Pondage refers to water buildup behind larger run-of-the-river systems. It involves storing a small amount of water during times of low demand and using it during peak periods when demand is highest.
Water Storage and Usage in Pondage
During periods of low electricity demand or when the plant is inactive, water that would otherwise be wasted is stored instead of flowing through the spillways. This stored water in the pondage is later used when needed, leading to water elevation changes of 1-1.5 meters during system operation.
Increased Efficiency with Pondage in Run-of-the-River Systems
Having a significant amount of pondage enables run-of-the-river systems to operate fully even during off-peak periods. This capability allows the plant to adjust to hourly fluctuations in energy demand more effectively, resulting in improved efficiency compared to systems without this water buildup.
Advantages of this Water Buildup
- It increases the efficiency of the plant.
- It stores excess water during periods of low power demand.
- It helps meet immediate increases in power demand.
Disadvantages of this Water Buildup
- It increases the initial investment required for the plant.
- It involves additional civil work.
- It requires extra manpower for operation and maintenance.
The capacity of the pond can be calculated using a similar method to that of determining the capacity of the reservoir. However, in this case, the demand is determined by the chronological load curve. It is clear that the need for pondage arises because the power plants usually operate at a load factor below 100 percent. If it were possible to run a hydro plant at a 100 percent load factor, pondage would not be necessary.