The vulnerability of fossil fuel prices to worldwide events such as the recent coronavirus (COVID‐19) pandemics increases the interest in renewable energy resources that offer more stable energy ...generation costs. Solar energy is one of the most abundant renewable energy resources that have gained significant interest in the last decades with various challenges related to the forecastingof the energy production from these systems. Solar radiation intensity varies due to the daily and seasonal changes in the sun's position in addition to the variation in the sky clearness from one location to another which is considered as an important factor that affects the deployment of solar energy systems. This study aims to develop statistical models—mainly regression models and parametric model based on ASHRAE model—to estimate the hourly diffuse radiation in Budapest as a case study using the measured hourly global and diffuse radiation between 2011 and 2018. The prediction models relate the clearness index (which is obtained from the extraterrestrial and global radiation) and the global radiation through a generalized equation. The parametric model was developed by finding the optimal site‐specific constants of ASHRAE model for Budapest using the measured data that minimize the root mean square error. In addition, this study presents a comparison between the results from the developed models and the models reported in the literature. The results indicate that all the developed regression models had close correlation coefficients (R2) where the linear, power, and exponential models had the largest R2 (.69). Finally, the linear model was evaluated on a dataset outside the test data range where the linear model was capable of predicting the diffuse radiation with much better R2 (.93).
Renewable microgrids are new solutions for enhanced security, improved reliability and boosted power quality and operation in power systems. By deploying different sources of renewables such as solar ...panels and wind units, renewable microgrids can enhance reducing the greenhouse gasses and improve the efficiency. This paper proposes a machine learning based approach for energy management in renewable microgrids considering a reconfigurable structure based on remote switching of tie and sectionalizing. The suggested method considers the advanced support vector machine for modeling and estimating the charging demand of hybrid electric vehicles (HEVs). In order to mitigate the charging effects of HEVs on the system, two different scenarios are deployed; one coordinated and the other one intelligent charging. Due to the complex structure of the problem formulation, a new modified optimization method based on dragonfly is suggested. Moreover, a self-adaptive modification is suggested, which helps the solutions pick the modification method that best fits their situation. Simulation results on an IEEE microgrid test system show its appropriate and efficient quality in both scenarios. According to the prediction results for the total charging demand of the HEVs, the mean absolute percentage error is 0.978, which is very low. Moreover, the results show a 2.5% reduction in the total operation cost of the microgrid in the intelligent charging compared to the coordinated scheme.
The respiration rate (RR) is a vital sign in physiological measurement and clinical diagnosis. RR can be measured using stretchable and wearable strain gauge sensors which detect the respiratory ...movements in the abdomen or thorax areas caused by volumetric changes. In different body locations, the accuracy of RR detection might differ due to different respiratory movement amplitudes. Few studies have quantitatively investigated the effect of the measurement location on the accuracy of new sensors in RR detection. Using a stretchable and wearable inkjet-printed strain gauge (IPSG) sensor, RR was measured from five body locations (umbilicus, upper abdomen, xiphoid process, upper thorax, and diagonal) on 30 healthy test subjects while sitting on an armless chair. At each location, reference RR was simultaneously detected by the e-Health sensor, and the measurement was repeated twice. Subjects were asked about the comfortableness of locations. Based on Levene’s test, ANOVA was performed to investigate if there is a significant difference in RR between sensors, measurement locations, and two repeated measurements. Bland–Altman analysis was applied to the RR measurements at different locations. The effects of measurement site and measurement trials on RR difference between sensors were also investigated. There was no significant difference between IPSG and reference sensors, between any locations, and between the two measurements (all p > 0.05). As to the RR deviation between IPSG and reference sensors, there was no significant difference between any locations, or between two measurements (all p > 0.05). All the 30 subjects agreed that diagonal and upper thorax positions were the most uncomfortable and most comfortable locations for measurement, respectively. The IPSG sensor could accurately detect RR at five different locations with good repeatability. Upper thorax was the most comfortable location.
