Science Forums 2

[CraigD]

Originally Posted by Michaelangelica

Does anyone know if the production of the [compact florescent?] lamps costs more in CO2 than they save?

Not even close, I calculate.

The most difficult stuff to melt (and thus form) in a compact florescent is the glass, at about 1000° C. My eyeball guesstimate of the mass of one (I’m looking at a 14 W “ultra mini spiral lamp”, the last in a 6 pack) is about 100 g. The specific heat of typical glass is about 0.67 J/g/K, so an efficient furnace should require about 1000 K * 100 g * .67 J/g/K = 67000 J to make one of these lamps. It draws 14 W, so uses as much energy as it took to manufacture it in 67000 J / 14 W = about 4800 s = about 80 minutes. The bulb has a rated life of 10,000 hrs, so the total energy it will use making light over its lifetime is 10000 hr * 3600 s/hr * 14 W = 500,000,000 J, so it takes about 0.02% the energy to make as it uses over its lifetime making light.

It replaces a 60 W incandescent bulb, which takes about the same energy to make as the florescent. It has a rated life of 1,500 hrs. I’ll need about 6.7 of these to last the 10,000 hrs of the compact florescent. They’ll use 10000 hr *3600 s/hr *60 W = 2,160,000,000 J.

So, with the energy saved by a single compact florescent we could make (2160000000 J – 500000000 J)/67000 J = nearly 25,000 compact florescents over a roughly 7 year period

According to several references I googled, power generation in the US releases between 0.0001 and 0.0002 g/J of generated energy, so powering a compact florescent bulb over its 7 year life releases about 500000000 J * 0.0001 g/J = 5 kg, far more than manufacturing it would release even if it were made of pure carbon and half burned in making each lamp

My local electricity authority is giving away six for free. (Unfortunately most of my light fittings are recessed and I don't think you can use them in recessed fittings.).

I use them in recessed fixtures. The little spiral lights are about 75% as long and 60% wide as the bulb they replace, and produce less heat, so there’s no problem.

After some complaints that the lighting in areas of my basement was too “flat” and white, I added some thin plastic “gells” to give them color. The florescents are so cool, I don’t need to worry about melting the plastic.

I’ve only noted 2 drawbacks with replacing incandescent with compact fluorescents

• In fixtures in which the bulb is visible, they look funny
• They take as long as 10 seconds to produce maximum light, so some places, such as near stair in dark areas that you enter with your eyes adjusted to bright daylight, you may have to pause for them to be bright enough for you to see well

How much power do you save by not leaving TVs on stand by mode?

According to this very nice c/net article, it varies a lot from model to model, from just a few W, to nearly 20.

These questions and articles point out that most people trying to save energy are hampered by the lack of published practical power consumption ratings (the ones usually published are maximums, and of little comparison value), and convenient devices to measure household electric current. A simple gadget you could take to a store and measure the power of consumer electonics before you buy them would be great for the conservation-focused consumer, but I’ve never seen one. Just having a easily viewed power meter for your home, so you could experiment with switching devices on and off and observing your total home power, would be very handy, but I’ve never seen one that wasn’t expensive, hard to install, and intended for commercial use. When I do such measuring, I have to go outside and time the revolutions on my power company electric meter using a stopwatch, an inconvenient, low-tech, but accurate and effective technique.

Thanks for the tip re iron and phytoplankton. That is a pretty impressive experiment. Why Iron? What does it do?

I don’t know the details, only that iron is important to their metabolism, and theories suggest that they rarely get as much as they need for maximum metabolism. It’s a complicated and controversial subject.