Journal of Energy Engineering

Integrating renewable energies into the electricity grid is a challenge that requires an in-depth investigation. This paper presents a model of the day-ahead electricity market, including wind and photovoltaic (PV) generators, and contingency analysis. The comprehensive day-ahead marketing model is designed as a modular structure so that the individual modules can be easily modified in the future. First, the day-ahead electricity marketing of an electricity grid with and without renewable energies is studied. A market model solves the problem of unit commitment and economic dispatch. A grid model was used to calculate the power flow of the branches and the grid losses. Congestions in the branches were handled by redispatching. For this purpose, the generators were redispatched using mixed-integer linear programming and the power transfer distribution factor. A contingency analysis, investigating the outage of one branch, was applied by using the line outage distribution factor. The redispatch process was operated with these calculated increased power flows, which need to be handled by the grid to achieve N-1 security. The simulations were carried out using 30-bus 118-bus systems. Historic wind speed and solar radiation data of Germany were used as input data for renewable energy production. The load data of the 118-bus system were generated based on a standard load profile from Germany. The results show that both systems were able to meet the demand without violation of the grid capacity during normal conditions, with and without renewable energies. However, when applying the contingency analysis, an outrageous amount of load curtailment is needed.

Photovoltaic (PV) module manufacturers specify their products’ performance under the standard test condition. However, such a condition is hardly found outdoors, that is, during actual operation of photovoltaic systems. Despite that, many modeling methods proposed in the literature rely on standard test condition data for parametric identification. This paper presents an experimental study concerning different modeling approaches for photovoltaic modules, focusing on assessing model performance in different scenarios. The goal is to assess the influence of the data used for the model parametric adjustment when predicting the maximum power point of two photovoltaic modules, allowing the most advantageous methods to be identified. By using an experimental outdoor photovoltaic platform, over 30,000 I-V curves referring to two photovoltaic modules were measured for 16 months. Different models were applied for cases where their parameters were identified using field measurements. It was found that using measurements obtained under real operating conditions to adjust the model parameters provides significantly better prediction of the maximum power in comparison to cases employing data sheet-extracted information. For the all methods and cases studied, using in-field measurements to adjust the model parameters provided average root-mean-square error of 3.4% for power predictions, whereas the average error level found when using data sheet information was 8.8%. An error level as low as 2.83% was reached by adopting the most complex model, although using a significantly simpler modeling approach provided error of 3.25%. Therefore, using field-measured data to adjust model parameters produced the best results, but increasing method complexity did not increase performance in the same scale.

To solve the problems of high pollutant emission of traditional diesel tractors and short continuous operation time of pure electric tractors, a new tractor powertrain system model with a fuel cell as the primary energy source, battery as the auxiliary energy source, and electric motors as the power source is developed. The fuel cell, battery, and degradation models are constructed. A rule-based control strategy is designed to distribute the current between fuel cell and battery, maximizing the benefits of the fuel cell and battery in the energy management process by differentiating the quadratic utility function and combining the Karush-Kuhn-Tucker (KKT) conditions. Finally, the optimal weight coefficient in the strategy is obtained through the Nash equilibrium. The simulation results show that the designed energy management strategy can adequately maintain the battery state of charge (SOC), reduce the performance degradation of the fuel cell, and improve the tractor’s ploughing mileage. The tractor is equipped with 960 g of hydrogen, the initial SOC is 90%, and it can operate continuously for 2.8 h.

Biomass from agricultural production is a renewable energy source with a high-volatile content. Semicoke (SC) and gasification residual carbon, which are ultralow volatile carbon-based fuels (LVFs), are by-products of the coal chemical industry, which are over capacity and urgently need to be cleanly and effectively consumed. Biomass and LVFs exhibit complementary fuel characteristics, particularly the volatile content, which can potentially be coprocessed efficiently. Furthermore, oxyfuel combustion technology can not only realize carbon dioxide (${\mathrm{CO}}_2$) capture and benefit from carbon neutrality, but also effectively reduce ${\mathrm{NO}}_x$ emissions. The cocombustion of biomass and ultralow volatile fuel under oxyfuel conditions can both use individual benefits and effectively control pollutant emissions. However, the cofiring characteristics and interaction mechanisms of LVF with biomass in an oxyfuel atmosphere are yet to be fully understood. In this study, three ultralow volatile fuels and one typical biomass were selected to explore the oxyfuel cocombustion characteristics via thermogravimetric experiments. The experimental results indicated that blending with wheat straw (WS) improved the overall combustion performance, the ignition point was close to that of WS, and the burnout temperature was close to the average value of the two individual fuels. An increase in the oxygen content can effectively enhance the combustion feature of ultralow volatile fuels while it has little effect on the burnout performance of biomass. In the presence of high-content ${\mathrm{CO}}_2$, the decomposition of carbonate in ultralow volatile fuel is impeded and the decomposition temperature is slightly increased. The present investigation can promote the efficient co-utilization of inferior LVFs and biomass, which also benefits ${\mathrm{CO}}_2$ capture, carbon neutrality, and even negative carbon emissions.

