There’s no doubt that light-emitting diodes – more commonly known as LEDs – are the future of lighting. They have come to represent an extremely ‘green’ lighting solution that requires less electrical consumption than traditional bulb (or lamp)-based systems to deliver an equivalent power output. They also offer reduced CO2 emissions which should receive a ‘thumbs up’ from those Boards of Directors currently striving for a reduced carbon footprint.
In essence, an LED is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction of what’s known as the P-N Junction (itself formed by combining P-type and N-type semiconductors in very close contact). The end effect is a form of electroluminescence (whereupon a material emits light in response to the stimulus of an electrical current having been passed through it).
Of itself, an LED is a small, extended light source with extra optics added to the chip that makes it emit a complex radiation pattern. The colour of the emitted light depends on the composition and condition of the semi-conducting material used, and can either be infrared, visible or near-ultraviolet.
One of the key advantages of LED-based lighting is its high efficiency, as measured by the light output per unit power of input. In 2002, the company Lumileds made 5 Watt (W) LEDs available with efficacies (or efficiencies) of 18-22 lumens per Watt. In comparison, a conventional 60-100 W incandescent lamp produces around 15 lumens per Watt.
Then, in September 2003, a new type of blue LED was demonstrated by Cree Incorporated and offered 24 MW at 20 mA. This produced a commercially packaged white light giving 65 lumens per Watt at 20 mA – thereby becoming the brightest white LED commercially available at the time. This was over four times more efficient than standard incandescent light sources.
In 2006, the company demonstrated a prototype with a record white LED efficacy of 131 lumens per Watt at 20 mA. Also, Seoul Semiconductor has plans for 135 lumens per Watt by the end of this year, and 145 lumens per Watt by 2008 (which would be approaching an order of magnitude improvement over standard incandescent sources and better even than standard fluorescents).
The Nichia Corporation has developed a white light LED with efficacies of 150 lumens per Watt at a forward current of 20 mA.
From traditional to modern
There are three main reasons why end users are now moving from traditional lamp-based CCTV lighting systems to ‘greener’, LED-rich project solutions:
- Technical advances in LED technology now make LED illumination possible
- LED illuminators provide increased securityon site when in operation
- The illuminators also deliver huge cost savings on the bottom line
Before examining why LEDs are the future of CCTV lighting, though, it’s first important to highlight the advantages and disadvantages of the different forms of CCTV lighting systems already available (including incandescent and fluorescent lamps, and the HID models).
For CCTV purposes, incandescent lamps are generally expensive to run (typically 200 W or 500 W) and expensive to maintain (with anything up to three lamp changes per year). End users are increasingly moving away from using halogen-based lighting products in favour of longer-life LEDs.
Incandescent lamps were the first to be developed and are highly inefficient, wasting about 90% of input energy as heat. Their heat output is such that they are extremely hot to touch, and can heat surrounding objects in close proximity.
Halogen lamps offer a minimal increase in efficiency and still waste as much as 85% of input energy as heat. They are smaller – and of a higher pressure – than their incandescent cousins, causing them to have an extremely hot surface that’s hazardous to the touch. Bringing the lamps into contact with cold surfaces may cause lamp failure.
The use of fluorescent lamps for surveillance purposes is limited due to the perceived ‘beating’ effect when used with a CCTV camera. They are generally low power and designed mainly for internal fitting.
As they have a large diffused source the light output is difficult to focus and control.
Fluorescent lamps are much more efficient than incandescent models, operating at approximately 40% efficiency. Only 60% of the input energy is wasted as heat, though, so fluorescent lamps run much cooler than incandescent lamps and can provide equivalent power from much lower electrical input. For this reason – and due to the fact that fluorescent lamps tend to last 10-20 times as long as their incandescent equivalents – they are commonly used in the homes as long-life light sources.
All that said, fluorescent lamps produce a flicker imperceptible to the human eye but visible to cameras as a ‘beat’ effect, making fluorescent illumination unsuitable for video surveillance. Fluorescent lamps also contain the hazardous material mercury.
High-intensity discharge, or HID lamps could be used with CCTV. They are efficient, provide good colour rendition and are long life (lasting for anything up to 12,000 hours). However, they suffer from a slow start (two to three minutes) and cannot be turned on immediately after being turned off.
