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Purpose This paper aims to measure the state-level energy efficiency in Indian paper industry and simultaneously explain inter-state variation in efficiency by inefficiency effect model. Three variables, labor productivity, capital intensity and structure of paper industry, are included in inefficiency effect model to assess the likely impact on energy efficiency. Design/methodology/approach Sub-vector input distance function is derived through neo-classical production function which provides measures to estimate energy efficiency. Assuming a translog production function specification, energy efficiency is estimated by using Battese and Coelli (1995) stochastic frontier analysis (SFA). The authors also estimated four other SFA models, and energy efficiency from all the models is compared for robustness checking. Findings The results show the existence of a vast potential to improve energy efficiency. Inefficiency effect model reported a positive impact of structure of the industry and capital intensity on energy efficiency performance, while labor productivity does not have any significant impact on energy efficiency. There exists considerable energy efficiency variation among states. Uttarakhand, Punjab and Orissa are the best performing states while Rajasthan, Jharkhand and Goa have worst energy efficiency performance based on average efficiency. The ranks assigned to states according to inefficiency effects model are found contrary to the simple measure of energy efficiency, i.e. energy intensity. Thus, energy intensity may not always be a good proxy for underlying energy efficiency and need to be compared with a comprehensive possible measure. Originality/value To the best of the authors’ knowledge, this is the first study which measures energy efficiency of Indian paper industry through stochastic frontier model using region-level data. Instead of relying on traditional energy efficiency indicators (energy-output ratio), total-factor energy efficiency approach is used to conduct the empirical exercise. Deviations from the frontier because of factors beyond the scope of producers are also incorporated into analysis to portray the magnitude of random factors in influencing the efficiency performance.

Power consumption is becoming more expensive by the day. This is not far from the fact that power generation is facing a lot of challenges coupled with increasing demand. Industrial sector power demand shares a significant proportion of this generated power. It is therefore a necessary task to manage well industrial energy use through appropriate energy efficiency methods practice so as to minimise energy losses. In this study energy efficiency opportunities in pulp and paper (P&P) mill are identified and the saving potential is then quantified. An energy flow model with the help of an energy audit are used to quantify energy supply, generation, conversion and end use thereby exposing areas of energy losses of the mill. This analysis will serve as an eye opener to future and current P&P making operations in South Africa, and as a base case for stimulating changes toward more efficient energy utilization in the pulp and paper industry. Quite a reasonable energy losses avenues were identified, audited and options of improvements suggested. The results proved that quite a sensible amount of energy is lost in the P&P case study and a near future look into the opportunities and barriers have been noted.

Thanks to their versatile functionality, metal oxides (MOs) constitute one of the key family materials in a variety of current demands for sensor, catalysis, energy storage and conversion, optical electronics, and piezoelectric mechanics. Much effort has focused on engineering specific nanostructure and macroscopic morphology of MOs that aims to enhance their performances, but the design and controlled synthesis of ultrafine nanostructured MOs in a cost-effective and facile way remains a challenge. In this work, we have exploited the advantages of intrinsic structures of graphene oxide (GO) papers, serving as a sacrificial template, to design and synthesize two-dimensional (2D) layered and free-standing MO papers with ultrafine nanostructures. Physicochemical characterizations showed that these MO materials are nanostructured, porous, flexible, and ultralight. The as-synthesized materials were tested for their potential application in photoelectrochemical (PEC) energy conversion. In terms of PEC water splitting, copper oxide papers were used as an example and exhibited excellent performances with an extremely high photocurrent-to-weight ratio of 3 A cm-2 g-1. We have also shown that the synthesis method is generally valid for many earth-abundant transition metals including copper, nickel, iron, cobalt, and manganese.

Recently, radioactive wastes are inevitable by-product due to rapid development and use of nuclear energy. Especially, there are large amount of liquid radioactive wastes to control nuclear fission reaction at nuclear generating station. In order to reduce total volume of solution state radioactive wastes, people have used solar evaporation without any specific instrument and it takes long time to get liquid state concentrated radioactive waste which is inefficient process. Herein we propose Janus-type membrane with different surface hydrophilicity toward efficient solar steam generation to concentrate radioactive liquid wastes. We used vapor deposition polymerization method to introduce polypyrrole (Py) and polystyrene (PS) on the top and bottom side of a cellulose paper. Py coating broadens the absorption wavelength range for enhanced photo-thermal energy conversion. Hydrophobic PS coating not only makes membrane easy to floating on water but also prevents salt accumulation during evaporation. Using this membrane, we can efficiently concentrate polluted water including Cs ion without salt accumulation on membrane, and thus no specific decrement in evaporation efficiency by time.

Being inspired by the “seismonastic reaction” of Mimosa pudica, an asymmetric swelling system was constructed to induce the controllable directional deformation of filter paper. In this work, multifunctional biomimetic Janus paper was facilely fabricated via depositing poly(vinylidene fluoride) (PVDF) on one side of Qualitative Filter Paper (QFP), the permeation of polymer solutions within filter paper was well controlled during fabrication. The wetting and swelling behavior of the prepared Janus paper were detected. The Janus paper showed controllable swelling-induced deformations in water. Both the degree and orientation of the deformation were fully investigated. On the one hand, the degree of deformation depends on the gradient wettability and hygroscopicity of the Janus paper, on the other hand, the orientation of deformation is related to the storage and release of stress. Additionally, the steady deformation during swelling endows the Janus paper with novel shape memory property both under idling and loading conditions. The Janus paper was also applied to achieve reversible energy conversion from the swelling potential energy to mechanical potential energy.

