Showing papers in "Journal of Renewable and Sustainable Energy in 2010"

Dewatering of microalgal cultures: A major bottleneck to algae-based fuels

Abstract: Microalgae dewatering is a major obstruction to industrial-scale processing of microalgae for biofuel production. The dilute nature of harvested microalgal cultures creates a huge operational cost during dewatering, thereby, rendering algae-based fuels less economically attractive. Currently there is no superior method of dewatering microalgae. A technique that may result in a greater algal biomass may have drawbacks such as a high capital cost or high energy consumption. The choice of which harvesting technique to apply will depend on the species of microalgae and the final product desired. Algal properties such as a large cell size and the capability of the microalgae to autoflocculate can simplify the dewatering process. This article reviews and addresses the various technologies currently used for dewatering microalgal cultures along with a comparative study of the performances of the different technologies.

Nanofluid-based direct absorption solar collector

Abstract: Solar energy is one of the best sources of renewable energy with minimal environmental impact. Direct absorption solar collectors have been proposed for a variety of applications such as water heating; however the efficiency of these collectors is limited by the absorption properties of the working fluid, which is very poor for typical fluids used in solar collectors. It has been shown that mixing nanoparticles in a liquid (nanofluid) has a dramatic effect on the liquid thermophysical properties such as thermal conductivity. Nanoparticles also offer the potential of improving the radiative properties of liquids, leading to an increase in the efficiency of direct absorption solar collectors. Here we report on the experimental results on solar collectors based on nanofluids made from a variety of nanoparticles (carbon nanotubes, graphite, and silver). We demonstrate efficiency improvements of up to 5% in solar thermal collectors by utilizing nanofluids as the absorption mechanism. In addition the experiment...

WindFloat: A floating foundation for offshore wind turbines

Abstract: This manuscript summarizes the feasibility study conducted for the WindFloat technology. The WindFloat is a three-legged floating foundation for multimegawatt offshore wind turbines. It is designed to accommodate a wind turbine, 5 MW or larger, on one of the columns of the hull with minimal modifications to the nacelle and rotor. Potential redesign of the tower and of the turbine control software can be expected. Technologies for floating foundations for offshore wind turbines are evolving. It is agreed by most experts that the offshore wind industry will see a significant increase in activity in the near future. Fixed offshore turbines are limited in water depth to ∼30–50 m. Market transition to deeper waters is inevitable, provided that suitable technologies can be developed. Despite the increase in complexity, a floating foundation offers the following distinct advantages: Flexibility in site location; access to superior wind resources further offshore; ability to locate in coastal regions with limited shallow continental shelf; ability to locate further offshore to eliminate visual impacts; an integrated hull, without a need to redesign the transition piece between the tower and the submerged structure for every project; simplified offshore installation procedures. Anchors are significantly cheaper to install than fixed foundations and large diameter towers. This paper focuses first on the design basis for wind turbine floating foundations and explores the requirements that must be addressed by design teams in this new field. It shows that the design of the hull for a large wind turbine must draw on the synergies with oil and gas offshore platform technology, while accounting for the different design requirements and functionality of the wind turbine. This paper describes next the hydrodynamic analysis of the hull, as well as ongoing work consisting of coupling hull hydrodynamics with wind turbine aerodynamic forces. Three main approaches are presented: The numerical hydrodynamic model of the platform and its mooring system; wave tank testing of a scale model of the platform with simplified aerodynamic simulation of the wind turbine; FAST, an aeroservoelastic software package for wind turbine analysis with the ability to be coupled to the hydrodynamic model. Finally, this paper focuses on the structural engineering that was performed as part of the feasibility study conducted for qualification of the technology. Specifically, the preliminary scantling is described and the strength and fatigue analysis methodologies are explained, focusing on the following aspects: The coupling between the wind turbine and the hull and the interface between the hydrodynamic loading and the structural response.

