The durability of automotive fuel cells is one of the main factors restricting their commercial application. Therefore, establishing a remaining useful life (RUL) prediction model and developing an online operational method to apply it to the RUL optimization of fuel cell vehicles is an urgent academic problem. In this work, a short-term RUL prediction model and an online operation scheme for fuel cell vehicles are proposed. Firstly, based on historical data of a fuel cell bus under multiple conditions, the daily mode of stack voltage under a 75 A operation condition was selected as a health indicator that could better reflect the health status of a fuel cell stack. Then, an adaptive locally weighted scatterplot smoothing (LOWESS) algorithm was developed to adjust the most appropriate step size to smooth the original data automatically. Furthermore, for better prediction accuracy and stronger adaptability, a short-term RUL prediction model consisting of the adaptive LOWESS and bi-direc... [more]

In early 2020, Indonesia implemented the biodiesel 30 (B30) program as an initiative to reduce Indonesia’s dependency on fossil fuels and to protect Indonesia’s palm oil market. However, palm oil has received international criticism due to its association with harmful environmental externalities. This paper analysed whether an investment in palm oil-based biofuel (POBB) provides Indonesia with the ability to achieve its environmental and financial goals. In this research, we performed a meta-analysis on biofuel energy return on investment (EROI) by examining 44 biofuel projects using ten types of biofuel feedstocks from 13 countries between 1995 and 2016. Results showed an average EROI of 3.92 and 3.22 for POBB and other biomass-based biofuels (OBBB), respectively. This shows that if only energy inputs and outputs are considered, biofuels provide a positive energy return. However, biofuels, including those from palm oil, produce externalities especially during land preparation and land... [more]

The northern part of the globe is dominated by industrialisation and is well-developed. For many years, the southern part of the world (South Asia, Africa etc.) has been a target of research concentrating on access to energy (mainly electricity) in rural regions. However, the Central Asian region has not been a focus of energy research compared to South East Asia and Africa. Despite plentiful domestically available energy resources, the energy supply in Central Asia is very unevenly distributed between urban and rural areas. Almost half of the total population of Central Asia lives in rural areas and there is a lack of access to modern energy services to meet primary needs. To analyse the energy situation (i.e., electricity, heating, hot water consumption, cooking, etc.) in rural Central Asia, this paper reviews residential energy consumption trends in rural Central Asian regions as compared to urban areas. Furthermore, the paper illustrates the potential of renewable energies in Centr... [more]

Solar irradiation data collected at the latitude of Milan city, near the 45th parallel North, and original activity data of some high-performing photocatalysts (i.e., commercial TiO2 P25, TiO2 prepared by flame spray pyrolysis, 0.2% wt/wt Au/P25) have been used to evaluate the feasibility and the efficiency of an ideal solar photoreactor for the CO2 photoreduction in liquid phase. The best theoretical performance was achieved with commercial bare P25 titania, despite the fact that it was the material with the widest band gap (3.41 eV vs. 3.31 for FSP and 3.12 for Au/P25). In that case the efficiency of energy storage was calculated as about 2% (considering the total irradiated solar energy) and ca 18% (considering only the UV fraction of solar irradiance). Most of the energy content of the products was stored as formic acid, which would return a productivity of about 640 kg/year kgcat under daylight solar irradiation considering the variance of the irradiance data. Bare FSP titania gav... [more]

A model of a fluidized bed coupled with direct carbon solid oxide fuel cell (SOFC) is developed to explore the effect of coupling between fluidized bed and solid oxide fuel cell. Three gas−solid flow regimes are involved including fixed bed, delayed bubbling bed and bubbling bed. The anode reaction of SOFC is treated as the coupling processes of Boudouard gasification of carbon and electrochemical oxidation of CO. The effects of inlet velocity of the fluidizing agent CO2, carbon activity, channel width and coupling extent on the system performance are investigated. The results show that the inlet velocity of CO2 can promote the gasification rate in the anode, but too high velocities may lower CO molar fraction. The gasification rate generally increases with the increase of the channel width and carbon activity. The overlapping area between the anode surface and the initial carbon bed, gas−solid regime and carbon activity have a significant influence on the gasification rate and the max... [more]

In this paper, a windowed receiver with a particle curtain is numerically simulated under full-spectrum conditions. The discrete phase model (DPM) is used to model the particle flow and interactions between the particle phase and the air phase. The scattering, absorption of the particle curtain and quartz glass window are considered in detail. The spectral characteristics of glass have an important influence on the heat transfer characteristics and the receiver efficiency. The results show that the quartz window can reduce the convective heat loss and the cavity re-radiation heat loss. Under the same conditions, the receiver efficiency of a windowed receiver with a particle curtain is increased by 11.9% compared with an aerowindow receiver with a particle curtain. Under the same mass flow, the particle curtain thickness and particle size have a non-negligible influence on the flow pattern and temperature distribution of the particle curtain. When the particle curtain thickness is low,... [more]

