Litroenergy is a new type of material that will emit light for a half-life of 12 years without needing electricity or sun exposure. The self-luminous micro-particles are called Litrospheres and are said to be non-toxic and inexpensive (although one would assume they are radioactive…). The light is said to be equivalent to a 20 watt incandescent bulb, and would cost a mere 35 cents. Perfect for any bunker!