Thermodynamic comparison and dynamic simulation of direct and indirect solar organic Rankine cycle systems with PCM storage

A thermodynamic comparison between a novel direct solar ORC system (DSOS) and indirect solar ORC system (ISOS) is carried out in this study. A phase change material (PCM) heat storage unit is integrated with both systems to ensure the stability of power generation. Water and R245fa are selected as a heat transfer fluids (HTFs) for ISOS and DSOS respectively. However, R245fa is used as working fluid for both systems. Weekly, monthly and annual dynamic simulations are carried out to compare the performance of both systems using hourly weather data of Islamabad, Pakistan. ISOS has shown 1.71% system efficiency and able to provide 34.02 kW/day power while DSOS has shown 4.5 times higher system efficiency and 2.8 times higher power on annual basis. Numerical model for the PCM storage is developed and validated with the previous experimental data. Average annual amount of energy stored by PCM during charging phase for ISOS is 4.24 MW/day higher than DSOS. However, in comparison with ISOS, DSOS has delivered 33.80 kW/day more power to HTF during discharging phase of the PCM on annual basis. Maximum benefits of PCM storage are observed during the summer season compared to the winter season at selected operating conditions. Furthermore, average annual increment in capacity factor by using PCM storage are found to be 21.71% and 17% for DSOS and ISOS respectively

Effect of Phase Change Material Storage on the Dynamic Performance of a Direct Vapor Generation Solar Organic Rankine Cycle System

Solar energy is a potential source for a thermal power generation system. A direct vapor generation solar organic Rankine cycle system using phase change material storage was analyzed in the present study. The overall system consisted of an arrangement of evacuated flat plate collectors, a phase-change-material-based thermal storage tank, a turbine, a water-cooled condenser, and an organic fluid pump. The MATLAB programming environment was used to develop the thermodynamic model of the whole system. The thermal storage tank was modeled using the finite difference method and the results were validated against experimental work carried out in the past. The hourly weather data of Karachi, Pakistan, was used to carry out the dynamic simulation of the system on a weekly, monthly, and annual basis. The impact of phase change material storage on the enhancement of the overall system performance during the charging and discharging modes was also evaluated. The annual organic Rankine cycle efficiency, system efficiency, and net power output were observed to be 12.16%, 9.38%, and 26.8 kW, respectively. The spring and autumn seasons showed better performance of the phase change material storage system compared to the summer and winter seasons. The rise in working fluid temperature, the fall in phase change material temperature, and the amount of heat stored by the thermal storage were found to be at a maximum in September, while their values became a minimum in February

Air quality in Mecca and surrounding holy places in Saudi Arabia during Hajj: initial survey.

The Arabian Peninsula experiences severe air pollution, the extent and sources of which are poorly documented. Each year in Saudi Arabia this situation is intensified during Hajj, the Holy Pilgrimage of Islam that draws millions of pilgrims to Mecca. An initial study of air quality in Mecca and surrounding holy sites during the 2012 Hajj (October 24-27) revealed strongly elevated levels of the combustion tracer carbon monoxide (CO, up to 57 ppmv) and volatile organic compounds (VOCs) along the pilgrimage route-especially in the tunnels of Mecca-that are a concern for human health. The most abundant VOC was the gasoline evaporation tracer i-pentane, which exceeded 1200 ppbv in the tunnels. Even though VOC concentrations were generally lower during a follow-up non-Hajj sampling period (April 2013), many were still comparable to other large cities suffering from poor air quality. Major VOC sources during the 2012 Hajj study included vehicular exhaust, gasoline evaporation, liquefied petroleum gas, and air conditioners. Of the measured compounds, reactive alkenes and CO showed the strongest potential to form ground-level ozone. Because the number of pilgrims is expected to increase in the future, we present emission reduction strategies to target both combustive and evaporative fossil fuel sources

Modelling, simulation and comparison of phase change material storage based direct and indirect solar organic Rankine cycle systems

The thermodynamic performance of a novel direct solar organic Rankine cycle system and conventional indirect solar organic Rankine cycle system is compared in this study. The working fluid is vaporized directly in the solar collectors in direct solar organic Rankine cycle system while heat transfer fluid is used to vaporize the working in indirect solar organic Rankine cycle system. The evacuated flat plate collectors array covering a total aperture area of 150 m2 is employed as a heat source and a phase change material tank having a surface area of 25.82 m2 is used as thermal storage for both configurations. R245fa and water are chosen as heat transfer fluids for direct and indirect solar organic Rankine cycle systems, respectively. However, R245fa is used as a working fluid for both configurations. The performance of both configurations is compared by carrying out weekly, monthly and annual dynamic simulations in MATLAB by using hourly weather data of Islamabad, Pakistan. The direct solar organic Rankine cycle system outperforms the indirect solar organic Rankine cycle system in terms of thermal efficiency and net power. The annual system efficiency and an annual average net power of the direct solar organic Rankine cycle system are 71.96% and 64.38% higher than indirect solar organic Rankine cycle system respectively. However, average annual heat stored by phase change material during charging mode of indirect solar organic Rankine cycle system is 4.24 MJ more than direct solar organic Rankine cycle system. Conversely, direct solar organic Rankine cycle system has provided annual daily average power of 33.80 kW extra to heat transfer fluid during the discharging mode of phase change material storage. Furthermore, with phase change material storage, the capacity factor is increased by 17 % and 21.71 % on annual basis for direct and indirect solar organic Rankine cycle systems, respectively

