A broad band energy harvesting system to harvest energy from a structure and associated methods are provided. The system includes a structure carrying a plurality of environmentally produced vibration frequencies extending over a frequency range and an energy harvesting apparatus positioned in vibration receiving communication with the structure to harvest energy from the structure. Each energy harvesting apparatus includes broadly tuned energy harvesting generators having relatively low quality factor and corresponding relatively wide bandwidth. The energy harvesting generators collectively provide energy harvesting over multiple modes to thereby provide energy harvesting over a substantial portion of the frequency range. Each energy harvesting generator can include a cantilevered beam connected to a common backbone comprised of a resilient material configured to transfer energy between adjacent generators to further enhance energy harvesting.