Misplaced Pages

#596403

52-735: Rangit Dam (Hindi: रन्गीत् बाँध Bāndh), which forms the headworks of the Rangit Hydroelectric Power Project Stage III , is a run-of-the-river hydroelectric power project on the Ranjit River , a major tributary of the Teesta River in the South Sikkim district of the Northeastern Indian state of Sikkim . The project's construction was completed in 1999. The project is fully functional since 2000. The project

104-433: A global testing ground for 10–50 MW run-of-river technology . As of March 2010, there were 628 applications pending for new water licences solely for power generation, representing more than 750 potential points of river diversion. In undeveloped areas, new access roads and transmission lines can cause habitat fragmentation , allowing the introduction of invasive species. Run-of-the-river projects strongly depend on

156-417: A lake or reservoir upstream. A small dam is usually built to create a headpond ensuring that there is enough water entering the penstock pipes that lead to the turbines , which are at a lower elevation. Projects with pondage, as opposed to those without pondage, can store water for daily load demands. In general, projects divert some or most of a river's flow (up to 95% of mean annual discharge) through

208-410: A pipe and/or tunnel leading to electricity-generating turbines, then return the water back to the river downstream. Run-of-the-river projects are dramatically different in design and appearance from conventional hydroelectric projects. Traditional hydroelectric dams store enormous quantities of water in reservoirs , sometimes flooding large tracts of land. In contrast, run-of-river projects do not have

260-402: A recreational water park named 'Rangit Water World'. It is a popular venue for picnics, fishing, boating and rafting. The recreational centre was developed due to the initiative of the local people of Legship town. Run-of-the-river hydroelectricity Run-of-the-river, or ROR, hydroelectricity is considered ideal for streams or rivers that can sustain a minimum flow or those regulated by

312-492: A total length of all three lines is 59 metres (194 ft)) to connect to the three Francis Turbine Generating Units of 20 MW capacity each, through the MIVs. The tailwaters from the turbines are led back into the river through a combined short tailrace channel. The firm power generation is of the order of 39 MW corresponding to annual energy generation of 340 GWh (in a 90% dependable year). The ruling levels for power generation are: in

364-452: A travel of 61 kilometres (38 mi) from its source. At the dam site, the catchment area drained is 979.02 square kilometres (378.00 sq mi) (rain-fed catchment is 712 square kilometres (275 sq mi) and the balance area is snow fed above snow line contour of (4,570 metres (14,990 ft)); elevation of the catchment area varies from about 600 metres (2,000 ft) to about 7,338 metres (24,075 ft) (North Kabru Peak) and

416-428: A vertical shaft, to isolate water from the generator. This also facilitates installation and maintenance. Water wheels of different types have been used for more than 1,000 years to power mills of all types, but they were relatively inefficient. Nineteenth-century efficiency improvements of water turbines allowed them to replace nearly all water wheel applications and compete with steam engines wherever water power

468-436: A wide range of heads and flows. This versatility, along with their high efficiency, has made them the most widely used turbine in the world. Francis type units cover a head range from 40 to 600 m (130 to 2,000 ft), and their connected generator output power varies from just a few kilowatts up to 1000 MW. Large Francis turbines are individually designed for each site to operate with the given water flow and water head at

520-404: Is a type of reaction turbine, a category of turbine in which the working fluid comes to the turbine under immense pressure and the energy is extracted by the turbine blades from the working fluid. A part of the energy is given up by the fluid because of pressure changes occurring on the blades of the turbine, quantified by the expression of degree of reaction , while the remaining part of the energy

572-417: Is considered an "unfirm" source of power: a run-of-the-river project has little or no capacity for energy storage and so cannot co-ordinate the output of electricity generation to match consumer demand. It thus generates much more power when seasonal river flows are high (spring freshet ), and depending on location, much less during drier summer months or frozen winter months. Depending on location and type,

