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Author Topic: Is energy really saved with energy efficient light bulbs?  (Read 5897 times)

Offline PAG

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I fully support all moves for decreased usage of energy.

BUT, I do wonder about energy efficient light bulbs.  I rushed out like so many people and installed them but am thinking that industry may once again have sold us something that doesn't do what we want.

Firstly, and not most importantly, what is the total lifecycle cost in energy of these bulbs compared with incandescent bulbs?  I am fairly certain that considerably more energy goes into their production than a traditional bulb.  Also what is the true life of these bulbs because it is not what is advertised.  I don't have strict records but I know that they do not last 5 years.

Secondly, undoubtedly they consume less energy for the same light emitted.  But with a traditional bulb where does the excess energy go?  The answer is that it is output as heat.  When do you have the lights on?  Mostly when it is dark which is also when it is usually cold (in the UK and further north).  We do use lights in the summer but not very much.  I would guess that 75% of our usage is when it is cold.  So if the excess energy goes into the room which we want to keep warm how is it wasted? ??? The other heating in the home is controlled by thermostats so if another source such as a light bulb provides a little heat then is it not just great? 

Just a theory....


 

nixietube

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Is energy really saved with energy efficient light bulbs?
« Reply #1 on: 13/12/2009 19:39:24 »
In amongst the greenwash there is an interesting gem...

Switching to these lamps ( and we now have legislation ) will reduce the FUTURE transmission requirements on our national grid.
 

Offline techmind

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Is energy really saved with energy efficient light bulbs?
« Reply #2 on: 13/12/2009 20:04:47 »
I fully support all moves for decreased usage of energy.

BUT, I do wonder about energy efficient light bulbs.
...

Firstly, and not most importantly, what is the total lifecycle cost in energy of these bulbs compared with incandescent bulbs?
... what is the true life of these bulbs because it is not what is advertised.

Secondly, undoubtedly they consume less energy for the same light emitted.  But with a traditional bulb where does the excess energy go?  The answer is that it is output as heat...

All very valid points, which have been discussed here before, I'm sure.

I think the short answer is that (in general) yes they will save energy overall, but considerably less than the CFL's proponents would have you believe.

There was some significant discussion of this on this Friday's (11th December 2009) Radio 4 "More or Less" programme http://www.bbc.co.uk/podcasts/series/moreorless/
and the spin-off BBC News Magazine article: http://news.bbc.co.uk/1/hi/magazine/8406923.stm


While I hate the CFL bulbs and the greenwash and the politics, I still think the More or Less programme came across slightly unfairly heavily against the CFL bulbs energy-savings.

The heat-substitution effect (thermostatic heating system 'compensates' for heat not created by the incandescent bulb) is perfectly valid, but while a gas-powered heating system may be 70~80% efficient, electricity generation is more like 30~40% efficient (it's losses in the power station - transmission losses are rather small) - so it's still better to get your heat from the a gas-fuelled heating system rather than from electricity.
(The fact that electricity is typically 3 to 4 times the price of gas per kWh should drop some hints about the inefficiencies in making the electricity!)
 

Offline PAG

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Is energy really saved with energy efficient light bulbs?
« Reply #3 on: 11/01/2010 14:47:18 »
Thanks for those comments.  :) I see the point.

I Googled around to confirm your figures and I found that normal boilers claim 90% thermal efficiency while a good power station has about 60% and this decreases to about 55% when you take into account transmission.  Looked at like this it is clear that the gas boiler wins and with it the CFL bulb.  So yes you’re right.

The other interesting thing you point out is the difference in prices (3 to 4 times), which is correct but doesn’t tie up with the efficiencies above.  Is this because there are other costs associated with the electrical distribution that are not incurred for gas and if so should these also be taken into account in favour of gas?

Does this not invalidate the CO2 argument for electric cars? ???
 

Offline durrenmatt

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Is energy really saved with energy efficient light bulbs?
« Reply #4 on: 19/01/2010 16:13:07 »
energy-efficient light bulbs do save some energy, but if you really want to see a difference on your power bill you should try LED lights! They may be a bit more expensive than traditional lights but the save a lot of power.
 

Offline peppercorn

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Is energy really saved with energy efficient light bulbs?
« Reply #5 on: 20/01/2010 13:08:47 »
...a good power station has about 60% and this decreases to about 55% when you take into account transmission.
...
Does this not invalidate the CO2 argument for electric cars? ???