Experimental study of the horizontally averaged flow structure in a model wind-turbine array boundary layer

Abstract: When wind turbines are deployed in large arrays, their ability to extract kinetic energy from the flow decreases due to complex interactions among them, the terrain topography and the atmospheric boundary layer. In order to improve the understanding of the vertical transport of momentum and kinetic energy across a boundary layer flow with wind turbines, a wind-tunnel experiment is performed. The boundary layer flow includes a 3×3 array of model wind turbines. Particle-image-velocity measurements in a volume surrounding a target wind turbine are used to compute mean velocity and turbulence properties averaged on horizontal planes. Results are compared with simple momentum theory and with expressions for effective roughness length scales used to parametrize wind-turbine arrays in large-scale computer models. The impact of vertical transport of kinetic energy due to turbulence and mean flow correlations is quantified. It is found that the fluxes of kinetic energy associated with the Reynolds shear stresses a...

The wave energy resource along Australia’s Southern margin

Abstract: The Southern Australian margin is one of the most energetic regions in the world suitable for the extraction of wave energy for electricity generation. We have produced a data set in which the deep-water wave energy resource for the region is described by three representative deep-water wave states, equivalent to the 10th, 50th, and 90th percentiles of the deep-water wave energy flux, derived from archives of the USA National Oceanic and Atmospheric Administration (NOAA) WaveWatch III (NWW3) operational wave model. The Simulating WAves Nearshore (SWAN) wave model is then applied along the full Southern Australian margin to propagate these representative wave states into the near-shore region to quantify the effects of shallow water processes such as refraction, shoaling, and bottom friction. The wave energy incident on the 25-m isobath (∼30–50 kW/m) is approximately 35%–50% less than the World Energy Council estimates of offshore wave energy but is approximately 20% greater than the energy observed from l...

Use of an autonomous sensor to evaluate the biological performance of the advanced turbine at Wanapum Dam

Abstract: Hydropower is the largest renewable energy resource in the United States and the world. However, hydropower dams have adverse ecological impacts because migrating fish may be injured or killed when they pass through hydroturbines. In the Columbia and Snake River basins, dam operators and engineers are required to make those hydroelectric facilities more fish-friendly through changes in hydroturbine design and operation after fish population declines and the subsequent listing of several species of Pacific salmon under the Endangered Species Act of 1973. Public Utility District No. 2 of Grant County, Washington, requested authorization from the Federal Energy Regulatory Commission to replace the ten turbines at Wanapum Dam with advanced hydropower turbines designed to improve survival for fish passing through the turbines while improving operation efficiency and increasing power generation. As an additional measure to the primary metric of direct injury and mortality rates of juvenile Chinook salmon using balloon tag-recapture methodology, this study used an autonomous sensor device—the Sensor Fish—to provide insight into the specific hydraulic conditions and physical stresses experienced by the fish as well as the specific causes of fish biological response. We found that the new hydroturbine blade shape and the corresponding reduction of turbulence in the advanced hydropower turbine were effective in meeting the objectives of improving fish survival while enhancing operational efficiency of the dam. The frequency of severe events based on Sensor Fish pressure and acceleration measurements showed trends similar to those of fish survival determined by the balloon tag-recapture methodology. In addition, the new turbine provided a better pressure and rate of pressure change environment for fish passage. Overall, the Sensor Fish data indicated that the advanced hydroturbine design improved passage of juvenile salmon at Wanapum Dam.

Renewable energy of waste heat recovery system for automobiles

Abstract: A system to recover waste heat comprised of eight thermoelectric generators (TEGs) to convert heat from the exhaust pipe of an automobile to electrical energy has been constructed. Simulations and experiments for the thermoelectric module in this system are undertaken to assess the feasibility of these applications. In order to estimate the temperature difference between thermoelectric elements, a network of thermal resistors is constructed. The results assist in predicting power output of TEG module more precisely. Three configurations of heat sinks, which are comprised of 10, 22, and 44 fins, are applied in this simulation. The results of the simulations show the average thermal resistance of these heat sinks in each section of the system with varied velocity of external flow. As the performance of a TEG module is influenced by an applied pressure through the effect of the thermal contact resistance, we clamp the TE module to our experimental apparatus; the relation between power output and pressure applied in this case is presented. Besides simulations, the system is designed and assembled. Measurements followed the connection of the system to the middle of an exhaust pipe. Through these simulations and experiments, the power generated with a commercial TEG is presented. The results establish the fundamental development of materials that enhance the TEG efficiency for vehicles.

