Recently, the research interest regarding ammonia applications in energy systems has been increasing. Ammonia is an important hydrogen carrier that can also be obtained starting from renewable energy sources. Furthermore, ammonia can be used as a carbon-free fuel in combustion systems. In particular, the behavior of internal combustion engines (ICEs), fueled by ammonia, needs to be further investigated. The main disadvantage of this kind of fuel is its low laminar flame speed when it is oxidized with air. On the other hand, considering a spark-ignition (SI) engine, the absence of knock phenomena could allow a performance improvement. In this work, a 1D numerical approach was used in order to assess the performance and the operating limits of a downsized PFI SI engine fueled with pure ammonia. Furthermore, the reliability of the 1D model was verified by means of a 3D approach. Both throttled and unthrottled engine operation was investigated. In particular, different boost levels were an... [more]

Turbine inlet temperature has continuously increased to improve gas turbine performance during the past few decades. Although internal convection cooling and traditional film cooling have contributed significantly to the current achievement, advanced cooling schemes are needed to minimize the coolant consumption and maximize the cooling efficiency for future gas turbines. This paper conducts a comprehensive review of advanced effusive cooling schemes for gas turbine blades. First, the background and the history of turbine blade cooling are introduced. Then, the metrics of effusive cooling efficiency are defined. Next, effusion cooling, impingement/effusion cooling, and transpiration cooling are reviewed. The flow and heat transfer mechanisms of the cooling schemes are emphasized, and the design trends of the cooling schemes are revealed. Finally, the conclusions and future research perspectives are summarized.

In this work, we investigate the economic viability of demand response (DR) as a balancing option for variable renewable energies, such as wind and solar. Our assessment is based on a highly resolved national energy system model for Germany coupled with a regional DR optimisation model. First, this allows us to determine the spatially resolved flexibility demand, e.g., for avoiding transmission grid congestion. Second, a high number of DR technologies from the residential, commercial and industrial sector, as well as sector coupling, can be considered to cover the regional flexibility demand. Our analysis is based on a scenario for 2035 with a 66% share of renewable energy sources in the power generation. The results show that the largest DR capacity is being installed in the west of Germany, an area with a high density of population and industry. All DR units have an aggregated capacity below 100 MW per transmission grid node. For the economic assessment, we further differentiate betw... [more]

There are three main parts of an electric power system—power generation, transmission, and distribution. For electric companies, it is a tough challenge to reduce losses of the power system and deliver lossless and reliable power from the generating station to the consumer end. Nowadays, modern power systems are more complex due to gradually increasing loads. In the electrical power system, especially in transmission and distribution networks, there are power losses due to many reasons such as overloading of the line, long distribution lines, low power factors, corona losses, and unsuitable conductor size. The main performance factor of the power system is reliability. Reliability means continuity of the power supply without any interruptions from the generating station to the demand side. Thus, due to these power losses, there are voltage stability problems and economic losses in the electrical system. The voltage stability of the power system can be increased by improving the voltage... [more]

Among the many potential future energy sources, hydrogen stands out as particularly promising. Because it is a green and renewable chemical process, water electrolysis has earned much interest among the different hydrogen production techniques. Seawater is the most abundant source of water and the ideal and cheapest electrolyte. The first part of this review includes the description of the general theoretical concepts: chemical, physical, and electrochemical, that stands on the basis of water electrolysis. Due to the rapid development of new electrode materials and cell technology, research has focused on specific seawater electrolysis parameters: the cathodic evolution of hydrogen; the concurrent anodic evolution of oxygen and chlorine; specific seawater catalyst electrodes; and analytical methods to describe their catalytic activity and seawater electrolyzer efficiency. Once the specific objectives of seawater electrolysis have been established through the design and energy performan... [more]

Field operations report that at least half of the fracturing fluid used in shale reservoirs is trapped. These trapped fluids can trigger various geochemical interactions. However, the impact of these interactions on well performance is still elusive. We modeled a hydraulic fracture stage where we simulated the initial conditions by injecting the fracturing fluid and shutting the well to allow the fluids to soak into the formation. Our results suggest a positive correlation between the dissolution and precipitation rates and the carbonate content of the rock. In addition, we observed that gas and load recovery are overestimated when geochemical interactions are overlooked. We also observed promising results for sea water as a good alternative fracturing fluid. Moreover, we observed better performance for cases with lower-saline connate water. The reactions of carbonates outweigh the reactions of clays in most cases. Sensitivity analysis suggests that the concentration of SO4, K and Na i... [more]

