the energy contained in a photon of light is equal to planck's constant times the frequency of the light (e = hf, h = 6.62606957 × 10-34 m x m kg / s), and the shorter the wave length, the higher the frequency. And the number of photons striking you each second is pretty much unimaginable. If we assumed that the light's energy was perfectly transfered to the flames it could be possible (cant really know for sure though :'(). Also we already produce usable energy from sunlight in this world and that is at no-where near 100% efficiency