From: Don Klipstein on
In article <epp1k3$4pe$1(a)>, Michael Black wrote in part:
>As energy consumption goes up, they have to keep building new plants,
>which can be costly. If they can throttle back each individual's demand,
>then the power companies can live longer with existing generators.
>Here in Quebec, Hydro keeps wanting to increase rates, with the claim
>that it will reduce consumption. Now, they get to play the
>"it's good for the environment to reduce consumption" card, yet
>given that most of the generators in the province, maybe all, are
>hydroelectric, electric useage is not the issue that it is where
>coal or oil power plants are located. The reality is that if
>they can get homeowners to reduce consumption, that leaves plenty
>of electricity with current plants that they can sell off to other
>power companies.
>One of the conundrums of electricity is that in order to supply
>all demands they end up with capacity that isn't used all the time.
>If they can cut back in those peak times, they don't have to
>add capacity.
>It's kind of amusing to see the electric company here wanting
>consumers to cut back on useage, given they used to really promote
>electricity, and I seem to recall they even gave rebates for people
>who switched over to electricity for heating. They want to raise
>prices so consumers will cut back, they've deliberately said that,
>when in the past they touted the cheap electricity and wanted people
>to convert.

One thing about electric heat: Heating is needed more at colder times
of the day and at colder times of the year. In a lot of areas this does
not increase peak demand since in those areas the annual demand peaks are
in hot times of the day on the hottest days of the hottest time of the
year, for air conditioning.

As a result, in many areas electric heating does not affect the peak
demand and need for ability to supply the peak demand.

It is common practice for electricity to be available at special lower
off-peak rates when billed through meters with clocks to only allow
consumption at lower demand times of the day. A common application of
circuits fed by these is water heaters for supplying hot water. Another
example is how the University of Pennsylvania achieves a good portion of
its air conditioning - that is done by chilled water lines cooled by ice
made at a chiller plant that uses off-peak electricity to make ice that
does the chilling.

- Don Klipstein (don(a)
From: Don Klipstein on
In article <1170296274.727935.120210(a)>,
throwitout(a) wrote:
>Incandescent flashlights are terribly inefficient (even compared to a
>household 120V incandescent), as well in the high shock environment of
>a flashlight, the durability and long life of LEDs is a plus.

As for the efficiency of incandescent flashlight bulbs - I would say
same ballpark as 120V ones despite some economies of scale of
incandescents mostly favoring lower efficiency of lower wattage ones.
The biggest reason is that most incandescent flashlight bulbs are
designed aggressively and have design life expectancy mostly 15-35 hours.
A secondary one is that for a given wattage and life expectancy,
efficiency of an incandescent of wattage of around a watt to a few watts
is maximized by designing it for a low voltage typically in the general
ballpark of 6 volts. Mainly, higher design voltage requires a thinner
filament that must operate at a lower temperature (less visible light and
more infrared) for the same life expectancy.

> As well they have much better characteristics as the battery dies than
>an incandescent.

True! Incandescents have energy efficiency varying directly and
somewhat to significantly more than proportionately with applied voltage,
and usually proportionately to roughly the cube (or worse) of the amount
of current flowing through them. On the other hand, most white LEDs have
enerhy efficiency actually alightly increased when they are mildly or
moderately or even moderately severely "underpowered".

> Also, most "white" LEDs have poor colour rendering
>quality, and colour temperature. While adequate for something like a
>flashlight, I wouldn't want that kind of ugly light lighting my house.
>It will take more R&D to improve this.

Believe me, they are working on this. "Warm white" LEDs with color
rendering index of 85 (where maximum is 100) already exist.

>> I believe there were quite a few LED Christmas lights
>> recently; more expensive initially but lower cost to run.
>Unfortunately the output of these LED Chrismas lights is quite dim
>unless you look at them straight on,

Improved in recent years! I have seen them!

> and the output is very flickery.

Easy enough to improve by well-enough-known means if enough consumers
feel the need to speak out!

>> Many cities have taken to use the LEDs in traffic lights as well.
>Several factors here. Traffic signals use single colours (Red, Amber
>and Green), LED technologies for those colours have been perfected
>long ago. Monotone LEDs have better efficiency than white LEDs, and a
>better lifespan.

As it turns out now, the latest and greatest white LEDs now on the
market now have more lumens per watt than the latest and greatest on the
market of any spectral color. As for what has the most watts of light out
per watt of electricity in - that's blue, since blue LED chips are used in
those white ones. The usual white LEDs including the latest higher
efficiency ones have blue-emitting chips combined with a phosphor that
absorbs some of the blue output and in response fluoresces out a yellowish
output that gets mixed with the remaining unabsorbed blue output to make
white. These white ones have more lumens per watt than the related blue
ones because the human eye is more sensitive to yellow light than to blue

>An incandescent bulb in a traffic signal must be a long life, shock
>resistant bulb, so immediately you loose a lot of efficiency (compared
>to a normal incandescent), and as well, of the white light the bulb
>puts off, all light except that of the desired colour is filtered out,
>further reducing efficiency.

