INTERNATIONAL JOURNAL OF ENERGY AND ENVIRONMENTAL ENGINEERING
Year:2014 | Volume:5 | Issue:1|Papers Count:9

Instantaneous solar irradiance profiles or solar irradiation data collected with small time intervals (e.g., minutes) are usually required for the energy simulation of photovoltaic systems, especially as concerns the estimation of the cell temperature. However, meteorological stations and technical standards often provide just monthly average values of the horizontal daily solar irradiation; extensive climate databases that make available up to date hourly observation data or satellite-derived data are seldom available. The goal of the present paper is to investigate the suitability and the accuracy of a methodology aimed at estimating the time profile of the cell temperature of a photovoltaic system on the basis of only the monthly mean values of the daily global irradiation on a horizontal surface. The methodology consists of a chain of well-established models that are applied one after another, in a stepby-step procedure, in order to derive the cell temperatures from the solar radiation data. In particular, we selected different models as possible candidates for each step of the methodology and compared their predictions with measured data to identify the most suitable ones. In addition, we tried several combinations of models in order to identify the most accurate combination. Comparisons with data measured in Rome confirm the suitability of the proposed approach and give information about its accuracy.

Optimal reconfiguration and capacitor placement are used to reduce power losses and keep the voltage within its allowable interval in power distribution systems considering voltage, current, and radial condition constraints.It is needed to solve two nonlinear discrete optimization problems simultaneously, so an intelligent algorithm is used to reach an optimum solution for network power losses. An effective method and a new optimization algorithm using ‘‘improved binary PSO’’ is presented and discussed to minimize power losses in distribution network by simultaneous networking of reconfiguration and capacitor placement. The proposed model uses binary strings which represent the state of the network switches and capacitors. The algorithm is applied and tested on 16-and 33-bus IEEE test systems to find the optimum configuration of the network with regard to power losses. Five different cases are considered and the effectiveness of the proposed technique is also demonstrated with improvements in power loss reduction compared to other previously researched methods, through MATLAB under steady-state conditions.

In this paper, a functional remote experimentation system tested for long-term use stability and under real weather conditions is presented. The proposed system offers the ability to students and anyone interested to remotely conduct experiments with a real PV module from anywhere on the planet, as long as an Internet connection is available. This innovative system is based on a 55Wp photovoltaic panel installed facing south on the roof of a lab, which is installed on a motorized mount allowing it to alter its tilt angle from 0o to 90o. A camera offers continuous live video streaming of the test site. In order to demonstrate a portion of the aforementioned system’s potential, a set of five proposed educational experiments and exercises that may be performed through the Internet is being comprehensively demonstrated in this paper. Each test creates an I-V and a P-I chart, as well as a TXT file with the test data, which is automatically stored for future use. The procedure only takes a few seconds to complete and the extracted data can then be studied and analyzed in due time, allowing the student to contemplate on the results and put theoretical knowledge into practice. Remote access to a renewable energy lab opens new ways to the education of photovoltaics by offering the students a feeling of direct experience with actual PV equipment and is a process exceptionally useful for part-time learners, distance learners, as well as students with disabilities.

The use of phase change materials (PCMs) for the building sector is increasingly attracting attention from researchers and practitioners. Several research studies forwarded the possibility of incorporating microencapsulated PCM in plastering mortars for building facades, in pursuit of increased energy efficiency associated with the heat storage capacity of PCM. However, most of these studies are centred in the use of a single type of PCM, which is bound to be more adequate for a given season of the year (e.g. winter or summer) than for all the seasons.The study proposed in this work regards the evaluation of the possibility of using more than one kind of PCM, with distinct melting ranges, here termed as hybrid PCMs, in plastering mortars, to achieve adequately advantageous performance in all seasons of the year. To characterize the PCM, the specific enthalpy and phase change temperature should be adequately measured. The main purpose of this study was to show the conceptual feasibility of combining PCMs in mortars and to evaluate the behaviour of the resulting mortars with differential scanning calorimeter.The results showed that the behaviour of the mortar that contains more than one type of PCM can be predicted through the superposition of effects of the independent PCMs and no interaction occurs between them. The knowledge obtained from the experimental testing established bases for a framework of numerical simulation of real-scale applications, which can be used to ascertain the feasibility of the hybrid PCM concept for decreases in energy consumption of heating/cooling demands in the buildings.