As promising fresh-water purification devices, solar steam generation systems have attracted significant attention recently. However, in practice, the approach often suffers from a poor solar energy conversion efficiency and a low water production rate due to poor material selection and inefficient microscopic structure design. Here, we fabricate an efficient solar steam generation system by "building" polyoxometalate "nano-walls" on rice paper-derived three-dimensional porous carbon paper. In this solar steam generation system, the height of the vertically aligned CoP4 Mo6 "nano-walls" range from 100 to 150 nm with thicknesses about 15 to 25 nm. Under 1 sun irradiation (1 sun = 1 kW m-2 ), the surface temperature increases from 29 to 50 °C in a short time with a solar thermal conversion efficiency achieving 92.8 %. The stability and durability of this solar steam generation system, which withstands fifteen cycle continuous tests, also offer good prospects. Its attractive solar energy conversion performance originates from the intense sunlight absorption and high conversion ability of the CoP4 Mo6 "nano-walls", as well as extremely promising heat localization and water transportation properties of the three-dimensional porous carbon paper. This solar steam generation system, which has produced some inspiring results, is employed for seawater desalination and for purification of water polluted with organic dyes.

Flexible electronics are developing rapidly due to promising applications in displays, sensors, and energy conversion fields. For biodegradable, lightweight, and flexible thin film electronics to be explored, O-(2,3-Dihydroxypropyl) cellulose (DHPC) was synthesized by homogeneous etherification of cellulose in 7 wt % NaOH/12 wt % urea aqueous solution without extra catalyst. DHPC exhibited a high level of transparency, outstanding ductility, and good adhesiveness but poor mechanical properties. Thus, stiff tunicate cellulose nanocrystals (TCNCs) were introduced to construct tough nanocomposite papers. The reinforcement of nanocomposite papers was well predicted by a percolating model, indicating the formation of the network of TCNCs. On the basis of the excellent interfacial compatibility between TCNCs and DHPC, supported by atomic force microscope mapping, the nanocomposite papers exhibited smooth surface, high transparency, as well as satisfactory mechanical properties, which were suitable for the const...

Harvesting energy from environmental moisture is a promising technique for sustainable electric power resource. Herein, a new scalable fabrication method for flexible moisture-electric energy transformation device by dispersing or direct printing carbon dots (CDs) on paper is reported. A facile strategy for self-establishing ionic gradient on both sides of the device by constructing an asymmetric structure (the side of device is encapsulated) is proposed, which avoids prior processing of the materials for building asymmetric functional groups. The carboxyl groups on CDs near the open side of the device ionize more protons than that near the closed side, resulting in a potential drop across the device due to the concentration difference of the released protons on the two sides. The device can produce a sustainable voltage of −40 mV for over 100 min at a fixed humidity value. In addition, the device responds to direct touching of a finger or human exhalation, thus indicating its great potential for applications in electronic skins and humidity sensors.

Nowadays, multi-functional systems driven by solar energy have been explored to alleviate the crisis of energy and freshwater scarcity. However, it remains a great challenge to integrate multi-functions into one hybrid system with a monolithic material, which can harvest, convert and store solar energy synergistically. Here, we firstly propose a multi-functional carbon nanotube paper, which starts from a material level to solve these problems. The carbon nanotube paper is fabricated by vacuum filtration. It exhibits high efficiency of solar-thermal conversion. Secondly, three types of energy conversion/storage systems (e.g., solar-thermal evaporation system, solar-thermoelectric generation system, and supercapacitor) are constructed based on the carbon nanotube paper, which extend the research to a device level. The solar-thermal evaporation system shows an evaporation rate of 1.28 kg m-2h−1 under simulated sunlight irradiation of 1 kW m−2. The solar-thermoelectric generation system demonstrates a stable electric power generation with an output voltage of 100 mV under light irradiation of 1 kW m−2. The supercapacitors perform the energy storage function with an areal specific capacitance of 19.6 mF cm−2. These devices and systems can be used in freshwater generation (0.84 kg m-2h−1, sunlight irradiation of 1 kW m−2), water purification/desalination (inorganic ions rejection larger than 99.9%) and portable solar charging system (maximum output voltage of 5 V). Finally, a hybrid energy system is innovatively proposed from the system level to simultaneously produce freshwater, generate and store electric power. Through the synergetic coupling of solar conversion and storage technologies, the hybrid energy system can supply sustainable freshwater and electricity for remote areas in daily life, highlighting the superiority of multi-energy (thermal energy, electrical energy, and electrochemical energy) complementary.

It is our great pleasure and honor to present this special issue of Heat Transfer Engineering to highlight some of the research works presented at the AIGE 2016 Conference on Energy Conversion, Man...

