The growing integration of intermittent renewable energy sources (RESs) and the increasing trend of shutting down fossil-fuel-based power plants has brought about the need for additional flexibility in energy systems. This flexibility can be provided in various forms, including controllable generation and consumption, storage, conversions, and exchanges with interconnected systems. In this context, an increasing focus is placed on the development of smart energy systems (SESs) that combine different types of distributed energy resources (DERs), information and communication technologies (ICTs), demand side management (DSM), and energy conversion technologies. The utilization of SESs can lead to multiple benefits for the stakeholders involved; therefore, the assessment of their performance is a primary concern. Due to their multidisciplinary nature, there are no known or universally accepted standards for assessing the performance of SESs. Previous efforts only define key performance in... [more]

This paper suggests a novel way to manufacture power-efficient building-integrated photovoltaic (BIPV) modules that are aesthetically acceptable for use in zero-energy buildings (ZEBs). An optical pattern is formed using additive manufacturing (AM) to maximize the number of sunrays that reach the solar cells and to hide cells beneath the pattern. The optical pattern was optimized by simulation, then selected PV modules were fabricated to ensure that they met the optimal optical pattern conditions. Increase in pattern angle and lens space yielded increase in the output power of the PV module, but reduced the aesthetic functionality. This color BIPV technology is expected to help expand the BIPV market and reduce carbon for “net zero” objectives.

Fast charging is an essential stakeholder concern for achieving a deeper penetration of Electric Vehicles (EVs), as optimizing the charging times of conventional vehicles is as yet a bottleneck to be solved. An important drawback of EV’s fast charging lies in the degradation suffered by the Li-ion Batteries (LIBs) at high charging currents. A deep understanding of the how these fast-charging activities affect the LIBs’ degradation is necessary in order to design appropriate fast charging stations and EV powertrains for different scenarios and contexts. In this regard, the present paper analyzes the effect of fast charging on Libs’ degradation under operation profiles from real driving cycles. Specifically, Battery Electric Buses (BEBs) driving profiles from three demos in European Cities (Gothenburg, Osnabrück and Barcelona) have been used in this analysis. In order to deduce the best practices for the design of the charging stations, different sizes for the chargers have been simulate... [more]

In this manuscript, a novel topology is proposed to integrate on-grid and off-grid PV systems supplying the same load premises. The load side is investigated and analyzed, and critical and non-critical loads are separated in terms of power supply. Critical and seasonal loads usually place stress on the grid’s point of common coupling (PCC). In the proposed topology, they are supplied by a novel topology for an off-grid solar pump PV system that lacks energy storage integration. The lack of energy storage batteries requires a novel design and sizing scheme for the off-grid PV system, and a methodology is proposed in this manuscript. The on-grid PV system is conventionally designed and coupled with the storage-less off-grid PV system to maintain load supply. The proposed methodology minimizes the ratings of the PCC and hence relieves stress on congested grids with renewable energy penetration, especially in condensed urban areas. The proposed structure enables the operation of microgrids... [more]

Obtaining energy from renewable resources is a worldwide trend in the age of increasing energy demand. Hydropower has some potential in this field, especially for low-power locations. However, construction of such facilities requires high expenses, which is why some attempts at lowering the costs have been made, i.e., by proposing alternative solutions to the classic ones. This paper proposes a selection of options for small hydropower plants (SHP) that lower the investment costs while keeping up profitable operations. The proposed solutions concern simplifying the turbine’s and generator’s integration by installing them in dedicated prefabricated concrete modules. A rare but simple and cheap semi-Kaplan type of turbine with a non-classical spiral inflow is proposed. The turbine operates a permanent magnet (PM)-excited generator, converting the energy at a variable rotational speed. Thanks to this approach, it is possible to simplify the regulation system and eliminate expensive mechan... [more]

