A Review of Information Needs of Rice Farmers: A Panacea for Food Security and Poverty Alleviation

The study aimed at reviewing rice farmers’ agricultural information needs, access, and utilization and the constraints faced in sourcing for information. Information were got on the concept of information needs, assessment of information needs of rice farmers, concept of information access, farmers’ information search behaviour,  concept of utilization or adoption of information and the constraints faced or being faced. Review of related literature on the information needs of rice farmers, access and utilization have been included. Recommendations are given for effective transformation in rice production technology sub-sector if considered such as setting up of adult literacy education programme for farmers, developing ICT-based agricultural information delivery support system. Key words: Information, Technology, Utilization, Innovation, Access, Farmer

Modelling of solder interconnection’s performance in photovoltaic modules for reliability prediction

A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophy.Standard crystalline silicon photovoltaic (PV) modules are designed to continuously convert solar energy into electricity for 25 years. However, the continual generation of electricity by the PV modules throughout their designed service life has been a concern. The key challenge has been the untimely fatigue failure of solder interconnections of solar cells in the modules due to accelerated thermo-mechanical degradation. The goal of this research is to provide adequate information for proper design of solar cell solder joint against fatigue failure through the study of cyclic thermo-mechanical stresses and strains in the joint. This is carried-out through finite element analysis (FEA) using ANSYS software to develop the solar cell assembly geometric models followed by simulations. Appropriate material constitutive model for solder alloy is employed to predict number of cycles to failure of solder joint, hence predicting its fatigue life. The results obtained from this study indicate that intermetallic compound thickness (TIMC); solder joint thickness (TSJ) and width (WSJ) have significant impacts on fatigue life of solder joint. The impacts of TIMC and TSJ are such that as the thicknesses increases solder joint fatigue life decreases. Conversely, as solder joint width (WSJ) increases, fatigue life increases. Furthermore, optimization of the joint is carried-out towards thermo-mechanical reliability improvement. Analysis of results shows the design with optimal parameter setting to be: TIMC -2.5μm, TSJ -20μm and WSJ -1000μm. In addition, the optimized model has 16,264 cycles to failure which is 18.82% more than the expected 13,688 cycles to failure of a PV module designed to last for 25 years

Economic Analysis of Irrigated Irish Potato Production in Plateau State

The study examined the economics of irrigated Irish potato production in Plateau State. A multistage sampling technique using purposive and systematic random sampling was used to obtain data from a sample size of 120 respondents using structured questionnaires. Data were analyzed using Descriptive Statistics, Gross Margin Analysis, Benefit –Cost Analysis and Sensitivity Analysis. Results reveals that majority of the farmers were educated (64.17%) adults (58.33%) with long years (97%) of experience in Irish potato irrigation farming, and owned an average of 0.7 hectares of irrigated farm land each. Cost and Return analysis revealed that costs of seeds, labor and chemical fertilizers made up the highest (89.40%) portion of the average total variable cost of production. Results also revealed that irrigated Irish potato production in Plateau State is a profitably lucrative enterprise with a robust economic viability as shown by values  of Gross Margin (N655,637.88), benefit–Cost Ratio (2.64) and Sensitivity Analysis ratio (2.16). The study recommends expansion in irrigated Irish potato farm lands in addition to adoption of technologies that will minimize cost of seeds, labor and chemical fertilizers. Keywords: Gross Margin, Benefit, Cost, Sensitivity, Profitability

Impact of Climate Change on the Design Parameters of Heating, Ventilation and Air Conditioning Systems for Manned Spacecraft

