Modelling question of the rate of decline in CO2 emissions

[zhangshu]

Hello, I am a beginner of TIMES. I am modeling China's energy system. There are some questions about the setting of user constraints.

I want to realize the constraint of gradually accelerating the rate of carbon dioxide decline, that is, the emission reduction in 2030-2035 is greater than that in 2025-2030. In the document of TIMES, I only saw the modeling of T and T-1, so to depict the rate of carbon dioxide decline, at least T, T-1 and T-2 phases are needed.How do you model a problem like this?

Thank you very much

[Antti-L]

Yes, the period-dynamic constraints are for successive periods, but by using the "cumulative" type I think it is reasonably easy.

So, denoting by Emiss(t) the emissions in period t, I guess your constraint would be something like:

   Emiss(2030)−Emiss(2035) ≥ AD × (Emiss(2025)−Emiss(2030)) , where AD > 1.

As this is linear constraint, it can be defined in TIMES.  Just define the UC_COMNET coefficients as above, for the emission commodity(s):

  UC_COMNET(2025) = −AD
  UC_COMNET(2030) = 1+AD
  UC_COMNET(2035) = −1
  UC_COMNET(0) = −1  (no interpolation/extrapolation)

And then define the UC_RHSR('LO')=0 (if the constraint is for single region or by region) or UC_RHS('LO')=0 (if the constraint is for sum over regions).

The minor drawback here is that the constraint is not independent of the period definition, and so it would need to be revised/removed if the periods are changed in such a way that any of the years 2025, 2030 and 2035 is not included as a milestone.

[Antti-L]

There is also another approach, based on using the UC_UCN parameter.  You could define the difference in emissions between T and T−1 into a VAR_UCRT variable, by using a dynamic constraint of type (T,T−1).  Then you could refer to this variable in a second dynamic constraint of type (T,T+1), by using UC_UCN, and define the minimum acceleration of emission reduction in proportion to that.

This approach has the benefit of being independent of the period definition, and it can also be easier if one should define it for several triplets (T+1, T, T−1).  However, as yet I have not tested this approach myself.

[zhangshu]

There is also another approach, based on using the UC_UCN parameter.  You could define the difference in emissions between T and T−1 into a VAR_UCRT variable, by using a dynamic constraint of type (T,T−1).  Then you could refer to this variable in a second dynamic constraint of type (T,T+1), by using UC_UCN, and define the minimum acceleration of emission reduction in proportion to that.

This approach has the benefit of being independent of the period definition, and it can also be easier if one should define it for several triplets (T+1, T, T−1).  However, as yet I have not tested this approach myself.

• Thank you very much for your reply. The first method is really effective. I will test the second method later, thanks again for your help!