Energies, Volume 5, Issue 3 (March 2012) – 19 articles , Pages 531-861

This article examines the inefficient use of resources in the Brazilian transportation system. The energy use growth and external cost generation in this essential economic sector are considerable, and the trend is towards an increasing problem in the coming years. The continued expansion of Brazilian cities and the increase in demand for mobility is a result of a substantial growth in the number of road transport users, as increased earnings enable lower income groups to acquire and use individual motorized means of transport. The aim of this paper is to estimate the potential gains from reducing individual motorized transport by the year 2020. This investigation concludes that in a conservationist scenario, by prioritizing low cost, low technology public policies—which include operation of Bus Rapid Transit systems, walking and cycling facilities and congestion charges, among others—it should be possible to save over USD 30 billion and USD 26 billion in external transportation and infrastructure costs, respectively, up to 2020. In addition, these public policies can save more than 35 million Tons of Oil Equivalents in energy consumption and avoid almost 4,000 thousand tons of local pollution emissions and 37,500 thousand tons of GHG emissions in the same period. Full article

To investigate the microphysics mechanism and the factors that influence arc development along a polluted surface, the arc was considered as a plasma fluid. Based on the image method and the collision ionization theory, the electric field of the arc needed to maintain movement with different degrees of pollution was calculated. According to the force of the charged particle in an arc plasma stressed under an electric field, a calculation model of arc velocity, which is dependent on the electric field of the arc head that incorporated the effects of airflow around the electrode and air resistance is presented. An experiment was carried out to measure the arc velocity, which was then compared with the calculated value. The results of the experiment indicated that the lighter the pollution is, the larger the electric field of the arc head and arc velocity is; when the pollution is heavy, the effect of thermal buoyancy that hinders arc movement increases, which greatly reduces the arc velocity. Full article

This paper presents a new Fuzzy Adaptive Modified Particle Swarm Optimization algorithm (FAMPSO) for the placement of Fuel Cell Power Plants (FCPPs) in distribution systems. FCPPs, as Distributed Generation (DG) units, can be considered as Combined sources of Heat, Power, and Hydrogen (CHPH). CHPH operation of FCPPs can improve overall system efficiency, as well as produce hydrogen which can be stored for the future use of FCPPs or can be sold for profit. The objective functions investigated are minimizing the operating costs of electrical energy generation of distribution substations and FCPPs, minimizing the voltage deviation and minimizing the total emission. In this regard, this paper just considers the placement of CHPH FCPPs while investment cost of devices is not considered. Considering the fact that the objectives are different, non-commensurable and nonlinear, it is difficult to solve the problem using conventional approaches that may optimize a single objective. Moreover, the placement of FCPPs in distribution systems is a mixed integer problem. Therefore, this paper uses the FAMPSO algorithm to overcome these problems. For solving the proposed multi-objective problem, this paper utilizes the Pareto Optimality idea to obtain a set of solution in the multi-objective problem instead of only one. Also, a fuzzy system is used to tune parameters of FAMPSO algorithm such as inertia weight. The efficacy of the proposed approach is validated on a 69-bus distribution system. Full article

A method for the prediction of Energy Production (EP) in Concentrating Photovoltaic (CPV) installations is examined in this study. It presents a new method that predicts EP by using Global Horizontal Irradiation (GHI) and the Photovoltaic Geographical Information System (PVGIS) database, instead of Direct Normal Irradiation (DNI) data, which are rarely recorded at most locations. EP at four Spanish CPV installations is analyzed: two are based on silicon solar cells and the other two on multi-junction III-V solar cells. The real EP is compared with the predicted EP. Two methods for EP prediction are presented. In the first preliminary method, a monthly Performance Ratio (PR) is used as an arbitrary constant value (75%) and an estimation of the DNI. The DNI estimation is obtained from GHI measurements and the PVGIS database. In the second method, a lineal model is proposed for the first time in this paper to obtain the predicted EP from the estimated DNI. This lineal model is the regression line that correlates the real monthly EP and the estimated DNI in 2009. This new method implies that the monthly PR is variable. Using the new method, the difference between the predicted and the real EP values is less than 2% for the annual EP and is in the range of 5.6%–16.1% for the monthly EP. The method that uses the variable monthly PR allows the prediction of the EP with reasonable accuracy. It is therefore possible to predict the CPV EP for any location, using only widely available GHI data and the PVGIS database. Full article