SECTION 10

#1732886604597

624-451: Is delimited between ( 27°16′30″N 88°00′51″E  /  27.275°N 88.0141°E  / 27.275; 88.0141 ) and ( 27°37′10″N 88°25′12″E  /  27.6195°N 88.42°E  / 27.6195; 88.42 ). A number of perennial streams originate in glacial fields of the river basin; important snow-fed rivers which constitute the Rangit basin above the dam site are

676-472: Is equal to that at the inlet to the draft tube. Using the Euler turbine equation, E / m = e = V w1 U 1 , where e is the energy transfer to the rotor per unit mass of the fluid. From the inlet velocity triangle, and Therefore The loss of kinetic energy per unit mass at the outlet is V f2 /2 . Therefore, neglecting friction, the blade efficiency becomes i.e. Degree of reaction can be defined as

728-445: Is extracted by the volute casing of the turbine. At the exit, water acts on the spinning cup-shaped runner features, leaving at low velocity and low swirl with very little kinetic or potential energy left. The turbine's exit tube is shaped to help decelerate the water flow and recover the pressure. Usually the flow velocity (velocity perpendicular to the tangential direction) remains constant throughout, i.e. V f1 = V f2 and

780-501: Is generally used to cover exclusively short-term peak times electricity demand. Diversion Weir is also heavily dependent on the natural river flow. Similar to a regular dam, water is stored from lull periods to be used during peak-times. This allows for the pondage dams to provide for the regulation of daily and/or weekly flows depending on location. When developed with care to footprint size and location, run-of-the-river hydro projects can create sustainable energy minimizing impacts to

832-455: Is necessary, as these are major parameters affecting power production. Draft tube : The draft tube is a conduit that connects the runner exit to the tail race where the water is discharged from the turbine. Its primary function is to reduce the velocity of discharged water to minimize the loss of kinetic energy at the outlet. This permits the turbine to be set above the tail water without appreciable drop of available head. The Francis turbine

884-441: Is rated at 1,853 MW. Some run-of-the-river projects are downstream of other dams and reservoirs. The reservoir was not built by the project but takes advantage of the water supplied by it. An example would be the 1995 1,436 MW La Grande-1 generating station . Previous upstream dams and reservoirs were part of the 1980s James Bay Project . There are also small and somewhat-mobile forms of a run-of-the-river power plants. One example

936-423: Is seen when the head height is between 100–300 metres (330–980 ft). Penstock diameters are between 1 and 10 m (3.3 and 32.8 ft). The speeds of different turbine units range from 70 to 1000  rpm . A wicket gate around the outside of the turbine's rotating runner controls the rate of water flow through the turbine for different power production rates. Francis turbines are usually mounted with

988-653: Is the so-called electricity buoy , a small floating hydroelectric power plant . Like most buoys, it is anchored to the ground, in this case in a river. The energy within the moving water propels a power generator and thereby creates electricity. Prototypes by commercial producers are generating power on the Middle Rhine river in Germany and on the Danube river in Austria. The advantages and disadvantages of run-of-river dams depends on

1040-688: The Government of India and built by its parastatal organization namely, the National Hydroelectric Power Corporation (NHPC). The construction of the project was completed in December 1999 and operation started in January 2000. Operation and maintenance of the project is also with the NHPC. This power project was the third stage of the five-stage cascade development conceived on the main stem of

1092-915: The disadvantages associated with reservoirs and so cause fewer environmental impacts. The use of the term "run-of-the-river" for power projects varies around the world. Some may consider a project run-of-the-river if power is produced with no water storage, but limited storage is considered run-of-the-river by others. Developers may mislabel a project run-of-the-river to soothe public perception about its environmental or social effects. The European Network of Transmission System Operators for Electricity distinguishes run-of-the-river and pondage hydropower plants, which can hold enough water to allow generation for up to 24 hours (reservoir capacity / generating capacity ≤ 24 hours), from reservoir hydropower plants, which hold far more than 24 hours of generation without pumps. The Bureau of Indian Standards describes run-of-the-river hydroelectricity as: A power station utilizing

