What does "Green" mean? The term "Green" to most people is anything that saves energy, cost or material. The push for going green started in the 1970's in the US and to this day is trying to move forward through the efforts of sustainable design companies and alternative energy companies.
Efficient Lighting Design Concepts
Lighting needs differ from space to space, mainly due to the purpose of the space. Lighting designers measure the amount of light a space needs in terms of footcandles. There are standards associated with spaces which vary depending on certain factors. Some classifications of spaces include: offices, manufacturing, assembly spaces, houses of worship, healthcare, and theaters.
There are several terms that need mentioned to create a basis for understanding efficient lighting design:
measured in Kelvin (K), refers to the exact shade of white light. The lower the color temperature, the warmer (more orange). The higher the color temperature, the cooler (more blue). Some examples are:
- Candlelight - 1850K
- Standard Incandescent - 2700K
- Most Warm White LEDs - 3000K
- Fluorescent - 3500K-5500K
- Daylight White (Noon, direct sun) - 5600K
- Daylight in Shadows - 7000K
- Overcast Daylight - 8000K-10000K
Color Rendering Index (CRI):
measure of the ability of a light source to reproduce the colors of various objects faithfully in comparison with an ideal or natural light source. The higher the CRI rating, the better color rendering of the light source. This scale ranges from 0 to 100.
measure of the perceived power of a light source. Luminous flux takes into account the varying sensitivity of the human eye to different wavelengths of light.
measure of how well a light source produces visible light. It is the ratio of luminous flux to power draw. (Lumens per watt) The highest attainable efficacy known to date is 683.002 lm/w which is green light at 555nm.
Emerging Technologies in Lighting
There are many types of lighting in use these days. For comparison, this article will talk about 5 different artificial light sources: incandescent, halogen, gas discharge, fluorescent, and LED.
Incandescent (tungsten incandescent) lighting is generally known to produce a very warm and natural feeling light. Thomas Edison improved and patented this lamp and technology in 1878. The color temperature is around 2700K with a high CRI, 90+. The downfall of incandescents is their short life and their high energy consumption. Along with high energy consumption comes high heat output. Approximately 2% of the energy used in an incandescent is emitted as light. A standard 60 watt incandescent lamp produces 14.2 lumens of light per watt. This 14.2 figure is the efficacy of the light source. It is easy to implement dimming of incandescents, and smooth dimmers that fade the light down to 0% are readily available.
Halogen lighting also produces a warm, clean light with a color temperature ranging from 2700K to 3200K. Halogen has a high CRI of 90+. The principle of halogen and incandescent tungsten lamps are the same, however the materials used in Halogen lighting are different. Halogen lighting sets up a reversible chemical reaction cycle with the tungsten evaporated from the filament. The halogen cycle keeps the bulb clean and the light output remaining almost constant throughout its life. The overall bulb envelope temperature must be higher than in conventional incandescent lamps for the reaction to work. Halogen is an improvement on the tungsten incandescent, but is still far from efficient as it retains an efficacy of 24 and is 3.5% efficient. Dimming halogens is similar to other incandescents, while keeping in mind that some halogens are low voltage and will require a low voltage dimmer.
Gas discharge lighting has been used for utility lighting in parking lots and exterior lighting, gymnasiums, roadways, manufacturing, etc. for years. This method of lighting is far more efficient than incandescent lighting as a gas discharge can produce between 65 and 150 lumens per watt. Although this makes them highly efficient (9.5%-21.9%), there is a reason to why no one is using them throughout their office building: the quality of light is very poor. The CRI of a sodium-vapor lamp is between 0 and 5. Only light with a CRI of 70 to 100 is considered suitable for living environments and offices.
