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How can I model discharge times for two DAYNITE processes?
#1
Hello,

Apologies for a previous post that was poorly phrased. I'm trying to incorporate a notion of hourly discharge times for two DAYNITE storage processes using availability factors, as my model has DAYNITE level timeslices and I don't want to go to an hourly time resolution. One process is representative of lithium ion batteries that should discharge their whole capacity in 4h , the other is representative of longer term storage (but still DAYNITE, not seasonal or annual) that can discharge its capacity continuously for 24h. I would like to model the availability factor(not in the TIMES storage sense, but in the normal sense) of the Li-ion battery as 4h/24h for every time slice, and that of the longer term process as 24/24 (1), and let TIMES/VEDA decide when to charge, discharge each process.

However, AF/AFS would just restrict the stored energy and AFC/AFCS are for bounding the input/output flow... which I understand (misunderstand?) as the amount of storage capacity the process is allowed to charge (for the input commodity) or discharge i.e. for some storage with input ELC and output OPELC, NCAP_AFCS(ELC)=0.5 means the storage process can only charge up to 50% of the storage capacity, and NCAP_AFCS(OPELC)=0.5 means the process can discharge just 50% of its capacity in a given timeslice.

So, assuming that AF/AFS and NCAP_AFC/AFCS aren't appropriate for incorporating the sort of availability factor mentioned in paragraph one, are there other TIMES parameters that I could use to basically inform the model that the storage with longer discharge times is better than Lithium ion storage? Could you please suggest a way to implement such an availability factor for storage?

Thanks.
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#2
(24-04-2020, 12:08 AM)ach Wrote: for some storage with input ELC and output OPELC, NCAP_AFCS(ELC)=0.5 means the storage process can only charge up to 50% of the storage capacity, and NCAP_AFCS(OPELC)=0.5 means the process can discharge just 50% of its capacity in a given timeslice.

If you mean by storage capacity the energy capacity, no, that is not at all true.

It is explained in the documentation:
In TIMES, capacity by default bounds only the activity. For storage, this means the amount of stored energy. However, with the NCAP_AFC/NCAP_AFCS attributes, one can bound the output (or input) flows instead. Capacity then also refers to the nominal output (or input) capacity, e.g. electrical capacity of a pumped hydro power plant.

Consequently, if you have a storage with input ELC and output OPELC, and a capacity of 1 MW, and you define for this storage NCAP_AFCS(ELC,s)=0.5, it means the storage process can charge only at most at the (average) input power level of 0.5 MW within timeslice s, irrespective of the storage energy capacity.  Similarly, NCAP_AFCS(OPELC,s)=0.5 means the storage process can discharge only at most at the (average) output power level of 0.5 MW within timeslice s.  

And then, you can additionally define the capacity for the stored energy, by defining additional availability factors NCAP_AFC(ACT,tslvl) for the storage level in proportion to the storage capacity (max. amount of energy stored), as explained in the documentation. So, you can define the input capacity, the output capacity, and the energy storage capacity, availability factors for each of these, and also at any desired timeslice level (DAYNITE, WEEKLY, SEASON, ANNUAL). Thus, both availability and utilization factors can equally well be defined.

I think these are all pretty much the normal sense of availability and utilization factors. While you claimed otherwise, you didn't actually define your normal sense. Maybe you could write down and post here the the mathematics of your desired "normal sense" equations, so that the Forum readers would be able to compare your equations with those in the documentation?
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#3
Thank you for clarifying that.

So for a storage process STORAGE with output OPELC, if I set NCAP_AFS(p=STORAGE, bd=UP,s)=0.167, does that mean all the stored energy is available for discharge as OPELC for a maximum of 16.7% of the time within the timeslice s? Like a nuclear power plant is operational 90-95% of the time? Because that's what I meant, and that's what I am trying to model .
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#4
Please express mathematically, what you mean by "all the stored energy is available for discharge as OPELC for a maximum of 16.7% of the time within the timeslice s? "  I am sorry, but at least I don't understand how that natural language description should be translated into a mathematical equation, unless you can clarify that.

Please refer to the relevant variables of the process when you write the equation, e.g. VAR_NCAP(r,v,p), VAR_CAP(r,t,p), VAR_ACT(r,v,t,p,s), VAR_SIN(r,v,t,p,c,s), VAR_SOUT(r,v,t,p,c,s).

For a nuclear power plant, NCAP_AFS(r,y,p,s,UP)=0.9 would mean that the (average) power level of the output within timeslice s is at most 90% of the full capacity, which can be considered equivalent to the process being operational 90% of the time.
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