This paper presents an integrated approach for mathematical statistics, theoretical analysis, and a field test to investigate the distribution law of in-situ stress and its engineering practice of rock burst control. The test site is located in the Juye mining area, Shandong Province, China. The main conclusions included: (1) There are two types of in-situ stress states in the Juye mining area, σH > σV > σh (42.42%) and σH > σh > σV (57.57%), which are mainly caused by the tectonic stress of the Heze and Fushan faults (The σH, σV, and σh is the maximum principal stress, vertical principal stress or intermediate principal stress and minimum principal stress respectively). (2) The lateral pressure coefficients KH, Kh, and Kav show a non-linear distribution with increased depth, approaching 1.32, 0.96, and 1.41, respectively. The variation range of the horizontal difference stress μd is 0.09−0.58. (3) The average value of the stress gradient is 3.05 MPa/100 m, and the main directions of t... [more]

The surface energy balance (SEB) model is a physically based approach in which aerodynamic principles and bulk transfer theory are used to estimate actual evapotranspiration. A wide range of different methods have been developed to parameterize the SEB equation; however, few studies addressed solutions to the SEB considering the land surface temperature (LST). Therefore, in the current review, a clear and comprehensive classification is provided for energy-based approaches considering the key role of LST in solving the energy budget. In this regard, three general approaches are presented using LSTs derived by climate and land surface models (LSMs), satellite-based data, and energy balance closure. In addition, this review surveys the concepts, required inputs, and assumptions of energy-based LSMs and SEB algorithms in detail. The limitations and challenges of aforementioned approaches including land surface temperature, surface energy imbalance, and calculation of surface and aerodynam... [more]

The high importance of demand-side management for the stability of future smart grids came into focus years ago and is today undisputed among a wide spectrum of energy market participants, and within the research community. The increasing development of communication infrastructure, in tandem with the rising transparency of power grids, supports the efforts for deploying demand-side management applications. While it is then accepted that demand-side management will yield positive contributions, it remains challenging to identify, communicate, and access available flexibility to the flexibility managers. The knowledge about the system potential is essential to determine impacts of control and adjustment signals, and employ temporarily required demand-side flexibility to ensure power grid stability. The aim of this article is to introduce a methodology to determine and communicate local flexibility potential of end-user energy systems to flexibility managers for short-term access. The pr... [more]

This paper deals with the energy recovery resulting from the braking transient of trains arriving in a railway station, to feed a railway micro-grid that would be purposely connected to the railway traction circuit to feed the electrical infrastructure required for charging a fleet of electrical vehicles that are parked nearby the station and offered for providing train plus electric vehicle integrated mobility. Based on results of an experimental campaign intended to recording the mechanical quantities related to the braking transient of regional trains arriving in a medium-size station of the Italian railways network, this paper describes a suitable quasi-stationary model that allows the evaluation of the amount of energy that is recoverable over each single day of operation, as well as the micro-grid dynamic electric behaviour due to the sudden energy recovery transient in the railway catenary. The proposed railway micro-grid is discussed, particularly concerning the configuration o... [more]

Bifacial photovoltaic modules combined with horizontal single-axis tracker are widely used to achieve the lowest levelized cost of energy (LCOE). In this study, to further increase the power production of photovoltaic systems, the bifacial companion method is proposed for light supplementation and the efficiency enhancement of tilted bifacial modules with a horizontal single-axis tracker. Specifically, a solar reflector is added to the rear end of the tilted bifacial photovoltaic module to guide the sunlight and promote power generation on the rear end. The technical feasibility of the proposed method is verified through optimal calculation and prototype experimental test. The theoretical calculation results suggest that the bifacial companion system is particularly suitable for mid-to-high latitude areas. The higher the latitude, the higher the gain ratio of generated power in the system; there is an optimal module tilt angle that maximizes the efficiency at different latitudes. The c... [more]

