Pumped Storage Hydropower: Benefits for Grid Reliability and Integration of Variable Renewable Energy.

摘要

Pumped storage hydropower (PSH) technologies have long provided a form of valuable energy storage for electric power systems around the world. A PSH unit typically pumps water to an upper reservoir when loads and electricity prices are low, and subsequently releases the water back to a lower reservoir through a turbine when loads are high and electricity is more expensive. Moreover, PSH is a flexible resource that contributes to balance supply and demand in the power grid and helps integrate variable renewable energy sources like wind and solar. These units can be incorporated into natural lakes, rivers, or reservoirs—so-called 'open-loop' systems—or PSH reservoirs can be constructed to be independent of existing natural water flows—so-called 'closed-loop' systems. Three main types of PSH technologies can be implemented. The most common is a fixed speed (FS) unit with pump/turbine and motor/generator that operate at a fixed synchronous speed. In recent years, adjustable speed (AS) units have become more popular due to their increased efficiency and ability to adjust their power consumption when in the pumping mode. This flexibility enables AS units to provide load-following and regulation services (i.e., respond to frequency deviations and short-term energy balancing needs in the system), which are becoming increasingly valuable as the penetration of variable renewable generation technologies, such as wind and solar, increases. Globally, more than 20 AS units have entered commercial operation since 1990. The third type of PSH technology is ternary units that can use a hydraulic bypass to provide more flexible operation, especially in the pumping mode, although this configuration is less common than AS. In the United States, 40 PSH plants are currently in operation, all of which utilize FS technology. The PSH plants provide 22 GW of total installed capacity. This accounts for 95% of all energy storage capacity in the United States.