The alcohols ethanol and 1-butanol are interesting options as blending components for renewable fuels. We studied whether it is possible to mix these alcohols with a little refined material, rapeseed oil, to obtain stable fuel samples. At room temperature, the stable samples consisted of rapeseed oil blended with butanol at 5 vol-%, 10 vol-%, 20 vol-%, 30 vol-% and one sample of rapeseed oil with 5 vol-% of ethanol. The samples’ fuel properties analysed were kinematic viscosity (at 40 °C), density (at 15 °C) and surface tension. Cold filter plugging point was measured for rapeseed oil with 20 vol-% and 30 vol-% of butanol. Stability of butanol or ethanol and rapeseed oil blends can be achieved at the studied volumes. The density of neat rapeseed oil and all the alcohol−rapeseed oil blends met the requirements set for residual marine fuels. The 30 vol-% butanol−rapeseed oil blend met the requirements for distillate marine oil for density, and almost for kinematic viscosity. The blends a... [more]

Currently, lipid extraction remains a major bottleneck in microalgae technology for biofuel production. In this study, an effective and easily controlled cell wall disruption method based on electro-Fenton reaction was used to enhance lipid extraction from the wet biomass of Nannochloropsis oceanica IMET1. The results showed that 1.27 mM of hydroxide radical (HO•) was generated under the optimal conditions with 9.1 mM FeSO4 in a 16.4 mA·cm−2 current density for 37.0 min. After the electro-Fenton treatment, the neutral lipid extraction yield of microalgae (~155 mg) increased from 40% to 87.5%, equal to from 12.2% to 26.7% dry cell weight (DCW). In particular, the fatty acid composition remained stable. The cell wall disruption and lipid extraction processes were displayed by the transmission electron microscope (TEM) and fluorescence microscopy (FM) observations, respectively. Meanwhile, the removal efficiency of algal cells reached 85.2% within 2 h after the reaction was terminated. Fu... [more]

The internal combustion engine (ICE) as a main power source for transportation needs to improve its efficiency and reduce emissions. The Organic Rankine Cycle (ORC) is a promising technique for exhaust heat recovery. However, vehicle engines normally operate under transient conditions with both the engine speed and torque varying in a large range, which creates obstacles to the application of ORC in vehicles. It is important to investigate the dynamic performance of an ORC when matching with an ICE. In this study, the dynamic performance of an ICE-ORC combined system is investigated based on a heavy-duty diesel engine and a 5 kW ORC with a single-screw expander. First, dynamic simulation models of the ICE and the ORC are built in the software GT-Power. Then, the working parameters of the ORC system are optimized over the entire operation scope of the ICE. A closed-loop proportional-integral (PI) control together with a feedforward control is designed to regulate the operation of the OR... [more]

There is the potential for hybridised gas engine-energy storage systems to participate in the Balancing Mechanism (BM) by offering a product that marries the advantages of both units. The higher price offerings are currently dominated by pumped storage (PS) assets. Given their high-flexibility, PS plants mostly offer at higher prices, but respond quicker and can run for a smaller minimum run time than a gas engine on its own. The operation of the hybrid system must match the operation of the pumped storage plants, to be able to claim a space in this part of the BM market including meeting a minimum run time and minimum start time. The business case is dependent on battery costs which in turn depend on size and operational strategy. This paper uses a case study approach to estimate Net Present Value of a hybrid system. The paper uses a mixture of publicly available data and industrially provided data within its analysis. The paper concludes that battery cost and lifespan are still issue... [more]

With an elevation of 1000 m above sea level, once the coastal mountain range is crossed, the Atacama Desert receives the highest levels of solar radiation in the world. Global horizontal irradiations over 2500 kWh/(m2 year) and a cloudiness index below 3% were determined. However, this index rises to 45% in the coastal area, where the influence of the Pacific Ocean exists with a large presence of marine aerosols. It is on the coastal area that residential photovoltaic (PV) applications are concentrated. This work presents a study of the soiling impact on PV modules at the coastline of Atacama Desert. The current−voltage characteristics of two multicrystalline PV modules exposed to outdoor conditions were compared, while one of them was cleaned daily. Asymptotic behavior was observed in the accumulated surface dust density, over 6 months. This behavior was explained by the fact that as the glass became soiled, the probability of glass-to-particle interaction decreased in favor of a more... [more]

