Drop the Hammer

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In the past the ‘on-time’, or the time it takes for the light bulb to light up completely, was a problem. Today, this is still somewhat of an issue. CFLs require pre-heating of the electrodes, which could take up to a second in the past. When people would flip the switch it would take a second for the bulb to turn on. That second of no light was a lot of time when you had already flipped the switch and expected the light to shine.

In order to minimize this start time, there are two options. The first and quickest way to do this is called Instant Start. By putting a slightly higher voltage in the ballast, the light will turn on when the switch is flipped. At this point it is still not stable because the lamp is not at equilibrium, but at least some light will come on in the beginning. In approximately the first minute the light will probably continue to increase in intensity.

The Rapid Start System had an average startup time of about 750-1000 milliseconds. Now, with the new electronic ballasts and the program start it can be done in about 200 milliseconds. The light will come on faster and is better than the original Rapid Start. This amount of time is pretty much unidentifiable by the human eye, the light comes on essentially instantaneously.

There have been so many enhancements to CFLs over the years including no flickering, faster start time, good light output, more shapes and sizes, it is difficult to understand why people still worry about them. What about safety? The use of high frequencies have good and bad qualities in CFLs. High frequencies help start the lamp easier, however when the lamp fails it does not go out as easily – the lamp is not extinguished right away. This is referred to as the ‘end of life’ problem with the latest version of electronic ballast. In the past the ballasts did not have the ‘smarts’ to know when they were failing, continuing to strike the fail lamp which could cause them to overheat. Today when the light begins to fail, it will simply shut off and there is no safety issue associated anymore.

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Ed has made inert gas lamps in the past in order to try to eliminate the use of mercury. He replace the mercury in the bulbs with inert gases to create the correct color combination. The best lamp he could come up with in doing so created only 20-30 lumens per watt. This was better than the average incandescent light bulb, but therefore also had less than half the efficiency of a fluorescent lamp.

His next attempt was to remove the phosphor from the lamps and leave the mercury, thus using the light from low vapor pressure mercury. This caused the lamps to go from 75 lumens per watt to 7 lumens per watt, clearly not a solution. That is even less than an incandescent bulb’s lumens per watt.

Currently there are laws evolving around the use of incandescent light bulbs in the future. They are moving towards the regulation that bulbs used in the future need to be 30 lumens per watt or better. Currently incandescents do not fit this standard and a new type of incandescent bulb will need to be developed if they want to survive. The present initiative is for incandescent light bulbs to be phased out by 2012 in the US, and possibly 2010 in Europe.

LEDs vs. CFLs. LEDs have been suggested as a replacement to CFLs, since CFLs use mercury. LED lamps are NOT as efficient as CFLs. They do not work well as a general light source to replace incandescent bulbs like CFLs. LEDs do not have the same amount of lumens per watt. There are also heat issues with LEDs as they tend to get extremely hot. CFLs on the other hand remain cooler than even incandescent bulbs. LEDs are better for specific purposes, such as their current uses in flashlights or traffic lights. The light given off from LEDs does not make them suitable for reading light like fluorescent lighting that creates the full spectrum.

There are so many types of lighting to choose from today it can be difficult. There are incandescent light bulbs, CFLs, LED, HID. It seems that each type of light is better for different applications. The fluorescent lighting market is much more broad. Others have a more specific ‘best application’ such as LED lights for traffic lights or flashlights and HID lights for stadium lighting.

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Process of Heating the Filaments

The next topic Ed discussed moved to an electronic aspect and the optimization of the ballast. It is important when making the lamps to make sure the filaments are not heated too fast or too slow, as each would have a negative effect in the lamp. The rate at which the filaments are heated create the result of how fast the light will turn on.

There were limitations with the first electronic ballast. Scientists did not really know what a lamp did or did not need to properly function. Once the needed adjustments were finally realized the changes could be implemented into the design, which led the new ballasts being much better than the eletro-magnetic ballast could ever be.

Since 1938, when the first practical CFL was made, the process has always been the same to create them. The function of a CFL goes something like this: the filament is heated, the electrons jump off the filaments which caused them to bump into mercury atoms. The mercury absorbs some energy and gives off some energy in the form of photons, which then land on the phosphor to create visible light. This visible light can be made into different colors based on the composition of the phosphor.

Is Mercury the BEST Element to Function in CFLs?

Mercury in CFLs has been a topic of controversy these days, with the growing green movement. So, is mercury really the best or only element that can be used to make CFLs? Ed explains why mercury is indeed important to CFL production, despite the controversy.

He says that it seems that mother nature has chosen mercury to be the ideal element for this type of lamp (CFLs). Vapor pressure in the lamps, at the right temperature, is perfect with mercury. He says using a different element, such as cadmium, would not work out for the best. In order to get the correct vapor pressure at the same level (as with mercury), it would take much longer for the light to turn on. This, coupled with the fact that the bulb would have to be a much hotter temperature and add the risk or burning anyone who touched it.

The option of combining mercury with cadmium, to lower mercury amounts, would also not be useful – Ed points out that cadmium is also a banned element.

