Avoid the expense for a whole new LED streetlight, forget about storage issues or disposing of the old one you take down.
Why Retrofit?
Designers reached a thermal ceiling with convection cooling inside a Cobrahead housing. Rather than find a thermal solution, they moved away from retrofitting. LED streetlights now typically have a dedicated heat exchanger as the exterior housing. This makes sense technically, but expense for the design and the new housing, and disposing of the old, is passed along to the end user. What is the best environmental choice?
A retrofit program addresses several issues: 1) it retains a familiar appearance; 2) it saves the cost of a new LED streetlight housing; and 3) by using the Cobrahead housing, there is no storage or disposal issue. Die-cast Cobrahead housings are proven and may last for decades.
Suppliers of complete new LED streetlights might argue that old Cobraheads are cheap; there's little to save. However, until they price their housing for that same amount, you will save hundreds of dollars per light when acquiring only the LED components.
See more Details Here.
Technology
LED luminaires need all the lumens they can get, and that equates to heat. The proprietary thermal management system used in this Cobrahead retrofit product allows maximum luminous output and coolest LED operation. This technique is not simply a convection heat exchanger sealed inside the enclosure. Instead, in addition to heat dissipation at the bottom side, it makes a heat exchanger from the entire die-cast outer surface.
This cooling method allows the power necessary for an optical output to really replace 200 watt or higher HPS streetlights, and last for more than 50,000 hours.
Sunday, September 19, 2010
Thursday, September 9, 2010
Solid State Lighting and the ESCO
What is an ESCO?
An Energy Service COmpany is "...a business that develops, installs, and arranges financing for projects designed to improve the energy efficiency and maintenance costs for facilities..." That snippet is from NAESCO (National Association of Energy Service Companies).
An ESCO may work with all aspects of energy savings (e.g. HVAC, lighting, insulation, energy efficient building materials, indoor and outdoor, etc.) and is usually compensated up front with a portion of the long term savings. This process is also known as an Energy Performance Contract.
This blog offers a forum to discuss how an ESCO and end user (Owner) can partner and win. LED lighting payback is mostly from maintenance savings due to its very long life, and LEDs usually save over 40% in energy when matching foot-candles of the lighting they replace. The LED product life increase of 4x - 5x combined with such energy savings makes it a clear winner and should be considered whenever an LED offering is available.
This ROI Calculator, one of the best in the Industry, is available with costs AND interest on the money borrowed, can quickly determine justification. It requires product cost and power consumption figures. First, compare photometric layouts for the current lighting and for the proposed LED to determine suitable LED replacement wattage or lumens. When you have the figures, use this straight line ROI payback calculator for conservative estimates.
An ESCO has the advantage of huge, dedicated labor resources, and will finish a large project in days rather than months or years. Large projects are a natural mission for the ESCO; a college may have hundreds of street-parking-courtyard lights, and a city may have thousands. When resident labor forces take on projects of this magnitude, their pre-existing priorities can make it seem they might never finish.
The calculated savings can't begin until the lighting project goes to work for you, and the ESCO makes that happen quickly.
Here's an example project with
Johnson Controls and University of Central Oklahoma.
Here - NAESCO has a form to help find an ESCO provider. You merely provide the location and the size of project.
Visit this Forum for Facility Managers to network services.
Also see Energy Star's Introduction to Energy Performance Contracting
There will be much more on this topic and we invite comment.
An Energy Service COmpany is "...a business that develops, installs, and arranges financing for projects designed to improve the energy efficiency and maintenance costs for facilities..." That snippet is from NAESCO (National Association of Energy Service Companies).
An ESCO may work with all aspects of energy savings (e.g. HVAC, lighting, insulation, energy efficient building materials, indoor and outdoor, etc.) and is usually compensated up front with a portion of the long term savings. This process is also known as an Energy Performance Contract.
This blog offers a forum to discuss how an ESCO and end user (Owner) can partner and win. LED lighting payback is mostly from maintenance savings due to its very long life, and LEDs usually save over 40% in energy when matching foot-candles of the lighting they replace. The LED product life increase of 4x - 5x combined with such energy savings makes it a clear winner and should be considered whenever an LED offering is available.
This ROI Calculator, one of the best in the Industry, is available with costs AND interest on the money borrowed, can quickly determine justification. It requires product cost and power consumption figures. First, compare photometric layouts for the current lighting and for the proposed LED to determine suitable LED replacement wattage or lumens. When you have the figures, use this straight line ROI payback calculator for conservative estimates.
