Energy Conversion and Management

Experimental studies on closed cycle MHD power generation with “Fuji-1” blow-down facility at the Tokyo Institute of Technology are presented. Recently, a new disk generator (Disk-F4) has been installed and a new seed injection system has been introduced from IVTAN (Institute of High Temperature in Russia). The design concept of the new generator channel is focused mainly on the reliability of high power generation. The Mach number at the generator inlet and the thermal input are increased up to ~2.8 and ~3.0 MW, respectively. In the new seeding system, a melted seed material is pushed by a piston dozator, instead of being gas-pressure-driven as in the previous system. The controllability of seed fraction is markedly improved, and the large fluctuation as has been observed previously is diminished. In power generation experiments with these new components, a maximum power output of 502 kW and an enthalpy extraction ratio of 16.7% have been obtained. These values at the present stage are lower than the maximum values previously achieved in the facility. However, reliable high power generation can be expected with the new generator. The behavior of plasma and fluid under high MHD interaction taking place in the generator channel is also discussed

The sequestration of CO₂ in the deep ocean has been proposed as a way to mitigate potential climate change. In order to better understand the environmental impacts associated with such a strategy, a methodology has been developed to quantify mortality suffered by marine zooplankton passing through a CO₂-enriched sea water plume. Predicted impact depends on the mode of injection, with scenarios which disperse the CO₂ showing the least impact. Benthic impacts also depend on the injection mode, with localized effects expected for any scenario in which the plume contacts the bottom. Based on available data, our modeling suggests that mortality associated with exposure to low pH can be avoided by properly dispersing the CO₂ and keeping the plume off of the seabed

A new class of single-switch low harmonic boost-type rectifiers suitable for both single and three phase applications are introduced in this paper. All the semiconductors in these rectifiers operates with zero-voltage switching and clamped voltage (ZVS-CV) with minimum voltage stress while the DC-side diode turns-off at zero-current. Hence, the switch turn-on loss and noise are sufficiently reduced. A multi-resonant scheme is used to achieve this property. Line current waveforms of low harmonic content are obtained naturally by these rectifiers. Simulation and experimental results for a boost-type rectifier are presented

The National Ignition Facility (NIF) is a 192-beam Nd:glass laser facility being constructed at the Lawrence Livermore National Laboratory (LLNL) to conduct research in inertial confinement fusion (ICF) and high energy density (HED) science. When completed, NIF will produce 1.8 MJ, 500 TW of ultraviolet light, making it the world’s largest and highest-energy laser system. The NIF is poised to become the world’s preeminent facility for conducting ICF and fusion energy research and for studying matter at extreme densities and temperatures.

This is a concise review of possibilities and prospects for power generation in space for terrestrial use. Advantages of this approach to power production, the economic and technological obstacles to be overcome, various conceptual approaches, including solar photovoltaic, solar dynamic, nuclear, and the use of chemical energy, and recommendations for progress are summarized. In view of the rising demand for energy, and of the diminishing fuel and available terrestrial area, the use of space for power generation seems to be inevitable: (1) It allows highest energy conversion efficiency, provides the best heat sink, makes best use of solar energy, and relieves the Earth from the penalties of power generation. (2) Both the costs of launching payloads into space and those of energy transmission are declining. The major obstacle is the exorbitantly high cost, which under current conditions requires, for example, the reduction of space transportation costs about a hundredfold for competitiveness. Other issues also need to be resolved, some of general nature, such as environmental effects and security and legal aspects, and some system specific, such as safety of nuclear power plants, and the realization of higher energy conversion and transmission efficiencies. Generation of power in space for terrestrial use will require massive resources, strong international cooperation, and several decades. A staged approach, fortified by developing applications collateral with space power, such as space-to-space power beaming for powering satellites, power relaying by orbital microwave or laser beam reflectors, and orbital mirrors for extended periods of terrestrial illumination, is recommended.

Black thin films deposited on metallic substrates are selective in nature and are promising for photothermal conversion of solar energy. In this paper, we have discussed the methods of deposition of three such coatings (i) magnesium sulphide, (ii) zinc oxide and (iii) Ni black on A1 substrates. From the experimentally observed spectra, the figures-of-merit, i.e. a/e ratios, are calculated and found to be 6.4, 5.0 and 10.0, respectively.

The performances of grooved emitter (GE), grooved collector (GC) and grooved electrodes (GEL) thermionic converters are investigated, and the results are compared with those of an identical converter with smooth electrodes (SEL), which is tested at the same conditions. These converters, with planar polycrystalline molybdenum electrodes and a 0.5 mm inter-electrode gap, are tested at emitter temperatures, TE=1473–1673 K, collector temperatures, TC=773–1023 K and Cs pressures, PCs=10–500 Pa. The grooved electrodes have concentric macro-grooves 0.5 mm wide, 0.5 mm deep and 1.0 mm apart. Measured and calculated performance parameters include ignition voltage, VIG, barrier index, VB, electric power density, PD, and conversion efficiency, η, as functions of the cesium pressure and electrodes temperatures. VIG of the GC converter is smaller than that of the SEL converter by up to ∼0.9 V for PCs=20–100 Pa. VB for the SEL converter is always lowest, except at TE=1673 K and TC=1023 K, indicating that grooved electrode(s) are effective in reducing VB only at high electrodes temperatures. The GE converter has the lowest PD and η, followed by the GEL converter, GC converter and, finally, the SEL converter, except for TE=1473 K and TC=773 K and for TE=1673 K and TC=1023 K. PD and η for the SEL converter at the optimum TC (873 K) are 3.74 We/cm2 and 17.0%, respectively, and they decrease to 1.61 We/cm2 and 10.4%, respectively, as TC increases by 150 to 1023 K. The corresponding PD and η for the GC converter decrease from 2.56 We/cm2 and 14.7% at TC=873 K to 2.38 We/cm2 and 14.3%, respectively, at TC=1023 K. Those for the GE converter decrease from 2.18 We/cm2 and 12.9% at TC=873 K to 1.56 We/cm2 and 11.0%, respectively, at TC=1023 K. For the GEL converter, PD and η decrease from 1.86 We/cm2 and 11.2% at TC=873 K to 1.44 We/cm2 and 9.7%, respectively, at TC=1023 K. At TE=1673 K and TC=1023 K, the converter with a GC has the lowest VB and operates at the highest PD (2.38 We/cm2) and η (14.3%).