This paper discusses the influence of passive façade design of a detached residential building on its energy performance. The research consists of a parameter analysis performed using commercially available software to assess the influence of different façade wall structures, glazing types, and window-to-wall ratios (WWRs) on the energy required for heating and cooling of a detached building with a sunspace. Eighteen variants of façade wall structure (W1–W18) and 20 variants of façade window glazing type (G1–G20) were created for the base model of a building with a sunspace (Model-FW) for the purpose of investigating their influence on energy consumption in the building. All variants of the base model were examined for $\mathrm{WWR}=20\%$, $\mathrm{WWR}=40\%$, and $\mathrm{WWR}=60\%$. The research was conducted for the location of the urban area in the city of Niš, Serbia. The analysis of the results showed that the best-performing façade wall structure in terms of heating energy consumption was Variant W1, which consists of a 0.40-m-thick concrete layer, 0.14-m-thick expanded polystyrene (EPS) thermal insulation layer, and a render/plaster layer on the outside and the inside with the total thickness of 0.03 m. The W1 variant had the largest thermal mass and thermal insulation thickness of all considered variants. Regarding the total energy required for heating and cooling, in the most favorable W1 model, the energy savings were 75.14% ($\mathrm{WWR}=20\%$), 35.04% ($\mathrm{WWR}=40\%$), and 17.15% ($\mathrm{WWR}=60\%$). The analysis of different glazing types showed that triple low-emissivity glazing performed the best in terms of heating energy required for a building with a sunspace. Among the considered models, benefits from triple glazing systems in terms of total energy consumption were 41.59%, 61.04%, and 47.70% for $\mathrm{WWR}=20\%$, $\mathrm{WWR}=40\%$, and $\mathrm{WWR}=60\%$, respectively.

Understanding the two-phase flow within multiple channels in a proton-exchange membrane fuel cell (PEMFC) is important to improve cell performance. In this study, the droplet behavior in multiple channels is predicted by the volume of fluid (VOF) method. In addition, the pressure drop and velocity and pressure distribution between the multiple channels are analyzed, and the effects of channel wettability, gas velocity, and structure parameters on the two-phase distribution within the multiple channels are investigated. The effect of different parameters on the droplet detachment time in multiple channels is evaluated by comparing the droplet movement time. The results show that the increase in amplitude and period leads to greater improvement in the water removal performance of the multiple channels. Additionally, the unevenness within the multiple channels is improved as the interval between channels decreases. The channels show better water removal performance at a channel period of 4, an amplitude of 1.2 mm, and an interval of 1 mm. With the lowering of the wall contact angle, the broken droplets tend to accumulate at the wall corners, and the time for the droplets to be removed increases significantly. It is also observed that as the inlet velocity increases, droplet breakup is more likely to occur in the third channel. At larger flow rates, the droplet detachment time from the channel decreases to some extent in all three channels, but the droplet detachment order is different due to the unevenness of the flow distribution of the two-phase flow in the multiple channels compared to a single channel. Therefore, this unevenness in the flow distribution is the cause of the different droplet detachment orders in the three channels. This study is important for the design of the flow channel and water management of the PEMFC.

