One of the things we’ve been able to change in our new house is the lights. The house, being only 9 years old has been fitted throughout with halogen down-lights. Very much the modern lighting and effective at lighting, particularly in a house with low ceilings where hanging chandeliers or even normal light shades are not practical or safe. However, halogen light bulbs have a bit of a bad reputation for being hot and expensive. They were also all pretty grotty so they needed changing and we decided to make the change to LED. LED or Light Emitting Diodes are not particularly new technology, having been used in electronics for decades but their ability to create white light is much more recent and hence their use in lighting is still pretty new.
- Efficiency: LED’s emit more light per watt than incandescent light bulbs. Their efficiency is not affected by shape and size, unlike fluorescent light bulbs or tubes.
- Color: LED’s can emit light of an intended color without using any color filters as traditional lighting methods need. This is more efficient and can lower initial costs.
- Size: LED’s can be very small (smaller than 2 mm2) and are easily attached to printed circuit boards.
- On/Off time: LED’s light up very quickly. A typical red indicator LED will achieve full brightness in under a microsecond. LED’s used in communications devices can have even faster response times.
- Cycling: LED’s are ideal for uses subject to frequent on-off cycling, unlike fluorescent lamps that fail faster when cycled often, or HID lamps that require a long time before restarting.
- Dimming: LED’s can very easily be dimmed either by pulse-width modulation or lowering the forward current.
- Cool light: In contrast to most light sources, LED’s radiate very little heat in the form of IR that can cause damage to sensitive objects or fabrics. Wasted energy is dispersed as heat through the base of the LED.
- Slow failure: LED’s mostly fail by dimming over time, rather than the abrupt failure of incandescent bulbs.
- Lifetime: LED’s can have a relatively long useful life. One report estimates 35,000 to 50,000 hours of useful life, though time to complete failure may be longer. Fluorescent tubes typically are rated at about 10,000 to 15,000 hours, depending partly on the conditions of use, and incandescent light bulbs at 1,000 to 2,000 hours. Several DOE demonstrations have shown that reduced maintenance costs from this extended lifetime, rather than energy savings, is the primary factor in determining the payback period for an LED product.
- Shock resistance: LED’s, being solid-state components, are difficult to damage with external shock, unlike fluorescent and incandescent bulbs, which are fragile.
- Focus: The solid package of the LED can be designed to focus its light. Incandescent and fluorescent sources often require an external reflector to collect light and direct it in a usable manner. For larger LED packages total internal reflection (TIR) lenses are often used to the same effect. However, when large quantities of light is needed many light sources are usually deployed, which are difficult to focus or collimate towards the same target.
- High initial price: LED’s are currently more expensive, price per lumen, on an initial capital cost basis, than most conventional lighting technologies. As of 2010, the cost per thousand lumens (kilolumen) was about $18. The price is expected to reach $2/kilolumen by 2015. The additional expense partially stems from the relatively low lumen output and the drive circuitry and power supplies needed.
- Temperature dependence: LED performance largely depends on the ambient temperature of the operating environment – or “thermal management” properties. Over-driving an LED in high ambient temperatures may result in overheating the LED package, eventually leading to device failure. An adequate heat sink is needed to maintain long life. This is especially important in automotive, medical, and military uses where devices must operate over a wide range of temperatures, which require low failure rates.
- Voltage sensitivity: LED’s must be supplied with the voltage above the threshold and a current below the rating. This can involve series resistors or current-regulated power supplies.
- Light quality: Most cool-white LED’s have spectra that differ significantly from a black body radiator like the sun or an incandescent light. The spike at 460 nm and dip at 500 nm can cause the color of objects to be perceived differently under cool-white LED illumination than sunlight or incandescent sources, due to metamerism, red surfaces being rendered particularly badly by typical phosphor-based cool-white LED’s. However, the color rendering properties of common fluorescent lamps are often inferior to what is now available in state-of-art white LED’s.
