INTERNATIONAL JOURNAL OF ENERGY AND ENVIRONMENTAL ENGINEERING
Year:2016 | Volume:7 | Issue:2|Papers Count:9

This paper deals with the occurrence of hot spot phenomena in photovoltaic (PV) systems under partial shading caused by objects on some parts of the modules. An interesting case of diffuse shadows is determined by overhead distribution lines whose path crosses or are in the proximity of the PV power plants. Investigating the impact of these shadows on reducing the power production of PV or on damaging the PV modules as the modules’ temperature is increasing, is of high interest. At the Solar Tech laboratory of Politecnico di Milano, the conditions for hot spot phenomena occurrence due to the overhead lines shading the PV cells were reproduced. Two experimental campaigns were carried out to investigate the current– voltage and power–voltage characteristics, and the energy production. In each experimental campaign, the built shading structure was considered fixed and different shading conditions were created based on the natural displacement of the sun. The hot spot phenomena was revealed on a field PV installation in Italy, caused my medium voltage overhead lines shading the PV cells, using infrared imagery.

This paper deals with standalone small power generation employing three self-excited induction generators under varying speeds feeding an isolated load. The proposed system utilizes three-level cascaded H-bridge inverter for the three generators. The control scheme has the capability of regulating the output voltage for balanced operation of a three-phase isolated load under variable speed. The proposed control can be implemented using DSPACE 1104, and the experimental results are presented to demonstrate the effectiveness of the proposed controller for an isolated generating system.

Experimental data is often the result of long and costly experimentations. Many times, measurements are used directly without (or with few) analysis and treatment. This paper, therefore, presents a detailed methodology to use steady-state measurements efficiently in the analysis of a thermodynamic cycle. The reconciliation method allows to correct each measurement as little as possible, taking its accuracy into account, to satisfy all constraints and to evaluate the most probable physical state. The reconciliation method should be used for multiple reasons. First, this method allows to close energy and mass balances exactly, which is needed for predictive models. Also, it allows determining some unknowns that are not measured or that cannot be measured precisely. Furthermore, it fully exploits the collected measurements with redundancy and it allows to know which sensor should be checked or replaced if necessary. An application of this method is presented in the case of a reversible HP/ORC unit. This unit is a modified heat pump which is able to work as an organic Rankine cycle by reversing its cycle. Combined with a passive house comprising a solar roof and a ground heat exchanger, it allows to get a positive energy building. In this study case, the oil mass fraction is not measured despite its strong influence on the results. The reconciliation method allows to evaluate it. The efficiency of this method is proven by comparing the error on the outputs of steady-state models of compressor and exchangers. An example is given with the prediction of the pinch-point of an evaporator. In this case, the normalized root mean square deviation (NRMSD) is decreased from 14.3 to 4.1 % when using the reconciliation method. This paper proves that the efficiency of the method and also that the method should be considered more often when dealing with experimentation.

Japanese Government is formulating new energy policies in the utilization of alternative energy sources to reduce reliance on nuclear and fossil-powered energy sources. This study shows the numerical evaluation of utilizing alternative energy sources for the demonstration single family detached house. The study shows that utilization of different alternative energy sources both offsite and on-site could reduce the house’s dependency on grid line electricity and fossil fuel. The installation of photovoltaic roof tiles, excess generated electricity could be sold through the feed-in tariff scheme. The utilization of a biomass fuel water heater could reduce the carbon dioxide emission. The combination of photovoltaic roof tiles and solar thermal collector with biomass fueled water heater allows the house to sell excess electricity produced, and eliminates the carbon dioxide emission.