The performance of a perovskite-based oxygen carrier for the partial oxidation of methane in thermochemical energy storage applications has been investigated. A synthetic perovskite with formula La0.6Sr0.4FeO3 has been scrutinized for Chemical Looping Reforming (CLR) of CH4 under fixed-bed and fluidized-bed conditions. Temperature-programmed reduction and oxidation steps were carried out under fixed-bed conditions, together with isothermal reduction/oxidation cycles, to evaluate long-term perovskite performance. Under fluidized-bed conditions, isothermal reduction/oxidation cycles were carried out as well. Results obtained under fixed-bed and fluidized-bed conditions were compared in terms of oxygen carrier reactivity and stability. The oxygen carrier showed good reactivity and stability in the range 800−1000 °C. An overall yield of 0.6 Nm3 of syngas per kg of perovskite can be reached per cycle. The decomposition of CH4 catalyzed by the reduced oxide can also occur during the reductio... [more]

Leading edge erosion (LEE) of wind turbine blades causes decreased aerodynamic performance leading to lower power production and revenue and increased operations and maintenance costs. LEE is caused primarily by materials stresses when hydrometeors (rain and hail) impact on rotating blades. The kinetic energy transferred by these impacts is a function of the precipitation intensity, droplet size distributions (DSD), hydrometeor phase and the wind turbine rotational speed which in turn depends on the wind speed at hub-height. Hence, there is a need to better understand the hydrometeor properties and the joint probability distributions of precipitation and wind speeds at prospective and operating wind farms in order to quantify the potential for LEE and the financial efficacy of LEE mitigation measures. However, there are relatively few observational datasets of hydrometeor DSD available for such locations. Here, we analyze six observational datasets from spatially dispersed locations an... [more]

Natural gum derived from the natural surrounding (gum arabic, guar gum, xanthan gum, gellan gum, fenugreek gum, karaya gum, and acacia gum) is one of the most abundant polysaccharides currently present around the world. As natural gum dissolved solution can be very sticky in nature, its role as a binder for both anodes and cathodes in rechargeable batteries have been recently significantly researched. Although much research has been delved into using natural gum as a feasible binder for rechargeable batteries, little investigation so far has taken place to compile, summarize, analyze, and evaluate the current status-quo of the natural gum-based binder research, as well as understanding some of the obstacles and issues that may need to be addressed. This review gives a comprehensive review on the natural gum-based binder that was used for both anode and cathode in rechargeable batteries and how each kind of natural gum improved the electrochemical performance in terms of cycle retention... [more]

Spark-ignited natural gas engines have received increasing attention in the heavy-duty market due to their low cost and reliability advantages. However, there are still some issues with natural gas engines retrofitted from 10 to 15 L diesel engines, which is a valuable medium-term goal for the automotive industry. In this work, the effect of intake port structure on the performance of a spark-ignited heavy-duty natural gas engine was investigated by multidimensional numerical simulations. A newly designed intake port was proposed, with strengthened in-cylinder turbulent kinetic energy and homogeneous air-fuel mixtures. Bench tests show that the proposed intake port has impressive thermal efficiency, cycle variation, and acceptable emissions performance. The effective thermal efficiency improves from 41.0% to 41.4%, and the cycle variation is 36% lower than traditional schemes. However, with the accelerated flame propagation, the in-cylinder temperature and NOx emission of the mixed-flo... [more]

The thermal management system of batteries plays a significant role in the operation of electric vehicles (EVs). The purpose of this study is to survey various parameters enhancing the performance of a heat pipe-based battery thermal management system (HP-BTMS) for cooling the lithium-ion batteries (LIBs), including the ambient temperature, coolant temperature, coolant flow rate, heat generation rate, start-up time, inclination angle of the heat pipe, and length of the condenser/evaporator section. This review provides knowledge on the HP-BTMS that can guarantee achievement of the optimum performance of an EV LIB at a high charge/discharge rate.

The article summarizes the results of the 25-year time horizon performance analysis of the ground source heat pump that serves as a heat source in a detached house in the climatic conditions that prevail in Wrocław, Poland. The main aim is to assess the potential of ground regeneration and reduction of CO2 emission by passive cooling application. The study adds value to similar research conducted worldwide for various conditions. The behavior of the lower source of the heat pump was simulated using EED software. The ground and borehole properties, heat pump characteristics, heating and cooling load, as well as the energy demand for domestic hot water preparation have been used as input data. Based on the brine temperatures for all analyzed cases including the ground with lower and higher values of conductivity and heat capacity, the borehole filler of inferior and superior thermal properties, and the passive cooling option turned on and off, the seasonal efficiencies of the heat pump h... [more]

