The Power Demand time series file contains the four following items
1. Target power. Target power demand, either as Target Power [MW or equivalent] or as Water Flow [m3/s or equivalent].
2. Installed capacity, effective only when ‘Create item for surplus capacity fraction’ is selected under the Surplus capacity fraction tab, but must always be present and non-blank. Specified as Power [MW or equivalent] or as Discharge [m3/s or equivalent].
3. Fraction. Surplus capacity Usage [dimensionless]. Fraction between 0 and 1. If this value is greater than 0, then a fraction of excess turbine capacity can be used for releases triggered by flood control, global ranking, and storage demand rules.
4. Head difference. Minimum head for turbine operation, specified as Head Difference [m or equivalent]. If head (difference between reservoir level and tailwater level or reservoir bottom level if no tailwater is specified) drops below this threshold, no water is routed through the turbines, regardless of power demand.
5. Minimum flow. Minimum flow for turbine operation, specified as Discharge [m3/s or equivalent].
The option to produce more power than demanded (up to installed engine capacity) at times where there is a surplus of water in the Reservoir is applicable when the reservoir water level is above Flood control level. Water that would otherwise be spilled can be routed through a turbine. Any release that - due to limited turbine capacity - cannot be exploited for hydropower generation is spilled from the Reservoir.
In addition, releases triggered as a result of global ranking and storage demand rules are also routed through hydropower, provided that capacity is available and the amount to be released exceeds the minimum flow required for turbine operation.