The rapid development of gas turbine (GT) and power-to-gas (P2G) technology promotes the integration of power systems (PS) and natural gas systems (NGS). To accurately describe the state distribution, this paper first introduces the model of integrated gas and power system (IGPS) governed by nonlinear partial differential-algebraic equations (PDAEs). A third-order method of lines (MoL) is proposed to solve the nonlinear partial differential equations (PDEs) in the natural gas system. The distribution of mathematical equations and variables in the energy flow model is then analyzed. The solution strategy for nonlinear dynamic energy flow calculation (EFC) in integrated gas and power system is then developed, including the equation set formulation, solvability analysis, and initial guess selection method. Finally, the accuracy and efficiency of the proposed method are verified through simulation in two different cases.

Earthquakes and other natural disasters have caused significant damages to power systems, indicating the necessity to enhance power system resilience. This paper proposes a risk-based resilience enhancement framework against earthquakes that considers their stochastic nature. The proposed framework supports the decision-making of distribution system operators (DSOs) for retrofitting substation components and underground cables to enhance distribution system resilience. The framework consists of four phases, namely earthquake modeling, vulnerability assessment, risk assessment, and resilience enhancement. An attenuation relationship is used to model the earthquake characteristics. Vulnerability assessment includes the failure probability calculation of substation components and a fault-tree method application to examine the seismic vulnerability of the substation. Conditional value at risk (CVaR) is used to assess the seismic risk, and includes the estimation of repair cost and customer interruption cost due to the damage caused by the earthquake, as well as the power generation cost of the distributed energy resources (DERs) used to meet the demand locally. A modified risk reduction worth (RRW) metric is adopted to determine the optimal retrofitting strategy to enhance resilience. The proposed framework was applied to a real distribution substation to examine the effectiveness of substation component retrofitting for resilience enhancement.

Production strategies and parameters control the efficiency of geothermal energy extraction related to the thermal stability and economic benefits of a geothermal system. The optimization strategies of geothermal energy extraction play a critical role in engineering and are generally determined through a numerical simulation approach. Considering the correlation among production parameters, numerical simulation requires numerous runs and manual adjustments, resulting in lower calculation efficiency and limited or local optimizations. This study proposes a high-efficiency network based on a three-dimensional heterogeneity model in the Gonghe Basin in China to achieve a high-efficiency and high-precision production strategy. The neural network was successfully established as a surrogate of the numerical model for the repetitive forward simulation. Meanwhile, the neural network is integrated with the Harris Hawks algorithm to optimize extraction strategies for sustainable heat extraction. This paper focuses on the effects of human-controlled operational parameters on geothermal systems. Results indicated that the maximum electrical power can be guaranteed 5.2 MW during a 50-year production period at an injection temperature of 60°C, an injection rate of $39\mathrm{kg}/\mathrm{s}$, and a well spacing of 380 m. The study provides important operational guidance for sustainable utilization in the Gonghe Basin. This simulation-optimization approach can be applied to other geothermal sites for sustainable energy production.

The aerodynamic performance of a National Renewable Energy Laboratory Phase VI horizontal-axis wind turbine (HAWT) equipped with blades characterized by leading-edge suction and blowing was analyzed numerically in three dimensions using computational fluid dynamics. The effects of leading-edge suction and blowing flow control methods on the flow field and aerodynamic characteristics of the HAWT and its performance were compared. The results suggest that leading-edge suction is superior to leading-edge blowing in suppressing the flow separation on the suction side of the turbine blade and improving the turbine aerodynamic characteristics. However, compared with the baseline turbine, the bending moment acting on the rotating blade of the HAWT to which suction or blowing is applied increased. This increment was greater for turbines with leading-edge blowing flow control blades. The effects of different arrangements of suction slots on the performance of the HAWT were analyzed. The results showed that the net wind power coefficient of the HAWT after deducting the energy consumption of the suction control was 45% higher than that of conventional turbines, indicating great potential for practical applications.

This paper assesses the dynamic thermal inertia performance of unfired clay bricks with dry-grass fiber additives. The used raw material was retrieved from Ifrane in Morocco. The used clay was illite with a 59.60% silicon proportion. Multiple percentages (0%, 1%, 7%, and 15%) were analyzed in this study. The dynamic thermal inertia simulation was carried out in TRNSYS software to investigate the specimens’ time lag, decrement factor, and heating and cooling loads. For this purpose, a reference house with three different wall thicknesses (0.20, 0.25, and 0.30 m) was evaluated. Collected findings reflected great time lag improvements. With the incorporation of 15% additive, 13.11 h was recorded. This reflected a thermal gain of 49.12% with the use of 0.30-m-thick walls. Decrement factor analysis also recorded interesting improvements. Thermal cooling and heating loads also recorded prominent energy savings of 95% and 60%, respectively. Finally, adopting thicker building walls recorded great thermal gains in the range of 60%.

