LED-based fixtures need understanding of the semiconductor/electronics packaging side of the business. There are tradeoffs between cost, optical efficiency, thermal performance, glare, photometric distribution, aesthetics, features, mounting depth, etc. It's difficult to figure out which of those compromises are going to be acceptable to the end consumer and the sales channels, and which are going to hinder the product's acceptability in the marketplace. Adoption of retrofit lamps is more defined and less nebulous, in spite of knowing fully well that the true performance of LEDs can be fully obtained in standalone integrated fixtures optimised for LEDs.

It is expected that within the useful life of first generation SSL fixtures, the new LED technology will enable significantly higher efficacy. All the while cost of energy will keep going up, making it compelling change to LEDs.

As we stand at the edge of the LED technology becoming mainstream lighting, there looms a very environmentally sensitive question as to what should we do with the old luminaires and fittings, which run into mind boggling trillions of units. The retrofitting with LED based lights would at once solve the energy saving as well as the luminaire recycling issues. Billions of sockets are beckoning you as a vast business opportunity. Thus retrofitting is more the result of a business model than a real serious response to technological advancement. Retrofit is a shortcut that can be partially applied to a technology like LEDs and only at this early stage solid-state lighting evolution. Retrofit design has happened to many industries: in the case of camera industry, only the lenses were saved, and not total housing.

The body of a digital camera had to be re-engineered and only the appearance was retained. Same with computers: you don't retrofit them; you never open the laptop to change the motherboard inside. Motherboards are unique for models that change constantly. One cannot replace the motherboard of Apple MBP unibody inside any older Apple MBP. Similar is the case with cars - one cannot transplant the improvements in combustion inside an old car.

T8 Tubelight Retrofit Lamps

A T8 retrofit is a compromise idea for two reasons: in terms of electronics you have to include a device to get the power delivered via an old transformer (ferromagnetic or electronic) to be able to power the DC LED chipsets. Equivalent integrated fixture called LED linear lights have on-board drivers and they do work well enough. In retrofit T8 you have a poorer thermal dissipation no matter how much aluminium you place to absorb the heat, especially if you are talking about enclosed devices. The "Patti" device was designed for tubes that did not needed to be ventilated as SSL-LEDs. The LED tubes get much hotter than linear lights. One mitigation has been to use hundreds of low current LEDs in place of high power LEDs.

The availability of cooler mass right around each such LEDs greatly influences the temperatures levels from accumulating.There are several stand alone linear light models that look like tubes. Yet, one cannot ignore T8 replacement market that is so staggeringly huge (800 million sold each year in India as replacements) that there will certainly still be retrofit linear lights for ten more years from now.

Replacement modules will score here as they cheaper. There is no way everybody will rip out their fluorescent ceiling, warehouse, or signage fixtures as long as the modular side of the industry gets and stays competitive. The reason retrofit will always be in fashion is simple economics. No country can reasonably be expected to trash hundreds of millions of 4-foot fluorescent fixtures.

Merits of Retrofit LED Lamps

There are several reasons why a consumer wants a replacement lamp.

• It saves costs of outer luminaire as well cost of labour and time to pull the old fixtures out of the ceiling and replace them with new ones.
• Benefits of LED lighting can be brought in even before end of standard maintenance cycle of the Fittings. Retrofitting suits any fixture that has a large enough mechanical envelope.
• Huge opportunity - billions of existing "sockets" out there.
• Inertia - it will take time for decisions that call for migration to completely integrated LED systems, giving longer opportunity window for retrofit business.
• Design aspects: we'll need a new series of bases or platforms that are more suitable for issues involving thermal dissipation.
• End of Life issues: In 5 years the total Lumen output of that fixture would have depreciated to less than it is today and may need replacement with a newer one even if it hasn't "failed". Having opted for a retrofit in the first cycle would have brought down the cost of the first cycle of relamping.
• Cost aspects: The Integrated LED lamp could be expensive since it maximizes the advantages of a LED light source, which is not compromised, by being a "replaceable lamp". Generally speaking, a lamped and ballasted 2x4 fixture costs a little more and delivers optimised performance than the lamps and the ballast separately.
• Maintainability aspects: In a lot of applications (task lighting, track lighting, chandeliers, pendants) replacing the entire fixture takes little more labour or expertise, but it would be easier to slip in a LED retrofit.

Merits of Integrated Fixtures v/s Retrofit Lamps

While the best integrated fixtures have an efficacy edge of 30-50% over currently available replacement lamps - there are things you can do in a fixture that are really quite difficult (and in some cases not possible) with a retrofit lamp. Lamp users really buy light with specific function and features. Anything the customer does not require is a waste. The integrated fixtures by design include less waste and all agree that long-term we will see more integrated fixtures designed from the LED up and out.

The retrofit LED has reduced performance due limitations imposed by form factor as well as or near zero convection airflow when placed inside the legacy fixtures. Designing the electronics and thermal solution into a contrained form-factor definitely call for tradeoffs with serious consequences in terms of performance dilution. Either it will cost more, or not perform as well, or perhaps both.

