An apparatus includes a thermoelectric (TE) device, a gas flow conduit proximate to one side of the thermoelectric device, a plurality of flexible tubes proximate to a second side of the thermoelectric device, and a spring to control contact force between the flexible tubes and the thermoelectric device. The spring comprises a coil spring at least partially circumscribing the gas flow conduit. The thermoelectric device converts a temperature differential between the flexible tubes and the gas flow conduit into electrical energy.