Erathna Mini Hydro Power Project

Erathna Mini Hydro Power Project
Country Sri Lanka
Location Ratnapura, Sabaragamuwa Province
Coordinates 06°49′36″N 80°26′29″E / 6.82667°N 80.44139°E / 6.82667; 80.44139Coordinates: 06°49′36″N 80°26′29″E / 6.82667°N 80.44139°E / 6.82667; 80.44139
Purpose Power
Status Operational
Construction began September 2001 (2001-09)
Opening date July 2004 (2004-07)
Owner(s) Vallibel Power Erathna PLC
Power Station
Type run of the river
Installed capacity 10 MW
Annual generation 40 GWh

The Erathna Mini Hydro Power Project[1][2][3] is one of the run of river mini hydro power projects in Sri Lanka which has the install capacity of 10 MW. The project is located on the Kuru Ganga, a tributary of the Kalu Ganga (Black River).[4]

Introduction

Sketch of the Power Plant

The developer of the project is Vallibel Power Erathna PLC[1] and the project is developed on built, own and operate basis. The intention of the company is to generate 40GWh[1] of green energy annually and to export to the national electricity grid of Ceylon Electricity Board which is the only authorized Institute for electricity transmission in Sri Lanka, controlling the all major functions of electricity generation, transmission, distribution and retailing in the country.

The project consists of weir, intake, headrace channel, sedimentation tank, forebay, penstock, powerhouse and transmission system.[5][6]

Location

Location of the Power Plant

The catchment of this project is 14.5km2 and the design flow is 2.7m3/s. The catchment falls within the peak wilds and it is considered as natural reserve. Topography surveys of the project area are available in the sheet 68 – Nuwara Eliya which in the scale of 1:50,000 by Survey Department of Sri Lanka. Sheet 61/16, 1:10,000 is also used for the initial conceptual development of the project. The Geo Coordinates of the project activity is 6o 49’36” N, 80o 26’ 29” E.[5][6]

Kuru Ganga leaves the peak wilderness sanctuary at an elevation of 1030m MSL and flows steeply westwards till it reaches the village of Adavikanda at an elevation of 400m MSL. Close to the pilgrim's rest called “Maha Ambalama” it forms the “Manna-Kethi” falls from elevation 860m to 840m. Thereafter flows on steeply exposed bedrock to an elevation of 600m. The riverbed below this level is covered with large boulders and the banks with thick vegetation.[5][6]

Project implementation

Traditional Groundbreaking Ceremony (Chairman of Vallibel Group; Mr Dhammika Perera,)
Traditional Groundbreaking Ceremony (Jt.Chief Executive Officer; Mr. Aruna Dheerasinghe)

The project is owned and operated by Vallibel Power Erathna PLC, which is the largest public quoted mini hydro power company in Sri Lanka. 5MW hydro power potential was identified at the aforesaid location at Erathna and feasibility studying process was initiated under the name of Zyrex Power Company Erathna Limited. Then the ownership of the company was changed to Vallibel Group of Companies. Then the project capacity was enhanced up to 10MW with the identification of the higher hydro power potential by the Vallibel Group. Later the name change of the company was done as Vallibel Power Erathna PLC.[1]

The project developer, Vallibel Power Erathna PLC itself carried out the construction work. Some of the contracts were awarded to third parties on the basis of labour contracts. Project Management was done by Vallibel group.

Construction of the power plant commenced in September 2001 with the traditional groundbreaking ceremony.

Access road

Inspection Visits at Initial Stage (Mr. Nihal Karunarathna, Mr. Suraweera, Mr. Aththnayaka, Mr. Aruna Dheerasinghe, are in the photo)

In order to facilitate the project and the other operational and maintenance purposes, a 3.5 km long new access road was built from powerhouse location to the forebay location. The access road starts from Adavikanda where the power house is built-up. The end point is Warangala; the Forebay location. By the construction of the access road, the requirement of accessing to the weir, penstock path, forebay and channel was fulfilled. Since the path is along the part of a highland complex of the country and 3.5  km long path climbs an elevation of 460m, it consists of steep valleys, rock cliffs, boulders and boulder trains. And also slope directions and slope angles vary considerably from place to place due to the inherent nature of the area. Therefore, it was a hard task to complete the access road and the construction of the access road too a period of 8 months.

With the access road implementation, nearby existing roads were rehabilitated by the company for upgrading the community wellbeing. Although the construction work is done, the company managed to make a less environmental impact. Because instead of removed vegetation within construction site, a lot of trees were planted by carrying out continuous tree planting programs.

Weir

Inspection of Weir Construction (Mr. Dhammika Perera, Mr. Saram, Mr. Dheerasinghe, and Mr. Jayawardhana are in the photo)

To optimize the plant design, the actual flow measurements should have been taken immediately. Therefore the weir construction was started parallel to the construction of the access road and constructed weir was used to measure the river flow.

