Performance analysis of a hypothetical 1-hectare PV plant in the Benguela region. The first year of operation.

The presents study evaluates the performance of a hypothetical 1-hectare solar photovoltaic (PV) plant located in the Baía Azul Beach, in Benguela, Angola. The first year performance of the plant composed by 2,784 DuoMax 365 PV modules from Trina Solar Company was evaluated by means of the VelaSolaris Polysum software package. The total surface area of the PV modules was of 5,456.64 m2. The annual alternate current electricity production was of 1,511.70 MWh allowing a total of 710.47 tCO2 of CO2 emissions reduction and a performance ratio of 72.8 %. The annual average energy and exergy efficiencies of the PV system were respectively of of 14.3 % and 14.7 %.

Performance Analysis of a Hypothetical 1-Hectare PV Plant in the Benguela Region. The First Year of Operation.

The presents study evaluates the performance of a hypothetical 1-hectare solar photovoltaic (PV) plant located in the Baía Azul Beach, in Benguela, Angola. The first year performance of the plant composed by 2,784 DuoMax 365 PV modules from Trina Solar Company was evaluated by means of the VelaSolaris Polysum software package. The total surface area of the PV modules was of 5,456.64 m2. The annual alternate current electricity production was of 1,511.70 MWh allowing a total of 710.47 tCO2 of CO2 emissions reduction and a performance ratio of 72.8 %. The annual average energy and exergy efficiencies of the PV system were respectively of of 14.3 % and 14.7 %.

Acidity Reduction of Bio-Oil by Methylic Esterification Reactions

An alternative to fossil fuels is the use of triglyceride biomass for conversion to biofuel by the thermal cracking process, also known as pyrolysis. The liquid phase, called bio-oil, has physicochemical properties like petroleum-derived fuels. One of the undesirable characteristics of bio-oil is the high acidity index, due to the presence of short-chain carboxylic acids in its composition. This feature makes refining and use inviable. The objective of this work was to perform esterification reactions using bio-oil, produced from soybean oil pyrolysis already characterized, in order to reduce its acidity index. Besides that, the esterified bio-oil was submitted to different washing experiments to decrease even more the final acidity. For the esterification reaction 25 g of bio-oil was used at a temperature of 64 °C, using from 0.8 to 2.2% sulfuric acid and 0.5 to 99.5% mass ratio of methyl alcohol and bio-oil. The highest acidity index reduction after 20 min was 81.2%, the esterified bio-oil reduced from 129 to 32.4 mg KOH g-1. Esterification reaction followed by washing and neutralization can decrease even more those values and, the acidity index can reach zero.

Enhanced Oil Recovery: Projects Planning Strategy in Angolan Oilfields

Hydrocarbon exploration in Angola commenced in 1910 with its first oil recovered in 1955. The proven reserves in Angola are estimated to reach up to 13 billion barrels (2.1 billion m3). Most of the Angolan oil fields are mature or maturing and some are or may be abandoned due to unprofitable recovery limit beyond the conventional type of oil production. The oil recovery is mainly by primary and secondary recovery methods. Apart from the issue of maturity, there is increasing energy demand due to population growth and difficulties in discovering and developing new fields as alternatives to the current oil fields. For incremental and sustained production rate of these fields and in addition to instability of oil prices and concerns about future oil supply, Angola has started to work towards developing affordable and efficient technologies capable of recovering residual oil in reservoirs as well as extend the life of many current fields which can be achieved through the implementation of enhanced oil recovery (EOR). Therefore, this paper discusses the EOR planning strategy from project selection, project implementation and optimization, and field abandonment. It further highlights the mutual benefits that may be derived from a cross-collaboration between the government and other stakeholders in Angola.