Characterization of carbon monoxide, methane and nonmethane hydrocarbons in emerging cities of Saudi Arabia and Pakistan and in Singapore

We investigate the composition of 63 C2-C10 nonmethane hydrocarbons (NMHCs), methane (CH4) and carbon monoxide (CO), in Jeddah, Mecca, and Madina (Saudi Arabia), in Lahore, (Pakistan), and in Singapore. We established a database with which to compare and contrast NMHCs in regions where ambient levels and emissions are poorly characterized, but where conditions are favorable to the formation of tropospheric ozone, and where measurements are essential for improving emission inventories and modeling. This dataset will also serve as a base for further analysis of air pollution in Western Saudi Arabia including, but not limited to, the estimation of urban emissions and long range pollution transport from these regions. The measured species showed enhanced levels in all Saudi Arabian cities compared to the local background but were generally much lower than in Lahore. In Madina, vehicle exhaust was the dominant NMHC source, as indicated by enhanced levels of combustion products and by the good correlation between NMHCs and CO, while in Jeddah and Mecca a combination of sources needs to be considered. Very high NMHC levels were measured in Lahore, and elevated levels of CH4 in Lahore were attributed to natural gas. When we compared our results with 2010 emissions from the MACCity global inventory, we found discrepancies in the relative contribution of NMHCs between the measurements and the inventory. In all cities, alkenes (especially ethene and propene) dominated the hydroxyl radical (OH) reactivity (kOH) because of their great abundance and their relatively fast reaction rates with OH

Effects of Low Molecular Weight and Unfractionated Heparin on Lipoprotein Lipase and Lipid Profile in haemodialysis patients

Introduction: In haemodialysis patients, mortality from cardiovascular disease is much greater than in the general population. The current study aimed to evaluate the effects of two different types of heparin, low molecular weight heparins (LMWH) and high molecular weight heparin (HMWH), on lipid profile in patients undergoing haemodialysis. Material & Methods: A total of 60 patients on haemodialysis were selected from two main hospitals of Lahore, Pakistan and were divided into two major groups based on the type of heparin used. A 5 ml blood sample was taken from the dialysis machine to get the serum and was kept frozen at -20ºC for analysis of total cholesterol, triglycerides, high-density lipoprotein, and low-density lipoprotein. Comparison of lipoprotein lipase activity between groups were evaluated by using the student t-test. A P-value of ? 0.05 was considered statistically significant. Results: Gender wise distribution of study population (n=60) was 67% (n=40) males and 33% (n=20) females. The age distribution of individuals varied from 39-43 years. Moreover, use of HMWH was high in males (73%) as compared to female (27%) with an average age of 39 ± 12 years where duration of haemodialysis was 4.44 ± 2.83. A significant difference in LPL activity related to different times in all patients was observed. A clearer difference observed in case of LDL where LPL activity was markedly different in both groups. Our data showed that individuals using LMWH had less chances of dyslipidaemia as compared to those using HMWH. Conclusion: LMWH is a useful and safe anticoagulant during haemodialysis as compared to HMWH

Rational Design and Advance Applications of Transition Metal Oxides

An attractive class of transition metal oxides (TMOs) have been freshly concerned with increasing research interest worldwide concerning stoichiometric and non-stoichiometric configurations as well, that usually exhibits a spinel structure. These TMOs will contribute substantial roles in the production of eco-friendly and low-cost energy conversion (storage) devices owing to their outstanding electrochemical properties. The current chapter involves the summary of the latest research and fundamental advances in the effectual synthesis and rational design of TMOs nanostructures with meticulous size, composition, shape, and micro as well as nanostructures. Also applications of TMOs such as effective photocatalyst, gas sensing, biomedical, and as an electrode material that can be utilized for lithium-ion batteries, and photovoltaic applications. Additionally, certain future tendencies and visions for the development of next-generation advanced TMOs for electrochemical energy storage methods are also displayed

Effect of Ajwa date pits powder (Phoenix dactylifera L.) on body composition, lipid profile and blood pressure in patients with hyperlipidemia: A randomized clinical trial

Objective: To evaluate the effect of Ajwa dates pit powder (ADP) on lipid profile, body composition and blood pressure in patients with hyperlipidemia.Materials and Methods: This randomized controlled clinical study was carried out on 40 patients with total cholesterol >200 mg/dl, triglycerides >150 mg/dl and BMI >25, of either sex, aged 30-50 years, who were recruited through written consent. The patients were divided into two groups (n=20 each): the ADP and the control group (CG). All patients received the doctor’s prescribed class A statin (Rosuvastatin/ Atorvastatin) 10 mg/day, while 2.7 g ADP was given on daily basis before breakfast with lukewarm water for 40 days and the control group received the same amount of wheat flour. Body composition, blood pressure and lipid profile were determined at baseline, and after 20 and 40 days. Data were analyzed by using SPSS and GraphPad Prism.Results: ADP significantly reduced body weight (p<0.001), BMI (p<0.001), fat mass, body fat percentage, visceral fat area and waist circumference compared to the control group. Similarly, ADP significantly (p=0.000) decreased the serum level of total cholesterol and low-density lipoprotein. Conclusion: ADP may have the potential to improve dyslipidemia and obesity