SECTION 20

#1732886604597

1144-509: The Daling series of quartzites and phyllites dominate the area. This rock type is overlain by crystalline Darjeeling Gneiss comprising gneisses and granitoides. Recent alluvium of sandy loam , silty loam and clayey material of varying thickness overlay the rock formations. The banks of the Rangit River depict silty clay material with large rock blocks. Many land slides are observed in

1196-547: The Forest Department of the Government of Sikkim involving engineering treatment measures (included agricultural land, forest land and water land) and biological treatment measures. 15 nurseries were established covering an area of 18.5 hectares (46 acres)) to provide saplings/seedlings for plantation in the sub-watersheds of the catchment identified for treatment. The reservoir created by the Rangit dam has been developed into

1248-916: The Hydropower project. This activity involves several works defined under the 'Catchment Area Treatment' (CAT) plan. For evolving the CAT plan, the status of the reservoir catchment was analysed. The reservoir catchment consists of five types of forests namely, the East Himalayan Sub-Tropical wet hill forests (elevation range of 800–1,800 metres (2,600–5,900 ft)), East Himalayan wet temperate forests (elevation range of 1,800–2,700 metres (5,900–8,900 ft)), Oak and Rhododendron forests (elevated above 2,700 metres (8,900 ft)), mixed coniferous forests (in elevation range of 2,700–3,750 metres (8,860–12,300 ft)) and alpine scrubs/pastures (above 3,750 metres (12,300 ft)). There are 35 reserve forests in

1300-536: The Rangit River, and was the first to be built in the series of Rangit Stage I to IV initially conceived by the Central Water Commission . Three other projects on the Rangit River planned and under development are the Rangit Stage II (60 MW capacity), Rangit Stage IV (3×40 MW = 120 MW capacity) and Jorethong HEP (96 MW); the last two projects are now under construction. In river valley reservoir projects,

1352-537: The Rathong Chu, Rimbi Chu, Prek Chu, Ralli Chu, Rongdon Chu and Kayam Chu. The drainage pattern is sub-dendentric. The dam is located at a distance of 130 kilometres (81 mi) from Siliguri and70 kilometres (43 mi) from Gangtok. The dam is located downstream of the confluence of Rathong Chu and Rangit Rivers near the Legship town and the powerhouse of the project is located near Sagbari village. The annual inflow in

1404-479: The catchment, out of which 29 are in West Sikkim district and six (6) are in South Sikkim district . The entire catchment area was analysed in detail to assess the degraded areas to be treated under the CAT plan to reduce siltation problems. An area of 13,075 hectares (32,310 acres)) was identified for implementing engineering and biological treatment measures. These measures were implemented, starting with 1995–96, by

1456-422: The catchment, which add to the siltation problems of the reservoir. The Rangit dam is 45 metres (148 ft) high concrete gravity structure of 100 metres (330 ft) length. The reservoir created behind the dam has a storage capacity of 1,175,000 cubic metres. The storage created is utilized for hydropower generation at a surface Powerhouse located on the left bank of the Rangit River. The diversion of flow from

1508-508: The consistent flow of water, as they lack reservoirs and depend on the natural flow of rivers. Consequently, these projects are more vulnerable to climate change compared to storage-based projects. Short-term climate anomalies such as the El Niño Southern Oscillation (ENSO) [1] can significantly disrupt the flow and can have a profound impact on the operation of these projects. Thus, incorporating climate change considerations into

1560-406: The design of high-efficiency turbines to precisely match a site's water flow and pressure ( water head ). A Francis turbine consists of the following main parts: Spiral casing : The spiral casing around the runner of the turbine is known as the volute casing or scroll case. Throughout its length, it has numerous openings at regular intervals to allow the working fluid to impinge on the blades of

1612-412: The electricity needed by consumers and industry. Moreover, run-of-the-river hydroelectric plants do not have reservoirs, thus eliminating the methane and carbon dioxide emissions caused by the decomposition of organic matter in the reservoir of a conventional hydroelectric dam. That is a particular advantage in tropical countries, where methane generation can be a problem. Without a reservoir, flooding of