Based on Ed’s knowledge, mercury really is the best element possible as an option at this time. The environmental impact amount of mercury that is needed in fluorescent bulbs is still less harmful to the environment than the production of incandescent bulbs. The greatest source of mercury in our today air comes from burning fossil fuels such as coal, the most common fuel used in the U.S. to produce electricity. Since CFLs use 75% less energy than incandescent bulbs, they are dramatically cutting down on the amount of CO2 released into the environment.

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Ed Hammer found that he was competing against himself when he was working with different lighting. He had the HID lamps which had a life of 20,000-24,000 hours and then there were fluorescent lights with a life of 10,000 hours. He decided that he needed to get the fluorescent lights up to a life of 20,000 hours to be competing with high pressure mercury.

The first step taken was in changing the electrode. He used an optimized overwind on the filament and extended the length of the filament. This created the opportunity to put more of the emission mix on the filaments as they were longer. The ratio held up to increase the life of the bulbs significantly. Normally 4mg of mix were used making the life 10,000 hours, so when 8mg of mix were used the life did increase to 20,000 hours. He said even an increase of 50% would have been nice, but he got it all the way to a 100% increase!

He then designed a stick cathode that could hold these 8mg of mix. From here, the life of the lamps went up to 20,000 hours. This was the birth of the fluorescent lamp with a life of of 20,000 hours in the U.S.! This same type is used today, but has been improved with electronic ballasts. These help to cut down on the sputtering of the filaments, and the life of the bulb can be extended even beyond 20,000 hours.

The emission mix on the filaments that is discussed is a triple carbonate ( made of barium, calcium, strontium carbonate). This is used in virtually all fluorescent lamps today. They are heated during the lamp creation process to turn to oxide, which enables them to emit electrons and function (CO2 breaks down). They must be heated in the process in order to emit the electrons. The electrons can then come out freely leading to: minimizes sputtering, longer life, cleaner ends, and better maintenance of the bulbs.

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How Have Colors of CFLs Changed Through the Years?

Fluorescent lights have changed in many ways over the years. When it comes to color, Ed Hammer explains that there are two aspects to consider:

1. Color CRI (Color Rendition Index)

2. Efficiency

Color is based on CRI or the Color Rendition Index. An incandescent lamp has a CRI of 100. Essentially this means that it reflects every color equally, hence you see white because no colors are absorbed.

In order to create a more efficient and better maintaining bulb the Triphosphor system was introduced. It uses a refractory (aluminum) oxide host, which generates more efficient phosphor with better maintenance (compared to the traditional halo phosphate). The Triphosphor system uses 3 rare Earth phosphors. These have a more stable host structure but also are more costly, which is why they were not initially used. This system helps the bulbs to receive better lumens per watt and better maintenance over the life of the bulb.

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Beginning of the Fluorescent Lamp
Fluorescent lights have been around longer than you may think. The first of the linear fluorescent lamps was presented in 1939 to the public at the New York World’s Fair. However, they were still not presented to the market this early in time. Ed Hammer was the owner of the first fluorescent lamp ever made in 1936, 3 years before the one presented at the World’s Fair. He had it in his lab and as far as he knows it was the only one in the world. It was a globe shape with 2 electrodes in the middle. Unfortunately it was moved and has since been misplaced.

Through the 1940′s and 50′s there was literature that stated that high frequency lighting could be created. In the 1950′s and 60′s scientists continued to work towards a better fluorescent lamp. There was a high frequency fluorescent lamp created by Jack Campbell in a city library in Mexico around this time.

What Took So Long for Fluorescent Lamps to Enter the Market?

The original fluorescent lamps only have a life of 2500 hours. Even though this was already better than the comparable incandescent bulbs (750 hours), there were other issues holding them back. There was not a lot of high speed equipment to make the lamps at that point in time, and because of this it led to extremely high costs. On top of all of this they contained elements that were very harmful to the environment.

What Steps Were Taken to Finally Reach the Market?

In 1950 there was some progress as they discovered how to turn phosphors to liquid instead of organics. This helped meet EPA standards as well as make it easier to coat the lamps. The manufacturing process was improved which led to better maintenance (how the quality of light output remains).

The next step was the improvement in lamp life when zirconia was added as a ‘glue’ to hold the emissions mix to the filaments. This increased the life from 2500 hours to 7500 hours!

According to Ed, it turns out the GE had the patents to the phosphor to liquid process and Sylvania had the patents to the zirconia process. They decided to exchange the patents as a fair trade.

Improving the process was the next development, by using more pure mercury and having better control of the phosphor size. The life of the lamp was again improved, from 7500 hours to 10,000 hours.

The next step was for the electronics crew to create the ballasts to accompany the lamps. In the 1960′s electromagnetic ballasts were used as they were cheap and simple. They lasted a long time but had some issues such as causing buzzing or flickering of the lamps. Since then these have obviously been improved, as it is imperative for the electronic ballast to work and be as efficient as the lamp itself.

“A compact fluorescent is a marriage between a lamp and a ballast, and if designed properly they work together”

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