Even if renewable energy generation is improving and diffusing rapidly, reliable energy access is still a major issue for a consistent part of the global population, with more than 1 billion people still lacking energy access globally. The vast majority of this share of population is living in remote rural areas of developing countries, experiencing major issues in terms of living conditions. While consistent efforts have been done in the past decades to solve the problem, still a lot of work has to be done and novel approaches need to be implemented.
In the past, most of the new energy connections were achieved through national grid extension, which is proving to be a non-adequate short-term solution for a consistent share of the remaining part of the population living in rural areas. This is the reason why decentralised solutions, such as Solar Home Systems and DC micro-grids, are becoming more appealing as alternative ways to improve energy access in developing countries.
In this framework, this Master's thesis will focus on DC solar micro-grids as a solution to the energy access problem. More specifically, the aim will be to develop a methodology to gather, process and analyse data, for planning and evaluation of remote DC micro-grid networks in rural areas of developing countries. One of the main novelty aspects of this proposed methodology is the integrated implementation of Geographic Information Systems and concepts derived from the mathematical field of Graph Theory, together with an electrical analysis.
The methodology is clearly divided into three consecutive steps. The first step focuses on gathering and processing ground-level data using GIS, to compare different micro-grid layouts in term of geometrical length. The second step consists of a graph theory-based dual-objective optimisation algorithm to design meshed micro-grids from a set of starting topologies. The third step implements a DC power flow tool to analyse the operational behaviour of the optimised layouts. The proposed methodology is explained in detail throughout the report, with an example of its application to a sample of villages in different world-wide locations.
The results of this first application of the proposed methodology allow to draw some conclusions on the methodology itself and on the comparison of different micro-grid topologies. First of all, the huge potential of the combination of GIS tools and graph theory applied to micro-grid planning is shown. The results of the layout comparison show how typically implemented micro-grid layouts are generally outperformed by micro-grids designed using novel concepts and this integrated approach. Nonetheless, each specific case studies has peculiar characteristics and conditions that need to be taken carefully into account and can lead to totally different kinds of optimal solutions. It is hence of vital importance to have a methodology which is at the same time well-structured and flexible to adapt to changes and modification of parameters in order to perfectly reflect the specific needs and characteristics of each different rural electrification project.
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To this day, 16% of the world’s population still has little or no access to electricity. The majority of which is located in rural regions of developing countries, such as India and most countries in sub-Saharan Africa. As a part of the Sustainable Energy for All (SE4All) initiative, a multi-tier framework that aims to categorize and quantify the electricity access of households and rural regions to reach the sustainable development goals by 2030. Solar Home Systems (SHS) is a potential solution that has emerged to cater for the lighting and power needs of these remote households. SHSs consist of a small stand-alone DC system which are composed of a PV array, battery, and power electronics that are designed to meet the load of a single household. The aim of this study is to propose a universal, optimal sizing methodology for the SHS with respect to cost, reliability (LLP) and battery lifetime for any household in the mutli-tier energy ladder. Moreover, the study aims to anticipate to which extend a stand-alone architecture remains a feasible solution. In this thesis, a practical model for each of the Solar Home System components was built using MATLAB, then two optimization methods: a classical iterative method, and the Genetic Algorithm, an evolutionary method were used to perform a multi-objective optimization on three case studies in different locations. The results obtained showed that for the lower energy tiers, with a load profile up to a peak load of 155W, the standalone approach is optimal. With an LLP·2%, an average total upfront cost of 1600$, and a lead-acid battery lifetime of 6.5 years. The results from the higher tiers however show proved that as the household moves up the energy ladder, the stand-alone approach becomes unaffordable and less reliable. An alternate approach to solve this issue was examined, where several households are interconnected forming a minigrid to share their energy generation and load. The outcome of this study showed that households with sub-optimal sized Solar Home Systems were able to greatly increase their system reliability, the LLP was recorded to drop by up to 50% in some scenarios with an increasing number of interconnected households. The LLP drop however reached a saturation point beyond 25 households. On this basis, it is recommended that further work should be done to increase the complexity of the component models, notable the battery. Moreover, a more extensive study should be conducted on the interconnected approach, with a multitude of scenarios to optimize the system size in a mini-grid architecture. ... Read more

Access to electricity still lacks for a fifth of the world's population. Most of the areas are in the remote rural location. Due to the off-grid location, policies, and other social factors, the grid expansion in these areas is not economically viable. Installing Solar Home Systems (SHS) is considered to be a promising immediate solution, given that most of these areas are in the tropical region where it has the highest sun-hours in the world. SHS consists of PV modules for the energy generation, batteries for the energy storage, converters for the energy conversion, and load appliances for the energy consumption. However, its high ambient temperature can potentially harm the SHS in decreasing the performance and shortening the lifetime. The lower performance and lifetime can directly translate to have high capital expenses. Therefore a precise quantification of the performance and the lifetime is essential to all the stakeholders.