Construction of flexible electrochemical devices for energy storage and generation is of utmost importance in the modern society. In this article, we report the synthesis of flexible MoS2 based composite paper by high-energy shear force milling and simple vacuum filtration. This composite material combines high flexibility, mechanical strength and good chemical stability. Chronopotentiometric charge-discharge measurements were used to determine the capacitance of our paper material. Highest capacitance of 33 mF cm-2 was achieved at current density of 1 mA cm-2 showing potential application in supercapacitors. We further used the material as a cathode for hydrogen evolution reaction (HER) with an onset potential of ca. -0.2 V vs RHE. The onset potential was even lower (ca. -0.1 V vs RHE) after treatment with n-butyllithium suggesting the introduction of new active sites. Finally, a potential use in Lithium ion batteries (LIB) was examined. Our material can be used directly without any binder, additive carbon or copper current collector and delivers specific capacity of 740 mA h g-1 at a current density of 0.1 A g-1. After 40 cycles at this current density the material still reached a capacity retention of 91%. Our findings show that this composite material could find application in electrochemical energy storage and generation devices where high flexibility and mechanical strength are desired.

This paper investigates the impact of combining CO2 capture and storage with alternative systems for biomass-based combined heat and power production (CHP) in Kraft pulp and paper mills. We compare heat, power, and CO2 balances of systems with alternative configurations of the CHP and CO2-capture systems. Because the captured CO2 comes from renewable biomass, the studied systems yield negative CO2 emissions. It is shown that pulp mills and integrated pulp and paper mills have the potential to become net exporters of biomass-based electricity while at the same time removing CO2 from the atmosphere on a net basis. The study shows that that the overall best CO2 abatement is achieved when CO2 capture is carried out within a biomass integrated gasifier with combined cycle where the syngas undergoes a CO-shift reaction. This configuration combines efficient energy conversion with a high CO2 capture efficiency. Furthermore, cost curves are constructed, which show how the cost of CO2 capture and storage in pulp and paper mills depends on system configuration and the CO2 transportation distance.

Herein, porous WP 2 nanosheet arrays integrated on graphite paper (P-WP 2 NSs/GP) as 3D flexible cathode for electrocatalytic hydrogen evolution reaction (HER) are prepared by in situ phosphidation via vacuum encapsulation assisted by pulsed laser deposition technique. Compared to the electrode without pre-deposition process, the enhanced catalytic activities are attributed to the increased effective catalyst loading and the reinforced charge transport kinetics. The results make the present P-WP 2 NSs/GP as a promising cathode for energy conversion and paves a new way for designing and fabricating efficient electrodes toward HER.

Lithium-Air batteries (LABs) are considered as one of the most promising energy conversion systems for delivering large specific energy. However, practical applications still face major challenges, including poor rate capability, short cycle life and low round-trip efficiencies. Here we report a novel strategy to improve the catalytic activity of MnO2 through the combination of three-dimensional (3D) MnO2 and carbon nanotubes/carbon fiber paper (CNTs/CFP) with binder-free structure. Side reactions related to the binder are precluded in this design. The presence of CNTs not only promotes the formation of 3D structure of air electrode, but directs the uniform deposition of MnO2. When applied as a cathode in LABs, the as-prepared MnO2/CNTs/CFP electrode achieves comparable specific capacity (with a discharge capacity of 8723.5 mAh∙g-1(CNTs+MnO2) at 100mA∙g-1). The encouraging electrochemical performance is found to benefit from free-standing nanoporous structures, which provide more active sites for enabling oxygen reduction. It is also attribute to the decreased side reactions.

Solar photovoltaic technologies could fully deploy and impact the energy conversion systems in our society if mass-produced energy-storage solutions exist. A supercapacitor can regulate the fluctua ...

The International Conference on Polygeneration (ICP) have established as a highly reputed conference series for leading scholars in the field of energy conversion with more than one form and its re...

Graphene nanosheet devices have attracted significant interest in transistor and photodetector applications owing to photothermoelectric effects of graphene. However, their solar energy conversion ability has not been fully explored due to disadvantages of their transparency and zero gap semiconductor in this special field. Here, we propose the potential of graphene-carbon nanotube papers for energy conversion and storage under sunlight and heat. We show that macroscopic 3-dimensional structure of graphene-carbon nanotube papers provides advantages over graphene nanomaterials in converting large area power sources, namely solar and thermal energy into considerable current and voltage. We also report a graphene-carbon nanotube paper stack with p-n interfaces that incorporates a solar/thermal energy cell and a p–n junction capacitor, which can be simultaneously used for energy conversion and storage with a charge-storage capacity of 70.5 μC cm−2 at one sun intensity.

Electrohydrodynamic processing including electrospinning and electrospraying is suitable for depositing controllable structures in fiber or film form. In this work, the electrohydrodynamic approach was used to prepare poly(vinylidene fluoride)/polyaniline composite film. Scanning electron microscopic analysis was performed to show the morphology of the film on soft tissue paper. Self-poling of the film was found due to the high voltage application in the electrohydrodynamic process. The addition of polyaniline into PVDF improves the conductivity of the film significantly. Mechanoelectrical response of the film was demonstrated by measuring the open circuit voltage of the specimens under bending. The peak voltage generated is over 1.2 V due to the bending deformation of the film. The film has ultrafast response to the deformation. It is concluded that the film has multiple functions for mechanoelectrical energy conversion, vibration sensing, and structural integrity monitoring applications.

