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Basic Principles of Pumped-Storage Power Stations

A pumped-storage power station functions like a "giant power bank," utilizing surplus electricity during off-peak hours to pump water for storage and generating electricity during peak hours. Its operation is based on the mutual conversion of water's potential energy and electrical energy, achieved by switching between "pumping" and "generating" modes to enable the spatial and temporal transfer of electricity. The specific process is as follows:

Core Components

The operation of a pumped-storage power station with the "two reservoirs, one tunnel and one power unit" configuration relies on a specialized hydraulic and electrical system, primarily consisting of:

Upper Reservoir: Located at a higher elevation (typically formed by natural terrain or artificial dams), it serves as the "energy storage reservoir," holding water pumped during the storage phase.

Lower Reservoir: Situated at a lower elevation, it acts as the "water source reservoir," receiving water released from the upper reservoir during the generation phase and providing water for pumping.

Water Conveyance System: Includes water diversion tunnels, pressure pipelines, and tailrace tunnels, connecting the upper and lower reservoirs for water flow.

Powerhouse: Equipped with reversible turbine-generator units (core equipment), which can operate either as pumps for water storage or as turbines for electricity generation.
Two Operational Modes: Pumping for Storage and Releasing Water for Generation

(1) Pumping Mode (Energy Consumption Phase)

During off-peak hours (e.g., nights, weekends, when electricity demand is low and renewable energy like wind or solar may be surplus), the station activates the "pumping" mode.

Surplus grid electricity drives the reversible units to pump water from the lower reservoir to the upper reservoir via the pressure pipelines. This process converts electrical energy into gravitational potential energy (stored as elevated water), effectively preserving "excess electricity" in the form of water's potential energy. For example, during nights when thermal or wind power generation is surplus, the pumped-storage station consumes this electricity to pump water, avoiding energy waste.

(2) Generation Mode (Energy Supply Phase)

During peak hours (e.g., daytime high demand or insufficient renewable energy output), the station switches to "generation" mode. Water from the upper reservoir flows downward through the water conveyance system (diversion tunnels, pressure pipelines), driving the reversible units as turbines to generate electricity. This converts the water's potential energy back into electrical energy, supplementing the grid. For instance, during daytime industrial or residential demand surges or cloudy days with low solar output, the upper reservoir releases water to generate electricity, quickly filling the grid's power gap.

CRANES USED IN PUMPED-STORAGE POWER STATIONS

Depending on the operational scenarios (e.g., construction, equipment installation, maintenance), various types of cranes are employed. The main types and their applications include:

Construction Phase Cranes

Dedicated cranes are utilized during stages such as civil works, shaft excavation, and power unit installation, performing heavy-load hoisting and precision positioning.

1

Tower Cranes

Used for material hoisting (e.g., steel bars, formwork, concrete components) during powerhouse foundation excavation and concrete pouring, as well as top structure construction in underground powerhouses.

Features: High lifting height and large working radius, suitable for open-air or large-scale material handling.
2

Crawler Cranes

Employed for hoisting large equipment (e.g., generator stators, rotors, main transformers) and installing heavy components like dam concrete blocks or gates. Features: Low ground pressure, strong off-road capability, and high lifting capacity (up to hundreds of tons).
3

High-Lift Shaft Gantry Cranes

Used for hoisting excavation equipment, formwork, support materials, and debris removal during shaft construction. These cranes are designed for both outdoor and tunnel use.

Features: Lifting heights of 100–600 meters (compared to typical gantry cranes under 30 meters), vertical operation along shafts, equipped with anti-fall devices and precision control systems for confined spaces. Tunnel-installed versions require compact designs due to limited space.
4

Mobile Cranes

For short-distance transport and hoisting of small to medium equipment (e.g., pipes, valves, small motors).

Features: High mobility and rapid response, ideal for temporary or urgent tasks.

Operation and Maintenance Phase Cranes

Dedicated cranes perform equipment hoisting, overhaul, and maintenance in power stations, requiring adaptation to confined spaces and high-precision handling.

1

Tower Cranes

Installed in main or auxiliary powerhouses for precision hoisting of core components (e.g., rotors, stators, bearings) and maintenance of electrical equipment (e.g., transformers, switchgear).

Features: Equipped with a high-precision control system and anti-sway device, the lifting capacity is customized according to the equipment specifications (e.g., 300-ton class for stator hoisting). The running track is arranged along the span direction of the workshop, covering the main equipment area.
2

Gantry Cranes

Used for equipment hoisting in switchyards or transformer areas (e.g., main transformer maintenance, GIS handling) or gate maintenance at reservoirs.

Features: Gantry cranes operate on ground tracks via wheels, with a medium lifting capacity (50-200 tons), making them suitable for large-area operation zones.
3

Jib Cranes

For small component maintenance (e.g., pipes, valves, motors) in auxiliary systems or control rooms.

Features: Compact structure, can be fixed on walls or columns, with a small working radius, suitable for light lifting in narrow spaces.
4

Electric Hoists (Monorail Cranes)

For lifting small tools or parts (e.g., cable pulling, platform adjustments).

Features: Compact size, user-friendly operation, mobility on tracks when paired with monorail trolleys, and a lifting capacity typically under 5 tonnes.
5

Dam-Top Gantry Crane

Handling gate operations (intake gate, tailrace gate) including opening/closing and maintenance for upper/lower reservoirs. It moves along dam crest rails to perform hoisting, traversing, and precise alignment of gates.

Features: High lifting capacity (customized to gate weight, typically 50 to 300 tonnes), wind-resistant and waterproof design, suitable for open reservoir environments.