This study aims to develop a controller to operate an energy system-consisting of a photovoltaic thermal (PVT) system combined with a heat pump, using the reinforcement learning approach to minimize the operating costs of the system. For this, the flow rate of the cooling fluid pumped through the PVT system is controlled. This flow rate determines the temperature increase of the cooling fluid while reducing the temperature of the PVT system. The heated-up cooling fluid is used to improve the heat pump’s coefficient of performance (COP). For optimizing the operation costs of such a system, first an extensive simulation model has been developed. Based on this technical model, a controller has been developed using the reinforcement learning approach to allow for a cost-efficient control of the flow rate. The results show that a successfully trained control unit based on the reinforcement learning approach can reduce the operating costs with an independent validation dataset. For the case... [more]

The aim of this paper is to demonstrate lithium metal battery cells assembled with high potential cathodes produced by sustainable processes. Specifically, LiNi0.5Mn1.5O4 (LMNO) electrodes were fabricated using two different water-processable binders: pullulan (PU) or the bifunctional electronically conductive poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). The cell performance was evaluated by voltammetric and galvanostatic charge/discharge cycles at different C-rates with 1M LiPF6 in 1:1 (v:v) ethylene carbonate (EC):dimethyl carbonate (DMC) (LP30) electrolyte and compared to that of cells assembled with LMNO featuring poly(vinylidene difluoride) (PVdF). At C/10, the specific capacity of LMNO-PEDOT:PSS and LMNO-PU were, respectively, 130 mAh g−1 and 127 mAh g−1, slightly higher than that of LMNO-PVdF (124 mAh g−1). While the capacity retention at higher C-rates and under repeated cycling of LMNO-PU and LMNO-PVdF electrodes was similar, LMNO-PEDOT:PSS featured su... [more]

The Central and South Pacific have significant wave energy resources distributed through the region that are currently not being explored. Even though the wave energy resource in the Pacific has been studied, there is limited knowledge on the potential obstacles when inserting this new energy source into a unique and unexplored environment. Pacific Island countries (PICs) have distinctive characteristics that can become barriers to this technology, especially considering that local coastal and marine systems are fundamental for subsistence and local development. Thus, the success of a project relies on local acceptance. The current study developed an integrative conceptual framework for the PICs (ICFPICs) that derived from the integration of the elements of a political, economic, social, technological, environmental and legal (PESTEL) structured approach and further combined with a strengths, weaknesses, opportunities and threats (SWOT) approach to create a matrix that included relevan... [more]

This paper presents a comprehensive review of multi-port power electronics converters used for application in AC, DC, or hybrid distribution systems in an Internet of Energy scenario. In particular, multi-port solid-state transformer (SST) topologies have been addressed and classified according to their isolation capabilities and their conversion stages configurations. Non-conventional configurations have been considered. A comparison of the most relevant features and design specifications between popular topologies has been provided through a comprehensive and effective table. Potential benefits of SSTs in distribution applications have been highlighted even with reference to a network active nodes usage. This review also highlights standards and technical regulations in force for connecting SSTs to the electrical distribution system. Finally, two case studies of multi-port topologies have been presented and discussed. The first one is an isolated multi-port bidirectional dual active... [more]

An innovative water-treatment process consisting in reducing the nitrate concentration by using an active silica filter obtained from ashes produced during rice-straw thermal treatment has been developed by the LIFE LIBERNITRATE project. A life-cycle assessment (LCA) was carried out to evaluate the environmental impacts of this innovative process, from the production of ashes and extraction and activation of silica to the water treatment. These results were compared to the environmental impact derived from the use of bottled water, instead of tap water, where traditional water treatments (i.e., reverse osmosis) may not be available due to the high installation and operating costs. The comparison showed that the proposed innovative process could contribute to reducing the environmental impact in almost all analyzed impact categories (from 20% for photochemical oxidation to 90% for abiotic depletion) with respect to the use of bottled water. In addition, if conveniently optimized (for ex... [more]

