the problem - to improve the conversion device (intrinsic factor) or to increase the input flux (extrinsic factor). While the first avenue is subject to energy engineering research and innovation (e.g., developing new types of photovoltaic materials and devices), the second option - concentration of the incident solar flux - is already widely implemented. This lesson presents basic concepts for sunlight concentration and discusses typical optical geometries common in utility scale solar plants. This material provides background for further discussion of such technologies as concentrating solar power (CSP) or concentrating photovoltaics (CPV) later in this course.
By the end of this lesson, you should be able to:
- understand the physical principles of light concentration;
- list the main types of concentration systems used for utility scale solar facilities;
- calculate parameters of the typical light concentrating systems (CPC, parabolic concentrators).
Duffie, J.A. and Beckman, W.A., Solar Engineering of Thermal Processes, 4th Ed., John Wiley and Sons, 2013. Parts of Chapters 2 and 7. Please refer to particular sections of the lesson for more specific assignment.