Computational fluid dynamics analysis of a twisted three-bladed H-Darrieus rotor

Abstract: A steady-state two-dimensional computational fluid dynamics analysis was performed using FLUENT 6.2 software to analyze the performance of a twisted three-bladed H-Darrieus rotor. The flow over the rotor was simulated by using unstructured-mesh finite volume method coupled with moving mesh technique to solve mass and momentum conservation equations. The standard k-e turbulence model was chosen. Second-order upwind discretization scheme was adopted for pressure-velocity coupling of the flow. The aerodynamic coefficients, such as lift coefficient, drag coefficient, and lift-to-drag coefficient, were evaluated with respect to angle of attack for two chord Reynolds numbers. The power coefficient of the rotor was also evaluated. The results were validated by using experimental values for the twisted three-bladed H-Darrieus rotor. The experiments were earlier conducted in a subsonic wind tunnel available in the department. The results showed good matching between the two approaches. The effect of twist angle at...

Effects of global warming on wind energy availability

Abstract: The use of wind energy reduces our greenhouse gas emissions into the atmosphere. In this study, we proposed a generic power-law relationship between global warming and the usable wind energy (Betz’s law). The power law index (∼4, region dependent) is then determined using simulated atmospheric parameters from eight global coupled ocean-atmosphere climate models (CGCMs). It is found that the power-law relationship holds across all eight climate models and also is time scale independent. Reduction of wind power scales with the degree of warming according to a generic power-law relationship. Thus, the earlier we switch to clean energy, and thereby decrease the global climate warming trend, the more cost-effective will be the harnessing of wind energy. This relationship is an area-averaged consequence of the reduced poleward temperature gradient as the climate warms during the 21st Century; it does not imply spatial uniformity over a region of interest.

Fundamentals and applications of the photocatalytic treatment for the removal of industrial organic pollutants and effects of operational parameters: A review

Abstract: Photocatalysis process, as an environmental application, is a relatively novel subject with tremendous potential in the near future. A number of studies determine the economic viability of applying various ultraviolet advanced oxidation processes for the purpose of degradation and destroying of various pollutant solutions. The present paper reviews the treatment of hazardous wastewater bearing organic compounds and the effects of various parameters such as pH, initial concentration, mass of catalyst, wavelength, light intensity, electron acceptor, temperature, etc., with the treatment cost for different reactor type. This study investigates the effect of various types of waste-water treatment parameters and the treatment cost for various designs of photocatalytic reactors, using both solar and artificial light, have been proposed for their different types of pollutants.

The budget approach: A framework for a global transformation toward a low-carbon economy

Abstract: Latest research shows that there is only a realistic chance of restricting global warming to 2 °C if a limit is set to the total amount of CO2 emitted globally between now and 2050 (global carbon dioxide budget). We move this global budget to the forefront of our considerations regarding a new global climate treaty in the post-Copenhagen process. [The authors are members of the “German Advisory Council on Global Change” (WBGU). The WBGU recently published a study on “Solving the climate dilemma: The budget approach.” This paper builds on the fundamental ideas and findings of the WBGU study and demonstrates that the budget approach could serve as a cornerstone for an institutional design for a global low-carbon economy.] Combining findings from climate science and economics with fundamental concepts of equity, the “budget approach” provides concrete figures for the emission allowances that are still available to countries, assuming they want to prevent the destabilization of the planet’s climate system. Ou...

Critical evaluation of wind speed frequency distribution functions

Abstract: Over the past few years a number of new mathematical functions have been proposed for wind speed probability density distributions. The most commonly used function that has been cited in literature has been the two-parameter Weibull function. However, in recent years studies have shown that the two-parameter Weibull function might be inadequate in modeling the wind speed probability density distributions or independent of whether the distribution is of unimodal or bimodal nature. For the unimodal distributions, the inadequacy may be due to the intricate behavior of the distribution, which prevents it to be satisfyingly modeled by a two-parameter model. For the bimodal behavior, the two-parameter Weibull function, which produces only a unimodal distribution, is simply inadequate to model it appropriately. Therefore, in recent years, alternative functions have been suggested for both unimodal and bimodal distributions, seeking more involved functions to better model these distributions. This article involve...

