Long-term Reliable Operation Research Articles

Methods of сorrosion testing used for development and commercial exploitation of new shipbuilding steels and alloys. Part I. Laboratory corrosion tests

Shipbuilding steels and alloys may be subjected to various types of corrosion damage when exposed to sea water. For reliable long-term operation of ships and marine structures, despite the use of corrosion protection, materials are chosen that, in addition to the required mechanical properties, have sufficient corrosion resistance to ensure a given service life. Evaluation of corrosion resistance of new materials for use in shipbuilding was made by carrying out mandatory delivery trials using methods that have been repeatedly tested experimentally and whose results have been confirmed in practice. The complex study of corrosion resistance of steels and alloys is based on step-by-step laboratory, bench, and field tests. The review provides a brief description of laboratory corrosion test methods that are part of mandatory delivery trials. Parameters determining the aggressiveness of seawater as a corrosive medium, including salinity, oxygen content are considered. Laboratory test methods include electrochemical studies with determination of potential and rate of corrosion, pitting potential on the basis of polarization curves construction, as well as the generally accepted gravimetric method of corrosion rate determination. Installations for testing in moving (with varying flow rate) seawater are given.

Hybrid enhancement effect of structural and material properties of the triboelectric generator on its performance in integrated energy harvester

A wind energy harvester (WEH) comprising a coaxial electromagnetic generator (EMG) and a triboelectric nanogenerator (TENG) is proposed to achieve an energy-autonomous closed loop that can harvest widely untapped energy sources for unattended monitoring systems in desolate regions. Energy conversion in the EMG from wind to electrical energy is implemented via the cyclic fixed-axis rotation, whereas that in the TENG is controlled by reciprocating translation driven by the coaxial rotation of the contact-separation structure. However, it is essential, albeit difficult, for TENG to generate a major portion of the wind energy-based electricity by improving the secondary transformation efficiency and reducing wear abrasion. Here, an arrayed contact-separation structure is fabricated with doped and surface-modified friction silicone rubber, large-area arc-shaped substrates, and a Reuleaux triangle plate-cam with local freedom. When the WEH works in one cycle, the TENG runs 12 times. Compared with the single contact-separation structure, the modified friction material significantly increases the output performance of the hybrid enhanced TENG by 104 % and the arrayed cam structure triples the output energy of TENG in a cycle. The maximum output power of the WEH is 54.78 mW at 90 rpm, to which the EMG and TENG contribute approximately 51.57 mW and 3.21 mW, respectively. The share of TENG output energy rivals the results induced by sliding mode TENG in those hybrid energy harvesters of current research. Furthermore, a WEH with an enhanced TENG is experimentally demonstrated by simulating earthquake, fire, and wind speed monitoring. The results indicate the immense potential of the proposed WEH in terms of power supply capability and long-term operation reliability.

Reversing fatigue in carbon-fiber reinforced vitrimer composites

Despite decades of research, fatigue remains the primary culprit for catastrophic failure in carbon-fiber reinforced polymeric (CFRP) composites. Existing approaches to combat fatigue are usually based on nano-scale additives that slow the growth of cracks in the polymer. While this prolongs fatigue-life, it cannot avert eventual failure since crack growth is being slowed and not reversed. Other approaches have explored self-healing polymers that release a curing agent to repair local damage. However, this approach also fails to tackle fatigue, since once the curing agent is released, it gets consumed and cannot be re-used. To addresses the irreversibility of fatigue, we report here a vitrimeric system, for which reversal of fatigue damage can be achieved repeatedly, by heating the material to above its topology freezing transition temperature. This enables intermittent healing of fatigue-induced damage, as it accumulates in the vitrimer matrix. Using this approach, we show that fatigue failure in vitrimers and in carbon-fiber reinforced vitrimers (vCFRP) can be postponed indefinitely. Such vCFRPs could open the door to future materials, in which natural aging and fatigue processes can be periodically reversed, so as to guarantee safe and reliable long-term operation.

