Overview
The Hatanagi-I Dam is a significant hydraulic engineering structure located on the Ōi River in Aoi-ku, Shizuoka, within Shizuoka Prefecture on the island of Honshū, Japan. It functions as the primary water retention structure for a pumped-storage hydroelectric power station, serving as a critical component of the regional energy infrastructure. The facility is owned and operated by the Chubu Electric Power Company, which utilizes the dam to manage water flow for electricity generation. The power station associated with the dam has an installed capacity of 137 megawatts, contributing to the operational grid of the Chubu region. The dam was commissioned in 1962, marking the beginning of its long-term operational history in the Japanese energy sector.
A defining characteristic of the Hatanagi-I Dam is its structural design, which classifies it as a hollow-core concrete gravity dam. With a height of 125 metres, it holds the distinction of being the tallest hollow-core concrete gravity dam in the world. This specific engineering approach involves constructing the dam with internal voids or cores, which reduces the overall volume of concrete required while maintaining structural stability through gravity forces. The 125-metre elevation allows for significant hydraulic head, which is essential for the efficiency of the pumped-storage mechanism. The use of hollow-core technology represents a notable advancement in dam construction, balancing material efficiency with the need for robust water retention in the mountainous terrain of Shizuoka Prefecture.
The integration of the dam with the 137 MW pumped-storage facility highlights its role in energy management. Pumped-storage hydroelectricity serves as a flexible power source, capable of storing energy by moving water between upper and lower reservoirs during periods of low demand and releasing it to generate power during peak usage. The Hatanagi-I Dam’s location on the Ōi River provides the necessary geographical features for this cycle. As an operational facility since 1962, the dam continues to support the Chubu Electric Power Company’s efforts to balance supply and demand in the regional power grid. Its status as the world’s tallest of its specific structural type underscores the engineering precision required to maintain such a large-scale infrastructure project in the Japanese landscape.
Engineering Design and Specifications
The Hatanagi-I Dam is a hollow-core concrete gravity dam located on the Ōi River in Aoi-ku, Shizuoka Prefecture, Japan.
The dam supports a pumped-storage hydroelectric power station with an installed capacity of 137 MW. The facility is owned and operated by the Chubu Electric Power Company. The system utilizes water as its primary energy source, functioning as a pumped-storage plant that was commissioned in 1962.
Technical Parameters
| Parameter | Value |
|---|---|
| Entity Type | Pumped Storage |
| Dam Type | Hollow-core concrete gravity dam |
| Height | 125 metres |
| Location | Ōi River, Aoi-ku, Shizuoka Prefecture, Japan |
| Capacity | 137 MW |
| Operator | Chubu Electric Power |
| Commissioned | 1962 |
| Status | Operational |
How does the Hatanagi-I pumped-storage system work?
The Hatanagi-I pumped-storage system operates as a closed-loop hydroelectric facility, utilizing water as its primary energy carrier within the Chubu Electric Power network. The core of this operational model lies in the interaction between two distinct structures: the Hatanagi No.1 dam and the Hatanagi No.2 dam. These two dams create the necessary elevation difference and reservoir capacity required for efficient energy storage and retrieval. The system does not rely on a single static reservoir but rather a dynamic interplay between an upper basin and a lower basin, allowing water to be cycled repeatedly through the turbine generators. This closed-loop configuration minimizes water loss through evaporation and seepage compared to traditional run-of-the-river schemes, making it highly efficient for daily load balancing on the island of Honshū.
Reversible Turbine Generators
The heart of the Hatanagi-I station is its 137 megawatts (184,000 hp) of installed capacity, driven by reversible turbine generators. These sophisticated mechanical units perform a dual function: they act as turbines during power generation and as pumps during energy storage. When electricity demand in the Chubu region peaks, typically during midday or early evening, water is released from the upper reservoir. The water flows downward, spinning the turbine blades and driving the generator to produce electricity. Conversely, when electricity supply exceeds immediate demand—often during the night or on windy days—the generators reverse their rotation. They draw power from the grid to drive the turbines, effectively acting as pumps that lift water back up to the upper reservoir. This reversibility allows the station to store excess energy as potential energy in the form of elevated water, ready to be converted back into kinetic and then electrical energy when needed.
The 5 km Penstock and Hydraulic Head
Connecting the upper reservoir to the powerhouse is a massive 5 km penstock. This long, pressurized conduit is critical to the system's efficiency, channeling water from the higher elevation of the Hatanagi No.1 dam down to the turbine hall. The significant length of the penstock, combined with the 125-metre height of the hollow-core concrete gravity dam, creates a substantial hydraulic head. This high pressure ensures that the water strikes the turbine blades with considerable force, maximizing the energy extracted per cubic meter of water. The penstock must withstand immense internal pressures and thermal fluctuations, requiring robust engineering to prevent fatigue over decades of operation. The design of this 5 km route was carefully planned to optimize the balance between construction cost and hydraulic efficiency, ensuring minimal friction losses as water travels from the source to the generator. This infrastructure allows the Chubu Electric Power Company to rapidly adjust output, responding to grid frequency changes within minutes, a key advantage of pumped-storage hydroelectricity.
