Category Solar Collectors and Panels, Theory and Applications

. Theoretical and experimental comparison of the collectors

1.1 Theoretical efficiency of collectors

Our modular device was composed of units, each of which consisted of a concentrator coupled to an optical fibre that transported the power to the utilisation point. Characteristics and performance of the six optical projects were theoretically estimated, calculating in particular the collection efficiency of each collector coupled to a 5m quartz fibre of size 0.6mm and NA=0.48. Table 2 summarises these optical features to compare the concentrators presented in Sect. 2.

Table 2 reports the power collection performance for the six concentrators of Tab. 1: the collector efficiency factor is the ratio output power / input power, while the total efficiency factor corresponds to the collector coupled to the fibre...

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Conic Cassegrain collector

The optical project of the Catadioptric Concentrator Monoblock (CCM) was developed with the aim of optimising the optical characteristics of the collector but also its compactness. In Tables 1 and 2 it is classified as conic Cassegrain and indicated as C1. The first surface is elliptic and the second one is spherical. The maximum EPD is 56mm, f is 55mm and f/# is 0.98. As for the previous collectors, C1 fulfils the fibre-matching requirements: the output

image011

(a) (b)

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image013angle 0=26.98° is within the fibre acceptance angle (28.7°) and the total image diameter (0.534mm) is considerably shorter that the fibre size (0.6mm).

The optical working principle of this collector is well known: it consists of two optical elements in a coaxial configuration of Cassegrain type...

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Parabolic collectors

The parabolic system is composed of two mirrors, the primary is parabolic and the secondary is flat, with or without correction lens: B1 and B2, respectively. The position of the secondary mirror is analogous of the corresponding Mangin layouts A1 and A3 shown in Figures 3a and 3c.

Figures 7a and 7b present the standard views of the optical designs for B1 and B2. To provide a more realistic view of B2, Fig. 7c presents a three-dimensional model of the Parabolic with lens.

The optical parameters are summarized in Tab. 2 of Sect. 3.1, but for B1 the maximum reachable EPD is 70mm, f is 65mm (at a wavelength of 580nm), f/# is 0.93 and the maximum axial angle 0 is 28.3°; while for B2 EPD is 71.1mm, f is 65mm, f/# is 0.914 and 0=28.67°.

The optical quality of B1 is very good; the total spot di...

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Mangin collectors

The Mangin system is composed of a glass meniscus, aluminised on the rear surface, with a first spherical mirror and a secondary mirror, which can be flat or spherical. The optical path between the two surfaces of the meniscus allows the control of the spherical aberration, which can be minimised adjusting their curvature radius.

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Three different configurations (A1, A2, A3) were selected, optimising their optical parameters with the aim of reaching the largest enter pupil diameter (EPD) in order to collect the maximum of power. The layouts are depicted in Figures 2, while the optical projects are reported in Figures 3: A1 in (a), A2 in (b), A3 in (c). All optical designs for A, B, C collectors were developed using Zemax ray tracing software.

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Fig. 3...

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Optical design of fibre-coupled collectors

Optical systems for sunlight exploitation have been optically designed and tested in our laboratory since 1997 [12-14, 10]. They are modular devices including solar collectors, optical fibres and mechanical and electronic systems for sun tracking. The main element of the device is the sunlight concentrator coupled to an optical fibre for power transportation to the utilisation point. Our first theoretical studies and practical experimentation of an optical system for sunlight collection were developed for a European project. The selected optical fibres were single fibres made of quartz, which are characterized by extremely reduced losses. The collector was optically designed to be coupled to an optical fibre with core diameter 0.6mm and numerical aperture NA=0.48 (angular semi-aperture 28...

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Internal Lighting by Solar Collectors and Optical Fibres

P. Sansoni, D. Fontani, F. Francini, L. Mercatelli, D. Jafrancesco and E. Sani, D. Ferruzzi

CNR-INO National Institute of Optics, Largo E. Fermi, 6, 50125 Firenze,

Italy

1. Introduction

Sunlight concentration on small surfaces is widely studied [1-3], experimented and mostly applied to photovoltaic power generation [4-6]. More rarely these solar collectors are coupled to optical fibres [7-9], with the advantage of always having a circular absorber shape. On the contrary the photovoltaic (PV) cell is typically squared and therefore it requires a secondary optical system to reshape the image and to improve the light distribution uniformity.

The introduction of optical concentrators, especially high concentration systems, has two positive effects: it reduces the area of expensive solar cells ...

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Solar Collectors and Panels, Theory and Applications

edited by

Reccab M. Ochieng

The title of this book was specifically chosen to encompass all the chapters presented in the book. Solar collectors and panels have become household and industrial items being used for power production, heating, cooling and are even being used for outer space research because of their environmentally friendly nature.

The reason for writing this book was to put together some material which are related in a way and can give those interested in the field of renewable energy a quick start but can also provide detailed information on what is going on in the dynamic area of solar collectors and panels research...

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