Abstract
After being adequately captured and concentrated, solar radiation can be conducted by optical fiber bundles/cables and directly used for illumination (lighting) or heating of confined spaces, or indirectly used by converting it in other forms of energy (e.g., for producing electricity). This article reports preliminary tests conducted on a 7-m-long optical fiber bundle/cable with an effective aperture circular area of 14 mm in diameter, specially designed and manufactured by a leading company to transmit up to 1000 Wth of unfiltered concentrated sunlight. The cable was tested in the typical receiver position at the top of a solar concentration central tower. The main purpose was the experimental determination of the transmission efficiency of the cable in function of the incidence angle using selected groups of heliostats belonging to the heliostat field. The testing methodology proved to be capable of evaluating the performance of the cable. The cable withstood the tests without revealing any type of damage. The results obtained showed that the transmissivity of the cable is higher than 50% when the incidence angle of the solar radiation is lower than 14.7°, increasing sharply to circa 95% when the incidence angle is lower than 4.5°.
Highlights
direct normal irradiance (DNI) values may have changed during the irradiation tests, but that did not affect the attainment of the objective of this work: the determination of the efficiency of the cable transmission
The protection system or thermal shielding put in place to avoid the concentrated radiation heating up the non-optical parts of the cable proved to be adequate
Facility proved to be suitable to determine the efficiency of the optical fiber decreasing from n = 1.0002736 at 15 C to n = 1.0001959 at 100 C
Summary
As important contributors to limit CO2 emissions in industrial or domestic activities, solar technologies can be developed for a variety of uses [1,2]. The first category refers to photovoltaics (PV), and the second includes low-temperature solar thermal (i.e., solar heating and cooling, SHC) and medium and high-temperature solar thermal (i.e., concentrating solar power (CSP)). CSP uses optical systems to concentrate solar light and leads to applications such as electricity generation, solar thermochemistry, and industrial process heat. Considering the classification used for solar heat for industrial processes (SHIP) [3], low temperature SHIP are in the range of 80–150 ◦ C; medium temperature SHIP cover the 150–400 ◦ C range; and high temperature SHIP are considered to cover the 400–1500 ◦ C range
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