Since a motorable access was not available at that time, laborers climbed with all materials such as sand, metal, cement, steel etc for a 460m elevation from power house location to the wier location.

The weir is located downstream of the Manna-Kethi fall. From the pool at the base of the fall another tributary joins from the left bank. As the project is run-of-river type, no storage is required at the weir. The weir is 20m long with the maximum height of 2m. Due to high flood flows, the weir is designed as a concrete gravity structure. Dowels are provided for added safety against sliding.[5][6]

Intake

The intake is a closed reinforced concrete conduit which is with the length of 10m and the section of 2m x 1m. There are trash bars spaced at 150mm to prevent the entry of debris to the channel path. The intake is designed for a maximum flow of 3m3/s.

Headrace channel

Construction of Channel (Mr. Dhammika Perera, Mr. Keerthi, Mr. Dheerasinghe, are in the photo)

The initial 20 m of the channel from the intake is closed conduit built into the right abutment to prevent the entry of floods and to attenuate the flow through the conduit during high flood levels. A side spillway of 10m long is provided in the open channel built on the rock immediately downstream of the closed conduit to spill the excess water entering at high flood levels. The headrace channel is of reinforced concrete, rectangular in section, 2m wide and 1.2m high in the inside based on economic studies. The length of the channel is 280m and the bed slope 2.5 in 1000. The channel is located in earth-cut, with crossings over minor streams. The channel is covered for most of its length to prevent the ingress of trash and silt from the hill slope.[5][6]

Sedimentation tank

The sedimentation tank is of a conventional design and it settles silt and sand to a particle size of 0.2mm. A desilting gate discharges the accumulated silt to a watercourse.[5][6]

Sedimentation Tank at Operational Stage

Forebay

The forebay is located on a hill slope of bedrock and it is a reinforced concrete structure. The forebay incorporates a spillway and a trash rack. Forebay spillway is specially designed considering less environmental impacts by directing the water spill to natural water path and it discharges 3m3/s. The forebay is designed to have a steady flow to penstock avoiding turbulence and vortex. The elevation of water is maintained automatically with the level sensors with the machine operation.[5][6]

Penstock

Penstock Installation at Construction Stage

In early 2002, penstock civil works such as anchors and supports are started and penstock installation was initiated in 2003. The penstock is 2400m long with a drop of 462m. Upper 1235m is a single pipe and the rest is twin pipes. The penstock has 33 anchors and supports at 12 meters interval. The single type penstock reduces its outer diameter from 1118mm to 1016mm and thereafter to 914mm. At the just upstream 12th anchor the pipe bifurcates into 813mm pipes. The twin pipes further reduce to 711mm and then to 620mm. Before entry to the powerhouse, it reduces to 500mm to suit the inlet valve diameter.[5][6]

The penstock has sleeve type expansion joints downstream of the every anchor and the penstock is supported by the piers by saddle supports with a suitable sliding interface. The sleeve type joint was thought to be the most reliable, durable and maintenance free joint for such a high head pipeline. Anchor blocks are reinforced concrete structures with rubble masonry sections to provide additional mass required against sliding.

Powerhouse

Power House at Operational Stage

The powerhouse is located on the right bank of Kuru Ganga at the Adavikanda where the road from Erathna to Adavikanda ends. The power house is a reinforced concrete structure which 18m wide and 30m long. The main machine floor served by the overhead crane is only 10.5 meters wide.

The power house has the machine bay, erection Bay, the inlet valve Bay, a control panel bay and a medium voltage room. There is office room and record room adjacent to the control panel bay and the power house is specially designed with a public gallery for visitors. The powerhouse superstructure is with a reinforced concrete frame with crane beams. The walls are constructed of cement bricks and plastering. Doors and windows are in aluminium and wood. Roof is made of concrete.[5][6]

The tailrace channel conveys the tail water back to the river and a part of the tailrace.

The switchyard is located close to the powerhouse and has two generator transformers and the service transformers connecting with the switchgear. The terminal tower of the 33kV transmission line is located at the end of the switchyard.

Electro-mechanical equipment

The power house has two twin jet Pelton turbines coupled to two generators of 4.95MW each which are manufactured by Voith Siemens.

