Band 10, Heft 1

Energy consumption in the field of transportation comes next to industrial consumption worldwide. If transportation is completely powered by renewable energy, the utilization of fossil fuels can be drastically reduced, which will result in a lesser amount of greenhouse gas emissions. Electric vehicles (EVs) can act as an alternative to make transportation pollution-free. Large-scale usage of EVs causes high electricity demand on the supply system. This problem can be overcome by utilizing renewable energy sources (RESs) for Electric Vehicle charging. Due to the unpredictability of RESs, coordinating EV charging with other loads and renewable generation is problematic. By using EVs as energy units, power fluctuations in the electric grid can be compensated. This paper presents a summary of recent research in the domain of integration of electric vehicles (EVs) to the smart grid. Electric vehicles-smart grid integrated systems face several issues related to communication, grid infrastructure and control in the future power system. Smart grid technologies are summarized in Section 2. The existing research articles in this area are classified into two based on the purpose: EVs integration into the electric grid and Vehicle to grid services. Finally, the research gaps and future scope of incorporating electric vehicles with renewable energy sources and the Smart grid are highlighted.

This study analyzes the feasibility of the photovoltaic-thermoelectric (PV-TE) hybrid system and examines the appropriate parameters to optimize the design of the hybrid system. A new formula that sets a minimal working condition from which the output power of the hybrid system will exceed that of the PV cell alone at 298 K was developed. The experimental results showed that the hybrid system outperformed the PV cell alone at 298 K, once the minimal working condition is attained. Moreover, the results illustrated that we can enhance the performance with a slight change in the cold side temperature of the TE using PV cells with a relatively small temperature coefficient and efficiency. The results indicated also that the model can produce trustworthy predictions, consequently, it may be useful during the design of a hybrid system with optimized performance.

A high concentration high-temperature beam down solar point concentrator is proposed, coupled to thermal energy storage and a Stirling engine to deliver fully dispatchable electricity over 24 h. Full 24 h operation at nominal power is permitted during the month of maximum solar energy collection while in the month of minimum solar energy collection, the full power production is limited to 17.06 h. The monthly average capacity factors oscillate between 71 and 100%, with an average of 87.5%. Thanks to an electric heater for the heat storage fluid, the system can accept excess electricity from the grid to compensate for the loss of the solar energy collected every other month versus the solar energy collected during the best summer month, to operate at rated power 24 h a day in every day of the year. In this case, the capacity factor can reach 100% every month. By further increasing the size of the thermal energy storage and the power of the engine, the electric thermal energy storage capability of the system can be enhanced, increasing the amount of electricity otherwise wasted that could be collected from the grid to be then returned when needed.

Levitation based energy harvester (LBEH) is an energy harvesting technology which is used to convert the existing kinetic energy into electrical energy. The technique utilizes a levitating magnet which in a closed container vibrate or moves for the subjected vibrations. An outer coil which will extract energy into electrical voltage is carefully selected or designed or the rating. In this research work, a conventional LBEH is designed, simulated, and studied for a particular vibration data. The same is carried out in the FEM analysis software. The system is also mathematically derived and analyzed in the numerical tool. The results obtained from the numerical and FEM tool are compared. At the end of the research work, a parametric study is carried out for the variations in the input characteristics such as frequency, nature of vibrations and other parameters. Results obtained indicate that the power developed is maximum with a value of 0.7 V and 10 mW for the designed natural frequency of 10 Hz and decreases on either side as the bandwidth varies from 5 to 15 Hz.

The flywheel is the simplest device for mechanical battery that can charge/discharge electricity by converting it into the kinetic energy of a rotating flywheel, and vice versa. The energy storage systems based on flywheel now arousing great interest, since this technology can offer great advantages in durability and lifetime. However, the flywheel performance rotation is limited by the strength of the materials, from which it is constructed, and the geometry. Greater control over those parameters could improve the development of high performance of a flywheel energy storage system (FESS). The main interest of this study is to demonstrate the influence degree of each parameter of geometry by using the mathematical method of design of experiments, in order to be able to optimize the adequate parameters for a high performed shape of the flywheel.

The current study aims to investigate and optimize the photovoltaic systems currently in operation at the University of Ibn Tofail in Kenitra, Morocco. The University has started already since 2017 to integrate photovoltaic systems in the form of carports with the objective to reduce the invoices for electricity supplied from the utility grid by at least around 40%. Until then, the University avoided selling the energy surplus to the local electricity provider due to complicated bureaucratic regulations. However, due to the new law on renewable energy adopted by the Moroccan government in November 2021, it will be possible for private households and public service buildings to sell the entire excess of energy produced by renewable energy systems instead of only 20% of the surplus according to the previous law 13-09. For this purpose, this research project seeks to verify whether an expansion of the available photovoltaic installations and the sale of the energy surplus is worthwhile or not. This research work has been done with the optimization software HOMER Pro and presents the obtained optimized results and proposals of two new scenarios in comparison to already existing photovoltaic arrays.

