Pushing the move towards LED lighting
PhotonStar as a company is only 18 months old, but is rapidly growing a business in LED-based lighting. Ken Sharpe finds out why LEDs are proving so successful for the company.
The phasing out of the popular tungsten-filament incandescent light bulbs in the UK is fast approaching, and there are ever-growing concerns about the compact fluorescent lamps that were their intended replacement. However, the development of lighting based light-emitting diodes is proceeding apace, and it is looking increasingly likely that they will become the natural successor to incandescent lamps for general lighting applications. LED technology is particular suited to downlighting, making it highly competitive to the widely used halogen downlights.
That is the view of James Mckenzie, CEO of PhotonStar, a company specialising in LED technology for lighting and which first hit the market at the Arc lighting exhibition in February 2008. Since then the company’s business has grown at 25% a month with at least 10 projects completed each month by working with, designers, specifiers, consultants and installation partners. The largest project of over 350 completed to date is a 4-storey office block in London.
James Mckenzie and PhotonStar’s chief technology officer Dr Majd Zoorob used to design LED chips for applications such as backlit monitors for computers and television screens. When the technology was sold to Taiwan for mass manufacture, the two men saw an opportunity for LED in general lighting and how they could be used properly. PhotonStar was set up and operated from facilities at the University of Southampton during a period of development work. The company has 15 patents for its products.
James Mckenzie has very clear views on the benefits of LED technology for lighting.
Compared with incandescent lamps, halogen lamps and CFLs, they save considerable amounts of energy.
First, they use 80% less energy than incandescent and halogen lamps and 40% less than CFL low-energy fittings.
Secondly, LEDs do not present any tricky environmental issues at the end of their life. In contrast, CFLs contain 2 to 4 mg of mercury, which necessitates special methods of disposal.
Thirdly, LEDs now produce high-quality light with the aid of phosphors. Lamps switch on instantly and can readily be dimmed, which leads to more efficient operation — i.e. increased efficacy. The company has developed the SmartWhite range of LED luminaires whose colour temperature can also be varied to mimic the change in daylight colour temperature with high colour quality during the day and provide more versatility for mood and scene setting.
Finally, and the benefit that is most often the deciding factor for LEDs, according to James McKenzie, is their long life and zero maintenance requirements. Indeed, it is when major maintenance of an existing lighting installation is due that the economic case for converting to LEDs is at its strongest.
So significant are the energy savings to be gained by changing from light sources such as halogen to LEDs that interest-free loans available through the Carbon Trust can immediately lead to positive cash flow.
The detailed arithmetic goes like this.
Upgrading a corridor lit by a hundred 35 W GU10 halogen lamps to the PhotonStar CSS 7 W lamp reduces the installed load from 3.5 kW to 700 W. If the lamps operate for 18 hours a day, seven days a week the 27 MWh a year used by the halogen lamps would be reduced to just 5.3 MWh a year whilst still providing equivalent amounts of light.
The reduction in electricity cost, based on 12 p/kWh, is £2600 a year — exceeding the loan repayments by over £660 a year.
There is also an additional significant maintenance saving, since the tungsten halogen lamps would need replacing 25 times during the life of an LED lamp — taken at 50 000 h, or nearly six years of continuous operation. This is the point when the user may notice the light is about 30% dimmer; failure is not catastrophic like conventional lamps. The cost of replacement halogen lamps and their installation would come up at intervals of less than 16 weeks.
LEDs already have significant costs benefits over halogen lamps, and are gaining ground all the time with James Mckenzie suggesting that their efficiency is improving by 15% every six to nine months.
With that pace of improvement in efficiency, LED light sources will soon catch up with the most efficient types of fluorescent lighting. James Mckenzie explains, ‘T5 and T8 fluorescent lighting is more efficient than LEDs at present — with an efficacy of 70 lumens per circuit watt from the fitting. However, it will probably only be a short time before LEDs exceed this efficiency.’
Despite the lower efficiency of LEDs compared with T5 and T8 fluorescent light sources, the case for using LEDs can be strongly influenced by their lower maintenance costs resulting from the very long lamp life — especially for refurbishment, where the cost of maintaining the existing installation can immediately be traded off against the cost of a new installation based on LEDs. James Mckenzie argues, ‘Installing LED luminaires makes sense at any time, especially when lighting usage is heavy.’
The effective life of an LED light source depends heavily on getting heat away from the diode junction. If the fitting and the heat sink are not designed as an entity to remove heat effectively, the temperature of the diode junction will be high, and the life of the LED could be very short indeed. James Mckenzie is concerned that there are many LED luminaires available on the market that do not dissipate heat adequately and will therefore have lives that are very short.
The rapid growth rate of PhotonStar demonstrates how ready the market is to accept LED lighting. But as James Mckenzie points out, what PhotonStar is achieving is a very small part indeed of the world potential. Since the introduction of the first ‘practical’ light bulb little more than a hundred years ago in 1880, he says that electric lighting has grown to such an extent that there are now about 19 billion light sockets in the world using around 13 billion lamps a year — the majority going into landfill
