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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.

Based on the energy and environmental audit, analysis of material flows, energy conversion, emissions into atmosphere and lithosphere in the production of instant coffee was carried out.To raise energy efficiency and reduce environmental burden, innovative flow diagrams and equipment for waste processing and production of new coffee products have been developed.Experimental modeling was carried out: kinetics of microwave extraction of water-soluble substances and oil from coffee slurry; hydraulics of the extractant flow through cassettes of the microwave extractor. The experimental data were summarized in the form of a criterion equation.As a result of experimental modeling of the extraction kinetics, it was found that the duration of the process in a microwave field is approximately 20 times less than in a thermostat. The microwave field affects the extraction rate to a greater extent than the process temperature. The growth of microwave power results in a more than the two-fold rise of the yield of extractives from a coffee slurry.Specification of the microwave oil extractor was defined. The extractor sample was tested at a specific power of 180...240 W/kg in the mode of boiling extractant. Ethanol (93...96 % concentration) was used as an extractant. As a result of the tests, a high-quality coffee oil was obtained. It is characterized by a pronounced aroma, coffee taste and an intense dark brown color.Flow diagram of pre-extraction of coffee from slurry was worked out. Additional extraction of water-soluble extractive substances from coffee slurry increased the extract yield by 10...12 %. The temperature regime of extraction was significantly reduced plus duration and energy intensity of the process were reduced.An innovative flow diagram has been developed for the production of liquid coffee concentrate as a basis for coffee-based drinks ready for immediate use. The concentration of solids is 50...65 %, На основе энергетического и экологического аудита проведен анализ материальных потоков, конверсии энергии, выбросов в атмосферу и литосферу при производстве растворимого кофе.Для повышения энергоэффективности, снижения экологической нагрузки разработаны инновационные технологические схемы и оборудование по переработке отходов и производству новых кофейных продуктов.Проведено экспериментальное моделирование: кинетики микроволнового экстрагирования водорастворимых веществ и масла из кофейного шлама; гидравлики течения экстрагента через кассеты микроволнового экстрактора. Экспериментальные данные обобщены в виде критериального уравнения.В результате экспериментального моделирования кинетики экстрагирования установлено, что продолжительность процесса в микроволновом поле приблизительно в 20 раз меньше, чем в термостате. Действие микроволнового поля влияет на скорость экстрагирования в большей мере, чем температура процесса. Повышение мощности микроволновой энергии повышает выход экстрактивных веществ из кофейного шлама более чем в два раза.Определены технические характеристики микроволнового экстрактора масла. Испытания образца экстрактора проводились при удельной мощности 180…240 Вт/кг в режиме кипения экстрагента. В качестве экстрагента использовался этанол (концентрация 93…96 %). В результате испытаний получено качественное кофейное масло, которое характеризуется выраженным ароматом и вкусом кофе и интенсивной темно-коричневой окраской.Разработана технологическая схема предэкстрагирования кофе из шлама. Дополнительное извлечение из шлама кофе водорастворимых экстрактивных веществ, повышает выход экстракта на 10…12 %. Существенно снижен температурный режим экстрагирования, уменьшена продолжительность и энергоемкость процесса.Разработана инновационная технологическая схема производства жидкого концентрата кофе – основы для напитков на базе кофе, готовых к немедленному употреблению. Концентрация сухих веществ составляет 50…65 %, На основі енергетичного й екологічного аудиту проведено аналіз матеріальних потоків, конверсії енергії, викидів в атмосферу й літосферу при виробництві розчинної кави.Для підвищення енергоефективності, зниження екологічного навантаження розроблені інноваційні технологічні схеми й устаткування по переробці відходів і виробництву нових кавових продуктів.Проведено експериментальне моделювання: кінетики мікрохвильового екстрагування водорозчинних речовин і масла з кавового шламу; гідравліки плину экстрагента через касети мікрохвильового екстрактора. Експериментальні дані узагальнені у вигляді критериального рівняння.У результаті експериментального моделювання кінетики екстрагування встановлено, що тривалість процесу в мікрохвильовому полі приблизно в 20 разів менше, ніж у термостаті. Дія мікрохвильового поля впливає на швидкість екстрагування більшою мірою, чим температура процесу. Підвищення потужності мікрохвильової енергії підвищує вихід екстрактивних речовин з кавового шламу більш ніж у два рази.Визначено технічні характеристики мікрохвильового екстрактора масла. Випробування зразка екстрактора проводилися при питомій потужності 180…240 Вт/кг у режимі кипіння екстрагенту. У якості екстрагенту використовувався етанол (концентрація 93...96 %). У результаті випробувань отримане якісне кавове масло, що характеризується вираженим ароматом і смаком кави й інтенсивним темно-коричневим фарбуванням.Розроблено технологічну схему передекстрагування кави зі шламу. Додатковий витяг зі шламу кави водорозчинних екстрактивних речовин, підвищує вихід екстракту на 10...12 %. Істотно знижено температурний режим екстрагування, зменшені тривалість і енергоємність процесу.Розроблено інноваційну технологічну схему виробництва рідкого концентрату кави – основи для напоїв на базі кави, готових до безпосереднього вживання. Концентрація сухих речовин становить 50...65 %

