INTERNATIONAL JOURNAL OF ENERGY AND ENVIRONMENTAL ENGINEERING
Year:2013 | Volume:4 | Issue:4|Papers Count:12

This paper presents thermodynamic investigation and environmental consideration of combined Stirling-organic Rankine cycle (ORC) power cycle. Combined cycle can be assisted by solar energy and an ORC used as an annular cold-side heat rejector for a free piston Stirling cycle. ORC can increase the power output efficiency by 4% to 8% compared to that of a Stirling standard cycle. Operating temperatures of ORC are between 80°C and 140°C. The main objective of this work is to model the combined cycle for performance optimization in respect to the use of several different working fluids with relevant temperature ranges. Total power efficiency in the range of 34% to 42% was observed for different cases. Several working fluids in the ORC were investigated from a thermal, operational, and environmental point of view. Working fluids considered were FC72, FC87, HFE7100, HFE7000, Novec649, npentane, n-decane, R245fa, and toluene. Practical issues like thermodynamic cycle efficiency, latent heat, density, toxicity, flammability, ozone depletion potential, global warming potential, and atmospheric lifetime are considered. Considering the cycle efficiency, n-decane shows the best performance at both levels of temperature supposed. However, this fluid has the highest saturated vapor specific volume (resulting in a larger condenser) and the lowest condenser saturation pressure (higher infiltration of non-condensable gases). The best candidates for the cycle regarding all the considered aspects were found to be toluene, HFE7100, and n-pentane. Comparing these three fluids, toluene presents the highest efficiency, the highest impact on the environment, the biggest vapor specific volume, and the minimum mass flow rate in Rankine cycle, therefore decreasing the pump power consumption. N-pentane exhibits the lowest cycle efficiency and vapor specific volume, but this fluid has super-atmospheric saturation pressure advantage. HFE7100 is a good working fluid from environmental and safety point of view.

In this study, an attempt has been made to develop a new correlation for the productivity of a single-basin double-slope solar still using experimental results obtained for different brine depths (0.01, 0.02, 0.03, 0.04, 0.05, and 0.06 m) in the basin in Coimbatore, Tamilnadu, India. The proposed correlation has been validated with the experimental results for one of the typical days in Coimbatore, Tamilnadu, India. A concluding correlation has been developed by including the results mentioned in the literature regarding double-slope solar still alone and the proposed correlation. The concluding correlation is compared with the correlation developed by the researcher based on the results in the literature regarding both single- and double-slope solar stills. The results indicate that the correlation coefficient R2 is slightly higher as compared with that of previous results obtained for both single- and double-slope single-basin solar stills.

In this project, a study was made to obtain low cost building materials using industrial wastes (welding and furnace slags). The objective of the study is to use these wastes in low-cost construction with adequate compressive strength. Different fine aggregate replacements have been studied by substituting 5%, 10%, and 15% of slag. The waste material was substituted for replacement of fine aggregates and for the preparation of concrete blocks. In this project, we have followed Indian standard methods and arrived at the mix design for M25 grade concrete. Experimental studies were conducted only on plain cement concrete. The preliminary studies were conducted by mixing the slag with the cement concrete cubes of standard sizes. The building material specimens were analyzed for compressive strength as per IS code. For the test and other specifications, it can be concluded that the welding and furnace slags can increase the strength of the concrete. The optimum compressive strength of concretes after 28 days has been found to be 41 N/mm2 for 5% welding slag and 39.7 N/mm2 for 10% furnace slag replacements. The results show that 5% of welding and 10% furnace slags replacement with sand is very effective for practical purpose.

Technical electricity generation assessment and economic analysis of six wind energy conversion systems in the categories small, medium, and large (with power ratings of 20, 35, 275, 500, 1, 000, and 2, 000 kW) were examined in this study. Electricity cost values were estimated based on the levelized cost of electricity (LCOE) and present value cost (PVC) methods for six locations selected across all the geopolitical zones of Nigeria. This was done using wind speed data that span between 25 and 37 years, measured at the height of 10 m. The result showed that the annual average energy output ranges from 2.242 MW h in Uyo with P10-20 turbine to 12, 521.55 MW h in Kano using Vestas V80-2 MW wind turbine. Furthermore, of all the selected sites, Kano gave the least costs of electricity production per kilowatt hour with Vestas V80-2 MW model at 67-m hub heights, while the highest is obtained in Uyo with GEV-HP (1 MW) model at 70-m hub heights for the LCOE and PVC height for both the LCOE and PVC methods. In addition, sensitivity of the selected parameters to the levelized cost of electricity was also carried out.