The current research investigated the utilization of fuel cells as an energy storage unit in microgrid energy system applications in an effort to enhance self-consumption of renewable energy. The prototype evaluation is constructed of solar photovoltaic and fuel cell energy storage units. The study utilizes experimental weather and electrical load data for household obtained at 1-min temporal resolution. The daily average energy consumption for the evaluated household was 10.3 kWh, with a peak power output of 5.4 kW and an annual energy consumption of 3757 kWh. The Solar System under investigation has a capacity of 3.6 kWp, while the fuel cell system has a capacity of 0–3 kW, allowing for effective integration with the photovoltaic system and a maximum renewable energy fraction. The research indicates that by installing fuel cells powered by hydrogen generated from renewable energy sources, self-consumption and self-sufficiency significantly increase. The annual energy flow demonstrated that the implementation of 2.5 kW fuel cells improved renewable fraction utilization from 0.622 to 0.918, while increasing energy self-consumption by 98.4% to 3338.2 kWh/year and self-sufficiency by 94.41% to 3218.8 kWh/year.

In order to provide continuous supply for succeeding application, abundant electricity energy and solar energy can be stored by means of thermal storage technology. In the present paper, the heat energy storage/exothermic tests are conducted to evaluate the performance of thermal energy storage and release of electricity energy in the self – designed heat storage box equipped with the composite phase change material (PCM), the delivery of heat to surrounding environment is through an air blower directly. The composite PCM consisting of Na 2 HPO 4 ⋅12H 2 O and Na 3 PO 4 ⋅12H 2 O at the ratio of 7:3 is used to carry out the tests, which is with stable solidification property. Following results are obtained from this research: (1) The solidification temperature of the composite PCM is 33.4 °C with reduced supercooling degree of 2.6 °C; (2) The is phase change exothermic enthalpy value of the composite PCM is 178.02 J/g; (3) The self – designed “peak load shifting” heat storage equipment for electricity energy is with the energy exchange efficiency of 89.59%. The achievements of this research show the applicability of the thermal storage technology by means of the composite PCM.

Energy harvesters and almost all energy generation devices receive the motivation for design from their efficiency and efficiency play an important role in the feasibility and practicability of the design. In this paper, we investigate the efficiency of electromagnetic vibration-based energy harvesters at various electrical loads. In our problem the efficiency depends on excitation frequency, coil and load parameters as well as electromagnetic coupling coefficient. The author first proves that the input power that the harvester receives from its environment at constant base acceleration and constant excitation frequency is always equal to the power that consumes in electrical and mechanical dampers, then the author defines the resonance frequency and plot three efficiency diagrams i.e. plot of efficiency versus (excitation) frequency, plot of maximum efficiency at a constant frequency versus load and in the end plot of the efficiency versus output power at varying load capacitance and resistance. The author observes that maximum efficiency not only does not occur at resonance (i.e. at maximum power) but also is very low (less than 1e−10%) for typical parameters at resonance. Also the maximum efficiency for typical optimum parameters is around 17.45%.

The need to capture the maximum amount of solar energy and to optimize the panels’ collecting surfaces are among the primary objectives of research in solar engineering. The simplest way to accomplish this is to perform a monthly accurate determination of the solar collector’s proper slope and azimuth angles. Indeed, this is the aim of this article, which consists of a graphical optimization based on the Gueymard’s daily integration model. A Matlab program was developed to predict the hourly solar radiation on a solar receiver using the Gueymard model in conjunction with the Liu and Jordan isotropic, Perez, and HDKR anisotropic models. A comprehensive simulation of the monthly solar irradiation throughout 2018 was executed for the city of Annaba, in north–eastern Algeria. The results indicate that the south-facing surface azimuth angle is the most appropriate. In fact, for maximum sunlight capture, the solar collector inclination must be adjusted each month in the range of [10–40°]. Furthermore, the results show that the gains in the amount of solar radiation received throughout the year by the thermal panel mounted at monthly optimum tilt angles are 15.63% in January and 7.37% in July.

The article describes an experimental investigation of the impact of soiling on the photovoltaic modules in northeastern, Iraq. Over five months, the voltage, current power and energy curves of two identical modules with varying cleaning strategies (one was naturally dusty while the other was cleaned regularly) were measured. The impact of soiling on the daily energy produced as well as rain accumulation and particulate matter concentrations are discussed. The results indicated that no losses occurred during wet seasons, but a considerable decline in performance was found during dry periods owing to soiling. Additionally, it was discovered that soiling has a bigger effect on the maximum power than the short-circuit current. After two dry summer months, the greatest power loss of up to 22% was seen. The daily energy loss due to soiling was determined to be 16% on average. Furthermore, there are four polynomial models that have been drowned in prediction photovoltaic module (voltage, current, power, and energy) degradation due to the accumulation of dust.

Piezoelectric energy harvesters are electromechanical systems, capable to convert ambient dispersed mechanical vibrations into usable electrical energy. They can be used for supplying power to sensors and actuators that are wireless connected, miniaturized and remote located. In this work, we analyze piezoelectric energy harvesters for mechanical vibrations in the frequency domain. White Gaussian and colored noise models for random vibrations are considered. The governing equations for the harvester are derived from mechanical properties, the characteristic relationships of piezoelectric materials, and circuit description of the electrical load. We show that the energy harvester can be modelled by cascade connected electromechanical two-ports, and that frequency domain methods are the perfect tool for analysis. Formulas for the harvested power and power efficiency are derived. We also show that application of matching networks reduces the impedance mismatch between the mechanical and the electrical parts, significantly increasing the harvested power and power efficiency. The matching network solution is compared to others, previously proposed solutions, such as application of power-factor correction. We show that the matching network offers nine times more average power and better power efficiency than the unmatched resistive load, and increases by more than 10% the harvested power and efficiency, with respect to the power-factor corrected solution.