Interfacial solar steam generation is a highly efficient and sustainable technology for clean water production and wastewater treatment. Although great progress has been achieved in improving evaporation rate and energy efficiency, it's still challenging to fully eliminate the energy loss to the surrounding environment during solar steam generation. To achieve this, a novel heatsink‐like evaporator (HSE) is developed herein. During solar evaporation, the temperature on the top solar evaporation surface can be regulated by the fin structures of the HSE. For the evaporators with 5 to 7 heatsink fins, the temperature of the solar evaporation surface is decreased to be lower than the ambient temperature, which fully eliminates the radiation, convection, and conduction heat losses, leading to the absolute cold evaporation over the entire evaporator under 1.0 sun irradiation. As a result, massive energy (4.26 W), which is over 170% of the received light energy, is harvested from the environment due to the temperature deficit, significantly enhancing the energy efficiency of solar steam generation. An extremely high evaporation rate of 4.10 kg m−2 h−1 is realized with a 6‐fin photothermal HSE, corresponding to an energy conversion efficiency far beyond the theoretical limit, assuming 100% light‐to‐vapor energy conversion., A heat‐sink like photothermal evaporator is designed and fabricated to realize fully cold solar evaporation under one sun irradiation with zero energy loss and massive energy gain (equivalent to 170% of the incident light energy) from the environment. An extremely high evaporation rate of 4.10 kg m−2 h−1 with corresponding energy efficiency far beyond the theoretical limit is achieved.

Energy cost contributes to the second largest portion of the starch-processing plants’ expenditure. Therefore, to improve energy efficiencies, CHP systems installed in cassava starch plants are considered. Hence, their energy conversions and efficiencies are investigated. Where, the structure of the plant is modeled, the factors of biogas, power, heat and the biogas distribution ratio are focused; the relationships among those factors are resolved by establishing formulas based on theoretical analysis. Results show: the minimum demand of biogas for 1 t starch product is 134.8 m3, which can produce 704.7–875.6 MJ of electric energy and total 1311.0 MJ of heat for starch production by a CHP-boiler system. The steam produced there can fully satisfy the heat demand under the three strategies, while a minority of excess electricity is available under the strategy 3. The total energy efficiencies of the CHP-boiler system are 70.6%, 70.1% and 67.1% corresponding to the three strategies; those are 8.4%–11.9% more than the efficiency of 58.7% by the original system. The total reduction of CO2 emissions is 2017.1–2508.3t/a for a 200 t/d cassava starch plant using CHP-boiler system; which investment costs 27.24 million CNY in total, and will be pay back in 3.18 years.

