Efficiency optimization for bidirectional IPT system

Compared with unidirectional inductive power transfer (UIPT) systems which are suitable for passive loads, bidirectional IPT (BIPT) systems can be used for active loads with power regenerative capability. There are numerous BIPT systems that have been proposed previously to achieve improved performance. However, typical BIPT systems are controlled through modulation of phase-shift of each converter while keeping the relative phase angle between voltages produced by two converters at ± 90 degrees. This paper presents theoretical analysis to show that there is a unique phase shift for each converter at which the inductive coils losses of the system is minimized for a given load. Simulated results of a BIPT system, compensated by CLCL resonant networks, are presented to demonstrate the applicability of the proposed concept and the validity of the mathematical model.

Cascaded multilevel converter based bidirectional inductive power transfer (BIPT) system

A typical low power IPT system employs an H-Bridge converter with a simple control strategy to generate a high frequency current from DC power supply. This paper proposes a cascaded multilevel converter for bidirectional IPT (BIPT) systems, which is suitable for low to medium power applications as well as for situations such as PV cells where several individual DC sources are to be utilized. A novel modulation strategy is proposed for the multilevel converter with the aim of minimizing switching losses. Series - Series (SS) compensation circuit is adopted for the IPT system and a mathematical model is presented to minimize the coil losses of the system under varying output power. Theoretical results presented in comparison to the simulations to demonstrate the applicability of the proposed concept and the validity of the developed model. The experimental results show the feasibility of the proposed phase shift modulation.

Design and modification of three-component randomly incorporated copolymers for high performance organic photovoltaic applications

In this study we report the molecular design, synthesis, characterization, and photovoltaic properties of a series of diketopyrrolopyrrole (DPP) and dithienothiophene (DTT) based donor-acceptor random copolymers. The six random copolymers are obtained via Stille coupling polymerization using various concentration ratios of donor to acceptor in the conjugated backbone. Bis(trimethylstannyl)thiophene was used as the bridge block to link randomly with the two comonomers 5-(bromothien-2-yl)-2,5-dialkylpyrrolo[3,4-c]pyrrole-1, 4-dione and 2,6-dibromo-3,5-dipentadecyl-dithieno[3,2-b;2′,3′-d] thiophene. The optical properties of these copolymers clearly reveal a change in the absorption band through optimization of the donor-acceptor ratio in the backbone. Additionally, the solution processability of the copolymers is modified through the attachment of different bulky alkyl chains to the lactam N-atoms of the DPP moiety. Applications of the polymers as light-harvesting and electron-donating materials in solar cells, in conjunction with PCBM as acceptor, show power conversion efficiencies (PCEs) of up to 5.02%.

Furan containing diketopyrrolopyrrole copolymers : synthesis, characterization, organic field effect transistor performance and photovoltaic properties

In this work, we report design, synthesis and characterization of solution processable low band gap polymer semiconductors, poly{3,6-difuran-2-yl-2,5-di(2- octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-phenylene} (PDPP-FPF), poly{3,6-difuran-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1, 4-dione-alt-naphthalene} (PDPP-FNF) and poly{3,6-difuran-2-yl-2,5-di(2- octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-anthracene} (PDPP-FAF) using the furan-containing 3,6-di(furan-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DBF) building block. As DBF acts as an acceptor moiety, a series of donor-acceptor (D-A) copolymers can be generated when it is attached alternatively with phenylene, naphthalene or anthracene donor comonomer blocks. Optical and electrochemical characterization of thin films of these polymers reveals band gaps in the range of 1.55-1.64 eV. These polymers exhibit excellent hole mobility when used as the active layer in organic thin-film transistor (OTFT) devices. Among the series, the highest hole mobility of 0.11 cm 2 V -1 s -1 is achieved in bottom gate and top-contact OTFT devices using PDPP-FNF. When these polymers are used as a donor and [70]PCBM as the acceptor in organic photovoltaic (OPV) devices, power conversion efficiencies (PCE) of 2.5 and 2.6% are obtained for PDPP-FAF and PDPP-FNF polymers, respectively. Such mobility values in OTFTs and performance in OPV make furan-containing DBF a very promising block for designing new polymer semiconductors for a wide range of organic electronic applications.

