Monitoring absolute vertical land motions and absolute sea-level changes from GPS and tide gauges data over French Polynesia

In this study,we estimate the absolute vertical land motions at three tidal stations with collocated Global Navigation Satellite System(GNSS)receivers over French Polynesia during the period 2007-2020,and obtain,as ancillary results,estimates of the absolute changes in sea level at the same locations.To verify our processing approach to determining vertical motion,we first modeled vertical motion at the International GNSS Service(IGS)THTI station located in the capital island of Tahiti and compared our estimate with previous independent determinations,with a good agreement.We obtained the following estimates for the vertical land motions at the tide gauges:Tubuai island,Austral Archipelago-0.92±0.17 mm/yr,Vairao village,Tahiti Iti:-0.49±0.39 mm/yr,Rikitea,Gambier Archipelago-0.43±0.17 mm/yr.The absolute variations of the sea level are:Tubuai island,Austral Archipelago 5.25±0.60 mm/yr,Vairao village,Tahiti Iti:3.62±0.52 mm/yr,Rikitea,Gambier Archipelago 1.52±0.23 mm/yr.We discuss these absolute values in light of the values obtained from altimetric measurements and other means in French Polynesia.

Performance Evaluation of Novel Eco-Materials Composed of Millet Husks, Rice Husks, and Polystyrene

Managing agricultural waste and expanded polystyrene (EPS) poses significant environmental and economic challenges. This study aims to create composites from millet husks, rice husks, and recycled EPS, using a manufacturing method that involves dissolving the polystyrene in a solvent followed by cold pressing. Various particle sizes and two binder dosages were investigated to assess their influence on the physico-mechanical properties of the composites. The mechanical properties obtained range from 2.54 to 4.47 MPa for the Modulus of Rupture (MOR) and from 686 to 1400 MPa for the Modulus of Elasticity in Bending (MOE). The results indicate that these composites have potential for applications in the construction sector, particularly for wood structures and interior decoration. Moreover, surface treatments could enhance their durability and mechanical properties. This research contributes to the valorization of agricultural and plastic waste as eco-friendly and economical construction materials.

Development and Characterization of Particle Boards Based on Sorghum Husk

This study tackles current environmental challenges by developing innovative and eco-friendly particle boards utilizing sorghum husk, combined with recycled expanded polystyrene (EPS). This dual eco-responsible approach valorizes sorghum husk, often deemed agricultural waste, and repurposes EPS, a plastic waste, thus contributing to CO2 emission reduction and effective waste management. The manufacturing process involves dissolving recycled polystyrene within a solvent to create a binder, which is then mixed with sorghum husk and cold-pressed into composite boards. The study explores the impact of two particle sizes (fine and coarse) and two different concentrations of the recycled EPS binder. Results demonstrate significant variations in the boards’ mechanical properties, displaying a range of Modulus of Rupture (MOR) from 0.84 MPa to 3.85 MPa, and Modulus of Elasticity (MOE) spanning from 658.13 MPa to 1313.25 MPa, influenced by the binder concentration and particle size. These characteristics suggest that the boards can be effectively used in various construction applications, including interior decoration, false ceilings, and potentially for furniture and door manufacturing when combined with appropriate coatings. This study not only exemplifies the valorization of plastic and agricultural wastes but also offers a practical, localized solution to global climate change challenges by promoting sustainable construction materials.

