Photovoltaic systems when integrated into a building structure can satisfy the world’s energy requirements at a competitive cost by providing onsite electrical and thermal energies for domestic appliances. The energy yield of the photovoltaic system is affected by the intensity of the solar radiation, wind speed, tilt angle, orientation, geographical location, etc. This paper presents an optimisation model of the tilt angle and orientation of a photovoltaic thermal system. A methodology has been developed to optimize the tilted angle of the roof for higher exergy output taking into account the intensity of solar radiation, wind speed, geographical location, cost of cleaning dust, etc. For a system installed in the city of Douala, Cameroon, it is recommended that the PV should be inclined at an angle between 10° and 20° south-facing for economical output. The cost per unit of electricity between the tilt inclination angles from 0° to 20° with south orientation is USD 0.04 per kWh. The cost of electricity loss due to a 20° tilt inclination angle can be compensated with the labour cost and work required for cleaning the photovoltaic thermal (PVT) system of the horizontal roof. The system installed over an effective area of 8 m2 is capable of producing annual net exergy of 2195.81 kWh/year at an efficiency of 11.8%.

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In N'Djaména, the use and marketing of certain hydrocarbons does not comply with any standard in force or with regulations provided for this purpose. Their evaporation and unregulated release into the wild significantly affects the ecosystem. The present work consists in developing a method of extraction from sediments polluted by bio surfactant (rhamnolipid) assisted by microwaves. The goal here is to look for the presence of polycyclic aromatic hydrocarbons in polluted sediments. The rhamnolipid used consists of monorhamnolipids and di-rhamnolipids, its emulsion index is 64.66% and is composed of saturated and unsaturated fatty acids having carbon numbers ranging from 12 to 18. We used the microwave micellar extraction process. It was made by keeping the concentration values fixed at 0.15 g/L and the power at 400 W and more. We observed a positive interaction of the rhamnolipid concentration factors and the power of the microwave to obtain the optimal conditions at the time of 50 S, at the concentration of 0.16 g/L and at the power of 443 W for a rate of optimal extraction of 0.91%. Chromatographic analysis by GC-MS of the optimum extracts allowed us to identify twelve (12) C10 to C43 n-alkanes and eight (8) PAHs. It emerges from this analysis that the rhamnolipid extracts seven (7) Polycyclic Aromatic Hydrocarbons in equivalent proportions while the tween 80 extracts only four (4) Polycyclic Aromatic Hydrocarbons with a high proportion (80.02%) of benzo [a] antracene.

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