Hydropower Production And Plants In Uganda
Hydropower
Hydropower is a renewable source of energy where power is derived from the energy of moving water from high to lower elevations. In order to convert this potential to applicable electric energy, water flow should be led to and drive a hydraulic turbine, transforming hydro energy into mechanical energy, the latter again drives a connected generator transforming the mechanical energy into electric energy. It is a proven, mature, predictable and price competitive technology. Hydropower has the best conversion efficiency of all energy sources (about 90%). It also has the highest energy payback ratio due to low operational costs and long lifespan. Being a renewable energy source that never can be exhausted, and that avoids the pollution associated with the burning of fossil fuels, makes hydropower a very attractive energy alternative.
A hydropower plant is an impoundment facility usually a large hydropower system, uses a dam to store river/stream water. Currently, Uganda has an installed hydropower of about 685.5MW (over 80% of the total installed power currently) with the bulk provided by Nalubaale 180MW, Kira 200MW and Bujagali 250MW. Mini hydropower plants (Mpanga 18MW, Bugoye 13MW, Ishasha 6.5MW, Nyagak 3.5MW, Kilembe Mines Limited 5MW and Kasese Cobalt Company limited 9.5MW) account for the remaining percentage.
Several hydropower plants are planned for installation and these include; Karuma 600MW, Ayago 610MW, Isimba 140MW, Oriang 390MW, Kalagala 330MW, Kiba 290MW, Murchison 690MW and several other mini hydropower plants.
Hydropower Production
Hydropower plants convert the kinetic energy contained in falling water or potential energy contained in stored water into electricity. Water goes through a turbine that converts water’s energy into mechanical power. The rotation of the turbine is transferred to a generator that converts mechanical into electricity.
Advantages and disadvantages of hydropower
Advantages
- A big hydroelectric advantage is the ability to quickly and readily vary the amount of power generated, depending on the load presented at that moment.
- It utilizes water, a renewable energy source as “fuel”
- The power generation process is environmentally clean (relatively low or no emissions).
- Hydropower plants are characterized with long lifetime and high reliability.
- Low operational costs.
Disadvantages
- It requires large initial investments (excavation and earth movement), this leads for long payback time.
- It may involve social and environmental negative effects especially for large scale schemes e.g water pollution, displacement of people, alteration of the natural flow of rivers, among others.
- It involves use of long transmission lines which leads to high power losses.
- It requires long construction time especially for large-scale plants.
Classification of Hydropower Plants
As there are no hard and fast rules to classify hydropower plants, some of the basis are as follows.
- Based on Hydraulic characteristics.
- Based on Head.
- Based on capacity.
- Based on turbine characteristics.
- Based on load characteristics.
f)Based on interconnection.
Hydropower Plant Based on Hydraulic Characteristics
a) Run of river plant (Diversion plant): The hydroelectric plant is built directly in the river since the flow rate and drop of water are consistent. Practically, water is not stored during flood and low electricity demand periods, hence there’s wastage of water. Seasonal changes in river flow and weather conditions affect the plant’s output, hence it is in limited use unless interconnected in grid. During good flow conditions, the plant supplies base load and during low flow conditions, the plant supplies peak load.
b) Canal based sites: these are plants that utilize the drops on existing or proposed canals. The energy generated by water flowing through the canal fall (located in the canal) is tapped for power generation. The Powerhouse is located at the main canal or a bye pass canal is constructed where the powerhouse can be located.
c) Storage (Impoundment) plant. This is the most common type of a hydropower plant. It involves the construction of a reservoir/dam across the river. The storage of water takes care of the fluctuations of water supply during flood and dry periods as well as during load fluctuations, hence it can supply electricity more consistent than any other plant.
d) Pumped storage plant. Water is used for generation of power during peak demand, while same water is pumped back in the reservoir during off peak demand period, when adequate power is available for this purpose. If a turbine used is reversible, it can be used to pump back the water, otherwise a separate pump is used.
e) Tidal Plant. A tide is a periodic rise and fall of water level of the sea due to gravitational attraction between moon and earth and sun and earth. Regions which come nearer to the moon are subjected to high tide and regions which are away from moon are subjected to low tide. The level difference between high tide and low tide is called Range of Tide, which is responsible for power generation.