Solar collector and concentrator system can be used for industrial process heat application in various industries. Apart from the low temperature applications, there are several potential fields of application for solar thermal energy at medium-high temperatures (80oC to 300oC). This paper describes the experimental results of the prototype parabolic trough made of fiberglass-reinforced plastic with its aperture area coated by aluminum foil with a reflectivity of 0.86. From Indian conditions, there is a large potential available for low-cost solar-concentrating technologies for domestic as well as industrial process heat applications. This line-focusing parabolic trough with mild steel receiver coated with black proxy material has been tested with and without glass cover. Instantaneous efficiency of 51% and 39% has been achieved with and without glass cover, respectively. Performance evaluation of the prototype system has been done during the months of April and May 2010 at Shivaji University, Kolhapur (16.42oN latitude, 74.13oW longitude). The total cost of the prototype system developed has been calculated as Rs10, 000 (US$200).

Penetration of distributed generation (DG) units in distribution network has increased rapidly stimulated by reduced network power loss, improved bus voltage profile, and better power quality. Appropriate size and allocation of DG units play a significant role to get beneficial effects. The objective of this study is to demonstrate a simple and fast technique to determine appropriate location and size of DG units. A voltage stability indicator (VSI) is derived which can quantify the voltage stability conditions of buses in distribution network. According to VSI, vulnerable buses of the network are arranged rank-wise to form a priority list for allocation of DG units. To determine the size of DG units, a feed forward artificial neural network is prepared in MATLAB environment (The MathWorks, Inc., Massachusetts, USA). The effectiveness of the proposed methodology has been tested on a 52-bus radial distribution network. After appropriate allocation of DG units, voltage profiles of most of the buses are increased significantly. The results also indicated that the total loss of the distribution network has reduced by nearly 76.39%, and voltage stability conditions of buses are improved considerably. Voltage stability conditions of bus-13, bus-36, and bus-44 are raised by 23.16%, 29.23%, and 37.64% respectively.

The sugarcane agro-industry is seen as a great opportunity for economic and industrial development in many sugarcane-producing countries. Important changes happening in recent decades have converted the sugar mill from being just a food producer into a diversified production factory. The sugar mill has become a multipurpose factory since it produces food, energy, and biofuels at present. The key cause of this change is the use of sugarcane agro-industrial residues as feedstock for energy cogeneration and biofuel production.The main aim of this paper is to carry out an assessment on sugarcane feedstock availability and its energy use in the sugar mill. The trade-off on sugarcane bagasse energy use (electricity cogeneration vs. bioethanol production), considering the agro-industrial development level, is analyzed in this work, too. The better options in each case are highlighted. The main environmental and techno-economic aspects concerning the sugarcane agro-industry were taken into account during the assessment process. The most promising trends of the sugarcane agro-industry and the barriers to overcome in its implementation are pointed out.

Statistical approach was employed to optimize biodiesel production from sesame oil in this work. Precisely, response surface methodology was applied, and the effects of four variables, viz. reaction temperature, catalyst amount, reaction time, and methanol/oil molar ratio, and their reciprocal interactions were determined. Central composite rotatable design was used to generate a total of 30 individual experiments, which were designed to study the effects of these variables during alkali-catalyzed methanolysis of sesame oil. A statistical model predicted the highest conversion yield of sesame biodiesel to be 99.71% at the following optimized variable conditions: reaction temperature of 63oC, catalyst amount of 1.04 wt.%, and methanol/oil molar ratio of 6.24, with a reaction time of 51.09 min. Using these variables under experimental condition in four independent replicates, an actual biodiesel yield of 98.36% was accomplished. The fuel properties of biodiesel produced were found to be within the ASTM D6751 and DIN EN 14214 biodiesel specifications.