Climatic design information has been published for several locations in the world by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) but there has not been data for Nigerian cities in these publications. Therefore, this study was embarked upon to bridge the gap in knowledge. The study of impact of climate change on the design parameters of Heating, Ventilation and Air Conditioning (HVAC) systems for spacecraft cabin environment is presented with particular focus on Ikeja-Lagos, Nigeria. Firstly, the characteristics climate parameters such as outdoor dry-bulb temperature, coincident wet-bulb temperature, relative humidity, pressures, air composition, among others as it affects manned spacecraft were discussed. The data for climatic parameters for Ikeja-Lagos, Nigeria, for a period of fifteen years (1995-2009) were obtained from Nigerian Meteorological Agency (NIMET), Oshodi-Lagos. Statistical data and Microsoft excel were used for evaluation of variation trends of the climate parameters for departure city. This is very important in determining thermal human comfort in spacecrafts on ascent. Results obtained from this study are hereby presented. The Ikeja-Lagos dry-bulb temperature average results obtained were 33.81°C, 32.98°C, 32.3°C, 22.1°C, 21.19°C, 20.43°C, 23.84°C and 31.65oC.at 0.4%, 1.0%, 2.0%, 97.5%, 99.0%, 99.6%, median of extreme lows and median of extreme highs, respectively. The Ikeja-Lagos relative humidity average results were 116.3, 112.65, 109.14, 99.83 and 49.42 at 0.4%, 1% and 2.0% occurrence as well as at median of extreme highs and median of extreme lows, respectively. Ikeja-Lagos had mean coincident dry bulb temperature of 33.81°C and 32.98°C at 0.4% and 1% percentile respectively. The dry bulb temperature for Ikeja-Lagos was determined to be an average range from 20.43°C to 22.1°C between January to December, in the period of 1995-2009, at 97.5% 99% and 99.6% percentile respectively. These results provide values of design parameters which are useful in the design of HVAC for space crafts with climate change adequately taken into consideration as it applies to Ikeja-Lagos, Nigeri

Impact of inter-metallic compound thickness on thermo-mechanical reliability of solder joints in solar cell assembly

This is an accepted manuscript of an article published by Elsevier in Microelectronics Reliability on 13/11/2020, available online: https://doi.org/10.1016/j.microrel.2020.114008 The accepted version of the publication may differ from the final published version.This study evaluates the impact of intermetallic compound (IMC) thickness on thermo-mechanical reliability of lead-free SnAgCu solder joints in crystalline silicon solar cell assembly with regard to fatigue life. Finite element modelling is used to simulate the non-linear thermo-mechanical deformation of the joints. Five geometric models of solar cell assemblies with different IMC thickness layers in the range of 1 to 4 μm are utilized. The models were subjected to accelerated thermal cycling from 40 °C to 85 °C employing IEC 61215 standard for photovoltaic panels. Creep response of each of the assembly's solder joints to the induced thermal load were simulated using Garofalo-Arrhenius creep model. Simulation results indicate that when IMC thickness grows incrementally to 1, 2, 2.5, 3 and 4 μm, thermo-mechanical fatigue life of solder joints diminishes to 13,800, 11,800, 10,600, 9400 and 7800 cycles to failure respectively. Thus, solder joint fatigue life decreases as the IMC thickness increases during service lifetime. Therefore, proper design of solder joint in crystalline silicon solar cell assembly must include consideration of IMC layer thickness to prevent premature failure and to ensure fulfilment of desired functional lifetime of 13,688 cycles to failure (25 years).Accepted versio

Evaluation of thermo-mechanical damage and fatigue life of solar cell solder interconnections

The soldering process of interconnecting crystalline silicon solar cells to form photovoltaic (PV) module is a key manufacturing process. However, during the soldering process, stress is induced in the solar cell solder joints and remains in the joint as residual stress after soldering. Furthermore, during the module service life time, thermo-mechanical degradation of the solder joints occurs due to thermal cycling of the joints which induce stress, creep strain and strain energy. The resultant effect of damage on the solder joint is premature failure, hence shortened fatigue life. This study seeks to determine accumulated thermo-mechanical damage and fatigue life of solder interconnection in solar cell assembly under thermo-mechanical cycling conditions. In this investigation, finite element modelling (FEM) and simulations are carried out in order to determine nonlinear degradation of SnAgCu solder joints. The degradation of the solder material is simulated using Garofalo-Arrhenius creep model. A three dimensional (3D) geometric model is subjected to six accelerated thermal cycles (ATCs) utilising IEC 61215 standard for photovoltaic panels. The results demonstrate that induced stress, strain and strain energy impacts the solder joints during operations. Furthermore, the larger the accumulated creep strain and creep strain energy in the joints, the shorter the fatigue life. This indicates that creep strain and creep strain energy in the solder joints significantly impacts the thermo-mechanical reliability of the assembly joints. Regions of solder joint with critical stress, strain and strain energy values including their distribution are determined. Analysis of results demonstrates that creep energy density is a better parameter than creep strain in predicting interconnection fatigue life. The use of six ATCs yields significant data which enable better understanding of the response of the solder joints to the induced loads. Moreover, information obtained from this study can be used for improved design and better-quality fabrication of solder interconnections in solar cell assembly for enhanced thermo-mechanical reliability

