A Simple Resistive Load I-V Curve Tracer for Monitoring Photovoltaic Module Characteristics

Current-Voltage (I-V) curve tracers are useful implements for solar Photovoltaic (PV) research and manufacturing, particularly when wishing to ascertain module yield viz-a-viz solar irradiation falling on the module in different climatic conditions. This paper presents a simple affordable and easy to fabricate instrument for tracing I-V characteristics of a PV module. It comprises of rapidly varying resistive loads centred on power resistors connected to relays and controlled by an electronic circuitry. The circuit consists of a 555 astable oscillator that is used to send clock pulses to the clock terminal of a 4017 decade counter which in turn produces a sequence of pulses. Each progression of pulse advances by one bit to sequentially turn on individual relays via driver transistors. The speed of the count is made variable from the frequency determining network of the 555 oscillator. The I-V characteristics of the module are thus measured by the sequential selection of the relays which are each connected to a selected load resistor to determine the operating point on the I-V curve. The currents and voltages are then recorded simultaneously with irradiance from a pyranometer, by a datalogger to which the instruments are connected. The circuit was tested on two monocrystalline modules to compare the effect of Harmattan dust on PV output yield

Sectional Investigation of Seasonal Variations of Surface Refractivity and Water Vapour Density over Nigeria

The accurate knowledge of radio refractive and water vapour density of the troposphere is important in the planning, budgeting and designing of transmission and reception of radiowave signals on earth-space path. Hence, there is the need to adopt more precise techniques to analyze the seasonal variation of refractivity and water vapour density over Nigeria. The seasonal variation of refractivity and water vapour density was studied using thirty-nine years meteorological data for forty-eight (48) stations over Nigeria. The forty-eight stations were grouped into nine vegetation and two major climates in Nigeria. Harmonic analysis approach was used in addition to the monthly mean computation. The results show that Forests zones values of refractivity and water vapour density are higher than Savannahs zones values. The refractivity value increases from about 281 N units at Sudarian Woodland in January to about 383.6 N units at Mangrove station in June. Water vapour density value increases from about 5.18 g/m3 at Brush and Thicket station in November to maximum value of about 22.36 g/m3 at Swamp Forest station in May. Results also show that over 80% variations in refractivity and over 70% variations in water vapour density are revealed in the first three harmonics at all the nine stations. The results indicate that the method of harmonic amplitudes and phases give a more analytical comparison between predictions model and observational data

NOVEL AIRFOIL DESIGN FOR SMALL HORIZONTAL AXIS WIND TURBINE: A PRELIMINARY RESULT

Various research efforts have been directed towards the design and re-design of wind turbine systems. This is in order to have more efficient, better performing and cost effective turbine systems. Based on this, efforts have been focused on wind turbine rotor design with emphasis placed on its aerodynamics. This is because the important criterion of a wind turbine rotor is the airfoil. It is the element that produces the forces that makes the turbine rotate. This research builds on existing knowledge and aims to further deepen knowledge in the field of wind turbine rotor design. The study designed and analysed a new airfoil for use in a small horizontal axis wind turbine. It employed the flow stage airfoil behaviour together with analytical software tools that include XFLR5, AirfoilPrep_v2.02.01, WT_Perf, and MATLAB.. Three well known and tested airfoils were employed and the coordinates were interpolated to create a new, more efficient and better performing small wind turbine rotor airfoil. The outcome showed the new airfoil performs better with good glide ratio over longer angle range, chord distribution and blade twist among other things. The parameters of the new airfoil were such that 10.17%, 26.49%, 6.26% and 45.0% of the chord characterised the maximum thickness and its position, and the maximum camber and its position respectivel

One year results of one minute Rainfall Rate Measurement at Covenant University, Southwest Nigeria

One year results of one minute rainfall rate measurement at Ota, Southwest, Nigeria (6° 42'N, 3° 14'E) from a wireless Davis Vantage Pro2 Weather Station is presented. The weather station was set at one minute integration time, and the rainfall rate data from the months of April 2012 to March 2013 have been analyzed. One minute rainfall rate at various percentages of time are needed for the modeling and prediction of rain attenuation at microwave frequencies for both terrestrial and earth space links. The measured one-minute rainfall rate events captured by the instrument for the past one year varies between 3 to 141 mm/h from 1% to 0.01% of time in an average year respectively. When the results were compared to the ITU_RP SG3 Digital Map from 1% to 0.01% (3.63 to 62.87 mm/h) the ITU-RP model underestimate rainfall rate at 0.01% exceedance by 55% and over estimate the rainfall rate at 1% exceedance by 3% respectively

Seasonal Variation of Surface Radio Refractivity and Water Vapour Density for 48 Stations in Nigeria

The monthly and seasonal variation of surface refractivity and water vapour density were studied using thirtynine years meteorological data for forty-eight stations in Nigeria. The factors which influence the transmission of radio signals operating within the troposphere are water vapour and refractivity. The results show that the surface refractivity and water vapour density generally have higher values during the rainy season than dry season at all station studied. Furthermore the results show that the value of surface refractivity and water vapour density varies from about 263 N-units and 3 g/m3 in arid region of Nigeria (North East) to about 393 N-units and 23 g/m3 in the coastal area of Nigeria (South West) respectively. For optimal performance of terrestrial radio link across Nigeria it is required to account for the variability of these parameters for optimal systems design

