POTENTIALS OF SMALL HYDROPOWER SYSTEMS FOR RURAL ELECTRIFICATION IN SUB SAHARA AFRICA
1.1 INTRODUCTION
Sub-Sahara Africa accounts for 75% of the world’s population without access to electricity (Tracking SDG 7: The Energy Progress Report, June 2021). To improve rural electrification and enhance sustainable development, other renewable energy sources need to be considered. Renewable Energy sources such as Hydropower, Wind, Solar, and Biofuel are important technology options for rural electrification projects and for reducing greenhouse gas emissions.
According to the International Energy Agency Net-Zero by 2050 report, the world will need 2600GW of hydropower capacity by mid-century to have a chance of keeping global temperature rises below 1.5 degrees Celsius. Off-grid systems that make use of small hydropower plants could be deployed to decentralize power generation through creating autonomous power plants for the Sub-Sahara Africa region. Small hydropower system is a renewable energy technology that generates electricity capacity not more than 10MW. It can either be run-of-water systems or integrated into existing water infrastructure without the construction of a reservoir or dam hence, the negative environmental impacts such as ecological disruption, flooding, methane emissions associated with large-scale hydro projects are drastically reduced. Due to its versatility, low investment costs, and as a renewable energy source, small hydropower is a promising option for producing sustainable and inexpensive energy in rural areas of Sub-Sahara Africa.
Rural electrification through grid extension can be expensive and technically challenging to transmit electricity through long distances resulting in transmission losses. Small hydropower systems can be installed with other off-grid renewable energy sources to support diverse energy requirements for communities and small-scale industries in remote areas and optimize harnessing the available local renewable energy sources for power generation. There are possibilities to link small hydropower to other uses like irrigation in Agriculture. This can reduce the investment costs for individual users, thus expanding the chances of income generation and development.
1.2 PRINCIPLE OF HYROPOWER GENERATION
Hydropower is a function of two factors, which are Head and Flow. Head refers to the height of the slope over which the waterfalls, while Flow refers to the volume of water per unit time. The basic hydropower principle is based on the conversion of a large part of the Head into mechanical and electrical energy. Hydraulic turbines harness the water pressure to convert potential energy into mechanical power, which drives an electrical generator. When electricity is generated, the powerhouse where the generator is located transfers the electricity to a step-up transformer, which is then transmitted to the grid sub-station or to the region where the electricity is to be used. Once electricity is produced, the water flow is returned to the river. To maximize production, both head and flow should be high. Small hydropower is a site-specific technology and as such not all locations on the river flow course are ideal for development except those that have considerable sizes of head such as sloping sections of the river and natural falls. Meaning most of the potential sites for small hydropower should be in mountainous areas with perennial rivers. The presence of perennial rivers and mountainous areas are in central, eastern, and some southern parts of Africa. The power exploited from hydropower at a particular site is proportional to the product of flow rate and head as shown below;
P = ղo ρgQH
Where ρ is the density, g is acceleration due to gravity (m/s2), Q is the flow rate (m/s2), H is the net head available at the inlet to the turbine (m) and ղo is the overall energy conversion efficiency. The values for overall efficiencies are higher in large-scale hydropower than small hydropower because the systems are designed with relatively high levels of precision and accuracy. Flow rate and head fix the energy potential in a site therefore, there is a limit to what hydropower could be utilized at a particular site and once this is reached, further power expansion is not possible.
1.3 SOCIO-ECONOMIC AND ENVIRONMENTAL ASPECTS
- Proper utilization of water resources such as small creeks, streams, or rivers can generate and supply energy. The Sub-Sahara region can enjoy local sources of energy without large storage of water, reducing the social and environmental impacts on the population.
- Small hydropower with the absence of a reservoir reduces investment cost per KW of installed power
- The small hydropower technology is a long-lasting and robust technology- the life span of a well installed system can last up to 50 years without part replacements thereby reducing maintenance cost (O. Paish, “Micro hydropower status and prospects,” Journal of Power and Energy, 2002)
- The system can be designed and installed using local resources thus creating job opportunities and providing an ability to use the technology to advance the standard of living in the region.
1.4 CHALLENGES AND RECOMMENDATION
- Most countries in Sub-Sahara Africa lack complete and updated data on the National inventory of potential sites for installation of small hydropower, therefore depending on feasibility studies conducted by international agencies. This could be resolved by creating opportunity for trainings and partnerships with small hydropower regional centres such as the Abuja regional centre instituted by United Nations Industrial Development Organisation (UNIDO) to improve the local capacity in conducting feasibility studies.
- Turbine parts and generators are imported, resulting in the parts being expensive due to some added costs of transportation and taxes. This is one of the barriers to the development of small hydropower installations in the Sub-Sahara region. Adequate skills and resources that can manufacture the parts locally would resolve this problem.
- Limitation of small hydropower innovation in most Sub-Sahara countries as compared to developing countries. This is due to limitations in research and training in the technology in higher institutions. This can be resolved by Government-funded research and technology development centres in the region.
1.5 CONCLUSION
Small hydropower can supply clean and affordable energy as it can be constructed in areas where there is enough flow and head to make energy generation viable in rural or undeveloped areas. It can be integrated into existing water infrastructure, resulting in no land acquisition or significant operating cost. The generated electricity can be used in water supply systems with excess electricity sold to the Government. The inclusion of this technology in the energy mixes could lead to sustainable development.
Picture credit : Enviroinc
Author : ETUMUKA AMAMIZE
