Pool fires – An empirical correlation

This study presents the experimental procedure and results of highly controlled pool fire tests, in a quiescent environment, designed to accurately measure the fuel burning rate and, consequently for sufficiently large pools, the thermal radiation flux back to the fuel surface. Steps were taken to minimize the effects of in-depth absorption of flame radiation, circulation within the liquid, and changes in fuel composition due to distillation of more volatile fuel components. With these precautions, focus is placed on gas phase phenomena controlling the heat release rate per unit pool area. The primary variables considered are: pool diameter, heat of gasification, flame sootiness as characterized by the inverse of the fuel smoke-point flame height, and, to a lesser extent, absorption of flame radiation by the fuel vapors just above the liquid surface. Results reported herein agree well with literature values for experiments conducted under similarly controlled conditions. A simple empirical formula is developed based primarily on heat of gasification and smoke point and is shown to correlate the mass burning rate within 9%, on average, of the experimental data.     

Evaporator modeling – A hybrid approach

In this paper, a hybrid modeling approach is proposed to model two-phase flow evaporators. The main procedures for hybrid modeling includes: (1) Based on the energy and material balance, and thermodynamic principles to formulate the process fundamental governing equations; (2) Select input/output (I/O) variables responsible to the system performance which can be measured and controlled; (3) Represent those variables existing in the original equations but are not measurable as simple functions of selected I/Os or constants; (4) Obtaining a single equation which can correlate system inputs and outputs; and (5) Identify unknown parameters by linear or nonlinear least-squares methods. The method takes advantages of both physical and empirical modeling approaches and can accurately predict performance in wide operating range and in real-time, which can significantly reduce the computational burden and increase the prediction accuracy. The model is verified with the experimental data taken from a testing system. The testing results show that the proposed model can predict accurately the performance of the real-time operating evaporator with the maximum error of ±8%. The developed models will have wide applications in operational optimization, performance assessment, fault detection and diagnosis.     

Nanomaterials for photoelectrochemical water splitting – review

Photoelectrochemical (PEC) water splitting using nanomaterials is one of the promising techniques to generate hydrogen in an easier, cheaper and sustainable way. By modifying a photocatalyst with a suitable band width material can improve the overall solar-to-hydrogen (STH) energy conversion efficiency. Nanomaterials can tune their band width by controlling its size and morphology. In many studies, the importance of nanostructured materials, their morphological and crystalline effects in water splitting is highlighted. Charge separation and transportation is the major concern in PEC water splitting. Nanomaterials are having high surface to volume ratio which facilitates charge separation and suppress electron-hole pair recombination. This review focuses on the recent developments in water splitting techniques using PEC based nanomaterials as well as different strategies to improve hydrogen evolution.     

Feasibility of photovoltaic – Thermoelectric hybrid modules

Outdoor performance of photovoltaic (PV) modules suffers from elevated temperatures. Conversion efficiency losses of up to about 25% can result, depending on the type of integration of the modules in the roof. Cooling of modules would therefore enhance annual PV performance. Instead of module cooling we propose to use the thermal waste by attaching thermoelectric (TE) converters to the back of PV modules, to form a PV–TE hybrid module. Due to the temperature difference over the TE converter additional electricity can be generated. Employing present day thermoelectric materials with typical figure of merits (Z) of 0.004 K⁻¹ at 300 K may lead to efficiency enhancements of up to 23% for roof integrated PV–TE modules, as is calculated by means of an idealized model. The annual energy yield would increase by 14.7–11%, for two annual irradiance and temperature profiles studied, i.e., for Malaga, Spain, and Utrecht, the Netherlands, respectively. As new TE materials are being developed, efficiency enhancements of up to 50% and annual energy yield increases of up to 24.9% may be achievable. The developed idealized model, however, is judged to overestimate the results by about 10% for practical PV–TE hybrids.     

Regulatory failures for nuclear safety – the bad example of Japan – implication for the rest of world

Investigation before and after the Fukushima nuclear accident has revealed that the failures of Japan's nuclear regulatory system was also blame to the worst nuclear accident since Chernobyl. The Fukushima nuclear accident has served to remind us that nuclear safety regulatory failure is vulnerable to the potentially deadly combination of natural risk. It should be noted that nuclear regulatory failures are not unique to Japan, given the low efficiency of the International Atomic Energy Agency (IAEA). We are living in a nuclear world. We have no alternative but to learn the lessons from the Fukushima. Unfortunately, all signs do not seem to be promising. This was partly due to competing proposals from several countries without clear understanding of which ideas would help, and a lack of sustained leadership focused on building support for key initiatives beforehand. New actions to strengthen the nuclear safety should be derived upon a thorough assessment of the causes for Japan's nuclear regulatory failures, as well as a comparative analysis of the nuclear regulatory systems in Japan, the United States (the owner of most nuclear reactors in operation), and China (the owner of most nuclear reactors under construction). This article is addressed to conduct an analysis of the causes for Japan's nuclear regulatory failure, discuss the key deficits in the nuclear regulatory systems of the U.S. and China, and finally outline two main policy recommendations. Nuclear accident knows no boundaries. Strengthening our nuclear safety regulation is not an option but an imperative, thus ensuring that the 433 operational units of reactor run safely, as well as 65 proposed ones. March 11, 2012 is the first anniversary of the Fukushima accident. This provocative article that calls for action on upgrade nuclear safety regulation over the world is dedicated to commemorate the first anniversary of the Fukushima accident.     