Recently, many renewable energy (RE) initiatives around the world are based on general frameworks that accommodate the regional assessment taking into account the mismatch of supply and demand with ...pre-set goals to reduce energy costs and harmful emissions. Hence, relying entirely on individual assessment and RE deployment scenarios may not be effective. Instead, developing a multi-faceted RE assessment framework is vital to achieving these goals. In this study, a regional RE assessment approach is presented taking into account the mismatch of supply and demand with an emphasis on Photovoltaic (PV) and wind turbine systems. The study incorporates mapping of renewable resources optimized capacities for different configurations of PV and wind systems for multiple sites via test case. This approach not only optimizes system size but also provides the appropriate size at which the maximum renewable energy fraction in the regional power generation mix is maximized while reducing energy costs using MATLAB's ParetoSearch algorithm. The performance of the proposed approach is tested in a realistic test site, and the results demonstrate the potential for maximizing the RE share compared to the achievable previously reported fractions. The results indicate the importance of resource mapping based on energy-demand matching rather than a quantitative assessment of anchorage sites. In the examined case study, the new assessment approach led to the identification of the best location for installing a hybrid PV / wind system with a storage system capable of achieving a nearly 100% autonomous RE system with Levelized cost of electricity of 0.05 USD/kWh.
Several research methodologies have recently been developed to allow for the patterning of conductive lines on elastomeric rubber substrates. Specifically, various conductive materials, substrates, ...and fabrication techniques were investigated to develop stretchable circuits. One promising technique recommends the application of axial strain on an elastomer substrate prior to patterning conductive lines on it. When the substrate is released, conductive lines buckle to form waves, making the circuit stretchable. However, the majority of applications of stretchable circuits require fitting them to two-dimensional surfaces, such as the human body. Hence, in this paper we propose the concept of radial pre-stretching of the substrates to enhance the stretchability of the fabricated circuits. In particular, straight silver conductive lines were deposited on a polydimethylsiloxane (PDMS) surface using inkjet printing technology, and subsequently tested under both axial and radial loads. Radial pre-stretching was compared to axial pre-stretching, resulting in an improved performance under radial loads. The optimal performance was achieved by pre-stretching the PDMS substrate with a radial strain of 27%. This resulted in stretchable circuits which could sustain radial loads with an average breakdown strain of approximately 19%. Additionally, horseshoe patterns were printed on radially pre-stretched PDMS substrates and their performance was compared to that of their straight line counterparts. Though these patterns are generally favorable for the fabrication of stretchable circuits, the optimal horseshoe pattern examined in this study could only sustain up to 16% radial strain on average when radially pre-stretched by 27%.
With the clear adverse impacts of fossil fuel-based energy systems on the climate and environment, ever-growing interest and rapid developments are taking place toward full or nearly full dependence ...on renewable energies in the next few decades. Estonia is a European country with large demands for electricity and thermal energy for district heating. Considering it as the case study, this work explores the feasibility and full potential of optimally sized photovoltaic (PV), wind, and PV/wind systems, equipped with electric and thermal storage, to fulfill those demands. Given the large excess energy from 100% renewable energy systems for an entire country, this excess is utilized to first meet the district heating demand, and then to produce hydrogen fuel. Using simplified models for PV and wind systems and considering polymer electrolyte membrane (PEM) electrolysis, a genetic optimizer is employed for scanning Estonia for optimal installation sites of the three systems that maximize the fulfillment of the demand and the supply–demand matching while minimizing the cost of energy. The results demonstrate the feasibility of all systems, fully covering the two demands while making a profit, compared to selling the excess produced electricity directly. However, the PV-driven system showed enormous required system capacity and amounts of excess energy with the limited solar resources in Estonia. The wind system showed relatively closer characteristics to the hybrid system but required a higher storage capacity by 75.77%. The hybrid PV/wind-driven system required a total capacity of 194 GW, most of which belong to the wind system. It was also superior concerning the amount (15.05 × 109 tons) and cost (1.42 USD/kg) of the produced green hydrogen. With such full mapping of the installation capacities and techno-economic parameters of the three systems across the country, this study can assist policymakers when planning different country-scale cogeneration systems.