Development of a dye with broadband absorbance in visible spectrum for an efficient dye-sensitized solar cell

Abstract: A blended dye composed of five organic dyes, namely, Rose Bengal, Eosin-Y, Rhodamine-B, Fast Green, and Acridine Orange, was developed and tested for various solar cell parameters of ZnO based dye-sensitized solar cell (DSSC). A comparison of the absorption spectra of dyes adsorbed on ZnO electrode revealed that the blended dye efficiently absorbs light in the entire visible region as compared with the individual dye. Six DSSCs were fabricated using the five individual dyes and one developed blended dye. The photovoltaic performance of the cells was examined by determining the various parameters such as open-circuit voltage, short-circuit current, energy conversion efficiency, fill factor, series resistance, and shunt resistance. Incident photon to current conversion efficiency was also measured to correlate the effect of the blended dye on the significant improvement of the solar cell parameters. The sensitization of ZnO electrode with blended dye has resulted in a maximum energy conversion efficiency of...

Evaluation of active flow control applied to wind turbine blade section

Abstract: A feasibility study for implementing active flow control (AFC) methods to improve the performance of wind turbines was performed. The experimental effort investigated the impact of zero-mass-flux (ZMF) piezofluidic actuators attempting to control boundary layer separation from thick airfoils that are suitable for wind turbine rotor blades. It was demonstrated that the ZMF actuators can replace passive vortex generators that are commonly used for boundary layer separation delay, without the inherent drag penalty that the passive devices impose. It has been shown that ZMF fluidic actuators are suitable for flow control in wind turbine application due to the fact that they are adjustable for wider Reynolds number range, while vortex generators are tuned to perform well in one design point. It was demonstrated that AFC can effectively double the maximum lift of this airfoil at low Reynolds numbers. A possible application is a significant reduction of the turbine start-up velocity. It was also found that even for a contaminated blade, AFC is capable to delay the stall and decrease the drag using low energy expenditure, therefore restoring and even surpassing the clean airfoil performance. The effectiveness of the AFC method was examined using a newly defined aerodynamic figure of merit. Various scaling options for collapsing the effect of the excitation magnitude on the lift alternation due to the activation of zero-mass-flux periodic excitation for boundary layer separation control are proposed and examined using experimental data.

Integrated energy and environmental systems analysis methodology for achieving low carbon cities

Abstract: Cities are responsible for nearly 75% of the world’s energy consumption; expectedly, about 90% of future growth will occur in urban areas. However, we consider that cities will be at the forefront of implementing groundbreaking technologies and policies, as evidenced in the initiatives taken by many cities here and worldwide to resolve issues in energy and climate change. In addition to affording energy and environmental benefits, investments in energy efficient and renewable technologies have huge potential to boost local economies, as demonstrated by the recent federal allocation of stimulus funding. Inclined to give priority to stopgap measures, many cities tend to regard comprehensive long-term planning as secondary. However, such solutions would bring multiple benefits to the community. The paper showcases an energy and environment systems model to provide a quantitative vision of technology and management strategy options for effectively deploying energy efficiency and renewable energy for reducing the carbon footprint, while sustainably maintaining the energy demands of the community and the servicing environmental infrastructure. We provide results of a case study completed for New York City, to showcase usefulness of long-term planning for achieving low carbon cities. Combined with appropriate stakeholder participation, such a technology explicit bottom-up approach holds the promise of influencing the current energy planning, environmental regulatory regime, including multimedia aspects of carbon control for cities locally and internationally.

Mapping available Ocean Thermal Energy Conversion resources around the main Hawaiian Islands with state-of-the-art tools

Abstract: This paper aims to demonstrate how the evaluation of Ocean Thermal Energy Conversion (OTEC) resources can benefit from currently available high-resolution ocean models. The case of waters around the main Hawaiian Islands is presented because of its relevance to the future development of OTEC. OTEC resources are defined here by ocean temperature differences between water depths of 20 and 1000 m, with little loss of generality. Using state-of-the-art tools like the HYCOM+NCODA (1/12°) model affords the possibility to track changes on a daily basis over a wide area (e.g., 17 °N to 24 °N and 153 °W to 162 °W). An examination of numerical data over a time period of 2 years reveals interesting geographical patterns. It is found that average OTEC temperature differences are consistently higher (by about 1 °C) west of the islands, whereas the amplitude of the yearly cycle globally decreases from north to south as expected. Better OTEC resources in the lee of the islands are attributed to the narrow eastward-flowi...