Design Optimization of a Lattice Tower: Structure and Foundations

Produced in power plants, electrical energy is transported to places of consumption via the electricity network. At the heart of this network are the supports that allow electricity to be efficiently transported over long distances, guaranteeing the security and supply of energy to the various centers of use. In the construction of a line, supports occupy an important part in terms of safety and construction cost. It is therefore essential to optimize their use to reduce the cost of transmission lines. This work addresses this problem, which focuses on the optimal utilization of X-lattice towers in the construction of overhead power lines. The challenge is to reconcile the search for optimal cost and respect for the design, resistance and service constraints of the structure. To do this, a parameter having a strong correlation with the weight, foundation and construction cost of the X-lattice tower for 161 kV lines is determined as an important cost variable. This parameter is the wheelbase of the towers. The junction point between the structure and the foundations is obtained by measuring the forces at the base of the tower following the lowering of the loads. These efforts make it possible to size foundations which are of the inverted or isolated sole type. The results obtained reveal that from 8 meters in width, the wheelbase gradually changes until the optimum is obtained at 6.29 meters. With this wheelbase, the production cost is optimal. It clearly emerges from this study that the construction of lattice pylons with a wheelbase of approximately 6.29 meters makes it possible to optimize the cost of construction of 161 kV lines in the Republic of Benin.

Comparative Study of Solar PV Power Plant Dimensionnement Connected to Network Based on Monofacial and Bifacial Modules

This article presents the results of comparative study of two PV solar modules technologies,namely monofacial and bifacial.This study main objective is to identify conditions and parameters that make it possible to obtain better energy and economic efficiency from one or other of two technologies.The study reason lies in revival observed on bifacial module in recent years where all the major manufacturers of PV solar panels are developing them where in a few years,this technology risks being at the same price as the monofacial solar panel with better efficiency.Economic indicator used is energy levelized cost(LCOE)which is function technology type,energy productivity,annual investment and operation cost.To achieve this,a 3.685 MWc solar PV power plant was dimensioned and simulated under Matlab for a 3.5 ha site with a 2,320,740,602 FCFA budget for monofacial installation,against 1,925,188,640 FCFA for 2.73 MWc bifacial installation.The LCOE comparative analysis of two technologies calculated over a period of 25 years,showed that plant with bifacial panels is more beneficial if bifacial gain is greater than 9%.It has further been found that it is possible to gain up to 40%of invested cost if bifacial gain reaches 45%.Finally,a loss of about 10%of invested cost could be recorded if bifacial gain is less than 9%.

Study of Rice Husks and Expanded Polystyrene Composites for Construction Applications

In the current context of environmental challenges, this study focuses on developing innovative and eco-friendly composites using rice husk and recycled expanded polystyrene. This dual-responsibility approach valorizes a by-product like rice husk, often considered waste, and reuses polystyrene, a plastic waste, thereby contributing to CO2 emission reduction and effective waste management. The manufacturing process involves dissolving recycled polystyrene into a solvent to create a binder, which is then mixed with rice husk and cold-compacted into composite materials. The study examines the impact of two particle sizes (fine and coarse) and different proportions of recycled polystyrene binder. The results show significant variations in the mechanical characteristics of the composites, with Modulus of Rupture (MOR) values varying from 2.41 to 3.47 MPa, Modulus of Elasticity (MOE) ranging from 223.41 to 1497.2 MPa, and Stiffness Coefficient (K) from 5.04 to 33.96 N/mm. These characteristics demonstrate that these composites are appropriate for various construction applications, including interior decoration, panel claddings, and potentially for furniture and door manufacturing when combined with appropriate coatings. This study not only highlights the recycling of agricultural and plastic waste but also provides a localized approach to addressing global climate change challenges through the adoption of sustainable building materials.

Numerical Modeling and Technico-Economic Analysis of a Hybrid Energy Production System for Self-Consumption: Case of Rural Area in the Comoros

This study aims to provide electricity to a remote village in the Union of Comoros that has been affected by energy problems for over 40 years. The study uses a 50 kW diesel generator, a 10 kW wind turbine, 1500 kW photovoltaic solar panels, a converter, and storage batteries as the proposed sources. The main objective of this study is to conduct a detailed analysis and optimization of a hybrid diesel and renewable energy system to meet the electricity demand of a remote area village of 800 to 1500 inhabitants located in the north of Ngazidja Island in Comoros. The study uses the Hybrid Optimization Model for Electric Renewable (HOMER) Pro to conduct simulations and optimize the analysis using meteorological data from Comoros. The results show that hybrid combination is more profitable in terms of margin on economic cost with a less expensive investment. With a diesel cost of $1/L, an average wind speed of 5.09 m/s and a solar irradiation value of 6.14 kWh/m2/day, the system works well with a proportion of renewable energy production of 99.44% with an emission quantity of 1311.407 kg/year. 99.2% of the production comes from renewable sources with an estimated energy surplus of 2,125,344 kWh/year with the cost of electricity (COE) estimated at $0.18/kWh, presenting a cost-effective alternative compared to current market rates. These results present better optimization of the used hybrid energy system, satisfying energy demand and reducing the environmental impact.