Optimization of thermo-mechanical reliability of solder joints in crystalline silicon solar cell assembly

This is an accepted manuscript of an article published by Elsevier in Microelectronics Reliability on 28/12/2015, available online: https://doi.org/10.1016/j.microrel.2015.12.031 The accepted version of the publication may differ from the final published version.© 2015 Elsevier Ltd All rights reserved. A robust solder joint in crystalline silicon solar cell assembly is necessary to ensure its thermo-mechanical reliability. The solder joint formed using optimal parameter setting accumulates minimal creep strain energy density which leads to longer fatigue life. In this study, thermo-mechanical reliability of solder joint in crystalline silicon solar cell assembly is evaluated using finite element modelling (FEM) and Taguchi method. Geometric models of the crystalline silicon solar cell assembly are built and subjected to accelerated thermal cycling utilizing IEC 61215 standard for photovoltaic panels. In order to obtain the model with minimum accumulated creep strain energy density, the L9 (33) orthogonal array was applied to Taguchi design of experiments (DOE) to investigate the effects of IMC thickness (IMCT), solder joint width (SJW) and solder joint thickness (SJT) on the thermo-mechanical reliability of solder joints. The solder material used in this study is Sn3.8Ag0.7Cu and its non-linear creep deformation is simulated using Garofalo-Arrhenius creep model. The results obtained indicate that solder joint thickness has the most significant effect on the thermo-mechanical reliability of solder joints. Analysis of results selected towards thermo-mechanical reliability improvement shows the design with optimal parameter setting to be: solder joint thickness - 20 μm, solder joint width - 1000 μm, and IMC thickness - 2.5 μm. Furthermore, the optimized model has the least damage in the solder joint and shows a reduction of 47.96% in accumulated creep strain energy density per cycle compared to the worst case original model. Moreover, the optimized model has 16,264 cycles to failure compared with the expected 13,688 cycles to failure of a PV module designed to last for 25 years.The authors acknowledge funding provided by the Petroleum Technology Development Fund (PTDF, PTDF/E/OSS/PHD/ZMT/623/12), Nigeria used in carrying out this study.Published versio

A review of photovoltaic module technologies for increased performance in tropical climate

The global adoption and use of photovoltaic modules (PVMs) as the main source of energy is the key to realising the UN Millennium Development Goals on Green Energy. The technology – projected to contribute about 20% of world energy supply by 2050, over 60% by 2100 and leading to 50% reduction in global CO2 emissions – is threatened by its poor performance in tropical climate. Such performance discourages its regional acceptance. The magnitude of crucial module performance influencing factors (cell temperature, wind speed and relative humidity) reach critical values of 90 °C, 0.2 m/s and 85%, respectively in tropical climates which negatively impact module performance indices which include power output (PO), power conversion efficiency (PCE) and energy payback time (EPBT). This investigation reviews PVM technologies which include cell, contact and interconnection technologies. It identifies critical technology route(s) with potential to increase operational reliability of PVMs in the tropics when adopted. The cell performance is measured by PO, PCE and EPBT while contacts and interconnections performance is measured by the degree of recombination, shading losses and also the rate of thermo-mechanical degradation. It is found that the mono-crystalline cell has the best PCE of 25% while the Cadmium Telluride (CdTe) cell has the lowest EPBT of 8-months. Results show that the poly-crystalline cell has the largest market share amounting to 54%. The CdTe cell exhibits 0% drop in PCE at high-temperatures and low irradiance operations – demonstrating least affected PO by the conditions. Further results establish that back contacts and back-to-back interconnection technologies produce the least recombination losses and demonstrate absence of shading in addition to possessing longest interconnection fatigue life. Based on these findings, the authors propose a PVM comprising CdTe cell, back contacts and back-to-back interconnection technologies as the technology with latent capacity to produce improved performance in tropical climates