It may be noted that in this recycling action of retrofitting, actually we are just avoiding replacement of the cheapest parts of the assembly - the sheet metal, only. This is not an economically speaking wise solution. But, once shorter life span is psychologically accepted, the overall cost can be brought down to very attractive level to trigger large scale adoption of retrofit bulbs. The reason is not difficult to be understood. One, it is very convenient for the user to do the change all by himself, and two, all such refitting can be taken up in phased manner and it also allows unplanned and random conversions.

Replaceable Ballast Driver is Another Workable Option

Making the driver easy to replace will be much more useful for your end users than replacing the entire LED/heat sink assembly.

The LED fixture solution is only as good as it's weakest link - the driver. In a well-designed LED fixture, the life of the electrical components used to drive/control it are limited There no point in developing an LED package and thermal solution that will last 100000 hours, and including a driver assembly that won't last 25000 hrs. Replacement ballasts will have their place for use with off the shelf LED modules, and will become more prevalent as the technology standardizes over the next 5-10 years.

However every manufacturer has different technique of connecting and sealing it. After 5 years of use, it will be difficult for the customers to replace the connector or driver modules or LEDs as they are too individual in design. Compliance to common standards for interconnection and size dimensions, alone will be the answer. The ZHAGA standard is right step in this direction, and being widely accepted. We may need more simple, cost effective interconnection standards for lower cost applications. It goes without saying that experience with retrofit bulbs and tube lights can lead to such new standards.

Over the coming years, the LED portion of the BOM (Bill of Material) will get dramatically smaller, due to higher efficacy and better manufacturing efficiencies as volumes ramp up, while the driver portion of the BOM less smaller as their components are already used in very high volume off-the-shelf. So the driver will become a larger portion of the total lamp or fixture cost over time as a percentage. The challenge with standardising the driver and making it replaceable is: which technology do you choose? Phosphor converted white, which presently the one dominating? or RGB? or RGBA? Each requires different ways of driving and control systems and sensors. "Standardising" today requires picking a winner blindly even before the market has played out. Removeability (modularity) typically adds complexity and cost, and the market is still at a point where most LED products aren't at cost parity with incumbent technology yet.

Standardisation & Innovation

Standardisation and innovation are always a trade-off. If you push one, you diminish the other, but there is still significant room for both component innovation and system integration innovation all across the LED food chain. This said, there are designs and reliable technology from both start-up companies and established firms. The difficulty in the market place is the discernment of the good from the not-so-good. To be fair, both older established companies as well as the new "innovator" companies should be considered.

One factor that inhibits wider use of LED lamps is lack of user relevant labeling: Many users desire a LED fixture that puts out a usable amount of lumen's at a targeted area with metrics that is not so complicated. The customer should be able to make a good guess as to how many 'Lux' he will get at a desk height with a sufficient colour rendering at not so exorbitant price.

Looking Ahead

The LED-based lamps will continue in products that are primarily lamp-holders, like domestic lights and incandescent track heads. We are going to see the maintenance of lighting evolve as LEDs begin to take a lot of share from Fluorescent. Soon companies will cart out to offer lighting as part of your HVAC maintenance contract. Soon the capital cost will be free and absorbed into AMCs (Annual Maintenance Contracts).

We assume that the buyers make rational economic decisions and push the market quickly to integrated solutions. They don't. The advantage retrofit systems have is that they look and feel like "bulbs". The growing tendency towards LED T8 replacements makes less logical sense from an engineering perspective but can carry the marketing message of a green replacement in a form factor the buyer understands and trusts.

LED makers are concentrating on improving the structures of the smaller LED chips to bring their efficiencies on par with larger chips.

Conclusion

There is a case for the citizens to convert to LED lighting right away and begin save energy. Worldwide if by some magic all tubes were replaced with solid-state linear lights as soon as the existing light fails, we end up with huge savings in the energy and maintenance.

This retrofit step is one that most building owners can start doing now. And they should not wait while the integrated products are evolving/improving. Their savings will help pay for the integrated LED fixtures a few years down the road. The thrust could be to Identify the users who run tubes all day and yet can't afford to overhaul the fixtures. Get the utilities to support this, like they did with CFL's and like they are doing with streetlights. While we're doing this, we can and should continue developing the integrated solutions.

Some will adopt the retrofit approach, and some will adopt a unified architecture. The market will reward those who deliver the best value proposition, including performance, cost, quality, quality of light, and lifetime amongst other tangible and intangible value

(K Vijay Kumar Gupta, BSc (Mumbai), BE (IISc 1977), is Managing Director, Kwality Photonics Pvt Ltd, an ISO 9001-2008 company and India's pioneer manufacturer of LED Segment Displays & PolyWa Power LEDs for lighting. 29, Electronic Complex, Kushaiguda, Hyderabad. www.kwalityindia.com kwality@kwalityindia.com 9000081171, 040-23440571)