Custom constraints¶
Custom-made shared limit for Flows¶
General description¶
This script shows how to add an individual constraint to the oemof solph OperationalModel. The constraint we add forces a flow to be greater or equal a certain share of all inflows of its target bus. Moreover we will set an emission constraint.
Code¶
Download source code: add_constraints.py
Click to display code
import logging
import pandas as pd
import pyomo.environ as po
from oemof.solph import Bus
from oemof.solph import EnergySystem
from oemof.solph import Flow
from oemof.solph import Model
from oemof.solph import components as cmp
def run_add_constraints_example(solver="cbc", nologg=False):
if not nologg:
logging.basicConfig(level=logging.INFO)
# ##### creating an oemof solph optimization model, nothing special here ##
# create an energy system object for the oemof solph nodes
es = EnergySystem(
timeindex=pd.date_range("1/1/2017", periods=5, freq="h"),
infer_last_interval=False,
)
# add some nodes
boil = Bus(label="oil", balanced=False)
blig = Bus(label="lignite", balanced=False)
b_el = Bus(label="b_el")
es.add(boil, blig, b_el)
sink = cmp.Sink(
label="Sink",
inputs={b_el: Flow(nominal_capacity=40, fix=[0.5, 0.4, 0.3, 1])},
)
pp_oil = cmp.Converter(
label="pp_oil",
inputs={boil: Flow()},
outputs={b_el: Flow(nominal_capacity=50, variable_costs=25)},
conversion_factors={b_el: 0.39},
)
pp_lig = cmp.Converter(
label="pp_lig",
inputs={blig: Flow()},
outputs={b_el: Flow(nominal_capacity=50, variable_costs=10)},
conversion_factors={b_el: 0.41},
)
es.add(sink, pp_oil, pp_lig)
# create the model
om = Model(energysystem=es)
# add specific emission values to flow objects if source is a commodity bus
for s, t in om.flows.keys():
if s is boil:
om.flows[s, t].emission_factor = 0.27 # t/MWh
if s is blig:
om.flows[s, t].emission_factor = 0.39 # t/MWh
emission_limit = 60e3
# add the outflow share
om.flows[(boil, pp_oil)].outflow_share = [1, 0.5, 0, 0.3]
# Now we are going to add a 'sub-model' and add a user specific constraint
# first we add a pyomo Block() instance that we can use to add our
# constraints. Then, we add this Block to our previous defined
# Model instance and add the constraints.
myblock = po.Block()
# create a pyomo set with the flows (i.e. list of tuples),
# there will of course be only one flow inside this set, the one we used to
# add outflow_share
myblock.MYFLOWS = po.Set(
initialize=[
k for (k, v) in om.flows.items() if hasattr(v, "outflow_share")
]
)
# pyomo does not need a po.Set, we can use a simple list as well
myblock.COMMODITYFLOWS = [
k for (k, v) in om.flows.items() if hasattr(v, "emission_factor")
]
# add the sub-model to the oemof Model instance
om.add_component("MyBlock", myblock)
def _inflow_share_rule(m, s, e, t):
"""pyomo rule definition: Here we can use all objects from the block or
the om object, in this case we don't need anything from the block
except the newly defined set MYFLOWS.
"""
expr = om.flow[s, e, t] >= om.flows[s, e].outflow_share[t] * sum(
om.flow[i, o, t] for (i, o) in om.FLOWS if o == e
)
return expr
myblock.inflow_share = po.Constraint(
myblock.MYFLOWS, om.TIMESTEPS, rule=_inflow_share_rule
)
# add emission constraint
myblock.emission_constr = po.Constraint(
expr=(
sum(
om.flow[i, o, t]
for (i, o) in myblock.COMMODITYFLOWS
for t in om.TIMESTEPS
)
<= emission_limit
)
)
# solve and write results to dictionary
# you may print the model with om.pprint()
om.solve(solver=solver)
logging.info("Successfully finished.")
if __name__ == "__main__":
run_add_constraints_example()
Installation requirements¶
This example requires oemof.solph (v0.5.x), install by:
pip install oemof.solph[examples]
To draw the graph pygraphviz is required, installed by:
pip install pygraphviz
License¶
Simon Hilpert - 31.10.2016 - simon.hilpert@uni-flensburg.de
Charge-rate depending on state-of-charge¶
General description¶
Example that shows the how to implement a GenericStorage that charges at reduced rates for high storage contents.
Code¶
Download source code: saturating_storage.py
Click to display code
import pandas as pd
from pyomo import environ as po
from matplotlib import pyplot as plt
from oemof import solph
def saturating_storage_example():
# create an energy system
idx = pd.date_range("1/1/2023", periods=100, freq="h")
es = solph.EnergySystem(timeindex=idx, infer_last_interval=False)
# power bus
bel = solph.Bus(label="bel")
es.add(bel)
es.add(
solph.components.Source(
label="source_el",
outputs={bel: solph.Flow(nominal_capacity=1, fix=1)},
)
)
es.add(
solph.components.Sink(
label="sink_el",
inputs={
bel: solph.Flow(
nominal_capacity=1,
variable_costs=1,
)
},
)
)
# Electric Storage
inflow_capacity = 0.5
full_charging_limit = 0.4
storage_capacity = 10
battery = solph.components.GenericStorage(
label="battery",
nominal_capacity=storage_capacity,
inputs={bel: solph.Flow(nominal_capacity=inflow_capacity)},
outputs={bel: solph.Flow(variable_costs=2)},
initial_storage_level=0,
balanced=False,
loss_rate=0.0001,
)
es.add(battery)
# create an optimization problem and solve it
model = solph.Model(es)
def soc_limit_rule(m):
for p, ts in m.TIMEINDEX:
soc = (
m.GenericStorageBlock.storage_content[battery, ts + 1]
/ storage_capacity
)
expr = (1 - soc) / (1 - full_charging_limit) >= m.flow[
bel, battery, p, ts
] / inflow_capacity
getattr(m, "soc_limit").add((p, ts), expr)
setattr(
model,
"soc_limit",
po.Constraint(
model.TIMEINDEX,
noruleinit=True,
),
)
setattr(
model,
"soc_limit_build",
po.BuildAction(rule=soc_limit_rule),
)
# solve model
model.solve(solver="cbc")
# create result object
results = solph.processing.results(model)
plt.plot(results[(battery, None)]["sequences"], "r--", label="content")
plt.step(
20 * results[(bel, battery)]["sequences"], "b-", label="20*inflow"
)
plt.legend()
plt.grid()
plt.figure()
plt.plot(
results[(battery, None)]["sequences"][1:],
results[(bel, battery)]["sequences"][:-1],
"b-",
)
plt.grid()
plt.xlabel("Storage content")
plt.ylabel("Charging power")
plt.show()
if __name__ == "__main__":
saturating_storage_example()
Installation requirements¶
This example requires oemof.solph (v0.5.x), install by:
pip install oemof.solph[examples]