Hydropower units undertake tasks such as peak shaving, frequency modulation, and providing accident reserves in the power system. With the increasing capacity and structural complexity of power systems, hydropower units have become more important. Hydraulic-turbine-governing systems (HTGSs) need to have higher control performance and automation levels to meet the higher regulatory requirements of the power system. To achieve high-quality control, we proposed a new finite-time, fault-tolerant control method for HTGSs with an actuator fault. First, a fractional-order model for HTGSs with uncertainty, external disturbance, and an actuator fault was introduced. Second, a fault estimator that could quickly track the fault signal for an actuator fault was proposed. Then, based on the fractional-order finite-time stability theorem, a finite-time, fault-tolerant controller was proposed for the stabilization of an HTGS. Furthermore, a controller was developed as a fractional differential form c... [more]

Soiling of solar module cover glass is a serious problem for solar asset managers. It causes a reduction in power output due to attenuation of the incident light, and reduces the return on investment. Regular cleaning is required to mitigate the effect but this is a costly procedure. The application of transparent hydrophobic, anti-soiling coatings to the cover glass is a promising solution. These coatings have low surface energy and contaminants do not adhere well. Even if soiling does remain on the coated surface, it is much more easily removed during cleaning. The performance of the coatings is determined using the water contact angle and roll-off angle measurements. However, although hydrophobic coatings hold out great promise, outdoor testing revealed degradation that occurs surprisingly quickly. In this study, we report on results using laboratory-based damp heat and UV exposure environmental tests. We used SEM surface imaging and XPS surface chemical analysis to study the mechan... [more]

To achieve the Paris Agreement’s long-term temperature goal, current energy systems must be transformed. Australia represents an interesting case for energy system transformation modeling: with a power system dominated by fossil fuels and, specifically, with a heavy coal component, there is at the same time a vast potential for expansion and use of renewables. We used the multi-sectoral Australian Energy Modeling System (AUSeMOSYS) to perform an integrated analysis of implications for the electricity, transport, and selected industry sectors to the mid-century. The state-level resolution allows representation of regional discrepancies in renewable supply and the quantification of inter-regional grid extensions necessary for the physical integration of variable renewables. We investigated the impacts of different CO2 budgets and selected key factors on energy system transformation. Results indicate that coal-fired generation has to be phased out completely by 2030 and a fully renewable... [more]

Animal manure represents a major source of renewable energy that can be converted into biogas using anaerobic digestion. In order to most efficiently utilize this resource, it can be co-digested with energy dense, high biomethanation potential feedstocks such as energy crops. However, such feedstocks typically require pretreatments which are not feasible for small-scale facilities. We investigated the use of single-stage and the sequential co-digestion of comminuted but otherwise non-pretreated Salix with animal manure, and further investigated the effects of coppicing frequency and clone choice on biomethanation potential and the area requirements for a typical Swedish farm-scale anaerobic digester using Salix and manure as feedstock. In comparison with conventional single-stage digestion, sequential digestion increased the volumetric and specific methane production by 57% to 577 NmL L−1 d−1 and 192 NmL (g volatile solids (VS))−1, respectively. Biomethanation potential was the highest... [more]

More and more cities are evolving into smart cities, increasing their attractiveness, energy efficiency, and users’ satisfaction. Lighting systems play an important role in the evolution process, thanks to their ability to affect city life at night along with people’s mood and behaviour. In this scenario, advanced lighting design methods such as virtual reality (VR) became essential to assess lighting systems from different points of view, especially those linked with the city users’ expectations. Initially, the review highlights a list of objective and subjective parameters to be considered for the lighting design of three main city areas/applications: roads, green areas and buildings. Besides, the state-of-art in using VR for outdoor lighting design is established. Finally, the Unreal game engine is used to analyse the ability of VR to take into account the lighting parameters, not yet investigated in current literature and to highlight the VR potential for augmenting lighting design... [more]

