No resource can get compensated twice for the same service per FERC 2222.
So if the solar is net metered (energy service), it can not be in the wholesale market at the same time for the same energy service that it is being paid for by someone else.
If the ISO defined a different service that the solar could participate in, that did not roll up into energy services, then yes you could try to aggregate that solar resource and bid it for only that service this is not energy.
The last comment is tempered by the fact that to date, there are no defined services that solar can also participate in (based on the latest draft rules from each ISO). That the distribution utility has the right to review and deny participation (with good reason) for any resource attached to their grid, and that states may decide to end Net metering if enough DER participates in 2222 activities.
None of the ISO /RTO documents are really "finished" yet, there are many questions that still need to be detailed in the rules. Expect it to take at least 5 years to iron out the issues with these rules, and that updates will appear regularly from now until likely 2026. Market monitors will find lots of holes/issues/problems that will have to be resolved.
My favorites right now include:
- How to properly define and compensate energy efficiency
- How to deal with baselines for demand response
- Can I wheel an aggregation to another ISO/RTO (e.g. an aggregation from Chicago (PJM) into MISO (right next door)
- Can my 2222 aggregation participate in Capacity auctions?
No set of rules that I have read has good answers to these questions.