The results of performance analyses of a refractory Nb–1Zr/C-103 vapor anode multi-tube alkali-metal thermal-to-electric conversion (AMTEC) cell are presented and discussed. This cell could be used with a radioisotope heater unit to provide electric power from tens to a few hundreds of watts. In the tens of kilowatts electric range, the AMTEC cells could be used with a parabolic solar concentrator or a nuclear reactor heat source. The present cell measures 41.27 mm in diameter and is 125.3 mm high and has eight sodium beta′′-alumina solid electrolyte (BASE) tubes, which are connected electrically in series to provide a load voltage in excess of 3 V. The hot structure of the cell, including the hot plate, the BASE tube support plate, the hot plenum wall and conduction stud, the evaporator standoff and porous wick and the side wall facing the BASE tubes, is made of Nb–1Zr. The cell's colder structure, which includes the condenser structure, the interior thermal radiation shield, the casing and wick of the liquid sodium return artery and the side wall above the BASE tubes, is made of C-103. This niobium alloy is stronger and has a lower thermal conductivity than Nb–1Zr, reducing the parasitic heat conduction losses in the cell wall, hence enhancing the cell's performance. The base cell weighs 163.4 g and delivers 7 We at 17% conversion efficiency and load voltage of 3.3 V (cell specific mass of 23.4 g/We). These performance parameters were for TiN BASE electrodes characterized by B=75 A K1/2/m2 Pa and G=50, assuming a BASE/electrode contact resistance of 0.06 Ω cm2 and a BASE braze structure leakage resistance of 3 Ω. Also, the inner surfaces of the thermal radiation shield and the cell wall above the BASE tubes were covered with low emissivity rhodium. The temperatures of the BASE brazes and the evaporator were below the recommended design limits (1123 and 1023 K, respectively), and the temperature margin was ⩾+20 K to avoid sodium condensation inside the BASE tube, shorting the cell. When high performance electrodes, characterized by B=120 A K1/2/m2 Pa and G=10, were used, the cell's electric power increased to 8.38 We at 3.5 V, and the efficiency increased to 18.8%, decreasing the specific mass of the cell to 19.7 g/We without exceeding any of the design temperature limits.

In this paper an experience, environmental assessment, a model for exit gas composition, agglomeration problem and a model for solid population balance of 10 MW power plant at Jalkheri, Distt. Fatehgarh Sahib, Punjab, India based on rice husk has been discussed. Three phase multistage mathematical model for exit gas composition of rice husk in fluidized bed has been derived. The model is based on three-phase theory of fluidization and material balance for shrinking rice husk particles and it is similar to model developed by Kunii and Levenspiel. The burning of rice husk is assumed to take place according to single film theory. The model has been used to predict the exit gas composition particularly O2, CO2 and N2. The agglomeration problem of above plant which is main reason for defluidization of bed has also been discussed. SEM of ash agglomerates has been done. Ash samples taken from the above 10 MW power plant at Jalkheri has been quantitatively analyzed. Finally solid population model has been formed to calculate bed carbon load and carbon utilization efficiency. Above two models are experimentally correlated with the data collected from the above 10 MW power plant at Jalkheri, Distt. Fatehgarh Sahib, Punjab, India which uses rice husk as a fuel input (at the time of study). All the results from the model for rice husk are coming with in permissible limits.

This study investigates the performance of a heat pump assisted mechanical opener drying system. This system was constructed and tested at the Energy Laboratory, Mechanical Engineering Department, Balikesir University, Turkey. Wetted wool, which is a material with fibres, was used as the test material being dried. The air velocities at the inlet of the dryer were varied from 0.65 to 1.25 m/s, while the material loading ratios (material/dryer volume) ranged from 1.39 to 2.78, with an optimal value of 1.85. The bypass air ratio, defined as the air mass flow rate bypassing the evaporator divided by the total air mass flow rate, was in the range of 20–80%. The dryer was shown to be capable of specific moisture extraction rates ranging from 0.65 to 1.75 kg/kW h. The heating coefficient of performance of the dryer was found to be between 2.47 and 3.95, depending upon condenser and evaporator temperatures. The drying curve equation for the wool was given, and the experimental findings were also discussed in the light of available models.

At the advent of the Montreal protocol, R134a has been suggested as an alternate refrigerant to R12. R134a is a high global warming potential gas and needs to be controlled as per the Kyoto protocol. It is reported that there is no single refrigerant or mixture available to satisfy both the ozone depletion potential (ODP) and global warming potential (GWP) issues. In this scenario, the objective of this work was, to develop an eco-friendly refrigerant mixture with negligible ODP and GWP values that is nearly equivalent to R12 in its performance. R123 is a potential refrigerant with very low ODP and GWP values, but due to its high suction specific volume and high boiling point, it has not been considered as an alternate refrigerant to R12. In this work, to overcome the above said problems, R290 has been identified as suitable for combination with R123 in a refrigerant mixture. Using REFPROP for analysis, it was found that the performance parameters for a mixture containing 70% R123 and 30% R290 were near matching with R12. This has been further confirmed experimentally by conducting a base line test with R12 and tests with the new mixture. The flow characteristics of the mixture were compared with R12 and presented.

