25 th International Conference on Electricity Distribution Madrid, 3-6 June 2019 Paper n°1874 CIRED 2019 1/5 TECHNO-ECONOMIC ANALYSIS OF NETWORK CONFIGURATION OF PV-BASED OFF-GRID DISTRIBUTION SYSTEM Iurii DEMIDOV, Antti PINOMAA, Andrey LANA, Olli PYRHÖNEN, Jarmo PARTANEN LUT University – Finland firstname.lastname@lut.fi ABSTRACT Only 15% of rural population in Sub-Saharan Africa has access to electricity. The focus in this study is on design and techno-economic analysis of low voltage (LV) distribution network configuration relying on PV- and energy-storage-based off-grid solutions for African rural conditions. In the paper, three different grid design approaches are studied for three real existing Namibian villages. As a result, the most economically and technically feasible and cost effective off-grid system configurations are defined case by case. INTRODUCTION Only 43% of population has access to electricity in Sub- Saharan Africa countries. This percentage goes rapidly down if we are talking about rural areas (15%) [1]. Moreover, 89% of electricity is generated by coal-fired power stations [2], even Africa is one of the most favourable places for the implementation of solar photo- voltaics (PV) energy production. According to the “World Sunshine Map”, it gets more sun days per year than any other continent in the world [3]. This paper consider Namibia as case study, a country in Sub-Saharan Africa, which has one of the highest solar radiation. Therefore, PV-battery-based off-grid system is one possible solution for electrification issue. Majority of the existing systems are either of two types: 1) solar house systems (SHS), of which power, typically, doesn’t exceed 100 W, and supply is a separated consumer; or 2) solar charging systems (SCS), which can have power rating up to 15 kW and is aimed as a rule to phone charging [4]. However, these systems are not intended for uninterrupted power supply that meet the power quality requirements [5]. In order to guarantee such requirements, there is a need to design a common off-grid power system, to which each consumer is connected to, which is sourced by a PV power plant, and backed up by a battery energy storage system (BESS). Typically, off-grid systems consist of components mentioned above. Besides these, there are power electronics (converter/inverter) for voltage transformation and power lines for power delivery. Proposed off-grid system design starts from sizing of the PV array. The descriptions of PV plant and sizing methodology are presented in [6]. In order to maximize PV plant output power, a maximum power point tracker (MPPT) is applied in all modern solar power systems. Characterization of the devices has been presented in [7]. Authors in [10] describe power electronic implementation for off-grid power system. Next step in off-grid system design is battery energy storage system (BESS). BESS provides energy and power in the absence of the sun, including the operation during the night time. Detailed description of the BESS dimensioning is presented in [8]. Based on parameters presented in [9], lithium-ion batteries are found feasible and chosen for the BESS of the concept. Due to safe and efficiency issues, low voltage is chosen for proposed off-grids. There are three different power distribution network configurations compared in the paper:  DC distribution, which presupposes usage up to three voltage levels: main feeder line voltage, distribution network branch voltage (120-1500 VDC), and consumer premise network voltage (48 VDC) [11] (Figure 1a).  AC European 230 VAC distribution [IEC 60038, IEC 50160, CEN-ELEC HD 472 S1], assuming one or three phase and up to two voltage levels: main feeder line and branches (Figure 1b).  AC American 120 VAC distribution [ANSI C84.1-1989], implying two voltage levels: main feeder line with one or three phases and branch voltage level with split-phase configuration (Figure 1c). The goal of the study is to determine the most cost- efficient configuration of the off-grid system. Three real existing Namibian villages, as cases, are considered in the paper. In addition, concept design includes such the key things as modularity, plug&play, scalability, and affordability. This allows interconnecting and scaling the off grids together in a long-term perspective. OFF-GRID DESIGN METHODOLOGY Research concept descriptions The paper considers three different network configurations based on geographical analysis of customer premises in selected villages of regions in Namibia; dense rural grid, scattered rural grid and dense city grid. Within each topology, distribution network configuration, including different voltage levels, is considered: 1) bipolar low- voltage DC distribution with voltages from 48 to 1500 VDC, 2) European AC 230 VAC distribution and 3) American AC 120 VAC distribution. In addition to different topologies and configurations, rising load capacity of the consumers is assumed and considered in