The Role of Mini-grids in Rural Electrification Programmes in Africa and beyond:“The State of Art Paper”

During the last two decades,there has been an outcry on how the shortage of power in rural areas can be sorted.Most Developed Countries(MDCs)like the USA,China,German,UK,Taiwan,and Singapore started using renewable energy sources to minimize power shortages in rural areas.Less Developed Countries(LDCs)mostly African countries also followed suit.This was not only to solve the power problem but also to be on the safe side after researches anticipated that in the near future,fossil fuels would be depleted.Over 50 years ago,several countries have attempted to harness power using hydro-power,biomass,solar,tidal,wave thermal,and wind energies.Different researches show that hydro-power has been most developed worldwide due to high levels of investment.Of recent,solar and biomass energies have come on board steadily,gaining trust from people.This still has benefited towns’more than rural areas due to transmission barriers,expected financial returns,and high cost of maintenance.Recently,there has been encouragement and development of solar PV systems and the utilization of mini-grids for rural electrification to minimize the challenge,especially in African countries.International Energy Agency(IEA)has high expectations in mini-grids in playing a significant role in rural electrification.Mini-grid energy solutions are emerging as the next best alternative to rural electricity access coming between the option of large-scale grid extension and solar home systems.This paper,therefore,has discussed the status,Strengths,Weaknesses,Opportunities and Threats(SWOT)strategies,financing options,risk management systems and current trends in renewable energy mini-grid development in Africa and beyond in an attempt to enhance rural electrification.This research used secondary data,internet resources,published data,and World Bank reports to synthesize the evolution and the update status of mini-grids.

Design of a Photovoltaic Mini-Grid System for Rural Electrification in Sub-Saharan Africa

This paper presents a detailed design of a photovoltaic (PV) system for use in the rural electrification of remote settlements that are far off from the electricity grid. Since investment in building transmission lines from the grid to these localities is not viable, a good solution is an installation in these areas of standalone photovoltaic systems. The design process comprises the choice and dimensioning of the solar panels, the battery storage, DC-AC inverter, and mini transmission grid to the different homes. The design is for a 15 kW PV system including an economic evaluation and analysis using Hybrid Optimization of Multiple Energy Resources (HOMER) software. Data on the average monthly solar radiation and temperature were obtained from various sources, including, Photovoltaic Geographical Information System (PVGIS) for Africa. From this data the study area receives a monthly average solar insolation of 6.16 kWh/m2/day with the worst month being August with 5.22 kWh/m2/day. The total daily electrical energy consumption is estimated to be about 72.525 kWh. Simulation results using HOMER software shows that the overall capital cost of the PV system components is $122,337, a replacement cost of $12,889 and an operation and maintenance cost of $29,946 over 10years. A financial analysis of the system showed that the design was both viable and sustainable with low maintenance cost.

A Virtual Synchronous Machine to Support Dynamic Frequency Control in a Mini-Grid That Operates in Frequency Droop Mode

This paper addresses the problem of dynamic frequency control in a diesel-based mini-grid. It is shown that a virtual synchronous machine (VSM) can support dynamic frequency control by adding virtual inertia and damping to the system. However, it is found that the typical formulation of damping power does not work properly when the grid forming gen-set operates in droop mode because of the unknown stabilization value of the grid frequency. As a solution to this problem, an estimator for the stabilization frequency that works in conjunction with the damping function of the VSM is proposed. Theoretical and experimental results provide evidence of a satisfactory performance of the proposed VSM with estimator for different values of the gen-set droop factor. The estimated stabilization frequency converges in approximately 2 s and the maximum frequency deviation during the transient is reduced in 34%, on average.

Impact of Sustainable Electricity for Cameroonian Population through Energy Efficiency and Renewable Energies

