NOVELTY - A method for spontaneously combusting a fuel, involves contacting several nanocatalyst particles with a fuel and oxygen, at ambient conditions, during which the fuel and oxygen combust spontaneously. The combustion takes place in the absence of flame. The nanocatalyst particles have an average diameter of less than 500 nm. The nanocatalyst particles are preferably entrained in reactant gases, and are provided on a support.    USE - In a thermoelectric generator (claimed); useful for producing electric power in devices such as computer and small electrical appliances; and useful in a reactor system and in a solid-state thermoelectric heater/cooler.    ADVANTAGE - The method provides stable and reproducible spontaneous self-ignition and self-supporting combustion at room temperature, by exposing nanometer-sized catalytic particles to the favorable mixture of fuel and oxygen, without requiring any external ignition or stimuli for initiating combustion. The catalytic activity can be dramatically improved by reducing particle size and changing particle morphology. Nanometer-catalyst supported self-ignition requires no external energy (e.g. heat, flame or high pressure) to start fuel oxidation or combustion process. In the resultant thermometric generator, a high temperature is achieved with flameless nano-combustion, a fast start-up time and short shut-down time are possible, and there is no need for initiation of the catalytic reaction by applying external stimuli such as temperature, pressure, vibration or spark. The lack of moving parts in the generator, reduces friction losses and improves efficiency, lowers maintenance costs and increases product life. In addition, the generator can be scaled from low power to high power applications, and particularly in low power applications, the generator can be implanted in other devices or can be portable. The generator can be based on alcohol, providing very little pollution from operation of the generator, thus allowing the generator to be used indoors.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for thermoelectric generator comprising a heat source containing several nanocatalyst particles, and an inlet for fuel and oxygen for contacting the fuel and oxygen with the nanocatalyst particles; a heat sink; and a thermoelectric generating unit consisting of n- and p-type semiconductors between and in thermal contact with the heat source and heat sink, and an electrical connection between the n- and p-type semiconductors.