Investigations on emission characteristics of the pongamia biodiesel–diesel blend fuelled twin cylinder compression ignition direct injection engine using exhaust gas recirculation methodology and dimethyl carbonate as additive

Abstract: Experiments were carried out on a twin cylinder direct injection compression ignition engine using pongamia biodiesel–diesel blend as fuel with exhaust gas recirculation (EGR) and dimethyl carbonate (DMC) as additive. The experimental results showed that pongamia biodiesel–diesel blend fuelled engine with EGR and DMC can simultaneously reduce smoke and nitric oxide (NOx) emission. The NOx emission was reduced by about 17.68% for 10% of EGR introduction and about 13.55% increase in smoke emission. When dimethyl carbonate was added with EGR, the engine emits lower smoke with lesser NOx emission, and it showed that the smoke reduction rate had a linear relationship with DMC percentage. The carbon monoxide (CO) and hydrocarbon (HC) emissions also decreased when DMC was added. However, the addition of DMC with EGR caused an increase in both BSEC and BTE.

Renewable energy and low carbon economy transition in India

Abstract: Cooperation of large developing countries such as India would be important in achieving a low carbon future, which can help in restricting the global temperature rise to 2 °C. Global modeling studies of such low carbon scenarios point to a prominent role for renewable energy. This paper reports scenarios for a low carbon future in India. An integrated modeling framework is used for assessing the alternate development pathways having equal cumulative CO2 emissions. The modeling period ranges from 2005 to 2050. The first pathway assumes a conventional development pattern together with a carbon price that aligns India’s emissions to an optimal 450 ppmv CO2-eq. stabilization global response. The second emissions pathway assumes an underlying sustainable development pattern. A low carbon future will be good for renewable energy under both the development pathways, though the share of renewable energy will be higher under a sustainable pathway. Renewable energy faces competition from low carbon technologies lik...

The feasibility and current estimated capital costs of producing jet fuel at sea using carbon dioxide and hydrogen

Abstract: A comparative cost/benefit and energy balance analysis addresses the critical scientific and technical challenges that impact the economic feasibility of synthesizing up to 100 000 gal per day of jet fuel at sea using carbon dioxide (CO2) and hydrogen (H2) from the sea. Included in this analysis are the capital cost, operation and maintenance, and electrical generation cost for synthesizing jet fuel at sea using either ocean thermal energy conversion or nuclear power processes as the energy source. The results suggest that jet fuel could be produced at sea for $3 to $6/gal. Comparing these costs with current and historical prices of fuel purchased by the Department of Defense provides insight into the economic and operational benefits of a sea-based fuel synthesis process for the Navy.

Technology roadmap for low carbon society in China

Abstract: Mid- and long-term energy requirements and greenhouse gas emission scenarios for China were presented by using the Integrated Policy Assessment Model of China. Technologies are the key component to reach a low carbon future. Technologies are identified with the scenario analysis. In order to realize the low carbon future, a technology roadmap was presented to reach the emission reduction up to 2050 in China. Twenty-eight key technologies are given in the paper for the technology roadmap, presenting learning curves. With full adoption of these key technologies, we do see ample opportunities for China to make the emission stable after 2020, without a large increase, and even start to have a deep reduction after 2030.

Peroxidase biocathodes for a biofuel cell development

Abstract: In terms of sustainable energy production, enzymatic biofuel cells are attractive for a number of special applications, such as disposable implantable power suppliers for medical sensor-transmitters and drug delivery/activator systems and self-powered enzyme-based biosensors; they offer practical advantages of using abundant organic raw materials as biofuels for clean and sustainable energy production. In this paper we discuss what power densities can be expected from enzymatic biofuel cells and what are the possibilities and limits for their optimization. As example, in this work, the designed hybrid biofuel cell formed by the battery type Zn anode and the biocathode, comprising horseradish peroxidase (HRP) immobilized on graphite and utilizing H2O2 as an oxidizer, is considered. The cell yields the open circuit voltage Voc of 1.68 and 1.57 V and the short-circuit current density isc of 800 μA cm−2 at pH 6 and 580 μA cm−2 at pH 7.45 in quiescent solutions. The biofuel cell operated at 1.5 V for 6 days; t...