Today, electricity tariffs play an essential role in the electricity retail market as they are the key factor for the decision-making of end-users. Additionally, tariffs are necessary for increasing competition in the electricity market. They have a great impact on load energy management. Moreover, tariffs are not taken as a fixed approach to expense calculations only but are influenced by many other factors, such as electricity generation, transmission, distribution costs, and governmental taxation. Thus, electricity pricing differs significantly between countries or between regions within a country. Improper tariff calculation methodologies in some areas have led to high-power losses, unnecessary investments, increased operational expenses, and environmental pollution due to the non-use of available sustainable energy resources. Due to the importance of electricity tariffs, the authors of this paper have been inspired to review all electricity tariff designs used worldwide. In this p... [more]

Water scarcity is a global issue recognized by the United Nations under Goal 6 of its Sustainable Development Goals (SDGs), which is to ‘Ensure availability and sustainable management of water and sanitation for all’. This challenging goal requires innovations, especially in areas with freshwater scarcity. Coupling this with the expected significant growth in population, especially in developing countries, presents major challenges to obtaining the appropriate levels of water provision needed. The development of seawater desalination technologies offers hope to alleviate freshwater shortages whilst supporting SDG 6. This research addresses the development of small-scale technology utilizing solar energy for providing clean drinking water in rural, hot, arid, and remote communities. To alleviate water scarcity in rural and isolated areas, a micro solar still (MSS) system that supports a multistage distillation process can be utilized, which evaporates and condenses the saline feed water... [more]

Because the road surfaces of the underground roadways in coal mines are slippery, uneven, with dust and water mist, and the noise and light illumination effects are significant, global positioning system (GPS) signals cannot be received, which seriously affects the ability of the odometer, optical camera and ultrasonic camera to collect data. Therefore, the underground positioning of coal mines is a difficult issue that restricts the intellectualization of underground transportation, especially for automatic robots and automatic driving vehicles. Ultra-wide band (UWB) positioning technology has low power consumption, high performance and good positioning effects in non-visual environments. It is widely used in coal mine underground equipment positioning and information transmission. In view of the above problems, this research uses the WLR-5A mining unmanned wheeled chassis experimental platform; uses two UWB receivers to infer the position and yaw information of the vehicle in the und... [more]

Higher carbon alcohols such as n-propanol, n-butanol, and n-pentanol that can be produced from biomass can be used as alternative fuels in diesel engines. These alcohols can mix with both diesel fuel and biodiesel without any phase separation. Currently, unregulated emissions such as toxicity and total polycyclic aromatic hydrocarbon (PAH) from the use of these alcohols are not monitored. Investigating the effects of increasing the alternative fuel concentration for use in a diesel engine on PAH emissions will contribute to the protection of the environment and extend the engine’s operating life. In this study, the effects of adding 35% (by volume) n-propanol, n-butanol and n-pentanol to diesel and biodiesel on unregulated emissions in a diesel engine were compared. In the total PAH emission of biodiesel, the mixture containing n-pentanol stood out compared to other mixtures with a decrease of 39.17%. In higher alcohol-diesel mixtures, the highest reduction was observed in the n-butano... [more]

Thermal efficiency and power density improvement are the main research foci of the literature on diesel engines. The Miller cycle is considered to be one of the most promising methods of diesel engine operation. In this study, a fully variable valve timing and lift mechanism (CD-HFVVS) was studied to determine the possibility of a Miller operation. Firstly, the valve seat impact buffer in the mechanism was tested, which proved that the buffer can effectively eliminate the valve seat impact. Then the influences of different speeds and oil temperatures were studied. The results show that the valve opening duration is prolonged when engine speed increases, and the valve lift and duration are reduced while the oil temperature increased. The valve timing and lift can be fully adjusted by changing the oil discharge position and the initial plunger position, which further proves that CD-HFVVS can achieve the performance optimization of the Miller cycle. By using the mechanism, a single cylind... [more]

This study reports on the structure analyses of NiO-BCZY (BCZY = BaCe0.54Zr0.36Y0.1O3-δ) anode composite materials with the ratio of 50:50 for proton ceramic fuel cells (PCFCs) application. A product of sintered NiO-BCZY was developed to understand the structural properties of the anode materials. The objectives of this work were (a) to investigate the lattice expansion of the anode by using a high-temperature XRD (HT-XRD) from 400−700 °C; and (b) to calculate the crystallite size of the sample by using Scherrer’s and Williamson Hall’s methods. The results obtained from the HT-XRD revealed that the diffraction peaks of NiO and BCZY are matched with the cubic phase perovskite structure. For example at T = 400 °C, the lattice parameter of NiO is a = 4.2004 Å and BCZY is a = 4.3331 Å. The observation also showed that the lattice expansion increased with the temperature. Furthermore, analyses of the Scherrer and Williamson Hall methods, respectively, showed that the crystallite size is str... [more]