Access to electricity and a reliable supply of energy are essential elements of local economic development and poverty reduction. To address these challenges, appropriate policies and mechanisms at the national and regional levels need to be implemented. In this study, we used Johanson cointegration and Granger causality techniques to examine the different cointegration and causal relationships that exist between the growth of electricity consumption (CE) and socio-economic parameters (GDP, tertiary GDP, GDP per capita, number of households, number of subscribers and population) in Cameroon during the period from 1975 to 2011. The results from the software Eviews 7.2 show that there are cointegration relationships between electricity consumption and socio-economic indicators (LGDPH, LPO and LS) thus reflecting the long-term relationship between socio-economic growth and electricity consumption (CE). Consumption growth could, therefore, follow socio-economic growth. In addition, the analysis of the Granger causality test results reveals that there is a unidirectional causal relationship of macroeconomic indicators towards electricity consumption. That is, LGDPG to LCE, LGDPH to LCE, and LGDPT to LCE. There is also a unidirectional relationship between LCE and the demographic indicators that is the relationship of LCE to LS (number of subscribers). We can, therefore, conclude that the indicators that have a better influence on electricity consumption are the overall GDP for the macroeconomic indicators and the population for the socio-demographic indicators respectively. In addition, the analysis of renewable energy potential (EnRs) shows us that Cameroon enjoys good irradiation throughout its territory, hence its high solar potential. The wind speed is unevenly distributed over the territory, it has an average speed in the region of the very north of the country, but a low speed in the rest of the territory, which justifies the low wind potential in the country. We also noticed that the forest is concentrated in the southernmost part of the country, mainly in the eastern and southern regions. After study, we concluded that it is possible to truncate thermal power plants with renewable energy plants. We proposed to trade the thermal power stations of additions by biomass plants. We also offer hybrid solar-biomass power plants for isolated power plants;and solar-wind hybrid power plants for the Far North region of the country, given its strong wind power potential. We also identified the sources of over-consumption and estimated the amount of energy that could be saved by developing an energy efficiency plan (10%) with the standard scenario that would take into account good energy-saving practices. We then estimated at 336,938 Kg the gain in CO2 emissions if we exchanged the thermal power stations into EnRs. Recommendations are then suggested for the successful implementation of an energy efficiency plan and implementation of renewable energy in Cameroon.

Virtual Synchronous Generator: A Control Strategy to Improve Dynamic Frequency Control in Autonomous Power Systems

Ideally, diesel hybrid autonomous power systems would operate with high penetration of renewable energy sources such as wind and photovoltaic to minimize fuel consumption. However, since these are inherently intermittent and fluctuating, the grid-forming diesel engine generator sets are usually required to operate with larger amounts of spinning reserve, often at low loading conditions what tends to increases operating and maintenance costs. Frequency stability is of great concern in “small” systems, such as mini-grids, where any individual generator in-feed represents a substantial portion of the total demand. There, the initial rate of change of frequency is typically larger and a lower value of frequency can be reached in a shorter time than in conventional systems with all generation supplied by rotating machines, possibly resulting in under-frequency load shedding and tripping of renewable energy generators. The first part of this paper, discusses some general concepts regarding frequency stability in a diesel hybrid mini-grid and how energy storage systems can be used to enhance system performance. Then, a particular technique based on a virtual synchronous generator is presented and its effectiveness is demonstrated with simulation results.

Nigerian Wood Waste: A Dependable and Renewable Fuel Option for Power Production

Being an oil-rich country, Nigeria’s energy supply is primarily fossil-based. The unequal distribution of oil wealth, along with agitation for self-determination and resource control, has led to the sabotage of oil installations. This, in turn, has affected all services running on the energy supply from these installations, leading to incessant or total shut-down of such facilities. Power generated using biomass-based renewable energy technologies is a promising option in limiting the country’s dependence on fossil energy for power generation. The most important part of this option is on-site power generation via mini-grid systems. The power thus produced is utilized with the excess being fed into the national grid based on Feed-in-Tariff (F.i.T.) requirements and technicalities. The important factors to be considered in the propagation of a mini-grid option are examined in this study. Furthermore, the study shows that about 1.3 TWh of electricity can be generated from the 1.8 million tonnes per year of wood waste produced by the lumber industry in Nigeria. Power generation through the utilization of biomass has however proved to be a possible path in achieving economic, social and environmental sustainability in the country. Economic studies show that for small-scale power generation, internal combustion engines and Stirling engines are economically feasible. Steam turbines and gas turbines are mostly used in medium/large-scale biomass power generators, especially in proximity to biomass waste resources. Micro gas turbine power technology can also be applied on a small scale despite its high total investment capital.

Inverter-Based Diesel Generator Emulator for the Study of Frequency Variations in a Laboratory-Scale Autonomous Power System

This paper presents the modeling, simulation and practical implementation of an inverter-based diesel generator emulator. The main purpose of this emulator is for the study of frequency variations in diesel-based autonomous power systems in a laboratory environment where the operation of a real diesel generator is not possible. The emulator basically consists in a voltage source inverter with a second order output filter which voltage references are given by the model of the diesel generator. The control of the emulator is based on the digital signal processor TMS320F2812, where the mathematical models of the diesel generator and the control of the inverter are computed in real-time. Parameters for the model were obtained from commercially available components. Experimental results for different values of speed droop showed that the emulator achieves a satisfactory performance in the transient and stationary response. For the stationary response, the measured frequency deviates from theoretical values with a mean absolute error of: 0.06 Hz for 0% droop, 0.037 Hz for 3% droop, and 0.087 Hz for 5% droop. For the transient response, the measured frequency nadir deviates from simulations in: 0.05 Hz for 0% droop, 0.02 Hz for 3% droop, and 0.1 Hz for 5% droop.