The Pelton turbines are horizontal units operating at 750rpm. The runner buckets are made with integrally cast stainless cast steel. The runner is directly coupled to the generator shaft. Other equipment associated with the turbine are inlet valve, distributor, power nozzles and needles and the governor and hydraulic systems. Rated voltage of the generators is 6.3kV. The bearings of generators are oil lubricated sleeve type and separate oil lubrication unit is used. Two 6MVA transformers are used to step up the generator voltage to 33KV. These transformers are the outdoor type. A 50kVA transformer operating at 400V is used for station supply.[5][6]

Transmission line

The method of transmission is an 18 km line connected to the Kosgama – Ratnapura 33kV power line. Pre-stressed concrete poles, SL type steel towers and elm conductors are used for the construction of the transmission line. The route of new line is same as the route taken by existing Sri Pada line and Erathna 33kV supply line.[5][6]

Design

Designs were carried out by specialised consultants and those were divided among company itself and outsourced consultants. Powerhouse structural design was done by Stems Consultants (Pte) Ltd. Hydraulic and Hydropower specialised designs are done by a team of specialists namely, G.G. Jayawardhana, P.S.P.S. De Saram and A. K. Dheerasinghe. Other structural designs were outsourced and done by individual structural designers. The architectural design of the powerhouse was done by Pan Arch (Pvt) Ltd.

Project Management Team of Vallibel (Mr. Suraweera, Mr. Aruna Dheerasinghe are in the photo)

The plant is commissioned on July 2004 and since then it serves Sri Lankan national grid by providing 40GWh of green energy in every year.

Contribution to sustainable development

Environmental benefits

The project contributes to an improvement of the local environment through reducing emissions such as CO2, SOx and NOx from thermal power plants. By this project, an equal amount of power generated using thermal sources which result in increasing the emission of Green House Gases is displaced. Due to the existence of this project approximately 50,000mt of CO2 emissions reduced annually.

Economic benefits

The project created employment opportunities during the project commissioning and operational period. The commissioning of this project consists of earth work, concrete work as well as mechanical and electrical work. This required both skilled and unskilled employees. As a result of the project, the income of the rural families in the project area increased. This is in line with the sustainable development criteria of the country such as eradication of the poverty and improving the social development.

Social welfare

This project works closely with the community to upgrade their standard of living and make a genuine contribution to their lives. During the construction of the plant, the welfare of the community, minimal disturbance to lifestyles, develop housing and maintenance of the roads are prioritised. The welfare activities are as follows,

  • Improvement of the access to the village of Halgastenna through the construction of a road to replace the steep and dangerous footpath previously used by villagers
  • Repair of the Erathna – Adavikanda road which runs through the main access road to Sri Pada from Kuruwita
  • Provide financial assistance to local authorities for cleaning the Sri Pada Road before the start of the pilgrimage season.
  • For the benefit of worshippers, a place of worship at Sri Pada, and a Buddha statue with a platform for worshipping were constructed.
  • Five hundred steps were built at Warangal for the development of the devotees' footpath, and foot bridges, hand rails and guard rails constructed along the path.
  • The Kuruwita – Erathna road was repaired for 5 km from Kuruwita to Sudagala, and a side wall constructed at a culvert near Marukanda.
  • A building for a local school, Erathna Maha Vidyalaya was constructed
  • The men's ward of the Erathna rural hospital along with the Kuruwita Police Station were rehabilitated
  • 5 houses were constructed and donated for villagers.

Environmental impacts

This project results in a reduction in the water flow between the weir and the powerhouse and mandatory discharge is released throughout the project life to avoid any impact on river ecosystem. The water quality does not change due to the implementation of the project and there would be no change in the water availability downstream too. The potential environmental impacts identified were soil erosion, loss of soil stability and slope failure, reduction in the river flow between the weir and tailrace, some ecological impacts such as interference to fish mobility, destruction of plants and noise. But, the potential impacts of this project were negligible comparatively and all the precautions were taken to minimise the impacts as on the recommendations of relevant authorities and consultants.

Financial background

Total investment of the company was 720 MN LKR and equity to debt ratio is 30:70. Debt facilities were arranged by Commercial Bank, Sampath Bank & DFCC Bank of Sri Lanka.

Awards and certificates

Vallibel Power Erathna PLC operates as per International standards.

The Erathna Mini Hydro Power Project won the Bronze Award in Mini Hydro Category at the National Green Awards 2012.[1]

Green Award

See also

References

  1. 1 2 3 4 5 "Vallibel Web". Vallibel.
  2. ↑ "PUCSL" (PDF). PUCSL.
  3. ↑ "CEB web". CEB web. Archived from the original on 2015-07-15.
  4. ↑ "Erathna Mini Hydro Power Plant Project". Vallibel Power Erathna PLC. Retrieved 1 June 2017.
  5. 1 2 3 4 5 6 7 8 9 10 11 "PDD - CDM" (PDF). PDD - CDM.
  6. 1 2 3 4 5 6 7 8 9 10 11 study erathna.pdf?t=VjB8bnJ4aTRlfDDblTzyC2VDBV7ny_471c7q "Feasibility Report" Check |url= value (help) (PDF). Feasibility Report.
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