The global concentration of greenhouse gasses in the atmosphere is increasing as well as the emissions of harmful pollutants. Utilization of liquid biofuels in combustion engines helps to reduce these negative effects. For diesel engines, the most common alternative fuels are based on vegetable oils. Blending neat vegetable oils with diesel and/or alcohol fuels is a simple way to make them suitable for diesel engines. In this study, coconut oil was used in ternary fuel blends with diesel and butanol. Coconut oil is a potentially usable source of renewable energy, especially in the Pacific, where it is a local product. Diesel fuel-coconut oil-butanol fuel blends were used in concentrations of 70%/20%/10% and 60%/20%/20%, and 100% diesel fuel was used as a reference. The effect of the fuel blends on the production of harmful emissions, engine smoke, performance parameters, fuel consumption and solid particles production was monitored during the measurement. The engine was kept at a const... [more]

In order to improve the recovery efficiency of natural gas hydrate in solid-state fluidized mining of natural gas hydrate, we solve drilling safety problems, such as narrow density of natural gas hydrate formation pressure window and poor wellbore stability caused by high upstream velocity during drilling and production. In this study—in order to increase the natural gas hydrate output and reduce production costs—based on the principle of the solid-state fluidized mining, a natural gas hydrate drilling method based on double-layer continuous-pipe double-gradient drilling was proposed to solve the above problems. The article introduces a drilling and production tool combination scheme and the mathematical model of wellbore-pressure dynamic regulation. Simulation software was used to study and compare the migration efficiency of multiphase mixed slurries of sediment and natural gas hydrates in the horizontal section of the double-layer continuous-pipe double-gradient drilling method and... [more]

This work investigates life cycle costing analysis as a tool to estimate the cost of hydrogen to be used as fuel for Hydrogen Fuel Cell vehicles (HFCVs). The method of life cycle costing and economic data are considered to estimate the cost of hydrogen for centralised and decentralised production processes. In the current study, two major hydrogen production methods are considered, methane reforming and water electrolysis. The costing frameworks are defined for hydrogen production, transportation and final application. The results show that hydrogen production via centralised methane reforming is financially viable for future transport applications. The ownership cost of HFCVs shows the highest cost among other costs of life cycle analysis.

This article presents results of experimental study of diesel, rapeseed oil and three different blends of 10%, 20% and 30% diethyl ether addition to rapeseed oil, tested on VW Golf vehicle on chassis dynamometer Mustang MD-1750. Fuel consumption and emission tests were conducted at different testing conditions: idling, 50 km/h, 90 km/h, as also IM-240 cycle. The analysis of obtained results have shown reduction of engine power by 6.2%−17.3% and increase of fuel consumption by 0.6%−15.5% (based on testing conditions) for all blends based on DEE addition compared to RO, demonstrating better perspectives for low level blends. Emission tests have shown decrease of hydrocarbons and nitrogen oxides (NOx) for all blends with DEE content in almost all testing conditions and also slight increase of carbon monoxides and carbon dioxides compared to rapeseed oil. Largest decrease of NOx was observed during 90 km/h and cycle IM-240 reaching almost 24% reduction for 20DEE and 30DEE in comparison to... [more]

Biofuels provide high oxygen content for combustion and do modify properties that influence the engine operation process such as viscosity, enthalpy of vaporization, and cetane number. Some requirements of performance, fuel consumption, efficiency, and exhaust emission are necessary for the validation of these biofuels for application in engines. This work studies the effects of the use of diethyl ether (DEE) in biodiesel-ethanol blends in a DI mechanical diesel engine. The blends used in the tests were B80E20 (biodiesel 80%-ethanol 20%) and B76E19DEE5 (biodiesel 76%-ethanol 19%-DEE 5%). Fossil diesel (D100) and biodiesel (B100) were evaluated as reference fuels. The results revealed similar engine efficiencies among tested fuels at all loads. The use of B100 increased CO and NOx and decreased THC compared to D100 at the three loads tested. B80E20 fuel showed an increase in NOx emission in comparison with all fuels tested, which was attributed to higher oxygen content and lower cetane... [more]