Several investigations have shown that enhanced mixing brought about by wind turbines alters near-surface meteorological conditions within and downstream of a wind farm. When scalar meteorological parameters have been considered, the focus has most often centered on temperature changes. A subset of these works has also considered humidity to various extents. These limited investigations are complemented by just a few studies dedicated to analyzing humidity changes. With onshore wind turbines often sited in agricultural areas, any changes to the microclimate surrounding a turbine can impact plant health and the length of the growing season; any changes to the environment around an offshore wind farm can change cloud and fog formation and dissipation, among other impacts. This article provides a review of observational field campaigns and numerical investigations examining changes to humidity within wind turbine array boundary layers. Across the range of empirical observations and numeri... [more]

Lignocellulosic biomass is a nonedible matrix that can be efficiently exploited as feedstock in an integrated biorefinery after a proper pretreatment. An organosolv pretreatment using an acidified γ-valerolactone (GVL)/water solution was proposed to improve the cellulose enrichment and enzymatic saccharification of cardoon (Cynara cardunculus L.) stems. At the optimal pretreatment condition (140 °C, 0.6 GVL/water, and 2.24% H2SO4), xylan was efficiently removed from the cardoon, and up to 50% of its content was recovered in the aqueous fraction, while 86% of the cellulose was retained in the solid fraction. The resulting cardoon pulp showed a cellulose content of 91.5% and an enzymatic digestibility of 100%. An overall glucose production of 37.17 g/100 g raw material (90% theoretical maximum) was obtained using high solid loading (20% w/w) and a high enzyme dosage (60 FPU/g cellulose). At a low enzyme dosage, glucose concentrations of 169 g/L and 210 g/L were achieved using 10 FPU/g ce... [more]

Wind energy is one of the fastest growing sources of energy worldwide. This is clear from the high volume of wind power applications that have been increased in recent years. However, the uncertain nature of wind speed induces several challenges towards the development of efficient applications that require a deep analysis of wind speed data and an accurate wind energy potential at a site. Therefore, wind speed forecasting plays a crucial rule in reducing this uncertainty and improving application efficiency. In this paper, we experimented with several forecasting models coming from both machine-learning and deep-learning paradigms to predict wind speed in a metrological wind station located in East Jerusalem, Palestine. The wind speed data were obtained, modelled, and forecasted using six machine-learning techniques, namely Multiple Linear Regression (MLR), lasso regression, ridge regression, Support Vector Regression (SVR), random forest, and deep Artificial Neural Network (ANN). Fiv... [more]

Risk management is critical for corporate finance management systems, in addition to corporate social responsibility (CSR) and sustainable development (SD) programs. Stakeholders need risk information to make informed judgments as to their involvement. No studies exist to date concerning disclosure of non-financial and financial risks in corporate annual statements and Polish strategic sector company reports. The authors sought to determine whether energy companies disclosed risks in non-financial annual reports in 2011−2020 (e.g., CSR, integrated, and board activity reports), and whether one can assess threats, including business activity risks and SD, based on these reports. We assessed the reports of all large Polish energy companies on a three- and five-degree scale to develop a model for risk information disclosures. We have three key empirical findings. Only half the analysed companies disclose annual financial data, threats, and risks. Less than half have implemented and operate... [more]

Employee performance in remote areas is a source of concern for the Saudi Arabian energy sector, which serves as the primary engine of the country’s economy. This research paper aimed to study the impact of social disconnectedness and career advancement on employees’ performance through employee satisfaction as a mediator. The targeted population was employees worked in remote areas in the energy sector. Data were collected using a web-based questionnaire and distributed electronically using social media. A total of 390 respondents participated in this study, and structural equation modeling (SEM) was employed to analyze the collected data. The study findings revealed that career advancement positively impacts employee performance; however, social disconnectedness negatively impacts employees’ performance. Both career and social factors had an indirect effect on employees’ performance through employee satisfaction. Lastly, results demonstrated a positive impact of employee satisfaction... [more]

