Preliminary design of an off-grid photovoltaic system for smallholder water pumping in Sub-Saharan Africa

University essay from Högskolan i Gävle/Avdelningen för bygg- energi- och miljöteknik

Abstract: Sub-Saharan Africa is the region in the world that suffers the most from poverty and its worst effects: hunger, lack of water and diseases. And the problem is not even decreasing: in the past years there has been a peak in undernourishment in the continent. Furthermore, according to ongoing research, the area is expected to be one of the most affected by climate change. A solution that tackles at the same time water scarcity, diseases, hunger and greenhouse gas emissions is urgent. Luckily, with the development in the past years of the solar photovoltaic and battery technologies, these solutions can now compete head-to-head with fossil-fuelled pumps. Indeed, the photovoltaic water pump (PVWP) is becoming the preferred solution for locals and NGOs, enabling a cheaper, less pollutant and more self-sustainable growth vector. In this thesis, a PVWP system is pre-designed. This means that the effect of the different variables over the system are studied, without aiming to design any specific system. However, the calculations are done with the climatic conditions of Fada N’gourma (Burkina Faso) as an example. To start, the importance of water for basic supply, sanitation and agriculture is researched through reviewing existing literature. The specific advantages of an advanced method of irrigation such as drip irrigation are also investigated. To continue, the analysis of the influence of each parameter intervening in the system is undertaken. First, a method to calculate the watering needs of the plants (through the concept of evapotranspiration), and simultaneously the passive self-regulation of PVWP systems for irrigation purposes is analysed. Second, the possibility to calculate faithfully the optimal angle with only climatic values and the size of the orchard is demonstrated. Third, a model to obtain the optimal diameter of the pipes through the optimisation of the cost is elaborated. The specific influence of the pump efficiency in this process is also explored. Fourth, an analysis on the effect in the system resilience to weather changes depending on the different starting dates for planting the crops is done. To finish, some considerations and a preliminary design are made. The option of implementing a storage system is discussed, with advantages of the batteries and the water tank. A quick economical evaluation done, leading to the conclusion that a PVWP system of the characteristics studied is viable under most of the circumstances.

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