Operational reserve constraint with energy storage

[pz-max]

• Here the GenX publication. Page 31 last & page 32 first paragraph talks about energy storage play a role for reserves (incl hydro etc).

• Our current PyPSA-Eur implementation does not consider energy storage
  

  pypsa-eur/scripts/solve_network.py

  Lines 733 to 790 in 3fba8da

  	def add_operational_reserve_margin(n, sns, config):
  	"""
  	Build reserve margin constraints based on the formulation given in
  	https://genxproject.github.io/GenX/dev/core/#Reserves.
  	Parameters
  	----------
  	n : pypsa.Network
  	sns: pd.DatetimeIndex
  	config : dict
  	Example:
  	--------
  	config.yaml requires to specify operational_reserve:
  	operational_reserve: # like https://genxproject.github.io/GenX/dev/core/#Reserves
  	activate: true
  	epsilon_load: 0.02 # percentage of load at each snapshot
  	epsilon_vres: 0.02 # percentage of VRES at each snapshot
  	contingency: 400000 # MW
  	"""
  	reserve_config = config["electricity"]["operational_reserve"]
  	EPSILON_LOAD = reserve_config["epsilon_load"]
  	EPSILON_VRES = reserve_config["epsilon_vres"]
  	CONTINGENCY = reserve_config["contingency"]
  	# Reserve Variables
  	n.model.add_variables(
  	0, np.inf, coords=[sns, n.generators.index], name="Generator-r"
  	)
  	reserve = n.model["Generator-r"]
  	summed_reserve = reserve.sum("Generator")
  	# Share of extendable renewable capacities
  	ext_i = n.generators.query("p_nom_extendable").index
  	vres_i = n.generators_t.p_max_pu.columns
  	if not ext_i.empty and not vres_i.empty:
  	capacity_factor = n.generators_t.p_max_pu[vres_i.intersection(ext_i)]
  	p_nom_vres = (
  	n.model["Generator-p_nom"]
  	.loc[vres_i.intersection(ext_i)]
  	.rename({"Generator-ext": "Generator"})
  	)
  	lhs = summed_reserve + (
  	p_nom_vres * (-EPSILON_VRES * xr.DataArray(capacity_factor))
  	).sum("Generator")
  	# Total demand per t
  	demand = get_as_dense(n, "Load", "p_set").sum(axis=1)
  	# VRES potential of non extendable generators
  	capacity_factor = n.generators_t.p_max_pu[vres_i.difference(ext_i)]
  	renewable_capacity = n.generators.p_nom[vres_i.difference(ext_i)]
  	potential = (capacity_factor * renewable_capacity).sum(axis=1)
  	# Right-hand-side
  	rhs = EPSILON_LOAD * demand + EPSILON_VRES * potential + CONTINGENCY
  	n.model.add_constraints(lhs >= rhs, name="reserve_margin")

Energy storage should be considered. However, because not all markets might consider storage as a reserve contributor, it should be implemented as an option.

Implementation idea:

• Avoid introducing if conditions
• Write in config a boolean (True/False aka. 1/0) for storage addition in the reserve constraint
• Add terms to the lhs and rhs for the constraint (see here). rhs= old terms + new term * boolean
• One challenge will be to properly understand what term to add on the lhs and rhs side... Good documentation for the new term will be essential

[fneum]

related #643

[pz-max]

Status. This feature request is of interest to the maintainers.
Now, someone just needs to work on adding a good PR to address this.