Rape straw, as a typical residue from agriculture, was recycled to produce bio-oil via vacuum pyrolysis. The energy conversion rate (ECR) of biomass pyrolysis was proposed to take into acco...

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.

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.

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.

A multi-functional electrochromic material which modulates light over a wide spectral range and stores electrical energy is an intriguing substance, which would lead to a variety of novel applications, such as smart windows for energy-efficient buildings, solar power storage, nonemissive displays, electronic paper, optoelectronic switches, and variable-reflectance mirrors/surfaces. Developing such a versatile material entails merging the electrochromic phenomenon with electrical-chemical energy conversions in an electrochromic-battery platform. However, the challenges related to transition metal oxide electrochromic-batteries include poor energy storage, low optical contrast, and high fabrication cost. Here, we demonstrate the synthesis of aqueous nanocrystalline colloidal molybdenum oxide in a matrix of tungsten molybdenum oxide (MoO3-W0.71Mo0.29O3) for solution-processed fully reversible switching electrochromic-battery electrodes. The hybrid material exhibits both 50% optical contrast modulation over a wide optical bandwidth and an improved Columbic efficiency. An 8 × 8 cm2 energy storing smart (ESS) window is assembled to demonstrate a functional prototype that can power an LED for more than 10 min when charged under −2.5 V for 1 min. The enhanced electrochromic performance, high energy storage capacity, simple solution processability, versatility for large area fabrication, and low cost make this nanocrystalline MoO3-W.71Mo.29O3 composite a promising material with the potential to be deployed ubiquitously in energy-efficient smart window architectures.

Activated carbon obtained from biomass wastes was presently studied in order to evaluate its applicability in an energy storage device. Biochar was obtained by the carbonization of spent malt rootlets and was further processed by mild treatment in NaOH. The final product had a specific surface of 362 m2 g−1 and carried Na, P and a few mineral sites. This material was first characterized by several techniques. Then it was used to make a supercapacitor electrode, which reached a specific capacitance of 156 F g−1. The supercapacitor electrode was combined with a photocatalytic fuel cell, making a simple three-electrode device functioning with a single alkaline electrolyte. This device allows solar energy conversion and storage at the same time, promoting the use of biomass wastes for energy applications.

The sunlight-heating and electricity-heating interfacial evaporation membrane (SHEHIEM), which is prepared mainly using wood pulp and MWCNTs and is directly driven by sunlight and electricity from photovoltaic panels, is adopt to produce more steam at a very low cost. The results show that some SHEHIEMs of different compositions, having higher steam yield in sunlight heating, can hardly run in electricity heating and the season is that the resistance of SHEHIEM changes sharply during absorbing water. Thus, according to resistance, hydrophilicity, steam yield, SEM, XRD, FTIR, TG, absorption spectra and tensile strength, the composition of SHEHIEM is determined and optimized. When the SHEHIEM is operated in only electricity heating, only sunlight heating, sunlight and electricity heating (S&E heating), the steam yield of S&E heating is the highest and 1.30 kg/m2 for 0.5 KW, 1.90 kg/m2 for 1 KW, 2.37 kg/m2 for 1.5 KW, 2.86 kg/m2 for 2 KW and 3.23 kg/m2 for 2.5 KW, respectively. Meantime, its energy conversion efficiencies are also the highest and 62.7% for 0.5 KW, 68.4% for 1 KW, 68.8% for 1.5 KW, 69.3% for 2 KW and 67.2% for 2.5 KW, respectively, and the SHEHIEM shows synergistic effects. For S&E heating of 1 kW/m2 and 2 kW/m2, 10 h consecutive tests show that the SHEHIEM has better stability. After evaporation, all the detected indicators meet the drinking water standard of WHO. In the open, when the SHEHIEM is run for 7 h in winter, the production water mass and energy conversion efficiencies are 9.03 kg/m2 and 55.4% for 1 KW and 15.67 kg/m2 and 61.0%.

