I feel the temperature rising

Singapore 26th September 2011

Back to LED again…the last few weeks I have been investigating LED (specifically the retrofit types, not so much the light engines) in depth to understand the limitations they have and the characteristics we need to look out for to achieve a successful installation. Today was another such day incorporating discussions with yet another lamp manufacturer. Note I say lamp (=light source) manufacturer, not fitting manufacturer, people who manufacture all core system components including lamp and all other essential elements such as driver and controls. Manufacturers have a tendency to put forward all the positive features of their lamps (conveniently) leaving out the potential negative site effects.

Today’s discussions centred mostly around the heat issues faced with LED’s, specifically after we discovered the problems with the Philips 10W Master LED recently. Now here is the deal…LED’s most critical point is the heat dissipated at junction point between LED and the circuit plate it is mounted on. Apparently it can get pretty hot up there (around 120 degr C I am told). The better the cooling the better the lamp works, so hence all these funky and ingenious heatsink designs we see apearing by various manufacturers. Philips went to the extent to built in a mini mechanical fan inside (!) the lamp to allow the lamp to be as compact as possible. A mechanical component in an electronic system? Seems like asking for trouble! What worries me most is that a 10 degr temperature increase can apparently cause a decrease in life of up to 50%! Really? So how do we control the heat dissipation in there? In the tropics it is hot and humid but at least the ambient temperature is reasonably constant. But Down Under we have day-night time temperature differences of more then 20 degrees on a day! Imagine the heat build up under tin-shed roofs…how is that going to work (or being controlled?). How do we define the acceptable light fittings for LED retrofit, as obviously enclosed types do not seem to be suitable.

The other issue relates to the compatibility between transformer and LED lamp. The transformer has wave curves, while LED has block shaped wave profiles. That obvioulsy does not match very well. No wonder there are so many non compatible transformers (!)…another subject for another day 🙂

In Light Watch today some pics of key players; Philips and Osram. I have added another (new kid on the block) player; Ecogreen which is a company that boosts ex-Philips and Osram engineers. Interesting to see how the products take shape…

Light Watch 170: MR16 retrofits

26. September 2011 by Martin Klaasen
Categories: Education, light watch, lighting design, lighting of the future | 3 comments

Comments (3)

  1. Hello Martin,
    I also was concerned with the actual disadvantages of LEDs. Specialized as grow light for plants – I am a biotechnology man – I came to one fundametal conclusion. Maybe we still use the energy of light, especially provided by light emitting diodes, imperfect ? I started to think about moving lights as they are known in greenhouses. And I figured out a moving light for LEDs with high light energy and high grow light per ²ft and low input energy cause the reduction of the number of LEDs. It is an actual project and we call it SPINLEDS. Maybe this can be another thought-provoking impulse for your valuable investigations.

  2. Dear Drees
    Thanks for your interesting feedback. Photosynthesis, lighting for plant growth, is an interesting subject similar to lighting for endangered animals like turtles and bats as it uses parts of the spectrum that are not necessarily related or important to human needs, but yet have to be integrated in our everyday environment. I am not familiar with “moving lights” in greenhouses, let alone the SPINLEDs, could you eleborate a bit more on their workings and how this benefits plant growth? Is this only suitable for the biotechnology industry or could there be more and wider applications?

  3. Hi Martin,

    sorry for the late response;

    SPINLEDs do generate a kind of intermittent light to the plants (chopperlight.com), by cycling around a propeller with LEDs on it. We actually are trying to figure out the best rotation-speed for photosynthetic reaction considering the characteristics of LED operation temperature and scale of visual effect to the human eye. Temporarily we rotate in the range of 2-5 cycles per second. But regarding the human eye and that almost every PAR-Lamp needs to “look good”, we are working on a solution to speed up the rotation to more than 25 per second. Now, depending on the visual frequency of specified animal types, a high rotation speed definitely has to be adapted, to avoid irritation. I could imagine a wide range of application beside biotechnology, because the kind how the SPINLEDs work is very different to all high energy lamps on the market. I also think about MINI-SPINLEDS, an alternative for lenses on LEDs. The key benefits are: no separate cooling, a very good mix of wavelength depending on the free selectable LED colors, extreme decrease of shadowing and very low heat-radiation to the ground. A special LED-board-air-screw even could direct the air flow from or to the surface.

    Thinking about a SPINLED for bats; In this special kind of illumination, not only the wavelength seems to be important, also the fact of animal echolocation and that the SPINLEDs are rotating objects, make me curious to think more about it.


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