Benefits of Light Emitting Plasma
- Energy Efficient - 115 lumens/watt source, 86 lumens/watt system
- 23,000 Directional Lumens
- Long Life - 50,000 hours
- Color Rendering up to 95 CRI
- Compact Emitting Area
- Forward Directional Output
- Dimmable to 20%
- Rapid Start
- Digital or Analog Controllability
|Source Efficacy (L/W)||120||115||100|
|Fixture Efficacy (L/W)||75||67||63|
|Color Rendering (CRI)||75-95||65-75||68|
|Lumen Density (L/mm^2)||1000||100||n/a|
|Dimmable & Controls||Yes||Yes||No|
How Light Emitting Plasma Works
LiFi light sources create light-emitting plasma by coupling radio-frequency (RF) energy into an electrodeless quartz bulb. The RF energy is created and amplified by an RF circuit that is driven by a Solid-State Power Amplifier. The following three steps outline the process of light generation in all LIFI systems:
Step 1: An RF circuit is established by connecting an RF power amplifier to a ceramic resonant cavity known as the puck. In the center of the puck is a sealed quartz bulb that contains materials consistent with metal-halide lamps.
Step 2: The puck, driven by the power amplifier, creates a standing wave confined within its walls. The electric field is strongest at the center of the bulb which ionizes the gasses inside the bulb (purple glow).
Step 3: The ionized gas in turn heats up and evaporates the metal halide materials which form a bright plasma column within the bulb (blue to bright white light). This plasma column is centered within the quartz envelope and radiates light very efficiently. In the back side of the bulb, a highly reflective powder is used to reflect nearly all of this light in the forward direction.
Frequently Asked Questions
What does LiFi® stand for?
LiFi is the brand name LUXIM uses to refer to Light Emitting Plasma™ technology - there are multiple product lines under the LiFi brand. LiFi represents the innovation in energy efficiency, reliability, and light quality that the LUXIM's technology brings to high illuminance lighting.
Is LiFi light source an LED (Light Emitting Diode)?
While LiFi is a category of solid-state lighting, it is not an LED. The fundamental difference is that LEDs use the solid-state device itself for light generation whereas LiFi light sources use a solid-state device to generate RF (radio frequency) energy to power a plasma light source. LiFi is able to combine the reliability of the solid-state technology with the high brightness and full spectrum of HID (high-intensity discharge) sources. This is the reason LiFi is called a solid-state high intensity light source.
The LiFi technology shares many of the same benefits with the LED technology but also has some basic differences in performance. The similarities that it shares with LEDs are the reliability of the solid-state electronics, the directionality of the light output, and the ability to dim instantaneously. The differences in performance are that LiFi has an order of magnitude higher lumen density (amount of light from one device), a full color spectrum with a CRI (color-rendering index) up to 94, and better source efficacy. LED luminaires work best in low and mid illuminance applications, LEP™ has superior performance in higher illuminance applications such as streetlights, parking lots, big box retail, distribution centers and factories.
How is LiFi different from traditional HID light sources?
LiFi differentiates itself from traditional HID light sources such as Metal Halide or High Pressure Sodium lamps in a number of ways. First, LiFi is powered using solid-state electronics that allow it to achieve very high reliability and have precise control over its operation. Also, unlike a traditional HID light source, the LiFi bulb does not need metal electrodes to drive power into the source and therefore has a more robust quartz vessel. LiFi is also able to produce a continuous spectrum due to its ability to use more efficient light generating materials. In addition, the light output from a LiFi source is directional, easily dimmable, turns on and re-strikes rapidly, and can operate in any orientation. All of these advantages translate into lower installation, maintenance and operating costs, higher energy efficiency, and an overall better lighting experience to the end user.
How is LiFi different from induction or other electrodeless light sources?
LiFi and other electrodeless lighting technologies like induction lamps share a common feature; they do not require electrodes to power the bulb and therefore can have a completely sealed, contaminant free and long lasting bulb. However, LiFi also is fundamentally different from other electrodeless technologies that have come before it.
Most electrodeless technologies use low pressure bulbs and typically use phosphors for secondary light generation. This has limitations in brightness, completeness of spectrum, and compactness - LiFi breaks away from these limitations. LiFi uses a dielectric resonant cavity to efficiently couple power from a solid state power amplifier into a high intensity discharge vessel unlike other electrodeless sources. Therefore, LiFi has higher lumen density, is more compact, more efficient and more colorful than other electrodeless light sources. Unlike induction, LiFi technology is a point source, which inherently emits all of the light that is generated in the forward direction in a lambertian pattern. There is less light trapped in the fixture and more light on the targeted surface.
How bright is a LiFi source? How many LiFi sources do you need in a typical street light?