Fluorescent lighting produces light in the 4200K to 6000K range with a CRI of 80 to 90. While it is an extremely flexible light source and provides decent direct and indirect lighting when used in the correct situations, fluorescent lighting does have its limitations. Fluorescent lighting is not feasible for controlled and focused needs. In addition, it doesn't have the ability to emulate the warmth of an incandescent. Fluorescents are also driven by ballasts which often cut-off around 30% which makes smooth dimming impossible. Still suited for many spaces, fluorescent fixtures can have an efficacy rating of 45-100 lumens per watt making some of the best fluorescent models 12-15% efficient.
LED lighting (White phosphorus LEDs) produces light anywhere from 2700K to 7000K depending on your needs. Finding a good LED lamp or fixture is a challenge, so it's important to know what you're looking for. See our LED section below to learn what to look for in a well-designed LED lamp. LEDs can have a range of CRI ratings from 70 through 90+. Some LED retrofits are even receiving an efficacy of 70+. While that number isn't enough to jump in front of other lighting technologies, think about the following reasons why LED lighting can look great and save a lot of money in as little as 2 years. LEDs focus light where you want it: they don't have to spill light everywhere like fluorescent products do. There are several types of LED lamps and fixtures that all have variable lensing, fixture profiles, and color temperatures. Best of all, good LEDs should be dimmable from close to 0% to 100%. Currently, most LED retrofits are about 20% efficient and are projected to reach close to 40% efficiency as the technology matures.
Occupancy sensing uses sensors in a room to recognize when someone is in a room, and turns the light on in the space. Once the sensor detects that the room is unoccupied for a length of time it turns the light back off. Unlike occupancy sensing, vacancy sensing relies on the user to switch the lighting on when entering a space. This prevents accidental activation of the lighting in spaces when someone walks past a sensor. It also allows the user to turn off the light immediately when leaving a space, maximizing the energy savings. Vacancy sensing continues to use a sensor to determine if the lighting was inadvertently left on, and will still time out and turn off the lights after the room in unoccupied. Well-designed vacancy sensing systems include a processor that is networked to the motion sensors, allowing for the computer to monitor motion in the room and provide more complex control. As estimated by the U.S. Environmental Protection Agency, average saving potential ranges from 40-80% as compared to a building without a vacancy sensing system.
Daylighting systems offer tremendous potential for reducing the energy consumption from lighting, but their usage has been inhibited by high costs and less than perfect performance. While the components to daylighting systems are not expensive, it is integral that the design, implementation, and programming is well thought through. Maximum savings is achieved when the architecture of the building is designed to allow in maximum natural light.
Daylighting systems use photocell sensors to monitor the amount of natural light in a space and adjust the amount of artificial light so the space is lit appropriately. These photocell sensors work best in conjunction with automated window shades which have the ability to block natural light when needed. By using these two technologies you can see an average annual energy savings of 24% compared with manual switching and standard blinds.
Commercial buildings in the U.S. house more than 64 billion sq. ft. of lit floor space. Most of these buildings are lit by fluorescent lighting systems. Estimates show between 30% and 50% of the space in these buildings has access to daylight either through windows or skylights. The installation of technologies designed to take advantage of available daylight would be an appropriate energy-saving strategy that could potentially turn off millions of light fixtures for some portion of each day. Low cost daylight harvesting systems should meet the following goals:
- install easily for a retrofit, or incorporate simply into existing fixtures or daylighting related products
- be inexpensive to design and manufacture
- achieve high energy savings
- not annoy occupants
Automatic blinds systems use a device that opens window blinds once per day, either overnight or during lunch time. The blind-opening mechanism is a simple mini-motor that is programmed to activate during specific times of the day. Some advantages of this device include:
- complementary operation with other daylight harvesting systems already in use
- a design that makes use of the daylight that would have been lost
- a simple and inexpensive add-on
- easy installation and automatic operation
- manual operation possible at any time
A study was conducted by the Lighting Research Center recently that tested several methods of daylighting in an office space in Albany, New York. This study showed that a "Perfect dimming" system, that is a dimming system that is smooth and unnoticeable which includes photocell sensors, along with automatic blinds can save 32% on energy consumption over an annual time period. This 32% figure is compared to a manually switched lighting system and manual blinds.
