How are energy storages that provide ancillary services handled?

Bids for energy storage are submitted either as production or as consumption.  

More information on handling when supplying from energy storage can be found in Section 2.1.3 of the Balance Responsibility Agreement (Agreement 4620) Appendix 2, “General Terms and Conditions for Balance Responsible Parties”, which you can find on the page on Balance Responsibility Agreement (in Swedish).