Every resistor is a source of a thermal noise with frequencies reaching up to THz. The noise available power is given by bandwidth, but independent of the frequency in which the noise is generated. To harness the noise power, some nonlinearity in the system should be present. With modern semiconductors, such as Schottky diodes or CMOS rectifiers, contemporary employed in RFID devices, the GHz part of the noise frequency range may be used. By means of RLC resonant circuits or PCB resonators connected in a cascade, a sufficient noise voltage can be attained. After rectifying, the noise energy may be stored in a condenser as a charge. Noise energy in a resonant circuit can be considered as that of a one sole molecule in an ideal gas. Even if the noise available power in a resonant circuit is negligibly small, the energy can be greatly increased by letting the power integrate over a long-time interval. In the appendix, a numerical example is presented. Keywords: Thermal noise harnessing, RLC resonant circuits, small signal Schottky diode, RF-harvesting, CMOS multistage rectifiers, PCB resonators, RFID devices, Second law.