INTERNATIONAL JOURNAL OF ENERGY AND ENVIRONMENTAL ENGINEERING
Year:2018 | Volume:9 | Issue:4|Papers Count:9

The geographical location of Mauritius near the warm tropical waters of the Indian Ocean coupled to the vast exclusiveeconomic zone approximating 2. 3 million square kilometers, encourage the promotion of ocean thermal energy conversion(OTEC) systems. Technological advancements have enabled offshore structures to pump the cold water lying at 1000 m depthin the seawater column to the surface, and through the temperature difference set up with the warm surface layer, drives aturbine and generates electricity. In this study, a model has been developed to compute the temperature difference betweenthe deep (1000 m) and surface (20 m) seawater layers around Mauritius. An algorithm has been implemented to determinethe net power generated from a proposed OTEC power plant, acquired through the processing of sea surface temperaturesatellite images, at a resolution of 1 km. The spatial and temporal variations of the net power generated has been observedby splitting the annual data into four monsoonal time frames. Results show that the south-western region of Mauritius possesseshigh OTEC resources, with annual mean daily net power generation capacity of about 95 MW, representing about20% of the peak power demand of the island. Moreover, the bathymetry of the southern region is propitious due to deepcold water availability at a proximity of less than 5km from the coastline. The energy and exergy efficiencies of the OTECsystem are found to be 1. 9 and 22. 8%, respectively. A cost– benefit analysis indicates that profits of the order of 4. 5 timesthe initial investment can be generated.

Accurate and precisess estimation of spatio-temporal variability of solar radiation is critical. Some commonly used modelsevaluate this variability using methods in which the data required for estimating atmospheric attenuation may not be easilyaccessible for some study areas. Here, a daily solar radiation estimation method which uses ambient air temperature, aDigital Elevation Model, time of year, and monthly radiation estimates from Solar Analyst model has been proposed. Theobjective was to use air temperature-based empirical models for atmospheric transmissivity and diffuse fractions to varytotal monthly radiation estimation from Solar Analyst, and then calculate total daily radiation as a fraction of total monthlyradiation by applying a daily transmissivity-based ratio, as air temperature data are readily available at most locations onthe planet. Results revealed that daily solar radiation can be estimated very well, with Mean Absolute Bias Error of around40– 53 W m− 2 or Mean Bias Error of ± 10%, under all sky conditions at seven sites in diverse climate regions, using significantlyless input data. The presented method is an improvement over previously used methods with Mean Bias Error ofunder 10% but more input parameters. Furthermore, the hourly solar radiation values can be calculated using the presentedmethod using the ratio between daily and hourly radiation, for example from literature values and estimated daily insolation. The result also showed that the method is more useful for those stations with substantially higher numbers of sunny daysthan cloudy or partly cloudy days because the uncertainty of the model decreased from cloudy to sunny sky conditions. Theimplemented Digital Elevation Models environment of this method makes it applicable in many studies that need spatialestimation of solar radiation, especially for solar energy generation projects.

Installation layout of wind turbines plays a prominent role in the design of every wind farm. Thus, the wind farm layout optimizationproblem is proposed to maximize the total power output with the minimum cost. In this research, Kahrizak region inTehran province of Iran is selected as a windy region and its real wind speed data are gleaned. Three different scenarios arealso considered, with various number of generations and populations for GA parameters, effective distances, and longitudeand latitude distances of turbines from each other. Among these scenarios, the best result is obtained for the one in whichthe longitudinal distance between turbines is greater than the latitudinal distance. By observing the wind rose of Kahrizakregion, it is observed that the dominant wind direction of the region is toward the east and south– east. Therefore, by increasingthe longitudinal distance of the turbines from each other, the efficiency can be improved and the turbine layout becomesmore realistic. In this case, the efficiency rate and normalized cost of turbines are 89. 5% and 37. 4, respectively, and also 56turbines are needed. The amounts of efficiency and power output are very convenient for real wind speed data of a region.

Buildings play an important role in the energy consumption of a household. There are different types of buildings and differentstandards, which are for each of them. Hence, the decentralized energy system has different configurations for each buildingstandards and buildings built up according to each standards and have necessity to be controlled in a different approach. Using a case study of four different standards— Sonnenhaus, KfW55, Passive house and WSchVO95 of single family houses(SFH) of same geometry and boundary conditions the control constraints are showcased. The houses are selected such thathigh renewable energy self-production, low energy demand house, low net energy house and an old 1995 constructed houseare compared. The differences in the system design, their control strategy and how it affects the system sizing or renewablefraction is explained in this paper. The same SFH according to different standards is simulated with TRNSYS and the energysystem (including solar thermal collectors, PV, gas boiler, fuel cell CHP, thermal storage and electrical storage) for eachhouse is optimized and compared. Thus, the paper showcases the importance of the building, not only geometry but alsobuilding physics and energy efficiency. Finally, the necessity for intelligent control system for a complicated building systemwith multiple energy source is justified and the requirements of such control systems are enlisted.

The aim of the present study is to evaluate the technical and economic feasibility of supplying recharge points for ElectricVehicles converting water pressure in excess into electric energy from a water distribution network. A real water distributionnetwork was analyzed, by designing a power station consisting of three components: a Pump-as-Turbine, an ad hoc generator, and a control system. The last one controls the flow rate trend at the inlet of the Pump-as-Turbine to regulate the rotationalspeed corresponding to the optimal range of efficiency. Energy produced permits to supply a recharging point for ElectricVehicles on site with the aim to convert water pressure generally dissipated and, consequently, lost into a renewable energyand to reduce power grid congestion. The economic analysis confirms the convenience of the proposed power station, andoverall, a comparable cost with pressure reduction valve devices normally adopted to control pressure pattern and leakagesof a water distribution network.