Thiophene-benzothiadiazole-thiophene (D-A-D) based polymers : Effect of donor/acceptor moieties adjacent to D-A-D segment on photophysical and photovoltaic properties

New push-pull copolymers based on thiophene (donor) and benzothiadiazole (acceptor) units, poly[4,7-bis(3-dodecylthiophene-2-yl) benzothiadiazole-co- thiophene] (PT3B1) and poly[4,7-bis(3-dodecylthiophene-2-yl) benzothiadiazole-co-benzothiadiazole] (PT2B2), are designed and synthesized via Stille and Suzuki coupling routes respectively. Gel permeation chromatography shows the number average molecular weights are 31100 and 8400 g mol-1 for the two polymers, respectively. Both polymers have shown absorption throughout a wide range of the UV-vis region, from 300 to 650 nm. A significant red shift of the absorption edge is observed in thin films compared to solution of the copolymers; the optical band gap is in the range of 1.7 to 1.8 eV. Cyclic voltammetry indicates reversible oxidation and reduction processes with HOMO energy levels calculated to be in the range of 5.2 to 5.4 eV. Upon testing both materials for organic field-effect transistors (OFETs), PT3B1 showed a hole mobility of 6.1 × 10-4 cm2 V-1 s -1, while PT2B2 did not show any field effect transport. Both copolymers displayed a photovoltaic response when combined with a methanofullerene as an electron acceptor. The best performance was achieved when the copolymer PT3B1 was blended with [70]PCBM in a 1:4 ratio, exhibiting a short-circuit current of 7.27 mA cm-2, an open circuit voltage of 0.85 V, and a fill factor of 41% yielding a power conversion efficiency of 2.54% under simulated air mass (AM) 1.5 global (1.5 G) illumination conditions (100 mW cm-2). Similar devices utilizing PT2B2 in place of PT3B1 demonstrated reduced performance with a short-circuit current of 4.8 mA cm -2, an open circuit voltage of 0.73 V, and a fill factor of 30% resulting in a power conversion efficiency of roughly 1.06%.

Relation between charge carrier mobility and lifetime in organic photovoltaics

The relationship between charge carrier lifetime and mobility in a bulk heterojunction based organic solar cell, utilizing diketopyrrolopyrole- naphthalene co-polymer and PC71BM in the photoactive blend layer, is investigated using the photoinduced charge extraction by linearly increasing voltage technique. Light intensity, delay time, and temperature dependent experiments are used to quantify the charge carrier mobility and density as well as the temperature dependence of both. From the saturation of photoinduced current at high laser intensities, it is shown that Langevin-type bimolecular recombination is present in the studied system. The charge carrier lifetime, especially in Langevin systems, is discussed to be an ambiguous and unreliable parameter to determine the performance of organic solar cells, because of the dependence of charge carrier lifetime on charge carrier density, mobility, and type of recombination. It is revealed that the relation between charge mobility (μ) and lifetime (τ) is inversely proportional, where the μτ product is independent of temperature. The results indicate that in photovoltaic systems with Langevin type bimolecular recombination, the strategies to increase the charge lifetime might not be beneficial because of an accompanying reduction in charge carrier mobility. Instead, the focus on non-Langevin mechanisms of recombination is crucial, because this allows an increase in the charge extraction rate by improving the carrier lifetime, density, and mobility simultaneously. © 2013 AIP Publishing LLC.

Nanoscale phase domain structure and associated device performance of organic solar cells based on a diketopyrrolopyrrole polymer

We investigate the blend morphology and performance of bulk heterojunction organic photovoltaic devices comprising the donor polymer, pDPP-TNT (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1, 4-dione-alt-naphthalene}) and the fullerene acceptor, [70]PCBM ([6,6]-phenyl C71-butyric acid methyl ester). The blend morphology is heavily dependent upon the solvent system used in the fabrication of thin films. Thin films spin-coated from chloroform possess a cobblestone-like morphology, consisting of thick, round-shaped [70]PCBM-rich mounds separated by thin polymer-rich valleys. The size of the [70]PCBM domains is found to depend on the overall film thickness. Thin films spin-coated from a chloroform:dichlorobenzene mixed solvent system are smooth and consist of a network of pDPP-TNT nanofibers embedded in a [70]PCBM-rich matrix. Rinsing the films in hexane selectively removes [70]PCBM and allows for analysis of domain size and purity. It also provides a means for investigating exciton dissociation efficiency through relative photoluminescence yield measurements. Devices fabricated from chloroform solutions show much poorer performance than the devices fabricated from the mixed solvent system; this disparity in performance is seen to be more pronounced with increasing film thickness. The primary cause for the improved performance of devices fabricated from mixed solvents is attributed to the greater donor-acceptor interfacial area and resulting greater capacity for charge carrier generation.