ПОВТОРНЕ ВИКОРИСТАННЯ МОСТОВИХ БАЛОК В ЯКОСТІ ПРОГОНОВИХ БУДОВ ТИМЧАСОВИХ МОСТІВ

Introduction. This article presents the results of study of the quality of girders that were used for the construction of temporary road bridge. In the bridge construction practice there is a need to use girders in the construction of road bridges on local roads that can be reused in temporary bridges construction. It is important when using such structures to determine their reliability for long-term operation. The cost of bridge girders is up to 60% of the cost of a new bridge, so the reuse of utilizedsed girders is economically feasible. Utilized girders can be reused on local roads and temporary bridges. Problem statement. To determine the usability of utilized girders in temporary bridges construction and provide recommendations for the girders reuse and possible bridge design structures. Materials and methods. The following works were performed during the inspection: visual inspection of the girders at places of their storage after dismounting; measurement of the basic sizes of girders; determination of concrete strength by non-destructive test method; determination of the number of working reinforcement and the protective layer thickness; measurements of pH of concrete of a protective layer were performed; registration of existing defects was performed. The following measurements were performed during the tests: general displacements and deformations of structural elements of the structures; relative deformations of cross sections; local deformations (displacements in joints). Results. According to the results of tests and calculations, the bearing capacity of the bridge span structure was determined. After analyzing the results of experimental and theoretical studies, conclusions were made regarding the operational performance of the girders of the bridge span structure. Conclusions. Girders in the 1st, the 2nd and the 3rd technical state can be considered suitable for bridge span structures unreservedly. Girders in the 4th technical state, need repairing and reinforcement for reuse in bridge span structures. They cannot be used without repairing. Girders in the 5th technical state cannot be used in the span structures of road bridges. They can be used, for example, as transition slabs, or for pedestrian bridges and crossings, or can be used for testing the technology of bridge structures repairing. Thus, tests of bridge girders and full-size joints testify that the accepted design decision provides the needed bearing capacity of girders and of the bridge span structure as a whole. This confirms the sufficient reliability of utilized girders in the further work. Practice shows that it is also needed to pay great attention to the following: firstly- to the methods of dismantling the girders without damage; secondly — to the proper storage of girders after dismantling.

An Exterior Optical Fibre Sensing Technology Used for Interface Pressure Measurement Between Cable and Accessory

Interface pressure between cable and accessory is the key to ensure the long-term reliable operation of cable accessories. The traditional measurement method of interface pressure is off-line measurement through a built-in piezoelectric sensor. However, this method is difficult to operate and damages the interface structure. In addition, the offline measurement cannot reflect the real-time dynamic change of interface pressure during the operation of cable accessories. Therefore, this paper proposes a new method for the on-line measurement of interface pressure between cable and accessory by means of an exterior optical fibre curvature sensor, whose design mechanism is based on the pure bending theory of optical fibre. Then the relationship model involving the exterior curvature of the cable accessory, the radial displacement and the inner interface pressure is established. Finally, interface pressures of the 8.7/10 kV cable accessory under different expansion ratios are measured by the calibrated optical fibre curvature sensor. The measurement results show that the optical fibre curvature sensor measures the exterior curvature of the accessory accurately; the average sensitivity reaches 7.679 nm/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> , and the measurable curvature ranges from 0.03 to 0.05 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> . The conversion results of interface pressure are basically consistent with the results measured directly by a traditional piezoelectric sensor or simulated mechanically by finite element software. Therefore, the exterior optical fibre sensing technology proposed in this paper is expected to be used for the on-line measurement of the interface pressure between cable and accessory.

Research on Calibration Technology of TEV Partial Discharge Smart Sensors

TEV partial discharge detection is an important method to judge the insulation status of the switchgear. However, the quality of TEV smart sensors produced by different manufacturers on the market is uneven. Some TEV smart sensors that have been put into operation have deficiencies in measurement sensitivity, data stability, and long-term operational reliability. In response to these problems, this paper proposes a TEV smart sensor calibration method and builds a test platform, which is composed of program-controlled signal source, signal coupling device, protocol conversion device, host computer and corresponding integrated control software. On the basis of the existing standards such as sensitivity and linearity, the evaluation of the data stability, reliability and battery lifetime of the TEV smart sensor has been added. It provides a more comprehensive and effective implementation plan for TEV smart sensor performance verification in power grid access test.

