> Are there any TIMES attributes that can regulate input/output flows for a storage, which has no size estimation yet?

Well, you could use e.g. FLO_SHAR(r,y,p,com,'ACT','ANNUAL','UP') = 1, to have the output of com bounded by the activity (1×VAR_ACT) at the beginning of each timeslice. And with aux flows and/or UCs you can define almost any kind of (linear) relations you might consider for regulating the flows. In general, having storage processes with no capacity variable, or the same commodity IN and OUT, may cause numerical problems for the solver, unless the activity / flow levels are bounded in some way or have some impact on the OBJ (e.g. via losses defined by STG_LOSS / STG_EFF).

BTW, You have defined NCAP_BND with the description "Max capacity bound". Note that it defines a bound for the new capacity installed in the period t specified in NCAP_BND(r,t,p,bd). So, your NCAP_BND bounds in the Subres seem to be defined on the new capacity in the Base year only.

Well, you could use e.g. FLO_SHAR(r,y,p,com,'ACT','ANNUAL','UP') = 1, to have the output of com bounded by the activity (1×VAR_ACT) at the beginning of each timeslice. And with aux flows and/or UCs you can define almost any kind of (linear) relations you might consider for regulating the flows. In general, having storage processes with no capacity variable, or the same commodity IN and OUT, may cause numerical problems for the solver, unless the activity / flow levels are bounded in some way or have some impact on the OBJ (e.g. via losses defined by STG_LOSS / STG_EFF).

BTW, You have defined NCAP_BND with the description "Max capacity bound". Note that it defines a bound for the new capacity installed in the period t specified in NCAP_BND(r,t,p,bd). So, your NCAP_BND bounds in the Subres seem to be defined on the new capacity in the Base year only.