Maximum savings and convenience comes with a combination of these systems, controlled by an intelligent control system capable of making decisions based on time-of-day, current conditions, occupancy/vacancy, etc. Some control systems allow local override in each classroom or office space, using available daylight supplemented with artificial lighting to maintain preset lighting levels, and automated blinds which take into account vacancy to minimize heat/cooling loss and increase security. The control system may also provide a graphical interface to provide override control to facility personnel, and provide an automatic or manually triggered building sweep to ensure all lights are off and all blinds are closed when the building is closed for the night.
An intelligent control system should also allow different schedules to be set up for different uses of the building. For example, an office building may want to keep hallway lights on during the workday, but provide occupancy sensing for those spaces during off hours or weekends. The possibilities are endless with the right combination of sensors and control system.
The Good, the Bad, and the Ugly
Poor quality LED lighting products have flooded the market, leading to many misconceptions of how LED lighting should be used. Our goal is to clear up these misconceptions and guide you on how to identify the LED products which will correctly meet your needs.
Color Rendering Index
CRI, or Color Rendering Index, is one of the most important specs to look for when looking for a good LED source. CRI is the ability for a light source to show all of the colors of an object. The higher the rating, the better. Remember, anything from 70-100 is the ideal CRI rating for offices, gathering spaces, or homes. We always try to spec LEDs that are around 90 and above.
Measured in degrees Kelvin (K), color temperature is the exact color of light which the eye adjusts to as being white after a length of time in a space. White light around 2700K - 3500K is classified as warm white, and white light around 4800K - 6000K is classified as cool white. The warm/cool terminology is not standardized, so it is important to read the exact specifications for each lamp. Higher color temperatures tend to make items look cooler and washed out. Lighting food with 5000K or higher light tends to make the food look more bland and less colorful. This is why in film and photography, food is often lit with a warm light source which brings out the color and makes the food look more appetizing. It is important to watch both the color temperature and CRI of LEDs, though, as a warmer color temperature often doesn't mean a higher CRI.
Mixing Colors to create White
Mixing colors to create a variable white light has become the new method to add or subtract wavelengths of light from lighting objects. While currently appealing to the museum, display, architainment and theatre industries, there are a lot of great aspects to using this method of LED lighting. In the case of using an RGBA (Red, Green, Blue, Amber) LED source, a warmer white light (3300K) can be achieved while also being able to create a cool white light by adding more blue to the mix. Because of the nature of having multiple sources mix to white light, the efficacy of color mixing fixtures is about 30% greater than that of a warm white phosphor LED. There is potential for better color rendering in a multiple colored LED source as well.
Now that we've explained multi-colored LED mixing, everyone is thinking about DJ lighting. Let's separate the good RGB, RGBA, RGBW fixtures from the rest of the field. Good color mixing fixtures should never appear to have multiple light sources! We stress that because proper lensing should always make a beam of light uniform and eliminate rainbow edges on shadows. When speaking about architectural color mixing fixtures, it should never be possible to see individual LEDs or spots of color on the lensing of the fixture. If the multi-colored sources are visible on the fixture, they will be visible on objects. Just because all white light has the rainbow of colors in it, doesn't mean that we should be fine with seeing it.
Multi-Source White LED Lamps
This brings us to multi-source white LED lighting. For most retrofitting, it is possible to avoid buying lamps that contain several LED chips to create adequate lighting. Any time multiple chips are used in a lamp there will be multiple shadows created. Because we have lived with incandescent lighting for so long we have become accustomed to seeing single shadows. Another point to note when looking at manufacturers is that many overseas LED technology companies are producing LED products that continue to add more LED chips to the lamp and increasing the output without increasing the heatsink. Most LEDs are at least 20% efficient. This means that about 20% of the energy being used is converted to light and about 80% is being converted to heat. Without a proper heatsink and proper heat dispersion, the electronics and LED components will burn up and the LED lamp will not make it to its rated lifetime. The warmer an LED runs the quicker its brightness will fade.