Physico-Mechanical Characteristics of Earth Bricks Stabilized with Cement and Padouk Sawdust Residues

The objective of this work is to improve the physical and mechanical properties of stabilized earth blocks (BTC) used in construction in the Ndé department of Cameroon. To achieve this, two stabilizers, cement and sawdust, were used at varying percentages of 0%, 4%, 6%, and 8%. Physical characterization tests, including natural water content, specific weight, jar test, Protor, and Atterberg limits, were conducted. Additionally, mechanical tests, such as compression and three-point bending, were performed. The results show that as the amount of stabilizer increases, the density of BTC decreases. The samples with 8% sawdust have the highest density, while those without stabilizers have the lowest. Porosity decreases as sawdust and cement content increases, with smaller values observed in samples with 8% sawdust or cement. Our tests indicate that blocks stabilized with cement have slightly higher compressive strength than those stabilized with sawdust. However, the water absorption rate increases with higher sawdust content.

Analysis of CO_2 utilization into synthesis gas based on solar thermochemical CH_4-reforming

In this study, the solar thermochemical reactor performance for CO_2 utilization into synthesis gas(H_2+ CO) based on CH_4 reforming process was investigated in the context of carbon capture and utilization(CCU) technologies. The P1 radiation heat transfer model is adopted to establish the heat and mass transfer model coupled with thermochemical reaction kinetics. The reactor thermal behavior with direct heat transfer between gaseous reactant and products evolution and the effects of different structural parameters were evaluated. It was found that the reactor has the potential to utilize by ～60% of CO_2 captured with 40% of CH_4 co-fed into syngas(72.9% of H_2 and 27.1% of CO) at 741.31 k W/mof incident radiation heat flux. However, the solar irradiance heat flux and temperature distribution were found to significantly affect the reactant species conversion efficiency and syngas production. The chemical reaction is mainly driven by the thermal energy and higher species conversion into syngas was observed when the temperature distribution at the inner cavity of the reactor was more uniform. Designed a solar thermochemical reactor able to volumetric store concentrated irradiance could highly improve CCU technologies for producing energy-rich chemicals. Besides, the mixture gas inlet velocity, operating pressure and CO_2/CH_4 feeding ratio were crucial to determining the efficiency of CO_2 utilization to solar fuels. Catalytic CO_2-reforming of CH_4 to chemical energy is a promising strategy for an efficient utilization of CO_2 as a renewable carbon source.

Design of a Hybrid System for Rural Area Electricity Supply in Comoros

Comoros Islands suffering from energy stress due to rolling power cuts in the country mainly due to problems with failures heat engines fuelled with diesel. These blackouts induce shortages of energy while demand for energy does not cease to grow with the population. An alternative way for the Comoros Islands to get out of this energy crisis is to exploit the existing energy renewable sources, in particular to invest in the hybrid energy, a promising technology in terms of economic efficiency. The north of Ngazidja Island, in the region of Mitsamiouli, is considered among the economic lungs of this Island. It is spread in the field of tourism but also an area developed in agriculture and fishing. The Village of Koua Mitsamiouli located in rural area of this region is well known for its efficient yield in agricultural production, although the latter suffers from an energy stress in its last years. This lack of energy and water permanently to farmers has caused its production capacity to fall. In order to increase its agricultural profitability, and to satisfy the needs of the population for their activities such as trade, health, education, banking transactions, product preserving in retail stores, the energy autonomy of this village is more than necessary. It is important to notice that, the use of renewable energies in Comoros is very limited by photovoltaic (PV) solar panels. Hybrid technology and other renewable energy sources are not yet developed in Comoros Island. The main objective of this work is to propose the best possible sizing of a hybrid system for the production of electricity from renewable and non-renewable energy resources in order to satisfy the electrical needs in a reliable manner of the remote of village, Koua Mitsamiouli, for energetic autonomy. Indeed, two energy resources, composed by solar photovoltaic (PV) system and diesel generator are considered in the hybrid system. This study estimates the community demand with HOMER analysis. In order to check the performance of the overall system combination photovoltaic (PV)/generator, several numerical simulations were performed with the HOMER software using data from the national meteorological agency in Comoros and the results obtained by authors are satisfactory in terms of cost and reliability of the system.