Biodiesel resources and production technologies – A review

The environmental concern and availability of fuels are greatly affecting the trends of fuels for transportation vehicles. Biodiesel is one of the options as alternative transport fuel. This can be produced from straight vegetable oils (SVOs), oils extracted from various plant species and animal fats. Amongst many resources, availability and cost economy are the major factors affecting the large scale production of the biodiesels. The transesterification is one of the production processes for biodiesel, but incomplete esterification of all fatty acids in the starting material, lengthy purification methods such as water washing, relatively long reaction times, contamination and separation difficulties associated with co-production of glycerol and saponification of the starting material under certain reaction conditions are still being major challenges in the biodiesel production. Technological advancement and enhanced production methods are the demand of present time for large scale and sustainable production of biodiesel. In the present paper, comprehensive review on its production process, feed stock and its applications have been made. From many case studies it was concluded that engine performance with B20 biodiesel blends, and mineral diesel were found comparable.     

Coal-fired oxy-fuel power unit – Process and system analysis

As oxy-fuel power generation is currently on the pre-demonstration stage of development many studies dealing with optimization and simulation aspects are still in progress. This paper is focused on the development of a simulation model of the integrated oxy-fuel system and cumulative energy analysis of an oxy-unit operation in separated national economy. The analyzed oxy-fuel system consists of a steam boiler, steam cycle, air separation unit, as well as a CO₂ purification and compression island. The built model is based on physical relations. It has been developed as a set of modules modelling isolated devices (e.g. combustion chamber or flue gas dehumidifier). Interconnections between these devices can be easily changed, which permits to analyse different oxy-fuel structures and operating parameters. The simulation model has been partially verified on the basis of literature data. Results of oxy fuel energy analysis have been presented for one selected structure and compared with an air combustion power unit, assuming the same steam cycle parameters. For both cases indices of cumulative primary energy consumption have been calculated. The obtained results show that the increase of oxy-fuel primary energy consumption (compared with air-based combustion) can be significantly reduced if by-produced nitrogen will be used for external applications.     

Vertically aligned carbon nanotube – Polyaniline nanocomposite supercapacitor electrodes

We develop a fast and cost effective method for the fabrication of a nanocomposite supercapacitor electrode. In this study aluminum foils were decorated with vertically aligned carbon nanotubes (VACNT) via chemical vapor deposition (CVD) method, which was followed by the electrodeposition of polyaniline (PANI) layer on top of the VACNTs. Electrochemical behavior of the fabricated nanocomposite electrodes were evaluated through cyclic voltammetry, galvanostatic charge discharge cycles and electrochemical impedance spectroscopy method. Fabricated VACNT/PANI nanocomposite electrodes through 15 electrodeposition cycles showed significant electrochemical performance. The specific capacity of these electrodes was calculated as 16.17 mF/cm² at a current density of 0.25 mA/cm².     

The Smart Grid – A saucerful of secrets?

To many, a lot of secrets are at the bottom of the often-cited catchphrase “Smart Grid”. This article gives an overview of the options that information and communication technology (ICT) offers for the restructuring and modernisation of the German power system, in particular with a view towards its development into a Smart Grid and thus tries to reveal these secrets. After a short outline on the development of ICT in terms of technology types and their availability, the further analysis highlights upcoming challenges in all parts of the power value chain and possible solutions for these challenges through the intensified usage of ICT applications. They are examined with regard to their effectiveness and efficiency in the fields of generation, transmission, distribution and supply. Finally, potential obstacles that may defer the introduction of ICT into the power system are shown. The analysis suggests that if certain hurdles are taken, the huge potential of ICT can create additional value in various fields of the whole power value chain. This ranges from increased energy efficiency and the more sophisticated integration of decentralised (renewable) energy plants to a higher security of supply and more efficient organisation of market processes. The results are true for the German power market but can in many areas also be transferred to other industrialised nations with liberalised power markets.     

