Let there be (LED) light!

In a recent article, I referred to a bicycle as an invention that has been around for more than a 100 years. It is still essentially the same – and that was a good thing. There is another invention that has been around for the same length of time – but that is not so good. It’s the humble incandescent bulb.

Till fairly recently it has been the primary source of electric light. However, over the last few years, other options have emerged – namely Compact Fluorescent Lights (CFL) and Light Emitting Diode(LED) bulbs. The question then arises – should one switch to using the other types of bulbs? The aim of this article is to analyse the numbers in order to see what is the best option. The quick answer is that LED bulbs are clearly the best, but if you would like a more detailed explanation, read on.

A little bit of history

The invention of the bulb is usually attributed to Thomas Edison and Joseph Swan – but was actually done before them by several other people. However, they were the first to commercialise them. Edison and Swan’s early bulbs used carbon filaments. The bulb in more or less its current form, with tungsten filaments, was invented by the Hungarian Sandor Just and Croatian Franjo Hanaman in 1904 – a 110 years ago.

Perhaps because they were cheap and electricity was not too expensive and plentiful in the West, no substantial changes were made in the design of the bulb for several decades. It’s a bit shocking when you think about it – the bulb in its current form existed before the car, radio, TV, airplane and any other form of technology that is commonplace today!

The fluorescent light has been around for quite a while, invented in the late 1890s by a gentleman named Peter Cooper Hewitt. The CFL was invented by Edward E. Hammer, an engineer working with GE, around 1973. However, it was only after 1995 that they became commercially available and started being used on a larger scale. In many countries the sale of incandescent bulbs has been banned, thanks to the availability of cheap CFLs.

The red LED was invented by Nick Holonyak Jr. in 1962, while working as a consultant scientist for GE. Prophetically, in an article in the Readers Digest in 1963 itself, he predicted that LED bulbs would replace incandescent bulbs. So while Edison – though he is known for it – did not invent the light bulb, the company he founded, which made him a very rich man, has played an important role in the development of bulbs ever since.

The problem with incandescent bulbs

Incandescent bulbs are bad from many angles. They are inefficient: as is evident to anyone who has tried to study using a 60W bulb in the summer, much of the energy is released in the form of heat. So especially in here in India, where heat is a problem, it is not a good thing. They do not last very long – most burn out within a year. The primary reason that they are still popular is that they are cheap to make and buy.

A comparison

Let us compare both the advantages and disadvantages. The primary advantage of the incandescent bulb is that it is cheap to buy. But in the long run that is certainly not the case. For the purposes of simplicity of calculation, we assume that the average house has around 20 bulbs of 60W or equivalent and the cost of electricity is around Rs 5 per unit. Further, we assume that these 20 lights are on for about 3 hours per night.

  • Incandescent Bulb: A 60W incandescent bulb running for an hour uses .06 Watts – which costs 0.06 X 5 =.3 rupees per hour, or 30 paise per hour. Assuming that it is on for 3 hours a night, it costs around 90 paise per day – or 90×30= Rs. 27 per month! Assuming that it lasts a year and costs around Rs. 12 per bulb, the cost per year is 12 x Rs. 27 + Rs. 12 = Rs. 336.
  • CFL Bulb: The equivalent of a 60W bulb is a 11W CFL bulb. Making the same assumptions, the cost per month would be 11/60 x (cost of the incandescent per month) = Rs. 4.95 per month. Or per year, it will cost Rs. 59.4. Adding to this the cost of a CFL bulb, which is around Rs. 150, and assuming it lasts for three years, the cost of using a CFL bulb is Rs. 59.5 + Rs. 50 = Rs. 109.5 per year – or a third of the cost of an incandescent bulb!
  • LED Bulb:  The equivalent of a 60W incandescent bulb, or a 11W CFL bulb, is a 6W LED bulb. With the same assumptions the bulb will use 0.006W per hour. Hence the cost per day is around 9 paise per day or Rs. 2.70 per month. Or Rs. 32.40 per year. The cost of an LED bulb is around Rs. 600 now – but it is supposed to last 20 years. Assuming it lasts 10 instead of the claimed 20, it costs around Rs. 60 per year. Hence the total cost of running an LED is  Rs.60 + Rs.32.40 = Rs.92.40 per year.

Hence if you replace an incandescent bulb with an LED bulb, you will recover the initial cost in two years! For a CFL bulb, it will take a little longer – around six years. A more detailed analysis, of cost per lumen in the US, can be found here: https://en.wikipedia.org/wiki/LED\_lamp.

CFL vs LED 

The analysis shows that CFLs and LEDs have pretty much the same running cost per year. However, there are many reasons why LED bulbs are much better than CFL, so are perhaps worth the extra cost.

  • Since they consume half the energy, they put less of a drain on the electricity grid. In India we have a tremendous shortage of electricity so whatever one can do to reduce consumption is good.
  • Nowadays, many people in Bangalore have an inverter. Typically, one can run 4 or 5 incandescent bulbs for a couple of hours. With the same inverter, one can run LED lights for the lights will run for much longer on it – in this case, around 20 hours!
  • CFL bulbs are not very environmentally friendly – they contain mercury and have to be disposed off carefully. They are quite delicate and break easily. They are supposed to last three years or so but quite often do not last so long. LED lights are supposed to last 20 years without substantial degradation, so the environmental impact is much less.
  • Over time CFLs degrade substantially. Often, one of the filaments burns out and this results in a reduction of intensity of light.
  • Another issue with CFLs is the quality of light. It does not have all the frequencies that the light from an incandescent bulb has – so some things look different. This might be a problem with LEDs as well but is more easily addressed.
  • CFL bulbs can not be dimmed so you cannot regulate the light very well.
  • LED lights, on the other hand, are very versatile. Pretty much anything is possible with LEDs. Since the bulbs themselves are very small, they can be made in all kinds of shapes and colours. There now exist LEDs whose colour can be varied and adjusted by a smartphone app. So one can have different colours of lights for different times or moods. You can also program them to turn on or off at certain times of the day.

