akash+ganapathi

Due: 3/12/009 Journal Summary


 * Hydrogen Production from Biogas using Hot Slag **

Slag is the molten run-off from steel mills as a result of smelting ores. The molten metal oxide flow is now being looked into as a possible source of energy to obtain hydrogen from biogases like methane. The study consisted of observing the decomposition rate of CO2-CH4 in a packed bed of granulated slag at a constant flow and temperature. The temperature is over 1700K when discharged from steelmaking industries or municipal waste incinerators, however this heat is not retained and the experiments were undertaken between 973K and 1273K. In the experiments a mixture of CO2 and CH4 gasses were introduced into the slag and the outlet gasses were monitored by gas chromatography. The study found that the slag acted not only as a thermal media but also as a good catalyst for hydrogen production. The product gasses were mainly hydrogen and carbon monoxide and depending on the temperature of the slag there was also a layer of solid carbon deposition on the surface of the slag. Higher temperatures of slag resulted in greater hydrogen generation and less un-reacted methane in the outlet gas. The study managed to achieve a maximum of 96% methane conversion. These results suggest a new energy efficient and cost effective process of hydrogen production because the heat from the slag which is normally not utilized can now be used to replace the energy needed for hydrogen production. This could be very useful for the potential hydrogen fuel cell economy.

Purwanto, H. and Akiyama T. "Hydrogen Production from Biogas Using Hot Slag." __Fuel and Energy Abstracts__ 47.5 Sep 2006 352. 12 Mar 2009 .

Due: 3/13/09 Journal Summary


 * The Performance of Silicon Solar Cells Operated in Liquids **

Silicon solar cells are a photovoltaic system used to collect solar energy from the sun. In this experiment, performed in China, it was found that better performance can be achieved when the bare silicon solar cells were immersed into liquids. By immersing the cells in the liquid the heat removing properties were enhanced. A control was used in the experiment which was not immersed in any liquid and simulated sunlight was used. It was found that the optic properties held by the liquids can cause minor efficiency changes on the solar cells while the electrical properties are responsible for the majority of changes (molecular polarity and ions, etc.). The goal of the experiment was to find a liquid that could be used to create a CPV (concentrated photovoltaic system usually created by lenses and mirrors) which had good heat transfer performance, the same spectral absorption of sunlight as the solar cells, was non-toxic and had good chemical stability (because the liquid would be heated), and which was also economic. Six liquids were chosen that could possibly fit this bill, ethanol and glycerin (polar), benzene and silicon oil (non-polar), and the inorganic distilled water and tap water. The results of the experiment showed that the bare solar cells immersed in the non-polar silicon oil had the best performance. An accelerated life test was carried out at 150o Celsius under an intensity of 200 W/m2 ultraviolet light irradiation. They found that the silicon oil had good stability in addition to assisting increase the efficiency of the solar cells. The silicon oil was able to provide an increase of 18.25% efficiency in the solar cells (from what I understood). This is comparable to the increase achieved by lenses and mirrors; however, lenses and mirrors require far more maintenance and are more expensive. Tap water actually had a greater increase of 24.47% (because of the electrolytes added to it), but tap water is not even close to as stable as the silicon oil as it evaporates. This would be seen as an immense and unnecessary waste of drinking water I assume. Perhaps it would be good to look at sea water then? Combine salt collection with water purification while obtaining energy? Of course this may require a lot of man power and/or money I don’t know.

Wang, Yiping and Fang, Zhenlei and Zhu, Li and Huang, Qunwu and Zhang, Yan and Zhang, Zhiying. "The Performance of Silicon Solar Cells Operated in Liquids." __Applied Energy__ 86.7-8(2009) 1037-1042. 12 Mar 2009 .

Due: 3/20/09 Journal Summary


 * The Efficiency of Solar Cells Immersed in Liquid Dielectrics **

As a follow up to my previous journal summary I continued to look for research being done on creating CPVs (concentrated photovoltaic cells) through liquid immersion. This study, performed by a group of Armenian scientists looks at the efficiency of solar cells when immersed in liquid dielectrics. (Dielectrics are non-conducting liquids.) Under conditions of non-concentrated, ordinary, sunlight, efficiencies have been obtained from silicon solar cells that are around 22.7%. The dielectrics that were tested include glycerin, isopropyl alcohol, acetone, butanol, dioxane, toluol and deionized water. The data was collected by placing the solar cell in a pan and then submitting it to an artificial source of sunlight at a known intensity. Then this same process was repeated with the added liquid they wished to test. This study found that the presence of a thin dielectric film, specifically glycerin and acetone, results in an increase of 40%-60% from the reference value. (I am assuming that the reference value is what the solar cell was able to attain ordinarily.) Thus for a common large scale produced solar cell, the efficiency would rise from 8% to 13.7%-14%.

Abrahamyan, Yu. "The efficiency of solar cells immersed in liquid dielectrics ." __Solar Energy Materials and Solar Cells__ 73.4 Aug 2002 367-375. 19 Mar 2009 .