Lam Ta Khong pumped storage project is set to be the last major project developed by the Electricity Generating Authority of Thailand (EGAT) in its traditional role as the country’s vertically-integrated power utility. EGAT has played an important role in developing an efficient national electricity system for Thailand, and Lam Ta Khong will help to stabilise northeast Thailand’s power supplies.
The northeast’s 19 provinces cover an area of 169,600km2, about one-third of Thailand’s total land area, and is home to some 20M people who are mainly involved in agriculture. Annual per capita electricity consumption (1993) is steadily rising through an average of about 970kWh. Until the 275MW Theun-Hinboun hydro plant came on-line earlier this year in central Laos, demand for electricity in northeast Thailand was almost double the region’s existing generating capacity.
Theun-Hinboun, a private investment joint venture led by Thailand’s MDX Group, is operated by Electricite du Laos to supply EGAT’s northeast region with almost all of its output. But power still needs to be drawn from other EGAT regions at peak demand periods. To meet the northeast’s evening peak, Lam Ta Khong will use surplus energy to store water by day.
Although Thailand’s overall electricity demand is fast diminishing, the requirement in the northeast still shows promise. With an eventual capacity of 1000MW, and forecast to generate an annual 989GWh, Lam Ta Khong was authorised by the Royal Thai Government for inclusion in Thailand’s Seventh National Plan (1992-1966).
The existing reservoir, in operation by the Royal Irrigation Department (RID) since 1968, will be used as the EGAT stand-alone pumped storage scheme’s lower pond. With a capacity of 230M m3, and an annual average of 230M m3, the Lam Ta Khong waters play a crucial role in the socio-economy of the predominantly agricultural lower northeast.
Lam Ta Khong’s first two 250MW pump turbines are due to be commissioned in February and April 2000, respectively; the final two are scheduled to go into service in early 2003. The project got off the ground when a feasibility study was prepared in 1989 by the Japan International Cooperation Agency (JICA). The northeast’s Khon Kaen University also conducted a detailed environmental impact study (EIA). EGAT then submitted the project for evaluation by the National Economic and Social Development Board, prior to final approval by Royal Thai Government in early 1994.
The total cost of the Lam Ta Khong project was assessed at 21,800M Thai baht (Bt) (US$872M 1994 figures), with Bt12,195M in foreign currency and the rest in Thai domestic funds. The foreign currency portion, as well as some of the local currency portion for construction supervision, was financed by loans from the International Bank for Reconstruction and Development and Japan’s Overseas Economic Co-operation Fund (OECF). The remaining local currency came from EGAT revenue and Thai commercial banks. Work started on the Lam Ta Khong project in February 1994; by July 1998 the two-unit Stage 1 was 40% complete, only very slightly behind schedule.
A four-part environmental mitigation programme for Lam Ta Khong, based on Kon Khaen University’s EIA, has been given a Bt236M (US$9.4M) budget by EGAT. Along with traditional environmental protection factors such as reducing soil erosion and protecting fish and wildlife, the plan includes a number of measures to improve the quality of life for local people, mainly farmers and fishermen. For the upper pond EGAT acquired about 26ha of land from two villages on the forested plateau above the lower reservoir.
Some 350m above the Lam Ta Khong lower reservoir, the rectangular upper pond is under construction, bound by a rock-filled retaining dike lined with an asphaltic membrane. With an area of 0.34km2 and a depth of 48m, the upper storage pond will have an effective storage capacity of 9.9M m3. Twin morning glory intakes lead into two 690m-long penstocks which plunge beneath the main Bangkok-Nakhon Ratchisima highway to reach reversible pump-turbines. The horseshoe-shaped cavern powerhouse is located 350m below ground; surge tanks of the pump-turbines are actually 40m below the surface of the lower reservoir. The system is designed to pump about 9M m3 of water daily into the upper storage reservoir, using surplus power from the EGAT grid.
Lead civil works contractor for EGAT’s Lam Ta Khong project is an international joint venture between three companies, Vianini (Italy), Dragados (Spain) and Nawarat (Thailand), while project management and engineering is in the hands of Japan’s Electric Power Development Co. Pump-turbines, generator-motors and power station systems are being supplied and installed by a French consortium consisting of CEGELEC, GEC, Alsthom-Neyrpic and GEC Alsthom Electromecanique. Supply and installation of transformers and fire extinguisher systems is by Japan’s Sumitomo Corporation.
Japan’s Hazama Corporation Ltd is engaged in excavating some 1.2km of tunnels and galleries, while Spain’s ABB Hidro Equipmamentos partners ABB Hidro Electricos SA in the supply and installation of hydraulic systems, including intake gates and penstock and tailrace linings. The switchyard and associated switchgear comes jointly from Siemens AG and Siemens Ltd, while the telecommunications contract was awarded to Fujikura and the control system was won by Mitsubishi Corporation.
Freshwater fisheries are a vital factor in the northeast’s domestic economy, so EGAT paid particular attention to the design of the hydro power station’s outflow into the Lam Ta Khong reservoir. Several studies were made by scientists of the Asian Institute of Technology (AIT), Bangkok, into formulating a design for the tailrace and outflow, to minimise disturbance to aquatic creatures resident in the reservoir. The first pumped storage project in Asia to feature an underground powerhouse, Lam Ta Khong also has over 20km of tunnels and galleries. AIT research included special design features to ensure adequate stability and drainage in the loose alternate layers of sedimentary sandstone and silkstone prevalent in the terrain of the Pak Chong district.
Since the late 1980s, demand for electricity in Thailand has increased by 10-15% annually. To meet surging demand, EGAT has turned more and more to thermal plants, owing to their shorter lead time and the limited national resources remaining for hydro power development. The large base load capacity developed by thermal plant results in surplus power availability in off-peak period. Pumped storage units have already been added by EGAT to both Bhumibol (Tak) and Srinagarind (Kanchanaburi) hydro power stations. EGAT would like to add another pumped-storage unit to Bhumibol, as well as similarly equip Chulabhorn (Chaiyaphum). Thus pumped storage technology and operation fits into the daily power demand scenario.
Development of a second stand-alone pumped-storage project, the Khirithan scheme for southeast Thailand’s Chantaburi province, has been put on-hold by EGAT for two years, or until the economic smoke clears in Asia. Plans for Khirithan construction were well advanced, but EGAT is now in a wait-and-see mode. According to Vatana Meevasana, of EGAT’s Hydro Power Construction Division, the Lam Ta Khong project Stage 1 should be completed within the original budget, despite some 70% devaluation of the Thai baht since its epochal flotation in July 1997. EGAT is somewhat economically insulated in this case by World Bank and OECF hard currency funding. Project cost for installation of the final Stage 2 twin units, however, may be a different story.
EGAT has identified at least 40 more sites suitable for pumped storage development of some sort, and the total pumped storage potential is assessed by EGAT to be 32,110MW.
Self-sufficiency has become Thailand’s plan for survival in a hostile global economy. The high cost of capital equipment, much of it sourced overseas and costed in expensive hard currency, is a stumbling block. But EGAT plans greater pumped storage development, to meet an increasing proportion of energy demand in Thailand.