Recent research shows that significant energy saving can be achieved in wireless sensor networks by using mo- bile elements (MEs) capable of carrying data mechanically. However, the low movement speed of MEs hinders their use in data-intensive sensing applications with temporal con- straints. To address this issue, we propose a rendezvous- based approach in which a subset of nodes serve as the rendezvous points (RPs) that buffer data originated from sources and transfer to MEs when they arrive. RPs enable MEs to collect a large volume of data at a time without trav- eling long distances, which can achieve a desirable balance between network energy saving and data collection delay. We develop two rendezvous planning algorithms, RP-CP and RP-UG. RP-CP finds the optimal RPs when MEs move along the data routing tree while RP-UG greedily chooses the RPs with maximum energy saving to travel distance ra- tios. We design the Rendezvous-based Data Collection pro- tocol that facilitates reliable data transfers from RPs to MEs in presence of significant unexpected delays in ME move- ment and network communication. Our approach is vali- dated through extensive simulations.