There are many mature oil fields in the North Sea. One of them is the Clair Oil Field, located on the United Kingdom Continental Shelf (UKCS) in Scotland. This oil field is unique because of the results of failure studies of several fluid injections, constituting secondary and tertiary oil recovery techniques, on increasing oil production. Only waterflooding has shown a promising future. In this paper, three-dimensional (3D) numerical simulations investigate the influence of infill drilling optimization by waterflooding in the Clair Oil Field so as to maximize net present value (NPV). An important goal of this study of reservoir management was to determine optimal well locations and optimal operational parameters (production constraints) that maximize cumulative oil production. Theoretical ideas and mathematical models with field data performance demonstrated the factors that can be considered in infill drilling so as to increase oil reserves. Most of the factors were related to reservoir heterogeneities and were important quantitatively for fluid injection and production. The results revealed that the four infill wells added in this study led to an increase in the field’s total cumulative oil production from $7.91\times {10}^6$ to $9.39\times {10}^6{\mathrm{m}}^3$. The NPV after infill drilling optimization by waterflooding increased by 54.4% over the base case. The oil recovery factor rose from 17.2% to 20.2%, while the gas oil ratio (GOR) fell from 1,000 to 840 SCF/STB. After combining infill drilling with waterflooding, the horizontal infill producers outperformed vertical infill producers by 5.5%. The field water cut was reduced from 95% to 88%. In addition, an analysis of cumulative production between parent and child wells was made. It was found that child wells produce less cumulative oil production than do parent wells. This paper reveals the greater success of a combination of infill drilling with waterflooding in enhancing oil production compared to other findings where the influence of infill drilling and waterflooding were analyzed separately or compared. It can be concluded that the Clair Oil Field has great potential to increase oil production by combining infill drilling with waterflooding, after other improved oil recovery techniques fail.

The optimization of energy management strategy (EMS) for fuel cell electric vehicles (FCEV) is mainly applied to reduce fuel consumption. However, serious power fluctuations affect the durability of the fuel cell, which is still a challenge for the FCEV. In order to optimize the fuel cell’s service life and economy, this paper proposes an EMS scheme based on fuzzy control. In the proposed EMS, the first layer uses the power following strategy to address the output power distribution issue between the battery and the fuel cell. In order to limit the rapid shift in fuel cell power, the second layer employs a fuzzy control method. Considering the variety of constraints, such as fuel cell power fluctuation and hydrogen consumption, the particle swarm optimization algorithm is used to optimize the membership function of the fuzzy controller. The performance and the operating characteristics of the fuel cells are then evaluated using a test bench. Afterward, the proposed EMS is verified by AMEsim joint simulation. The optimized strategy increased the driving range by 4.7% and 5.9% in world light vehicle test cycle (WLTC) and new European driving cycle (NEDC) conditions, respectively. It also reduces the fuel cell degradation by 21.4% and 19.8%.

Abstract

Solar energy is a type of renewable energy that is readily available, but it must be converted to a usable form using a highly efficient method. The global energy problem that has surfaced in recent years shows the importance of both practical and scientific studies on using solar energy for space heating. Solar air heaters are large volume systems used for space heating. Research on the geometry and surface forms of solar air collectors is focused on reducing system volume and optimizing the use of solar energy. A photovoltaic (PV) module can be cooled with a fluid to prevent a decrease in efficiency due to heat while generating electrical power. The subject of this study is the idea of using the heat from cooling the modules to support a solar air heater. The improvement of the thermal performance of a solar air collector with a cooling thermal load of the concentrated photovoltaic thermal collector (CPV/T) was experimentally investigated. The heat exchanger, which removes the heat of the water-ethylene glycol circulating in the photovoltaic thermal collector, is mounted in the solar air heater’s chamber of one of the two identical solar air heaters, and the first hybrid unit was obtained (i.e., first unit). The ordinary one was called the second unit. Heated air left the first and second units at average temperatures of 45.87°C and 38.83°C, respectively. Although the airflow rates in the units are the same, the air temperature in the first unit was increased by 18.13%. The heat contribution of the heat exchanger to the first unit was 128.96 W. The first and second law efficiencies of the first and second units were calculated as 51.89%, 15.22%, and 45.4%, 10.34%, respectively. The energetic and exergetic improvement of the first unit was found to be 6.49% and 4.88%, respectively. The local solar utilization capability is $797.76\mathrm{kW}·\mathrm{h}/\mathrm{year}$ and $609.12\mathrm{kW}·\mathrm{h}/\mathrm{year}$ for the first and second units, respectively. The waste heat from the CPV/T collector cooling cycle, which is $188.64\mathrm{kW}·\mathrm{h}/\mathrm{year}$, was recovered for heating air in the first unit. The recovery of waste heat for use in the first unit provided a significant performance improvement over the second unit. The environmental contribution of the waste heat recovery means 144 kg ${\mathrm{CO}}_2$ emission per year less in emission release.

