A single hybrid parameter-based model for calibrating hargreaves-samani coefficient in Nigeria

Abstract

The present research was designed to locally calibrate Hargreaves-Samani computing model (HS) in twenty-one (21) locations with their corresponding coastal and interior regions in Nigeria employing a single hybrid parameter-based model to obtain the adjusted Hargreaves-Samani coefficient (AHC) for Nigerian environment. To achieve this purpose, meteorological parameters such as extraterrestrial solar radiation, maximum sunshine duration, minimum and maximum temperatures were employed as input parameters to compute the original HS model and equally calibrate the original HS model. The monthly AHCs were obtained by multiplying the 0.17 by the monthly ratio of the observed global solar radiation (H) to H calculated from original HS model. The average value was obtained per station. These observed AHC values were considered as the target values for the development of hybrid parameter-based models (HP) for every station used for calibrating original HS model. On the whole, the result from the statistical indicators confirmed that the locally calibrated HS model performed better than the original HS model in all stations (including coastal and interior regions) investigated. Both the original and calibrated HS models underestimated H at annual timescale, but the calibrated HS model provided closer average values with H, which could confirm the good performances of the calibrated HS model. Therefore, the calibrated HS model obtained in this research could be highly recommended for estimating H in Nigeria when only temperature data are available.

Relationship between photosynthetically active radiation with global solar radiation using empirical model over selected climatic zones in Nigeria

“…The H data measured in kwhm -2 day -1 were converted to MJm -2 day -1 using a factor of 3.6 [33] and was further converted to EM -1 using a converting factor of 4.56 [1]. The details of the study area are found in Nwokolo and Ogbulezie [31]. …”

Modeling the influence of cloudiness on diffuse horizon-tal irradiation under various sky conditions in Nigeria

“…The GHI and DHI data measured in kwhm -2 day -1 were converted to MJm -2 day -1 using a factor of 3.6. The details of the study area are found in Nwokolo and Ogbulezie [19]. …”

“…It is therefore imperative to analyse DHI using GHI and clearness index obtained from NASA data. This will produce DHI data as a baseline for further scientific, environmental and atmospheric research without the substantial cost of the instrumentation network that would otherwise be needed [17][18][19]. The aim of this research paper is to develop an empirical model for estimating DHI in six tropical ecological zones in Nigeria.…”

A critical review of theoretical models for estimating global so-lar radiation between 2012-2016 in Nigeria

“…In this review, the global solar radiation models are classified according to the basis of their input parameters applied in correlating with the clearness index. The clearness index (kt) indicates the percentage depletion by the sky of the incoming solar radiation and therefore, gives both the level of availability of solar radiation and changes in the atmospheric condition in a given environment [11][12]. Mathematically, clearness index is the ratio of horizontal global solar radiation (often measured and collected from Nigeria Meteorological Station (NIMET), International Institute of Tropical Agriculture (IITA), National Aeronautics and Space Administration (NASA) atmospheric science data center by researchers in Nigeria) to the extraterrestrial solar radiation (Ho) on a daily or monthly basis as found in literature expressed as:…”

“…These assessments have involved direct measurement with meteorological measuring instrument such as Eppley pyranometer and satellite remote-sensing instrument such as Moderate-Resolutoin Imaging Spectroradiometer (MODIS) products, and meteosat-images etc. Due to cost implication, maintenance, expertise involved in ground measurement and satellite-derived data, especially in rural and developing locations in Nigeria, numerous estimation models employing empirical, artificial neutral network and other techniques were proposed in Nigeria by solar-energy researchers that can produce global solar radiation data without the substantial cost of the instrumental network that would otherwise be needed [11][12][13][14].…”