ST-Storage Simultaneous Injection & Withdrawal

[ThanosGkou]

The case of simultaneous injection and withdrawal of st-storage objects (of type "Battery") was observed in a real-life case study. As such, I can't really provide a directly reproducible study, but I can provide some hints that I think are relevant. The below comments are what suspect is happening, but haven't verified it in practice.

I'm using Antares 8.6.6 in Windows 10.

When the phenomenon of simultaneous charge+discharge takes place, it wasn't in my case accompanied by spilled energy. BUT, the marginal price was a bit negative, e.g. -0.08 e/MWh, which means that the system is marginally not spilling energy, because the Cost of Spilled energy was set in my case to 0.1e/MWh.

So, if a 1000 MW battery has 90% efficiency, a simultaneous charge+discharge would provide "free" dissipation of 100MW. These 100MW, if they were to be spilled, they would be charged at a cost of 0.1e/MWh. So, from an optimization point of view it makes sense to take advantage of this efffect, but in my opinion there should be a constraint to forbid this behaviour.