Storage

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Reservoirs are used to store an inflow and, depending on the current content and operating regulations, to deliver water for a total of newly different uses to up to three different system elements. With the possibility to regulate and control it is an extremely flexible system element with a variety of options. Originally, the reservoir was developed to represent dams, but it is also possible to represent other reservoirs such as flood control reservoirs or similar. Optionally, an addition to the reservoir by precipitation, as well as losses at the reservoir by evaporation and infiltration can be simulated.

The system element reservoir can also be used to simulate hydro power plants.


Storage characteristic

The storage characteristic curve compares the content of the storage tank with the respective water levels and the surface. It is the basis for all calculation options that include not only the reservoir content but also the height or surface, e.g., feed/loss, weir, pressure pipe.


Release

Calculation options

Independent of the selected calculation option, the outputs can still be scaled with a system state/state group, which makes it possible to integrate complex operating rules, which are not only dependent on states within the storage element, but also on states within the entire river basin.

Output per time step/output sequence

With this option, you define the output values by directly entering output values (up to 365). These output values are output in this order for one time step at a time during the simulation.


Function (+ Graph/Time series)

The outputs are defined as content-dependent functions through the input of grid points. These outputs can additionally be scaled with a factor, a yearly, weekly and daily cycle (and, as with all calculation options, with a system state or a state group) or with a factor and a time series.

The following options are available as function types:

KNL

Kennlinie

LAM

Lamellenplan

XYZ

Zeitabhängige Funktion


Characteristic curve

For the characteristic curve, a time-independent content delivery function is entered. The interpolation points can be interpreted as steps or interpolated linearly.


Lamellenplan

With the option Lamella plan the storage content is divided into different areas (lamellas) over the year and these lamellas are each assigned a fixed delivery level. Thus, any ascending delivery levels are defined and for each fixed period of time the respective storage contents are entered for each of these delivery levels.

The supporting points of the lamella plan can be interpreted as block steps. However, it is also possible to interpolate linearly in time and/or to interpolate linearly between the grid points of the contents/output values.


Time dependent function

The time dependent function is very similar to the slat plan, but a bit more flexible: The support points for the output values must be the same for the different time periods only in number, but not in value, and they do not necessarily have to be ascending. So you can define arbitrary functions with their respective content and output values for different time periods.

By default the entered interpolation points are interpreted as block steps. However, it is also possible to interpolate linearly in time and/or to interpolate linearly between the grid points of the contents/output values.


Weir raid

The charge is calculated by the weir formula according to Poleni as a perfect / imperfect raid.


Pressure pipeline

The fee is calculated using the Prandtl-Colebrook and Darcy-Weisbach rates.


Turbine

Based on the characteristics of the turbine, the turbine flow is determined depending on the storage tank content and the underwater level, so that the desired performance is maintained as long as the maximum possible flow rate of the outlet is not exceeded. See also the page on hydropower plants.


Boundaries

The physically maximum possible output can also be entered for the individual outlet organs of the storage tank as a function of the storage tank content, which additionally limits the desired outputs. A minimum permissible discharge can also be entered here, below which the discharge is set to 0.


Internal dependencies

Internal dependencies are used to define the priorities in case of several, competing deliveries from one storage. One or more charges can be reduced if another charge exceeds a certain amount or if the memory content falls below a certain amount.

The respective limits of output and storage volume for internal dependencies are constants, which can still be scaled by constant graphs.

If several charges are reduced, the order in which they are to be reduced must also be specified.

Example: If output B > 0 and the memory content S < X, then reduce output A by the amount of output B, whereby output A may not become less than zero.

This means, that between A and B a linear dependence exists as long as B is equal to the value of A. If B rises further, A remains constant zero.


Contribution/Loss at the Reservoir

A contribution or loss at the reservoir in the form of precipitation, evaporation or infiltration can be considered via two options:

  • Constant chart (daily, weekly and/or yearly)
  • Time series

These can be scaled by a factor. The reservoir loss/contribution is additionally scaled automatically with the current storage surface