[en] Technologies for fossil fuel extraction, transportation, processing and their use have harmful impact on the environment which cause direct and indirect negative impact on human heath, animals, crops and structure etc. The end use of all the fossil fuels is combustion irrespective of the final purpose i.e. heating, electricity production and motive power for transportation. The main constituents of fossil fuels are carbon and hydrogen but some other ingredients, which are originally in the fuel e.g. sulfur or are added during refining e.g. lead, alcohol etc. Combustion of the fossil fuel produces various gases (CO/sub x/, SO/sub x/ NO/sub x/, CH,), soot, ash, droplets of tar and other organic compounds, which are all released into the atmosphere. High rate of population growth and industrialization in the developing countries are causing unsustainable use of forest resources and fossil fuels, hence, are serious hurdles in environmental improvement. The situation in Pakistan is even worse as it has very limited fossil fuels and 40% of its commercial energy requirement are to be imported every year. Renewable energy technologies on the other hand, can play a vital role in improving the environmental condition globally. Pakistan Council of Renewable Energy Technologies (PCRET) is working in the field of renewable energy technologies. The Council has developed solar modules and solar thermal devices including solar cookers, solar dryers, solar stills and solar water heaters. The paper describes these devices and contribution they can make towards the improvement of environment. (author)

[en] Short communication

[en] Quartz is used for extraction of silicon and also for making crucibles as heating pot to melt high temperature semiconductors during crystal growth. Quartz crucible purity is of great concern for crystals grown by Czochralski technique (CZ). During growth, impurities critical from semiconductor point of view are incorporated into the from of crucible and degrade the quality of the crystal. The impurities in quartz crucible used for growing single crystal at NIST are determined by using atomic absorption spectroscopy. (author) 5 figs

[en] Most of the approaches to fabricate photovoltaic cells, relay on silicon because the solar cell made from silicon have proved to be reliable both for space and terrestrial purposes. Oxygen and carbon are undoped impurities which are incorporated in the crystal during the Czochralski growth process. Infrared spectroscopy is a well established method for the measurement of oxygen and carbon impurities in silicon. Fourier Transform Infrared Spectrometer 1710 is used to measure the oxygen and carbon concentration in silicon wafers. The effect of oxygen and carbon impurities on the performance parameters such as Short circuit current density (Jsc), Open circuit voltage (Voc), efficiency (LAMBDA) and power density at maximum power point (pm) have been studies. (author)

[en] Silicon material due to its abundance in nature and maximum conversion efficiency has been successfully being used for the fabrication of electronic and photovoltaic devices such as ICs, diodes, transistors and solar cells. The 80% of the semiconductor industry is ruled by silicon material. Single crystal silicon solar cells are in use for both space and terrestrial application, due to the well developed technology and better efficiency than polycrystalline and amorphous silicon solar cells. The current research work is an attempt to reduce the cost of single crystal silicon solar cells by reusing the silicon saw dust obtained during the watering process. During the watering process about 45% Si material is wasted in the form of Si powder dust. Various waste powder silicon samples were analyzed using inductively Coupled Plasma (ICP) technique, for metallic impurities critical for solar grade silicon material. The results were evaluated from impurity and cost point of view. (author)

[en] Silicon material due to its abundance in nature and maximum conversion efficiency, has a vide range of application in opto-electronic and photovoltaic devices, such as ICs, thin film transistors and solar cells. The cost of the solar cells is the main hindrance in competing solar energy with other form of energy resources. The production of Si material using locally available indigenous silicon ores will reduce the cost silicon solar cells and will help to promote solar energy applications in the country. Silicon ores, Quartz and Sand, were collected from various parts of the country and analyzed. The purification processes of Silicon to produce high purity silicon are discussed. The cost comparison of locally produced and imported silicon material shows that 15% to 20% cheaper material can be produced locally. In order to reduce the cost further, the silicon saw dust wasted during wafering process are analyzed. The undesirable impurities from silicon saw dust can be removed. The reusing of sawdust will produce 10% cheaper silicon solar cells. (author)