EQ_STSBAL Equation

[Sebastien]

Dear all,

I am trying to set up storage processes that store energy both at a seasonal and inter-annual level.

I cannot work out the role of the EQ_STSBAL equation, which appears in my .LST file as follows:

ES_STSBAL(AND,2012,2012,EHYDSTG105,ANNUAL,2012,1).. 
-
VAS_SIN(AND,2012,2012,EHYDSTG105,ELCHYD1,ANNUAL,1)
+
VAS_SOUT(AND,2012,2012,EHYDSTG105,ACT,ANNUAL,1)
+
VAS_SOUT(AND,2012,2012,EHYDSTG105,ELCHYD1,ANNUAL,1) =E= 0 ; (LHS = 0)



From what I understand, this equation links together
- the STGTSS equation that uses VAS_SOUT(AND,2012,2012,EHYDSTG105,ACT,ANNUAL,1))
- and the STGIPS equation that uses VAS_SOUT(AND,2012,2012,EHYDSTG105,ELCHYD1,ANNUAL,1)

However I cannot understand why the two VAR_SOut have the same sign, and I'm not quite clear about VAR_SIn... Is this normal, or did I make a huge mistake in my modeling?

Could someone help me out here? I also attach a SubRES file from my DEMO model, in case it helps... (I used the exact same syntax)
uploads/119/SubRES_B-NewTechs.zip

Many thanks!

Regards,

Sebastien

[Antti-L]

Arranging
the terms, one can immediately see that

   VAS_SOUT(AND,2012,2012,EHYDSTG105,ACT,ANNUAL,1)

is equal
to the net charging to the inter-period storage:

   VAS_SIN(AND,2012,2012,EHYDSTG105,ELCHYD1,ANNUAL,1) –
VAS_SOUT(AND,2012,2012,EHYDSTG105,ELCHYD1,ANNUAL,1)

Because
this is general timeslice storage combined with an IPS storage, this net
charging into the IPS will not come directly from the commodity balance, but it
must come from the TSS storage. The storage flows are linked to the commodity
balance only on the process timeslice level.

Accordingly,
the net charging

   VAS_SOUT(AND,2012,2012,EHYDSTG105,ACT,ANNUAL,1)

is
extracted from the TSS storage at the next finer timeslice level. As you noted,
the same flow appears in EQ_STGTSS for each timeslice s, where

 
VAS_SOUT(AND,2012,2012,EHYDSTG105,ACT,ANNUAL,1) * RS_FR(r,s,ANNUAL)

is a
discharge flow, multilpied by the fraction of timeslice s in proportion to
ANNUAL.

Hence,
in total, the TSS storage is required to provide exactly the amount that is charged
into the IPS storage. For the TSS, this can happen without storage losses if
the TSS storage is charged at timeslice S by the required amount, or with
storage losses (if defined) when taken from the TSS storage stock.

In
summary, the equation just establishes the energy balance between the TSS and
the IPS, and it should be considered quite "normal", unless of course
you can demonstrate that it is not working in an expected way?

Note
also that VAS_SOUT(AND,2012,2012,EHYDSTG105,ACT,ANNUAL,1) is defined as a free
variable (-INF,INF), to accommodate any net amount of transfer between the TSS
and the IPS.

[Sebastien]

Dear Antti,

Thank you for your quick and helpful answer. I was
mainly confused by the sign difference between the two VAR_SOUT
variables, yet it is crystal clear now. (and my processes behave
correctly as far as I can see, I just wanted to make sure I did not
misinterpret VEDABE outputs.)

Thanks and regards,

Sebastien