In the last years, the thermoacoustic phenomena had risen the scientific community interest due to its implications in thermodynamics, heat transfer and acoustic matters, that make possible the conversion between sound and heat. This work aimed at exploring the Russell-Weibull refrigerator, analyzing the behavior of the different parts to achieve a good level of thermal separation, together with the capability of working standalone. Special attention was paid to all those parts that need to be designed properly with explanation of the physics that ruled them, such as the sound generator, the woofer box, the stack and the tube insulation. During the second part of the work, the results obtained are discussed, consistently showing that, if some expedients are adopted, this simple refrigerator can achieve a temperature difference of 24oC. The design choices concerning materials and geometries had great influence on the device behavior.

In this paper, the solar radiation on diversely oriented surfaces and optimum tilts for solar absorbers were assessed. The KT solar radiation model was coded in the MATLAB-based environment to compute the monthly solar radiation values. Seven-year data of monthly average daily solar radiation on a horizontal surface in Bangi, Malaysia (latitude=3oN) were adopted as input in the simulation programme and the results were compared with the local optimum tilt angle at solar noon and other solar radiation model. The contour mappings of solar irradiation at various orientations in 12 months were presented.Results showed that the surface tilted £20o could intercept a relatively high solar intensity, which was less sensitive to the variation of azimuths with average solar insolation deviation of 11.82%. The monthly optimum tilt angle altered throughout the year, ranging from -24o (in equator direction) to +22o (in north direction). The estimated annual optimum slope, 1.4o facing to the equator, was close to local latitude. Based on the seasonal analysis, the northfacing surface was able to intercept higher daily average solar radiation energy compared to south-facing plane. The optimum angles for seasonal south- and north-facing surfaces were found to be 14.4o and 14.8o, respectively, with a tolerable slope deviation of ±5o from the optimal values in the present work.

Biohydrogen production could be generated from organic wastes: food and beverage processing wastewater, restaurant food waste and raw starch waste.Fermentative hydrogen production from food and beverage processing wastewater by sewage microflora was optimized in terms of pH (4.5-7.0), mesophilic condition (35±2oC) and thermophilic condition (50±2oC). Low initial pH (6.5) and mesophilic condition favored hydrogen production (0.28 L/L) indicating that such parameters along with the wastewater characteristics were crucial to dark-fermentative hydrogen production. Pretreatment methods (methanogenic inhibitor, sterilization, sonication and acidification) on restaurant food waste and raw starch waste to enhance biohydrogen production were also investigated in this study. Maximum hydrogen yields of 3.48 and 2.18 ml H2/g COD were observed on sterilization of pretreated restaurant food and raw starch wastes, respectively.

As the use of photovoltaics expands, with more and more commercial and residential users investing on solar energy systems around the globe, there is substantial demand for relatively simple, easy-to-use software packages, for the planning and performance estimation of photovoltaic installations by installers and architects. In this paper, the calculative accuracy of TRNSYS, Archelios, Polysun, PVSyst, PV*SOL and PVGIS is being examined in comparison to the real electrical energy generated by a grid-connected 19.8 kWp photovoltaic installation. The assessment has been performed by using the climatic data which have been recorded at the site of the real PV park over the same calendar year. Our results displayed that the software packages tend to overestimate the global irradiation received by the PV modules, but still significantly underestimate the electrical energy generated by the installation.

The study investigated the economic value of biodiversity attributes that could provide policy makers reliable information to estimate welfare losses due to biodiversity reductions and analyze the trade-off between biodiversity and economics. To obtain the non-market benefits of biodiversity conservation, an indirect utility function and willingness to pay for biodiversity attributes were applied using the approach of choice modeling with the analysis of multinomial logit model. The study found that Mekong Delta residents accepted their willingness to pay of VND 913 monthly for a 1% increase in healthy vegetation, VND 360 for an additional mammal species and VND 2, 440 to avoid the welfare losses of 100 local farmers.