Morphological and elemental analyses of supported palladium (Pd)/silver (Ag) composite membranes

Supported palladium (Pd)/silver (Ag) composite membranes have been investigated for hydrogen separation mainly in order to avoid hydrogen embrittlement, improve hydrogen permeance and reduce membrane cost. The electroless method is recommended for the co-plating of Pd and Ag on a substrate surface. However, Ag precursor has a higher redox potential than Pd and, thus, Ag is preferentially deposited, which compromises the membrane selectivity to hydrogen. Here we investigated the morphology and elemental composition of supported palladium (Pd)/silver (Ag) composite membranes produced by different methods. The first membrane was produced from a plating solution of 80 wt% of Pd and 20 wt% of Ag. The membrane surface presented several large dendritic crystals that not grown in a direction to form a dense metallic film. According to EDS results, the membrane surface presented similar Pd and Ag composition, which confirms the preferential Ag deposition. At room temperature, this membrane presented a nitrogen flux of 0.35 mol m-2 s-1 at 200 kPa of transmembrane pressure. Thus, the formed membrane is not suitable for hydrogen separation. The second membrane was formed by adding small amounts of Ag to the plating solution during the electroless process. The final plating solution contained 75 wt% of Pd and 25 w% of Ag. The membrane thickness was 2 µm, but the membrane morphology was not totally dense. According to EDS results, the Ag composition was greater than the Pd composition, especially at the membrane top surface. This membrane also presented high nitrogen permeance probably due to the holes formed on the membrane surface. Thus, although the controlled addition of Ag is recommended to form dense membranes, the Ag was preferentially deposited over the Pd when starting with the highest rate of Ag addition. Adding lower Ag rates at the beginning could be helpful to avoid the preferential Ag deposition.

Evaluation of Gas Composition Obtained from Gasification of Pellets and Blends with Agricultural Wastes

The gas produced by gasification is more versatile than the original solid biomass and can be applied as raw material for chemical industry and as fuel for the electrical and thermal energy production. Small gasification plants are being considered as an option for electrical energy generation in remote areas where agriculture wastes can be found easily. In this way, the aim of this work was to evaluate the characteristics of the gas composition of co-gasification using pine pellets and blends with agricultural wastes. The experiments were carried out in duplicate in a pilot scale fixed bed downdraft gasifier, GEK Power Pallet 20kW. It was performed experimental runs with 100 % pine pellets, 80 % pine pellets and 20 % agriculture wastes, and 80 % pine pellets with 15.4 % agriculture wastes and 4.6 % of glycerol used as an agglutinant agent. The samples were analyzed by GC-FID/TCD. The moisture of different feedstocks varied between 8.00 and 10.88. The results of the produced gas show an average composition of 37.45% CO and 15.79% H2, and LHV 7,155 kJ/kg for gasification of 100 % pine pellets. While the mixture of pine pellets and agriculture wastes resulted in a gas with 32.13% CO and 20.10% H2, and LHV of 6,663.4 kJ/kg. When added glycerol, the gas composition to CO was 20.52 % and to H2 11.21 % with LHV of 4,507.4 kJ/kg. The results indicate that the gasifier is compatible with the mixture of agricultural residues and pines pellets in co-gasification.

Enhanced oil recovery: Projects planning strategy in Angolan oilfields

Hydrocarbon exploration in Angola commenced in 1910 with its first oil recovered in 1955. The proven reserves in Angola are estimated to reach up to 13 billion barrels (2.1 billion m3). Most of the Angolan oil fields are mature or maturing and some are or may be abandoned due to unprofitable recovery limit beyond the conventional type of oil production. The oil recovery is mainly by primary and secondary recovery methods. Apart from the issue of maturity, there is increasing energy demand due to population growth and difficulties in discovering and developing new fields as alternatives to the current oil fields. For incremental and sustained production rate of these fields and in addition to instability of oil prices and concerns about future oil supply, Angola has started to work towards developing affordable and efficient technologies capable of recovering residual oil in reservoirs as well as extend the life of many current fields which can be achieved through the implementation of enhanced oil recovery (EOR). Therefore, this paper discusses the EOR planning strategy from project selection, project implementation and optimization, and field abandonment. It further highlights the mutual benefits that may be derived from a cross-collaboration between the government and other stakeholders in Angola.

