Energy storage systems (ESSs) are essential components of the future smart grid to smooth out the fluctuating output of renewable energy generators. However, installing large number of ESSs for individual energy consumers may not be practically implementable, due to both the space limitation and high investment cost. As a result, in this paper, we study the energy management problem of multiple users with renewable energy sources and a single shared ESS. To solve this problem, we propose an algorithm that jointly optimizes the energy charged/discharged to/from the shared ESS given a profit coefficient set that specifies the desired proportion of the total profit allocated to each user, subject to practical constraints of the system. We conduct simulations based on the real data from California, US, and show that the shared ESS can potentially increase the total profit of all users by 10% over the case that users own individual small-scale ESSs with no energy sharing.