Imran Ali Siddiqui

A suitable design of solar power project requires accurate measurements of solar radiation for the site of investigation. Such measurements play a pivotal role in the installation of PV systems. While conducting such studies, in general, global solar radiation (GSR) is recorded, whereas diffuse component of solar radiation on a horizontal surface is seldom recorded. The objective of the present study is to assess diffuse solar radiation (DSR) on horizontal surfaces by using polynomial models for Lahore, Pakistan (27.89 N, 78.08 E) and by correlating clearness index with diffuse fraction. The established models are compared with some of the existing models from the literature. Performance of models is evaluated by employing five goodness-of-fit (GoF) tests that are, mean bias error (MBE), root mean square (RMSE), Coefficient of Determination (R2), Mean Absolute Percentage Error (MAPE) and Akaike’s Information Criterion (AIC). The comparison of the results of goodness-of-fit tests with those of existing models indicate that the models established in the present study are performed better as compared to the existing models. The values of statistical error analysis further suggested that a cubic model with a good accuracy of 97.5% and AIC of -22.8 is relatively more suitable for this climatic region for estimating diffuse solar radiation. The study shows that the model developed is in good agreement with Elhadidy and Nabi model with an accuracy of 96.1% and AIC of 4.4 and satisfactory results are obtained for Lahore. The findings can help to give a generous understanding of solar radiation in order to optimize the solar energy conversion systems. The results of this study provide a better understanding of the associations between global solar radiation, clearness index and diffused fraction for the region under study.

04 March, 2019 Accepted: 24 April, 2019 Abstract: Wind energy assessment of Ormara, Gwadar and Lasbela wind sites which are located in province Baluchistan is presented. The daily averaged wind speed data for the three sites is recorded for a period of four years from 2010-2013 at mast heights 7 m, 9.6 m and 23 m. Measured wind data are extrapolated to heights 60 m (Ormara), 80 m (Gwadar) and 60 m (Lasbela). Yearly averaged wind speeds are modeled using a two parameters Weibull function whose shape (k) and scale (c) parameters are computed using seven well known numerical iterative methods. Reliability of the fitting process is assessed by employing three goodness-of-fit test statistics, namely, RMSE, R2 and χ2 tests. Tests indicate that MLE, MLM and EPFM outperformed other Weibull parameter estimation methods for a better fit behavior. Yearly Weibull pdf and cdf are obtained and Weibull wind characteristics are determined. Wind turbines Ecotecnia 60/1.67 MW and Nordex S77 1500 kW are used to extract wind energy on yearly basis. Estimated yearly Weibull power densities are in the range 623.00 - 700.13 W/m2, 276.04 – 307.55 W/m2 and 66.85 – 75.93 W/m2 for Ormara, Gwadar and Lasbela respectively. Extracted wind energy values for Ormara and Gwadar using wind turbines are reported as ca. 8623 kWh and ca. 4622 kWh, respectively.

Weibull distribution function is fitted to a measured wind speed data set at mast height of 30 m and Gharo-Sindh (Pakistan) is selected as a case site under study. Wind speed data recorded in one minute interval for the year 2004 is used to estimate Weibull parameters (k and c). Weibull parameters are calculated using Modified Maximum Likelihood Method (MMLM), Maximum likelihood Method (MLM) and Method of Moment (MoM) and the results obtained are compared. Kolomogorov-Smirnov test, Root Mean Square Error (RMSE) and R2 tests are performed to test the goodness-of-fit of the Weibull distribution function. The analysis is based on recorded monthly and yearly wind speed data. Goodness-of-fit tests indicate a better performance of MMLM and MLM as compared to MoM. Wind power density is estimated for the site under study using MMLM and Weibull function estimator. A lowest Weibull mean wind speed of 3.73 m/s in the month of October and highest value of 7.90 m/s for August are observed and correspondingly power densities of 80.95 W/m2 and 425.87 W/m2 are obtained. Descriptive statistics for the measured wind speed data is also evaluated.

