Selective separation of plastic LED lamp components using electrodynamic fragmentation for material recovery.

The recycling of light-emitting diode (LED) lamps and tubes is becoming increasingly important due to their growing market share as energy-efficient lighting technology. Here we report on the use of high voltage electric-pulse fragmentation to recover elementary components such as LED chips and printed circuit boards (drivers). E27 LED lamps with plastic bulbs, which represent 48% of deposits collected by a French company, are used as a case study. More than 150 lamps were tested on a laboratory reactor for electrodynamic fragmentation. The technological process in which highly energetic electrical pulses were applied to materials immersed in water was studied in order to separate the components of the LED lamps using a minimal specific energy. The estimated energy necessary to achieve total separation assessed at 64%, without grinding pretreatment, was 5.2 ± 0.6 kWh per ton, representing a mass recycling rate of 74%. Based on the disassembled material, the commercial value of the recovered materials was thus estimated. Gold, as the most representative material, was found to represent 0.03% of the mass fraction for 83.6% of the total commercial value. The process disassembling capacity is a key issue to increase the recycling rate of current LED lamps and tubes.

When and how to repower energy systems? A four strategies-based decision model.

Repowering systems is a long-lasting managerial endeavor where decision-makers face maintenance and optimization problems. The decision time to repower an energy system is one of the most important matters in this field. Also, in the real-world, each component of the system has different versions available in the market, so choosing the best version of components can be one of the valuable and practical issues in repowering a system. Therefore, decision-makers need optimal repowering policies in order to generate the optimal combination of system's components as well as the optimal time to repower this system with respect to important concerns such as cost, availability and safety issues. This paper provides a first-step decision-making model based on four independent repowering strategies for energy systems. A case study from offshore wind turbine system is presented afterwards to demonstrate the effectiveness of the presented policies. This decision support tool deals with the optimal repowering time and the best combination of components based on cost, availability, and safety constraints.

Wind farm topology-finding algorithm considering performance, costs, and environmental impacts.

Optimal power in wind farms turns to be a modern problem for investors and decision makers; onshore wind farms are subject to performance and economic and environmental constraints. The aim of this work is to define the best installed capacity (best topology) with maximum performance and profits and consider environmental impacts as well. In this article, we continue the work recently done on wind farm topology-finding algorithm. The proposed resolution technique is based on finding the best topology of the system that maximizes the wind farm performance (availability) under the constraints of costs and capital investments. Global warming potential of wind farm is calculated and taken into account in the results. A case study is done using data and constraints similar to those collected from wind farm constructors, managers, and maintainers. Multi-state systems (MSS), universal generating function (UGF), wind, and load charge functions are applied. An economic study was conducted to assess the wind farm investment. Net present value (NPV) and levelized cost of energy (LCOE) were calculated for best topologies found.

Quantitative modeling of reflected ultrasonic bounded beams and a new estimate of the Schoch shift.

The wavefields of bounded acoustic beams and pulses reflected from water-loaded plates are fully modeled with the phase advance technique. The wavefield produced at the source is propagated at any incidence angle using phase shift modeling that incorporates the full analytic solution for the acoustic reflectivity at the interface. This approach provides for the ready visualization of both the stationary monofrequency beam wavefield and animation of the temporally bounded pulse. The model images are reminiscent of the classic Schlieren photographs that first illustrated the nonspecular behavior of the reflected beams incident near critical angles. Various phenomena such as the lateral displacement and the null zone at the Rayleigh critical angle are recreated. A new approximation for this shift agrees well with that of the peak energy of the reflected beam. Similar effects are observed during the reflection of a bounded pulse. Although more computationally costly than existing analytic approximations, the phase advance technique can facilitate the interpretation of reflectivity measurements obtained in laboratory experiments. In particular, the full visualization allows for a better understanding of the behavior of reflected waves at any angle of incidence.

A large ultrasonic bounded acoustic pulse transducer for acoustic transmission goniometry: modeling and calibration.

A large, flat ultrasonic transmitter and a small receiver are developed for studies of material properties in acoustic transmission goniometry. While the character of the wave field produced by the transmitter can be considered as a plane wave as observed by the receiver, diffraction effects are noticeable near critical angles and result in the appearance of weak but detectable arrivals. Transmitted ultrasonic waveforms are acquired in one elastic silicate glass and two visco-elastic acrylic glass sample plates as a function of the angle of incidence. Phase velocities are determined from modeling of the shape of curves of the observed arrival times versus angle of incidence. The waveform observations are modeled using a phase propagation technique that incorporates full wave behavior including attenuation. Subtle diffraction effects are captured in addition to the main bounded pulse propagation. The full propagation modeling allows for various arrivals to be unambiguously interpreted. The results of the plane wave solution are close to the full wave propagation modeling without any corrections to the observed wave field. This is an advantage as it places confidence that later analyses can use simpler plane wave solutions without the need for additional diffraction corrections. A further advantage is that the uniform bounded acoustic pulse allows for the detection of weak arrivals such as a low energy edge diffraction observed in our experiments.