Morphological and Elemental Analyses of Supported Palladium (Pd)/Silver (Ag) Composite Membranes

Supported palladium (Pd)/silver (Ag) composite membranes have been investigated for hydrogen separation mainly in order to avoid hydrogen embrittlement, improve hydrogen permeance and reduce membrane cost. The electroless method is recommended for the co-plating of Pd and Ag on a substrate surface. However, Ag precursor has a higher redox potential than Pd and, thus, Ag is preferentially deposited, which compromises the membrane selectivity to hydrogen. Here we investigated the morphology and elemental composition of supported palladium (Pd)/silver (Ag) composite membranes produced by different methods. The first membrane was produced from a plating solution of 80 wt% of Pd and 20 wt% of Ag. The membrane surface presented several large dendritic crystals that not grown in a direction to form a dense metallic film. According to EDS results, the membrane surface presented similar Pd and Ag composition, which confirms the preferential Ag deposition. At room temperature, this membrane presented a nitrogen flux of 0.35 mol m-2 s-1 at 200 kPa of transmembrane pressure. Thus, the formed membrane is not suitable for hydrogen separation. The second membrane was formed by adding small amounts of Ag to the plating solution during the electroless process. The final plating solution contained 75 wt% of Pd and 25 w% of Ag. The membrane thickness was 2 µm, but the membrane morphology was not totally dense. According to EDS results, the Ag composition was greater than the Pd composition, especially at the membrane top surface. This membrane also presented high nitrogen permeance probably due to the holes formed on the membrane surface. Thus, although the controlled addition of Ag is recommended to form dense membranes, the Ag was preferentially deposited over the Pd when starting with the highest rate of Ag addition. Adding lower Ag rates at the beginning could be helpful to avoid the preferential Ag deposition.

Evaluation of Gas Composition Obtained from Gasification of Pellets and Blends with Agricultural Wastes

The gas produced by gasification is more versatile than the original solid biomass and can be applied as raw material for chemical industry and as fuel for the electrical and thermal energy production. Small gasification plants are being considered as an option for electrical energy generation in remote areas where agriculture wastes can be found easily. In this way, the aim of this work was to evaluate the characteristics of the gas composition of co-gasification using pine pellets and blends with agricultural wastes. The experiments were carried out in duplicate in a pilot scale fixed bed downdraft gasifier, GEK Power Pallet 20kW. It was performed experimental runs with 100 % pine pellets, 80 % pine pellets and 20 % agriculture wastes, and 80 % pine pellets with 15.4 % agriculture wastes and 4.6 % of glycerol used as an agglutinant agent. The samples were analyzed by GC-FID/TCD. The moisture of different feedstocks varied between 8.00 and 10.88. The results of the produced gas show an average composition of 37.45% CO and 15.79% H2, and LHV 7,155 kJ/kg for gasification of 100 % pine pellets. While the mixture of pine pellets and agriculture wastes resulted in a gas with 32.13% CO and 20.10% H2, and LHV of 6,663.4 kJ/kg. When added glycerol, the gas composition to CO was 20.52 % and to H2 11.21 % with LHV of 4,507.4 kJ/kg. The results indicate that the gasifier is compatible with the mixture of agricultural residues and pines pellets in co-gasification.

Effects of the simplification in the geometry of a cyclone test facility on the swirling flow: a CFD study

A study about the influence of geometry simplification on the swirling flow of a cyclone was performed by comparing CFD results with experimental data. The numerical results were obtained by solving the mass and momentum equations with the Reynolds Stress Model (RSM) for the turbulence closure. On other hand, the experimental data were obtained in the literature, the authors used the Particle Image Velocimetry (PIV) technique to measure the velocity fields and a differential manometer to measure the pressure drop. In this work, different test facility geometries configurations were simulated: the complete test facility; and others with some simplifications downstream and upstream of the cyclone. The boundary condition for both numerical and experimental analysis was performed with inlet velocity in 10.5 and 12.25 m/s. Results showed a decrease in the gas vortex velocity in the cyclone center when simplifications in the test facility geometry are made. These bring significant consequences in the performance parameters, like almost 20% in the pressure drop values.