Photovoltaic systems for improved domestic energy services in off-grid communities of developing countries. A techno-economic analysis of various photovoltaic systems for decentralized electrification in Sierra Leone.
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The access to reliable and affordable energy services needs to be improved for many of the developing countries to facilitate the alleviation of poverty. Photovoltaic (PV) systems can play a useful role in realizing that, since they are clean, safe, require little maintenance and have low recurring cost. This in contrast to its predominantly used alternatives: kerosene, dry cell batteries and home generators. The alternative of grid extension to peri-urban and rural areas is often financially unviable due to the areas’ remoteness and low load densities. The characteristics of a PV system make it a promising technology for decentralized electrification, although different barriers hinder its large-scale use. The barriers of high up-front cost, poor technical performance and unsuitability to the user needs are addressed in this study by designing the PV project according to the actual needs of the user and focusing on cost-effective technology. First, the relevant techno-economic assessments for PV project design are discussed through a literature study. Thereafter, these assessments are applied to a case study in Sierra Leone. A techno-economic analysis of various PV systems is performed to find the most cost-effective solution for a peri-urban community and two rural communities. Assessments concerning the solar resource, user energy demand and optimized system design are discussed. The resource assessment concerns satellite-based irradiation data, optimal inclination and an estimation of the system’s reliability. Energy demand is assessed through questionnaire based household surveys focused on energy use, expenditure, and service priorities. The energy use is relevant to grasp the picture of PV project impacts on consumption patterns. The energy expenditure concerns the user’s ability to pay for a PV system and is needed to approximate its affordability. In order to establish a PV system that is reliable on the long-term, the expected present and future load is calculated. Further, an optimized system design on the basis of cost-effectiveness is desirable to increase the project’s viability. A well-founded decision on technology selection is crucial in the PV project planning. The evaluated systems for the rural communities are the Pico PV system (1 – 10 Wp), solar home system (SHS) and solar charging station (SCS). These technologies are sized using analytical equations with a yearly average irradiation, and they are evaluated on their initial investment costs, annualized life cycle costs and cost of useful light output. A SHS and hybrid PV-diesel micro-grid are studied for the peri-urban community. These systems are both sized using a simulation-based Optimization Model for Distributed Power (HOMER) that produces hourly simulations of solar power supply and demand. The least-cost configuration of a power distribution system is computed using a Village Power Optimization Model for Renewables (ViPOR). Both systems are compared on their initial investment costs and annualized life cycle costs. For the rural communities, it was shown that the relative weight of up-front cost, reliability and lighting quality of the PV system determine the most desirable system in the project design. The SCS showed the most potential to supply reliable and affordable improved energy services to the rural communities. It demonstrated to have the lowest initial investment costs, while the Pico PV system showed the lowest annualized life cycle costs, with a limited reliability. The SHS and SCS can increase their reliability against limited incremental costs. The user is able to pay for all evaluated systems, except the SHS with reliability above 93% of the annual load coverage. The clear benefit of the SHS is the low cost of useful light output for the user. The system is costly, but supplies lighting of a higher quality. For the peri-urban community, the hybrid PV-diesel micro-grid showed For the peri-urban community, the hybrid PV-diesel micro-grid showed lower annualized life cycle costs compared to the SHS. However, reliable data on installation costs for both systems are important for further improvement of the analysis. The spread of the village, its terrain, the number of service connections and the daily load determine the cost-competitiveness of the hybrid micro-grid compared to the SHS. For a hybrid micro-grid, the break-even point of user fee and incremental cost for each service connection is important. The user’s ability to pay is relevant to estimate the feasibility of such connection fees. Besides, the use of optimization software for the distribution network increases the viability of the micro-grid. The micro-grid becomes more cost-competitive with increasing loads, because the power distribution network cost stays constant for an equal number of service connections. Once the scale benefits and a reduced system capacity for the micro-grid surpass the additional cost for the distribution system, an increase in load leads to a more cost-effective micro-grid compared to the SHS. The households classified as low are able to contribute fully to the annualized cost of both systems, for the present daily load. The middle and upper households would need to spend more than their substitutable energetic expenses in order to cover the annualized costs for both systems. Their willingness to pay more for a PV system will determine the interest in changing their energy supply system. An increase in capacity shortage for a SHS substantially reduces its system costs and makes them more affordable by the user. A desirable reliability level is ideally chosen based on people’s willingness to pay for reduced capacity shortage.