Changing the heat transfer fluid (HTF) is a viable approach to study the corresponding effect on the thermal and hydraulic performances of parabolic trough collectors (PTC). Three categorized-types of pure fluids are used in this study; water, Therminol® VP-1 and molten salt. The parametric comparison between pure fluids is also studied considering the effect of various inlet fluid temperatures and different Reynolds ( R e ) numbers on the thermal performance. Two low-Reynolds turbulence models are used; Launder and Sharma (LS) k-epsilon and Shear Stress Transport (SST) k-omega models. In order to assess the performance of each fluid, a number of parameters are analyzed including average Nusselt ( N u ) number, specific pressure drop distributions, thermal losses, thermal stresses and overall thermal efficiency of the PTC system. Results confirmed that changing the working fluid in the PTC enhances the overall heat transfer thereby improving thermal efficiency. For a temper... [more]

The limitation of battery capacity is a cause of range anxiety that reduces the wide use of electric bicycles (e-bikes). Therefore, many works have developed systems that provide assistance to cyclists to deal with the range anxiety problem. However, these systems may have limited applications since they can only work with the e-bike manufacturers’ hardware and communication protocols. This paper proposes an energy monitoring system (EMS) for e-bikes, which is based on EnergyBus, a standardized hardware and communication protocol for e-bikes. EnergyBus standard is based on controller area network (CAN) bus and CANopen protocols. EMS comprises a gateway connected to EnergyBus of e-bike and an EMS application installed on a smart device that connects to the gateway via Bluetooth. The gateway provides CAN bus monitoring and CANopen device data access services to the smart device. These services are modeled to determine gateway parameters to ensure the efficient performance of the gateway... [more]

In this paper, a systematic study is carried out to compare the performance of various V-I models at both normal and faulty conditions, in terms of simulating proton exchange membrane fuel cell (PEMFC) behavior and analyzing the corresponding degradation process. In the analysis, the simulation accuracy of V-I models, including overall behavior simulation and the simulation of different PEMFC losses, is investigated. Results show that compared to the other V-I models, the V-I model using exponential function for mass transport loss and considering open circuit voltage (OCV) at zero current can provide the best simulation performance, with an overall root mean square error (RMSE) of about 0.00279. Furthermore, the performance of these V-I models in analyzing PEMFC degradation process is also studied. By investigating the evolution of PEMFC losses during the degradation, the effectiveness of these models in interpreting PEMFC degradation mechanisms can be clarified. The results show that... [more]

The use of renewable energies, energy saving, and efficiency are needs of global society. According to the latest estimates, global energy demand could triple by 2050 and, by then, 70% of the world’s population will live in cities. Cities are currently responsible for 80% of greenhouse gas emissions, so they have a key role to play in shifting towards a sustainable energy future. Cities are threatened not only by overcrowding, but also by rising energy demand, obsolete infrastructure, volatile energy markets, and the effects of climate change. This Special Issue aims to advance the contribution of energy saving and the use of renewable energies in order to achieve more sustainable cities.

This paper proposes a high gain DC−DC converter based on the series resonant converter (SRC) for photovoltaic (PV) applications. This study considers low power applications, where the resonant inductance is usually relatively small to reduce the cost of the converter realization, which results in low-quality factor values. On the other hand, these SRCs can be controlled at a fixed switching frequency. The proposed topology utilizes a bidirectional switch (AC switch) to regulate the input voltage in a wide range. This study shows that the existing topology with a bidirectional switch has a limited input voltage regulation range. To avoid this issue, the resonant tank is rearranged in the proposed converter to the resonance capacitor before the bidirectional switch. By this rearrangement, the dependence of the DC voltage gain on the duty cycle is changed, so the proposed converter requires a smaller duty cycle than that of the existing counterpart at the same gain. Theoretical analysis s... [more]