A Comparative Study of the Phase Distribution in Carbon-Silica Hybrid Fillers for Rubber Obtained by Different Methods

Different types of carbon-silica fillers were prepared via pyrolysis-cum-water vapor of waste green tires tread and impregnation method. Dual phase fillers have been characterized by energy dispersive X-ray (EDX) spectroscopy in a scanning transmission electron microscope (STEM) or STEM-EDX. Phase distribution in hybrid fillers for rubber was investigated. The results achieved show that the conditions of obtaining influence the distribution and the location of the phases in the carbon-silica hybrid fillers as well as their most essential characteristics including specific area, oil absorption number, iodine adsorption number, ash content and others.

Combination of Tsoft and ET34-ANA-V80 software for the preprocessing and analysis of tide gauge data in French Polynesia

Since 2008 a network of five sea-level monitoring stations was progressively installed in French Polynesia.The stations are autonomous and data,collected at a sampling rate of 1 or 2 min,are not only recorded locally,but also transferred in real time by a radio-link to the NOAA through the GOES satellite.The new ET34-ANA-V80 version of ETERNA,initially developed for Earth Tides analysis,is now able to analyze ocean tides records.Through a two-step validation scheme,we took advantage of the flexibility of this new version,operated in conjunction with the preprocessing facilities of the Tsoft software,to recover co rrected data series able to model sea-level variations after elimination of the ocean tides signal.We performed the tidal analysis of the tide gauge data with the highest possible selectivity(optimal wave grouping)and a maximum of additional terms(shallow water constituents).Our goal was to provide corrected data series and modelled ocean tides signal to compute tide-free sea-level variations as well as tidal prediction models with centimeter precision.We also present in this study the characteristics of the ocean tides in French Polynesia and preliminary results concerning the non-tidal variations of the sea level concerning the tide gauge setting.

PV-Wind-Diesel System for Energy Supply on Remote Area Applied for Telecommunication Towers in Comoros

The Comoros is an archipelago in the Indian Ocean located in the Mozambique Channel between the African continent and Madagascar. Geographically Comoros is composed of four islands: Grande Comores, Anjouan, Mohéli and Mayotte (under French administration). Apart from Mayotte, the others three independent islands commonly known as the Union of the Comoros are suffering from energy stress since their independence year 1975 until nowadays. The energy supplied and distributed by the national electricity company, SONELEC produced by diesel engines, is not stable with so much load shedding all the time. This instability energy leads to a lack of a phone network in some telecommunications towers connected to grid. The majority of telecommunications towers are located in rural areas not connected to grid and running on diesel generators, which once again leads to a problem with the telecommunications network when diesel engines fail. The two competing companies which operate in the field of telecommunications in the Comoros, namely Comores Télécom, a national public company and Telma, the private one, are still unable to ensure the provision of the telecommunications network on a regular basis. This is why we propose in the present work, a sizing of hybrid system composed essentially of a diesel generator, a wind turbine and a photovoltaic solar system with storage in batteries for supplying telecommunications towers in order to permanently ensure the provision of the telecommunications network for the well-being of the population. Our future energy must be based on non-polluting energies with significant resources. Renewable energies are the best candidates but with intermittent production especially in rural areas not connected to the national electricity grid whose energy demand is more important to meet the needs of the population. The aim of this work is the sizing of a hybrid system composed of a diesel generator, a wind turbine and a photovoltaic solar system with storage in batteries for supplying telecommunications towers located in rural areas in the Comoros. In fact, to verify the performance of the hybrid system, a numerical study has been carried out with the HOMER 2.68 Beta software using meteorological data from the Comoros. The results obtained show that this hybrid combination is more profitable in the margin of economic cost and environmental assessments with a less expensive investment. These results also show a better optimization of Wind/PV/Battery of the hybrid system used, satisfying the demand and contributing to the preservation of the environment to fight against climate change with a low cost of energy.

