overproduction

[dvanre]

I have a material commodity which is overproduced though declared as FX. As I have a UC constrained on the commodity, var_comprd and var_comnet are generated, maybe it is due to that; How can I limit it (I have a cost already on var_comnet which I could increase, but can it not been done in another way 

[Antti-L]

Ok, this situation may need to be addressed in the code. For now, you can define COM_BNDNET(FX) with the interpolation option 2, and that will prevent the VAR_COMNET from being non-zero.

However, I would be interested to know why this happens. Therefore, can you describe the UC constraint you have on the commodity so that I can see why the VAR_COMNET is getting activated.  I will then try and prevent that from occurring in the next version of TIMES.

But note that the VAR_COMNET variables are, indeed, activated if you use COM_CSTNET on the commodity, even when the commodity type is FX. This is by design, since the original days of TIMES. If that is the reason for your problem, you could simply remove the cost on VAR_COMNET (the cost would be zero anyway if VAR_COMNET is bound to zero).

Thanks,
Antti

[dvanre]

My problem occurs with MPPPUP which is overproduced to get black liquor with severe CO2 constraints. The MPPUP production is constrained by the user constraint in the attach file UC_IND, sheet UC_PUP which impose a lower bound on the CHEM production technology. There is also a COM_TAXNET on MPPUP in the scenario BAUGENERAL(sheet renaccounting). What I also find strange is that when I eliminate all COMTAX_NET on MAT, there is no overproduction of MPPUP but when I put only the COM_TAXNET on MPPPUP =0, then there is overproduction

[dvanre]

uploads/31/Scen_BAUGeneral.rar

[Antti-L]

Thanks for the info.  It seems that the reason for the overproduction is simply the tax on MPPPUP, which activates the VAR_COMNET variable. This is by design (it has been this way from the early days of TIMES). Putting a tax on the NET production of a commodity would be meaningless if the NET production would be bound to zero. Therefore, TIMES has been designed to activate the VAR_COMNET variables whenever a cost or tax is specified on the NET production, because otherwise the cost/tax would be always zero, which would not make sense.

So, the easy solution to your problem is to remove the tax from the MPPPUP commodity. You mentioned yourself that if you eliminate all COM_TAXNET on MAT, there is no overproduction of MPPUP. I find it strange that you have defined those COM_TAXNET on the MAT commodities but also want to the keep the NET production at zero, because the TAX proceeds would then always be zero.

[dvanre]

Thanks; The MAT are LO by default I think and so the COMTAXNET should avoid overproduction. I put it on FX not to have overproduction, So this FX is overwritten when comtaxnet is given, if I understand correctly. It seems that COMTAXNET=0 is not equivalent to no comtaxnet, is this correct

[Antti-L]

The LIM type of MAT commodities is FX by default.  For energy and environmental commodities (NRG, ENV) the default is LO.

When COM_TAXNET is specified, the FX type is actually not overwritten, but the VAR_COMNET variables are activated. However, you are correct that mathematically the end result may be considered equivalent to overwriting the FX type by LO.

Yes, COM_TAXNET=0 is different from "no COM_TAXNET", because the explicitly specified zero value is seen as EPS by the model generator, and it indicates that the user wants to have the VAR_COMNET variables activated.