Practical Applications

This study addresses the process of supporting the performance of a solar air heater with the waste heat obtained during the liquid cooling application of a CPV/T collector. The heat exchanger of a closed loop that cools a CPV/T collector was placed in the solar air heater’s chamber of the first solar air heater unit. The heat released from the heat exchanger increased the unit’s heating capacity. The improvement achieved with the first unit compared to the second unit is evaluated by comparing it to the second unit but without a heat exchanger attachment. While solar utilization in the first unit reached 525.19 W, the second unit provided 401 W of solar utilization. The energy and exergy values of the first and second units were found to be 51.89%, 15.22%, and 45.4%, 10.34%. When evaluating the use of solar energy instead of fossil fuel-based heating applications, it is predicted that the local gain can be $767.76\mathrm{kW}·\mathrm{h}/\mathrm{year}$ and $609.12\mathrm{kW}·\mathrm{h}/\mathrm{year}$. In recent years, active cooling of PV modules is a popular method to prevent a decrease in module efficiency due to a rise in the PV module temperature. Gaining use of the thermal load removed from the PV module is another well-known subject. In this study, $188.64\mathrm{kW}·\mathrm{h}/\mathrm{year}$ of thermal load from the CPV/T collector was recovered to the heating air in the first unit. In this way, the efficiency of the first and second laws of the first unit increased by 6.49% and 4.88%, respectively, compared to the second unit. The idea of the hybrid solar air heater contributes to researchers working in this field and raises awareness among practitioners.

For a fuel cell range-extended electric vehicle (FC-REEV), the fuel cell system can work at a fixed output power point, and it has high durability. However, the differences in output power and start–stop threshold can lead to a significant difference in energy loss and degradation of power sources. Based on the thermostat control strategy (TCS), the state of charge (SOC) of the battery is stabilized within a reasonable range. To obtain the lowest hydrogen consumption rate, the vehicle’s fuel economy is considered in the evaluation function. The artificial bee colony (ABC) optimization algorithm is then used to increase the driving range, and the conventional ABC-TCS (CABC-TCS) is proposed. However, the CABC-TCS leads to many start–stop times for fuel cells. To enhance the durability of the fuel cells, a penalty factor was added to the evaluation function, and a novel optimized ABC-TCS (OABC-TCS) is proposed. Different strategies were tested under federal test procedure (FTP)-72 and worldwide light-duty test procedure (WLTC) driving cycles. The results show that, compared with TCS, the optimized driving range of OABC-TCS in FTP-72 and WLTC conditions increased almost 10.59% and 10.3%. Compared with CABC-TCS, the start–stop times of OABC-TCS in FTP-72 and WLTC conditions decreased by 27.55 and $46.47\mathrm{times}/\mathrm{h}$, respectively.