My System of Career Influences MSCI (Adult) Facilitator's Guide

Career development in the 21st century presents many challenges and opportunities to adults. They must now navigate a complex and rapidly changing world of work influenced by technology, globalisation and fluctuating economic conditions. The My System of Career Influences (MSCI) (Adult) is a qualitative career assessment tool based on the constructivist theory from cognitive psychology. Acknowledged as the third wave in cognitive science after psychoanalysis and behaviourism, constructivism emphasises the individual in the assessment and counselling process. Individuals actively participate in the construction of their own reality and are encouraged to respond to and deal with both anticipated and unanticipated events that influence their careers. The tool comprises a facilitator guide and participant workbooks. The guide describes the Systems Theory Framework of career development that provides the theoretical background to the MSCI as well as a step-by-step user guide to conducting the MSCI (Adult) process with individuals and groups. Each participant uses the accompanying MSCI (Adult) Workbook (sold separately) which they can complete and keep for later reference. With its attention to an holistic and storied approach to career intervention My System of Career Influences (MSCI) (Adult) is an essential resource for all career practitioners working with adults in today's workplaces.

My System of Career Influences MSCI (Adult) Workbook

NOTE: This client booklet is to be used in conjunction with the MSCI (Adult) Facilitators Guide. Career development in the 21st century presents many challenges and opportunities. Throughout your life you will make countless decisions and experience numerous transitions. Each decision may be subject to a range of influences, for example people we know may give us an opinion, we may be attracted to a particular place or a particular salary, or we may simply want a change. No two people will have the same pattern of influences. The My System of Career Influences MSCI (Adult) is a qualitative career assessment reflection process based on recent developments in theory and practice. It uses a constructivist view and encourages a narrative and story-based approach to your career development. It has been used successfully with employees by career development practitioners working in a range of businesses and organisations from large to small and in one-on-one career counselling sessions as well as in a group setting.

A Tradable Permit System in an Intertemporal Economy

It is known that in an intertemporal competitive economy, a tradable permit system may not achieve efficiency without setting appropriate permit interest rates (i.e., rewards for holding permits). To find the rates, however, we need to know in advance the path of efficient permit prices, which is difficult to obtain. This study intends to solve this problem in two ways. First, we analyze a special case in which the permit interest rates are given by a simple rule. For example, if the marginal abatement cost of pollution emission is constant, then the appropriate rate is to equal the monetary interest rate. As is the case for global warming, if the damage is caused in the future far beyond the planning period of the environmental program, the appropriate rate coincides with the marginal self-recovery of environmental stock under certain conditions. As a second approach, we propose a tradable permit system with a permit bank, as a mechanism by which the permit interest rates are generated endogenously without governmental intervention other than the issuance of permits. However, we also show that this approach raises the problem of indeterminacy of the equilibrium. © 2013 Springer Science+Business Media Dordrecht.

Use of the biolistic particle delivery system to transform fungal genomes

Biolistic delivery of transforming DNA into fungal genomes, especially when performed on uninucleate haploid conidia, has proven successful in bypassing the time-consuming repetitive purification of protoplasts used for the widely applied polyethylene glycol-mediated method. Biolistic transformation is also relatively quick compared to other available methods and provides a high percentage of stable transformants.

Environmental information provision, market valuation, and firm incentives: An empirical study of the Japanese PRTR system

The environmental performance of a listed firm could affect its level of investment in pollution prevention and its access to financial markets. Previous studies using Tobin's q that explore market response to environmental performance do not distinguish between the impact of performance on investment and market response, which may mislead conclusions. To overcome this problem, we simultaneously estimate the functions of the intangible asset, the replacement cost, and the toxic chemical risk. We find that the Japanese financial market does not value risk associated with toxic chemical releases. Nevertheless, even without market valuation, firms increase investment to reduce pollution. © 2010 by the Board of Regents of the University of Wisconsin System.

The pollution release and transfer register system in the U.S. and Japan : an analysis of productivity

This study analyzes Total Factor Productivity (TFP), which includes all categories of productivity. Our measure investigates productivity in the context of the provision and dissemination of environmental information policies. We investigated data on the emission of toxic chemical substances for the U.S. and Japanese manufacturing firms, including 386 firms for the period 1999-2007 and 466 firms for the period 2001-2008. The results show that productivity improved in all nine industrial sectors and that pollution levels were high in the U.S. and Japan from 2001 to 2007. In particular, the electronics industry improved rapidly after 2002 in both countries, which may be attributed to the enforcement of RoHS and the REACH directive in Europe. As a result of these stringent policies on toxic chemical emissions, the U.S. and Japanese firms, many of which export to the European market, have strong incentives to reduce their toxic chemical emissions.