  This paper presents an automated peer-to-peer (P2P) negotiation strategy for
settling energy contracts among prosumers in a Residential Energy Cooperative
(REC) considering heterogeneous prosumer preferences. The heterogeneity arises
from prosumers' evaluation of energy contracts through multiple societal and
environmental criteria and the prosumers' private preferences over those
criteria. The prosumers engage in bilateral negotiations with peers to mutually
agree on periodical energy contracts/loans that consist of an energy volume to
be exchanged at that period and the return time of the exchanged energy. The
prosumers keep an ordered preference profile of possible energy contracts by
evaluating the contracts from their own valuations on the entailed criteria,
and iteratively offer the peers contracts until an agreement is formed. A
prosumer embeds the valuations into a utility function that further considers
uncertainties imposed by demand and generation profiles. Empirical evaluation
on real demand, generation and storage profiles illustrates that the proposed
negotiation based strategy is able to increase the system efficiency (measured
by utilitarian social welfare) and fairness (measured by Nash social welfare)
over a baseline strategy and an individual flexibility control strategy. We
thus elicit system benefits from P2P flexibility exchange already with few
agents and without central coordination, providing a simple yet flexible and
effective paradigm that may complement existing markets.
