SONDU/MIRIU HYDRO-ELECTRIC POWER PLANT

SONDU/MIRIU HYDROPOWER PROJECT- A BRIEF INTRODUCTION The Project is the first major hydro power project located in Nyanza Province about 60km south of Kisumu City alongside Lake Victoria. On completion, the power station was expected to have a maximum capacity of 60 MW from two units and an average annual energy production of 330.6 GWh. The feasibility study for the Sondu-Miriu River Hydropower Project was undertaken in 1985. At that time, the hydropower development was proposed as a component of an overall basin development programme that included the Magwagwa Multi-purpose Dam and the Kano Plain Irrigation Project. This multi-purpose programme depended on the construction of a large flow regulating reservoir at Magwagwa and would have resulted in major changes in the river flow regime, diverting water to another basin. However, this multi-purpose programme was not implemented. Water was diverted from the Sondu river at the Intake through a 6.2 km long tunnel constructed under phase I of the project. A surface mounted penstock will then take the water down the Nyakach escarpment to the Power Station below. In the Powerhouse, harnessing the water and the head, the turbines are turned to generate the electricity. The water is then returned to the Sondu river approximately 13km downstream of the intake via a 4.7km long Outlet Channel. A new Transmission Line approximately 50km long will be constructed under the SMHPP to connect the Power Station to the Kisumu substation.   AIMS OF THE COMPANY The plant is owned and maintained by KenGen whose objectives are: 1. To be an employer of choice to thousands of people and give back to the communities in which they operate in. 2. To be market leader in the provision of reliable, safe, quality and competitively priced electric energy in the Eastern Africa region. 3. To efficiently generate competitively priced electric energy using state-ofthe-art technology, and skilled and motivated human resource to ensure financial success. 4. To achieve market leadership by undertaking least cost,environmentally friendly capacity expansion. Consistent with their corporate culture, core values will be adhered to in all their operations.   PROCESSES Hydro-electric power generation in Sondu Miriu. Unlike the other major hydropower projects in Kenya, the Sondu-Miriu Project does not have a major dam and associated reservoir but relies on the flow of the river with only a small storage capacity at the Intake. Hence Sondu-Miriu is not a dam but a weir, water is diverted to the power generation house and returned to its normal stream after generation. Some water is diverted to the power station via the intake tunnel while the rest is usually left to flow downstream into the original course of the river. There is on-going construction of a tunnel 6.2 km long and 4.2 m in diameter. This takes the water to the top of the Nyakach Escarpment. In addition, there is the penstock construction at the top of the Nyakach Escarpment and take the water down the escarpment, a fall of approximately 200m to the Power Station to be constructed below. The water is then taken back to the original river, approximately 13km downstream of the Intake, by a 4.7 km long and 2.6 m bottom wide outlet channel. The electricity will be distributed via a new transmission line to the Kisumu Substation. A 49km transmission line of 135 kV is also to be constructed under the project. There is a control room at the intake facility where the gates are controlled to regulate the run-off. The intake facility has the following structures a) Intake weir- This is the overall water retention structure used. It is blocked by gates which are controlled to regulate run-off. It is 70m in width and 18m in height and has three 15m width and 10.6m height fixed wheel with 4.0m width and 1.85m height flap gates. b) Siltation bay- The siltation bay is built in a slanting manner, such that silt settles at the bottom, after a period of time, the sand flushing gates are opened to drain the sand. These gates are controlled by a programmed simulation. The programme controls the three spillway gates and one sand-flushing gate. c) Trash rack- This is used to fish out any floating debris on the water. There are two 5.0 m width and 9.0 m height inclined type trash racks used for this purpose. d) Just before the start of the pentstock is the surge tank. The purpose of a surge tank is to neutralize rises and falls in pressure to prevent system failures, blowouts as well as to quickly provide extra water during a brief drop in pressure along the pentstock. It is attached at the highest point of the system. When pressure rises, forcing fluids upward, they shift into the tank rather than blowing out the pentstock. e) The pentstock- A penstock is a channel used to feed or carry away water. The flow of the water through the penstock can be controlled with a sluice or gate that is raised and lowered. It’s