In order to study the flashover mechanism of polluted insulators under AC voltage, a new arc propagation criterion which is based on an arc root voltage gradient is proposed. This criterion can explain the variation of the arc root voltage gradient in the arc propagation process. Based on this criterion, a new distributed parameter electrical circuit flashover model of polluted insulators is presented. The arc channel is considered as an equivalent distributed parameter circuit model instead of using the arc voltage-gradient equation. The parameters of the arc model are obtained from the electromagnetic field distribution of the arc and the gas discharge theories. The arc root is considered as parallel paths including the polluted layer. The variation of the voltage on the arc root is related to the capability of arc propagation. This model takes the microscopic mechanism of arc root ionization into consideration, which can improve the accuracy of the flashover model. The results obtained from the presented model are in good agreement with other mathematical and experimental results. Full article

Bio-oil from fast pyrolysis of biomass is a low-grade liquid fuel, which can be upgraded through the emulsification with diesel oil. In this study, we prepared two rice husk bio-oil samples with different solid char contents and three bio-oil/diesel-oil emulsion samples with the bio-oil content of 10 wt%, 30 wt% and 50 wt%, respectively. The lubrication properties of these oil samples were evaluated by a four-ball tester. The morphologies of the worn ball surface were observed by scanning electron microscope (SEM). The chemical states of the elements on the worn surface and non-worn surface were analyzed by X-ray photoelectron spectroscope (XPS). The results showed that the bio-oil possessed better extreme-pressure, anti-wear and friction-reducing properties than the commercial diesel oil (number zero). The solid char particles in the bio-oil could improve its lubrication performance. Moreover, the lubrication ability of the emulsions would be enhanced with the increasing of the bio-oil content in the emulsions. Full article

Accurate prediction of algal biofuel yield will require empirical determination of physiological responses to the environment, particularly light and temperature. One strain of interest, Nannochloropsis salina, was subjected to ranges of light intensity (5–850 μmol m⁻² s⁻¹) and temperature (13–40 °C) and its exponential growth rate, total fatty acids (TFA) and fatty acid composition were measured. The maximum acclimated growth rate was 1.3 day⁻¹ at 23 °C and 250 μmol m⁻² s⁻¹. Fatty acids were detected by gas chromatography with flame ionization detection (GC-FID) after transesterification to corresponding fatty acid methyl esters (FAMEs). A sharp increase in TFA containing elevated palmitic acid (C16:0) and palmitoleic acid (C16:1) during exponential growth at high light was observed, indicating likely triacylglycerol accumulation due to photo-oxidative stress. Lower light resulted in increases in the relative abundance of unsaturated fatty acids; in thin cultures, increases were observed in palmitoleic and eicosapentaenoic acids (C20:5ω3). As cultures aged and the effective light intensity per cell converged to very low levels, fatty acid profiles became more similar and there was a notable increase of oleic acid (C18:1ω9). The amount of unsaturated fatty acids was inversely proportional to temperature, demonstrating physiological adaptations to increase membrane fluidity. These data will improve prediction of fatty acid characteristics and yields relevant to biofuel production. Full article

The Agence Nationale de la Recherche (ANR-EESI) ENERGY ReCOvery from Low Temperature heat sources (ENERCO_LT) project is a waste heat recovery project that aims to reduce energy consumption in industrial gas production sites, by producing electrical power from exothermic processes discharges at low and medium temperature. Two promising thermal sources, consisting of: (i) almost dry gas flow at 165 °C and (ii) moist gas flow at 150 °C with a dew point at 60 °C, were then investigated. In this paper, the challenge was to discern suitable recovery solutions facing resource specificities and their thermodynamic constraints, in order to minimize the overall exergy destruction, i.e., to move up the exergy efficiency of the entire system. In this spirit, different designs, including Organic Rankine Cycles (ORCs) and CO₂ transcritical cycles, operating as simple and cascade cycles, were investigated. Combined exergy analysis and pinch optimization was performed to identify the potential of various working fluids, by their properties, to overcome the global irreversibility according to the studied resource. Supercritical parameters of various working fluids are investigated too, and seem to bring promising results regarding system performances. Full article

The present study aims to develop a thermoeconomic-based approach for optimization of steam levels in a steam production and distribution system by use of the specific exergy costing (SPECO) method for determining optimum steam levels to minimize the cost caused by exergy destruction. In the field of total site optimization, incremental cost of the utility system caused by exergy destruction has been selected as an objective function and the result is compared with the case that energy minimization has been selected as the prime objective. The steam levels are optimized considering steam demand at each level, output power generated by turbines, boiler duty, fuel and cold utility requirements as well as capital cost of equipments. The analysis showed that thermoeconomic (exergoeconomic) approach in optimization not only can change the optimum structure of steam levels but also may reduce the total cost of utility system up to 8%. Full article