An ESCO has the advantage of huge, dedicated labor resources, and will finish a large project in days rather than months or years. Large projects are a natural mission for the ESCO; a college may have hundreds of street-parking-courtyard lights, and a city may have thousands. When resident labor forces take on projects of this magnitude, their pre-existing priorities can make it seem they might never finish.
The calculated savings can't begin until the lighting project goes to work for you, and the ESCO makes that happen quickly.
Here's an example project with
Johnson Controls and University of Central Oklahoma.
Here - NAESCO has a form to help find an ESCO provider. You merely provide the location and the size of project.
Visit this Forum for Facility Managers to network services.
Also see Energy Star's Introduction to Energy Performance Contracting
There will be much more on this topic and we invite comment.
Thursday, September 4, 2008
Thermal Issues with Outdoor SSL
Most of us know that solid state lighting design requires effective thermal management. Thermal discussion was the #1 hold up in the early days of LED traffic signals. In fact, for the first 2 years after ITE and NEMA became involved with LED Traffic Signal Standards, they conducted studies of solar heating effects in various geographical locations. But that's history, and obviously LED traffic signals are a huge success.
Traffic signals must be their brightest at the hottest time of day. Since outdoor lighting with LEDs takes place at night, do we assume the Sun is not an issue? This would definitely be a bad assumption. Referring back to the traffic signal studies, it was demonstrated that non-energized traffic signal heads of any exterior color, exposed to the Sun, had internal temperatures exceeding 85°C. This fact must not be overlooked in the design of outdoor solid-state luminaires; after all, they will be in the Sun all day long.
Why? The LED luminaires will not be on during the day, so why be concerned with the solar heat?
It's true that LEDs degrade with excessive junction temperature while driven with current; the LED junction typically will not be degraded without electrical bias, even at storage temperatures.
However, white LEDs of the phosphor conversion type can be degraded when the phosphor is subjected to excessive heat, with or without electrical bias. That would be the case in luminaires that behave as solar collectors.
(Note that previous LED technologies by some manufacturers had epoxy encapsulant that was sensitive to the blue light or Ultra-Violet, and it yellowed over time. Obviously for outdoor applications, no element should yellow from UV exposure because of the required daily exposure to UV from the Sun.)
LEDs rated for 50,000 hours that are stated to have a 12-year service life may give a surprising reduction in lumen maintenance when subjected to 85°C on a daily basis for several years. A nighttime Luminaire is often characterized at 50% duty cycle, i.e. 50,000 hours is stated as a 12-year lifetime of lumen maintenance. However, if that Luminaire is powered at night and collecting solar heat by day, it may actually be a 6-year product.
Phosphor manufacturers have thermal degradation graphs for their product, which may show a permanent shift in CCT as well as conversion efficiency degradation. Some LED manufacturers have taken steps to distance the phosphor coating from the heat-producing junction.
There are SSL Luminaires with heat exchangers designed to address the solar issues, and some Luminaires really are efficient solar collectors. Can you spot the difference?
Traffic signals must be their brightest at the hottest time of day. Since outdoor lighting with LEDs takes place at night, do we assume the Sun is not an issue? This would definitely be a bad assumption. Referring back to the traffic signal studies, it was demonstrated that non-energized traffic signal heads of any exterior color, exposed to the Sun, had internal temperatures exceeding 85°C. This fact must not be overlooked in the design of outdoor solid-state luminaires; after all, they will be in the Sun all day long.
Why? The LED luminaires will not be on during the day, so why be concerned with the solar heat?
It's true that LEDs degrade with excessive junction temperature while driven with current; the LED junction typically will not be degraded without electrical bias, even at storage temperatures.
However, white LEDs of the phosphor conversion type can be degraded when the phosphor is subjected to excessive heat, with or without electrical bias. That would be the case in luminaires that behave as solar collectors.
(Note that previous LED technologies by some manufacturers had epoxy encapsulant that was sensitive to the blue light or Ultra-Violet, and it yellowed over time. Obviously for outdoor applications, no element should yellow from UV exposure because of the required daily exposure to UV from the Sun.)
LEDs rated for 50,000 hours that are stated to have a 12-year service life may give a surprising reduction in lumen maintenance when subjected to 85°C on a daily basis for several years. A nighttime Luminaire is often characterized at 50% duty cycle, i.e. 50,000 hours is stated as a 12-year lifetime of lumen maintenance. However, if that Luminaire is powered at night and collecting solar heat by day, it may actually be a 6-year product.
Phosphor manufacturers have thermal degradation graphs for their product, which may show a permanent shift in CCT as well as conversion efficiency degradation. Some LED manufacturers have taken steps to distance the phosphor coating from the heat-producing junction.