Reduced models of combined heat and power plants are required for different applications. Among other usages, they are implemented as mixed integer linear programs (MILP) in energy market models or price-based unit commitment problems to study the economic feasibility and optimal operation strategies of different units. Generic models are particularly useful when limited information is available for each considered plant. This paper presents a MILP modeling approach for combined heat and power (CHP) plants. The approach is based on energy and exergy balances and a few typical plant characteristics for different operating conditions. The reduction of electrical power output due to heat extraction is estimated by the transferred exergy to the district heating network. Furthermore, the accuracy, strengths and limitations of this approach are investigated for various CHP plant types with extraction condensing turbines designed for district heating systems. Therefore, detailed thermodynamic cycle simulations of CHP plants including part load operations are used to obtain the real plant operating conditions to compare them to the results of the described generic approach. The validation of the reduced, generic model shows that the accuracy mainly depends on the effectiveness of the heat extraction from the CHP plant. In addition, it can be seen that the main advantage of the presented exergy-based method is the inherent consideration of the feed flow temperature for the calculation of the power reduction due to heat extraction.

The further development of sub-Saharan Africa is hinged on the possibility of the provision of uninterrupted power supply. Agriculture, education, and the economy in general are greatly affected by the power outage that has become difficult to comprehend. The energy system is inauspicious that only one in five inhabitant has access to electricity. Having electricity is necessary. Having access to clean energy is crucial. For example, a large number of people in Nigeria have electrical generators that release toxic fumes detrimental to the human health. Utilizing clean energy is considered the way of the future and to do that strategically locating the generating plants is important. Therefore, the introduction of solar parks (SPs) as well as solar and wind-assisted parks (SWAPs) on a wide scale is worthy of consideration since it yields an effective way of generating clean energy. This paper presents the application of a location model for SPs and SWAPs from a country’s perspective. In particular, we focus on Nigeria and Ghana. The power supply infrastructure of both countries, as well as the policies surrounding the provision of off-grid energy are analyzed in depth. We present the advantages and disadvantages of two different methods (the grid approach and the problem owner method). We choose a hybrid approach by combining the grid and the problem owner method (POM). We apply the grid method to regions with high population density and utilize the POM for less populated areas. Furthermore, we take into account power plants that are operational or will be so in the near future. In the above fashion we design two separate, capacitated networks of SPs and SWAPs, one for Ghana, one for Nigeria. Each of these is powerful enough to cover-in a sustainable way-the energy requirement of the majority of households by a facility within reasonable distance.

In the presented work, a model is created in order to investigate the effect of different material parameters and operating conditions on the anode diffusion overpotential, which influence the exergy and energy efficiency of the solid oxide fuel cell (SOFC). In this research, it was demonstrated that the anode material parameters and operating conditions of the device components such as porosity, tortuosity, pore diameter, temperature, pressure and current density of the anode have various effects on the anode diffusion overpotential, which consequently affect the exergy and energy efficiency of the SOFC. The model has provided a strong direction on how to optimize the SOFC exergy and energy efficiency, by reducing the anode diffusion overpotential, which is affected by various material parameters and operating conditions.

Polymer processing is an energy-intensive industry. The plastification of polymers requires a high volume of electric power for thermal energy. Electricity based power is the common form of energy in polymer processing and provides obvious potential for a reduction in energy use and costs. Measures to avoid production based conversion losses, total conversion and transportation losses in energy used all have social, national, economic and business relevance. A bottom-up evaluation of four different production factories in this study assesses the potential for energy use improvements. The resulting theoretical assessment suggested that reducing primary energy demand is the most powerful target for reducing energy intensity in the polymer industry followed by the introduction of improved technologies to raise energy efficiency. The transferability of the conclusions was supported by the comparison between two different geographic locations for polymer production in Germany and Western Australia. The findings of this research suggest potential in their use in ‘green’ decision-making in the plastics industry.

Wind turbines, because of their height and localization, are frequently subject to direct lightning strikes. Thus, the investigation on the performance of their grounding system is of paramount interest for the prediction of the potential threats either for people working in (or animals passing through) the wind farm area and for the power and control units installed in close proximity of the turbine towers. In this paper, we perform a comprensive study of the transient behavior of the earthing systems of wind turbines. The analysis is conducted in the frequency domain and an hybrid approach, based on circuit theory and Method of Moments, is adopted to fully account for resistive, inductive and capacitive couplings between elements of the ground system. The actual transient behavior is obtained by means of an Inverse Fourier Transform. The results, computed considering a typical wind turbine grounding system configuration, provide more insight on the nature of the early-time transient response of grounding systems and allow to draw up useful design guidelines.