The effect of air density variations on the calibration constants of several models of anemometers has been analyzed. The analysis was based on a series of calibrations between March 2003 and February 2011. Results indicate a linear behavior of both calibration constants with the air density. The effect of changes in air density on the measured wind speed by an anemometer was also studied. The results suggest that there can be an important deviation of the measured wind speed with changes in air density from the one at which the anemometer was calibrated, and therefore the need to take this effect into account when calculating wind power estimations. Full article

This study developed a theoretical model for predicting the downstream temperatures of high pressure high temperature condensate gas flowing through chokes. The model is composed of three parts: the iso-enthalpy choke model derived from continuity equation and energy conservation equation; the liquid-vapor equilibrium model based on the SRK equation of state (EoS); and the enthalpy model based on the Lee-Kesler EoS. Pseudocritical properties of mixtures, which are obtained by mixing rules, are very important in the enthalpy model, so the Lee-Kesler, Plocker-Knapp, Wong-Sandler and Prausnitz-Gunn mixing rules were all researched, and the combination mixing rules with satisfactory accuracy for high pressure high temperature condensate gases were proposed. The temperature prediction model is valid for both the critical and subcritical flows through different kinds of choke valves. The applications show the model is reliable for predicting the downstream temperatures of condensate gases with upstream pressures up to 85.54 MPa and temperatures up to 93.23 °C. The average absolute errors between the measured and calculated temperatures are expected for less than 2 °C by using the model. Full article

The objective of this study is to investigate heating performance characteristics of a coolant source heat pump using the wasted heat from electric devices for an electric bus. The heat pump, using R-134a, is designed for heating a passengers’ compartment by using discharged energy from the coolant of electric devices, such as motors and inverters of the electric bus. The heating performance of the heat pump was tested by varying the operating parameters, such as outdoor temperature and volume flow rate of the coolant water of the electrical devices. Heating capacity, compressor work, and heating COP were measured; their behaviors with regard to the parameters were observed. Experimental results showed that heating COP increased with decrease of outdoor temperature, from 20.0 °C to 0 °C, and it observed to be 3.0 in the case of 0 °C outdoor temperature. The observed characteristics of the heating COP suggest that the heat pump is applicable as the cabin heater of an electric vehicle, which is limited by short driving range. Full article

Accurate wind power forecasts highly contribute to the integration of wind power into power systems. The focus of the present study is on large-scale offshore wind farms and the complexity of generating accurate probabilistic forecasts of wind power fluctuations at time-scales of a few minutes. Such complexity is addressed from three perspectives: (i) the modeling of a nonlinear and non-stationary stochastic process; (ii) the practical implementation of the model we proposed; (iii) the gap between working on synthetic data and real world observations. At time-scales of a few minutes, offshore fluctuations are characterized by highly volatile dynamics which are difficult to capture and predict. Due to the lack of adequate on-site meteorological observations to relate these dynamics to meteorological phenomena, we propose a general model formulation based on a statistical approach and historical wind power measurements only. We introduce an advanced Markov Chain Monte Carlo (MCMC) estimation method to account for the different features observed in an empirical time series of wind power: autocorrelation, heteroscedasticity and regime-switching. The model we propose is an extension of Markov-Switching Autoregressive (MSAR) models with Generalized AutoRegressive Conditional Heteroscedastic (GARCH) errors in each regime to cope with the heteroscedasticity. Then, we analyze the predictive power of our model on a one-step ahead exercise of time series sampled over 10 min intervals. Its performances are compared to state-of-the-art models and highlight the interest of including a GARCH specification for density forecasts. Full article

Many advanced vehicle technologies, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and fuel cell vehicles (FCVs), are gaining attention throughout the World due to their capability to improve fuel efficiencies and emissions. When evaluating the operational successes of these new fuel-efficient vehicles, it is essential to consider energy usage and greenhouse gas (GHG) emissions throughout the entire lifetimes of the vehicles, which are comprised of two independent cycles: a fuel cycle and a vehicle cycle. This paper intends to contribute to the assessment of the environmental impacts from the alternative technologies throughout the lifetimes of various advanced vehicles through objective comparisons. The methodology was applied to six commercial vehicles that are available in the U.S. and that have similar dimensions and performances. We also investigated the shifts in energy consumption and emissions through the use of electricity and drivers’ behavior regarding the frequencies of battery recharging for EVs and plug-in hybrid electric vehicles (PHEVs). This study thus gives insight into the impacts of the electricity grid on the total energy cycle of a vehicle lifetime. In addition, the total ownership costs of the selected vehicles were examined, including considerations of the fluctuating gasoline prices. The cost analysis provides a resource for drivers to identify optimal choices for their driving circumstances. Full article