Residual stress and mechanical strength of Ce0.8Gd0.2O2-δ-FeCo2O4 dual phase oxygen transport membranes

Ce0.8Gd0.2O2-δ-FeCo2O4 membranes, benefiting from their excellent chemical stability, exhibit a broad application potential in oxygen-consuming industrial processes running in harsh environments. For long-term reliable operation, the membrane needs to possess sufficient mechanical strength. This paper characterizes the typical aspects that challenge the mechanical stability of the sintered membrane, including composition and microstructural defects as well as residual stress and residual stress gradients. It is revealed that mechanical strengths of the sintered membranes increase with decreasing iron cobalt spinel content, that the high iron cobalt spinel content induces microcracks, and that high residual tensile stress gradually decreases from the as-sintered surface to the bulk. Although the residual tensile stress can be reduced by applying an extensive elevated temperature dwell time during cooling, it is suggested to limit the iron cobalt spinel content to a nominal value of 15 wt% to eliminate the residual tensile stress while maintaining a high mechanical strength.

Editorial: Emerging Technologies With High Impact for Ocean Sciences, Ecosystem Management, and Environmental Conservation

While humanity no longer sees them as a boundless resource to use and abuse, our understanding of the oceans and our ability to manage and conserve marine ecosystems are challenged by their very scale and dynamic nature. Many important observational tools are not well suited for cost-efficient scalable deployment or reliable long-term unattended operation at sea. Improved scientific understanding and technological innovation offer opportunities to deliver quality marine observations at optimal resolution and coverage, analyze them at scale, and apply the resulting insights to inform timely ecosystem management, conservation, restoration, and marine science. Together, these advances and insights represent real progress and reasons for optimism in the development of better tools and approaches in support of marine science and conservation. Contributions like the ones highlighted here and ones yet to come increase the odds that we will address some of the many environmental challenges along the way to a sustainable global civilisation.

Next Generation Monitoring of SiC mosfets Via Spectral Electroluminescence Sensing

This article presents a new methodology for monitoring next generation SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> -based converters. The methodology uses the spectral distribution of electroluminescence that is emitted by the body diodes of SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s and includes information on device current as well as the junction temperature. Intelligent estimation algorithms based on artificial neural networks allow processing the extracted information to separately estimate device current and junction temperature with high bandwidth. The resulting unified monitoring of device current and junction temperature galvanically isolates the sensors via optical guides from the power module. Thus, it can be effectively integrated into future power electronic modules to replace external temperature and current sensors and enable monitoring for safe and reliable long-term operation. Previous publications successfully investigated how either temperature or current information can be extracted from the intensity of the emitted light if the other variable is known. However, they did not aim to extract both variables at the same time from one measurement. This work presents how multiple optical sensors with different wavelength sensitivities and artificial-intelligence techniques can separately extract both variables. The proposed technology is evaluated using an automotive-grade SiC power module. Its utilization for monitoring future SiC-based converters allows reducing converter size and cost while increasing reliability.

Photoluminescence Spectroscopy Measurements for Effective Condition Assessment of Transformer Insulating Oil