Energy efficiency is an increasingly important dimension of household appliances, which is why they are labeled to indicate their energy consumption. In 2020, the European Union countries changed the labeling system from the previous system: ranging from A+++ to D, to the new system: ranging from A to G, assuming it would be more transparent for the consumer. The aim of the study was to find out the extent to which consumers are aware of the new labeling system, and the impact that the new labels have (compared to the previous ones) on the perception of household appliances and consumer decision-making. For this purpose, the survey was conducted on a nationwide representative Polish sample (n = 1054). The research was partly experimental, where the same appliances were presented with new and previous energy labels. The results showed that currently most people do not identify the new energy classes. Furthermore, products with the new labels are perceived as being less energy efficient... [more]

The linear parameter-varying (LPV) model is widely used in aero engine control system design. The conventional local modeling method is inaccurate and inefficient in the full flying envelope. Hence, a novel online data-driven LPV modeling method based on the online sequential extreme learning machine (OS-ELM) with an additional multiplying layer (MLOS-ELM) was proposed. An extra multiplying layer was inserted between the hidden layer and the output layer, where the hidden layer outputs were multiplied by the input variables and state variables of the LPV model. Additionally, the input layer was set to the LPV model’s scheduling parameter. With the multiplying layer added, the state space equation matrices of the LPV model could be easily calculated using online gathered data. Simulation results showed that the outputs of the MLOS-ELM matched that of the component level model of a turbo-shaft engine precisely. The maximum approximation error was less than 0.18%. The predictive outputs o... [more]

Several modified terpolymer polyketones (MPK) with N-substituted pyrrole moieties in the main chain and quaternized amine in the side group were synthesized for use as anion exchange membranes for fuel cells. The moieties were carried by SiO2 nanoparticles through surface functionalization (Si−N), which were added to the membranes to enhance their overall properties. On increasing the amount of modified silica from 10% to 60% wt/of MPK, there was an increase in Si−N and a corresponding threefold increase in the hydroxide conductivity of the membrane. The MPK−SiN (60%) exhibited a superior ionic conductivity of 1.05 × 10−1 S.cm−1 at 120 °C, a high mechanical stability, with a tensile strength of 46 MPa at 80 °C. In strongly alkaline conditions (1 M KOH, 216 h at 80 °C), the membranes maintained about 70% of the conductivity measured in a usual environment. Fuel cell performance at 80 °C showed a peak power density of 133 mW·cm−2, indicating that using surface-functionalized SiO2 is a si... [more]

Condition monitoring and overheating warnings of the main bearing of large-scale wind turbines (WT) plays an important role in enhancing their dependability and reducing operating and maintenance (O&M) costs. The temperature parameter of the main bearing is the key indicator to characterize the normal or abnormal operating condition. Therefore, forecasting the trend of temperature change is critical for overheating warnings. To achieve forecasting with high accuracy, this paper proposes a novel model for the WT main bearing, named stacked long-short-term memory with multi-layer perceptron (SLSTM-MLP) by utilizing supervisory control and data acquisition (SCADA) data. The model is mainly composed of multiple LSTM cells and a multi-layer perceptron regression layer. By combining condition parameters into a characteristic matrix, SLSTM can mine nonlinear, non-stationary dynamic feature relationships between temperature and its related variables. To evaluate the performance of the SLSTM-ML... [more]

Sewage sludge is a residue of wastewater processing that is biologically active and consists of water, organic matter, including dead and living pathogens, polycyclic aromatic hydrocarbons, and heavy metals, as well as organic and inorganic pollutants. Landfilling is on the decline, giving way to more environmentally friendly utilisation routes. This paper presents the results of a two-stage gasification−vitrification system, using a prototype-entrained flow plasma-assisted gasification reactor along with ex situ plasma vitrification. The results show that the use of plasma has a considerable influence on the quality of gas, with a higher heating value of dry gas exceeding 7.5 MJ/mN3, excluding nitrogen dilution. However, dilution from plasma gases becomes the main problem, giving a lower heating value of dry gas with the highest value being 5.36 MJ/mN3 when dilution by nitrogen from plasma torches is taken into account. An analysis of the residues showed a very low leaching inclinatio... [more]