Energy generation using liquid movement over a graphene surface generally demands a very high rate of flow (e.g.∼100 ml min(-1)). In addition, a continuous flow of liquid is unable to generate a desired voltage, as it needs modification of the substrate such as development of nanopores and criss-cross network structures. Here, we report an ultra-low-cost yet highly efficient portable device for energy conversion, by exploiting the capillary flow of an electrolyte on a filter paper matrix in which a naturally deposited gradient of reduced graphene oxide is induced through chemical synthesis. In addition, the fibres and pores present in the paper offer a criss-cross network, acting as a natural splitter of a continuous flow into tiny droplets. Our methodology thus obviates the need for any elaborate procedure for pre-generation of droplets. Further, we fabricate the necessary electrodes on filter paper by simply scribing pencil tips on the same filter paper, which facilitates the necessary electrochemical reactions. Effectively, at the anode, electrons are released, which travel through the outer circuit for cation reduction at the cathode and deliver an electrical output (voltage/current), realizing the conversion of the chemical form of energy to the electrical form in the filter paper. An absorbent pad at the channel outlet ensures continuous flow of fresh solution in the device, resulting in an inexpensive platform for power generation over a prolonged period of time. A maximum current density of 325 mA cm(-2) and a maximum power density of 53 mW cm(-2) have been observed, which significantly outweigh the capabilities of other reported devices fabricated for similar purposes.

The penetration and diffusion of ink droplet in paper coating have significant influence on the image quality in the inkjet imaging. The flight physical phenomenon of the ink droplet was researched and analyzed according to the hydrodynamic equations of multiphase flow discrete phase in this paper. Base on studying on the surface structure of paper coating, the mechanism of impact, penetration and diffusion between ink droplet and paper coating also was researched in this paper from the perspective of energy conversion in the imaging process. The proposed mathematical model consisted of the factors of hydrodynamic characteristics for ink droplet and the physical characteristics of paper coating, we could get the maximum diameter of ink droplet spreading in paper coating through solving the model and obtain viscous loss and energy consumption in penetration of ink droplet by experiment, and then calculated the average penetration depth of ink droplet.

A simple and scalable method was proposed to fabricate graphene papers, and the graphene sheets were prepared using conventional chemical vapor deposition (CVD) method. The CVD graphene papers possess much higher electrical conductivity of 1097 S cm−1, compared with other reported carbon-related papers (graphene, carbon nanotube, etc.). The graphene papers have good flexibility with only

Recently, great interest has been aroused in flexible/bendable electronic equipment such as rollup displays and wearable devices. As flexible energy conversion and energy storage units with high energy and power density represent indispensable components of flexible electronics, they should be carefully considered. However, it is a great challenge to fabricate flexible/bendable power sources. This is mainly due to the lack of reliable materials that combine both electronically superior conductivity and mechanical flexibility, which also possess high stability in electrochemical environments. In this work, we report a new approach to flexible energy devices. We suggest the use of a flexible electrode based on free-standing graphene paper, to be applied in lithium rechargeable batteries. This is the first report in which graphene paper is adopted as a key element applied in a flexible lithium rechargeable battery. Moreover graphene paper is a functional material, which does not only act as a conducting agent, but also as a current collector. The unique combination of its outstanding properties such as high mechanical strength, large surface area, and superior electrical conductivity make graphene paper, a promising base material for flexible energy storage devices. In essence, we discover that the graphene based flexible electrode exhibits significantly improved performances in electrochemical properties, such as in energy density and power density. Moreover graphene paper has better life cycle compared to non-flexible conventional electrode architecture. Accordingly, we believe that our findings will contribute to the full realization of flexible lithium rechargeable batteries used in bendable electronic equipments.

A method for the analysis of process energy requirements has been used to identify in an early design stage the potential process retrofit measures in an integrated pulp and paper mill. The minimum energy requirements (MER) of the process were computed by means of a dual representation that segregates the thermodynamic requirement of the process from its technological implementation. Energy and exergy recovery opportunities have been examined to improve the integration of the utility system to the process. An MILP optimisation targeting method has been applied to identify the best energy conversion options and to optimise the production of combined heat and power (CHP). Replacing the steam injections to mixing tanks by heat exchangers would decrease the MER by 10%, and increase the combined production of heat and power by a factor 1.7. Improving the exergy efficiency of the paper drying technology would be more difficult to implement, but the results indicate that this could bring an additional 12% gain of electricity cogenerated with no change to the MER.

Maximum power point tracking (MPPT) is a very important necessity in a system of energy conversion from a renewable energy source. Every year a number of publications appear in various journals and conferences claiming to offer better and faster MPPT techniques for wind energy conversion system (WECS). This research paper provides a concise yet comprehensive critical analysis of these techniques with an in-depth review of their strengths and drawbacks. This review is unique as there has been no other research paper so far that offers such a complete and up-to-date investigation of MPPT techniques in WECS. Therefore this research paper can serve as a precise reference for the future research on MPPT for WECS.