This paper aims to evaluate the impact of cetane improvers on the combustion, performance and emission characteristics of a compression ignition engine fueled with a 20% peppermint bio-oil/diesel blend (P20). It is hypothesized that the low viscosity and boiling point of peppermint oil could improve the atomization characteristics of the fuel. However, the usage of peppermint oil is restricted due to its low cetane index. To improve this, Diethyl Ether (DEE) and Di- tertiary Butyl Peroxide (DTBP) are added to the P20 blend. The tests are performed in a single-cylinder naturally aspirated water-cooled diesel engine and results indicate that NOx emission for P20 + DEE and P20 + DTBP is decreased by 10.4% and 9.8%, respectively, when compared to P20 at full load condition. Among these two cetane improvers, DTBP is more effective in reducing the CO, HC and smoke emission and the performance of the engine was reported to be higher for P20 + DTBP blends.

All-electric buildings are playing an important role in the electrification plan towards energy-neutral smart cities. Batteries are key components in all-electric buildings that can help the demand-side energy management as a flexibility asset and improve the building survivability in the case of power outages as an active survivability asset. This paper introduces a novel methodology and indexes for determining cost-effective battery sizes. It also explores the possible trade-off between energy flexibility and the survivability of all-electric buildings. The introduced methodology uses IDA-ICE 4.8 as a building performance simulation tool and MATLAB® 2017 as a post-processing calculation tool for quantifying building energy flexibility and survivability indexes. The proposed methodology is applied to a case study of a Norwegian single-family house, where 10 competitive designs, 16 uncertainty scenarios, and 3 dynamic pricing tariffs suggested by the Norwegian regulators are investigat... [more]

The article presents the results of research on the influence of two fuel additives that selectively affect the combustion process in a diesel engine cylinder. The addition of NitrON® reduces the concentration of nitrogen oxides (NOx), due to a reduction in the kinetic combustion rate, at the cost of a slight increase in the concentration of particulate matter (PM) in the engine exhaust gas. The Reduxco® additive reduces PM emissions by increasing the diffusion combustion rate, while slightly increasing the NOx concentration in the engine exhaust gas. Research conducted by the authors confirmed that the simultaneous use of both of these additives in the fuel not only reduced both NOx and PM emissions in the exhaust gas but additionally the reduction of NOx and PM emissions was greater than the sum of the effects of these additives—the synergy effect. Findings indicated that the waveforms of the heat release rate (dQ/dα) responsible for the emission of NOx and PM in the exhaust gas diff... [more]

In this paper, the integration of the dynamic behavior of the flywheel system into the load simulation tool OpenFAST is presented. The flywheel system enables a wind turbine to vary the inertia of its rotor blades to control the power production and, most importantly, to affect the vibratory behavior of wind turbine components. Consequently, in order to simulate the behavior of a wind turbine with a flywheel system in its rotor, the variable blade characteristics need to be considered in the load simulation tool. Currently, computer-aided engineering tools for simulating the mechanical loads of wind turbines are not designed to simulate variable blade inertia. Hence, the goal of this paper is to explain how variable inertias of rotor blades are implanted in such load simulation tools as OpenFAST. OpenFAST is used because of it is free, publicly available, and well documentation. Moreover, OpenFAST is open source, which allows modifications in its source code. This add-on in the load si... [more]

The paper deals with the determination and compensation of non-active torques of parallel HEV using an auxiliary electrical PMSM or IM motor. The non-active oscillating torque generating by the ICE engine was estimated, and consequently, the compensating torque component of the current was determined. Based on real measured data, the four regimes of operation have been investigated: compensating non-active torques, parallel operation, regenerating for PMSM, and both parallel operations, together with compensation. Using of p-q theory, the power of fundamental harmonic is presented by average values PAV, QAV of total power waveforms p(t), and q(t). Worked-out simulation results are used for sizing and dimensioning of PMSM machine, VSI inverter, and traction accumulator-battery. Circuit simulator Matlab/Simulink was used for all simulation experiments.

Plummeting reserves and increasing demand of freshwater resources have culminated into a global water crisis. Desalination is a potential solution to mitigate the freshwater shortage. However, the process of desalination is expensive and energy-intensive. Due to the water-energy-climate nexus, there is an urgent need to provide sustainable low-cost electrical power for desalination that has the lowest impact on climate and related ecosystem challenges. For a large-scale reverse osmosis desalination plant, we have proposed the design and analysis of a photovoltaics and battery-based stand-alone direct current power network. The design methodology focusses on appropriate sizing, optimum tilt and temperature compensation techniques based on 10 years of irradiation data for the Carlsbad Desalination Plant in California, USA. A decision-tree approach is employed for ensuring hourly load-generation balance. The power flow analysis evaluates self-sufficient generation even during cloud cover... [more]