Siloxanes are widely used in industrial processes and consumer products. Some of them reach the wastewater. Siloxanes are not decomposed in the activated sludge process and partly concentrate in the sludge. During anaerobic digestion of the sludge, they volatilise into the formed biogas. Combustion of silicon containing gases, e.g., when producing electricity, produces, however, the abrasive microcrystalline silica that has chemical and physical properties similar to those of glass and causes serious damage to gas engines, heat exchangers and catalytic exhaust gas treatment systems.The growing consumption of silicones and siloxanes and the subsequent increased concentration in wastewater, together with the increasing interest in the production of biogas and “green energy” in sewage treatment plants, has created significant concern about the presence of siloxanes and the related damage (fouling etc.) in the biogas beneficiation equipment.The present paper, therefore, reviews the fundamentals of siloxanes and the current problems of the associated fouling. Moreover, it summarizes the useable methods for siloxane abatement from biogas and makes some recommendations towards preventive actions.

This work presents an experimental study on the application of hydrocarbon mixtures to replace HFC-134a in a domestic refrigerator. The hydrocarbons investigated are propane (R290), butane (R600) and isobutane (R600a). A refrigerator designed to work with HFC-134a with a gross capacity of 239 l is used in the experiment. The consumed energy, compressor power and refrigerant temperature and pressure at the inlet and outlet of the compressor are recorded and analysed as well as the distributions of temperature at various positions in the refrigerator. The refrigerant mixtures used are divided into three groups: the mixture of three hydrocarbons, the mixture of two hydrocarbons and the mixture of two hydrocarbons and HFC-134a. The experiments are conducted with the refrigerants under the same no load condition at a surrounding temperature of 25 °C. The results show that propane/butane 60%/40% is the most appropriate alternative refrigerant to HFC-134a.

This paper reports an experimental investigation of condensation heat transfer and pressure drop of an ozone friendly refrigerant, R-134a, inside a helical tube for climatic conditioning of hot regions. This study concerns the condensation of R-134a flowing through annular helical tubes with different operating refrigerant saturated temperatures. The average pressure drop is measured and compared with data from relevant literature. The measurements of R-134a were performed on mass flow flux ranges from 50 to 680 kg/m2 s. The study provides experimental data that could be used for the design and development of more efficient condensers for refrigeration and air conditioning (A/C) systems working with the same refrigerant.

The pyritic sulphur removal from coal and pyrite by Thiobacillus ferrooxidans was studied in a batch reactor. Microbial oxidation of ferrous iron to the ferric form, the central step in the biodesulphurization process was found to be affected by the substrate and product concentration. Direct microbial oxidation of pyrite was dominant during the exponential phase, while indirect electrochemical oxidation was observed at the stationary phase of the growth. The effect of various parameters, such as pulp density, ferrous and ferric iron concentrations on the rate of biodesulphurization was studied. The rate of pyritic sulphur removal was retarded at higher concentrations of ferrous and ferric iron. Therefore, during the process, the concentrations of Fe(II) and Fe(III) iron in the bioreaction mixture need to be controlled to maintain high rates of pyritic sulphur removal.

The interphase transformer inductance seriously affects the performance of 18 pulse rectifiers. Low inductance values cause non-characteristic harmonics whereas high inductance values increase the rectifier cost and size. Hence, determination of the interphase transformer inductance value is an important problem in the design of 18 pulse rectifiers. In this paper, an approach to determine the optimum inductance value of an interphase transformer is proposed and a practical formula is introduced. The proposed approach has been validated with simulation and experimental studies carried out with designed capacitive loaded autotransformer based 18 pulse rectifier for different IPT inductance values at different load levels. Experimental and simulation results show that cost effective interphase transformer inductance value can be determined with the proposed approach and this value reduces the line current harmonics and improves power factor drastically.

This paper aims to investigate the sectoral energy use in the Turkish economy for the 1980–2000 period when significant changes occurred in the economic and demographic structure of the country. These changes had several impacts on the energy use in the primary sectors such as agriculture, industry and services. Decomposition analysis is conducted on these sectors by using the additive version of the LMDI method due to its advantages over others. Although a close relationship exists between primary energy consumption and GDP, analyses show that significant variations occurred in the sectoral energy use during the 1982, 1988–1989, 1994 and 1998–2000 periods. Such variations are related to the economic policies of the governments. The Turkish economy has undergone a transformation from agricultural to industrial enhanced by rapid urbanization, especially after 1982. However, industrialization has not been completed yet, and the energy demand should be increasing faster than national income until the energy intensity of the country reaches a peak. This study is performed on three basic sectors; however, decomposition into secondary and tertiary sectors will provide detailed information for further investigations.

Electrical power must be available to the consumer in any amount upon demand. Conventional methods of power generation, such as the burning of fossil fuels, hydroelectric plants, and nuclear power plants, have considerable shortcomings. Governmental regulations have increased in quantity and have raised the already rigid standards of producing electric power without further damage to the environment. Electrical power produced by wind energy conversion systems are undergoing extensive research and revitalization as a viable solution to clean air power generation. The basic challenge to scientists and engineers is to develop wind energy conversion systems that produce adequate amounts of power, but at a cost comparable to present conventional methods. This article discusses the background and impact of the modern wind energy conversion system on future power generation.