Neutral aqueous electrolytes have been shown to extend both the calendar life and cycling stability of secondary zinc–air batteries (ZABs). Despite this promise, there are currently no modeling studies investigating the performance of neutral ZABs. Traditional continuum models are numerically insufficient to simulate the dynamic behavior of these complex systems because of the rapid, orders‐of‐magnitude concentration shifts that occur. In this work, we present a novel framework for modeling the cell‐level performance of pH‐buffered aqueous electrolytes. We apply our model to conduct the first continuum‐scale simulation of secondary ZABs using aqueous ZnCl2–NH4Cl as electrolyte. We first use our model to interpret the results of two recent experimental studies of neutral ZABs, showing that the stability of the pH value is a significant factor in cell performance. We then optimize the composition of the electrolyte and the design of the cell considering factors including pH stability, final discharge product, and overall energy density. Our simulations predict that the effectiveness of the pH buffer is limited by slow mass transport and that chlorine‐containing solids may precipitate in addition to ZnO.

Pyrolysis is one of the potential routes to harmless energy and useful chemicals from biomass. The pyrolysis of Albizia amara was studied for determining the main characteristics and quantities of ...

This chapter provides updated information and current state of the knowledge on bioreactors used for wastewater to energy conversion. Continuous stirred tank reactor (CSTR), anaerobic filter (AnF), up-flow anaerobic sludge blanket (UASB), and anaerobic membrane bioreactor (AnMBR) treating industrial wastewaters were reviewed. Among the focused reactors, the AnMBR offered many advantages (e.g., low HRT, high OLR), achieving high performances in terms of COD removal and biomethane yield (i.e., 99% and 0.55 m3 CH4 kg−1 CODremoved, respectively). However, an energy evaluation has suggested a higher energy recovery of UASB technology (i.e., 3.29 kWh kg−1 CODremoved) than those showed by CSTR, AnF, and AnMBR (i.e., 0.35, 2.21, and 2.40 kWh kg–1 CODremoved, respectively). The scale-up assessment has also revealed similar results between pilot and full-scale experience in Europe.

doi: 10.1080/07373937.2018.1492615 Drying woody biomass holds the potential to improve the energy efficiency of certain processes, such as in CHP plants. Drying can also be a necessary unit process in several energy conversion processes (e.g. in biomass gasification). Belt dryers are typically used for drying when low temperature air (100–110 °C) is used. This article aims to produce new knowledge about the influence of the main design parameters on the drying costs of a low temperature belt dryer when three different materials (forest residue, bark, as well as sawdust and soot sludge mixture) are dried using it. The influence is analyzed by changing the following parameters: bed height, air temperature, air velocity and initial/final moisture contents of the material. The study aims to evaluate which of these parameters has an actual effect on drying costs. Results indicate that the lowest costs are achieved with the highest air temperature if the heat price is the same for every air temperature level. However, an optimal bed height depends on the material. Increasing the air velocity does not necessarily decrease the costs. In the sensitivity analysis, to factor in the influence of the temperature on the heat price, the price was changed for every drying air temperature (1, 5, 10 and 15 €/MWh). This analysis showed that the lowest drying costs are achieved by the lowest air temperature in all cases, thus indicating that the price of the heat has a remarkable influence on the economics of drying. Furthermore, the results support the use of low temperature heat sources in drying if they are clearly less expensive than higher temperature heat sources. However, if the prices for lower and higher air temperatures are of the same magnitude, the higher air temperatures are preferable. In general, this paper shows that it is important to pay attention to the main design parameters to optimize total drying costs. For example, if an overly low bed height is used in woodchips or bark drying, the total drying costs might be dozens of per cent higher than inthe most economic case.

