Questions on Var_NCap, Var_NCapM, INSTCAP, LUMPINV

[atujaycee]

Please I have some questions.
 
I run the demo files C:\VEDA\VEDA_Models\ETSAP_DemoS_Adv\ETSAP_DemoS_Adv\DemoS_Adv
A small part of the results is attached.
I note that New capacity Var_NCap as determined by the model is different from Capacity (time) – Capacity (previous time) which I calculated (from the Var_Cap results), but in some cases, they are the same.
E.g. in the attached, for the technology COTNCOA1 the first two entries of my calculations (173.791, 231.5573) from Var_Cap correspond to Var_NCap, but the others are significantly different.
Please why iis this so? Does it have to do with retired capacity? If so, how? What is the equation connecting all capacity-related variables. I cannot see Var_RCap under the ATTRIBUTES tab.
 
Also, please what is the physical meaning of Var_NCapM? Under the attributes tab, I saw Cap_New. Then, this was divided into INSTCAP and LUMPINV. Please what are these? I checked all your documentations but I can’t find these there. Any material to recommend?
 
Best regards, James.

[Antti-L]

For a description of the Cap_New attribute, see:
Part II Section 3.3  Report parameters
Part V Appendix A: VEDA-BE TIMES Attributes

Yes, Var_Cap(t) – Var_Cap(t–1) cannot in general be equal to Var_Ncap(t), because of the phase-out of old capacity at the end of their life.

As you can see from the documentation, there is no physical meaning of Var_NCapM.
As to the equation connecting all capacity-related variables, see EQ(l)_CPT.

[atujaycee]

For a description of the Cap_New attribute, see:
Part II Section 3.3  Report parameters
Part V Appendix A: VEDA-BE TIMES Attributes

Yes, Var_Cap(t) – Var_Cap(t–1)  cannot in general be equal to Var_Ncap(t), because of the phase-out of old capacity at the end of their life.

As you can see from the documentation, there is no physical meaning of Var_NCapM.
As to the equation connecting all capacity-related variables, see EQ(l)_CPT.

OK. Thanks, but I am not clear on some issues.
Var_NCapM is called "Technology Investment-Marginals", so it has a meaning, but what is the meaning of marginal here? How does Var_NCapM differ from Var_NCap?

Also, please where can one find EQ(l)_CPT? I find many TIMES Constraints in Part II documentation, Section 6.3, but where can one find these constraints in your software? Can we access the TIMES equations? If so, where? How? In VEDA or GAMS or Excel or other?

Best regards, James.

[Antti-L]

As written in the documentation (slightly edited for improved readability):

VAR_NcapM:
Undiscounted reduced costs of investment variable (VAR_NCAP) of process (p); only reported, when the
capacity variable is at its lower or upper bound;
When the investment variable is at its lower (upper) bound, the reduced costs describe the cost increase (decrease) of the objective function caused by an increase of the lower (upper) bound by one unit; the undiscounted reduced costs can be interpreted as the necessary decrease / increase in the investment cost coefficient, such that the investment variable will leave its lower (upper) bound.

The marginals reported are thus these "Undiscounted reduced costs", explained above.

Concerning your question: "How does Var_NCapM differ from Var_NCap?" You can find the answer by comparing it to the description of Var_Ncap:  Technology Investment – New capacity: Level value of investment variable (VAR_NCAP) of process (p) in period (v).

Var_Ncap is thus completely different from Var_NCapM: Var_Ncap gives the level of the variable, instead of the marginal cost impact of a unit change in that variable.

where can one find EQ(l)_CPT

You can find the documentation for it in Part II (6.3.18  Equation: EQ(l)_CPT). You can find the GAMS implementation for it in the GAMS code, file EQCPT.mod.