We confront empirical data on citizen-led renewable energy capacities in Poland with results obtained from a meta-theoretical, empirical analysis of the national energy system. We elicit and rank essential disabling and enabling factors that explain the current low level of citizen energy in Poland. Altogether, we estimate the contributions of individual and collective prosumers as amounting to about 3.2 GW, with PV installations contributing more than 90%. Most activities are rather recent and come from individual prosumers. The factors with the greatest explanatory power are connected with decades of a rigid, centralized Polish energy system going hand in hand with social, regulatory, and technical lock-ins. Strikingly, factors connected with the heritage of, and transition from, the socialist period are less important, but they do explain why substantially more contributions originate from individuals compared to collective prosumers. Our results show that the currently rather small... [more]

In this study, the development and testing of a hybrid thermal energy storage (TES) including phase change material (PCM) macro-capsules inside a vertical sensible tank is presented. The storage was specifically developed for delivering hot water on board of ships. Accordingly, a commercial PCM was selected and tested. Subsequently, the hybrid TES was designed and tested under mimicked boundary conditions at lab scale, showing the possibility of increasing the volumetric energy storage density up to 30% compared to the sensible configuration. On this basis, two numerical models were developed: a detailed one, implemented in a Fluent environment, aiming at investigating the main parameters affecting the heat transfer efficiency inside the TES and a second one, implemented in an ESP-r environment to simulate the TES as a component to be implemented inside a more complex system, thus helping its accurate design and operation through a reliable modelling phase. Both models were satisfactor... [more]

Crude oil maturity assessment is a vital goal for petroleum geochemistry, and equally important is the exploration of maturity indicators of sufficient credibility. While most molecular proxy parameters have been extensively used and have provided some useful insights; the component ratios approach is somewhat limited in validity regarding oil maturity characterization for variable reasons. Novel thermal trends of hopanes and steranes were observed in a series of hydrous pyrolysates of an immature coal (0.49 %Ro) generated at eight target temperatures ranging from 250−375 °C (measured vitrinite reflectance of 0.71−0.91 %Rm), which−further substantiated this idea. Expelled oil and extractable bitumen were combined as the total soluble organic material (tSOM) for each pyrolysis experiment to mitigate the effects of primary expulsion fractionation. While bitumen extracted from the original coal—the 250 °C tSOM—the 275 °C tSOM (0.49−0.73 %Rm) sequence recorded normal increases in C31 αβ-ho... [more]

The performance of CO2-expanded hexane in the vapor-liquid two-phase region was examined to extract phosphorus-free bio-oil from rice bran. Previously, it was found that in the uniform liquid phase region, it is difficult to maintain the phosphorus concentration at a stable and low level when the CO2 mole fraction changed slightly. To overcome this issue, the dependences of the phosphorus and free fatty acid concentrations, the oil solubility, and the oil yield on the CO2 mole fraction in the CO2-expanded hexane were measured at 25 °C, 5.1−5.2 MPa, and at a CO2 mole fraction of 0.88−0.94 in the two-phase region. Thus, a relatively constant phosphorus concentration of <10 ppm was maintained in the extracted oil, which was ~1/50 of that in the oil extracted by hexane, thereby satisfying the European unified standard for biodiesel fuel. Furthermore, a high oil yield exceeding that of hexane extraction was maintained over all CO2 mole fractions. Moreover, the oil solubility in the CO2-e... [more]

The measurement of the higher heating value (HHV) of municipal solid wastes (MSWs) plays a key role in the disposal process, especially via thermochemical approaches. An optimized multi-variate grey model (OBGM (1, N)) is introduced to forecast the MSWs’ HHV to high accuracy with sparse data. A total of 15 cities and MSW from the respective city were considered to develop and verify the multi-variant models. Results show that the most accurate model was POBGM (1, 5) of which the least error measured 5.41% MAPE (mean absolute percentage error). Ash, being a major component in MSW, is the most important factor affecting HHV, followed by volatiles, fixed carbon and water contents. Most data can be included by using the prediction interval (PI) method with 95% confidence intervals. In addition, the estimations indicated that the MAPE from estimating the HHV for various MSW samples, collected from various cities, were in the range of 3.06−34.50%, depending on the MSW sample.