The importance of characterizing the wind shear at a specified location for the utilization of wind turbine is of vital importance. Such study is considered necessary both for the turbine design and prediction of its power output. In situations where the wind speed at different heights is required if measured values are known at one height then, generally it is extrapolated to the hub height by using the one-seventh power law. The exponent in this case has a value of 1/7 but it is observed that, the value of exponent varies with the type of terrain therefore; the one-seventh power law is not suitable for wind speed extrapolation and energy estimation. It has been found that, the one-seventh power law has a tendency to miscalculate the actual long-term average wind speeds. Hence, for accurate estimation of wind speed at a height, both monthly or seasonal and diurnal values of wind shear coefficient (WSC) have to be used. In this paper, the power law exponent for three sites located over coastal sites in South of Pakistan, i.e., Katibandar, Jati and Gharo, is established using wind speeds measured at heights 10 m and 30 m above the ground (AGL). Wind data is obtained from Pakistan Meteorological | department (PMD). Mean values of WSC were found to be 0.318 at Jati, 0.321 at Gharo and 0.269 at KatiBander. In addition, yearly, monthly and diurnal variation for WSC is also analyzed. The research showed that, the wind shear coefficient significantly fluctuates by seasonal and diurnal changes. Comparisons has been made for discrepancies in energy estimation, payback period and cost of energy (Cents/Kwh) using wind speed values extrapolated from 10 m, for one-seventh power law and overall mean WSC as exponent. The study showed that, if wind speed is extrapolated with WSC of 0.143, the energy is underestimated by 16-33% at Gharo, 12-25% at Katibandar and 28-51% at Jati for all considered hub heights. Error in the Payback period is estimation as 19–34% at Gharo, 16–27% at Katibandar and 31–48% at Jati for all considered hub heights, for 10 m wind data extrapolated with WSC of 0.143. The percentage change in the COE estimation for the two wind shear factors and three sites under study show that, if 10 m wind data extrapolated with WSC 0.143, the COE overestimated is between 19-34% for Gharo, 16-27% for Katibandar and 31- 48% for Jati for all considered hub heights. It is evident from results that, the 1/7 power law, tends to produce misleading results for the feasibility study.

Aims: The aim was to determine the influence of some Aspergillus species on the production of nematicidal agent(s) in vitro and biocontrol of Meloidogyne javanica in tomato by Pseudomonas fluorescens strains CHA0 and CHA0/pME3424. Methods and Results: Six species of Aspergillus, isolated from the rhizosphere of certain crops, produced a variety of secondary metabolites in vitro. Culture filtrate (CF) obtained from Ps. fluorescens strain CHA0 and its2,4‐diacetylphloroglucinol overproducing mutant CHA0/pME3424 grown in King's B liquid medium caused significant mortality of M. javanica juveniles in vitro. Bacterial growth medium amended with CF of A. niger enhanced nematicidal and β‐galactosidase activities of fluorescent pseudomonads while A. quadrilineatus repressed such activities. Methanol or ethyl acetate extracts of the CF of A. niger markedly optimized bacterial efficacy to cause nematode deaths while hexane extract of the fungus had no influence on the nematicidal activity of the bacterial strains. A. niger applied alone or in conjunction with the bacterial inoculants inhibited root‐knot nematode galling in tomato. On the other hand, A. quadrilineatus used alone or together with CHA0 did not inhibit nematode galling but when used in combination with strain CHA0/pME3424 did reduce galling intensity. Conclusions: Aspergillus niger enhances the production of nematicidal compounds by Ps. fluorescensin vitro and improves biocontrol potential of the bacterial inoculants in tomato while A. quadrilineatus reduces bacterial performance to suppress root‐knot nematodes. Significance and Impact of the Study: Rhizosphere harbours a variety of micro‐organisms including bacteria, fungi and viruses. Aspergillus species are ubiquitous in most agricultural soils and generally produce a variety of secondary metabolites. Such metabolites synthesized by Aspergillus species may influence the production of nematicidal agents and subsequent biocontrol performance of the bacterial inoculants against plant‐parasitic nematodes. This fact needs to be taken into consideration when using biocontrol strains in an agriculture system.