Petrol & Diesel engines turn less than 30% of the fuel's energy into work. Factor in fuel processing from crude oil & it's down to nearer 20%.

Electric motors should deliver around 95% efficiency, giving overall efficiency of perhaps 50%.

The complication comes from what mix of generating technologies is used to supply electricity through the national grid.  as a point of reference petrol delivers around a quarter to a third of its thermal energy from its carbon content.
« Last Edit: 20/01/2010 13:13:52 by peppercorn »
 

Offline diane21

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Is energy really saved with energy efficient light bulbs?
« Reply #6 on: 14/10/2011 20:25:14 »
LED's use less energy than a Compact Fluorescent for the same light output. Fluorescent bulbs contain mercury and pose a danger to the environment.Some may be required to pay for disposal of fluorescent bulbs.If the bulb breaks, it contaminates it's surroundings including food. Proper clean up can be expensive.

Spam link removed, user banned
« Last Edit: 15/10/2011 15:21:09 by BenV »
 

Offline marie_turner2011

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Is energy really saved with energy efficient light bulbs?
« Reply #7 on: 15/10/2011 11:37:36 »
I do agree with you LED's do use less energy as compared with other bulbs but also pose danger to the environment, but as science is being improved more better ways of saving energy are being invented.
______________
 

Offline Geezer

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Is energy really saved with energy efficient light bulbs?
« Reply #8 on: 15/10/2011 15:54:03 »
I do agree with you LED's do use less energy as compared with other bulbs but also pose danger to the environment, but as science is being improved more better ways of saving energy are being invented.
______________


Where's the danger to the environment?
 

Offline Airthumbs

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Is energy really saved with energy efficient light bulbs?
« Reply #9 on: 16/10/2011 00:40:19 »
Just a quick point to mention.  I run a hotel here with about 18 rooms.  We buy these eco bulbs to reduce the cost of electricity but.. and it's a big but.  On the side of the package it states that the bulbs will last 8yrs!  Often you might see that the figures are given in the thousands of hours or more.  Never, not once in my two years running this place has a bulb ever lasted more then 6 months.  Some of them have gone in weeks not years!!   In the decision making process paying more for these bulbs seems cost effective as we would not have to buy more for quite some time.  This is not true so are we being conned? 

Does anyone else have the same experiences with these bulbs that say they will last years and then go after a few weeks?  The worst case I had of one of these bulbs failing quickly was literally in two weeks after being fitted in to a light with a motion sensor built in.  The total time the bulb was active for was about 3-4 hrs maximum. 

In history we know that light bulb manufacturers deliberately built in redundancy into the light bulb design so as to create a profitable business.  No one wants to run a business where your customers only buy once in a lifetime, unless your a church in which case you make a lot of money from that!
 

Offline SeanB

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Is energy really saved with energy efficient light bulbs?
« Reply #10 on: 16/10/2011 12:22:54 »
Using a CFL to replace a lamp is not good if the lamp is switched frequently. Rather use a normal incandescent, or a halogen replacement.

The killer for CFL is frequent switching and running hot. The incandescent lamp is not worried about running at 200 degrees or more, and will run to the point where the soldered connections melt off the lamp base. The CFL needs to be kept cool, preferably with the base down, the exact opposite to almost all standard fixtures where the lamp is base up and enclosed. The lamps will last the rated life if they are used correctly, but the fixtures they invariably are placed in are designed for an incandescent lamp, and thus run the lamp at high temperature.

The CFL works best if run for long periods with very little switching, like a lamp used at night, as long as it runs cool. Essentially it is too hot if any part of the lamp body or any point on the glass ( aside from the 2 ends of the tube where the emissive material is) is too hot to hold after it has been running for an hour. It needs cooling, and needs to be base down to keep the ballast area cool. Then, in a good quality lamp ( and those cost a little more and are certain old established brands) you will get a very good life out of the lamp.
 

Offline Geezer

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Is energy really saved with energy efficient light bulbs?
« Reply #11 on: 17/10/2011 07:53:07 »
Roll On LEDs!*

I hope they become much less expensive in the near future. They may not be perfect, but they are far better than the alternatives.


*The FED (Flame Emitting Diode) was really much more interesting, but we're not supposed to talk about that.
 

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Is energy really saved with energy efficient light bulbs?
« Reply #11 on: 17/10/2011 07:53:07 »

 

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