Silicon-based sensors are widely used for monitoring solar irradiance, in particular, in the field of Photovoltaic (PV) applications. We present a method to correct the global horizontal irradiance measured by silicon-based sensors that reduces the difference to the standard thermopile sensor measurements. A major motivation to use silicon-based sensors for the measurements of irradiance is their lower cost. In addition, their response time is much lower, and their spectral response is much closer to that of the PV systems. The analysis of the differences is based on evaluating four parameters that influence the sensor measurements, namely the temperature, cosine error, spectral mismatch, and calibration factor. Based on the analysis, a correction model is applied to the silicon sensors measurements. The model separates measurements under a clear sky and cloudy sky by combining the clearness index and the solar zenith angle. By applying the correction model on the measurements of the s... [more]

The deployment of renewable energy at the local level can contribute significantly to mitigating climate change, improving energy security and increasing social, economic and environmental benefits. In many countries local authorities play an important role in the local development, but renewable energy deployment is not an obligatory task for them. Hence there are two research questions: (1) Do local governments think investments in renewable energy (RE) are urgent and affordable within the local budgets? (2) How do they react to the public aid co-financing investments in renewable energy? To provide the answer we performed qualitative analysis and non-parametric tests of data from a survey of 252 local authorities, analysis of 292 strategies of local development and datasets of 1170 renewable energy projects co-financed by EU funds under operational programs 2007−2013 and 2014−2020 in Poland. Findings showed that local authorities’ attitudes were rather careful, caused by financial c... [more]

The study described in this paper uses direct evidence from processes applied for the developing economy of Indonesia, as it defines the trajectory for its future energy policy and energy research agenda. The paper addresses the research gap to make explicit the process undertaken by key stakeholders in assessing and determining the suitability, feasibility, and dynamics of the renewable energy sector. Barriers and enablers that are key in selecting the most suitable renewable energy sources for developing economies for the renewable energy development have been identified from extensive analyses of research documents alongside qualitative data from the Focus Group Discussions (FGD). The selected FGD participants encompass the collective views that cut across the political, economic, social, technological, legal, and environmental aspects of renewable energy development in Indonesia. The information gained from the FGD gives insights into the outlook and challenges that are central to... [more]

One of the solutions to reduce environmental emissions is related to the deployment of electric vehicles (EVs) with sustainable energy. In order to be able to increase the number of electric vehicles in circulation, it is important to implement optimal planning and design of the infrastructure, with particular reference to areas equipped with charging stations. The suitable analysis of the location of current electric vehicle charging stations (EVCSs) is the central theme of this document. The research focused on the actual location of the charging stations of five major EVCS companies in the province by selecting Istanbul as the study area. The study was conducted through a three-step approach and specifically (i) the application of the analytical hierarchy process (AHP) method for creating the weights of the 6 main and 18 secondary criteria that influence the location of EVCSs; (ii) a geospatial analysis using GIS considering each criterion and developing the suitability map for the... [more]

Reliable seismic hazard analyses are crucial to mitigate seismic risk. When dealing with induced seismicity the standard Probabilistic Seismic Hazard Analysis (PSHA) has to be modified because of the peculiar characteristics of the induced events. In particular, the relative shallow depths, small magnitude, a correlation with field operations, and eventually non-Poisson recurrence time. In addition to the well-known problem of estimating the maximum expected magnitude, it is important to take into account how the industrial field operations affect the temporal and spatial distribution of the earthquakes. In fact, during specific stages of the project the seismicity may be hard to be modelled as a Poisson process—as usually done in the standard PSHA—and can cluster near the well or migrate toward hazardous known or—even worse—not known faults. Here we present a technique in which we modify the standard PSHA to compute time-dependent seismic hazard. The technique allows using non-Poisson... [more]

Spark-ignited internal combustion engines are known to exhibit a decreased brake efficiency in part-load operation. Similarly to cylinder deactivation, the x-stroke operation presented in this paper is an adjustable form of skip-cycle operation. It is an effective measure to increase the efficiency of an internal combustion engine, which has to be equipped with a variable valve train to enable this feature. This paper presents an optimization procedure for the exhaust valve timings applicable to any valid stroke operation number greater than four. In the first part, the gas spring operation, during which all gas exchange valves are closed, is explained, as well as how it affects the indicated efficiency and the blow-by mass flow. In the second part, a simulation model with variable valve timings, parameterized with measurement data obtained on the engine test, is used to find the optimal valve timings. We show that in 12-stroke operation and with a cylinder load of 5 Nm, an indicated e... [more]

