I bought a couple of new 5' tubes for the kitchen ceiling yesterday. On fitting them I was gobsmacked at the difference in light output. I knew the old ones were a bit down but didn't think they were as much as that. The old ones were 3300K, new ones were 4700K, so that makes a difference anyway, but even so. Bloody hell, it's like full-on daylight in there now and that's with only one tube in each double fitting.
Square root of F-all. Quick google suggests that a 5' tube will be 58W or 65W. That's less than ~140W for both. The vast majority of the OP's energy bill will be for heating. (Centre for Alternative Technology suggests 80%).
People get used to expecting that lamps die at the end of life. After all, that is all too obvious with filament lamps.
However, fluorescent tubes often don't die at end of life, and can continue working for many thousands of hours more in a low efficiency mode with worn out phosphors. I worked in a place where some of the tubes were never switched off, and were still running well over 10 years after installation. This became obvious when the occasional tube did fail and was replaced - light output of the original tubes was probably down to only 1/4 of what it had been.
Same goes for CFLs - you don't have to run them until they go right out - you can (and should) replace them when they've reached end of effective working life and got too dim.
Power consumption doesn't drop when fluorescents dim with age, and if they start going dim purple (argon gas is discharging because there's no mercury left), power consumption can go up (depending on type of control gear).
are.http://en.wikipedia.org/wiki/Colour_temperature#LightingYou think I don't know that?
A 50/50 mix of warm white and cool white is reckoned to be the best, but nothing comes close to HID. Although, there are grow-LEDs available now, but I haven't a clue what the results are.
Not a great application for LEDs in reality, some sites try and pull in NASA research ffrom the early 000`s with growing lettuce in space, the results weren`t that great . iR wound healing different case now getting strangled into IR LED wrinkle therapy.
the measure for lamp efficacy for horticultural use, how do you think you get flowers out of season, is Photosynthetically Active Watts, PAR:
I don't know what happens chemically, but it slowly deteriorates throughout the lamp's life, and that's the reason light output steadily drops. It does absorb some of the lamp's mercury over time. It's also exposed to high levels of UV, and in contact with ionised gases, all of which make for a pretty nasty environment. I don't know which specific ones are responsible for its drop off in efficiency though.
I have wondered if it's recylable, because there's a world shortage of the rare earth metals used in it. I don't know if it can be made to work as good as new again. The lighting industry is expecting a world shortage of fluorescent lamps in a year or two, except those manufactured in China. Currently, China makes most of the CFL retrofits, and most other tubes are manufactured outside China, and it's these which are going to be hit by the shortage of rare earths. (China will have only enough for its own industry, not for export.) A couple of years later, some additional sources of rare earths should start coming online from the US which might alleviate the problem, unless the usage of rare earths for other new inventions continues to increase as it has in the past.
Plants generally don't like UV - it damages their tissues. They get most of their energy from the red area of the spectrum, and a little from the blue in some cases. The growlux or plain warm white work best.
Some plants need other specific wavelengths to trigger flowering or other behaviours.
But generating levels of light produced by the sun is rather expensive in energy, so using the sun in the first place works best.
All plants have to do something to protect themselves from UV. Exactly what this is varies from one plant to another, and from one area of a plant to another area of the same plant. Some of the chemicals they produce to mop up the UV damage are quite beneficial for mopping up similar damage in ourselves, which is one of the reasons eating the parts of green vegetables which are designed to be exposed to the sun is generally a good thing for our health too.
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