- Area light source: Single LED’s do not approximate a point source of light-giving a spherical light distribution, but rather a lambertian distribution. So LED’s are difficult to apply to uses needing a spherical light field, however different fields of light can be manipulated by the application of different optics or “lenses”. LED’s cannot provide divergence below a few degrees. In contrast, lasers can emit beams with divergences of 0.2 degrees or less.
- Electrical polarity: Unlike incandescent light bulbs, which illuminate regardless of the electrical polarity, LED’s will only light with correct electrical polarity. To automatically match source polarity to LED devices, rectifiers can be used.
- Blue hazard: There is a concern that blue LED’s and cool-white LED’s are now capable of exceeding safe limits of the so-called blue-light hazard as defined in eye safety specifications such as ANSI/IESNA RP-27.1–05: Recommended Practice for Photobiological Safety for Lamp and Lamp Systems.
- Blue pollution: Because cool-white LED’s with high colour temperature emit proportionally more blue light than conventional outdoor light sources such as high-pressure sodium vapor lamps, the strong wavelength dependence of Rayleigh scattering means that cool-white LED’s can cause more light pollution than other light sources. The International Dark-Sky Association discourages using white light sources with correlated color temperature above 3,000 K.
- Droop: The efficiency of LED’s tends to decrease as one increases current.
Now I don’t entirely understand each and every one of those points but the positives seem to out-weight the negatives to my reading.
I can definitely vouch for the higher cost though. It has cost us quite a bit to replace the down-lights to LED compatible ones, but now that we have, the cost of lighting in our house should be considerably lower, with a lower environmental impact too. Hopefully we can recoup our costs in just a few years by saving on our electricity bills.
I also found this page in my googling. Of all the facts listed, the carbon emissions comparison has shocked me most of all. Carbon Dioxide Emissions based upon 30 bulbs a year works out to be 4500 pounds/year for incandescent, 1051 pounds/year for compact fluorescent (CFL’s) and 451 pounds/year for LED’s. That’s just over 10% of the emissions of a traditional light bulb! I was concerned however about the environmental cost of making and disposing of LED lights. It’s the part of the story we are so often not told. We learned to look further into the manufacturing process when we were looking into flooring for our house. We considered bamboo and were just about to go ahead as it’s touted as this great environmental material, but creating flooring from it uses formaldehyde which means it’s not quite as green as it’s played out to be and making bamboo fabric uses a lot of chemicals to create longer fibres with which to weave. The whole truth shows bamboo as carrying a larger footprint than is apparent at first glance. So, I’ve had a bit of a look into LED manufacture and it’s coming up as not too shabby from a cursory glance. I found this article which states that LED’s come up best of the bunch but “the one area where LED’s lost was generating hazardous waste that must be taken to a landfill because LED lights include a component called a heat sink, a ribbed aluminum segment that is attached to the bottom of the LED bulbs. Aluminum heat sinks absorb and dissipate heat that’s generated by the bulb, preventing it from overheating. The process to mine, refine and process the aluminum in heat sinks is energy-intensive and creates several byproducts such as sulfuric acid that must be taken to a hazardous waste landfill.” Hopefully that component can be improved upon in the near future.
As far as things going on around here, there’s not much to report. I’m getting stuck into packing so we are down to the bare essentials (and not even that in the kitchen) which is getting very frustrating. We survived the 40 degree temperatures of yesterday and our house has cooled down to under 30 finally although it will still be a warm night. And we most definitely have 2 Dorking roosters. One of the 2 black ones, the one with the white feather collar as well as one of the other ones were shaping up in fine form yesterday. Right up on their legs, rearing right up and ruffs sticking out, they tried to scratch each other and pecking too. It was a right old barney in there. And we are looking forward to another day off tomorrow as we are off to an extended family Christmas gathering in Bendigo. Looking forward to getting the last bit of the chook pen and last veggie bed in on Sunday though.