INTERNATIONAL JOURNAL OF ENERGY AND ENVIRONMENTAL ENGINEERING
Year:2015 | Volume:6 | Issue:3|Papers Count:10

Uncertain renewable energy supplies, load demands and the non-linear characteristics of some components of photovoltaic (PV) systems make the design problem not easy to solve by classical optimization methods, especially when relevant meteorological data are not available. To overcome this situation, modern methods based on artificial intelligence techniques have been developed for sizing PV systems. However, simple methods like worst month method are still largely used in sizing simple PV systems. In the present study, a method for sizing remote PV systems based on genetic algorithms has been compared with two classical methods, worst month method and loss of power supply probability (LPSP) method. The three methods have been applied to a PV lighting system with orientation due south and inclination angles between 0o and 90o in Adrar city (south Algeria). Because measured data for the chosen location were not available, a year of synthetic hourly meteorological data of this location, generated by PVSYST software, have been used in the simulation. Genetic algorithms and worst month methods give results close to each other between 0o and 60o but the system is largely oversized by the worst month method when the tilted angle is over 60o. The results obtained by LPSP method show that the system is very undersized. Hence, a proposition has been made to improve results obtained by this method.

Microbial fuel cell (MFC) technology represents a form of renewable energy that generates bioelectricity from what would otherwise be considered a waste stream. MFCs may be ideally suited to the small island developing state (SIDS) context, such as Trinidad and Tobago where seawater as the main electrolyte is readily available, and economically renewable and sustainable electricity is also deemed a priority. Hence this project tested two identical laboratory-scaled MFC systems that were specifically designed and developed for the Caribbean regional context. They consisted of two separate chambers: an anaerobic anodic chamber inoculated with wastewater and an aerobic cathodic chamber separated by a proton exchange membrane. Domestic wastewater from two various wastewater treatment plants inflow (after screening) was placed into the anodic chamber, and seawater from the Atlantic Ocean and Gulf of Paria placed into the cathodic chambers, respectively, with the bacteria present in the wastewater attached to the anode. Experimental results demonstrated that the bacterial degradation of the wastewaters as substrate induced an electron flow through the electrodes producing bioelectricity whilst simultaneously reducing the organic matter as biochemical oxygen demand and chemical oxygen demand by 30 to 75%. The average bioenergy output for both systems was 84 and 96 mW/m2, respectively. This study demonstrated the potential for simultaneous bioenergy production and wastewater treatment in the SIDS context.

Ways to produce metallic nanoparticles and the scale-up of these processes have seen increased interest as the industrial application of nanoparticles continues to grow. Their feasibility from an environmental point of view can be assessed by means of life cycle analysis (LCA). In this work two methods of metallic nanoparticle production, by evaporation/condensation of metal using electrical arc discharge reactors or by chemical reduction of metal salts in aqueous solutions or dry solid/solid mixtures, are evaluated based on the life cycle indicators. The evaporation of metal using electrical discharge reactors is a method studied in the European Commission 7th Framework Program ‘‘BUONAPART-E.’’ The environmental impact of the two different nanoparticle production approaches is here compared for four metals: copper, silver, zinc and aluminum. The chemical routes of producing nanoparticles require several different chemicals and reactions, while the electrical discharge routes use electricity to evaporate metal in a reactor under inert atmosphere. The nanoparticle production processes were modeled using ‘‘SimaPro’’ LCA software. Data for both the chemical production routes and the arc routes were taken from the literature. The choice of the best route for the production of each metal is strongly dependent on the final yield of the metallic nanoparticles. The yields for the chemical processes are not reported in the open literature, and therefore the comparisons have to be made with varying yields. At similar yields the electrical process has in general a lower environmental footprint than the studied chemical routes. The step or chemical with the greatest environmental impact varies significantly depending on process and metal being studied.

The paper studies the possibility of unifying the two branches of the irreversible engineering thermodynamics, namely finite physical dimensions thermodynamics (FPDT) and finite speed thermodynamics (FST), aiming to take into account their benefits and successes and to eliminate as much as possible their disadvantages. Actually, the two branches have the same goal, that of optimizing the performance of thermal machines and they were developed almost in parallel. Analysis of thermal machines cycles using the FPDT is based on the first and second law of thermodynamics, in the presence of the external irreversibility generated by the heat transfer at finite temperature difference at the thermal reservoirs and internal irreversibility, using the internal source of entropy considered as parameter or function to be specified. The FST is based on the mathematical expression of the first law for process with finite speed that involves three causes of internal irreversibility, namely the finite speed of the piston, internal friction and throttling. The direct method is used in the analysis of thermal machines cycles to provide analytical expression of the machine performance (efficiency and power) as a function of the speed of the process. The significant progress of these two branches of irreversible engineering thermodynamics makes their unification a desirable outcome. We hope that the new model yielded from this study will provide an even more important tool for engineers that will help their attempt to a better design and optimization of thermal machines.

Concerning the global warming due to large CO2 emission, the efficient use of coal becomes important for getting sustainable energy production. Coal gasification under CO2-rich condition is expected to be an effective way to produce a concentrated and pressurized carbon dioxide stream, resulting in reduction in separation energy of CO2 for CCS. Moreover, the soot formation, which is of significant environmental concern, is still being neglected in the past studies of coal gasification. A one-step soot formation reaction mechanism is proposed in this study and implemented in numerical simulations of coal gasification with the aim of describing the gasification behaviors in a two-stage entrained-flow gasifier. In addition, the effects of O2 ratio and CO2 concentration on soot concentration, syngas heating value and carbon conversion are numerically studied in an effort to increase the syngas production. The Eulerian–Lagrangian approach is applied to solve the Navier–Stokes equation and the particle dynamics. Finite rate/eddy dissipation model is used to calculate the rate of nine homogeneous gas-to-gas phase reactions including soot formation and soot oxidation. While only finite rate is used for the heterogeneous solid-to-gas phase reactions. It is found that formation of soot enhances the H2 production in the gasifier. Carbon conversion gradually increases with an increase in O2 ratio, while producing a low heating value syngas beyond a certain limit of O2 ratio. In contrast, an increase in CO2 concentration in the gasifier increases heating value of product syngas.