In this work, photovoltaic thermal-compound parabolic concentrators (PVT-CPC) are integrated to a single slope solar still(SS-SS) through a heat exchanger placed in the basin. A continuous water flow is provided over the condensing cover ofSS-SS for yield enhancement. An effect of cooling condensing cover on energy and exergy analysis (thermal and electrical)together with the production cost of distilled water (₹ /kg) has been studied for the following three cases: (I) the proposedpartially covered photovoltaic thermal-compound parabolic concentrator single slope solar still (PVT-CPC-SS-SS), (II) fullycovered thermal-compound parabolic concentrator single slope solar still (PVT-CPC-SS-SS), and (III) flat plate thermalcompoundparabolic concentrator single slope solar still (FPC-CPC-SS-SS). Design parameters have been optimized for maximumdistillate output (energy) and exergy on annual performance basis. Moreover, higher daily yield (37. 9 kg) is obtainedfor case (iii). In addition, higher electrical module efficiency (13%) is obtained for case (ii) for the month of January when thesolar cell temperature is 55 ° C at the optimized conditions. However, the proposed system gives daily yield (35. 78 kg) andgenerates electricity at module efficiency of 12%. The energy payback time of the proposed system is estimated to be 2 years.

Anaerobic digestion to produce biogas is generally considered as one of the most sustainable technologies for the productionof renewable energy. During this microbial process, organically bound nitrogen is released as ammonium that ends up in thedigestate and finally may inhibit the process. In this study, it is investigated if ammonium can be removed and recovered outof the liquid fraction of a thermophilic digestate from a potato processor. This is achieved at laboratory scale through an easyand self-designed stripping and scrubbing process using Vigreux and Dufton columns, which are commonly used laboratoryfractionating columns. The stripping is performed at pH 8. 5 and at 323. 15 K (50 ° C), which results in the volatilization ofthe ammonium present in ammonia. Subsequently, the stripping gas charged with ammonia is put into contact with a sulphuricacid solution, resulting in (NH4)2SO4, which can be used as an N– S fertilizer. In addition, the digestion experimentshave demonstrated that the biogas yield is 36% higher after removal of the ammonium from the digestate compared to theuntreated digestate.

Grate firing is one of the main competing technologies in biomass combustion for steam and electricity generation. Ashgenerated in the furnace during combustion process would greatly reduce the boiler thermal performance and may lead tounscheduled shutdown. The focus of this study is to optimize the combustion characteristics of the mixture of palm kernelshell (PKS) and selected additives (Al2O3, MgO and CaO) to develop a fuel mixture of low ash yield and higher heatingvalue (HHV). D-Optimal Design under Cross Methodology of Design Expert (6. 08) was employed to mix the componentsalongside various particle sizes. The mixed samples were ashed in a muffle furnace (848 K) to a constant weight and theirHHV were determined using Ballistic Bomb Calorimeter. Combustion test based on optimized PKS additive mixture wasconducted with a 5 kW grate furnace from which the effects of varying the ratio of primary to secondary air flow rate ontemperatures and flue gas compositions from the furnace were measured. The ash obtained after combustion process wascharacterized using X-ray diffraction (XRD) for the purpose of identifying the mineral phase compounds that are present inPKS and PKS-additive ash. The optimum composition obtained for the process was 2. 5, 0. 0, 5. 0, 92. 5% and 5. 50 mm foradditives (Al2O3, MgO, CaO), PKS and particle size, respectively. The composition resulted in lowest ash yield (0. 56%) andHHV (20. 64 kJ/g). The coefficient of determination (R2) (0. 7951 and 0. 7344) and least-square errors (0. 19 and 0. 024) of theprediction model indicated a close fitness to the experiment results obtained for ash yield and HHV. Primary to secondaryair ratio of (40: 60) recorded maximum temperature (1058 K), minimum level of CO (285 ppm) and 6% oxygen. XRD resultsshowed excellent interaction between PKS and additives. The appearance of potassium-alumino silicate (KAlSiO4) in thePKS-additive ash prevented the release of potassium chloride which has the ability to increase ash deposition and corrosion.

According to the European Cement Association, CEMBUREAU, in 2015, the global cement production was 4. 6 billion tons. Traditional cement production emits approximately 1 ton of CO2per ton of cement, which represents almost 80% of the totalCO2emissions of concrete and approximately 6% of the world’ s emissions. Among supplementary cementitious materials, the use of agro-waste ash emerges due to its reduced CO2emissions, chloride diffusion, and materials cost, in addition toits greater compressive strength. In Colombia, the disposal of agro-wastes, such as tobacco waste, is an environmental andeconomic concern. In this study, ash obtained from tobacco waste (TWA) was studied as a sustainable partial replacementfor cement in hydraulic concrete. The TWA was reduced to a particle size of less than 75 μ m and was characterized by X-rayflorescence. A central composite design was used to study the influence of the ash replacement percentage of cement andthe water/binder (w/b) ratio on the compressive strength at 28 days. The results show that it is possible to replace 10% of thecement with TWA using a 0. 5 w/b ratio and obtain a 51% higher compressive strength than the control mixture at 28 days. Moreover, the experimental results demonstrated an improvement of 86% in the 7-day compressive strength when TWAwas used.