pywr.nodes.RollingVirtualStorage

class pywr.nodes.RollingVirtualStorage(*args, **kwargs)

A rolling virtual storage node useful for implementing rolling licences.

The volume of the node is updated each timestep with the volume of water utilised in the timestep immediately prior to the rolling period.

If the initial volume of the storage is less than the maximum volume then the parameter will calculate an initial utilisation value. This is set equal to: (max volume - initial volume) / (timesteps - 1). This utilisation is assumed to occurred equally across each timestep of the rolling period. The storage is replenished by this value for each timestep until a full rolling period is completed. At this point, replenishment will be based on the previous utilisation of the storage during the model run. Note that this changes the previous default behaviour of the node up to Pywr version 1.17.1, where no initial utilisation was calculated. This meant that it was impossible for the storage volume to be higher than the initial volume even if this was lower than the max volume.

Parameters:

model: pywr.core.Model

name: str

The name of the virtual node

nodes: list of nodes

List of inflow/out flow nodes that affect the storage volume

factors: list of floats

List of factors to multiply node flow by. Positive factors remove water from the storage, negative factors remove it.

min_volume: float or parameter

The minimum volume the storage is allowed to reach.

max_volume: float or parameter

The maximum volume of the storage.

initial_volume, initial_volume_pcfloat (optional)

Specify initial volume in either absolute or proportional terms. Both are required if max_volume is a parameter because the parameter will not be evaluated at the first time-step. If both are given and max_volume is not a Parameter, then the absolute value is ignored.

timestepsint

The number of timesteps to apply to the rolling storage over.

daysint

The number of days to apply the rolling storage over. Specifying a number of days (instead of a number of timesteps) is only valid with models running a timestep of daily frequency.

cost: float or parameter

The cost of flow into/outfrom the storage.

Notes

TODO: The cost property is not currently respected. See issue #242.

__init__(model, name, nodes, **kwargs)

Methods

__init__(model, name, nodes, **kwargs)
after(self, Timestep ts, double[)
before(self, Timestep ts)	Called at the beginning of the timestep
check(self)
commit(self, int scenario_index, double value)	Called once for each route the node is a member of
commit_all(self, double[)	Called once for each route the node is a member of
finalise_load()	Finish loading a node by converting parameter name references to instance references.
finish(self)
get_all_cost(self, double[)
get_all_max_volume(self, double[)
get_all_min_volume(self, double[)
get_area(self, ScenarioIndex scenario_index)
get_cost(self, ScenarioIndex scenario_index)	Get the cost per unit flow at a given timestep
get_current_pc(self, ...)	Return the current proportion of full of the storage node.
get_initial_pc(self)	Returns the initial volume as a proportion.
get_initial_volume(self)	Returns the absolute initial volume.
get_level(self, ScenarioIndex scenario_index)
get_max_volume(self, ...)
get_min_volume(self, ...)
pre_load(model, data)	Create a node instance from data.
reset(self)
setup(self, model)

Attributes

active	active: 'bool'
allow_isolated	A property to flag whether this Node can be unconnected in a network.
area
comment	comment: basestring
component_attrs
components	Generator that returns all of the Components attached to the Node
cost	The cost per unit increased in volume stored
current_pc	Current proportion full.
domain
factors
flow	Total flow via this node in the current timestep
fully_qualified_name
has_fixed_cost	Returns true if cost is not a Parameter.
initial_volume
initial_volume_pc
level
max_volume
min_volume
model	The recorder for the node, e.g. a NumpyArrayRecorder.
name	Name of the node.
nodes
parent	The parent Node/Storage of this object.
prev_flow	Total flow via this node in the previous timestep
recorders	Returns a list of pywr.recorders.Recorder objects attached to this node.
timesteps	timesteps: 'int'
virtual	virtual: 'bool'
volume