A series of experiments were performed to investigate the effect of ignition energy (Eig) and hydrogen addition on the laminar burning velocity (Su), ignition delay time (tdelay), and flame rising time (trising) of lean methane−air mixtures. The mixtures at three different equivalence ratios (ϕ) of 0.6, 0.7, and 0.8 with varying hydrogen volume fractions from 0 to 50% were centrally ignited in a constant volume combustion chamber by a pair of pin-to-pin electrodes at a spark gap of 2.0 mm. In situ ignition energy (Eig ∼2.4 mJ ÷ 58 mJ) was calculated by integration of the product of current and voltage between positive and negative electrodes. The result revealed that the Su value increases non-linearly with increasing hydrogen fraction at three equivalence ratios of 0.6, 0.7, and 0.8, by which the increasing slope of Su changes from gradual to drastic when the hydrogen fraction is greater than 20%. tdelay and trising decrease quickly with increasing hydrogen fraction; however, trising... [more]

Increasing the share of Renewable energy sources in District Heating (DH) systems is of great importance to mitigate their CO2 emissions. The combined integration of Solar Thermal Collectors (STC) and Thermal Energy Storage (TES) into existing Combined Heat and Power (CHP) systems can be a very cost-effective way to do so. This paper aims at finding the optimal design of STC and TES systems integrated in existing CHP’s considering two distinct objectives: economic profitability and environmental impact. To do so, we developed a three-stage framework based on Pareto-optimal solutions generated by multi-objective optimization, a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)-entropy method to select the optimal solution, followed by the definition of final Operation strategy. We proposed relevant improvement of the state-of-the-art models used in similar analysis. We also applied the proposed methodology to the case of a representative, 12 MWth CHP plant. Our res... [more]

This article is designed to demonstrate that electric roads are an affordable way to electrify all forms of road transport—not only cars, but also buses and trucks. Electric roads represent a way to power electric vehicles without relying solely on batteries. The idea is that when an electric vehicle reaches an electric road, it stops using power from the battery and instead uses power directly from the road itself. The primary challenge for electric vehicles is still the perception of a compromised quality of life in owning an electric vehicle due to a limited range compared with petrol and diesel cars, today. This paper introduces a new technology, currently experiencing rapid development, that can not only overcome range anxiety but make electric vehicles better, in terms of range, than petrol and diesel cars today. Furthermore, not only can this research help to arrange this, but it can also help, for the first time, to cost-effectively electrify heavy-duty transport, such as truck... [more]

Dimethyl ether (DME) is a promising alternative to diesel for compression-ignition (CI) engines used in various industrial applications. However, the high nitrogen oxide (NOx) emissions of DME combustion have restricted its use. The primary cause of high NOx emissions is a high combustion temperature. In this study, a high exhaust gas recirculation (EGR) rate was used when testing a common-rail direct injection CI engine suitable (with minor modifications) for a passenger car. A modified fuel supply system created high injection pressure during evaluation of combustion performance. The physical and chemical properties of DME were the principal determinants of the ignition delay, combustion speed, and heat release rate. Although a high injection pressure accelerated formation of the fuel-air mixture and the combustion speed, combustion performance deteriorated with increased NOx emissions. An increased EGR rate affected combustion and the NOx concentration. A high EGR rate effectively r... [more]

Renewable energies have been the only sources recording a clear increase in total installed capacity, setting a record in new power capacity in 2020, despite the pandemic. The European Union Green Deal represents a strategy towards a sustainable economic model. In this framework, land-based geothermics has seen very limited development; however, offshore geothermics is almost completely absent in the discussion on energy source alternatives, even though it represents a real challenge for energy transition, including the production of green hydrogen. This article discusses an excursus on the activities carried out on offshore geothermal areas worldwide. We focused on the energy potential capacity of the Marsili volcanic seamount located over the bathial plain of the Tyrrhenian Basin, describing the detailed geological, geochemical, and geophysical investigations that have been carried out on that seamount since the 2000s. All the collected data have shown evidence supporting the existen... [more]