This paper presents a study of a polymer electrolyte fuel cell (PEFC) multi-stack generator and its power electronic interface dedicated to an on board vehicle power unit. A parallel electric architecture has been designed and tested. First, a dynamic model of the PEFC stack, valid for high frequencies and compatible with power converter interactions, has been developed. This model is used for simulations of the global fuel cell and power converter behaviors. Second, an inventory of generic multi-stack fuel cells architectures is presented in order to couple electrically the fuel cell stacks to an on board DC bus (in series, parallel, through magnetic coupling…). This state of the art is completed by an overview of several candidate power converter topologies for fuel cells. Then, among all the possible technical solutions, an original power converter architecture using a high frequency planar transformer is proposed, which allows parallel and series magnetic couplings of two fuel cell stacks. Then, the study focuses on a first step, which is the association of two PEFC stacks. Such a structure, having good efficiency, is well adapted for testing and operation of fuel cells in normal and degraded working modes, which correspond to real constraints on board a vehicle. Finally, experimental validations on a 2 × 500 W twin stack PEFC with power converter interface demonstrate the technological feasibility for the embarked multi-stack fuel cells generator. The 1 kW power level chosen for the experimentation is close to that of a small on board PEFC auxiliary power unit (APU).

This paper presents an overview of the status of offshore wind energy development in the United States. It includes an overview of the research conducted at the University of Massachusetts in the early 1970s on large floating offshore systems and designs for offshore systems sited in the Great Lakes. It also presents a summary of the present US work on offshore energy, including the most recent work in New England as well as national and regional efforts to define the potential offshore wind energy resource. Also included is a review of the regulatory and permitting issues that must be addressed for offshore wind energy systems development. The paper concludes with a summary of current commercial and developmental activities in the US.

The United States Department of Energy's Pittsburgh Energy Technology Center, under its Combustion 2000 program, is working with private industry to develop two kinds of advanced, coal-fired electric power generation systems that will have significantly higher thermal efficiency, superior environmental performance and a lower cost of electricity than current coal-fired plants. The low emission boiler system (LEBS) is a highly advanced pulverized-coal-fired power plant which will be ready for commercial introduction before the year 2001. LEBS uses supercritical steam conditions and substantial low-level heat recovery to achieve an efficiency of 42%. Very low emissions are realized by using advanced combustion technology and pollution controls that are integrated with the boiler. The high performance power system (HIPPS) is based on indirectly fired combined-cycle technology that is capable of 47–50% efficiency. This system uses a gas turbine driven by a clean air working fluid separately heated in a novel high-temperature furnace. Energy recovered from the turbine exhaust drives a steam cycle. HIPPS is planned to be commercially available by 2005. This paper describes the Combustion 2000 program and the technologies being developed for LEBS and HIPPS.

Jordan is an example of a developing country that depends almost exclusively on imported oil. Luckily, Jordan is blessed with good solar energy resources. However, only 24% of Jordanian families are installing solar water heating systems (SWHS). The objective of this research is to forecast the yearly demand on SWHS by the household sector during the period 2001–2005 and to compute the potential energy savings throughout the investigated period due to the use of SWHS. It is found that the net energy collected over the entire investigated period is about 1454.4 million kW h. In addition, the capital savings over the entire investigated period is estimated to be 46.28 million US$ if SWHS are used to heat water instead of the commonly used LPG gas cookers. The results of the research may assist decision makers in the energy sector to implement more comprehensive plans that encourage more families to install SWHS and save on imported oil.

Growing of PV for electricity generation is one of the highest in the field of the renewable energies and this tendency is expected to continue in the next years. Due to the various seasonal, hourly and daily changes in climate, it is relatively difficult to find a suitable analytic model for predicting the performance of a grid-connected photovoltaic (GCPV) plant. In this paper, an artificial neural network is used for modelling and predicting the power produced by a 20 kWp GCPV plant installed on the roof top of the municipality of Trieste (latitude 45°40′N, longitude 13°46′E), Italy. An experimental database of climate (irradiance and air temperature) and electrical (power delivered to the grid) data from January 29th to May 25th 2009 has been used. Two ANN models have been developed and implemented on experimental climate and electrical data. The first one is a multivariate model based on the solar irradiance and the air temperature, while the second one is an univariate model which uses as input parameter only the solar irradiance. A database of 3437 patterns has been divided into two sets: the first (2989 patterns) is used for training the different ANN models, while the second (459 patterns) is used for testing and validating the proposed ANN models. Prediction performance measures such as correlation coefficient (r) and mean bias error (MBE) are presented. The results show that good effectiveness is obtained between the measured and predicted power produced by the 20 kWp GCPV plant. In fact, the found correlation coefficient is in the range 98–99%, while the mean bias error varies between 3.1% and 5.4%.

Integrated coal gasification combined cycle (IGCC) power plants have been looked to as a key technology for the 21st century in order to realize high efficiency and good environmental performance for electricity generation, replacing existing coal fired power plants.Following successful completion of a 200 ton/d pilot project in Nakoso, IGCC technology development in Japan is moving from the stage of a feasibility study to a detailed study to allow final decisions for demonstration plant construction. The feasibility study, jointly conducted by the domestic electric power companies, found MHI's IGCC technology to have several advantages in efficiency and reliability. In parallel with the study, a number of R&D tests have been executed as a national project to facilitate scaling up from the pilot plant to the demonstration plant. This paper introduces the current status of the MHI's IGCC technological development.

Fossil fuels (i.e., petroleum, natural gas and coal), which meet most of the world’s energy demand today, are being depleted fast. Also, their combustion products are causing the global problems, such as the greenhouse effect, ozone layer depletion, acid rains and pollution, which are posing great danger for our environment and eventually for the life in our planet. Many engineers and scientists agree that the solution to these global problems would be to replace the existing fossil fuel system by the hydrogen energy system. Hydrogen is a very efficient and clean fuel. Its combustion will produce no greenhouse gases, no ozone layer depleting chemicals, little or no acid rain ingredients and pollution. Hydrogen, produced from renewable energy (e.g., solar) sources, would result in a permanent energy system, which we would never have to change.However, there are other energy systems proposed for the post-petroleum era, such as a synthetic fossil fuel system. In this system, synthetic gasoline and synthetic natural gas will be produced using abundant deposits of coal. In a way, this will ensure the continuation of the present fossil fuel system.The two possible energy systems for the post-fossil fuel era (i.e., the solar-hydrogen energy system and the synthetic fossil fuel system) are compared with the present fossil fuel system by taking into consideration production costs, environmental damages and utilization efficiencies. The results indicate that the solar-hydrogen energy system is the best energy system to ascertain a sustainable future, and it should replace the fossil fuel system before the end of the 21st century.

