  In this paper, we study how datacenter energy cost can be effectively reduced
in the wholesale electricity market via cooperative power procurement.
Intuitively, by aggregating workloads and renewables across a group of
datacenters, the overall power demand uncertainty of datacenters can be
reduced, resulting in less chance of being penalized when participating in the
wholesale electricity market. We use cooperative game theory to model the
cooperative electricity procurement process of datacenters as a cooperative
game, and show the cost saving benefits of aggregation. Then, a cost allocation
scheme based on the marginal contribution of each datacenter to the total
expected cost is proposed to distribute the aggregation benefits among the
participating datacenters. Besides, we propose proportional cost allocation
scheme to distribute the aggregation benefits among the participating
datacenters after realizations of power demand and market prices. Finally,
numerical experiments based on real-world traces are conducted to illustrate
the benefits of aggregation compared to noncooperative power procurement.