The Next Generation Nuclear Plant (NGNP) Project was initiated at Idaho National Laboratory by the U.S. Department of Energy pursuant to the 2005 Energy Policy Act and based on research and development activities supported by the Generation IV Nuclear Energy Systems Initiative. The principal objective of the NGNP Project is to support commercialization of the high temperature gas-cooled reactor (HTGR) technology. The HTGR is helium cooled and graphite moderated and can operate at reactor outlet temperatures much higher than those of conventional light water reactor (LWR) technologies. Accordingly, it can be applied in many industrial applications as a substitute for burning fossil fuels, such as natural gas, in addition to producing electricity, which is the principal application of current LWRs. These varied industrial applications may involve a standard HTGR modular design using different Energy Conversion Systems. Additionally, some of these process heat applications will require process heat delivery systems to lie partially outside the HTGR operator’s facility.

Welcome to this special section of the Journal of Micromechanics and Microengineering (JMM). This section, co-edited by myself and by Professor Jeffrey Lang of the Massachusetts Institute of Technology, contains expanded versions of selected papers presented at the Power MEMS meeting held in Atlanta, GA, USA, in December of 2012. Professor Lang and I had the privilege of co-chairing Power MEMS 2012, the 12th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications. The scope of the PowerMEMS series of workshops ranges from basic principles, to materials and fabrication, to devices and systems, to applications. The many applications of power MEMS (microelectromehcanical systems) range from MEMS-enabled energy harvesting, storage, conversion and conditioning, to integrated systems that manage these processes. Why is the power MEMS field growing in importance? Smaller-scale power and power supplies (microwatts to tens of watts) are gaining in prominence due to many factors, including the ubiquity of low power portable electronic equipment and the proliferation of wireless sensor nodes that require extraction of energy from their embedding environment in order to function. MEMS manufacturing methods can be utilized to improve the performance of traditional power supply elements, such as allowing batteries to charge faster or shrinking the physical size of passive elements in small-scale power supplies. MEMS technologies can be used to fabricate energy harvesters that extract energy from an embedding environment to power wireless sensor nodes, in-body medical implants and other devices, in which the harvesters are on the small scales that are appropriately matched to the overall size of these microsystems. MEMS can enable the manufacturing of energy storage elements from nontraditional materials by bringing appropriate structure and surface morphology to these materials as well as fabricating the electrical interfaces required for their operation and interconnection. Clearly, the marriage of MEMS technologies and energy conversion is a vital application space; and we are pleased to bring you some of the latest results from that space in this special section. Approximately 130 papers were presented at the Power MEMS 2012 conference. From these, the 20 papers you have before you were selected based on paper quality and topical balance. As you can see, papers representing many of the important areas of power MEMS are included: energy harvesters using multiple transduction schemes; MEMS-based fabrication of compact passive elements (inductors, supercapacitors, transformers); MEMS-enabled power diagnostics; MEMS-based batteries; and low power circuitry adapted to interfacing MEMS-based harvesters to overall systems. All of the papers you will read in this special section comprise substantial expansion from the proceedings articles and were reviewed through JMM's normal reviewing process. Both Professor Lang and I hope that you will share our enthusiasm for the field of power MEMS and that you will find this special section of JMM exciting, interesting and useful. Sincerely, Mark G Allen

This special section of Journal of Micromechanics and Microengineering features papers selected from the 11th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2011), held at Sejong Hotel in Seoul, Korea during 15–18 November 2011. Since the first PowerMEMS workshop held in Sendai, Japan in 2000, the workshop has developed as the premier forum for reporting research results in micro and nanotechnology for power generation, energy conversion, harvesting and processing applications, including in-depth technical issues on nanostructures and materials for small-scale high-density energy and thermal management. Potential PowerMEMS applications cover not only portable power devices for consumer electronics and remote sensors, but also micro engines, impulsive thrusters and fuel cells for systems ranging from the nanometer to the millimeter scale. The 2011 technical program consists of 1 plenary talk, 4 invited talks and 118 contributed presentations. The 48 oral and 70 poster presentations, selected by 27 Technical Program Committee Members from 131 submitted abstracts, have stimulated lively discussion maximizing the interaction between participants. Among them, this special section includes 9 papers covering micro-scale power generators, energy converters, harvesters, thrusters and thermal coolers. Finally, we are grateful to the members of the International Steering Committee, the Technical Program Committee, and the Local Organizing Committee for their efforts and contributions to PowerMEMS 2011. We also thank the two companies Samsung Electro-Mechanics and LG Elite for technical tour arrangements. Special thanks go to Dr Ian Forbes, the editorial staff of the Journal of Micromechanics and Microengineering, as well as to the staff of IOP Publishing for making this special section possible.

Nanogenerators capable of harvesting energy from environmental mechanical energy are attractive for many applications. In this paper, we present a simple, low-cost approach to convert low-frequency mechanical energy into electric power using piezoelectric ZnO nanorods grown on a common paper substrate. This energy conversion device has ultrahigh flexibility and piezoelectric sensitivity and can produce an output voltage of up to 10 mV and an output current of about 10 nA. It is demonstrated that the device's electric output behavior can be optionally changed between four types of mode simply by controlling the straining rate. Furthermore, it is also shown that the electric output can be enhanced by scaling the size of the device. This energy-harvesting technology provides a simple and cost-effective platform to capture low-frequency mechanical energy, such as body movements, for practical applications.