The LiFi source has very high lumen density - in other words, a single source, only a few millimeters in size, can produce 23,000 lumens of brilliant white light. At this level of output, you will only need to use one light source per street light in most cases. This makes the mechanical and optical implementation of light fixtures much simpler and less expensive compared to using a large HID bulb or an array of multiple LEDs that is needed to match this level of luminous output.
Can LiFi sources scale to lower output? How about higher outputs?
While it is certainly possible for LiFi to scale to lower powers, the value proposition of the technology is greater at the higher output levels. For applications that require less than 5000 lumens, there already exist efficient, cost effective white light solutions such as LEDs and Ceramic Metal Halides. The advantages of LiFi are significant versus competing products in applications that require more than 10,000 lumens. LUXIM's future products will scale to higher output to enable even brighter and more energy efficient light fixtures.
What about thermal management?
Because there is only one LiFi source per fixture and because the source is more efficient at converting input power into light rather than heat, the thermal management of LiFi sources is straightforward. The LiFi source and driver are designed to operate without forced-air cooling in a normal operating environment of -40 to 45 C. All that is necessary is to mount the driver such that it makes good thermal contact with the light pole or a heatsink. The light source itself comes with a casing that also acts as a heatsink. LUXIM provides simple application and thermal design guidelines for adequately mounting the lamp onto the fixture.
How does LiFi light source's directionality and size impact light fixture performance?
LiFi inherently emits all of the light that is generated in the forward direction in a lambertian pattern from a small area much like a single LED does. This characteristic provides many advantages in light fixture performance. A smaller source requires smaller and cheaper optics (lenses and reflectors) to achieve the required level of glare cutoff and illumination pattern of luminaires. The directionality aspect improves the fixture efficiency - since all of the light is already directed towards the area that you are trying to illuminate (street or roadway), you do not have optical losses from light that goes in the wrong direction. This simple design advantage can improve the fixture efficiency in normal cases by 30% - in some inefficient fixtures that contain large sources, implementing a LiFi source can improve the fixture efficiency by two fold. In summary, the compact and directional source can lower the cost of manufacturing and installing a light fixture as well as the energy cost of operating it.
Can you dim LiFi sources?
LiFi is the only high-intensity light source that you can dim down to 20% of full brightness in a fraction of a second. This capability provides a huge opportunity to save on energy consumption and operating cost when combined with an occupancy or daylight sensor. For example, in lighting applications that sees minimal traffic, you can dim the light level in the room while unoccupied and instantly bring it back up to full brightness once the occupancy sensor detects movement. At the 20% brightness level, LiFi can have an even better life rating when operated at this level.
What is the source efficiency of LiFi when compared to other white light sources? How is source efficiency defined?
Source efficiency for white light sources such as metal halide or white LED is defined as the amount of light output (lumens) generated per watt of input power that is consumed by the source; therefore, efficiency is measured in Lumens/Watt. LiFi, with 115 Lumens/Watt at the source level, has one of the highest source efficiencies compared to other high output white light source (see below for a comparison chart). We should mention that there are HID sources like High-Pressure Sodium (HPS) lamps that match this level of source efficiency but its light quality is generally considered suboptimal due to its yellow-orange color.
|Ceramic Metal Halide||100||90||15,000|
|High Pressure Sodium||125||20||24,000|
|Low Pressure Sodium||180||<20||16,000|
What is the system or luminaire efficiency of a LiFi light fixture?
Luminaire efficiency is the overall efficiency of a light fixture and is the ultimate figure of merit that should be used in determining the energy consumption of the fixture. It takes into consideration power losses in each of the sub-systems that make up a luminaire. In addition to the source efficacy, a luminaire efficiency calculation also considers the ballast or driver efficiency, and optical or fixture efficiency. In this calculation, the utilization should be factored in due to power savings that result from the operating pattern of a light fixture - for instance a light fixture with an occupancy sensor will consume significantly less energy compared to a fixture that is always left on. The table below shows a comparison between a typical LiFi fixture and one that uses a pulse start MH lamp with electronic ballast.
|Fixture||Walkway Direct||Walkway Direct|
|Technology||PS Metal Halide||LiFi|
|Lamp Model||Solid-State High Intensity||LiFi-STA-40-01|
|Lamp Power (W)||400||200|
|Ballast/Driver Eff. (%)||93%||80%|
|AC/DC Eff. (%)||100%||94%|
|Tot. Power (W)||430||266|
|Initial Source Lumens||36800||23000|
|Mean Source Lumens||25208||19550|
|Fixture Eff. (%)||65%||90%|
|Mean Fixture Lumens||16385.2||17595|
|Daily Usage (hrs)||12||12|
|Annual KW-Hr (full power)||1884||1165|
|Annual KW-Hr (dim)||0||0|
|Cost per KW-Hr||$0.13||$0.13|
|Annual Operating Cost||$245||$151|
|Replacement Lumen Level||70%||70%|
|Replacement Cycle (hrs)||10500||50000+|
|# of Lamps/Year (4380 hrs)||0.42||0.09|
|Annual Maintenance Cost||$63||$22|
|Total Annual Cost||$307||$173|
|Annual Savings/Installation||for 10,000 units||$1,341,385|
How long can I expect a LiFi light source to last? Does orientation or operation cycle impact life time rating for LiFi lamps?