Review of Rain Attenuation Measurements On Earth - Space Links in Nigeria

Due to the prevailing impact of rain on microwave and millimetre wave propagation in tropical climates, fade margins derived from experimental campaigns would provide more practical estimates for planning. In this paper, the extent of work done on the experimental assessment of the attenuation induced by rain on practical earth-space links in Nigeria is presented. The cumulative rain rate distributions derived from the instantaneous precipitation indices for propagation modelling and the estimation of fade margin is presented for Ile-Ife, Akure, Ilorin, Ota, Osogbo and Ogbomoso. Results reveals the spatial variability of the point rainfall rate across these stations. Although the stations engaged with measurement on rain attenuation are limited in number, preliminary results from new stations are presented, while addition data from ongoing campaigns will provide a robust indices for modelling the digital DTH links and for evaluating the performance of pre-existing models over Nigeria

Large-scale phenotyping of patients with long COVID post-hospitalization reveals mechanistic subtypes of disease

One in ten severe acute respiratory syndrome coronavirus 2 infections result in prolonged symptoms termed long coronavirus disease (COVID), yet disease phenotypes and mechanisms are poorly understood1. Here we profiled 368 plasma proteins in 657 participants ≥3 months following hospitalization. Of these, 426 had at least one long COVID symptom and 233 had fully recovered. Elevated markers of myeloid inflammation and complement activation were associated with long COVID. IL-1R2, MATN2 and COLEC12 were associated with cardiorespiratory symptoms, fatigue and anxiety/depression; MATN2, CSF3 and C1QA were elevated in gastrointestinal symptoms and C1QA was elevated in cognitive impairment. Additional markers of alterations in nerve tissue repair (SPON-1 and NFASC) were elevated in those with cognitive impairment and SCG3, suggestive of brain–gut axis disturbance, was elevated in gastrointestinal symptoms. Severe acute respiratory syndrome coronavirus 2-specific immunoglobulin G (IgG) was persistently elevated in some individuals with long COVID, but virus was not detected in sputum. Analysis of inflammatory markers in nasal fluids showed no association with symptoms. Our study aimed to understand inflammatory processes that underlie long COVID and was not designed for biomarker discovery. Our findings suggest that specific inflammatory pathways related to tissue damage are implicated in subtypes of long COVID, which might be targeted in future therapeutic trials

Development of a Low-Cost Soil Heat Flux and Temperature Profile with Logger

Variation of soil temperature and soil heat flux measurements from a locally fabricated and calibrated device were analyzed and compared with a standard device. The soil heat flux consists of two-disc aluminum plates, dielectric material and two thermocouples such that each thermocouple was sandwiched between the aluminum plates and one side of the dielectric material. The sizes of the aluminum plates and the dielectric material were 32 mm in diameter and their thickness is 2.5 mm. Differential temperature between two thermocouples attached to two aluminum plates separated by a thermal insulator was used to measure the soil heat flux values. The thermocouples amplifier module AD8495 and then combined with a 16-bit Analog to Digital Converter (ADS1115) for a good measurement resolution was employed for the signal conditioning. A semiconductor sensor DS18B20 was used to measure the soil temperature. The microSD shield was included for storing data and DS3232, a Real Time Clock (RTC) module for timekeeping. Arduino mega 2560 microcontroller was used to coordinate the whole active and display the activities on LCD. The soil heat flux sensor was calibrated using the principle of thermal conduction over the surface area by heating with a known heat source. The thermal conductivity of heat flux is given by 3.3407 (WV-1m-1) from the empirical deduction. The temperature sensing unit was checked for accuracy by inserting it inside a calorimeter with the mercury-in-glass thermometer and the correlation obtained was 0.92. The soil heat flux and temperature sensing unit were compared with that of standard Campbell device. The correlation obtained for soil heat flux and temperature were 0.89 and 0.95 respectively. The result obtained when installed at the Redeemer’s University, Ede, Nigeria, the variation of soil heat flux and temperature when placed at the same level of 10 cm into the soil gave the same value. The maximum peak of heat flux density usually occurs at about 13:00 pm to 15:00 pm with values around 260 W/m2 at 10 cm. The logging interval can be preset to any rate from 30 seconds and above

Variability of GPS-derived ionospheric TEC over Nigeria during a year of low solar activity

An investigation of the diurnal and seasonal variability of ionospheric total electron content (TEC) over Nigeria is carried out in this study using the global positioning system (GPS) observable. Nigeria coordinates fall within the trough of the equatorial ionisation anomaly region of the African sector. The TEC data used were obtained from the ground-based GPS receiver stations of the Nigerian GNSS network of stations (NIGNET). The stations with their respective geomagnetic latitudes are: Abuja (–1.64°), Yola (–1.32°), Zaria (–0.13°), Kebbi (0.72°). The results of the diurnal analysis of the relative variability index (VD) revealed higher nighttime values than daytime values. The diurnal variation of VD also showed two conspicuous peaks: post-midnight and post-sunset. The diurnal–seasonal variation does not reveal any consistent pattern (no particular season leads the others throughout). On average, considering all the seasons together, maximum TEC variability occurred in Zaria (62%) and minimum in Yola (54%). Seasonally, maximum VD was recorded during the March equinox and the lowest was recorded during the December equinox.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Validation of TEC models over an equatorial station

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal