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johnr
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Re: "Negawatts" - Preparing for Your New Electric Car

Sat Sep 25, 2010 7:23 pm

Azrich wrote:Skylights

We have six 22 x 44 in skylights on a flat roof. We now have the plastic bubble type which let in a lot of the summer heat. We want to replace them with double-pane low-e glass skylights. We know that Velux makes such a skylight, but you have to build a contraption out of wood so the skylight is slanted so the rain will run off.

Does anyone know of any other manufacturers of glass skylights that might work better on our flat roof?

Sorry I missed your post. Have you considered tubular skylights? They let in all the sunlight with none of the heat, and they're easier to install as well. :)
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garygid
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Re: "Negawatts" - Preparing for Your New Electric Car

Sat Sep 25, 2010 9:46 pm

Existing through-roof skylights, apparently on a flat roof.
Wants to replace plastic domes with low-e glass, right?

Q. How to tip so rain runs off?

But, first consider:
1. Is glass allowed in the skylight?
2. Sealing glass so there are no leaks.
3. Holding the glass down in a strong wind.

Then, consider a frame to tilt the glass slightly. Only a very little is needed for rain.
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indyflick
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Re: "Negawatts" - Preparing for Your New Electric Car

Sun Sep 26, 2010 12:28 pm

Here's an interesting site on Trombe Wall's and Thermal Mass Window System's for passive solar heating. While this system would reduce your consumption of gas considerably, you might only save a couple of kWhs of electricity a day in the winter months because you wouldn't be running your blower as often. Furnace blower motors typically consume ~100 watts for the efficient versions with many consuming several hundred watts.

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johnr
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Re: "Negawatts" - Preparing for Your New Electric Car

Wed Sep 29, 2010 6:13 pm

I did some quick and dirty calculations to find out which is better for the environment in regards to mercury emissions. Incandescent, CFL, or LED.

First of all, we know that the average electricity production in the US is 57% coal. Also, coal power plants emit on average 0.06 milligrams of mercury per kWh. Finally, CFLs contain about 4.5 milligrams of mercury and last about 1000 hours.

Therefore, using 60 watt incandescent bulbs over a period of 1000 hours would emit 2.05 milligrams of mercury.
A 20 watt CFL would emit only 0.68 mg but we have to add the 4.5 mg contained in the bulb, so a total of 5.18 milligrams of mercury over the same time period.
Currently, LED bulbs are roughly the same efficiency as CFLs but contain no mercury, so an LED bulb would emit only 0.68 milligrams.

This is assuming the power source is 57% coal and the remainder of the power mix is mercury-free. This is also assuming the bulbs are disposed of in the landfill (CFLs are supposed to be disposed of in hazardous waste but nobody bothers to do so).

The result: In terms of mercury emissions the LED bulb comes out ahead of the pack with the least mercury emissions by far. LEDs currently seem very expensive until you consider that they last up to 10 times longer than even CFLs. Second is the incandescent, and the CFL is worst. The solution: Upgrade to the latest lighting technology: LEDs 8-)

Sources: http://www.powerscorecard.org/tech_deta ... ource_id=2 & http://www.myledlightingguide.com/Artic ... ticleID=19
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lne937s
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Re: "Negawatts" - Preparing for Your New Electric Car

Wed Sep 29, 2010 8:57 pm

johnr wrote:I did some quick and dirty calculations to find out which is better for the environment in regards to mercury emissions. Incandescent, CFL, or LED.

First of all, we know that the average electricity production in the US is 57% coal. Also, coal power plants emit on average 0.06 milligrams of mercury per kWh. Finally, CFLs contain about 4.5 milligrams of mercury and last about 1000 hours.

Therefore, using 60 watt incandescent bulbs over a period of 1000 hours would emit 2.05 milligrams of mercury.
A 20 watt CFL would emit only 0.68 mg but we have to add the 4.5 mg contained in the bulb, so a total of 5.18 milligrams of mercury over the same time period.
Currently, LED bulbs are roughly the same efficiency as CFLs but contain no mercury, so an LED bulb would emit only 0.68 milligrams.

This is assuming the power source is 57% coal and the remainder of the power mix is mercury-free. This is also assuming the bulbs are disposed of in the landfill (CFLs are supposed to be disposed of in hazardous waste but nobody bothers to do so).

The result: In terms of mercury emissions the LED bulb comes out ahead of the pack with the least mercury emissions by far. LEDs currently seem very expensive until you consider that they last up to 10 times longer than even CFLs. Second is the incandescent, and the CFL is worst. The solution: Upgrade to the latest lighting technology: LEDs 8-)

Sources: http://www.powerscorecard.org/tech_deta ... ource_id=2 & http://www.myledlightingguide.com/Artic ... ticleID=19


From a personal exposure perspective, CFL's are even worse if they break. Reason being is that they vaporize the Mercury in the bulb and send it directly into the room. Whereas the coal plant sends it into the atmosphere where it is diluted, the CFL puts it into a concentrated, contained airspace filled with people. It is like the difference between venting car exhaust into the atmosphere and running it in a sealed garage. Mercury is bioaccumulative (you can't really get rid of it in your system unless you surgically remove it) and it tends to collect in biologically active parts of the body. It especially causes problems with pregnant women and children-- this is dramatically more exposure from broken bulbs than regular carnivorous fish consumption (i.e., tuna). If a CFL bulb should break, be sure to evacuate people from the room, ventilate, and follow cleanup procedures recommended by the EPA:

http://www.epa.gov/cfl/cflcleanup.html

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planet4ever
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Re: "Negawatts" - Preparing for Your New Electric Car

Wed Sep 29, 2010 10:45 pm

johnr wrote:This is assuming the power source is 57% coal and the remainder of the power mix is mercury-free. This is also assuming the bulbs are disposed of in the landfill (CFLs are supposed to be disposed of in hazardous waste but nobody bothers to do so).

But our power source (PG&E) is 1% coal, and I do dispose of CFLs as hazardous waste. (In fact I have an appointment Friday morning to do just that, along with some old paint.) Given those facts I think I'll stick with CFLs for now.
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LEAFfan
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Re: "Negawatts" - Preparing for Your New Electric Car

Thu Sep 30, 2010 12:50 am

johnr wrote:I did some quick and dirty calculations to find out which is better for the environment in regards to mercury emissions. Incandescent, CFL, or LED.

First of all, we know that the average electricity production in the US is 57% coal. Also, coal power plants emit on average 0.06 milligrams of mercury per kWh. Finally, CFLs contain about 4.5 milligrams of mercury and last about 1000 hours.

Therefore, using 60 watt incandescent bulbs over a period of 1000 hours would emit 2.05 milligrams of mercury.
A 20 watt CFL would emit only 0.68 mg but we have to add the 4.5 mg contained in the bulb, so a total of 5.18 milligrams of mercury over the same time period.
Currently, LED bulbs are roughly the same efficiency as CFLs but contain no mercury, so an LED bulb would emit only 0.68 milligrams.

This is assuming the power source is 57% coal and the remainder of the power mix is mercury-free. This is also assuming the bulbs are disposed of in the landfill (CFLs are supposed to be disposed of in hazardous waste but nobody bothers to do so).

The result: In terms of mercury emissions the LED bulb comes out ahead of the pack with the least mercury emissions by far. LEDs currently seem very expensive until you consider that they last up to 10 times longer than even CFLs. Second is the incandescent, and the CFL is worst. The solution: Upgrade to the latest lighting technology: LEDs 8-)

Sources: http://www.powerscorecard.org/tech_deta ... ource_id=2 & http://www.myledlightingguide.com/Artic ... ticleID=19


I have to disagree a little...my CFLs are guaranteed to last 5 years. It will be four years and counting in Dec. There is no way that any LED will last 50 years (your "up to 10 times longer). I did notice your "up to", which can actually mean anywhere from no longer to ten times. It's like those sales, when they say, "up to 75% off", but in reality you may find only a few items at that price, with others anywhere from list price to 5-70% off. ;)

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lne937s
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Re: "Negawatts" - Preparing for Your New Electric Car

Thu Sep 30, 2010 7:36 am

leaffan wrote:
I have to disagree a little...my CFLs are guaranteed to last 5 years. It will be four years and counting in Dec. There is no way that any LED will last 50 years (your "up to 10 times longer). I did notice your "up to", which can actually mean anywhere from no longer to ten times. It's like those sales, when they say, "up to 75% off", but in reality you may find only a few items at that price, with others anywhere from list price to 5-70% off. ;)


It has to do with hours of operation in-fixture rating. For typical residential use, those CFL's will last a few years and are warranteed due to government regulations surrounding EnergyStar rating. In many applications, they will not last that long and the warranty will typically be very difficult for you to cash in on (fill out a form, pay S&H that is as much as a new bulb, etc.) so they count on people never cashing in. And those warranties do not apply to commercial applications. If you use the fixture heavily, you will get 10 times as many hours of operation out of an LED bulb in-fixture- more if you use the bulb in a sealed can, more if it is used outside or there are big termerature swings, and much more if the light is constantly being switched on and off (occupancy sensors). Will the LED bulbs last 50 years? probably not due to corrosion, plastics breaking down, etc. Will they last 50,000+ hours in heavily-used fixture with constant switching on and off- yes.

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Ready2plugin
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Re: "Negawatts" - Preparing for Your New Electric Car

Thu Sep 30, 2010 7:49 am

lne937s wrote:For LED lighting, I recommend CREE. There is a lot of exageration in the LED lighting business, and some products that look good in manufacturer's claims do not perform well in real life or independant testing. CREE products tend to outperform rated specs in independant testing.
http://www.creeledlighting.com/index.aspx

You can acutally buy one of their downlights through home depot:
http://www.homedepot.com/Lighting-Fans- ... ogId=10053


I ordered the CREE downlights from Home Depot to replace the 5 standard dimmable ones I have in my kitchen. It took a total of 20 minutes to do all 5 and my wife loves the look and the brightness of the new lights. $50 a pop is still pretty expensive, but I counld not be happier (other than if they were cheaper :P ) with these.

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drees
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Re: "Negawatts" - Preparing for Your New Electric Car

Thu Sep 30, 2010 12:25 pm

johnr wrote:I did some quick and dirty calculations to find out which is better for the environment in regards to mercury emissions. Incandescent, CFL, or LED.

First of all, we know that the average electricity production in the US is 57% coal. Also, coal power plants emit on average 0.06 milligrams of mercury per kWh. Finally, CFLs contain about 4.5 milligrams of mercury and last about 1000 hours.

Your conclusion is wrong because you have made the wrong assumption about CFL bulb life.

While an incandescent bulb typically lasts about 1000 hours at most, your typical CFL is rated for between 6000-15000 hours.

If you run the numbers for even a 6000 hour run time, the conclusion is very different - especially considering that you can recycle the CFL and avoid all mercury emissions.

If you are worried at all about breakage - do not use a CFL in that location and pay extra for the LED bulb.
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