According to the European Union, buildings account for 40% of overall energy use and 36% of ${\mathrm{CO}}_2$ emissions, with existing energy-inefficient buildings the main source of losses. Efforts to enhance the thermal comfortability of users in buildings can result in overheating if not appropriately designed, which in turn could lead to health issues as well as continual emission of greenhouse gases. To provide further insights into this dilemma and contribute to improving energy-efficient building designs, we undertake a new modeling technique encompassing a complete analysis of the existing building 3D model as well as solar radiation behavior on buildings. The technique involves 3D building information modeling (3D BIM) that is reconstructed using computer-aided design (CAD). Ladybug and Honeybee plugins for Grasshopper for Rhino are then used to evaluate environmental and building performance using the energy plus weather (EPW) file of Wuhan city, China, as a case study. An assessment of ‘with’ and ‘without’ built architectural surroundings contexts is also carried out in relation to summer and winter solstices. An overall change of approximately 29.56% is observed between ‘with’ and ‘without’ surrounding contexts, which suggests that both have a significant influence on the solar potential of individual buildings. Investigation of internal and external thermal energy consumption behaviors in relation to building comfort lead us to suggest an optimized smart solution which is validated using our case study site in Wuhan. Our findings suggest that the building energy lifespan can be increased while reducing environmental consequences if an estimated 50% of monthly energy savings are made. The findings of this study provide useful insights for decision-makers, engineers, and designers of energy-efficient buildings.

The effect of two mechanisms that contribute to the cyclic variability of a spark-ignition (SI) engine fueled with lean methane–hydrogen blends was examined. This assessment was performed using a research computational fluid dynamics (CFD) code, employing a fast methodology that allowed the simulation of several cases (three per mechanism and per case) and thus greatly reduced the computational time. The first mechanism is related to the local gas turbulent properties at the spark plug, and the second mechanism is related to the fuel mass variation per cycle. The engine performance and emissions results were processed using a linear regression approach, and then using a Monte Carlo–based approach to extract the main indicators such as the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) for each individual mechanism as well as for their combination. It was found that the contribution of the first mechanism is significant and it mainly affects the initial flame propagation process. On the other hand, the second mechanism affects the equivalence ratio and subsequently the whole combustion process with a high variability of CO emissions, and its uncertainty was accounted for by expanding its range.

In order to study the temperature distribution in a lithium-ion battery (LIB), a series of experiments including open-circuit voltage (OCV) test, discharge rate test, hybrid pulse power characteristic (HPPC) test, and discharge temperature rise test based on the Bernardi heat generation model were conducted. The thermal model (TM) of the LIB under different discharge rates was established. The temperatures of the cell at different discharge rates calculated by the TM, which leverages the user-defined function (UDF) to import a variable heat generation rate, were compared with the experimental data. Moreover, this TM was used to simulate the LIB temperature at different ambient temperatures and different heat-transfer coefficients and analyze the temperature distribution of cell. The results showed that the TM can accurately simulate the temperature rise of the LIB at different discharge rates, which provides a reference value for LIB thermal management.

Solar chimneys have been applied widely to various buildings under different climate conditions because of their superiority in improving the indoor environment and saving energy. A series of comparative studies of the performance of solar chimneys used in 12 cities in China under different climatic conditions was carried out. A typical solar chimney in a representative building was studied using numerical simulation and analyzed using orthogonal experiment methods. Results show that the optimal structural configuration and the significance of influencing factors of the solar chimney have strong seasonal consistency. The window-to-wall ratio and wall-to-south wall ratio are the most significant influencing factors. Among the 12 cities, the highest average indoor temperature of the case room could be decreased by 5.7°C in summer and increased by 6.7°C in winter. The cooling and heating loads could be reduced by 30%–100% and 46%–56% respectively. The research results can provide practical guidance for future passive solar technology design.

This study examines the spray characteristics of biodiesel, diethyl carbonate (DEC), and their mixtures in a common-rail injection system. Using the schlieren method, the spray tip penetration, spray cone angle, spray tip velocity, spray area, and spray liquid core ratio were observed with a high-speed camera. The test results show that the spray pressure and ambient pressure have significant effects on the spray characteristics. Increasing the spray pressure and decreasing the ambient pressure can increase the spray tip penetration, decrease the spray cone angle, and increase the spray area. After the addition of DEC to biodiesel, with increasing the mixing ratio, the viscosity and surface tension of the mixed fuel are reduced, but the density is increased. This increases the spray cone angle and spray area of the mixed fuel, and it reduces the Sauter mean diameter (SMD). The SMD of droplets were calculated, and it was found that DEC30 has the smallest SMD, and it is of the same order as that of diesel. An improved calculation model for the spray tip penetration of the DEC and biodiesel mixture under high injection pressure was obtained by modifying the exponent of an existing model. By comparing the linear relationship between the injection pressure and the spray tip penetration, it was found that the spray tip penetration of DEC10 has the largest increase.