the disclosed invention provides examples of preferred embodiments including systems for harvesting energy from variable output energy harvesting apparatus . the systems include energy harvesting apparatus for providing energy input to a switched mode power supply and a control loop for dynamically adjusting energy harvesting apparatus input to the switched mode power supply , whereby system output power is substantially optimized to the practical . exemplary embodiments of the invention include systems for harvesting energy using solar cells in boost , buck , and buck - boost configurations .