One of the main sources of energy utilized in the Mongolian Gers is coal and wood mainly for the purpose of heating and other domestic use. This heavily increases the air pollution levels. A viable solution for handling the air pollution is switching to renewable energy sources (RES). Grid-connected photovoltaic (PV) systems with battery back-up provide a reliable solution to the problem addressing the energy demand and pollution control. This paper proposes a grid-connected PV−second-life battery system and its operation strategy. A single Ger, which consists of a PV array, battery energy storage system (BESS), and an electric heater (EH), is modeled and tested. The trading coefficient and selling unit price are calculated based on variables such as loan, selling price, and purchasing price. The advantages of the proposed strategy are its simple design and easy implementation. The economic result shows that there is a significant reduction in the electricity bill during winters, while... [more]

This study focused on the thermal degradation of peanut shells in the presence and absence of a termite hill as the catalyst. EDX, XRF, SEM, SAA and XRD were employed for the characterization of the termite hill. The bio-oil obtained from peanut shell pyrolysis was analyzed by GC-MS. To ascertain the kinetic parameters of the reaction, thermogravimetric analysis of peanut shells was carried out with and without a termite hill at heating rates of 3, 12, 20 and 30 °C·min−1. TG/DTG of peanut shells revealed four steps of weight loss from 30 to 800 °C. The weight loss was attributed to the evaporation of water and degradation of hemicellulose, cellulose and lignin. The Kissinger method was applied for the evaluation of kinetic parameters. The activation energy (E) for the non-catalyzed degradation reactions of hemicellulose, cellulose and lignin was evaluated as 108.082, 116.396 and 182.908 kJ/mol, with a pre-exponential factor (A) of 1.9 × 108, 2.42 × 109 and 2.98 × 1011 min−1, respective... [more]

Small-scale uncontrolled passive wind generator systems are an attractive solution for rural energy generation because of the system’s reliability and low cost. However, designing these uncontrolled wind generators for good power matching with the wind turbine is challenging and often requires external impedance matching. In this paper, permanent magnet generators with different stator and rotor structures were investigated and designed to increase the generator’s synchronous inductance for a natural impedance matching. For the design methodology, multi-objective optimisation was used to design the generators for near-maximum turbine power matching, whereby internal impedance matching was reached as much as possible. It was shown that altering the placement and orientation of the permanent magnets in the rotor is a viable method to achieve the desired impedance matching; however, these generators do not have the best performance. It was found that the surface-mounted permanent magnet g... [more]

The energy efficiency of road refrigerated transport is still a less researched area, despite a significant amount of energy being used for cooling perishable goods inside the refrigerated vehicle. The refrigeration units of these vehicles continuously operate while en route from the cargo sender to the recipient, even during the vehicle’s forced stopovers due to the driver’s working time limitations. This article aims to summarize the impact of the parking sheds used in rest and service areas on the energy consumption of the vehicle’s refrigeration unit. The achievable cost savings by decreasing the energy consumption of the semi-trailer’s refrigeration units are also presented. We establish a mathematical model to calculate the heat balance and verify our approach. The calculation results, which were carried out under certain operating conditions of the refrigeration unit of a semi-trailer, provide an opportunity to achieve savings on a scale of 12.03%. Lastly, ideal locations of res... [more]

To mitigate the fast-growing demand of electrical energy, the use of renewable energy resources, e.g., solar and wind, can offer an environmentally friendly and sustainable solution. Due to their intermittent nature, the grid connected operation of renewable energy resources provides a better performance compared to the standalone operation. However, the massive penetration of power electronic inverter/converter-interfaced renewable resources in power systems introduces new issues, such as voltage and frequency instabilities, because of their inherent low inertia properties. As a consequence, these issues may lead to serious problems, such as system blackouts. Therefore, there is an immediate demand to solve these new issues and ensure the normal performance of the power system with the large penetration of renewable energy resources. To achieve this, grid connected inverters/converters are designed to address these problems and behave as synchronous generators, which is possible with... [more]