Rangit Dam - Misplaced Pages Continue

1664-470: The gravity of the siltation problem induced due to catchment degradation is serious and needs to be suitably addressed. For this purpose, the Ministry of Environment and Forests , Government of India have made it obligatory for the project authorities to implement physical engineering and biological measures in the catchment area of the project to be taken up pari passu (concurrently) with the implementation of

1716-436: The guide and stay vanes is to convert the pressure energy of the fluid into kinetic energy. It also serves to direct the flow at design angles to the runner blades. Runner blades : Runner blades are the heart of any turbine. These are the centers where the fluid strikes and the tangential force of the impact produces torque causing the shaft of the turbine to rotate. Close attention to design of blade angles at inlet and outlet

1768-506: The highest possible efficiency, typically over 90% (to 99% ). In contrast to the Pelton turbine , the Francis turbine operates at its best completely filled with water at all times. The turbine and the outlet channel may be placed lower than the lake or sea level outside, reducing the tendency for cavitation . In addition to electrical production , they may also be used for pumped storage , where

1820-458: The initial design and location selection of run-of-the-river projects can help mitigate the vulnerability of these projects to climate-related disruptions. Francis Turbine The Francis turbine is a type of water turbine . It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today, and can achieve over 95% efficiency. The process of arriving at

1872-467: The modern Francis runner design took from 1848 to approximately 1920. It became known as the Francis turbine around 1920, being named after British-American engineer James B. Francis who in 1848 created a new turbine design. Francis turbines are primarily used for producing electricity. The power output of the electric generators generally ranges from just a few kilowatts up to 1000 MW, though mini-hydro installations may be lower. The best performance

1924-433: The plant will most likely have a lower head of water than from a dam, and will thus generate less power. The potential power at a site is a result of the head and flow of water. By damming a river, the head is available to generate power at the face of the dam. A dam may create a reservoir hundreds of kilometres long, but in run-of-the-river the head is usually delivered by a canal, pipe or tunnel constructed upstream of

1976-442: The power house. The cost of upstream construction makes a steep drop desirable, such as falls or rapids. Small, well-sited run-of-the-river projects can be developed with minimal environmental impacts. Larger projects have more environmental concerns. For fish-bearing rivers, a ladder may be required, and dissolved gases downstream may affect fish. In British Columbia , the mountainous terrain and wealth of big rivers have made it

2028-433: The ratio of pressure energy change in the blades to total energy change of the fluid. This means that it is a ratio indicating the fraction of total change in fluid pressure energy occurring in the blades of the turbine. The rest of the changes occur in the stator blades of the turbines and the volute casing as it has a varying cross-sectional area. For example, if the degree of reaction is given as 50%, that means that half of

2080-598: The reservoir to the surface Powerhouse is effected through an Intake leading to a concrete lined Head Race Tunnel (HRT) of 4.5 metres (15 ft) diameter (Horse shoe shaped and concrete lined) of 3 kilometres (1.9 mi) length, a Surge Shaft (14 metres (46 ft) diameter and of 60 metres (200 ft) depth at the end of the HRT with control arrangement followed by one main penstock pipe (of 3.5 metres (11 ft) diameter and length of 270 metres (890 ft)) trifurcating into three lines of 2 metres (6.6 ft) diameter each (with

2132-586: The reservoir, Full Reservoir Level (FRL) of 639 metres (2,096 ft) and Minimum Draw Down Level (MDDL) of 627 metres (2,057 ft)), the Normal Tail Water Level (NTWL) in the Tail Race Channel from the Powerhouse of 512 m and under an operating gross head of 127 m. Since it is owned by coastal projects ltd, the power generated is shared and Sikkim gets a share of 13.33%. The project was funded by

Rangit Dam - Misplaced Pages Continue

2184-469: The river at the location of the dam has been estimated as 696,000 cubic metres. The maximum flood discharge has been adopted as 3,395 cubic metres (119,900 cu ft)/s while the design flood discharge adopted for the spillway of the dam is 2,725 cubic metres (96,200 cu ft)/sec. The dependable discharge adopted for diversion from the reservoir for power generation is 1717.8 cubic metres (630 cu ft)/s (without considering contribution from