In this paper, a plate counter-flow dew-point evaporative cooling system was designed with a nanoporous membrane covered on the surface of the wet channel for enhancement of heat and mass transfer. First, the operating principle of this device and theoretical analysis of nanoporous membrane evaporation were discussed in detail. Then, the impacts of several operating parameters on cooling performance, mainly including inlet air temperature, humidity, velocity, and the effect of utilizing the membrane, were investigated in trials. It was found that the cooling performance can be improved by using membrane significantly. In the dry channel, the maximum temperature decrease can reach 12.5 °C. At a high inlet air temperature, the product air can be dropped to a lower temperature, contributing to a more significant heat transfer process. Lower humidity, on the other hand, resulted in a reduced product air temperature and a lower cooling efficiency. Under the condition of 50% humidity, the we... [more]

Drilling fluid represents the most important fluid that must fulfill numerous important assignments during drilling operations. Many commercially available additives for water-based drilling fluid fall into the category of non-degradable and environmentally hazardous materials. Significant development in this area can be made by using biodegradable materials as additives in drilling fluids. The objective of this study was to determine whether mandarin peel powder particle size affects the properties of the drilling fluid. In this paper, mandarin peel was used in the form of a dry powder divided into particle sizes smaller than 0.1 mm, and between 0.1 mm and 0.16 mm. Mandarin peel powder was added to a water-based drilling fluid in four different concentrations (0.5, 1, 1.5, and 2% by volume of water). By increasing the mandarin peel powder concentration, the API filtration reduced up to 42%, PPT filtration significantly decreased up to 61.54%, while the rheological parameters generally... [more]

The building-integrated photovoltaic (BIPV) system is provoking mention as a technology for generating the energy consumed in cities with renewable sources. As the number of BIPV systems increases, performance diagnosis through power-generation predictions becomes more essential. In the case of a colored BIPV module that has been installed on a wall, it is more difficult to predict the amount of power generation because the shading loss varies based on the entrance altitude of the irradiance. Recently, artificial intelligence technology that is able to predict power by learning the output data of the system has begun being used. In this paper, the power values of colored BIPV systems that have been installed on walls are predicted, and the system output values are compared. The current-voltage (I−V) curve data are measured to predict the power required changing the intensity of the irradiance, and the linear regression model is derived for the changes in the voltage and current at a ma... [more]

Reduction of greenhouse gases emissions is a key challenge for the power generation industry, requiring the implementation of new designs and methods of electricity generation. This article presents a design solution for a novel thermodynamic cycle with two new devices—namely, a wet combustion chamber and a spray-ejector condenser. In the proposed cycle, high temperature occurs in the combustion chamber because of fuel combustion by pure oxygen. As a consequence of the chemical reaction and open water cooling, a mixture of H2O and CO2 is produced. The resulting working medium expands in one turbine that combines the advantages of gas turbines (high turbine inlet temperatures) and steam turbines (full expansion to vacuum). Moreover, the main purpose of the spray-ejector condenser is the simultaneous condensation of water vapour and compression of CO2 from condensing pressure to about 1 bar. The efficiency of the proposed cycle has been estimated at 37.78%. COM-GAS software has been used... [more]

Today, the study of thermal systems that take advantage of residual thermal sources in the power generation sector is of great importance to mitigate environmental impact and promote sustainable alternatives in this sector. Among these alternatives, the organic Rankine cycle (ORC) is of great relevance since it allows taking advantage of residual energy sources at low temperatures. This work presents a methodology to evaluate the feasibility of using a refrigerant as a working fluid in an organic Rankine cycle based on an exergetic viability index. As a case study, R134a, R600a, R245fa, and R123 refrigerants were considered. A residual thermal source was used that came from the Hybrid Cycle Plant of the Valley of Mexico. Thermodynamic analysis was performed to determine generated power, thermal efficiency, refrigerant mass flow, pinch point temperature difference, specific steam consumption, unused thermal exergy flow, exergy efficiency, and total heat transfer requirement. The weighte... [more]

