Systems and methods are provided for generating electric power using low grade thermal energy from a vehicle. The methods may include surrounding at least a portion of a coolant conduit system with a flexible thermo-electrochemical cell including a nanoporous cathode electrode, a nanoporous anode electrode, and an electrolyte. A coolant fluid may be circulated through the coolant conduit system, which is in thermal communication with a power generating unit, such as an internal combustion engine or fuel cell stack. The method includes maintaining a temperature gradient in the electrolyte solution by contacting the anode electrode with the coolant conduit system, and exposing the cathode electrode to a temperature lower than a temperature of the coolant conduit system. Generated electrical charges can be collected for subsequent use.