The influence of pressure waves in tidal gravity records

For the reduction of atmospheric effects,observed gravity has initially been corrected by using the computed barometric admittance k of the in situ measured pressure,expressed in nms-2/hPa units and estimated by least squares method.However,the local pressure changes alone cannot account for the atmospheric mass attraction and loading when the coherent pressure field exceeds a specific size,i.e.,with increasing periodicities.To overcome this difficulty,it is necessary to compute the total atmospheric effect at each station using the global pressure field.However,the direct subtraction of the total gravity effect,provided by the models of pressure correction,is not yet satisfactory for S2 and other tidal components,such as K2 and P1,which include solar heating pressure tides.This paper identifies the origin of the problem and presents strategies to obtain a satisfactory solution.First,we set up a difference vector between the tidal factors of M2 and S2 after correction of the pressure and ocean tides effects.This vector,hereafter denoted as RES,presents the advantage of being practically insensitive to calibration errors.The minimum discrepancy between the tidal parameters of M2 and S2 corresponds to the minimum of the RES vector norm d.Secondly we adopt the hybrid pressure correction method,separating the local and the global pressure contribution of the models and replacing the local contribution by the pressure measured at the station multiplied by an admittance kATM.We tested this procedure on 8 stations from the IGETS superconducting gravimeters network(former GGP network).For stations at an altitude lower than 1000 m,the value of dopt is always smaller than0.0005.The discrepancy between the tidal parameters of the M2 and S2 waves is always lower than0.05% on the amplitude factors and 0.025° on the phases.For these stations,a correlation exists between the altitude and the value kopt.The results at the three Central European stations Conrad,Pecny and Vienna are in excellent agreement(0.05%) with the DDW99NH model for all the main tidal waves.

Indoor Nitrogen Oxides Occurrence, Modeling and Prediction

Outdoor air quality, building materials, HVAC （Heating, Ventilation, Air Conditioning） systems and people activity are important factors in human exposition of polluted indoor air. The degree of signification varies in dependence on pollution character and its sources. Buildings eliminate significantly people exposition of outdoor pollutants, but on the other hand, buildings are significant source of indoor pollution. The contamination of indoor air is largely from the use of gas for heating and cooking appliances. A comprehensive analysis of indoor air pollution by nitrogen oxides shows that the extent of indoor air pollution and consequent exposure varies as a result of many factors mainly the differing dislribution of appliances and their level of use. This study aims to formulate a mathematical model for the production of nitrogen oxides indoors. The physical processes that determine the concentrations of indoor nitrogen oxides as a function of outdoor concentrations, indoor emission rates and building characteristics have been mathematically described. The mathematical model developed has been parameterized for typical Slovak residences. The modeling of the occurrence of indoor nitrogen oxides and verification of the model is presented in this paper.

