Solar Energy

CHAPTER ONE


1.0INTRODUCTION



solar devices thus involve electronic devices which be strung-out on the sun or its rays or any contour of light for its operation. They ar mostly referred to as photosensitive devices. Solar devices in this group comprises photosensitive semiconductor device devices in which the deed of visible rays infra-red rays or ultra-violet rays causes variations in resistivity or generates an electromotive hale by the internal photoelectric effect.
The main types of photosensitive semiconductor devices are :
(a) Photoconductive cells (light dependent resistors) commonly consisting of two electrodes among which is a semiconductor substance (cadmium sulphide lead sulphide etc.) whose electrical resistance varies with the intensity of illumination falling on the cell.
These cells are used in flame detectors in depiction meters for automatic cameras for counting moving objects for automatic precision measuring rod devices in automatic door opening systems etc.
(b) Photovoltaic cells which transform light directly into electrical energy without the need for an away source of current. Photovoltaic cells based on selenium are used mainly in luxmeters and exposure meters.



Those based on silicon have a higher output and are used in particular in control and regulating equipment for detecting light impulses in communication systems using role optics etc.
Special categories of photovoltaic cells are:
(i) Solar cells silicon photovoltaic cells which convert sunlight directly into electric energy. They are usually used in groups as sources of electric power e.g. in rockets or satellites employed in space research for set rescue transmitters.
(ii) Photodiodes (germanium silicon etc.) characterised by a variation in resistivity when light rays strike their p n junction. They are used in automatic data processing (reading of punched tease and tapes data storage) as photo cathodes in certain electronic tubes in radiation pyrometers etc. Phototransistors and...If you want to get a full essay, order it on our website: Ordercustompaper.com



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