Plant microbial fuel cell (P-MFC) is an electrochemical reactor that converts organic compounds to electrical energy through the catalytic reaction from electrochemically active bacteria (EAB). However, there is no sign of an attempt in developing the functional model in predicting the energy conversion and utilization of P-MFC. In this study, an analytic model is proposed to show the whole production process of the organic compound to electrical energy generation. Pandanus Amaryllifolius plant was used as sources of photosynthate, where biomass product from rhizodeposition, acetate was produced, and soil bacteria as the microbial culture, and air as the input to the cathode chamber. The proposed analytical model is able to predict the output of the P-MFC using the parameters from the experiment. The generated data from the model was then compared with the monitored data from the Pandanus Amaryllifolius P-MFC. The results show the electrical power output has a high similarity pattern with the bacterial growth curve model and able to achieve the coulombic efficiency of 95.32%.

The improvement of the design and operation of energy conversion systems is a theme of global concern. As an energy intensive operation, industrial agricultural product drying has also attracted significant attention in recent years. Taking a novel industrial corn drying system with drying capacity of 5.5 t/h as a study case, based on existing exergoeconomic and exergetic analysis methodology, the present work investigated the exergetic and economic performance of the drying system and identified its energy use deficiencies. The results showed that the average drying rate for corn drying in the system is 1.98 gwater/gdry matter h. The average exergy rate for dehydrating the moisture from the corn kernel is 345.22 kW and the exergy efficiency of the drying chamber ranges from 14.81% to 40.10%. The average cost of producing 1 GJ exergy for removing water from wet corn kernels is USD 25.971, while the average cost of removing 1 kg water is USD 0.159. These results might help to further understand the drying process from the exergoeconomic perspective and aid formulation of a scientific index for agricultural product industrial drying. Additionally, the results also indicated that, from an energy perspective, the combustion chamber should be firstly optimized, while the drying chamber should be given priority from the exergoeconomics perspective. The main results would be helpful for further optimizing the drying process from both energetic and economic perspectives and provide new thinking about agricultural product industrial drying from the perspective of exergoeconomics.

Biomass conversion into various forms of energy, such as heat, power, or biofuels using thermal processes, involves the decomposition of biomass by exposure to heat, typically above 300 °C. Thermal conversion processes include pyrolysis, gasification, and direct combustion. Several factors affect the yields and energy recovery from these processes including temperature, reaction time, heating rate, absence, or presence of oxygen, use of catalysts, and pressure. Due to rice straw’s relatively high carbon and hydrogen contents, it contains a considerable amount of energy that make it a suitable feedstock for thermal conversion. In this chapter, the basic principles and factors affecting the thermal conversion of biomass into energy are discussed. Studies on the use of rice straw as feedstock to produce heat, power, and biofuels via thermal conversion are reviewed. Utilization of thermal conversion byproducts including biochar and ash will are presented. Thermal processes are compared in terms of energy conversion, possible environmental impacts, and technological and commercial maturity.

Currently, energy conversion methods in nanochannels have been developed for both fundamental sciences and technological applications. Graphene oxide membranes with excellent properties possess potential applications in numerous fields. Due to the confinement of nanocapillaries within graphene oxide membranes and the mobility difference of ions, an electricity generation process has been achieved using graphene oxide membranes. In this study, for the first time, the influence of source concentration, applied pressure and membrane thickness was investigated on electricity generation in aqueous environment. The results revealed that these three factors could successfully control the electricity generation with graphene oxide membranes. Electrical potential difference would become larger with increasing the source concentration and membrane thickness. In contrast, the applied pressure was not well-suited to capture energy from sources. This provided new insights into the design and utilization of graphene oxide films for highly efficient energy harvesting.

The chemical looping gasification (CLG) between biomass and Fe2O3 be expressed as a potential hydrogen production technology as long as Fe2O3 could be effectively alkali-modified and enough steam could be supplied to the biomass gasification process. Therefore, a one-step strategy was developed herein by introduces KNO3-containing acetic acid liquid waste to modify Fe2O3 and provide enough steam to improve the efficiency of hydrogen production from corn stalk. Experiments under different excess oxygen ratio (Ω), temperature (T) and potassium concentrations (mKNO3) shows that these parameters have obvious effects on biomass CLG, and the highest hydrogen yield of 1.79 L is obtained at Ω = 0.2, T = 750 °C and mKNO3 = 8%. The kinetic and thermodynamic analysis further verifies that KNO3-containing acetic acid liquid waste boosts biomass CLG for hydrogen generation. The proposed CLG strategy has dual advantages of waste treatment and energy conversion.