Why it matters
The Hatanagi-I Dam holds a distinct position in global civil and hydraulic engineering as the tallest hollow-core concrete gravity dam in the world. With a structural height of 125 metres (410 ft), this facility represents a significant achievement in dam construction technology, utilizing a hollow-core design to optimize material usage and structural stability for a gravity dam of its scale. This specific engineering classification distinguishes it from solid gravity dams or arch dams, highlighting the technical innovations applied to the Ōi River in Aoi-ku, Shizuoka Prefecture, Japan. The dam's prominence is not merely architectural but functional, serving as the critical headwater structure for a major hydroelectric asset.
Post-War Energy Infrastructure Role
Commissioned in 1962, the Hatanagi-I Dam and its associated power station were integral to Japan's rapid post-war energy expansion. During this period, the nation required robust and flexible power sources to fuel industrial growth, and pumped-storage hydroelectricity emerged as a key solution for load balancing. The facility, owned and operated by the Chubu Electric Power Company, supports a 137 MW (184,000 hp) pumped-storage hydroelectric power station. This capacity allows the grid to store excess energy during off-peak hours by pumping water to the upper reservoir and releasing it through turbines during peak demand, providing essential grid stability for the Chubu region on the island of Honshū. The operational status of the dam remains active, demonstrating the longevity and reliability of the infrastructure established in the early 1960s.
Engineering Significance
The designation as the world's tallest hollow-core concrete gravity dam underscores the technical rigor applied to the Hatanagi-I project. Hollow-core gravity dams utilize a series of vertical or horizontal voids within the dam body, which can reduce the volume of concrete required compared to a solid section while maintaining the gravitational force needed to resist water pressure. This design choice reflects the engineering priorities of the era, balancing cost-efficiency with structural integrity for a 125-metre high structure. The dam's location on the Ōi River in Shizuoka Prefecture provides the necessary topographical gradient for effective pumped-storage operations, further enhancing its strategic value to the regional energy mix. The facility continues to serve as a benchmark for similar dam constructions globally, illustrating the enduring relevance of mid-20th-century hydraulic engineering solutions in modern energy infrastructure.
Water Resource Management
The Hatanagi-I Dam creates a significant reservoir that serves as a critical node in the water resource management infrastructure of Shizuoka Prefecture. While the facility is primarily recognized for its status as the tallest hollow-core concrete gravity dam in the world, its hydrological function extends beyond hydroelectric generation to support regional water supply networks. The reservoir, commonly referred to as Hatanagi Lake, functions as a primary source for tap water distribution, industrial water usage, and agricultural irrigation across the prefecture. This multi-purpose utilization maximizes the efficiency of the captured water from the Ōi River, which flows through Aoi-ku, Shizuoka, on the island of Honshū. The integration of water storage for municipal and industrial needs alongside energy production is a defining characteristic of the Chubu Electric Power Company’s operational strategy for the facility. The dam’s height of 125 metres provides the necessary hydraulic head and storage volume to regulate flow, ensuring consistent water availability for downstream users even during periods of variable precipitation. The management of these water resources requires careful balancing between the demands of the 137 MW pumped-storage hydroelectric power station and the steady consumption patterns of the surrounding communities and industries. The reservoir’s role in supplying tap water highlights its importance to public health and urban development in the region, while its contribution to industrial water supply supports the manufacturing sectors that rely on the Chubu Electric Power grid. Agricultural irrigation remains a vital component of the water allocation, sustaining crop production in the fertile lands of Shizuoka Prefecture. The operational status of the dam, which has been active since its commissioning in 1962, underscores the long-term reliability of this water management infrastructure. The continuous operation of the Hatanagi-I Dam ensures that the water resources are effectively harnessed to meet the evolving needs of the region, balancing energy generation with essential water supply functions. The facility’s design as a hollow-core concrete gravity dam allows for efficient water retention and structural stability, contributing to the overall reliability of the water resource management system. The coordination between the Chubu Electric Power Company and local water authorities ensures that the reservoir levels are maintained to optimize both energy output and water availability. This integrated approach to water resource management exemplifies the strategic importance of the Hatanagi-I Dam in the broader context of Shizuoka Prefecture’s infrastructure. The dam’s contribution to the region’s water security is a testament to the effective planning and engineering that underpin its operation. The reservoir serves as a vital buffer against seasonal fluctuations in water availability, providing a stable source for both domestic and industrial consumers. The ongoing maintenance and operation of the Hatanagi-I Dam continue to support the economic and social development of the region through reliable water and energy supply. The facility’s role in water resource management is integral to the sustainability of the local ecosystem and the prosperity of the communities that depend on it. The strategic location on the Ōi River allows for efficient capture and distribution of water resources, enhancing the overall resilience of the regional water supply network. The Hatanagi-I Dam remains a cornerstone of water infrastructure in Shizuoka, demonstrating the enduring value of integrated water and energy management systems.