Effect of operating temperature on degradation of solder joints in crystalline silicon photovoltaic modules for improved reliability in hot climates

Accelerated degradation of solder joint interconnections in crystalline silicon photovoltaic (c-Si PV) modules drives the high failure rate of the system operating in elevated temperatures. The phenomenon challenges the thermo-mechanical reliability of the system for hot climatic operations. This study investigates the degradation of solder interconnections in c-Si PV modules for cell temperature rise from 25 °C STC in steps of 1 °C to 120 °C. The degradation is measured using accumulated creep strain energy density (Wacc). Generated Wacc magnitudes are utilised to predict the fatigue life of the module for ambient temperatures ranging from European to hot climates. The ANSYS mechanical package coupled with the IEC 61,215 standard accelerated thermal cycle (ATC) profile is employed in the simulation. The Garofalo creep model is used to model the degradation response of solder while other module component materials are simulated with appropriate material models. Solder degradation is found to increase with every 1 °C cell temperature rise from the STC. Three distinct degradation rates in Pa/°C are observed. Region 1, 25 to 42 °C, is characterised by degradation rate increasing quadratically from 1.53 to 10.03 Pa/°C. The degradation rate in region 2, 43 to 63 °C, is critical with highest constant magnitude of 12.06 Pa/°C. Region 3, 64 to 120 °C, demonstrates lowest degradation rate of logarithmic nature with magnitude 5.47 at the beginning of the region and 2.25 Pa/°C at the end of the region. The module fatigue life, L (in years) is found to decay according to the power function L=721.48T-1.343. The model predicts module life in London and hot climate to be 18.5 and 9 years, respectively. The findings inform on the degradation of c-Si PV module solder interconnections in different operating ambient temperatures and advise on its operational reliability for improved thermo-mechanical design for hot climatic operations

Determination of Maiganga Lignite Coal Combustion Characteristics for Application in Thermal Power Plant using Standard Mathematical Models

This paper presents determination of Maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. The problem statement was that Nigeria cement plants uses rotary kiln coal burner despite its associated drawbacks such as sudden explosion and incomplete combustion. Fluidized bed technology has less of the drawbacks associated with rotary kiln coal burner. The integration of Maiganga coal in mathematical models will increase accurate prediction of operating variables useful in design and sizing the components of fluidized bed thermal power plant. The methodology of the study includes utilization of established numerical models based on energy balance and fuel properties for Maiganga lignite combustion. The coal was fired in a pilot atmospheric fluidized bed combustor (FBC). The results obtained include the theoretical air required per kg of Maiganga lignite was 7.4, at an excess air of 10% and maximum mass of air supplied per kg of Maiganga lignite of 8.82. The time for burn out of particle sized 0.4 mm was determined to be 2.64 min, with burning rate of 0.23 kg/min (3.8 g/s). The ignition temperature of 797 K and fuel power of 84 kW for Maiganga coal were determined for the pilot FBC in this study. The Maiganga lignite fuel, air and sorbent flow rates through the fluidized bed combustor were predicted to be 14.2 kg/hr (0.23 kg/min), 202.4 kg/hr and 1.26 kg/hr respectively. The combustion performance evaluation of the fluidized bed combustor had specific firing rate for the lignite at graded particle size of between 0.2-1.12 mm at bed temperature of 1173 K was 2.8 g/m2s, air-fuel ratio of 23 and equivalence ratio of 0.45. The above results are similar to coal burnout time of 3 minutes and equivalence ratio of 0.40 in an atmospheric fluidized bed combustor in the literature. Hence, above parameters can be used to design and model a safe ignition and good combustion characteristics in other lignite fired power plants similar to that of Maiganga lignite coal