May 9, 2016 admin

Why LED

 

 

LED technology helps to reduce energy consumption significantly. Depending on the light sources compared to, by 50…90%. Since lighting is in commercial buildings a major energy consumer, focus must be on lighting to reduce the energy cost. Also, as it was put, the “social licence” to waste energy is revoked.

Increasing tenant requirements for better light quality, good corporate citizenship, and future proofing of the tenancy: creating a productive, efficient & healthy building

LED technology has several key advantages over traditional light sources. While the technology is available since the 1960s, cost and output as well as limited colours  had been prohibitive in most lighting applications. Now this still evolving technology is state-of-the art.

 

Key Advantages:

  • Efficacy: LEDs emit more visible light per Watt than conventional light sources. Compared to fluorescent light bulbs or tubes less energy is wasted on UV light components.
  • Colour: LEDs can emit light of an intended colour without using any filters. This is more efficient and can lower initial costs. Also the spectrum is smaller, i.e. focussed on the required wave length. This is why LEDs often are brighter to the human eye than a lux meter (which also measures unwanted wave lengths) would suggest.
  • Lifetime: LEDs have typically 35,000 to 50,000 hours of useful life, usually defined as >70% of initial output. Time to complete failure will be longer. Typically Fluorescent tubes are rated at 10,000 to 15,000 hours, incandescent light bulbs are rated at 1,000 to 2,000 hours. Longer lifespan reduces maintenance costs.Usually it is not the LED itself that fails, it is a driver component. It is essential to choose quality devices from reputable suppliers.
  • Cycling: LEDs suitable for frequent on-off cycling, unlike fluorescent lamps that fail faster when cycled, or HID lamps that require a long pause before restarting. This makes LEDs ideal to work in conjunction with presence sensors.
  • Light quality: Colour rendering properties of state-of-the-art white LEDs are superior to common fluorescent lamps. No unwanted wave lengths, e.g. UV are emitted.
  • 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.
  • Waste heat: In contrast to most light sources, LEDs radiate very little heat in the form of Infra Red light that can cause damage to sensitive objects or fabrics.
  • Slow failure: LEDs mostly fail by dimming over time, rather than the abrupt failure of incandescent and fluorescent bulbs and tubes, which are also fragile.
  • Shock resistance: LEDs, being solid-state components, are resistant to external shock, unlike fluorescent lamps.
  • Low temperature applications, e.g. cool rooms: LEDs start easily in in low temperatures, where fluorescent lights are required to stay permanently on due to re-start difficulties.
  • On/Off time: LEDs light up very quickly. A typical LED will achieve full brightness in a millisecond.
  • Dimming: LEDs can very easily be dimmed either by pulse-width modulation or lowering the forward current. It is important however to choose a quality dimmable driver (whether in-build or external) to avoid flicker.
  • Size: LEDs can be very small (smaller than 2 mm2) and are easily populated onto printed circuit boards, making them ideal for architectural design applications.
  • No mercury: save to recycle and non-hazardous in case of damage

 

Disadvantages

  • Initial cost: LEDs are currently still more expensive, price per lumen, on an initial capital cost basis, than most conventional lighting technologies. This is off-set by energy savings.
  • Temperature dependence: An adequate heat sink is needed to maintain long life. When selecting LEDs it is essential to ensure quality design.
  • Voltage and current sensitivity: LEDs must be supplied with the voltage above the threshold and a current below the rating. Quality current-regulated power supplies are essential.

 

Safety and health

  • Safety: The vast majority of devices containing LEDs are “safe under all conditions of normal use”, and so are classified as “Class 1 LED product”. Only a few extremely bright speciality LEDs are classified as “Class 2“, same as lasers.
  • Blue hazard and Blue pollution: With increased output cool-white LEDs are now capable of exceeding safe limits of the so-called blue-light hazard as defined in eye safety specifications. Also cool-white LEDs used outside there intended use can cause more light pollution than other light sources. Proper selection of colour temperatures and choosing lamps with good colour rendering is essential. Please note that measurement of the colour rendering index favouring fluorescent lamps and disadvantaging LEDs.
  • UV light: contrary to fluorescent lights, LED do not emit significant ultra violet light.
  • Hazardous materials: LEDs have a huge advantage over fluorescent lamps that they do not contain mercury. LEDs do not contain any significant amounts of hazardous materials. Some colours require extremely small amounts of lead and arsenic. An US study published in 2011 states: “According to federal standards, LEDs are not hazardous except for low-intensity red LEDs, which leached Pb [lead] at levels exceeding regulatory limits.