(2) Utilization of Head between Aqueduct and River Beneath This idea would provide new diversion work near the existing aqueduct, and then utilize the head to the powerhouse to be constructed on the river bank beneath the aqueduct. The aqueduct is located in Sungaiduo Village, which is about 0.5 km upstream of the diversion structure BBH11 in the main canal. The plan, profile and current condition of the aqueduct are shown in Figures 5.3.5 and 5.3.6. Diversion Route from for Aqueduct for Power Generation Figure 5.3.5 Plan and Profile of Existing Aqueduct BBH11b’ BBH11b’ Aqueduct River beneath Aqueduct Figure 5.3.6 Existing Aqueduct 5-18 The gross head between the water surface in the main canal and the river bottom beneath the aqueduct is about 9.5 m, as shown in the as-built drawing and as confirmed at the site. As shown in Table 5.3.1, surplus water available for power generation is calculated for the basic scenarios in the same way as for the case of BBH6. The annual average discharge is 6.06 m3/s. Table 5.3.1 Surplus Water Available for Power Generation at BBH11b Site Basic Scenario Unit: m3/s Jan. Feb.Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec. 1st half 2.03 7.36 5.76 7.14 4.48 2.99 10.87 16.42 17.06 7.57 3.95 0.00 2nd half 4.05 0.75 0.85 1.60 0.53 5.22 13.11 15.99 0.00 8.64 2.45 6.72 Source: JICA Survey Team The most possible layout of this plan is to construct a new diversion structure on the main canal at the immediate downstream of the existing aqueduct. An intake is provided at the right bank of the main canal, which will be connected to the steel penstock and powerhouse to be newly constructed on the left bank of the river beneath the aqueduct. Comparison between this plan and the plan using the SEDASI pump station is presented in Table 5.3.2. As shown in this table, the plan using the SEDASI pump station is more suitable. As both these plans discharge surplus water outside the irrigation system, and thus mutually exclusive, the plan to utilize the head between the aqueduct and the river beneath is discarded from further examination. Table 5.3.2 Comparison of Plans Using Surplus Water in Main Canal Location SEDASI pump station Aqueduct Gross Head 19.0 m 9.5 m Annual Average of 7.43 m3/s 6.06 m3/s Surplus Water Available Project Component Rehabilitation of: New construction of: - Intake - Diversion structure - Sitiung Secondary Canal - Intake - Powerhouse - Penstock New construction of: - Powerhouse - Penstock Connection with 200 m 800 m Transmission Line Land Acquisition Not required Required Source: JICA Survey Team 5.3.2 Power Generation Plan Using Drop Works, Diversion Works and Siphons The Batang Hari main canal has drop works and diversion works, and surplus head is dissipated to the required head in the canal section there. Figure 5.3.7 shows a schematic diagram of the Batang Hari main irrigation system indicating locations of those drop works, diversion works and siphons. 5-19 Siguntur SC Sikabu SC SEDASI Pump Station ○○ Sitiung 5M Rawa Kapeh SC Sub Sc Mimpi MC Tarata Koto Tuo Terang SC Koto Tuo SC SC Sitiung SC BBH 1 BBH 3 ◎◎◎◎◎◎◎ BBH 2 BBH 4 BBH 5 BBH 6 BBH 7 Lima Kapeh SC Kelawa SC Tebing Tinggi Mimpi SC SC Pisang Rebus SC Kampung Baru SC Piruko MC Padang Candi SC Diversion & Drop Batang Hari Headworks BBRA 7M Sub Sc BBRA 11M Sub Sc Batu Rizal C Batu Rizal A SC Pulai SC Koto SC Beringin BBRA 10M Sub Sc 5M Sub Sc Padang Pulai A SC Bintungan ki Koto Beringing SC Batu Rizal B SC SC BBH 8 BBH 9 BBH 10-2 ◎ ◎ ◎◎◎BBH 11 Sungai Atang SC BBH 14 BBH 15-2 Koto Agung SC BBH 10-1 ◎◎◎◎◎ Koto BBH 12 Koto Padang BBH 13 Padang 3M BBH 15-1 Gunung Medan 6M2 Sub Sc A SC Sungai Duo SC Sub Sc Pinang Gadang SC Sialang Koto Padang SC Gaung Pinang Padang SC Gadang 2M Gunung Medan SC Pinang Gadang 3M Bintungan ka Sub Sc Aqueduct Sub Sc SC Pinang Gadang 4M Sialng Gaung 3M Sub Sc Sub Sc Tiumang 2M Sub Sc Sipangkur Siphon at BBS24 Sipangkur LEGEND ki Sub Sc 3M Sub Sc ◎ Diversion of MC Tarantang Sungai ○ Division S of SC. Tiumang SC Sipangkur Langkok Drop SC BBH 18 SC BBH 20 SC BBH 22 Tertiary C ◎◎ ◎ ◎ ◎ ◎ ◎ Asphalt Road BBH 16 BBH 17 Seberang BBH 19 Sungai BBH 21 Piruko