Directionality of LED Sources
LEDs are also more efficient than other sources because of their inherent directional qualities. LEDs have been designed to have native lensing, often narrow, to allow for optimal light output and optional secondary lensing to spread the beam angle of the light. All other light sources create light in all directions and rely on reflectors to bounce the light towards the intended direction.
Dimming of LEDs
LED components can not be dimmed in the conventional sense. They are designed to operate only at a specific voltage and current. Pushing less current through will only make them run less efficiently, and push more through will significantly shorten their life. To give the appearance of dimming in an LED driver circuitry uses Pulse Width Modulation (PWM) to turn the LED on and off very quickly. This happens so quickly that the human eye sees it as dimming up and down and the ratio of on time to off time are changed. The better the LED driver circuitry, the faster the PWM rate. A very fast PWM rate is essential if something lit by an LED source will be photographed or video recorded. A fixture with a slow rate will appear to flicker or strobe on video, and may even appear to be turned off in part of the image when photographed.
LED retrofit lamps are available which are dimmable. These sense the changes in incoming voltage and use PWM to "dim" the LED components. Different lamps respond differently to each type of dimmer. Many require a very specific dimmer to work correctly. Spire can advise on the correct dimmer for each type fo lamp. The less expense lamps will cut out at 5% or 10% on any dimmer, and some may never turn fully off.
Dimming greatly affects the lifetime of LEDs. As you drive LEDs at full you are using them at their rated lifetime (most times this is 35,000 to 50,000 hours until the LED fixture is 70% as bright as it was when it was new). Due to PWM, dimming LEDs means they are not on 100% of the time. Not being on 100% also means the heat sink has more time to get rid of the heat generated, exponentially reducing the temperature of the diode. Therefore, by running an LED lamp at 90% you could potentially double the lifespan of the components.
Let's set up a scenario. For example: an office building that uses 100 - 60 watt incandescent lamps, could retrofit their 100 fixtures and replace them with 12.5 watt dimmable LEDs. This would yield an energy usage of 1.25 kW/hrs per hour that the lights were on. Prior to the retrofit, the lighting was using 6 kW/hrs per hour. Let's assume that the lighting was on for 10 hours a day 260 days a year (Monday through Friday). Prior to the retrofit the annual electrical usage was 15,600 kW/hrs. Using the national average electrical cost of 9.83 cents per kW/hr, the office would have cost $1,533.48 to light the office. Now with the LEDs, the annual electrical usage was 3,250 kW/hrs. The annual cost to use the LEDs would equal $319.48. At $20 per lamp, the office's $2,000 investment would pay off in 20 months. Also remember, if you were using the cheapest incandescent 60 watt light bulb that was rated for 300 hours, a maintenance employee would have changed all of the light bulbs in the office 8 times in that year. By the way, your new LEDs would last 19.23 years! Follow this link for a calculator which can calculate the savings for your particular situation.
Now let's add more to the above scenario. If you were to add a daylighting system with dimming and automated blinds to this office, you should expect to see an additional cost savings of 32% annually. Now maybe the office isn't big enough to justify the expense of a system like this, but as the project size scales up, the control system and design fees stay about the same.
Rebates and Incentives
Currently there are rebates for LED lighting and efficient design solutions that are funded through energy providers, state and federal governments. We will work with you and your energy provider to complete all paperwork and to get you the highest rebate possible. Currently there are several electric providers offering anywhere from 25-50% rebate on LED technology. Because rebates expire once a predetermined amount of funding runs out, programs come and go monthly.
How We Can Help
If you made it this far in the article, you may be wondering what to do next. We can help design your project and walk you through everything until you are completely satisfied. We provide in-depth design services and thorough installation services. We know that most people are not lighting designers, but want to end up with an efficient and great looking project that fits their budget and their facility. That is why we strive to work with clients closely to make sure that they get the design and functionality needed for their space. Call us to talk about your project and your ideas.