Condition assessment of insulating oil is crucial for the reliable long-term operation of power equipment, especially power transformers. Under thermal aging, critical degradation in oil properties, including chemical, physical, and dielectric properties, occurs due to the generation of aging byproducts. Ultraviolet-visible (UV-Vis) spectroscopy was recently proposed for the condition assessment of mineral oil. However, this absorption technique may involve all electronic states of the investigated material which typically yield a broad spectrum, and thus cannot precisely reflect the electronic structure of aged oil samples. It also cannot be implemented as an online sensor of oil degradation. In this paper, photoluminescence (PL) spectroscopy is introduced, for the first time, for effective condition assessment of insulating oil. The PL technique involves emission processes that only occur between a narrow band of electronic states that are occupied by thermalized electrons and consequently yields a spectrum that is much narrower than that of the absorption spectrum. Aged oil samples with different aging extents were prepared in the laboratory using accelerated aging tests at 120 °C, under which 1 day of laboratory aging is equivalent to approximately 1 year of aging in the field. These aged samples were then tested using PL spectroscopy with a wavelength ranging from 150 nm to 1500 nm. Two main parameters were evaluated for quantitative analysis of PL spectra: The full width at half-maximum and the enclosed area under the PL spectra. These parameters were correlated to the aging extent. In conjunction with PL spectroscopy, the aged oil samples were tested for the dielectric dissipation factor as an indication of the number of aging byproducts. Interestingly, we find a correlation between the PL spectra and the dielectric dissipation factor. The results of PL spectroscopy were compared to those of UV-Vis spectroscopy for the same samples and the parameters extracted from PL spectra were compared to the aging b-products extracted from UV-Vis spectra. Finally, the corresponding physical mechanisms were discussed considering the obtained results and the spectral shift for each spectrum. It was proved that PL spectroscopy is a promising technique for the condition assessment of insulating oil when compared to conventional transformer oil assessment measuring techniques and even to other optical absorption techniques.

Reliable long-term operation of superconducting bus lines for the LHD

The Large Helical Device (LHD) is an experimental device for helical type fusion plasma in National Institute for Fusion Science and plasma experiments over 150,000 shots have been successfully conducted during twenty long-term plasma experimental campaigns. The LHD has two kinds of superconducting magnets and nine flexible superconducting bus lines with an average length of 55 m, which are utilized as a part of the current feeder system between the coils and the power sources. The superconducting bus lines consist of a pair of aluminum stabilized NbTi/Cu compacted stranded cable insulated electrically and coaxial five corrugated stainless steel tubes with two layers of vacuum insulations. The nominal current is 32 kA and the withstand voltage is 5 kV in 77 K gas helium. From the first experimental campaign, the superconducting bus lines have been stably operated at steady state by using automatic control. It is also confirmed that the status of the superconducting bus lines are kept good thanks to appropriate maintenances. As the results, the reliable operation of the superconducting bus lines has been achieved during the plasma experimental campaigns without any serious failure and the total operational time of the steady state cooling is approximately 58,000 hours.

Effects of Trapping Characteristics on Space Charge and Electric Field Distributions in HVDC Cable under Electrothermal Stress

Space charge behavior has a strong impact on the long-term operation reliability of high voltage–direct current (HVDC) cables. This study intended to reveal the effect of trap density and depth on the space charge and electric field evolution behavior in HVDC cable insulation under different load currents and voltages by combined numerical bipolar charge transport (BCT) and thermal field simulation. The results show that when the load current is 1800 A (normal value), the temperature difference between the inside and the outside of the insulation is 20 °C, space charge accumulation and electric field distortion become more serious with the increase in the trap depth (Et) from 0.80 to 1.20 eV for the trap densities (Nt) of 10 × 1019 and 80 × 1019 m−3, and become more serious with the increase in Nt from 10 × 1019 to 1000 × 1019 m−3 for Et = 0.94 eV. Simultaneously decreasing trap depth and trap density (such as Et = 0.80 eV, Nt = 10 × 1019 m−3) or increasing trap depth and trap density (such as Et = 1.20 eV, Nt = 1000 × 1019 m−3), space charge accumulation can be effectively suppressed along with capacitive electric field distribution for different load currents (1800 A, 2100 A and 2600 A) and voltages (320 kV and 592 kV). Furthermore, we can draw the conclusion that increasing bulk conduction current by simultaneously decreasing the trap depth and density or decreasing injection current from conductor by regulating the interface electric field via simultaneously increasing the trap depth and density can both effectively suppress space charge accumulations in HVDC cables. Thus, space charge and electric field can be readily regulated by the trap characteristics.

