| the film in the article says: "a 100 W light bulb turned on every night for a year takes equivalent energy output from burning half a ton of coal" I get that this film is probably dated, but there are so many things wrong with this: 1. 100 W for 8 hours at night * 365 days in a year is 292 kWh; a ton of coal burned in a power plant produces ~1,000 kWh. so, much less than half a ton. still alot though... 2. modern 100 W light bulbs typically use LED and only require ~14 W of power (so ~14% of the power draw) 3. neither of the above actually matter though because power at night is essentially free; wind turbines, hydro, geo thermal, etc. all continue to work at night and can't be easily shut off, even though demand for power is much much lower. given that energy waste is not an issue, the benefits of solving this problem are restricted to being able to view stars, preventing a few birds from running into buildings, and requiring residents near outdoor lighting to install curtains (though it seems like even with lights that are dimmed and pointing downwards, most people that live near them would still install curtains anyways, whether for darkness or just privacy...). This must be weighed with the benefits of having lights on in the first place. |
You are limiting yourself to residential light bulbs, which previously typically came in "100W" (actually 1,600 lumen) and "60W" (actually 800 lumen) varieties. Yes, the modern indoor 1600 and 800 lumen bulbs now use less power.
But if you look up street lights, you'll find HPS/Halide can use 100-400W, while modern LED use 50-150W. Also architectural lamps that wash against the side of a building may have different outputs.
Given the hundreds/thousands of street lights out there, if (say) half the light is going up (or even sideways) that's a lot of waste: we could all the photons that are going up/out could be redirect down then we could reduce the power needed even further.
> 3. neither of the above actually matter though because power at night is essentially free; wind turbines, hydro, geo thermal, etc. all continue to work at night and can't be easily shut off, even though demand for power is much much lower.
And what does this light do to people's (and animals') circadian rhythms? What does the excess glare of street lights do to road users (like drivers), especially after it has rained? What have we lost 'culturally' by not being able to see the stars?