Analysis of Lateritic Soil Reinforced with Palm Kernel Shells for Use as a Sub-Base Layer for Low-Traffic Roads

In tropical areas,palm oil production generates significant amounts of waste,including palm kernel shells.The use of this waste in the civil engineering sector,presents a very challenging task.In the present study,the production of lateritic soil(A-2 in GTR classification and A-7-6(9)in HRB classification)reinforced with palm kernel shells is considered.In order to improve their performances,these materials are mixed using the Fuller’s parabolic law.Moreover,experimental tests are used to characterize the physical and mechanical geotechnical properties of the lateritic soil.After characterizing the matrix(i.e.,lateritic soil)and the inclusions(i.e.,palm kernel shells)in their natural state,it is found that Avrankou’s lateritic soil has a high level of fine particles(56.6%),high plasticity(PI=21%)and low lift(ICBR=17%);which makes it unusable in the pavement layer.Results also prove that the mixture composed of 39%of lateritic soil volume and 61%of PKS with a CBR index equals to 30 and the mixture composed of 45%of lateritic soil,40%PKS and 15%of lagoon sand with a CBR index equals to 41 can be used as sub-base layer for roads for low and medium traffic,respectively.

Elaboration of a Road Material Based on Clayey Soil and Crushed Sand

To contribute to the enhancement of unconventional local materials used for road construction,this study characterizes a crushed sand 0/5,a clayey soil and the litho-stabilized material without and with hydraulic binder and determines their use in accordance with some reference specifications(CEBTP 1984).It is shown that the different components are not usable alone in pavement base.Indeed,the plasticity index obtained for the clayey soil is 21%,a value higher than the imposed standards.In addition,the grading of the 0/5 crushed sand does not fit into the range proposed by CEBTP.A combination of these two(02)components is therefore considered to obtain a suitable material usable for the sub-base.This new material does not enter any class of the CEBTP lateritic soils.In order to be used in base layer,a treatment with hydraulic binder is carried out with the intention to improve its mechanical performances.The optimal dosage of hydraulic binder to achieve the desired mechanical performance is obtained by studying the evolution of the mechanical characteristics of the mixture.After this treatment,the Bearing Ratio index of the mix increases from 37 to 223 for the optimal dosage and the dry compaction density decreases from 2.11 to 2.06 g/cm3 while the optimal water content increases from 9%to 10.1%.

Characterization of Stabilized Earth Blocks with Incorporation of Cement Expanded Polystyrene for Use in Buildings

This work focuses on the development of local building materials in Benin for their efficient use in buildings. It aims to make mud bricks lightened with good mechanical, thermal and sound properties and enhance the waste polystyrene. This article is the result of experimental work on a broad field of applied sciences： building mechanics. The study is focused on BTS （blocks of stabilized earth） chosen as reference materials to which we linked polystyrene. The percentage of polystyrene varies from 0% to 100% starting from a constant volume of each reference material. The results showed that the increase in polystyrene percentage lowers mechanical properties. These results also showed that the gradual addition of polystyrene to the laterite-cement mixture has a significant influence on the density and mechanical resistances of the final composite material.

Feasibility Study for a Hybrid Power Plant(PV-Wind-Diesel-Storage)Connected to the Electricity Grid

In this work,we present a feasibility study for a new hybrid power plant(PV-Wind-Diesel-Storage)directly connected to the electrical grid.Several simulations are performed to verify the performance of the hybrid system under different scenarios using real meteorological data.It is shown that the performances of the hybrid system connected to the electrical network depend obviously on the available energy resources and constraints because the renewable energies are intermittent.In addition,the price of the kWh of electricity supplied by the hybrid system is determined,which amounts to$0.209/kWh,which is very cost effective and satisfactory for the considered sample conditions(Comoros Island).

Study of the Porosity of the Tiles out of Vibrated Mortar by Microstructural Analysis

The promotion and the popularization of the micro concrete tiles in any locality obligation with a will of durable development pass by a standard of quality, which is based on the results of scientific and technical research taking account of local specificities. This work proposes to study the porosity of the micro concrete by micro structural analysis. From this study, it comes out that the variation of porosity compared to the ratio of the fine gravels (s/(s + g)) is decreasing. Indeed more the granular ratio increases less low is the density of pores of material. The decrease of porosity according to the granular rate is not infinite;it tends towards a minimum starting from a rate of fine gravel close to 50%. The results obtained justify well the ratio of fine gravel practised by tileries.