Improvement of a semipermeable shell for encapsulation of calcium hydroxide for thermochemical heat storage solutions: Material design and evaluation in laboratory and reactor scale

Thermochemical heat storage concepts offer a promising contribution to an economic, efficient and sustainable future energy supply. The reaction system CaO/Ca(OH)2 is amongst the most considered systems for Concentrated Solar Power (CSP) applications, but as the cost efficiency and good availability of the material are accompanied by poor powder properties, complex and costly reactor solutions are required. Hence, modifications of the storage material promise a option for a reliable long-term operation. The present work discusses considerations on inter- and intraparticular changes of the storage material and options for particle size stabilization. With the background of a previous work, the experimental section presents a successful approach for the enhancement of the mechanical stability of a ceramic shell material by admixing selected additives to the powdery precursor. To assign for possible complex, mutual interactions of the additives, the approach is based on a full factorial design of experiments. Investigations of the microstructure of the material are performed by gas-adsorption and mercury intrusion measurements and enriched by combining light- and scanning electron microscopy on respective samples. The obtained mechanical stability of the selected material is accompanied by a significantly enhanced thermal conductivity. Cycling stability is proven over ten reaction cycles in laboratory and reactor scale. Due to a minimization of the contact area between the storage material core and its stabilizing shell by utilizing spherical particles, it is demonstrated that only a minor formation of thermochemically inert side product is detectable.

Progress on thermal runaway propagation characteristics and prevention strategies of lithium-ion batteries

<p indent="0mm">lithium-ion batteries have been widely used in energy storage systems due to their significant advantages such as relatively high energy and power density. In order to meet the capacity and voltage requirements of the energy storage system, it is necessary to connect the battery monomer to form a module or even a battery pack through different configurations. For the battery system composed of a large number of batteries, which is a vast reservoir of energy, its safety should be considered from the perspective of the energy storage system to ensure long-term safe and reliable operation. Because of the high energy density, flammable electrolyte and low stability of the separator, batteries may get into the problem of thermal runaway. If the speed of the thermal runaway propagation cannot be well controlled in the local area, thermal runaway could propagate from one initiating battery to its neighbors and cause disastrous consequences at the system level. Therefore, when the battery system fails to make key breakthroughs and the intrinsic safety problems cannot be fundamentally solved, it is particularly important to prevent thermal runaway propagation effectively. The purpose of this review is to discuss the research progress on thermal runaway propagation characteristics and prevention strategies of lithium-ion batteries. Firstly, the abuse conditions that may lead to thermal runaway are summarized. Then the characteristics of thermal runaway propagation are clarified from the perspectives of electrical characteristic and heat transfer characteristic. To further describe the heat transfer process of thermal runaway propagation, the thermal network diagram of the battery module is established, which could provide theoretical support for the design of the prevention strategies for thermal runaway. Finally, the modeling method of battery thermal runaway is discussed, and a systematic review of prevention strategies is presented in terms of heat dissipation and insulation, phase change material technology, and the strategy taking into account the normal working conditions. For the heat dissipation and insulation strategy, it should be noted that in order to prevent thermal runaway propagation successfully, the simple heat dissipation method requires additional investment, including cost, space, power consumption, etc. While the effective heat insulation between batteries could help block the harmful heat transfer path and reduce the requirement of fast heat dissipation capacity. For the phase change material technology, the heat transfer path diagram of the battery module is established. By improving the thermal conductivity of phase change material, the generated heat of the battery in case of thermal runaway could be distributed more uniformly to the phase change material in other areas of the module. Besides, the heat transfer capacity of the system can be further improved by setting heat transfer components at the module boundary or between the phase change materials. To further optimize the thermal management performance of the battery, the strategy taking into account the normal working conditions should be considered, which can meet the dual requirements of thermal safety and temperature control through a reasonable combination of heat conduction and insulation. This review is expected to provide theoretical basis and engineering application guidance in designing the thermal management system, so as to improve the safety performance of lithium-ion battery.