This paper presents a comparison of the efficiency of energy storage and energy curtailment as an addition to the allocation of renewable energy in the distribution system in order to minimize development costs using a Mixed Integer-Linear Programming (MILP). Energy sources and energy storages are selected, sized and allocated under operational circumstances such as grid congestions and weather conditions. Loads and power units are modeled by daily consumption and generation profiles respectively, to reflect the intermittent character of renewable generation and consumption of energy. The optimization is carried out for a one-year time horizon using twenty-four representative days. The method is verified on three main simulation scenarios and three sub-scenarios for each of them, allowing for the comparison of the efficiency of each used tool. The main scenarios differ in their share of energy from renewable energy sources (RES) in total consumption. In the sub-scenarios, different too... [more]

The scope of the present study was to understand the wake characteristics of wind-turbines under various inflow shears. First, in order to verify the prediction accuracy of the in-house large-eddy simulation (LES) solver, called RIAM-COMPACT, based on a Cartesian staggered grid, we conducted a wind-tunnel experiment using a wind-turbine scale model and compared the numerical and experimental results. The total number of grid points in the computational domain was about 235 million. Parallel computation based on a hybrid LES/actuator line (AL) model approach was performed with a new SX-Aurora TSUBASA vector supercomputer. The comparison between wind-tunnel experiment and high-resolution LES results showed that the AL model implemented in the in-house LES solver in this study could accurately reproduce both performances of the wind-turbine scale model and flow characteristics in the wake region. Next, with the LES solver developed in-house, flow past the entire wind-turbine, including th... [more]

Improving the efficiency of an internal combustion engine (ICE) leads to the reduction of fuel consumption, which improves the performance of a hybrid vehicle. Waste heat recovery (WHR) systems offer options to improve the efficiency of an ICE. This is due to the ICE releasing approximately one third of the combustion energy as waste heat into the atmosphere. This paper focuses on one such upcoming system by analysing the efficiency of a thermoelectric generator (TEG) used as a waste heat recovery system in a hybrid electric vehicle (HEV). It summarises how the efficiency of the TEG can be improved by considering parameters such as the size of module, materials used, and the number of modules needed for the TEG system. The results obtained are then compared with other types of WHR system such as the Organic Rankine Cycle (ORC) and turbocompounding (T/C) implemented on the same type of engine. The research is based on a 1.8 L Toyota Prius-type engine. The TEG model simulated in this res... [more]

This work concerns borehole heat exchangers and their testing using apparatus for thermal response tests. In the theoretical part of the article, an equation was derived from the known equation of heat flow, on which the interpretation of the thermal response test was based. The practical part presents the results of several measurements taken in the AGH Laboratory of Geoenergetics. They were aimed at examining the potential heat exchange capacity between the heat carrier and rock mass. Measurement results in the form of graphs are shown in relation to the examined, briefly described wells. Result analysis made it possible to draw conclusions regarding the interpretation of the thermal response test. The method of averaging the measurement results was subjected to further study. The measuring apparatus recorded data at a frequency of one second, however such accuracy was too large to be analyzed efficiently. Therefore, an average of every 1 min, every 10 min, and every 60 min was propo... [more]

Notwithstanding the policies that move towards electrified powertrains, the transportation sector mainly employs internal combustion engines as the primary propulsion system. In this regard, for medium- to heavy-duty applications, as well as for on- and off-road applications, diesel engines are preferred because of the better efficiency, lower CO2, and greater robustness compared to spark-ignition engines. Due to its use at a large scale, the internal combustion engines as a source of energy depletion and pollutant emissions must further improved. In this sense, the adoption of alternative combustion concepts using cleaner fuels than diesel (e.g., natural gas, ethanol and methanol) presents a viable solution for improving the efficiency and emissions of the future powertrains. Particularly, the methane−diesel dual-fuel concept represents a possible solution for compression ignition engines because the use of the low-carbon methane fuel, a main constituent of natural gas, as primary fue... [more]