This special section of Journal of Micromechanics and Microengineering features papers selected from the 10th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2010). The workshop was organized in Leuven, Belgium from 30 November to 3 December 2010 by Katholieke Universiteit Leuven and the imec/Holst Centre. This was a special PowerMEMS Workshop, for several reasons. First of all, we celebrated the 10th anniversary of the workshop: the first PowerMEMS meeting was organized in Sendai, Japan in 2000. None of the organizers or participants of this first meeting could have predicted the impact of the workshop over the next decade. The second reason was that, for the first time, the conference organization spanned two countries: Belgium and the Netherlands. Thanks to the advances in information technology, teams from Katholieke Universiteit Leuven (Belgium) and the imec/Holst Centre in Eindhoven (the Netherlands) have been able to work together seamlessly as one team. The objective of the PowerMEMS Workshop is to stimulate innovation in micro and nanotechnology for power generation and energy conversion applications. Its scope ranges from integrated microelectromechanical systems (MEMS) for power generation, dissipation, harvesting, and management, to novel nanostructures and materials for energy-related applications. True to the objective of the PowerMEMSWorkshop, the 2010 technical program covered a broad range of energy related research, ranging from the nanometer to the millimeter scale, discussed in 5 invited and 52 oral presentations, and 112 posters. This special section includes 14 papers covering vibration energy harvesters, thermal applications and micro power systems. Finally, we wish to express sincere appreciation to the members of the International Steering Committee, the Technical Program Committee and last but not least the Local Organizing Committee. This special issue was edited in collaboration with the staff of IOP Publishing. PowerMEMS 2010 contents Harvesting energy from airflow with a michromachined piezoelectric harvester inside a Helmholtz resonator S P Matova, R Elfrink, R J M Vullers and R van Schaijk Analysis and characterization of triangular electrode structures for electrostatic energy harvestingDaniel Hoffmann, Bernd Folkmer and Yiannos Manoli A smart and self-sufficient frequency tunable vibration energy harvesterC Eichhorn, R Tchagsim, N Wilhelm and P Woias Power output enhancement of a vibration-driven electret generator for wireless sensor applicationsTatsuakira Masaki, Kenji Sakurai, Toru Yokoyama, Masayo Ikuta, Hiroshi Sameshima, Masashi Doi, Tomonori Seki and Masatoshi Oba Harvesting traffic-induced vibrations for structural health monitoring of bridgesT V Galchev, J McCullagh, R L Peterson and K Najafi Dispenser-printed planar thick-film thermoelectric energy generatorsA Chen, D Madan, P K Wright and J W Evans Silicon nanowire arrays as thermoelectric material for a power microgeneratorD Davila, A Tarancon, M Fernandez-Regulez, C Calaza, M Salleras, A San Paulo and L Fonseca A micro thermal switch with a stiffness-enhanced thermal isolation structureTakashiro Tsukamoto, Masayoshi Esashi and Shuji Tanaka A dielectric liquid contact thermal switch with electrowetting actuationA R McLanahan, C D Richards and R F Richards A self-regulating valve for single-phase liquid cooling of microelectronicsRadu Donose, Michael De Volder, Jan Peirs and Dominiek Reynaerts A MEMS-enabled 3D zinc–air microbattery with improved discharge characteristics based on a multilayer metallic substructureA Armutlulu, Y Fang, S H Kim, C H Ji, S A Bidstrup Allen and M G Allen Design, fabrication and testing of an air-breathing micro direct methanol fuel cell with compound anode flow fieldLuwen Wang, Yufeng Zhang, Youran Zhao, Zijiang An, Zhiping Zhou and Xiaowei Liu A shadow-mask evaporated pyroMEMS igniterD A de Koninck, D Briand and N F de Rooij Aerodynamic journal bearing with a flexible, damped support operating at 7.2 million DNTobias Waumans, Jan Peirs, Farid Al-Bender and Dominiek Reynaerts Thermoelectric energy harvester on the heated human machineVladimir Leonov

This special section of the Journal of Micromechanics and Microengineering presents papers selected from the 9th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2009), which was held in Washington DC, USA from 1?4 December 2009. Since it was first held in Sendai, Japan in 2000, the PowerMEMS workshop has focused on small-scale systems that process, convert, or generate macroscopically significant amounts of power, typically with high power density or high energy density. In the workshop's early years, much of the research presented was on small-scale fueled systems, such as micro heat engines and micro fuel cells. The past nine years have seen a dramatic expansion in the range of technologies that are brought to bear on the challenge of high-power, small-scale systems, as well as an increase in the applications for such technologies. At this year's workshop, 158 contributed papers were presented, along with invited and plenary presentations. The papers focused on applications from micro heat engines and fuel cells, to energy harvesting and its enabling electronics, to thermal management and propulsion. Also presented were the technologies that enable these applications, such as the structuring of microscale, nanoscale and biological systems for power applications, as well as combustion and catalysis at small scales. This special section includes a selection of 12 expanded papers representing energy harvesting, chemical and fueled systems, and elastic energy storage at small scales. We would like to express our appreciation to the members of the International Steering Committee, the Technical Program Committee, the Local Organizing Committee, and to the workshop's financial supporters. We are grateful to the referees for their contributions to the review process. Finally, we would like to thank Dr Ian Forbes, the editorial staff of the Journal of Micromechanics and Microengineering, and the staff of IOP Publishing for making this special section possible.

