  We address potential synergy among flexible demands and how they may earn
more collectively than individually by forming a coalition and bidding to the
reserve market. We consider frequency-supporting ancillary service markets,
particularly the manual Frequency Restoration Reserve (mFRR) market. The
coalition of flexible demands provides more reliable mFRR services, where in
comparison to individual demands, is penalized less for their potential failure
and is paid more for their successful activation. This synergy effect is
quantified as a function of the number of homogeneous assets in the coalition.
A subsequent payment allocation mechanism using Shapley values is proposed to
distribute the total earnings of the coalition among demands, while
incentivizing them to remain in the coalition. For our numerical study, we use
real price data from the Danish mFRR market in 2022.
