IntroductionIt is generally thought that countries that experience extended periods of sunshine might better enjoy the benefit of solar energy. Nevertheless, the performance of photovoltaic (PV) devices is critically dependent on the ambient temperature and the operating temperature of a given device. Also, irradiance, relative humidity and harmattan dust particles, and several other parameters such as wind speed, wind chill and direction, seasonal variation of sunrise and sunset, rainfall, and how the module is installed (rooftop, ground system, orientation, etc.) can be expected to influence the performance of a solar panel.Generally, sunny climates are most often hot, with a large variation in relative humidity, ranking from dry to humid. It is necessary, therefore, to carry out in situ studies of the parameters of PV devices under controlled and varying conditions. Such a study of the seasonal variation of the operating temperature of solar PV panels was undertaken in Southern Ghana.Ghana's climate depends on three types of air masses. Consequently, Ghana has three distinct types of climate (Varley and White 1958, 34-50):

IntroductionThe basic idea behind modelling a solar cell is to obtain the values of the operating parameters for the device. To that extent, the most popular of the existing models is the Shockley five-parameter model in which the equation governing the behaviour of the cell is formulated as a transcendental exponential equation involving five parameters, which are I L , the light-generated current, I s , the reverse saturation current, R s , the series resistance, R sh , the shunt resistance and T, the operating temperature.In the conventional approach to solving the fiveparameter model equation, it is often assumed that the light-generated current is most approximately equal to the short-circuit current. However, Da Rosa (2009, 552-553) has pointed out that in the presence of a large series resistance, there is a significant difference between the light-generated current and the short-circuit current due to the conversion of noticeable incident photon energy to heat.Different approaches to the solution of the equation have been developed. Several of these approaches have proved somewhat cumbersome (Hart 1982, 281-288; Lasnier 1990, 65-76). This paper discusses an alternative formulation of the model. This formulation leads to a relationship which allows an easy determination of the light-generated current.

The determination of the surface tension of some liquids or solutions has been carried out using a tensiometer. The determination of the contact angle between the liquids and a planar surface has also been carried out using photography. Polar and dispersive contributions of the surface tension were obtained by calculation while the polarities of the liquids and solutions were determined applying Wu equations. This method gave the different results for solutions prepared from macromolecular compounds (acroleineethanolamine macromolecular solution 1 g/l, acroleine-diethanolamine macromolecular solution 1 g/l, acroleine-urea macromolecular solution 0.7 g/l and polyglutaraldehyde-ethanolamine macromolecular solution 1 g/) synthesized by Malonda from glutaraldehyde and acroleine. The dispersive and polar contributions of the surface tension were computed and used to calculate the surface tensions of solutions by the simple measurement of the contact angle. The results have revealed that the polarities were weak: 2% for all solutions except for the acroleine-diethanolamine macromolecular whose polarity was 6%. The surface tensions for all solutions varied from 67 to 59 dynes/cm.

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