This thesis aims to evaluate and quantify the influence of temperature on the performance and the lifetime of SHS. To achieve the research goal, an integrated SHS model is proposed by considering the performance and the aging behavior of both PV modules and the batteries. Two different battery technologies: Li-ion and Lead-acid are involved in the evaluation. Moreover, the analysis was conducted for Sumba Island, Indonesia since it has great solar potential and also the potential market for the SHS. Furthermore, this work presents a comprehensive investigation of temperature impact from the PV module and battery component level to the system level.

Initial system design has been performed in which it requires a 330 Wp PV module, with a tilt and azimuth angle of 11 degrees and 6 degrees respectively, and 960 Wh of batteries to achieve the LLP of 9.5%. The simulation result of the PV component showed clearly that the PV energy yield reduces due to the higher ambient temperature is used. As for the battery, there is a converse behavior concerning the temperature impact in which an increase in temperature gives a positive effect on the capacity and internal resistance in the short term. However, in the long run, it has a severe aging rate.

By combining PV module and battery element in an integrated SHS model, it is shown that it achieves to have a 7.4% lower LLP compared to the initial sizing. However, as the aging plays a part, the LLP increases exponentially over the years and can achieve almost doubled the initial LLP. As the ambient temperature increases, it brings negative impacts for the SHS in terms of the performance and the lifetime. It results to have even higher LLP. A decreasing trend of battery lifetime is observed as the ambient temperature increases. Furthermore, it is seen that the system lifetime is limited by the battery lifetime. ... Read more

Nowadays, there are still some regions in developing countries lacking electrification. A solution to electrify thehouseholds in these areas with off-grid Solar Home Systems (SHS) has been proposed for some time. However,battery storage in SHS is always the limitation in both cost and lifetime point of view. Thus, a battery withstable behaviour, longer lifetime and less maintenance as well as a lower price is highly desired in SHSs. Withthe narrow choices on economical commercial battery technologies, there is another approach to improve thebattery behaviour in SHSs.This thesis is aiming at exploring a solution from usage perspective to maintain the battery behaviour in long-term, in SHSs. In order to achieve the goal, a tool and a method were proposed to provide a practical solutionfor battery performance preservation in SHSs.In this study, two battery technologies which are commonly applied in SHSs were explored: the LiFePO 4battery and the Valve Regulated Lead-acid batteryFirstly, an accurate battery dynamic model based on the electrical equivalent circuit was constructed for bothbattery technologies separately. Series of experiments were performed to obtain the relevant parameters. This model was built for low current applications, which is lower than 1 C, typically suitable for SHS applications.This model was on battery cell level and with a great accuracy with a < 2% errorSecondly, a performance based battery lifetime prediction model was built, and the battery capacity wasselected as the index of the ageing process. The modelling was achieved by applying a new concept, which isthe rate of normalised capacity fading, with respect to capacity throughput. Another series of experiments wereoperated for the exploration of the relationship between stress factors and the rate of battery ageing. Theexperimental data is the foundation of the battery lifetime model.Thirdly, a usage guideline for each battery technology was proposed by analysing the lifetime test data. Thenone practical usage guideline application method was simulated. The application of the usage guideline has anoticeable improvement in the battery behaviour in long term scale.In conclusion, the modelling of the battery including both dynamic behaviour as well as lifetime predictionprovides a tool for future exploration. With this tool, the design and sizing of the battery storage system, as wellas the management of appropriate battery usage in SHS would be easier. The method proposed for batterycapacity preservation is the usage guideline. The usage guidelines offered wide choices on user sideimplementations regarding battery capacity preservation. ... Read more

1.3 billion people in the world lack access to electricity (International Energy Agency (2013). The largest share of this group is poor and lives in the developing world, and has to deal with unmet basic needs. Having the possibility to use reliable and clean energy is seen as a driver for social development and environmental sustainability. Having access to energy is also often linked to economic growth and has a positive impact on health. (Gradl & Knobloch, 2011) Improving energy access is therefore a hot topic worldwide. With a Solar Home System (SHS), energy can be generated and used on a household level at places where the electric grid does not reach. The main components of a SHS are a solar panel for the generation of electricity, a battery for energy storage and balance of system (BoS) components, including power electronics, to coordinate the flows of energy. SHS are offered by multiple companies worldwide, and come in various configurations. The smallest SHS are capable of powering for example LED lights, phones and/or a radio, while larger SHS can power for example televisions and fans. Generally speaking, SHSs are increasing in size. This is due to dropping prices of system components. Where in 2003 a SHS of 20 Wp was economically competitive with kerosene lamps, in 2015 this was already 70-80 Wp. (Chattopadhyay, Bazilian and Peter Lilienthal, 2015) The conventional technologies are likely to dominate the SHS the upcoming years. Proven technologies are favourable as reliability is key for SHSs. This means that most of the SHSs in the future will rely on crystalline silicon panels and lead-acid batteries. In the future, li-ion battery technologies will become competitive as prices are dropping... ... Read more