This paper focuses on an investigation of the proper capillary tube length for an inverter air conditioner. Air to air variable capacity systems with R-22 and R-407C were tested and modeled. First, the optimum refrigerant charge was determined for four capillary tubes at full load condition by varying the mass charge from 1.1 kg to 1.9 kg. The capillary tube lengths were 1.016 m, 0.914 m, 0.813 m and 0.711 m. The two zone model, the distributed model and the combined model were compared to estimate the optimal charge inventory. The combined model analysed a simple path evaporator, a complex path condenser with a two zone model and a distributed model, respectively. It obtained good agreement with experimental results for the system performances and the optimum mass charge. Furthermore, four capillary tubes with specific optimum mass charges were investigated at compressor frequencies in a range of 30–50 Hz. The R-22 capillary tube obtains the best performance with the addition length of 1.016 m at the lowest frequency. Especially, the length of 0.813 m with R-407C is the appropriate size at the operation frequency of 30–35 Hz. The base capillary tube of 0.914 m is optimum at other frequencies. The model prediction agrees with the experimental data in a range of 40–50 Hz.

High efficiency segmented thermoelectric unicouples (STUs) made of n-type Bi2Te3 and CoSb3 based alloys and p-type Bi2Te3 and CeFe4Sb12 based alloys have recently been developed at the Jet Propulsion Laboratory (JPL). A 1-D analytical model of STUs, which assumes zero side heat losses, is developed and its predictions are compared with some results of experiments performed at JPL to measure the performance parameters of two STUs, uni8 and uni12. Calculations of the effects of contact resistance and side heat losses on the performance of these STUs are presented and discussed. The results indicate that had uni8 and uni12 been well insulated and the contact resistance per leg ∼50 cm2, they could have achieved a conversion efficiency of ∼12%, in the tests performed at Tc=305–316 K and Th=872–885 K. However, the actual contact resistances of ∼146 and 690 cm2 per leg and the side heat losses of 3.7 and 1.83 W, for uni8 and uni12, respectively, limited the peak conversion efficiency in the tests to ∼5.5% and 4.6%, respectively. Calculations indicated that STUs having a total contact resistance ∼50 cm2 per leg and being well insulated on the sides could potentially achieve a peak conversion efficiency of 15% when operated between 973 and 300 K.

A new control method is proposed for three phase high performance induction motor drives. The control system enjoys the advantages of vector control and direct torque control and avoids some of the implementation difficulties of either of the two control methods. In particular, the proposed control system includes a current vector control in connection with a switching table. An extensive comparative performance evaluation of a motor under the proposed control method confirms the effectiveness of the method and its partial superiority over either vector control or direct torque control despite its relative structural simplicity.

The purpose of this study is to determine the thermal reliability and corrosion of the Al–34%Mg–6%Zn alloy as a latent heat energy storage material with respect to various numbers of thermal cycles. The differential scanning calorimeter (DSC) analysis technique was applied to the alloy after 0, 50, 500 and 1000 melting/solidification cycles in order to measure the melting temperatures and the latent heats of fusion of the alloy. The containment materials were stainless steel (SS304L), carbon steel (steel C20) in the corrosion tests. The DSC results indicated that the change in melting temperature for the alloy was in the range of 3.06–5.3 K, and the latent heat of fusion decreased 10.98% after 1000 thermal cycles. The results show that the investigated Al–34%Mg–6%Zn alloy has a good thermal reliability as a latent heat energy storage material with respect to thermal cycling for thermal energy storage applications in the long term in view of the small changes in the latent heat of fusion and melting temperature. Gravimetric analysis as mass loss (mg/cm2), corrosion rate (mg/day) and a microscopic or metallographic investigation were performed for corrosion tests and showed that SS304L may be considered a more suitable alloy than C20 in long term thermal storage applications.

Microalgae present one of the few technologies for the capture and utilization of CO2 emitted by power plants. These microscopic plants would be grown in large open ponds, into which power plant flue gas or pure CO2 (captured from power plants) is sparged, and, after harvesting, the biomass would be converted to a fossil fuel replacement, preferably a high value liquid fuel such as biodiesel. The requirements for large areas of land, favorable climate, and ample water supplies will restrict the potential of this technology. Also, even with rather favorable technical assumptions, the currently projected costs of microalgae-fuels are high, similar to most power plant CO2 capture and disposal options. However, if the technology of microalgae could achieve very high productivities, equivalent to 10% solar energy conversion, and if projected low-cost cultivation, harvesting and processing techniques could be developed, microalgae technology could become a low-cost CO2 mitigation option, particularly if prices for fossil fuels increase in the future. In the nearer-term microalgae CO2 utilization can be integrated with wastewater treatment and reclamation, providing an early application of this technology. Long-term basic and applied R&D are required to develop this technology, as one of the many options that may be required in the future to help preserve our planetary atmosphere and biosphere.

In this paper an integrated approach for on-line induction motor fault detection and diagnosis is presented. The need to insure a continuous and safety operation for induction motors involves preventive maintenance procedures combined with fault diagnosis techniques. The proposed approach uses an automatic three step algorithm. Firstly, the induction motor stator currents are measured which will give typical patterns that can be used to identify the fault. Secondly, the eigenvectors/eigenvalues of the 3D current referential are computed. Finally the proposed algorithm will discern if the motor is healthy or not and report the extent of the fault. Furthermore this algorithm is able to identify distinct faults (stator winding faults or broken bars). The proposed approach was experimentally implemented and its performance verified on various types of working conditions.