Light can promote peace!

One cannot underestimate the importance of light. Apart from the obvious practical benefits of being able to function in the dark light has tremendous influence on our psychological state. High intensity light exposure is the treatment for people who suffer from Seasonal Affect Disorder – depression caused by lack of exposure to sunlight. Jet Lag can be treated by regulating light exposure.

So the lights you put in your house can have a significant influence on your life. In fact, in Los Angeles, some Sodium vapour streetlights were replaced by LED lights. Apart from a tremendous reduction in maintenance costs and energy savings an unexpected side benefit was a significant drop in crime in that area!

While I am advocating running out and replacing all your incandescent bulbs with LED bulbs I am not quite suggesting running out and replacing all your CFL bulbs with LEDs since that would not be environmentally friendly. However, every time a bulb goes bust in your house, I recommend that you replace it with an LED equivalent. You will save yourself a lot of money in the long run and do your bit for saving the planet.

The cost of an LED bulb may seem to be high – but as the analysis shows, it is still a better deal in the long run. However, there is even better news. The cost-per-lumen of LED bulbs is supposed to follow Haitz’s Law, which asserts that the cost per lumen will drop by a factor of 10 in a decade. So if you wait a bit, unlike most other things, the price will come down! And, like in the case of computers, you will get a better product.

So, go LED, as soon as possible!

References
https://en.wikipedia.org/wiki/LED_lamp

https://en.wikipedia.org/wiki/Cfl_bulb

https://en.wikipedia.org/wiki/Nick_Holonyak

http://www.forbes.com/sites/justingerdes/2013/01/25/los-angeles-saves-millions-with-led-street-light-deployment/

Related Articles

In the offing: Plans to produce solar power in Bangalore homes
Cycling to work: Something all the nay-sayers should read

About Ramesh Sreekantan 0 Articles
Ramesh Sreekantan is a Mathematician at the Indian Statistical Institute. He takes a keen interest in cycles - both the algebraic and mechanical kind.

7 Comments

  1. @Ramesh
    Agreed – the technology is probably better, but on this forum we are looking at implementation for public use. There seem to be a lot of claims from manufacturers of LED arrays, CFLs, induction lighting. We should do what we do best – wait for the rest of the world to figure out the best system. Indians already use ordinary tubelights which seem to be quite good. Finally it is the TCO that counts and that includes the environmental cost.

  2. Dear Skeptic – the issues you bring up – while perhaps valid – have more to do with the question of how people might implement them rather than the technology. That is too complicated a question to be addressed here.

  3. Need to look at the pitfalls: 1. No Standards – means cheap, low quality LEDs will ‘burn out’ before even recovering the cost ————————————————————————–
    2. The LEDs may be great but the power supply units fail miserably. _______________
    3. As usual vested interests will supply ‘cheap’ units to the government at our cost.
    4. Watch out for Chinese and Indian manufacturers dumping rejects here and sold to gullible customers.

  4. They have installed LED lights in a few places – and in fact they are much better. On 15th Cross in Malleshwaram, they have LED streetlamps which have greatly improved the lighting in the night.

    The best installation I have see is on 80ft road in Sanjay Nagar, the road which joins MSR Hospital with Sanjay Nagar main road. On one side of the street they have installed LED streetlights + streetlamps – namely, the same pole is used for both lighting up the street as well as the footpath. They are elegant and functional. This should be contrasted with the other side of the street – where, thanks to the residence of a former CM being there, they installed `fancy’ streetlamps. Now all of them are broken and deformed are are an eyesore on that street.

    I do agree that there should be a national policy of using only LED lights for streets – but I dont think its going to happen anytime soon. I think very few national policies are made with the best interests of the nation at heart!

  5. A well articulated article.

    Only other advantage of LED which the author did not highlight is that CFL lights have a limited wattage capacity and not suitable for Street Lights application. Whereas LED’s lights can be made to any wattage as the application demands. Thus ideally suited to replace the currently popular Sodium vapour lamps for street lights application.

    Street Lights being used from dusk to dawn also constitutes a large part of power consumption at any place – be it a city, High way or even villages.

    Across the world more and more cities are changing over to LED street Lights.

    Thus a more pragmatic approach should be to have a national policy to switch over to LED street Lights within a given time frame. It also calls for some National level design and development of LED street Lights including optimum wattage, Height of pole etc thus standardizing the design and application across the country. Once this is achieved such a design can be sold to approved SSI industries who can make them locally and may also be entrusted with maintenance and warranty replacements thus cutting down the grip of multinationals and Big players and thus cutting down on cost and wheeler and dealers.

    Domestic users will follow suit axiomatically once convinced about its advantages.

  6. Too simplistic. CFLs have their negative points about which we were kept in the dark while all the politicians urged us to use them. It is too early to adopt LEDs everywhere, for one, they are way too expensive (I dont buy the – you will save money in the long run story after being burnt by CFLs). If they really want us to save energy, let the companies give it to the public under CSR!

  7. Why not everywhere LED lights in homes and industry spaces, because of having such advantages. In future it has researched that LED technology uses nano-particles for generating sun like light to give a pure sun light.
    Ref – http://www.autopal.net.in/

Leave a Reply

Your email address will not be published.


*


Please solve this *