The Philippine residential sector consumes a large percentage of the country’s generated electricity, and the price of electricity there is one of the highest in Asia. With a government program in renewable energy utilization and energy efficiency, the development of energy efficient houses is important. This paper presents a numerical investigation on how to minimize the house’s energy consumption, and the results show that a house’s electricity consumption can be supported by the installation of solar photovoltaic panels on its rooftop. A solar thermal collector with an auxiliary biomass water heater could support the hot water requirement of the house. The desiccant dehumidification system combined with evaporative and ground cooling systems can keep the house’s indoor temperature below 27 oC with a humidity ratio of less than 11 g/kg year-round. Energy conservation measures such as additional insulation of a concrete house, unplugging of unused electrical appliances and application of light-emitting diode lighting are important to reduce electric energy consumption. The application of new building technologies is having a positive impact on a building’s energy consumption and indoor environment conditions. The results of this study are important for the Philippine programin alternative energy utilization and energy efficiency.

Solar greenhouses can be considered as efficient places for biological CO2 capture and utilization if CO2 enrichment becomes a common practice there. As CO2 enrichment is applied only when greenhouses are closed, ventilated greenhouses-represent a large percentage of greenhouses all over the world-cannot be considered for this practice. Consequently, ventilated greenhouses cannot be considered for CO2 capture and utilization. The aim of this paper is to show-through modeling and simulation- that these ventilated greenhouses can be activated for serving as efficient CO2 capture and utilization places if they are kept closed (to apply CO2 enrichment) and used microclimate control methods alternative to ventilation. The paper introduces a realistic mathematical model in which all the processes and phenomena associated with the biological CO2 capture and utilization by photosynthesis inside greenhouses are considered. The model validity and accuracy were ensured through the good agreement of its numerical predictions with the available experimental results in the literature. The effect of different environmental and planting conditions on the CO2 capturing process (the photosynthesis process) is investigated. A case study was chosen to investigate the effects of the cooling method, cooling temperature, planting conditions, and CO2 concentration level on the cumulative amount of captured CO2 which represents the greenhouse capturing performance. The results show that the capturing performance of greenhouse can be enhanced from value as low as 1.0 g CO2/ m2 day for ventilated greenhouses with low planting density to a value as high as 140 g CO2/m2 day for high planting density when alternative microclimate control methods and CO2 enrichment are applied, considering the appropriate plant type. Additional benefits besides CO2 capture are also discussed for the possible increase of the plant productivity and possible lowering of water consumption by plants.

Currently, the most balanced technical solution for sun protection of glazed areas is the Venetian blind, because it prevents the entry of direct solar radiation, but at the same time provides a view of the outside and allows light to diffuse into the building. The current challenge is to find an improved, integrated technical solution at an affordable cost that requires low maintenance, is suitable for every geographical situation (latitude) and adaptable toeach orientation of building facades. The solar control glass facade FB720 presented here integrates into a single structural element the advantages of protective glass and Venetian blinds.

A novel solar-two-step thermochemical concept for continuous production of H2 or CO from solar energy and H2O or CO2 using the redox pair MOFe2O3/ MO as reactive particles is proposed and assessed. Here, an efficient continuous separation mechanism is devised by the use of an external magnetic field and the weak magnetization of MOFe2O3 at the working temperatures. The mechanism is suitable for systems of ferrites with a Curie temperature in the range 500–800 oC where water or CO2 decomposition occurs. One of the most promising candidates is the Fe3O4/FeO system. Pyromagnetic coefficients for Fe3O4 were obtained experimentally. A simple magnetic trap was employed and the separation ratios Fe3O4/ FeO were obtained. The results are encouraging and motivate the development of full-scale solar reactor prototypes.

Estimation of the landfill gas (LFG) and electricity potential is one of the significant aspects of an integrated landfill development. In view of this, geological surveys were undertaken in all the government operated landfills in Lagos to appraise ground conditions for the exploitation of the anaerobically generated LFG. Thereafter, attempts were made to estimate the electricity potentials based on various equations and models. The geology of the landfill areas is essentially that of the Oligocene to Pleistocene Coastal Plain Sands except for that of Epe landfill area which is of Recent Deposits. The lithologies of the landfills in the Coastal Plain Sands areas seem suitable for landfill gas capture upon capping. Using stoichiometry, an achievable electrical power of 123.75 MW was deduced. By juxtaposition with an established Malaysian scenario, the yearly electrical energy was placed at 646,663.2 MWh with a tariff revenue in excess of US$64.68 million/year. Furthermore, an accruing carbon credit of about US$31.73 million/year is expected from certified emission reduction (CER) under the Kyoto Protocol. However, estimations by comparison with gas capturing sites across the globe yielded a mean of 38.35 MW. This is about 30 % of the theoretical and is capable of providing electricity to over 230,000 inhabitants.Hinged on actuality, this latter evaluation may aid to eradicate spurious estimations for practical purposes, and is critical in terms of global LFG capture economics. The concomitant benefits of LFG exploitation are expected to be exponentially higher in terms of reduction of greenhouse gases and mitigation of environmental hazards.