Vibration energy harvesting holds great potential to achieve long-lifetime autonomous operation of low-power electronic devices. This work is concerned with analytical and numerical modeling and analysis of a unimorph beam and a novel multi-beam energy harvesting systems. Several of the former device and two identical proof masses are utilized to design the multi-beam harvester, aiming to propose a scavenger with resonance frequency of less than 100 Hz. Accuracy of the models are verified, and extensive parametric studies are presented. Results demonstrate that the proposed multi-beam harvester is capable of generating several milliwatts of power under harmonic base acceleration of 0.4 g.