There is a huge requirement for power systems to reduce power losses. Adding distributed generators (DGs) is the most common approach to achieving lower power losses. However, several challenges arise, such as determining the ideal size as well as location of the utilized distributed generators. Most of the existing methods do not consider the variety of load types, the variety and size of the utilized DGs besides reducing the convergence time and enhancing the optimization results. The paper performed an optimization algorithm that integrated a golden search-based flower pollination algorithm and fitness-distance balance (FDB) to find out the optimal size as well as the location of the distributed generators. It was then compared with different optimization methods to determine the best optimization technique, and it was determined to be the best technique. In addition, different types of DGs are considered, including solar energy, wind energy, and biogas, along with optimizing the si... [more]

Compared to mechanical compressors, ejector-based refrigeration systems can make direct use of many forms of thermal energy, including waste heat, solar thermal, or biogases. It is known that SE systems have a lower thermal efficiency compared to mechanical compressors because of their lower performance at high compression ratios. In the present work, binary fluid ejector heat pumps with high efficiency are presented based on a proper selection of the binary fluids and the ejector geometry for specific operating conditions of a ground-source heat pump cooling system (GSHP). The existing literature on ejector-based refrigeration systems considers the thermal COP and does not account for many energy losses across the system. In the present paper, the system COP of an ejector-based GSHP that accounts for all energy exchange processes is determined. A method for the calculation of the work done by the boiler feed pump, the refrigeration expansion valve, and the ground loop circulation pump... [more]

One of the best precursors for winter wheat is fallow. Its application aims to solve two important tasks: preserving and accumulating soil moisture and weed control. The authors of this paper have designed a new modular harrow for fallow tillage, which can work stably at a depth of 5−6 cm tillage while maintaining and even accumulating soil moisture. This article describes a method designed by the authors for a reasonable selection of the design parameters concerning the working devices mounted inside the new harrow, such as their length and working width, as well as the angles of vertical inclination (ε) and horizontal deviation (γ) of blades, depending on the accepted depth of the upper soil layer loosening. To reduce the soil tillage resistance of the harrowing unit resulting in a reduction in the tractor fuel consumption, the value of the inclination angle (ε) of its vertical blade should be chosen so that the corresponding change in the value of the deflection angle of the horizon... [more]

To mitigate the consequences of climate change, there is an increasing need to minimize the usage of fossil fuels, especially in the industrial sector because the majority of the industrial sector primarily rely on fossil fuels to meet their needs for heat energy, and a practical strategy to reduce reliance on fossil fuels is to use energy from the sun. Due to their environmental advantages, energy security, and viability as a potential substitute for fossil fuels, solar thermal collectors are acknowledged as promising technology to harness solar thermal energy fir process heating applications. This review is a thorough compendium and evaluation of contemporary literature on solar thermal collectors and their applications in industry. Apart from applications, this review paper also assesses the challenges and limitations currently hindering the global acceptance of this technology in the industrial sector.

Research over several years has shown that municipal engineering is an important source of humic substance formation (HS). Effluents from municipal landfills and digested sludge, due to high concentrations of organic pollutants, including HS and inorganic pollutants, are discharged to a biological treatment plant, where their largely non-biodegradable pollutants constitute a burden on the activated sludge and generate problems related to wastewater treatment. To demonstrate that humic substances, primarily soluble acids, are the carriers of micro-pollutants, their isolation was carried out from samples taken at different municipal management sites. The following analyses were performed: elemental composition, and the content of inorganic micropollutants, including heavy metals. In addition, the sorption affinity of pure HS to selected pharmaceuticals was investigated. The sorbed pharmaceuticals were Diclofenac and Estrone. HS commonly found in municipal engineering have been shown to b... [more]

With the recent developments in renewable energy generation and addition of power electronic devices, power system dynamics have become extremely complex. One of the challenges faced due to this transition is the sub synchronous oscillations caused by the interaction of renewable energy sources and various components of the power grid. Recently reported incidents due to sub synchronous oscillations highlight the need of monitoring and suppression of these harmful oscillations in real time. This paper gives an overview of the phenomena of sub synchronous oscillations and discusses the existing monitoring and damping techniques along with their limitations. Further, it highlights the research trends along this path.

The deployment of renewable energy (RE) needs to be policy-driven and supported by public funds. Hence, the aim of this study was to find out whether urban and rural areas benefit from public funds for RE deployment equally and whether factors determining other types of investments also determine investments in RES. To do so, we carried out: (i) comparative analyses of qualitative and quantitative data describing 2642 investments in solar RE supported by the European Union funds and carried out in Poland under operational programmes in 2014−2020; (ii) multiple linear regressions, evaluating the predictions. Findings showed that principles of supporting solar RE investments were the same for all kinds of beneficiaries in both urban and rural areas. However, in rural areas, most RE investments cumulated in eastern, north-eastern and south-eastern parts of Poland, and depended only on few socio-economic characteristics. RE investments in urban areas were dispersed all over the country rat... [more]