dimensions are: diameter- 3.6 m in tunnel, 3.6 m, 3.4 m and 3.2m at inclined surface section, 2.2 m and 1.65 m after spherical branch; length- Total 1,214.33 m consisting of 53.0 m, 1,139.13 m and 22.20 m in tunnel and at inclined and horizontal surface sections. The general electricity production technique in the powerhouse is as follows: i. Turbines- This has propellers which are turned round by the onrushing water from the pentstock. The turbine is connected to the generator by a shaft which rotates due to the propellor rotational force. It provides a coupling for the generator which it is connected to. ii. Generator-(Check image below) This is the power producer. When the turbine converts thhe energy of flowing water into meechanical water, the hydroelectric generator converts thisenergy into electric energy. The operation of the generator is based on the Faradays principles. When a magnet is moved past a conductor, it causes electricity to flow. The electromagnets are made by circulating direct current through loops of wire around stacks of maagnetic steel laminations. These are called field poles and are mounted at the perimeter of the rotor. The rotor is attache to the turbine shaft and rotates at a fixed speed. When the rotor rotates, it causes the field poles (the electromagnets) to move past the conductors mounted on the stator. This, in turn, causes electricity to flow and a voltage to develop at the generator output terminals. The Turkwell generator outputs 106MW at 11KV which is then stepped up to 32KV and fed to power lines from Jinja (Uganda) and taken to Lessos sub station. iii. Transformers- Modern electric power systems use transformers to convert electricity into different voltages. With transformers, each stage of the system can be operated at an appropriate voltage. In a typical system, the generators at the power station deliver a voltage of from 1,000 to 26,000 volts. Transformers step this voltage up to values ranging from 138,000 to 765,000 V for the long-distance primary transmission line because higher voltages can be transmitted more efficiently over long distances. At the substation the voltage may be transformed down to levels of 69,000 to 138,000 V for further transfer on the distribution system. Another set of transformers step the voltage down again to a distribution level such as 2,400 or 4,160 V or 15, 27, or 33 kilovolts (kV). Finally the voltage is transformed once again at the distribution transformer near the point of use to 240 or 120V. iv. Transmission Lines- The lines of high-voltage transmission systems are usually composed of wires of copper, aluminum, or copper-clad or aluminum-clad steel, which are suspended from tall latticework towers of steel by strings of porcelain insulators. By the use of clad steel wires and high towers, the distance between towers can be increased, and the cost of the transmission line thus reduced. In modern installations with essentially straight paths, high-voltage lines may be built with as few as six towers to the kilometer. In some areas high-voltage lines are suspended from tall wooden poles spaced more closely together. v. Switchyard- At the switchyard, 11KV voltage output for each generator is connected in a system of buses to the main generator transformer for step-up to 132KV for transmission. In the switchyard there is a series of lightning arresters. There is also a communication cable next to the neutral running which is a fibre optic for monitoring the transmission line. For the conductors, aluminum is used but steel is used for tension purposes. For lower voltage distribution lines, wooden poles are generally used rather than steel towers. In cities and other areas where open lines create a safety hazard or are considered unattractive, insulated underground cables are used for distribution. Some of these cables have a hollow core through which oil circulates under low pressure. The oil provides temporary protection from water damage to the enclosed wires should the cable develop a leak. Pipe-type cables in which three cables are enclosed in a pipe filled with oil under high pressure (14 kg per sq cm/200 psi) are frequently used. These cables are used for transmission of current at voltages as high as 345,000 V (or 345 kV). SAFETY MEASURES i. There is a developed plan to shut down quickly if any beyond-measures emergency occurs in the operation time of the facility. ii. There is yearly maintenance of the plant when all the machines are closed down for maintenance and check up. Old and worn out machine parts are replaced during such a period. iii. There are numerous emergency doors to enable quick escape in case of emergency. iv. The management carries out awareness training to all new employees and trainees to inform them on safety measures. v. All employees put on safety wear e.g. helmets, overalls and safety boots. vi. There are fixed alarm gadgets that alert employees if an emergency occurs in the