Li-N-H system – Reversible accumulator and store of hydrogen

The statistical theory of phase transformations in the course of chemical reactions on hydrogen absorption–desorption in the lithium nitride with the formation of lithium amide and hydride has been developed. The calculation of free energies of all constituent phases of chemical reactions has been performed on the basis of molecular-kinetic notions, their dependences on temperature, pressure, hydrogen concentration and energetic parameters have been ascertained. The hydrogen solubility in phases has been estimated, it has been ascertained the possibility of manifestation of peculiarities of its temperature dependence. The constitution diagram for the system being investigated has been constructed. The actual conditions of manifestation of hysteresis effect has been justified. The calculation results have been compared with experimental literature data for the examined system.     

Solar assisted air conditioning of buildings – an overview

Goal of this contribution is to draw a picture about some general issues for using solar thermal energy for air conditioning of buildings. The following topics are covered:

• –A basic analysis of the thermodynamic limits for the use of heat cooling in combination with solar thermal energy is drawn; thereby fundamental insights about control needs for solar thermal driven cooling are obtained.
• –A short overview about the state-of-the-art of available technologies, such as closed thermal driven cooling cycles (e.g., absorption, adsorption) and open cooling cycles (e.g., desiccant employing either solid or liquid sorbents) is given and needs and perspectives for future developments are described.
• –The state-of-the-art of application of solar assisted air-conditioning in Europe is given and some example installations are presented.
• –An overview about new developments of open and closed heat driven cooling cycles for application in combination with solar thermal collectors is given and some of these new systems are outlined more in detail.

     

Hydrogen from biomass – Present scenario and future prospects

Hydrogen is considered in many countries to be an important alternative energy vector and a bridge to a sustainable energy future. Hydrogen is not an energy source. It is not primary energy existing freely in nature. Hydrogen is a secondary form of energy that has to be manufactured like electricity. It is an energy carrier. Hydrogen can be produced from a wide variety of primary energy sources and different production technologies. About half of all the hydrogen as currently produced is obtained from thermo catalytic and gasification processes using natural gas as a starting material, heavy oils and naphtha make up the next largest source, followed by coal. Currently, much research has been focused on sustainable and environmental friendly energy from biomass to replace conventional fossil fuels. Biomass can be considered as the best option and has the largest potential, which meets energy requirements and could insure fuel supply in the future. Biomass and biomass-derived fuels can be used to produce hydrogen sustainably. Biomass gasification offers the earliest and most economical route for the production of renewable hydrogen.     

Miniature heat-pipe thermal performance prediction tool – software development

The software for flat miniature heat-pipe parameters (Q_max, R_hp, temperature field along the pipe surface, heat transfer coefficients in the evaporator and condenser zones h_e, h_c, etc.) prediction and numerical modeling was developed. The experimental data received for the flat miniature heat pipe (2.5–4 mm thickness, 50–250 mm length, 8–11 mm width) with a copper sintered powder wick saturated with water were compared with the data of numerical analysis and results showed that experimental verification testifies the validity of the software application.     

Thermodynamic analysis of ethanol processors – PEM fuel cell systems

This work presents a simulative energy efficiency analysis performed on fuel processor – PEM fuel cell systems, considering ethanol as fuel and steam reforming or autothermal reforming as processes to produce hydrogen.     

Thermal – Catalytic cracking of real MSW into Bio-Crude Oil

The thermal decomposition method has been able to convert of real municipal solid waste (MSW) into Bio-Crude Oil (BCO) which is mainly contained hydrocarbon fuel such as light oil (gasoline) and heavy oil (diesel). By this method, sustainable MSW management and energy problem can be considered. Hence, this research was conducted the pyrolysis experimental to BCO production from the real MSW under thermal and catalytic pyrolysis at 400 °C and 60 min for time reaction. To increase the BCO yield in this study, the natural activated zeolite as a catalyst was employed. BCO was analyzed by Gas chromatography–mass spectrometry (GC–MS) which it can be used to identify carbon number range by percentage of peak areas. It was found that the catalytic pyrolysis has performances better than the thermal pyrolysis. Both of thermal and catalytic pyrolysis were the produce of BCO around 15.2 wt% and 21.4 wt% respectively with the main organic components are gasoline and diesel. Furthermore, paraffin and olefin fraction are major species in the gasoline and diesel. It can be concluded that the content of MSW and their processes has an impact on the fuel produced. In the thermal cracking produce BCO with higher content in the gasoline range. More plastic in MSW is also produce more gasoline while more biomass produces more in diesel range.     