Моделирование системы управления рысканием ветротурбины

Owing to its being an important component of renewable energy, wind energy is a kind of power generation method with the most mature, highly developed technologies and broad commercial prospects. The stable and efficient conversion of wind energy by wind turbines depends not only on the reliability of the wind power generation equipment itself, but also on the wind turbine control system, which, in turn, contributes to long-term safe and reliable operation of the wind farm fleet. It is exactly the wind turbine control system that is the main subject of this study. The key to efficient and stable operation of the entire wind energy conversion system is the control technology, which includes yaw control, pitch angle control, and maximum power point tracking control. The active yaw control system is one of the important components of a horizontal axis wind turbine's control system. To eliminate the uncertainty of wind direction influence on the turbine power output, a composite yaw control system has been checked. By using an active yaw system and maximum power point tracking system, the turbine position and its rotation speed are adjusted to enable the wind turbine to accurately track the wind direction and capture the wind energy to the fullest extent.

Energy Management Strategies for Hybrid Power Systems Considering Dynamic Characteristics of Power Sources

Due to the rising concern of environmental problems, fuel cell hybrid power systems have been proposed to be an ideal substitution to diesel engines. However, the hybrid power system has brought many challenges, one of which is the power splitting among different power generation technologies. In this paper, a wavelet transform and fuzzy logic based energy management strategy is proposed for a fuel cell/battery/ultra-capacitor hybrid power cruiser considering their dynamic characteristics. The energy demand of the cruiser is decoupled into different frequencies by wavelet transform and distributed to different energy sources according to their dynamic characteristics. To ensure long-term reliable operation of the hybrid power system, fuzzy logic is proposed to keep the state of charges of the battery and ultra-capacitor within safe range. The proposed energy management strategy is applied to a hybrid power cruiser in MATLAB/Simulink and two cases are studied considering different initial states of charge of the energy storage system. The results show that the proposed energy management strategy enables the fuel cell to supply about 50% of the high frequency power and reduce the peak power supplied by the fuel cell by 80% - 100% when the initial state of charge of the ultra-capacitor is low, and the fuel cell supplies around 400% higher than the low peak power and 20% of the high peak power when the initial state of charge of the battery is low.

Assessment of Thermal Aging Degree of 10kV Cross-Linked Polyethylene Cable Based on Depolarization Current

During the long-term operation of high-voltage cross-linked polyethylene (XLPE) cables, the cable will gradually deteriorate under the effect of various aging factors. Thermal aging is one of the key factors directly related to the long-term operation reliability of the XLPE cables. In this paper, the thermal aging samples are prepared for PDC measurement. Based on the polymer trap theory and the extended Debye model, the shape of PDC curve, depolarization charge, parameters of the extended Debye model, aging factor (A), elongation at break retention rate (EB%) and their relationships under different thermal aging degrees are analyzed. The results show that the depolarization current curve and the depolarization charge can preliminarily judge the aging condition of the XLPE, but it is not accurate enough. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{3}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau _{3}$ </tex-math></inline-formula> of the branch, with the largest time constant must be the most sensitive to cable aging. With the increase of aging degree, the A shows an upward trend, and has a nonlinear relationship with EB%. Under the aging temperature of 140 °C, after 15–25 days of aging, the A suggests the samples are in the moderate to severe aging stage, and the PDC test should be performed on carried out for the cables with that have been used for 21 years of operation to evaluate the insulation aging condition. The study reveals that the PDC-based parameters can be serviced as an effective tool for the aging condition prediction of XLPE cable insulation.