Molecular solar‐thermal energy storage systems are based on molecular switches that reversibly convert solar energy into chemical energy. Herein, we report the synthesis, characterization, and computational evaluation of a series of low molecular weight (193–260 g mol−1) norbornadiene–quadricyclane systems. The molecules feature cyano acceptor and ethynyl‐substituted aromatic donor groups, leading to a good match with solar irradiation, quantitative photo‐thermal conversion between the norbornadiene and quadricyclane, as well as high energy storage densities (396–629 kJ kg−1). The spectroscopic properties and energy storage capability have been further evaluated through density functional theory calculations, which indicate that the ethynyl moiety plays a critical role in obtaining the high oscillator strengths seen for these molecules.

Biomass is seen as a viable alternative energy source for replacing fossil fuel. However, the inherent properties of raw biomass, including high moisture content, low energy density, hydrophilic behavior, and fibrous nature, limit its use. Thus, pretreatment becomes an important step in the path of biomass to energy conversion routes. Torrefaction is one such emerging pretreatment process, which makes biomass hydrophobic, more energy dense, and easier to grind. This paper investigates the torrefaction process in a continuous two-stage, indirectly heated rotary torrefier under the volatile gases medium. The rotary reactor is operated at different angular speeds, inclinations, and temperatures, and the produced torrefied solid product is characterized for physical and chemical compositions. The observed characteristics of the torrefied biomass produced under the volatile gases medium indicate that nitrogen supply can be avoided. Experimental results showed that torrefaction temperature has a more significan...

The low-cost biocathode microbial electrochemical system (MES) with microbial separator (MS) is promising for the practical application in wastewater treatment. To evaluate the potential realizable advantages for future full-size MESs, four 2-Liters MES modules with MS are constructed and their energy conversion, biomass metabolism and pollution degradation are systematically investigated. The mass and energy flow for MES with raw domestic wastewater is built under maximum power point (Pmax), maximum current point (Imax), and open circuit (OC) modes. The chemical oxygen demand (COD) removal rates are 0.831 and 0.846 kg m−3 day−1 in Pmax and Imax modes, while that of OC is 0.609 kg m−3 day−1. The effluent COD concentrations at Pmax and Imax are stable at 41 ± 2 and 37 ± 2 mg L−1, while that of OC is up to 101 ± 4 mg L−1. The observed sludge yield is only 23.4% (Pmax) or 19.5% (Imax) of the OC mode with much higher sludge calorific values. For the raw wastewater treatment, the direct electricity harvest and reuse from MES units are unrealistic and uneconomical due to its low energy efficiency. But the high COD removal efficiency and low observed sludge yield are the realizable advantages for practical applicated MESs.

Manipulating basal plane structure of graphene for advanced energy conversion materials design has been research frontier in recent years. By extending size of defects in the basal plane of graphene from atomic scale to nanoscale, graphene with in-plane holes can be synthesized by multiple steps oxidation and reduction of defective graphene oxide at low concentration. These complicated and low yield synthetic methods largely limited research and applications of holey graphene based high performance energy conversion materials. Inspired by graphene in-plane holes formation mechanism, an easy and scalable synthetic approach has been proposed in this work. By oxidizing widely available defective graphite mineral under high concentration, holey graphene oxide has been scalable synthesized. Through simple reduction of holey graphene oxide, nitrogen doped holey graphene with high volumetric capacitance of 439 F/cm 3 was obtained. We believe this breakthrough can provide a feasible synthetic approach for further exploring the properties and performance of holey graphene based materials in variety of fields.