Pressure losses as friction factor, and flow patterns in 3D axial flow between sinusoidal corrugated parallel plates with perpendicular directions of corrugation is numerically studied. The flow is assumed to be steady and laminar in the studied range. The numerical procedure is Chorin’s artificial compressibility method with finite difference second order central discretization. Results show that in moderate Reynolds numbers, vortices are formed and they put a great effect on pressure drop. The size of vortices grows with increase in Reynolds number, and also their cores tend to shift toward the flow direction and away from the walls. These vortices are not closed loops, and the streamlines slightly swirl in the circulating zone of vortices. This means that there can be a little convection in these regions and they are not closed dead zones anymore. The linear curve fit of the friction factor diagrams versus Reynolds number in logarithmic scale, shows that friction factor almost obeys a power function of hydraulic Reynolds number in the investigated geometries. With a slight error, this can be assumed as a rough estimation for the product of friction factor and hydraulic Reynolds number. The friction factor grows larger with increase in wave amplitude or decrease in wavelength. Also, when the gap between two plates decreases, friction factor increases. The least friction factor among the investigated geometries is for flat parallel plates.

European R&D for ADS design and fuel development is driven in the 6th FP of the EU by the EUROTRANS Programme. In EUROTRANS, the longer-term EFIT development, the european facility for industrial transmutation, aims at a generic conceptual design of a full transmuter. A CERCER U-free fuel core with an MgO matrix and a CERMET core with a Mo-92 matrix have been designed. Both the CERCER and the CERMET EFIT concept were optimized towards: a high transmutation efficiency, high burn-up, low reactivity swing, low power peaking, adequate subcriticality, reasonable beam requirements and a high level of safety. Protected and unprotected transients which are initiated by a mismatch of power-to-flow or resulting from a beam disturbance or overpower situation were analyzed. Potentials which can lead to the introduction of positive reactivity into the core were identified, as e.g. the steam generator tube rupture (SGTR) accident or the pin failure with a gas release from the fission gas plena. Both for the CERCER and the CERMET fuelled core the design and safety analyses are close to completion in EUROTRANS and thus a first preliminary résumé can be drawn on the achieved design and safety goals. In addition, scenario studies in the framework of the PATEROS CA project of the 6th FP highlighted the specific needs on transmutation machines serving in countries with different nuclear options. Based on these studies in the 6th FP first reflections can be performed on needs or options for further optimizing an EFIT type ADS.

Maximum power point tracking (MPPT) techniques are usually used for solar power applications. This paper discusses: (1) various connection methods between solar arrays and loads and (2) various maximum power point control methods and MPPT algorithms. In this paper, the solar array is treated as a current source instead of a voltage source. Analytical models are built for the solar array and converter on the basis of the data sheet of the manufacturer and the principle of energy conservation. An improved MPPT algorithm was proposed to reduce the power loss in the tracking process. A digital signal processor (DSP) based controller was constructed to implement the proposed MPPT control, and the experimental results are presented.

This paper presents a new maximum power point tracking algorithm based on current control for a single stage grid connected photovoltaic system. The main advantage of this algorithm comes from its ability to predict the approximate amplitude of the reference current waveform or power that can be derived from the PV array with the help of an intermediate variable β. A variable step size for the change in reference amplitude during initial tracking helps in fast tracking. It is observed that if the reference current amplitude is greater than the array capacity, the system gets unstable (i.e. moves into the positive slope region of the p–v characteristics of the array). The proposed algorithm prevents the PV system from entering the positive slope region of the p–v characteristics. It is also capable of restoring stability if the system goes unstable due to a sudden environmental change. The proposed algorithm has been tested on a new single stage grid connected PV configuration recently developed by the authors to feed sinusoidal current into the grid. The system is operated in a continuous conduction mode to realize advantages such as low device current stress, high efficiency and low EMI. A fast MPPT tracker with single stage inverter topology operating in CCM makes the overall system highly efficient. Specific cases of the system, operating in just discontinuous current mode and discontinuous current mode and their relative merits and demerits are also discussed.

CO2 can be removed from the flue gas of existing pulverised coal fired power stations by retrofitting a new process which recovers the CO2 as a pure liquid by distillation. The boiler is modified to burn the fuel in a CO2 and Oxygen mixture instead of air. Flue gas is partly recycled and mixed with oxygen from an air separation plant for fuel combustion. Excess flue gas in compressed, liquefied and distilled into pure CO2 and SO2 plus NO2 products. Net power generating efficiency and capital cost of the retrofit are given. The economics of CO2 disposal in an offshore depleted gas reservoir and for enhanced oil recovery are presented.

FC-72 and HFE-7100 dielectric liquids are favored for immersion cooling applications of computer chips. This paper reports the results of series of experiments that systematically investigated nucleate boiling of both FC-72 and HFE-710 on a plain porous graphite surface measuring 10 × 10 mm. The obtained values of the nucleate boiling heat transfer coefficient and critical heat flux (CHF), at different surface orientations, 0° (upward facing) to 180° and liquid subcooling up to 30 K are compared. In addition to the absence of temperature excursions prior to boiling incipience, the CHF increases linearly with increased liquid subcooling but at a rate that is ∼10% higher for HFE-7100 than that for FC-72. The CHF for HFE-7100 is typically 10% to 15% higher than that for FC-72, however, the maximum nucleate boiling heat transfer coefficient, occurring at or near the end of the fully developed nucleate boiling region, is ∼57% higher for FC-72 than that for HFE-7100 and increases also linearly with increased liquid subcooling. The CHF correlation developed accounts for the effects of surface characteristics (smooth, porous, or micro-porous), liquid properties and subcooling, and surface inclination and fits present and reported values by other investigators to within ±10%.