A LiFi-STA-41-01 source for general lighting applications is rated for 50,000 hours. At 50,000 hours, the lumen maintenance or the amount of light output as a percentage of initial output is above 65% on average. Lighting installers typically perform group re-lamping when the light output is 70% of original brightness; the 70% lumen maintenance occurs at 50,000 hours for a LiFi STA 41-01 source.
It is important to note that unlike typical HID light sources, LiFi sources do not need to be de-rated for the length of operating cycles or orientation of operation. In comparison, a typical 400W metal halide lamp can be expected to last 18,000 hours with a 50% survival rate. Its lifetime is de-rated by as much as 25% for bulb orientation and up to 50% for short operating cycles. LiFi sources do not have these types of limitations greatly enhancing their reliability and thus lowering maintenance costs.
What are the electrical requirements to install LiFi light fixtures?
The LiFi driver requires a DC power input of 28 volts and 9.5 amps. Therefore, the installation will require an AC to DC converter. If two sources are connected in close proximity, it is conceivable to use one AC-DC converter for both the sources. If two sources are placed further apart, it is recommended to use one AC-DC converter per source as there is less power dissipation over long distances in AC lines compared to DC.
You can either choose to run the lamp in basic mode or in digital mode. Basic mode allows only simple ON and OFF operations by controlling the input power to the lamp. No other electrical installation except supplying the recommended DC power is required in this mode. In basic mode, LiFi driver is also compatible to 0-10V analog dimmers that are commonplace in today's lighting control infrastructure. Digital mode allows you to communicate with the lamp to dynamically control the lamp's output, read the lamp settings, and perform diagnostics. To run the lamp in digital mode, you will need a serial connection to the individual lamp and a network infrastructure with a serial bus. See question 14 for the further details on the digital mode of operation.
Can you setup an intelligent network of centrally controlled LiFi light sources?
In digital mode, LiFi sources have a built-in capability to communicate with and be controlled via a serial bus. You can use the digital mode of the lamp to perform diagnostics, read faults, turn the lamp on and off, and dynamically dim its output. This feature gives the installer versatility in the way a lighting network is implemented as well as maintained. For instance, you can design an intelligent network of lamps that dim according to a day light sensor or signal for group maintenance when a certain percentage of them need replacement.
The lamp can also be made compliant with DALI and other lighting network specifications.
How quickly will LiFi sources turn on and how quickly can it re-strike?
LiFi sources will come up to full power typically within 30 seconds of turning it on. After shutting it off, you can re-strike it within 60 seconds. This is an order of magnitude better than conventional metal halide HID sources that require between 10-15 minutes to come to full brightness and up to 20 minutes to re-strike. Ability to turn on and re-strike instantaneously provides not only a better experience to the user but also enables occupancy sensing energy saving capabilities that would otherwise not be possible with conventional light sources.
Is there any EMI (Electro-Magnetic Interference) or safety concerns using LiFi?
There are two options for EMI management. First option will be a standalone LiFi unit with an EMI mesh that blocks any radiated emissions. The second option is to integrate the EMI mesh into the reflector used in the fixture. For those who choose the second option, LUXIM can provide design guidelines in order to ensure that the EMI is contained within the luminaire optics. In general, LiFi sources emit less electromagnetic radiation than an average cell phone. With proper design and installation, there is no RF safety or EMI concerns. LiFi products will be compliant with all the applicable CISPR and FCC standards for indoor and outdoor lighting.
What about user replacement and disposal of LiFi sources?
Both the LiFi source and the driver are designed to be easily replaced from within the light fixture. The LiFi source contains a very small amount of mercury compared with typical HID sources of equivalent power and the mercury vapor poses little risk of exposure under normal use and handling. You should contact the proper state environmental department for disposal regulations. LiFi electronics are also RoHS compliant and do not contain lead and other harmful toxic substances.
How can I get more information and get started on a LiFi evaluation kit?
You can get more information on LiFi and how to purchase an evaluation kit by contacting a Deco Lighting representative at email@example.com.