Exergy analysis of particle dispersed latent heat thermal storage system for solar water heaters

Abstract: Phase change material (PCM) based latent heat thermal storage (LHTS) systems offer a challenging option to be employed as an effective energy storage and retrieval device if the energy source is intermittent and time dependent. However, the performance of LHTS systems is limited by the poor thermal conductivity of PCMs employed. The addition of high conductivity particles is proposed as one of the promising performance enhancement techniques for LHTS. In our study, an attempt is made to investigate the performance enhancement of a shell and tube storage unit applicable to solar water heaters due to the addition of high conductivity particles (copper) through exergy analysis. The enthalpy based two dimensional-transient equations are solved numerically for discharging process using FLUENT—a commercial computational fluid dynamics code. The numerical results show good agreement with experimental results available in the literature. The thermal behavior and performance of particle dispersed PCM unit in terms of exergy efficiency and total exergy recovered are compared with that of pure PCM unit. It is observed that the discharging time is reduced by around 28% by adding particles of volume fraction 0.1 and by around 85% with 0.6 volume fraction. However, the decrease in discharging time is not much appreciable beyond the particle volume fraction of 0.4. Similarly, the exergy efficiency and total exergy recovered are increased by 12% and 15%, respectively, with 0.1 volume fraction and by 50% and 60%, respectively, with 0.4 volume fraction. Different Reynolds numbers (i.e., Re=200–10 000) are considered in the numerical trials to investigate the influence of mass flow rate of heat transfer fluid (HTF) on the performance of the system. The results reveal that the role of HTF mass flow rate in increasing the overall thermal performance of LHTS unit is insignificant.

Electricity supply, irregularities, and the prospect for solar energy and energy sustainability in Sub-Saharan Africa

Abstract: Countries in Sub-Saharan Africa (SSA) are faced with the problem of expanding urban growth and demographic shift, necessitating the need to achieve a sustainable rate of positive economic growth. To move toward a sustainable future, many reforms have been implemented, including in the energy sector. Reforms in the energy sector will lead to a secure future energy supply, open globalised energy market, as well as providing basic energy needs. Unfortunately electrical energy production within SSA countries is primarily by wood fueled power stations and large hydroschemes (with oil and gas to a lesser extent). Large hydropower systems are environmentally destructive, and the combustion of wood generates millions of tons of carbon dioxide and green house gas emissions. The recent price fluctuations of crude oil and natural gas and the inconsistent and insufficient power supply have further increased public dissatisfaction. This paper demonstrates how the SSA region with its natural resources is capable of producing a stable electrical energy supply sector through renewable energy technologies (RETs), extending electricity supply to off-grid areas via photovoltaics (PV) and maintaining a continuous energy supply, with no significant impact on the environment and detriment to health of the local population. The most common characteristics of weak and unstable grids in SSA countries and their energy generation are investigated. Distributed generation technologies for rural electrifications (PV off-grid systems) as well as the grid-connected PVs are evaluated. This paper also demonstrates the possibility and merits of promoting specific RETs such as combined solar thermal energy systems for hospital equipment sterilization and powering solar air-conditioning systems in SSA countries, thus offsetting dependence on current power supply networks.

Quantum dot solar cell: Materials that produce two intermediate bands

Abstract: Placing intermediate bands within the energy gap of a semiconductor has been proposed as a way to increase solar cell efficiency. In this work, possible energy band configurations are determined, which achieve a theoretical efficiency greater than 70%. One way to create these bands is by utilizing quantum dot technology. Quantum dot materials and parameters are identified, which closely match the intermediate band energies that provide the maximum theoretical efficiency. The sensitivity of the efficiency as a function of the intermediate band energy levels is investigated. In addition, the minimum distances between the quantum dot materials required to prevent band overlap are determined.

Prediction of performance coefficients of a three-bucket Savonius rotor using artificial neural network

Abstract: This article deals with an artificial neural network analysis to predict the power and torque coefficients of a three-bucket Savonius rotor. The input data sets under different overlap conditions are taken from the experiments performed in a subsonic wind tunnel. Thirty input and output data sets are used. Out of these, 24 data sets are utilized for training and the remaining 6 are employed for testing analysis. The data sets are separated randomly. Three parameters, viz., the overlap ratio, the tip-speed ratio, and the angular velocity, are considered as input variables of the network. The power and torque coefficients are taken as output variables. The hidden layers are varied in the range from one to three. The quantities of neurons in the hidden layers are altered network-by-network for best matching. The back-propagation perceptron-learning algorithm which is commonly used is employed to train and test the networks. Eight network configurations are trained and tested simultaneously and the global errors between the experimental and neural network outputs are evaluated. From the investigation of the errors it is concluded that the two-hidden layer network provides the best matching for the power coefficient. However, the single hidden layer network provides better prediction of the torque coefficient.

