  An energy cooperation policy for energy harvesting wireless sensor networks
(WSNs) with wireless power transfer is proposed in this paper to balance the
energy at each sensor node and increase the total energy utilization ratio of
the whole WSNs. Considering the unbalanced spatio-temporal properties of the
energy supply across the deployment terrain of energy harvesting WSNs and the
dynamic traffic load at each sensor node, the energy cooperation problem among
sensor nodes is decomposed into two steps: the local energy storage at each
sensor node based on its traffic load to meet its own needs; within the energy
storage procedure sensor nodes with excess energy transmit a part of their
energy to nodes with energy shortage through the energy trading. Inventory
theory and game theory are respectively applied to solving the local energy
storage problem at each sensor node and the energy trading problem among
multiple sensor nodes. Numerical results show that compared with the static
energy cooperation method without energy trading, the Stackelberg Model based
Game we design in this paper can significantly improve the trading volume of
energy thereby increasing the utilization ratio of the harvested energy which
is unevenly distributed in the WSNs.
