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Doubt about output value
#1
Hi Everyone,

I am studying how storage models behave in VEDA-TIMES and their parameters on it. 

Right now, I am modeling the following process:

STG - DAYNITE
Capacity = 4.39 GW
STG_EFF = 0.72
Cap2Act = 31.536 GW/PJ
AFC(ACT) = AFC(NRG) = AFC(ELC) = 1.0
IN COMM = OUT COMM = ELC (Electricity)

For example, for winter timeslice we have the following YRFR:

YRFR = 0.01027397 >>> Equivalent aproxx. to 3.75 days
So for the max out or in flow I expected it to be around = (4.39 * 31.536 * YRFR) = 1.42147 PJ

In all timeslices, the limits are respected, everything works as I expected. However, my questions is that when I sum the IN and OUT flows the results is equal to the max out/in value at this timeslice. I am curious to know why this happens, anyone has any idea ? Does TIMES divides that capacity we have for in and out flow when they occur at the same timeslice ? This has brought me a lot of questions ... 

Thank you guys.


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#2
You are defining NCAP_AFC availability factors for both ELC and NRG flows of the storage. This means that both the ELC output and the NRG inputs will be included in the flow-capacity equations defining the capacity availability.

This is in many cases exactly as desired, because simultaneous charging and discharging is usually not considered typical storage operation, and should in fact be avoided, because such simultaneous flows would basically not require any storage activity (storage level), and would thus not correspond to any genuine storage operation. The combined flow-capacity equations restrict such unusual storage operation, although do not fully prohibit it.

However, for some storage technologies it may be desirable to allow also for simultaneous charging and discharging, and in such cases you may want to consider either 1) leaving the charging flows out of the availability constraint (if bounding the charging by the capacity may be considered unimportant), or 2) defining the availability constraints independently for the output and input flow(s).  The option 1) is self-explanatory.  The independent option 2) can be enabled by defining NCAP_AFC(r,'0',p,ACT,TSL)= -1; where TSL is the timeslice level, for which you want to have the independent constraints. However, that requires the input / output commodities to be different (always possible by using an aux flow if necessary).
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#3
(05-10-2021, 06:11 PM)Antti-L Wrote: You are defining NCAP_AFC availability factors for both ELC and NRG flows of the storage. This means that both the ELC output and the NRG inputs will be included in the flow-capacity equations defining the capacity availability.

This is in many cases exactly as desired, because simultaneous charging and discharging is usually not considered typical storage operation, and should in fact be avoided, because such simultaneous flows would basically not require any storage activity (storage level), and would thus not correspond to any genuine storage operation. The combined flow-capacity equations restrict such unusual storage operation, although do not fully prohibit it.

However, for some storage technologies it may be desirable to allow also for simultaneous charging and discharging, and in such cases you may want to consider either 1) leaving the charging flows out of the availability constraint (if bounding the charging by the capacity may be considered unimportant), or 2) defining the availability constraints independently for the output and input flow(s).  The option 1) is  self-explanatory.  The independent option 2) can be enabled by defining NCAP_AFC(r,'0',p,ACT,TSL)= -1; where TSL is the timeslice level, for which you want to have the independent constraints. However, that requires the input / output commodities to be different (always possible by using an aux flow if necessary).

Now I got it! Thank you very much Antii for your explation!!
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