Diopside – Mg orthosilicate and diopside – Ba disilicate glass–ceramics for sealing applications in SOFC: Sintering and chemical interactions studies

Diopside (CaMgSi₂O₆) based glasses compositions containing magnesium orthosilicate or barium aluminosilicates phases have been appraised for sealing applications in solid oxide fuel cells (SOFCs) and other solid-electrolyte devices. The sintering behavior and crystalline phase evolution of glass powders has been investigated under isothermal and non-isothermal conditions in the SOFC operating temperature range (800–900 °C). All the glass compositions exhibited two-stage shrinkage behavior resulting in well sintered and mechanically strong glass–ceramics with Augite as the primary crystalline phase. The appropriate coefficient of thermal expansion (CTE), long term thermal stability (300 h at 900 °C), high electrical resistivity, good adhesion and minimal reactivity with SOFC components makes the investigated glass–ceramics potential candidates for further experimentation as SOFC sealants.     

A methanol – Tolerant carbon supported Pt–Sn cathode catalysts

Carbon supported Pt–Sn bimetallic electrocatalysts with a Pt:Sn 90:10 atomic ratio were prepared by impregnation method and then heat treated at 300 and 500 °C under Helium atmosphere. The purpose of this work is to investigate the effect of tin addition to platinum for methanol tolerant oxygen reduction reaction. In this sense, structure and morphological properties of supported bimetallic catalysts were correlated to the catalytic performance. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterizations confirm the formation of Pt–Sn bimetallic electrocatalysts with a Pt single-phase material alloy and revealed an increase in the average particle size after heat treatment. The electrocatalytic activities of these samples for the oxygen reduction reaction (ORR) were examined in acidic medium using both a rotating disk (RDE) and a rotating ring disk (RRDE) electrodes. Compared with the Pt/C, Pt–Sn/C bimetallic catalysts show superior electrocatalytic activity towards ORR with an approaching four electron pathway leading to water formation. The specific and mass activity for ORR follow the order of Pt–Sn/C-500 ≈ Pt–Sn/C-300 > Pt–Sn/C > Pt/C. Furthermore, it is found that among the three Pt–Sn samples, Pt–Sn/C-500 exhibits the highest methanol tolerance. These experimental observations indicate that the addition of Sn into Pt is favorable to maximize the ORR performances of platinum and further the heat treatment is beneficial to improve the methanol tolerance behavior. On this basis, the novel Pt–Sn catalysts can be considered as potential candidates to be used as cathodes in Direct Methanol Fuel Cells.     

Land application of organic waste – Effects on the soil ecosystem

Growing populations and the increasing use of existing resources has led to growth in organic waste emissions. Therefore, a sustainable approach to managing this waste has become a major concern in densely populated areas. Biological treatment is an efficient method for reducing the amount of organic waste, and for producing energy. A large number of biogas plants and compost facilities that use organic waste as a substrate for electricity and fuel production are being built around the world. The biological treatment process in these plants produces large amounts of organic waste, and there is therefore a growing need to find a sustainable use for this material. Organic waste, such as biogas residues and compost can be a valuable fertilizer for agricultural soils. They can serve as a source of plant nutrients and can also improve soil structure and water holding capacity. However, as organic residues are known to contain both heavy metals and organic contaminants there is a need for long term field experiments to ensure that soil and plant quality is maintained. In order to investigate the potential risks and benefits of using organic waste in agriculture, an 8 year field experiment was established in central Sweden. Under realistic conditions, compost and biogas residues from source-separated household waste were compared with traditional mineral fertilizer. We examined crop yield and soil chemical and microbiological properties. The main conclusion from the field experiment was that biogas residues resulted in crop yields almost as high as the mineral fertilizer NPS. In addition, several important soil microbiological properties, such as substrate induced respiration, potential ammonium oxidation and nitrogen mineralization were improved after application of both biogas residues and compost. Moreover, no negative effects could be detected from using either of the organic wastes. In particular the genetic structure of the soil bacterial community appeared to resist changes caused by addition of organic waste.     

Flow characteristics of refrigerants flowing through capillary tubes – A review

A comprehensive review of the literature on the flow of various refrigerants through the capillary tubes of different geometries viz. straight and coiled and flow configurations viz. adiabatic and diabatic, has been discussed in this paper. The paper presents in chronological order the experimental and numerical investigations systematically under different categories. Flow aspects like effect of coiling and effect of oil in the refrigerants on the mass flow rate through the capillary tube have been discussed. Furthermore, the phenomenon of metastability and the correlations to predict the underpressure of vaporization have also been discussed. The paper provides key information about the range of input parameters viz. tube diameter, tube length, surface roughness, coil pitch and coil diameter, inlet subcooling and condensing pressure or temperature. Other information includes type of refrigerants used, correlations proposed and methodology adopted in the analysis of flow through the capillary tubes of different geometries operating under adiabatic and diabatic flow conditions. It has been found from the review of the literature that there is a lot more to investigate for the flow of various refrigerants through different capillary tube geometries.