This article reports our novel idea about the thermal stimulation of seabed hydrate reservoirs for the purpose of natural gas production. Our idea is to use submarine heat pumps, which are to be placed near the hydrate reservoir and work to recover thermal energy from the surrounding seawater and supply it into the reservoir. Although the heat pumps need an electricity supply from the sea surface level, they can provide thermal energy which is several times that of the consumed electricity in quantity. As a consequence, the use of submarine heat pumps has a distinct thermodynamic advantage over other thermal stimulation techniques already proposed in the literature. Full article

In this paper, petroleum product (mainly petrol and diesel) consumption in the transportation sector of China is analyzed. This was based on the Bayesian linear regression theory and Markov Chain Monte Carlo method (MCMC), establishing a demand-forecast model of petrol and diesel consumption introduced into the analytical framework with explanatory variables of urbanization level, per capita GDP, turnover of passengers (freight) in aggregate (TPA, TFA), and civilian vehicle number (CVN) and explained variables of petrol and diesel consumption. Furthermore, we forecast the future consumer demand for oil products during “The 12th Five Year Plan” (2011–2015) based on the historical data covering from 1985 to 2009, finding that urbanization is the most sensitive factor, with a strong marginal effect on petrol and diesel consumption in this sector. From the viewpoint of prediction interval value, urbanization expresses the lower limit of the predicted results, and CVN the upper limit of the predicted results. Predicted value from other independent variables is in the range of predicted values which display a validation range and reference standard being much more credible for policy makers. Finally, a comparison between the predicted results from autoregressive integrated moving average models (ARIMA) and others is made to assess our task. Full article

Optimization of three parameters: agitation rate (A; 100, 200 and 300 rpm), aeration rate (B; 0.5, 1.5 and 2.5 vvm) and aeration timing (C; 2, 4 and 6 h), for ethanol production from sweet sorghum juice under very high gravity (VHG, 290 g L⁻¹ of total sugar) conditions by Saccharomyces cerevisiae NP 01 was attempted using an L₉ (3⁴) orthogonal array design. The fermentation was carried out at 30 °C in a 2-L bioreactor and the initial yeast cell concentration was approximately 2 × 10⁷ cells mL⁻¹. The results showed that the optimum condition for ethanol fermentation should be A₂B₃C₂ corresponding to agitation rate, 200 rpm; aeration rate, 2.5 vvm and aeration timing, 4 h. The verification experiments under the optimum condition clearly indicated that the aeration and agitation strategies improved ethanol production. The ethanol concentration (P), productivity (Q_p) and ethanol yield (Y_p/s) were 132.82 ± 1.06 g L⁻¹, 2.55 ± 0.00 g L⁻¹h⁻¹ and 0.50 ± 0.00, respectively. Under the same condition without aeration (agitation rate at 200 rpm), P and Q_p were only 118.02 ± 1.19 g L⁻¹ and 2.19 ± 0.04 g L⁻¹h⁻¹, respectively while Y_p/s was not different from that under the optimum condition. Full article

Solar energy has become an important energy source in recent years as it generates less pollution than other energies. A photovoltaic (PV) system, which typically has many components, converts solar energy into electrical energy. With the development of advanced engineering technologies, the transfer efficiency of a PV system has been increased from low to high. The combination of components in a PV system influences its transfer efficiency. Therefore, when predicting the transfer efficiency of a PV system, one must consider the relationship among system components. This work accurately predicts whether transfer efficiency of a PV system is high or low using a novel hybrid model that combines rough set theory (RST), data envelopment analysis (DEA), and genetic programming (GP). Finally, real data-set are utilized to demonstrate the accuracy of the proposed method. Full article

Low-carbon future has in recent years recurred as a strategic element in energy and climate planning. The transition towards a low-carbon society requires fundamental changes in both the energy systems and in the ways that society adapts to large transformations. These changes cannot happen by themselves, but require purposeful mechanisms and measures steered by government and other actors in society. Actions are required at all levels of government from international to local. Thailand needs to transform its energy system to effectively address concerns about a range of environmental problems. This paper provides an analysis of Thailand’s carbon governance structure as applied to the energy systems. The study applies a multi-level governance framework to understand the policy environment. It presents the elements of existing energy and climate governance and an examination of modeling exercises of the existing literature. It is concluded that multi-level governance enables integration of divergent perspectives and helps steer the course of responsible development. The paper also provides some recommendations on issues related to the governance challenges. Full article