Effects of water atmosphere on chemical degradation of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ electrodes

Protonic ceramic fuel cells (PCFC) based on a state-of-the-art electrolyte and cathode materials with extremely low ohmic resistance and high surface exchange rate in the intermediate temperature range (500–650 °C) have demonstrated exceptional power output in recent studies. However, reliable long-term operation remains a challenging issue in the development of PCFCs for practical applications. In particular, the water generated at the cathode has been reported to accelerate cation segregation and phase destruction of materials, thereby resulting in significant performance degradation. In this study, we investigate the underlying mechanism of the rapid chemical and electrochemical degradation of thin film PrBa0.5Sr0.5Co1.5Fe0.5O5+δ model electrodes in a water atmosphere. The electrochemical degradation, concurrent with the formation of Ba- and Sr-enriched surface clusters, was more significant in the water atmosphere than a dry atmosphere. Water adsorption onto the electrode surface was found to substantially alter the chemical states of the electrodes. In particular, the increased oxygen vacancies caused an increase in the electrostatic attraction, in turn, facilitating the cation segregation and phase destruction of the electrodes.

Evaluation of pure rapeseed oil as a renewable fuel for agricultural machinery based on emission characteristics and long-term operation behaviour of a fleet of 18 tractors

The usage of locally produced pure rapeseed oil fuel (R100) according to fuel standard DIN 51605 in agricultural machinery can contribute to protecting the climate, water, and soil. Besides economic aspects, uncertainties concerning the long-term operation reliability and limited exhaust emissions of R100-operated agricultural machinery are hindering market entry. Thus, the aim of this research is to evaluate field experiences, such as downtimes and repairs, engine oil quality, and cold start behaviour, over a total period of more than 50,000 operation hours with 18 tractors. The tested tractors range from European Union exhaust gas stages I to IV and were configured for the use of R100. Additionally, performance, nitrogen oxides, and particulate matter were measured on a tractor test stand. The tractors demonstrated their full functionality under usual Bavarian farm conditions in daily use. Within the tractor fleet, no serious engine damage was observed, while minor malfunctions and necessary repairs occurred just occasionally. The operational reliability of the tested rapeseed-oil-fuelled tractors seemed to be comparable to that of diesel-fuelled tractors. The results of recurrent power and fuel consumption measurements gave no indication of engine deterioration. Furthermore, measurements proved that differences in exhaust gas emissions between R100 and diesel operation were marginal. Tractor models with exhaust gas after treatment systems were characterized by low emissions of nitrogen oxides and particulate matter in particular. With the 18 tractors running on R100, about 220 tonnes of CO2eq per year were saved on average from 2015 to 2017. It can be concluded that the usage of pure rapeseed oil fuel (R100) in compatible agricultural machinery is an implementable alternative to diesel fuel and can make an important contribution to reducing greenhouse gas emissions in agriculture. Nevertheless, there are some challenges to solve, particularly for modern agricultural machines with engines with exhaust gas aftertreatment systems.

Thermal evaluation of a hermetic transcutaneous energy transfer system to power mechanical circulatory support devices in destination therapy.

Current generation left ventricular assist devices (LVADs) are powered by a percutaneous driveline. The high prevalence of driveline infections has motivated the development of transcutaneous energy transfer (TET) systems which eliminate driveline associated complications by wirelessly delivering power across the skin. Destination therapy (DT) requires long-term reliable operation of the TET electronics suggesting the use of hermetic packaging techniques as used in all other chronically implanted devices. TET coils dissipate heat during operation and in order for the technology to be suitable for patient use, sufficient power must be delivered while maintaining temperatures at levels deemed safe. The heating of a TET system designed for DT which uses hermetic packaging technology was evaluated in silico and in vivo. A numerical model was used to evaluate the temperature of the TET coils. The TET system was fabricated and assessed in vivo using an ovine model. The receiving coil was implanted subcutaneously in a sheep and the transmission coil placed in contact with the skin and concentric to the implanted coil. Temperatures of the system were measured using sensors fixed to the surface of the coils. Numerical modeling indicated that the maximum temperatures of the primary and secondary coil surfaces were 38.13°C and 38.41°C, respectively, when delivering 10W continuously. Stable temperatures were observed in vivo after 70minutes and the maximum skin and implant surface temperatures were 37.73°C and 38.31°C, respectively. This study showed that a hermetic, chronically implantable TET system is thermally safe when continuously delivering 10W of power, sufficient to power modern LVADs.