Hydrogen storage in aromatic carbon ring based molecular materials decorated with alkali or alkali-earth metals

On the basis of first-principles calculations of molecular electron structure, we discuss the strategy of modifying the carbon-based materials in order to increase their capacity to bind with molecular hydrogen. In particular, we have studied hydrogen adsorption on molecular complexes having anionic aromatic carbon-based rings stabilized by cations of alkali (Li+, Na+, K+) or alkali-earth metals (Be2+, Mg2+, Ca2+). The adsorption depends more on the properties of the cation than on the ring itself. The interaction of the H2 molecule with an electrostatic field leads to the binding of the hydrogen molecule with the strongly polarized ionic molecular complex. The number of the adsorbed molecules is driven by two factors acting in opposite directions: the binding energy, which should be larger than a 4–5 kJ/mol threshold needed to keep hydrogen molecules attached, and the area around the cation (coordination sphere), which is determined by its radius. As a compromise between these factors, we propose several promising candidates for building blocks of hydrogen storage materials, including diboratabenzene lithium, C4B2H6Li2, and diboratabenzene potassium, C4B2H6K2, which can adsorb 6 and 12 H2 molecules, correspondingly. We also discuss the possibility of linking these molecular complexes in three-dimensional structures.http://dx.doi.org/10.1021/jp305324phttp://pubs.acs.org/doi/pdf/10.1021/jp305324phttp://pubs.acs.org/doi/pdf/10.1021/jp305324

Exergetic Analysis of Cogeneration Energy Sources

В данной статье рассмотрен метод теплового и эксергетического анализа работы когенерационных энергоисточников на примере газотурбинной установки LM6000PF (ГТУ-ТЭЦ «Восточная»). Целью проведенного эксергетического анализа служит определение наиболее выгодного с точки зрения термодинамической эффективности способа оценки работы оборудования. Выполнено сравнение величин КПД ГТУ, полученных расчетным путем по методикам теплового и эксергетического анализа. Особенностью проведения эксергетического анализа является использование помимо энергии дополнительного показателя – эксергии. В ходе проведения эксергетического анализа оценивается эффективность использования энергии сжигаемого в камере сгорания ГТУ топлива и рабочих тел газового цикла для производства электрической и тепловой энергии путем сравнения фактически совершенной работы с эксергией процессаThis article discusses the method of thermal and exergetic analysis of cogeneration energy sources on the example of the gas turbine unit LM6000PF (GTU-CHPP «Vostochnaya»). The purpose of the conducted exergetic analysis is to determine the most advantageous method for evaluating the performance of equipment in terms of thermodynamic efficiency. The comparison of GTU efficiency values obtained by calculation using the methods of thermal and exergetic analysis is performed. A special feature of the exergetic analysis is the use of an additional indicator as exergy along with energy indicator. In the analysis, the efficiency of using the energy of the fuel burned in the GTU combustion chamber and the working bodies of the gas cycle for the production of electrical and thermal energy is assessed by comparing the actually accomplished work with the exergy of the proces