Brazil, Russia, China, India, and the Republic of South Africa (BRICS) represent developing economies facing different energy and economic development challenges. The current study aims to predict energy consumption in BRICS at aggregate and disaggregate levels using the annual time series data set from 1992 to 2019 and to compare results obtained from a set of models. The time-series data are from the British Petroleum (BP-2019) Statistical Review of World Energy. The forecasting methodology bases on a novel Fractional-order Grey Model (FGM) with different order parameters. This study contributes to the literature by comparing the forecasting accuracy and the predictive ability of the FGM1,1 with traditional ones, like standard GM1,1 and ARIMA1,1,1 models. Moreover, it illustrates the view of BRICS’s nexus of energy consumption at aggregate and disaggregates levels using the latest available data set, which will provide a reliable and broader perspective. The Diebold-Mariano test resu... [more]

Using information from an experimental planting of non-toxic Jatropha curcas (NTJC) with minimal water and fertilization resources on rural marginal soil the objective of this article is to determine the sustainability of this raw material for producing biodiesel and the possibilities for improving it through life-cycle assessment (LCA). Three production scenarios were studied: minimal resources (MR), which focuses on the obtaining of biodiesel; minimal resources and utilization of sub-products (MRUS), which includes the utilization of the residual products in order to produce food and solid biofuels, as well as biodiesel; and utilization of biofertilizers, flood irrigation, and sub-products (UBIS), which incorporates the use of bio-fertilizers and irrigation in the production system. This study includes the selection of six sustainability indicators, as well as indicators by means of LCA methodology Finally, a sustainability index (SI) for each scenario was determined on the basis of... [more]

A significant part of energy consumption in Northern countries goes to heating. There is no consensus about the most efficient source of renewable heat there. This paper presents a field study for a 7.8 m2 vacuum tube solar collector facility that is conservatively located in the cloudy and cold climate conditions of western Norway. We analyse a year-long operation by examining the rig’s statistics. We show that in Nordic latitudes with rainy climate conditions, a domestic solar hot water system can produce 2200 kWhth/y at a thermal efficiency of up to 72%. The average amount of heat produced by the collectors was up to 14.7 kWhth/d. This was enough to sustain the domestic hot water demand in an average Norwegian household for 6 months with a short period of auxiliary heating. In conclusion, we calculated that a 3× upscaled area facility would deliver over 25 kWhth covering six months of total heat consumption. The payback period for the facility is 12 years.

The present work reviews the role of biogas as advanced biofuel in the renewable energy system, summarizing the main raw materials used for biogas production and the most common technologies for biogas upgrading and delving into emerging biological methanation processes. In addition, it provides a description of current European legislative framework and the potential biomethane business models as well as the main biogas production issues to be addressed to fully deploy these upgrading technologies. Biomethane could be competitive due to negative or zero waste feedstock prices, and competitive to fossil fuels in the transport sector and power generation if upgrading technologies become cheaper and environmentally sustainable.

Turkmenistan is currently one of the key suppliers in the global natural gas market, and it is important to examine its competitive position in the world. The aim of this article is to forecast the development strategy of its gas sector. To achieve this aim, the authors first examined: (1) Turkmenistan’s position in the global gas market and the structure of its oil and gas sector; (2) the share of gas in Turkmenistan’s exports. They then conducted an analysis of the causal relationship between FDI and GDP. The above research made it possible to conduct a comprehensive SWOT analysis. Based on the SWOT analysis, three sector development scenarios were developed: pessimistic, realistic, and optimistic. On their basis, the gas sector in Turkmenistan can build strategies for its development, considering the impact of market and non-market factors.

The rotary-percussion drilling method is a prospective way to decrease drilling costs. It is obvious, based on literature analyses and finished geothermal drilling, that the Lublin Basin can be perceived as the one where rotary-percussion drilling can be used to drill an overburden of shale rocks. The paper explained the geology of the Lublin Basin, its’ geological structures, and the possibility of the use of drilling with a down-the-hole hammer, which could significantly decrease the cost of the whole shale gas drilling investment. Data collected from the wells drilled in the Lublin Basin were compared and analyzed to determine the viability of rotary-percussion drilling. Provided analyses showed that using the rotary-percussion drilling method in the Lublin Basin had a greater possibility of application than in other Polish shale basins (Baltic and Podlasie).

The development of internal combustion engines involves various new solutions, one of which is the use of dual-fuel systems. The diversity of technological solutions being developed determines the efficiency of such systems, as well as the possibility of reducing the emission of carbon dioxide and exhaust components into the atmosphere. An innovative double direct injection system was used as a method for forming a mixture in the combustion chamber. The tests were carried out with the use of gasoline, ethanol, n-heptane, and n-butanol during combustion in a model test engine—the rapid compression machine (RCM). The analyzed combustion process indicators included the cylinder pressure, pressure increase rate, heat release rate, and heat release value. Optical tests of the combustion process made it possible to analyze the flame development in the observed area of the combustion chamber. The conducted research and analyses resulted in the observation that it is possible to control the ex... [more]