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Summary PLTA Aek Bilah
 
   Hydroelectric Power Plant (PLTA) Aek Bilah developed by PT. Berkah Daya Energi, located in Dolok and Dolok Sigompulon Districts, South Tapanuli Regency and North Padang Lawas Regency, North Sumatra Province with an installed capacity of 77 MW. Energy production was sold at 446,185.65 GWh per year. The land needed for development is 80.9 Ha. The time needed for construction is needed for 36 months and the construction time is 24 months, with a construction cost of $ 141,000,000. Assumptions for loan resources 70%, sources of own funds 30%, bank loan interest rates 13.5% obtained BCR value of 1.12, IRR of 15.58% while NPV value of $ 4,466,295,873 and this project will Break Event Point (BEP) in 6.4 years year.
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A. Technical Aspects

    Technical aspects include the study:

a. Hydrology: Conduct hydrological analysis through watershed data (DAS), Automatic Water Level Recorder (AWLR) and rainfall around the location to determine the planned discharge for the plant and flood discharge plans for planning civilian buildings in the river channel.

b. Topography: Conducting topographic survey and measurement activities to obtain conditions and situations as well as height differences from a location that will produce a situation map, long section and cross section.

c. Geology: Conduct geological studies to get an overview of the geological conditions of the study area by guiding geological maps, earthquake maps and conducting soil structure checks.

d. Making basic layouts and designs.

B. Machine and Equipment Aspects

   Based on the review of technical aspects, the machinery and equipment used will be examined, starting from the machinery and equipment in the Power House to the point of transaction agreed with PT PLN (Persero), including the pole and distribution network, so that the energy produced connected optimally.

C. Environmental Aspects

    Environmental aspects include:

a. Identifying field conditions both from the designation of the area / regional status as well as Economic, Social and Cultural.

b. Identifying impacts that will arise both during pre-construction, construction and post-construction (operational).

D. Financial Aspects

    Financial aspects include:

a. Make a calculation of estimated investment value needed from pre-construction activities, construction to the Commercial Operating Date (COD).

b. Make calculations of estimated operational costs and estimated cash flows.

c. Make financial analysis of several investment criteria including: Internal Rate of Return (IRR) project, IRR equity, payback period, Net Present Value (NPV), cost of goods manufactured, selling price of electrical energy, Benefit Cost Ratio (BCR) and ratio- other relevant financial ratios.

  Location

A. Geography

  South Tapanuli Regency is one of the districts in the province of North Sumatra, Indonesia. The capital is Sipirok. This regency was originally a very large district and has the capital in Padang Sidempuan. The regions that have separated from South Tapanuli Regency are Mandailing Natal, Padang Sidempuan City, North Padang Lawas and South Padang Lawas. The area of ​​South Tapanuli Regency is 379,326 Ha with its height ranging from 0 - 1,985 m above sea level. While North Padang Lawas Regency is one of the Regencies in North Sumatra Province, namely the result of the expansion of South Tapanuli Regency in accordance with the Law of the Republic of Indonesia Number 37 of 2007 and was ratified on August 10, 2007 concerning the establishment of North Padang Lawas Regency with the district capital is Gunung Old. The territory of North Padang Lawas Regency is a 'liaison' area between the east coast region that has developed and has become a national and regional trade door with the west coast region that is rich in natural resources and relatively undeveloped.

B. Administrative

  South Tapanuli Regency is located on line 0o 58 '35 "- 2o 07' 33" North Latitude and 98o 42 '50 "- 99o 34' 16" East Longitude. The total area of ​​South Tapanuli Regency is 4,444.82 km2 or 444,482.30 Ha. As for the administrative boundaries of South Tapanuli Regency, can be described as follows:

  • North: Kabupaten Tapanuli Tengah and Kabupaten Tapanuli Utara

  • East: Padang Lawas District and North Padang Lawas Regency and Labuhan Batu Regency.

  • South: Regency of Mandailing Natal.

  • West: Mandailing Natal Regency and the Indonesian Ocean.

  While North Padang Lawas Regency is in the northern part of North Sumatra Province. Geographically located at 1o 13 '50 "-2o 2' 32" North Latitude and 99o 20 '44 "- 100o 19' 10" East Longitude. The total area of ​​North Padang Lawas Regency is 3,918.05 km2, with the following administrative boundaries:

  • North Side: Borders with Kec. Bilah Hulu, Bilah Barat (Labuhan Batu Regency) Kec. Sungai Kanan, Kec. Torgamba (Labuhan Batu Selatan Regency), Kec. NA IX-X (Labuhan Batu Utara Regency).

  • East: Bordered by Rokan Hilir and Rokan Hulu Regencies, Riau Province;

  • South: Bordering Huristak District, Barumun Tengah District, Sosopan District, Padang Lawas Regency; and

  • West: Bordering Batang Batangola District, Angkola Timur District, Sipirok District, Arse District, Saipar Dolok Hole District, Aek Bilah District, South Tapanuli Regency.