There are SSL Luminaires with heat exchangers designed to address the solar issues, and some Luminaires really are efficient solar collectors. Can you spot the difference?
Thursday, August 7, 2008
Scotopic verses Photopic for Best Night Vision
Updated Sept. 2010
For as long as we've been measuring outdoor lighting for streets, that luminance criteria has been based on the wrong color. We've had a false impression of safety, and that may conflict with lighting efficiency goals.
Safety with lighting must consider more than object and color recognition, or even crime prevention; we can actually suffer 'night blindness' by some modern lighting designs.
You should know the following when defining a luminance level for an application: Night Blindness occurs during the time your vision needs to adjust to lower luminance. After your vision is 'dark adapted', exposure to brighter lights will reset your vision back to the daytime (Photopic) level; then your 'Night Blindness' starts all over again. How long do we need to adjust?
When luminance is greater than 3 cd/m2, our "daylight vision" peak sensitivity is 555nm; this is the Photopic scale. For less than 0.001 cd/m2, our color sensitivity peaks at 500nm; this is the Scotopic scale.
Between Scotopic and Photopic is Mesopic where most OUTDOOR lighting aligns near the middle at about 0.1 cd/m2.
The first determining factor of Photopic vision is 3 or more footcandles of illumination, regardless of lighting technology or color. Scotopic vision occurs at a much lower illuminance, where it's actually pretty dark.
At Photopic luminance, cool white appears brighter than warm white simply because of peak sensitivity color alignment; NOT because of Scotopic vision. See more technical information at Scotopic Spin.
The color of HPS lighting, at any luminance, is a longer wavelength than our Photopic peak, so it can never align with our Scotopic vision. See an interesting article illustrating a Mesopic scale. Lighting can be far more efficient with less light of the proper color.
Also see Graphic Comparisons and Explanation
NOTE - In the news lately:
Effects of blue light on health (Human, animal and plants)
Unique Human Health Effects of Blue Light
Health Effects of Light Pollution PDF Ron Chepesiuk
For more background, see this Blue Rich White Paper by IDA.
For as long as we've been measuring outdoor lighting for streets, that luminance criteria has been based on the wrong color. We've had a false impression of safety, and that may conflict with lighting efficiency goals.
Safety with lighting must consider more than object and color recognition, or even crime prevention; we can actually suffer 'night blindness' by some modern lighting designs.
You should know the following when defining a luminance level for an application: Night Blindness occurs during the time your vision needs to adjust to lower luminance. After your vision is 'dark adapted', exposure to brighter lights will reset your vision back to the daytime (Photopic) level; then your 'Night Blindness' starts all over again. How long do we need to adjust?
When luminance is greater than 3 cd/m2, our "daylight vision" peak sensitivity is 555nm; this is the Photopic scale. For less than 0.001 cd/m2, our color sensitivity peaks at 500nm; this is the Scotopic scale.
Between Scotopic and Photopic is Mesopic where most OUTDOOR lighting aligns near the middle at about 0.1 cd/m2.
The first determining factor of Photopic vision is 3 or more footcandles of illumination, regardless of lighting technology or color. Scotopic vision occurs at a much lower illuminance, where it's actually pretty dark.
At Photopic luminance, cool white appears brighter than warm white simply because of peak sensitivity color alignment; NOT because of Scotopic vision. See more technical information at Scotopic Spin.
The color of HPS lighting, at any luminance, is a longer wavelength than our Photopic peak, so it can never align with our Scotopic vision. See an interesting article illustrating a Mesopic scale. Lighting can be far more efficient with less light of the proper color.
Also see Graphic Comparisons and Explanation
NOTE - In the news lately:
Effects of blue light on health (Human, animal and plants)
Unique Human Health Effects of Blue Light
Health Effects of Light Pollution PDF Ron Chepesiuk
For more background, see this Blue Rich White Paper by IDA.
Sunday, April 13, 2008
CRI is not the best metric with LEDs
Color Rendering Index (CRI) indicates how well a test source renders eight standard colors of intermediate saturation, when compared to a reference lamp of the same color temperature. Lab measured CRI is a comparison against a spectrally continuous red-weighted reference. Field conducted CRI tests are subjective with Human observers when luminance levels are below 3 cd/m2.
The industry is discovering that CRI is not the best metric for comparing LED light sources, especially at Mesopic levels. Originally developed in 1964, this index is based on outdated color models and assumes illumination sources with broad spectral distributions, whereas LEDs are narrow-band sources. And, nighttime lighting requirements fall primarily in the Mesopic range where our color sensitivity shifts with luminance, and there is no defined index.