Demagnetization is required to prevent a warship from being detected by magnetic mines. However, minimal research has been conducted to establish a suitable deperming protocol, especially the Flash-D protocol. To establish such a deperming protocol, we conducted a theoretical study using Preisach modeling for the Flash-D protocol. Magnetic coercivity distributions were derived from B−H curves representing the material properties of the warship, and a deperming protocol that is effective on particles was proposed. The internal magnetization distribution was analyzed using the program combined with Preisach model and the finite element method (FEM), in accordance with the conventional and proposed protocols, and the proposed method was confirmed to be effective. In addition, the method was verified through experiments in a scaled-down magnetic treatment facility test room. Therefore, the proposed method can be used to establish an effective Flash-D protocol for submarines depending on th... [more]

Heat-pipe-cooled microreactors (HPMR) use a passive high-temperature alkali metal heat pipe to directly transfer the heat of solid core to the hot end of the intermediate heat exchanger or thermoelectric conversion device, thus avoiding a single point failure. To analyze and evaluate the transient safety characteristics of an HPMR system under accident conditions, such as heat pipe failure in the core or a loss of system heat sink and other accidents, a previously developed model for transient analysis of a heat-pipe-cooled space nuclear reactor power system (HPSR) was improved and validated in this study. The models improved mainly comprise: (1) An entire 2-D solid-core heat transfer model is established to analyze the accident conditions of core heat pipe failure and system heat sink loss. In this model, radial and axial Fourier heat conduction equations are used to divide the core into r-θ direction control volumes. The physical parameters of the material in the control volume are c... [more]

When a hydrokinetic turbine operates in a confined flow, blockage effects are introduced, altering the flow at and downstream of the rotor. Blockage effects have a significant effect on the loading and performance of turbines. As a result, understanding them is critical for hydrokinetic turbine design and performance prediction. The current study examines the main and interaction effects of solidity (σ), tip speed ratio (TSR), blockage ratio (ε), and pitch angle (θ) on how the blockage influences the performance (CP) of a three-bladed, untwisted, untapered horizontal axis hydrokinetic turbine. The investigation is based on validated 3D computational fluid dynamics (CFD), design of experiments (DOE), and the analysis of variance (ANOVA) approaches. A total number of 36 CFD models were developed and meshed. A total of 108 CFD cases were performed as part of the analysis. Results indicated that the effect of varying θ was only noticeable at the high TSR. Additionally, the rate of incremen... [more]

Food waste is one of the biggest global challenges. Thinking and acting for closed-loop cycles for energy and resources recovery is pivotal for meeting the Sustainable Development Goal 12.3 (SDG 12.3) by 2030. In this paper, the multifaceted problem of food waste and Greece’s national policy of circular economy is briefly given. Greece produces the highest annual per capita food waste output (142 kg) in Europe, indicating that the problem is rather large for the country. The solution to the problem inextricably linked to the implementation of the food waste hierarchy, was investigated through a survey integrating the possibility of energy recovery. The tailored questionnaire sent via e-mails and social media with the goal of identifying a snapshot of Greek citizens’ conceptions and practices regarding the management of their household food waste, and their familiarity with circular economy concepts. Results have shown that most respondents are aware of the problem’s existence, however,... [more]

With the increasingly stringent regulations on air quality and the consequent emission limits for internal combustion engines, researchers are concentrating on studying new solutions for improving efficiency and energy saving even in off-road mobile machines. To achieve this task, pump-controlled or displacement-controlled systems have inspired interest for applications in off-road working machines. Generally, these systems are derived from the union of a hydraulic machine coupled to an electric one to create compact components that could be installed near the actuator. The object of study of this work is a 9-ton excavator, whose hydraulic circuit is grounded on load sensing logic. The validated mathematical model, created previously in the Simcenter Amesim© environment, represents the starting point for developing electro-hydraulic solutions. Electric components have been inserted to create different architectures, both with open- and closed-circuit layouts, in order to compare the en... [more]