2236-581: The run of the river flows for generation of power with sufficient pondage for supplying water for meeting diurnal or weekly fluctuations of demand. In such stations, the normal course of the river is not materially altered. Many of the larger run-of-the-river projects have been designed to a scale and generating capacity rivaling some traditional hydroelectric dams. For example, the Beauharnois Hydroelectric Generating Station in Quebec

2288-400: The runner. These openings convert the pressure energy of the fluid into kinetic energy just before the fluid impinges on the blades. This maintains a constant velocity despite the fact that numerous openings have been provided for the fluid to enter the blades, as the cross-sectional area of this casing decreases uniformly along the circumference. Guide and stay vanes : The primary function of

2340-602: The same principles. S. B. Howd obtained a US patent in 1838 for a similar design. In 1848 James B. Francis , while working as head engineer of the Locks and Canals company in the water wheel-powered textile factory city of Lowell, Massachusetts , improved on these designs to create more efficient turbines. He applied scientific principles and testing methods to produce a very efficient turbine design. More importantly, his mathematical and graphical calculation methods improved turbine design and engineering. His analytical methods allowed

2392-417: The surrounding environment and nearby communities. Run-of-the-river harnesses the natural potential energy of water by eliminating the need to burn coal or natural gas to generate the electricity needed by consumers and industry. Advantages include: Like all hydro-electric power, run-of-the-river harnesses the natural potential energy of water by eliminating the need to burn coal or natural gas to generate

2444-876: The total energy change of the fluid is taking place in the rotor blades and the other half is occurring in the stator blades. If the degree of reaction is zero it means that the energy changes due to the rotor blades is zero, leading to a different turbine design called the Pelton Turbine . The second equality above holds, since discharge is radial in a Francis turbine. Now, putting in the value of 'e' from above and using V 1 2 − V f 2 2 = V f 1 2 cot ⁡ α 2 {\displaystyle V_{1}^{2}-V_{f2}^{2}=V_{f1}^{2}\cot \alpha _{2}} (as V f 2 = V f 1 {\displaystyle V_{f2}=V_{f1}} ) Francis turbines may be designed for

2496-406: The type, the following sections generally refer to Dam-Toe unless otherwise stated. These are listed in order of least impact to most impact, as well as (on average) requisite project size. Dam-toe has no flow regulation and utilizes the natural flow of the river to turn the turbines. Electricity generation is heavily dependent on river flow. Diversion Weir has very little flow regulation, which

2548-450: The upper part of the river does not take place. As a result, people remain living at or near the river and existing habitats are not flooded. Any pre-existing pattern of flooding will continue unaltered, which presents a flood risk to the facility and downstream areas. Due to their low impact, run-of-the-river dams can be implemented in existing irrigation dams with little to no change in the local fluvial ecosystem. Run-of-the-river power

2600-539: The upstream Stage II project, which is yet to be implemented). The climate of the Rangit River basin is cold and humid. The climatic seasons of the basin represented in the project area are: spring season-late February, summer season-March, premonsoon showers-April and May; monsoon season May to September, sometimes extending to October. The snow season, at higher elevations of the catchment falls between December and February. Winters are very cold with mist and fog lasting from November to February. Precambrian formations of

2652-516: Was available. After electric generators were developed in the late 1800s, turbines were a natural source of generator power where potential hydropower sources existed. In 1826 the French engineer Benoit Fourneyron developed a high-efficiency (80%) outward-flow water turbine. Water was directed tangentially through the turbine runner, causing it to spin. Another French engineer, Jean-Victor Poncelet , designed an inward-flow turbine in about 1820 that used

SECTION 50

#1732886604597

2704-673: Was built at a cost of Rs 4922.6 million (Rs 492.26 crores) (at US$ 1 = Rs 45, this is US$ 109.39 million). The average annual power generation from the 60 MW (3x20 MW) project is 340 GWh with firm power of 39 MW. The Ranjit River on which the Rangit Dam is located, is a major right bank tributary of the Teesta River in Sikkim. The river arises from the Talung glacier and it meets the Teesta river at Melli after

#596403