Enhanced boiling of HFE-7100 dielectric liquid on porous graphite measuring 10 mm × 10 mm is investigated, and results are compared with those for smooth copper (Cu) of the same dimensions. Although liquid is out-gassed for hours before performing the pool boiling experiments, air entrapped in re-entrant type cavities, ranging in size from tens to hundreds of microns, not only enhanced the nucleate boiling heat transfer and the critical heat flux (CHF), but also, the mixing by the released tiny air bubbles from the porous graphite prior to boiling incipience enhanced the natural convection heat transfer by ∼19%. No temperature excursion is associated with the nucleate boiling on porous graphite, which ensues at very low surface superheat of 0.5–0.8 K. Conversely, the temperature overshoot at incipient boiling on Cu is as much as 39.2, 36.6, 34.1 and 32.8 K in 0 (saturation), 10, 20 and 30 K subcooled boiling, respectively. Nucleate boiling ensues on Cu at a surface superheat of 11.9, 10.9, 9.5 and 7.5 K in 0 (saturation), 10, 20 and 30 K subcooled boiling, respectively. The saturation nucleate boiling heat flux on porous graphite is 1700% higher than that on Cu at a surface superheat of ∼10 K and decreases exponentially with increased superheat to ∼60% higher near CHF. The CHF values of HFE-7100 on porous graphite of 31.8, 45.1, 55.9 and 66.4 W/cm2 in 0 (saturation), 10, 20 and 30 K subcooled boiling, are 60% higher and the corresponding superheats are 25% lower than those on Cu. In addition, the rate of increase in CHF with increased liquid subcooling is 50% higher than that on Cu.

The paper presents two high power, high frequency DC–DC power processors utilising a single phase AC link that is suitable for low voltage DC distribution systems. Expressions for active and apparent power transmitted through the isolation transformer and the primary side power factor are derived. The analysis accounts for the contribution made by harmonics towards power transmission. In the available literature, analysis of similar power processors ignores harmonics and assumes sinusoidal voltage and current waveform variation. It will be shown that ignoring power transfer due to harmonics leads to significantly lower calculated values of active and apparent power and to higher values of operating power factor compared with those obtained in practice. The best operating range of phase shift to ensure operation with high energy efficiency is identified. The effects of parasitic components on performance are also investigated. Simulation and analytical results for a 10 kW converter interconnecting 68–75/725 V DC busses are presented. Experimental results taken at a lower input voltage (24 V instead of 72) are also included to validate the simulation waveforms.

In this paper, performance assessment of various building cogeneration systems is conducted through energy and exergy efficiencies. The cogeneration plants considered include steam-turbine system, gas-turbine system, diesel-engine system, and geothermal system. Here, the cogeneration operation refers to the simultaneous generation of electrical power and heating for buildings (especially for space heating and hot water). Selected actual operating data are employed for analysis and performance assessment. The same amount of electrical and thermal product outputs is considered for all systems, except the diesel, to facilitate comparisons. Also, the effects of certain operating parameters (e.g., steam pressure, water temperature) on the energy and exergy efficiencies are investigated. The diesel-engine and geothermal systems appear to be thermodynamically more attractive, in that they have higher exergy efficiencies, than steam-turbine and gas-turbine systems. The results demonstrate that exergy analysis is a useful tool in performance assessments of cogeneration systems and permits meaningful comparisons of different cogeneration systems based on their merits. Such results can allow the efficiency of cogeneration systems to be increased, and the applications of cogeneration in larger energy systems to be configured more beneficially, leading to reductions in fuel use and environmental emissions.

An 85 m3 floating drum biogas plant was installed at the dairy farm of HP Agricultural University, Palampur, in 1989 to meet the energy needs of cooking food in the veterinary hostel mess and for general dairy requirements. It cost nearly Rs. 0.21 million ($6293), including the cost of an 800 m gas pipe line, and is working satisfactorily without any major problem except breakage of the central guide of its gas holder. With the feed rate of 17 q cattle dung/day, 50 m3 and 30 m3 biogas was obtained in the summer and winter months, respectively, during 1989–1991. The reduction of feed rate to 9 q cattle dung/day in 1992 onwards resulted in lowering the gas production of 25 m3 and 18 m3 in the summer and winter months, respectively. This gas was just sufficient to meet 73% (9466 MJ/month) and 53% (7019 MJ/month) of the energy needs for cooking meals in the hostel alone in the summer and winter months, respectively, during the course of study. Considering the biogas and manure obtained from the plant, the income–cost ratios during the period 1989–1991 and 1992–1997 were found to be 1.44 and 1.15, respectively, suggesting that, though the plant was under fed relative to the requisite feed rate (21 q cattle dung/day), the installation of this plant was an economically viable proposition.

British Coal Corporation is taking a proactive stance in researching the issues associated with the possibility of enhanced global warming. One aspect of this research is the evaluation of the options which might conceivably be required if it turns out to be necessary to reduce CO2 emissions from coal fired power plants more than can be achieved by improved efficiency.A programme of assessment studies has been undertaken to evaluate the impacts on plant thermal efficiency of various options for CO2 removal for ultimate storage in some form of long term repository. Preliminary screening studies of the integration of CO2 recovery into coal fired power generation processes have indicated that routes based on Integrated Gasification Combined Cycles (IGCC) are preferred to those based on combustion.A series of options based on IGCC with CO shift is presented which compares alternative means of separating hydrogen from CO2, as required by this process route. Technologies evaluated include chemical and physical solvent scrubbing and membrane separation. This work was carried out with the intention of identifying thermally efficient flowsheets and the associated process development needs.The paper concludes by presenting economic considerations and describing British Coal's future research programme in this area.