SC Kalang SC Siat MC Source: JICA Survey Team Figure 5.3.7 Schematic Diagram of Batang Hari Irrigation System (BBH1-BBH22) As listed in Table 5.3.3, the Batang Hari main canal has four drop works and 28 diversion works in total. Table 5.3.3 List of Drop Works and Diversion Works of Main Canal Drop Works Discharge Drop Height (m3/s) (m) BBH.7c 20.90 0.74 BBH.11a 17.59 0.92 BBH.13b 13.08 1.24 BBH.23a 9.04 0.42 Diversion Discharge Drop Height Diversion Discharge Drop Height Works (m3/s) (m) Works (m3/s) (m) BBH.1 25.20 1.03 BBH.15 12.05 0.00 BBH.2 23.81 1.26 BBH.16 11.53 1.10 BBH.3 23.39 1.86 BBH.17 11.04 0.43 BBH.4 22.11 0.00 BBH.18 10.67 0.00 BBH.5 21.91 0.00 BBH.19 10.51 0.70 BBH.6 21.52 1.23 BBH.20 9.80 0.00 BBH.7 20.90 1.00 BBH.21 9.60 0.62 BBH.8 20.54 0.92 BBH.22 9.16 0.38 BBH.9 19.96 0.00 BBH.23 9.04 0.53 BBH.10 19.64 0.93 BBH.24 8.49 0.38 BBH.11 17.59 1.64 BBH.25 8.14 0.00 BBH.12 15.20 1.17 BBH.26 7.96 0.00 BBH.13 13.08 0.45 BBH.27 7.63 0.00 BBH.14 12.38 0.00 BBH.28 7.29 0.00 Source: Design Report of Irrigation and Drainage System- May 1996 5-20 In case that there is sufficient head at the drop works or diversion works, the power generation is enabled by providing a penstock for another passage and generating equipment at the terminal of the penstock. However, as shown above, all drop works and diversion works have low heads of less than 2 m. As shown in Figure 5.3.8, the actual drop heights as built were also checked during the field survey and were confirmed to be the same as the designed. Headworks Topographic condition is not preferableBBH3. BBH11 Figure 5.3.8 Diversion Structures (BBH3 and BBH11) The types of turbines applicable to a head less than 2 m are limited to the following: - Undershot water wheel; - Archimedes screw; and - Very Low Head (VLH) turbine. The undershot water wheel is a simple system in which a water wheel is placed over a fast water flow. Generally, it is applicable for a head of 1.0-2.0 m. Such system had been widely used in power milling of flour as well as in other industries all over the world. However, its generating capacity is limited only to about 10 kW at the maximum. The Archimedes screw is made up of helix-shaped blades mounted on a central shaft, which is put in a trough at an angle to pump water up. By reversing this pump, the Archimedes screw can also be used to generate electricity. Generally, it is applicable for a head of 1.0-4.0 m. Such system had been used mainly in European countries, and not yet in Indonesia. According to the result of a hearing survey with European manufacturers, the machine would cost US$4,000/kW, excluding installation, transportation, and civil works. Such price level is not competitive to ensure viability of the projects in this Survey. The VLH turbine is a brand-new design concept developed by a European company to increase the size of Kaplan turbine runner diameter and to integrate a self-supporting structure therein. It is applicable for a head of 1.5-2.5 m. This type of turbine is still in the industrialization phase limited only to European countries, and not yet ready to be exported to Asian countries. Since all the three types of turbine are found not applicable, the plan using drop works and diversion works is discarded from further examination in this Survey. 5-21 In case of a siphon which is facilitated at one site on the downstream part of the main canal and six sites on secondary canals, each siphon has a head of less than 2.0 m. Citing the examination results on possibility of using drop works with a similar head, there is no potential siphon site from the technical and economical viewpoints. 5.3.3 Power Generation Plan Using Headworks Power generation utilizing the head difference between the upstream and downstream of the Batang Hari headworks is also conceivable. Such kind of power development was already implemented in Indonesia; at the Lodoyo Power Station in the East Java Province. The Lodoyo Power Station has an installed capacity of 4.5 MW by utilizing a head difference of 9.5 m and discharge of 57.5 m3/s However, there are two specific problems in case of the Batang Hari headworks.