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•Three 100% renewable energy systems are optimally sized and located for Estonia.•Excess energy is used for district heating and hydrogen fuel production.•The optimal hybrid PV/wind system has a total capacity of 194 GW, mostly wind.•The optimal hybrid system produces 15.05×109 tons of hydrogen fuel.•The minimum cost of hydrogen production is 1.42 USD/kg.
Fluctuations in fossil fuel prices significantly affect the economies of countries, especially oil-importing countries, hence these countries are thoroughly investigating the increase in the ...utilization of renewable energy resources as it is abundant and locally available in all the countries despite challenges. Renewable energy systems (RES) such as solar and wind systems offer suitable alternatives for fossil fuels and could ensure the energy security of countries in a feasible way. Zimbabwe is one of the African countries that import a significant portion of its energy needs which endanger the energy security of the country. Several studies in the literature discussed the feasibility of different standalone and hybrid RES either with or without energy storage systems to either maximize the technical feasibility or the economic feasibility; however, none of the studies considered maximizing both feasibilities at the same time. Therefore, we present a techno-economic comparison of standalone wind and solar photovoltaic (PV) in addition to hybrid PV/wind systems based on maximizing the RES fraction with levelized cost of electricity (LCOE) being less than or equal to the local grid tariff where Gwanda, Zimbabwe, is the case study. The methodology suggested in this study could increase the utilization of renewable energy resources feasibly and at the same time increase the energy security of the country by decreasing dependency on imported energy. The results indicate that the PV/wind hybrid system does not only have the best economic benefits represented by the net present value (NPV) and the payback period (PBP), but also the best technical performance; where the maximum feasible size of the hybrid system-2 MW wind and 1 MW PV-has RES fraction of 65.07%, LCOE of 0.1 USD/kWh, PBP of 3.94 years, internal rate of return of 14.04% and NPV of 3.06 × 106 USD. Having similar systems for different cities in Zimbabwe will decrease the energy bill significantly and contribute toward the energy security of the country.
With the growth in the solar photovoltaic (PV) market, there is a renewed interest in increasing the system’s annual produced energy. Most of the proposed solutions in the literature require special ...additional equipment, which might adversely affect the cost of the produced energy. This paper proposes an integrated PV-reflector system that augments the solar irradiance on already installed PV modules. A new mathematical model has been developed in MATLAB R2020a to simulate and techno-economically assess the proposed integrated PV system during the entire year using real meteorological data. A genetic algorithm has been employed in MATLAB R2020a to obtain the optimal geometric and optical parameters that maximize the annual produced energy and minimize the Levelized Cost of Electricity (LCOE) at two selected locations (Cairo in Egypt and Ma’an in Jordan) and for three module technologies (monocrystalline, polycrystalline, and thin film) and different commercial reflectors. The optimal system configurations increased the annual energy production by up to 6.05, 5.14, and 8.34% for the three PV technologies, respectively. For both locations, the optimal tilt angles of the PV module and reflector range between 24° and 34° for Cairo, and between 19° and 36° for Ma’an, depending on the PV technology. Finally, all the system configurations have favorable and low payback periods (∼3 and 6.5 years for Ma’an and Cairo, respectively), as well as attractive LCOE, which varies between 0.0369 and 0.044 USD/kWh in Ma’an and between 0.0543 and 0.065 USD/kWh in Cairo.
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•Back reflectors are used for enhancing the energy production of PV plants.•Monocrystalline, polycrystalline, and thin-film plants are assessed and optimized.•Plants have optimal PV and reflector tilt angles around 23 and 37°, respectively.•LCOE increases by a maximum of ∼5% in most systems when using reflectors.•Back reflectors are preferred when their reflectivity is lower (around 0.81).
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