Optimal Sizing of Grid-PV Hybrid System for Ethio Telecom Access Layer Devices and Its Economic Feasibility
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Date
2017-06
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Addis Ababa University
Abstract
In Ethiopia, conventional grid power is primary source for base stations with backup from diesel
generator and/or battery. Unstable diesel price; huge expenses of fuel and its transportation; and
high carbon emissions are the main problems associated with fuel energy. Mindful of these facts,
countries move to renewable energy sources. The work behind this paper is to determine the
optimal size of grid connected solar power system for powering base stations and compare its
performance with the existing system.
The study included 138 base stations that are found in Addis Ababa. They are categorized in to five
based on their technology – GULC, GUC, GUL, GU and UO. To estimate the size of PV module, real
time power consumption data was collected from ethio-telecom Network Operating Center (NOC)
for a period of about one year (Dec. 01, 2015 to Nov. 30, 2016) - 7,860 records for each site. In
addition, hourly metrological data, specifically global horizontal, diffuse solar radiation,
temperature and wind speed, were collected from National Metrological Agency. The proposed
hybrid model comprises of PV-Grid-Battery. This project employed linear programming as
optimization method and MATLAB program was used to compute hourly DC electric power output
and to solve the developed optimization model.
The finding showed that the highest power consumption was nearly 6KWs in GUC and GULC
technologies, while the lowest was found to be in UO technology – around 1 KW. The number of PV
modules in the hybrid system for UO technology is lower, which shows it can be implemented in all
areas; while the other two technologies, GUL and GU, required green field /outdoor base stations.
In addition the simulation output revealed that the system automatically chose the grid in case
where subsidized/current cost of electricity was considered, while the model builds PV system to
supply its energy need when the real electricity cost was utilized. This implied that PV’s economic
competence was hindered by local policy. Moreover, life cycle cost comparison of PV and DG
showed that photovoltaic systems are more economical than diesel generator systems.
As this evidence has several ramifications, it is better to promote PV to be used in any power design
of BS. Promoting competitive PV market is also important to avail sufficient generation capacity to
cover the local need.
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Keywords
Grid-PV Hybrid System, ethio telecom Access, Economic Feasibility, Optimal Sizing