Decentralized robust static synchronous compensator control for wind farms to augment dynamic transfer capability

Abstract: This paper presents an algorithm to design a decentralized robust controller for static synchronous compensators (STATCOMs) using minimax linear quadratic output-feedback control design approach. There is an increase in the available (dynamic) transfer capability of power systems with fixed-speed wind generators due to the designed decentralized controllers. The effects of the integration of various types of wind generators into power systems based on transfer limit have also been analyzed in this paper. The effectiveness of the suggested control strategy is validated by simulations on a benchmark two area power system. The performance of the designed controller is also compared to a conventional proportional-integral-based STATCOM controller. Simulation results show that both the dynamic voltage stability and the transient stability can be improved by using the robust STATCOM control proposed in this paper.

Dynamic modeling of photovoltaic module for real-time maximum power tracking

Abstract: Today’s society relies heavily on electric power produced mainly using coal and petroleum. These sources of energy are nonrenewable. The rise in the cost of petroleum and the effects of coal on the environment force the issue of seeking alternative sources of energy that are renewable and environmentally friendly. One such source is solar energy. Solar energy is extracted via photovoltaic (PV) modules. The problem with this alternative form of energy is the poor efficiency of solar cells. This work deals with the development of an improved dynamical model of PV modules to maximize the amount of power extracted from the Sun. The developed model has been implemented using MATLAB®/SIMULINK. Field data are used to compare the efficiency of the newly developed model to the existing models reported in the available literature. Results reveal that the proposed model led to an improvement of 21% in the efficiency of the PV module. Such improvement in efficiency will lead to great energy saving when used on a larg...

A comparative evaluation of Al2O3 coated low heat rejection diesel engine performance and emission characteristics using fuel as rice bran and pongamia methyl ester

Abstract: In this study, for the first time, a nanoceramic Al2O3 was used as a coating material in the low heat rejection engine concept Experiments were conducted on single cylinder, four stroke, water cooled, and direct injection diesel engine First, the engine was tested at different load conditions without coating Then, combustion chamber surfaces (cylinder head, cylinder liner, valves, and piston crown face) were coated with nanoceramic material of Al2O3 using plasma spray method Comparative evaluation on performance and emission characteristics using fuel as rice bran methyl ester, pongamia methyl ester, and biodiesel/diesel fuel mixtures was studied in the ceramic coated and uncoated engines under the same running conditions An increase in engine power and a decrease in specific fuel consumption, as well as significant improvements in exhaust gas emissions (except NOx) and smoke density, were observed in the ceramic coated engines compared with those of the uncoated engine

Another “Great Transformation”? Social and cultural consequences of climate change

Abstract: The dynamics of anthropogenic climate change is not merely a question of natural processes, but first and foremost, a question of economy, society, and culture. The humanities are therefore crucial to analyzing issues like migration, new risks because of extreme weather events, violent conflict, and the impact of global warming on political stability.

Performance and emission studies on biodiesel-liquefied petroleum gas dual fuel engine with exhaust gas recirculation

Abstract: Biodiesel is an alternative fuel to diesel derived from vegetable oils by transesterification process. It can be used in diesel engines with/without any modification in the engine system. Biodiesel engines emit slightly higher NOx emissions, as compared to that of diesel engines, as higher cylinder temperatures achieved during combustion. To reduce the NOx emissions a small percentage of exhaust gases recirculated into the cylinder in dual mode operation. For the improvement of power, liquefied petroleum gas (LPG) was supplied along with fresh air in dual mode operation. This article describes experimental investigation on performance and emission characteristics of single cylinder, indirect diesel engine fueled with biodiesel-diesel blend and LPG in dual fuel mode operation with exhaust gas recirculation (EGR). Recirculation of exhaust gases into the engine decreases the combustion chamber temperatures and marginal improvement in thermal efficiency was observed with EGR. However, reduction in air flow in...