HID lamps are 60-80% efficient and, in comparison with incandescent and fluorescent sources, provide much more light from a smaller package. HID forms include low pressure sodium (unsuitable for CCTV due to its yellow tinge), metal halide and high pressure sodium (which is most acceptable, but produces worse colour rendition than metal halide). Metal halide lamps provide a natural, cool, clear white light with good colour discrimination. HID lamps are commonly used for street lighting and in car headlights.
LEDs: efficiency and reliability
LEDs are extremely efficient light sources and offer unbeatable reliability into the bargain – including the lowest possible running costs (less than 100 W for the highest power units) with the longest operating life (of up to ten years) (see table 1, above).
They are a relatively new development in lighting, but their usage is expanding rapidly on the back of clear technical advantages. LEDs can be slightly more expensive to purchase, but provide extremely long life – up to 100,000 hours, in fact.
In comparison, fluorescent lamps typically last 10,000 hours and incandescent lamps just 1,000. LED efficiency is typically 80-90%, with the greatest efficiency coming from LEDs producing red light. The advantages of LEDs include extremely low electrical consumption, low operating temperatures and the continuity of colour through the operating life of the LED.
Unlike traditional lamps, LEDs are also highly durable, insensitive to vibration and their hard casing makes them difficult to break. They are also capable of emitting light at a given wavelength without the need for a filter, and are ‘quick start’ devices. Power and thermal management are important to ensure LEDs deliver the expected performance. ‘Through hole’ LEDs are expensive to mount to PCBs and, generally speaking, aren’t as robust as surface mount technology (SMT). SMT LEDs offer better thermal management, allowing the LEDs to be driven harder without compromising performance.
Higher levels of site security
Well-engineered, well-powered and, most importantly, well-controlled LED lighting allows for higher levels of security on site than traditional lamp-based illuminators. LED lighting should provide in excess of 10 years of hassle and maintenance-free illumination. LED lights simply should not fail, and do not need regular replacement.
Older lamp technologies – whether halogen, metal halide or sodium – all require lamp changes, either when the lamp has blown or at regular service intervals. Consider a site such as a prison or military barracks. There might be 100 cameras monitoring the perimeter, each fitted with an infrared or white light illuminator. If these are lamp illuminators that is 100 lamps which require regular servicing and replacement with the use of a cherry picker and dedicated maintenance staff. Each time a lamp ‘blows’, rather than paying for a call out charge and the cost of a cherry picker (in addition to the cost of a replacement lamp), it’s common to wait until a few lamps have ‘blown’ in order to service multiple lamps in one visit. Obviously, this leaves some of the site without adequate CCTV lighting and, therefore, prone to attack by criminals and vandals alike.
LEDs provide high security, low risk lighting. LED illumination offers more security and ‘peace of mind’ to end users, secure in the knowledge that whenever a crime occurs, the CCTV system will be fully operational.
Delivering huge cost savings
As previously stated, LEDs are far more efficient than lamp-based illuminators and, consequently, require less electrical energy to generate the same light output. Once installed, LEDs also require zero maintenance. Compared with lamps, they save costs on replacement parts, equipment hire (specifically cherry pickers) and labour.
Compare the operational costs of a single LED illuminator with a bulb-based illuminator (see table 2 on page 33).
From a combination of electrical savings, and reduced costs for maintenance and replacement parts, a single LED illuminator can provide annual savings of up to GB pound 368 compared to a 500 W illuminator. Now, consider the cost savings to be made on larger sites using multiple cameras and multiple CCTV illuminators (table 3, above).
The cost savings for large systems are enormous. Changing 100 units of 500 W lamps to 100 units of high efficiency LEDs can save end users up to GB pound 36,800 per year (and this is a figure based on minimum costs for labour and equipment hire to replace lamps). When you consider that most installed CCTV systems have a projected operational life-cycle of ten years, this amounts to a total ten-year saving of GB pound 368,000 for switching a 100 light system to high efficiency LEDs.
Consider the facts… A maximum saving on one illuminator of GB pound 368 per year. Over ten years that represents a total saving of GB pound 3,680. A maximum saving on 100 illuminators of GB pound 36,800 per year is equal to GB pound 368,000 over ten years. In addition to the cost savings, the reduced electrical consumption of LED illuminators delivers a lower carbon footprint (with resulting tax benefits for end users).
The future of CCTV lighting is green. New LEDs provide all the power and distance of lamp-based illuminators with the advantages of delivering a more secure site and massive savings in operating and maintenance costs.
Next time you need CCTV lighting, do the planet and your pocket a massive favour – go green. It’s certainly a win-win scenario.