This special issue of the Journal of Micromechanics and Microengineering features papers selected from The 8th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2008) with the 2nd Symposium on Micro Environmental Machine Systems (μMEMS 2008). The workshop was held in Sendai, Japan on 9–12 November 2008 by Tohoku University. This is the second time that the PowerMEMS workshop has been held in Sendai, following the first workshop in 2000. Power MEMS is one of the newest categories of MEMS, which encompasses microdevices and microsystems for power generation, energy conversion and propulsion. The first concept of Power MEMS was born in the late 1990's from a MEMS-based gas turbine project at Massachusetts Institute of Technology. After that, the research and development of Power MEMS have been promoted by the strong need for compact power sources with high energy and/or power density. Since its inception, Power MEMS has expanded to include not only various MEMS-based power generators but also small energy machines and microdevices for macro power generators. Previously, the main topics of the PowerMEMS workshop were miniaturized gas turbines and micro fuel cells, but recently, energy harvesting has been the hottest topic. In 2008, energy harvesting had a 41% share in the 118 accepted regular papers. This special issue includes 19 papers on various topics. Finally, I would like to express my sincere appreciation to the members of the International Steering Committee, the Technical Program Committee, the Local Organizing Committee and financial supporters. This special issue was edited in collaboration with the staff of IOP Publishing.

This letter gives the correction to a few mistakes in the illustrations of a paper published by the authors in the IEEE Transactions on Energy Conversion, vol.17, p.90-4, Mar. 2002.

Flexible thermoelectric materials are presented with potential applications in electronic devices and energy conversion due to their convenient preparation, good flexibility, and various forms. However, as ductility is rarely observed in inorganic semiconductors and ceramic insulators, reports on applications of inorganic oxide materials in flexible thermoelectric materials are sparse. Here, we report a new method for the synthesis of a flexible Na1.4Co2O4 thermoelectric material based on Na1.4Co2O4 bulk materials, which are prepared by a self-flux method and painted on print paper. Seebeck coefficient and power factor of the obtained thermoelectric material are 78–102 μVK-1 and 159–223 μWm-1K-2, respectively, in a temperature range of 303–522 K, which are superior to those values of other conductive polymers and their compounds. More interestingly, the n-type Na1.4Co2O4 flexible material is obtained in the painting process at higher pressure with Seebeck coefficients of –109 to –183 μVK-1 in a temperature range of 303–522 K. The convenient preparation method of these novel flexible thermoelectric materials may be expanded to the synthesis of other flexible thermoelectric materials, which will be the focus of future work.

Along with the chic fad energy industry field, the graphene application in energy conversion and management does bring about some benefits in terms of the energy transfer and storage development, the achievement it exerts on the multifaceted innovate approaches. Both current and previous studies on energy conversion, energy storage and energy transfer development, many research results are sufficient to show that all graphene products including graphene paper, film, foam and fiber have a significant role in improving performance. In the energy conversion research on the graphene paper, it has been recently demonstrated that putting the graphene into triboelectric nanogenerators practice possesses higher output performance than traditional generator, which has a maximum strain as large as 200% without evident degradation of the electrical properties. In terms of energy transfer, the graphene fiber application on the battery can significantly increase the charge and discharge rates with enhanced storage capacity of 763 F g−1. On the energy storage research, the graphene foam can enhance a high density of solar thermal storage up to 269.8 kJ kg−1 for long-term. Nano-graphene and graphene coating provide feasibility for the miniaturization of energy storage equipment which inspired the possibility for portable and foldable devices. The work done in this paper can effectively help promote the application of graphene in energy field. Based on our work, the researchers can choose graphene products (graphene paper, graphene film, graphene foam or graphene fiber) efficiently according to the research object in the future.

This paper investigates the thermochemical characteristics of date palm fronds (DPFs) to use as feedstock for different energy conversion processes. The proximate analysis, ultimate analysis, calorific value measurements, and elemental content measurements were carried out using some quantitative and qualitative techniques. At later stage, the gasification of DPFs was carried out in an externally hot gasifier system. The effect of gasification temperature and biomass particle size on gas composition and heating value of producer gas was investigated. The results showed that the thermochemical characteristics of DPFs were comparable with other biomass materials reported in the past literature. The gasification trials of the biomass revealed that temperature has a significant effect on gas composition, especially H2 and CO contents. The high temperature yielded high H2 and CO concentrations in the product gas. A good quality gas composition (in terms of H2, CO, CH4, and CO2 contents) was obtained from bigger particle sizes as compared to smaller sizes. The thermochemical characteristics of DPFs and gasification results showed that DPF feedstock is comparable with other conventional biomass for production of energy through appropriate thermochemical technologies.