This study is aimed to evaluate and compare environmental impacts of various food waste management systems: anaerobic digestion, co-digestion with sewage sludge, and volume reduction using a garbage dryer followed by incineration from generation to final disposal. An environmental credit using life cycle assessment was employed to compare by-products. The entire disposal process, namely discharge, collection, transportation, treatment, and final disposal, was included in the system boundary. The functional unit was 1 tonne of food waste from households for each treatment option. Global warming potential of the category indicator was selected to assess the environmental impact of food waste disposal options. The net global warming potential (environmental credit) of the options (wet based) was 33 kg of carbon dioxide equivalent (CO2-eq) for anaerobic digestion and -315 kg of CO2-eq for incineration by renewable energy production as electricity, thermal energy, and primary materials avoided. We found that dryer-incineration option was an available alternative for food waste recycling in a metropolitan area in Korea.

A 10.3-kW single-cylinder water-cooled direct-injection diesel engine was evaluated using blends of biodiesel (B10 and B20) obtained from a mixture of mahua and simarouba oils (50: 50) with high-speed diesel (HSD) in terms of brake specific fuel consumption, brake thermal efficiency, and exhaust gas temperature and emissions such as CO, HC, and NOx. Based on performance and emissions, blend B10 was selected for long-term use. Experiments were also conducted to assess soot deposits on engine components, such as cylinder head, piston crown, and fuel injector tip, and addition of wear metal in the lubricating oil of diesel engine when operated with the biodiesel blend (B10) for 100 h. The amount of soot deposits on the engine components was found to be, on average, 21% lesser for B10-fueled engine as compared with HSD-fueled engine due to better combustion. The addition of wear metals such as copper, zinc, iron, nickel, lead, magnesium, and aluminum, except for manganese, in the lubricating oil of B10-fueled engine after 100 h of engine operation was found to be 11% to 50% lesser than those of the HSD-fueled engine due to additional lubricity.

Experimental studies are carried out on a semiclathrate hydrate system of carbon dioxide in tetra-n-butylammonium bromide (TBAB) with a small amount of surfactant, sodium dodecyl sulfate (SDS), for 5, 10, and 20 wt.% TBAB to determine the phase equilibrium temperature and pressure conditions. It is observed that the presence of SDS did not influence the equilibrium conditions of the semiclathrate hydrate. Re-nucleation (memory) effect of semiclathrate hydrates of CO2 is studied for few cases of TBAB concentration in an aqueous solution. The equilibrium pressure and temperature conditions obtained for memory effect and regular experimental run without memory effect were observed to be quite close. It is concluded that in the case of no memory effect, with increasing TBAB percentage in the system, the time required for nucleation is reduced. For the same TBAB concentration, the incipient pressure and temperature required for nucleation and re-nucleation of semiclathrate hydrates increase while the time required for re-nucleation decreases.

Oil dependency and global warming have stimulated R& D activities on the utilization of secondary biofuels. This article investigates the suitability of coconut shell-derived producer gas (a secondary gaseous biofuel) as a substitute for coal gas from an environmental perspective using life cycle assessment (LCA) approach. Thermochemical gasification in an air-fluidized bed with steam injection is the gaseous fuel production process. LCA is carried out with respect to Indian conditions based on primary and modified Ecoinvent 2.0 data using IMPACT 2002+environmental impact assessment methodology. The study indicates that coconut shell-derived producer gas life cycle is capable of saving 18.3% of emissions causing global warming potential, 64.1% of emissions causing ozone depletion potential, and 71.5% of nonrenewable energy consumption. The analysis of energy and exergy consumptions of the two life cycles reveal that the renewable fraction in the total energy demand is 62.9% for producer gas life cycle, while it is only 2.8% for coal gas life cycle. Allocation of the by-product, coconut palm residues, is the major responsible factor for this reduction in environmental burden. Based on the existing fertilization practice and the utilization of electricity from the Indian electric grid, substantial green house gas (GHG) emission savings cannot be achieved for producer gas life cycle over coal gas life cycle. However, the green electricity-aided catalytic gasification of coconut shell produced by organic farming can result in 43.4% reduction in GHG emissions, meeting European Union renewable energy directive.