Table 1.

Summary of input data

Quantity	Symbol	Value
Storage energy capacity	$E_{\text{max}}$	12 MWh
RE generation capacity (if present)	$P_{\text{max}}$	10 MW
Time to fully charge or discharge the storage	τ	4 h
Charging efficiency	${\eta }_{\text{C}}$	0.95
Discharging efficiency	${\eta }_{\text{D}}$	0.95
Number of time intervals for periodicity constraint	Φ	24
Number of time intervals for discharge constraint	ε	24
Maximum energy discharged during one day	Ε	12 MWh
Discount rate (yearly)	r	7.5%
Length of time step	$\text{Δ}t$	1 h
Start date of the contract		2015-01-01/2030-01-01
End date of the contract		2019-12-31/2034-12-31
Countries (number of solar, wind projects)		Germany (5,5), Denmark (6,5),
		Spain (5,5), Finland (5,5), Italy (5,5),
		Sweden (4,5), United Kingdom (5,5)

Reference storage unit for the assessment of proxy storage PPAs.