operation time of the facility. PROBLEMS FACED The plant has faced several problems ever since its inception. The problems brought foward before construction were as follows: i. Environmental impact- The hydrological and ecological formation of the river was greatly disturbed when the river was eventually diverted. Wildlife, especially the colobus monkey and hippopotamus, dependent on the river water were forced to seek water sources at the lower populous Nyakwere plains disturbing their habitat. ii. Socio-economic effects- The project displaced more than 1,000 households through resettlement. Loss of arable land coupled with inadequate compensation is adversely affecting the livelihood of these predominantly subsistent communities. iii. Cultural Effects- The diversion of the river occurs upstream of the breathtaking Odino falls. The community attaches a lot of cultural values and beliefs to the falls. According to the community, the falls is the harbinger of good and bad omen. It is the home of prosperity or death. The aftermath of the construction has had issues also. Both within and around the plant: iv. The rainfall pattern in western Kenya can be described as steady but erratic and this unpredictable nature has made it difficult to plan operations at the power plants. The river’s water levels is natural and a fall would mean a depriciated generation capacity. v. Because of the nature of hydroelectric systems, the water run-off often takes on a higher temperature, loses oxygen content, experiences siltation, and gains in phosphorus and nitrogen content. SOLUTIONS & FINANCIAL IMPLICATIONS i. Electricity and piped water in the homes ii. Jobs at the plant have been awarded to the locals. KenGen through its CSR has done a lot to the Community Such as giving Scholarship to bright needy students in all KenGen Stations Community Schools. iii. It also help in donations such as to the children orphanages, helping kids with heart diseases, helping in famine relief by giving food and other domestic items. iv. New schools and dispensaries in their remote villages. KenGen has done a lot regarding the building of schools such as Aomo Primary School, Apondo Kasaye Primary School and Thurdibuoro Secondary School. It has also help in building of Thurdibuoro AIC Church and furnished it with pews. v. KenGen has so far dug more than five boreholes in remote villages in Nyakach and Kasipul Kabondo. Last year, the company handed over water projects worth Sh143 million to villagers living around River Sondu Miriu. vi. Fortunately the water quality problem has been dealt with by the production of "fish ladders". These structures provide a pathway for fish to navigate past the hydroelectric dam construction.   RECOMMENDATIONS & OBSERVATIONS Hydropower is the cheapest way to generate electricity today. No other energy source, renewable or nonrenewable, can match it. Producing electricity from hydropower is cheap because, once a dam has been built and the equipment installed, the energy source-flowing water-is free. Although Hydropower does present a few environmental problems the inherent technical, economic and environmental benefits of hydroelectric power make it an important contributor to the future world energy mix. Weighing up the benefits and environmental disadvantages is difficult. Until recently, projects deemed to be for ‘the greater good’ of the country werecarried out regardless of the local human and environmental cost. This haschanged recently, but it is still very difficult to balance. For example, Egypt’s communities have benefited from receiving electricity, yet the effect of buildingthe Aswan dam has been to starve the farming communities of nutrient-rich silt that used to be brought down on the floods each year. The benefits of electricity are undisputable for both economic and social development, and if the balance is between providing electricity that reduces the human mortality rate and protecting the environment, the former must be chosen. To choose the latter is arrogance on our part, sitting in well-lit comfy buildings, legislating for an effect that will never harm us. The theoretical amount of hydroelectric power available world-wide is about four times more than has been exploited at the present time. It is clear that the actual amount of hydroelectricity generated will be much less than this total, due to the growing anxiety about environmental costs and the economic cost of developing many of these sites. Although it is feasible for large scale hydroelectric power projects to be developed I do not believe this to be desirable because of the huge environmental impact. However an increase in SHP schemes should be encouraged to meet local needs. REFERENCES a) Referential notes taken during the industrial visit to Sondu Miriu Hydro-Electric Power Project premises on the 22nd of June 2011. b) The official KenGen website- http:// www.kengen.co.ke c) The Wikipedia website- http://en.wikipedia.com