How can electrons in a tungsten filament release infrared light photons?
I do not believe the active users of Physics SE are patient enough to write or read explanations that can be understood by most of us - the practical electricians. I write an answer here.
Elementary concepts such as &quot;radiation is emitted when electron returns to lower energy orbit&quot; unfortunately explain too loosely what happens in solid materials.
At first solid conductive material doesn't have some sparse allowed electron orbits. When interatom distance is small enough atoms disturb electrons in other atoms, the number of allowed orbits is vastly increased. A part of electrons move in so complex orbits and long distances that they are practically free in the emptiness between the atoms when compared to electrons in tighter lower energy orbits.
Atoms attract indirectly also each other when many atoms attract the same electron. This keeps the material solid - the distribution of the electrons between atoms happens to be a total energy minimum.
The number and variety of the possible electron orbits is so huge that only statistical distribution calculations are possible.
So, what makes electrons to jump from lowest energy orbits to the numerous free upper energy orbits which are possible in solid materials? Thermal excitation, they say. What's that? It's the mechanical thermal motion they say - random vibrations which cause thumps also to electrons.
But there's no such thing as mechanical thump. Electron can change it's course to higher energy orbit ONLY by absorbing a photon and to a lower energy orbit by emitting a photon. When do these things happen depends on are free orbits available, is there radiation available to be absorbed and the life statistics. Electron stay in certain orbit a random time which cannot be determined. Only statistical analyses are possible. That's one basic facts of the quantum physics.
Atoms can vibrate around their equilibrium positions - that's what the heat is. But all inter-atom thumps are  relayed by the common electrons. Together with the previous paragraph that means the material is full of radiation - photons. Physicists handle photons as gas which obeys certain statistics. It's not the same statistics as particles obey because photons born and vanish all the time due the state transitions of the electrons. But their statistical nature is theoretically derived and it explains at least one phenomenon very well: All the time some photons escape out of the surfacea of solid materials. Those photons you already know. It's the thermal radiation, mostly at infrared wavelength range in temperatures that we humans can stand, but also visible light if we warm up materials at least several hundred degrees above our room temperature.
Electric current is a way to generate heat. That's because moving electrons contain extra energy. Besides it they are part of the electron cloud in the solid and obey its statistics so they emit photons and finally cause thumps to atoms. Due that energy loss the drifting motion of the electric current electrons in solids is very slow, only in vacuum electrons can get cosmic average speeds. But the number of drifting able electrons is especially in metals so high that substantial currents are possible.