Sun drying is popularly used in Lombok to dry food items including jackfruitDodolbecause it is easy and cheap. This type of drying has a weakness, which is very weather dependent. When it is cloudy or rainy, the drying process will stop, which will affect the income level of the jackfruitDodolbusiness. To overcome this, it is done through the application of a dryer with rice husk energy. Rice husks can be an alternative energy in drying process because they are easy to obtain and cheap. To make rice husks as drying energy, it can be done through an energy conversion process using a heat exchanger that is placed in a furnace. Tests were carried out in the drying process to produce a dry product of 5 kg of jackfruitDodol. The drying temperature is obtained from the result of the energy conversion process between burning rice husks in a furnace with environmental air flowing in the heat exchanger pipe. The resulting hot air flows into the drying chamber. This makes the product more hygienic and drying process can be all the time. The implication of the application of the rice husk energy dryer is to increase the jackfruitDodolbusiness income. This dryer provides a return on investment (ROI) rate of 304.48% with the break-even point (BEP) occurring at 0.2778 years or 3.3336 months. This means k Dodolis feasible.

Dr. S.R. Caplan (Israel) summarised his work on the self adaptive control of energy conversion and its relation to the mechanical behaviour of muscle.

Silicone fluids have numerous electrical applications in both energy conversion equipment and communications type apparatus. To aid engineers in the application of these fluids and to determine the general characteristics of these dielectrics, a study was made of their electrical properties. The measurements were made on fluids of commercial purity.

Graphene is usually embedded into polymer matrices for the development of thermally conductive composites, preferably forming an interconnected and anisotropic framework. Currently, the directional self‐assembly of exfoliated graphene sheets is demonstrated to be the most effective way to synthesize anisotropic graphene frameworks. However, achieving a thermal conductivity enhancement (TCE) over 1500% with per 1 vol% graphene content in polymer matrices remains challenging, due to the high junction thermal resistance between the adjacent graphene sheets within the self‐assembled graphene framework. Here, a multiscale structural modulation strategy for obtaining highly ordered structure of graphene framework and simultaneously reducing the junction thermal resistance is demonstrated. The resultant anisotropic framework contributes to the polymer composites with a record‐high thermal conductivity of 56.8–62.4 W m−1 K−1 at the graphene loading of ≈13.3 vol%, giving an ultrahigh TCE per 1 vol% graphene over 2400%. Furthermore, thermal energy management applications of the composites as phase change materials for solar‐thermal energy conversion and as thermal interface materials for electronic device cooling are demonstrated. The finding provides valuable guidance for designing high‐performance thermally conductive composites and raises their possibility for practical use in thermal energy storage and thermal management of electronics., The dual‐assembled graphene framework (DAGF), which combines a highly oriented graphene structure along the vertical direction and a low junction thermal resistance between the graphene building blocks, exhibits excellent performance in improving the thermal conductivity of polymers. The resultant composites have a record‐high thermal conductivity of 56.8–62.4 W m−1 K−1(≈13.3 vol%), significantly outperforming previously reported results.

Representative models of the nonlinear behavior of floating platforms are essential for their successful design, especially in the emerging field of wave energy conversion where nonlinear dynamics can have substantially detrimental effects on the converter efficiency. The spar buoy, commonly used for deep-water drilling, oil and natural gas extraction and storage, as well as offshore wind and wave energy generation, is known to be prone to experience parametric resonance. In the vast majority of cases, parametric resonance is studied by means of simplified analytical models, considering only two degrees of freedom (DoFs) of archetypical geometries, while neglecting collateral complexity of ancillary systems. On the contrary, this paper implements a representative 7-DoF nonlinear hydrodynamic model of the full complexity of a realistic spar buoy wave energy converter, which is used to verify the likelihood of parametric instability, quantify the severity of the parametrically excited response and evaluate its consequences on power conversion efficiency. It is found that the numerical model agrees with expected conditions for parametric instability from simplified analytical models. The model is then used as a design tool to determine the best ballast configuration, limiting detrimental effects of parametric resonance while maximizing power conversion efficiency.

Reverse electrodialysis is a promising method to harvest the osmotic energy stored between seawater and freshwater, but it has been a long‐standing challenge to fabricate permselective membranes with the power density surpassing the industry benchmark of 5.0 W m−2 for half a century. Herein, a vertically transported graphene oxide (V‐GO) with the combination of high ion selectivity and ultrafast ion permeation is reported, whose permeation is three orders of magnitude higher than the extensively studied horizontally transported GO (H‐GO). By mixing artificial seawater and river water, an unprecedented high output power density of 10.6 W m−2 is obtained, outperforming all existing materials. Molecular dynamics (MD) simulations reveal the mechanism of the ultrafast transport in V‐GO results from the quick entering of ions and the large accessible area as well as the apparent short diffusion paths in V‐GO. These results will facilitate the practical application of osmotic energy and bring an innovative design strategy for various systems involving ultrafast transport, such as filtration and catalysis., Vertically transported graphene oxide is prepared to extract osmotic energy from mixing artificial seawater and river water with an unprecedentedly high power density of 10.6 W m−2. It surpasses the industry benchmark of 5.0 W m−2 and outperforms all the reported nanoporous membranes. Under more optimized conditions, the power density can be further enhanced to be 34 W m−2.