This accounts for red and green traffic signals with incandescents
easily being only about 20% as efficient as household lightbulbs of the
same wattage.

>Traffic signals are also very directional, which is a light pattern LEDs
>excel at. All in all LEDs are very well suited for traffic signals.
>However, I see very few people lighting their homes with traffic signals.

How true!

>LEDs are great for certain applications, however it will be a while
>yet before they replace general household lighting, IF they replace
>general household lighting.

The biggest obstace now is actually the cost of high efficiency white
LEDs. Ones of at most a few watts cost more than 4-foot fluorescent
bulbs, most incandescent bulbs and even promotion-price compact
fluorescents, while high color rendering index warm white versions with
efficiency like that of compact fluorescents have yet to hit the market.

- Don Klipstein (don(a)
From: Don Klipstein on
In <srhi-DFD342.09111931012007(a)>, Shawn Hirn wrote:
>A news report I recently heard on a public radio station said that a new
>kind of energy efficient LED light bulb is available for residential and
>commercial buildings. This news report said that Wal-Mart is the largest
>corporate user of energy in the United States and they are buying up
>these light bulbs in huge quantities to replace older bulbs in their
>stores. They are replacing less efficient bulbs with the new LEDs as the
>old bulbs burn out and they are already saving a lot of money on power,
>but this also benefits the environment.
>Evidently, as a result of Wal-Mart buying so many of these LED bulbs,
>the price has gone up high and its hard for consumers to buy them for
>home use because the manufacturing isn't up to demand yet, but that's
>likely to improve over the next few months.

I sure haven't heard anything like that yet! Should I go to the WM
nearest me, am I supposed to expect even 1% of the lighting (by lumen
count) that they have done so far with fluorescents to now be being
done with LEDs?

Keep in mind that a 1.2 watt LED costs more than a 4-foot fluorescent
bulb, and I have yet to hear of LEDs other than laboratory prototypes
producing more lumens per watt (at full power) than commonly available
F32T8 4-foot fluorescents.

LEDs are advancing, but it's going to be a while before they advance
enough to be suitable for most room lighting.

- Don Klipstein (don(a)
From: Don Klipstein on
In article <betatron-4835FE.08361931012007(a)>, fluffy bunny wrote:
>In article <srhi-DFD342.09111931012007(a)>,
> Shawn Hirn <srhi(a)> wrote:
>> Evidently, as a result of Wal-Mart buying so many of these LED bulbs,
>> the price has gone up high and its hard for consumers to buy them for
>> home use because the manufacturing isn't up to demand yet, but that's
>> likely to improve over the next few months.
>I expect that LED's are going to virtually exterminate hot-filament and
>gas discharge lamps in almost all applications over the next decade,
>barring niche-applications such as [can't think of any]. They will,
>soon, revolutionize the way we think about illuminating our homes and
>In twenty years, old style lamps will be curios, much like kerosene
>As replace incandescents, they will obviate the need for terawatts of
>illumination power over the next few years, and even, by dint of their
>incredible reliability, save lives.
>Its hard to overstate the breakthrough (or if you prefer, the profound
>incremental steps) represented by the recent few years of LED
>engineering. The LED flashlights for sale today are impressive, but
>they're not state of the art, and the state of the art has a ways to go
>before it plateaus. They're truly a modern miracle.

It's going to be a while and the advance of LEDs is going to be slow.
And the main obstacles now for LEDs are cost reduction. Available now
only in recent months are white LEDs with efficiency getting into the
fluorescent range, with such efficiency at about 1.2 watts per LED with
these LEDs in quantities of thousands costing more than I pay for 4-foot
fluorescents at home centers.

The latest announced laboratory prototype for high efficiency white LEDs
already has about half the efficiency of a white LED based on a phosphor
with 100% quantum efficiency coated onto a 100% efficient blue LED chip.
I see the top efficiency level of efficiency of the laboratory prototypes
already getting into a plateau, while at that level only about 50% above
the efficiency of some very common fluorescent bulbs in common real-world

LEDs are advancing (at about half the pace of advancement of computers
during the years both have existed), they will eventually become a major
light source, but beware the hype!

- Don Klipstein (don(a)
From: Ron Peterson on
On Jan 31, 10:14 pm, d...(a) (Don Klipstein) wrote:
> In <srhi-DFD342.09111931012...(a)>, Shawn Hirn wrote:

> Keep in mind that a 1.2 watt LED costs more than a 4-foot fluorescent
> bulb, and I have yet to hear of LEDs other than laboratory prototypes
> producing more lumens per watt (at full power) than commonly available
> F32T8 4-foot fluorescents.

That's true for white LEDs which use flourescent material, but
monochrome LEDs can be more efficient on a lumens per watt basis for
applications like stop lights.

It's still taking a large number of LEDs to give an adequate lighting
level. See
sku__KH150 .