IGCC technology per se involves the potential of highest efficiencies, thus reducing the CO2 output accordingly. Moreover, the intermediate stage of synthesis gas makes it possible to remove most of the carbon compounds before combustion with acceptable additional auxiliary power demand. The separated CO2 stream is of highest purity and therefore suited for disposal e.g. in the deep sea or for reuse in chemical syntheses. So, methanol synthesis based on power plant CO2 has been investigated.This contribution presents the results of a pre-basic design for a coal-fired 300 MW-class IGCC power plant with methanol production using an external H2 source. Based on a Siemens Model V94.3A gas turbine-generator, the standard IGCC has been equipped with plant components including CO shift reactors, CO2 scrubber, methanol synthesis reactors and distillation unit; additional investment costs amount to approx. 25 %. This concept is based solely on proven process engineering methods.Primary energy utilization as well as the resulting methanol production costs based on appropriate generating costs are discussed. Comparative CO2 emission figures make the advantage of such a coproduction process regarding this perfectly clear.

Commercially proven technology developed by Kerr-McGee Chemical Corp., and now jointly licensed by Kerr-McGee and ABB Lummus Crest Inc., is being used for the production of food-grade and chemical-grade CO2 products from coal. The technology can also be used to recover CO2 from oil or gas-fired boiler flue gases, gas turbine and engine exhausts, and other oxygen-containing waste gases. This paper describes the Kerr-McGee/Lummus Crest appraoch for recovering CO2 from oxygen-containing gases, as well as discusses design aspects of a unit which recovers food-grade CO2 from coal-fired boiler stack gases. Markets for CO2 are also discussed.

In this study, a new shell and tube heat exchanger optimization design approach is developed. Artificial Bee Colony (ABC) has been applied to minimize the total cost of the equipment including capital investment and the sum of discounted annual energy expenditures related to pumping of shell and tube heat exchanger by varying various design variables such as tube length, tube outer diameter, pitch size, baffle spacing, etc. Finally, the results are compared to those obtained by literature approaches. The obtained results indicate that Artificial Bee Colony (ABC) algorithm can be successfully applied for optimal design of shell and tube heat exchangers.Highlights► Artificial Bee Colony for shell and tube heat exchanger optimization is used. ► The total cost is minimized by varying design variables. ► This new approach can be applied for optimization of heat exchangers.

This work focuses on selecting new absorbents for CO2 capture. Absorption of CO2 was studied at 40 °C using both single and mixed amine-based absorbents. The experimental results show that most absorbents tested have a poorer performance than MEA, but that aqueous AEEA might be a possible contender. In addition to the absorption measurements, the VLE of CO2 in the selected absorbent, the aqueous 2.9 M AEEA, were studied at 40 and 120 °C. The equilibrium partial pressures of CO2 in the aqueous 2.9 M AEEA at the temperature of removal (40 °C) and that of regeneration (120 °C) are lower than for aqueous 5.0 M MEA, but the maximum net cyclic capacity is somewhat higher.

The capture of H2S or SO2 with Ca-based absorbents, limestone and dolomite, was investigated under a periodically changing condition between reducing and oxidizing atmospheres, taking account of the coexistence of these atmospheres in a fluidized-bed coal gasifier. The degree of desulfurization in the reducing atmosphere was large compared with that in the oxidizing atmosphere. Apparent difference in desulfurization behavior was scarcely observed between limestone and dolomite. Stabilization of CaS in in situ desulfurization residues derived from both limestone and dolomite to harmless CaSO4 was also investigated. Absorbents maintaining porous-structure, such as dolomite, will be preferable for desulfurization in the coal gasification/combustion types of hybrid power systems.

A systematic investigation is made of the two-stage vapour absorption refrigeration system employing the refrigerant absorbent combinations of NH3H2O and NH3LiNO3. The system consists of coupling two conventional absorption cycles so that the first-stage evaporator produces cooling water to circulate in the absorber of the second stage. The effect of operating variables such as generator temperature, evaporator temperature, absorber temperature and condenser temperature on the coefficient of performance (COP), heat transfer rates and relative circulation have been studied for both single-stage and two-stage absorption refrigeration systems. It is found that the COP is higher for NH3LiNO3 than for NH3H2O, in both single-stage and two-stage absorption systems, especially at higher generator temperatures. Furthermore, the minimum evaporator temperature achieved is lower for NH3LiNO3, and the system can be operated at lower generator temperatures.

A new electrolyte has been proposed for the deposition of nickel-black selective coatings for use in flat-plate solar collectors. The authors have studied the influence of various ingredients and operating parameters on the appearance of the black coatings so obtained with special reference to their optical values (α, ϵ). The coating exhibits better corrsion resistance than the well known black-nickel coatings (which contains nickel, zinc and sulphur) apart from having thermal stability upto 380°C. With no zinc in the deposit, this can be used in place of black nickel coatings with less corrosion problems.

This is an analytical study of the performance of the stationary-reflector/tracking-absorber (SRTA) solar collector with tubular absorber. The mathematical treatment and the derived formulae are generalized for any rim angle and any absorber-to-reflector diameter ratio. The effects of these two parameters on the average concentration ratio are investigated. Different multi-reflection zones of the mirror are identified. Their contributions to the total concentrated power and the local concentration ratio, at different absorber points, are assessed. The concentration profile along the absorber is determined under different conditions. The influence of mirror reflectance on the flux density at different points is evaluated. The circumferentially-distorted concentration profile at times of oblique incidence is displayed. The absorber surface is divided into bright, faint and dim regions. A mathematical procedure is presented to contour these regions. Their occurrence and area growth are shown to be dependent on the rim angle and diameter ratio.