  Plans for the construction of the Hydroelectric Power Plant located in the Aek Bilah River Flow. Based on the studies that have been carried out, civil building facilities are planned on the right side of the river. In government administration, the hydropower location is located in Dolok sub-district and Dolok Sigompulon sub-district, North Padang Lawas regency. As for the hydropower study location of the Aek Blade shown in the following figure:

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Study Location of hydropower on Map Indonesia
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Study Location of Hydroelectric Power Plant Aek Bilah on Map of North Sumatra
Hydropower Study Area Aek Bar on District Map

BASIC DESIGN OF AEK HYDROPOWER

The layout of a generator is a basic guideline in determining the main buildings according to the results of topography. The layout will show the required land area in accordance with the design of civil works, access roads and networks.

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Layout PLTA Aek Bilah
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The area needed for the construction of the Aek Bilah hydropower project is estimated to be 80.9 Ha.

A. Bendung (Weir)

    The type of weir that will be built on the Aek Bilah hydropower plant is a fixed type weir. Because the slope of the river at the location of the weir is not too large / sloping, which is about 3%, the height of the river is planned to be 25 m from the bottom of the floor upstreem. Some of the main components of the weir include:

    a. Dam Bendung

      The type of lighthouse for hydropower is Aek The selected blade is a round light with a Bucket type. The weir height has considered sedimentation on the river bed, because this sendimen can reduce the discharge to the intake.

    b. Weir Building Completeness

      At the location of the dam, the average slope of the river bed is known, S = 0.030. Flood discharge plans for a 100-year return period of 2,000 m3 / sec. At the location of the wide dam the river reaches ± 50 m. Based on the results of the calculation of the data above, the water level above the lighthouse is 3.06 m.

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Weir Design of Hydroelectric Power Plant Aek Bilah
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       c. Building Stability of Weir

          Based on the stability requirements that must be met in the planning of the weir (as described in CHAPTER 3). The results of the calculation of the stability of the weir can be seen in Annex E Stability Analysis of the Weir.

B. Conduction Channels / Tunnels (Tunnel)

    The design does not always refer to the best hydraulic cross section design, because there are also technical considerations (material, location and construction implementation) and economical. For Aek hydropower this bar is planned:

  Debit plan = 69.66 m3 / sec

  speed, V is 2.71 m / s.

  q design = 1.1 × 69.66 = 76.63 m3 / sec

  Tunnel Diameter = 6.00 m1

  A = 1 / 4π x D2 = 28.29 m2 (wet cross sectional area)

  V = q / A = 2.71 m / s.

  P = π x D = 18.86 m, (wet cross section length)

  For Strickler roughness values, k = 70 (for concrete)

obtained channel slope (S) as follows:

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Transverse Channel / Tunnel Crossing Profile (Tunnel)

C. Surge Tank

Planned The base level of the Surge Tank is 159 masl and the top surface elevation is 210 masl. It is planned that Surge Tank's diameter size is 15 m with a height of 51 m. The concept of Surge Tank images can be seen in the following figure.

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Design of Surge Tank Hydropower Aek Bilah

D. Pipa Pesat (Penstock)

   The layout of the Aek Bilah hydropower plant, the length of the fast pipe is 1700 m. The rapid pipe diameter is calculated according to the approximation formula of equation 3.3. For Qd = 69.66 m3 / s and He = 134 m obtained diameter = 4.20 m. With t = 2.8 cm, the outer diameter of the pipe is rapidly used by 4.26m. Whereas for the branch penstock diameter is obtained 3 x 2.6 m.

E. Power House

    The Power House building measures 51 mx 22 m for placement of 3 generating units @ 25.6 MW along with control equipment, supporting equipment, swithchgear and a multipurpose room and toilet. Power House is designed with a height of 11 meters, enough as an overhead crane with a capacity of 40 tons to facilitate the installation of generating equipment and maintenance work.

    The walls and columns of the Power House are built with reinforced concrete as well as being a 40-ton crane with a rail system installed on the WS steel pedestal. The discharge channel outside Power House is equipped with a stoplog. Concrete walls are required to use water proofing, so that there is no seepage from ground water around entering the building space. Besides that it is also equipped with holes and drainage pipes. Building and machine foundations consist of a raft foundation and are prepared with reinforced concrete. The power house floor is at an elevation of 60 m above sea level and free of flooding. Ventilation and windows are positioned in the east and west direction, which is in the direction of the exhaust channel.

F. Tail Race

    The dimensions of the drainage channel in the downstream are made the same as the carrier channel which is 7.5 x 3.7 m for wet height plus 0.5 m guard.

     Supporting buildings in hydropower are:

A. Operator House

   The operator's house consists of houses with stone foundation, brick wall, asbestos roof and building area of ​​54 m2.

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The operator's home picture

B. Guard Post

    The building of the guard post is made with a building area of 12 m2.

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Building Guard

C. Observation Post

     The observation post building is made with an area of 5 m2.

D. Access Road

    The length of the road Access to the Aek Bilah Hydroelectric Power Plant is 9 Km, which is 8 Km to repair the existing road and 1 Km to open a new road. The access road uses asphalt pavement (Hot Mix), with a minimum pavement width of 3.0 meters.

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typical access road

E. Connecting substations

    The connecting substation is planned according to the standards issued by PT. PLN (Persero) with a size of 4 x 4.5 m and a height of 3, 35 m.