Several standards bodies are addressing this deficiency, and in the interim, Color Temperature may be the most suitable tool for comparison because it is independent of observer subjectivity.
Here are some related links:
Metrics for solid-state lighting
Lumileds LED Glossary
www.netl.doe.gov PDF
The industry is discovering that CRI is not the best metric for comparing LED light sources, especially at Mesopic levels. Originally developed in 1964, this index is based on outdated color models and assumes illumination sources with broad spectral distributions, whereas LEDs are narrow-band sources. And, nighttime lighting requirements fall primarily in the Mesopic range where our color sensitivity shifts with luminance, and there is no defined index.
Several standards bodies are addressing this deficiency, and in the interim, Color Temperature may be the most suitable tool for comparison because it is independent of observer subjectivity.
Here are some related links:
Metrics for solid-state lighting
Lumileds LED Glossary
www.netl.doe.gov PDF
Saturday, April 12, 2008
Parking Garage LED Lights
How many LED parking garage lights have we found that were actually designed for the IESNA RP20 standard, and the NPA criteria? This means achieving the vertical footcandles without making a glare bomb.
A parking garage luminaire is a special critter, it has entirely different photometrics than typical outdoor luminaires. So this may be considered off-topic.
Here is a site with illustrations in parking garage lighting and links to DOE/GSA data.
This site describes IESNA RP-20 and LM-64 and asserts the following...
The lighting designer is cautioned to verify vertical illuminance without the need of floor reflectivity.
A parking garage luminaire is a special critter, it has entirely different photometrics than typical outdoor luminaires. So this may be considered off-topic.
Here is a site with illustrations in parking garage lighting and links to DOE/GSA data.
This site describes IESNA RP-20 and LM-64 and asserts the following...
The lighting designer is cautioned to verify vertical illuminance without the need of floor reflectivity.
Some LED 'downlights' are promoted as parking garage fixtures. However, since they are not specifically designed for this application, they rely upon floor reflectivity to achieve the RP-20 required vertical footcandles. Downlights that rely upon floor reflectivity may conveniently meet the LM-64 criteria since that suggests measuring illuminance during periods of minimal vehicle occupancy. In this case, vertical footcandle levels will be diminished during actual garage activity, but that's when vertical illuminance is most necessary.Be sure to check compliance to DOE ANSI/ASHRAE/IESNA Standard 90.1-2007
A downlight will usually create a hot spot and not adequately illuminate the far ends of a parking stall. Since the RP-20 horizontal uniformity Max/Min ratio is 10:1, meeting its horizontal illuminance criteria with typical downlights may require additional fixtures; increasing their power will only increase glare.
Saturday, August 4, 2007
Pay Back or Return on Investment (ROI)
Here's where we determine justification. Don't forget warranty provisions, and whether the company can actually afford to replace defective units.
How much does a LED light really save on your electric bill? If the LED is expected to light as much area as a conventional light, and it's efficacy is not as high as High Pressure Sodium or Metal Halide, then it will consume more electricity, which is no bargain at all.
We know the LED can use less electricity if it reduces the excessive light beneath the fixture which is wasted light anyway, but that may be only 20%, correct? Then a LED light installation must pay the purchaser back with reduced maintenance. Here is a LED ROI Payback Calculator to show when your investment is returned, and show the savings during all those years afterward.
Today many LED sales statements would have you believe that LEDs can do an equivalent lighting job for a fourth of the energy, or less. Don't be fooled. Here is an IES photometric file comparator that will help you with a comparison. Note that it must have 2 IES files in order to run.
If a light is a security or safety issue, a burned-out light must be replaced as soon as possible, so there is a call-out expense which may be overtime pay with a bucket truck. Eliminating a single repair incident may pay back the cost of a LED fixture. For a light that is costly to replace, such as on a bridge or in a tunnel requiring traffic maintenance, long-life LEDs can offer a huge advantage. These cases are ideal to justify the higher initial cost for a longer life, robust product.
Calculating the payback isn't difficult. For example, a 100 watt HID lamp will have a ballast that pulls an additional 20 watts, and replacing that with a 75 watt LED at 10-cents/kWh will save you less than $2 per month. How many years will it require to pay back on energy savings?
If routine maintenance requires re-lamping or a new ballast every 2 years, and if that costs $150 (including labor) then a $400 LED light could pay for itself in 3-years. Many agencies use a streetlight budget of $50 per year, and probably visit the light only when it's not working. So, the years they don't visit the light amounts to money used for something else within the department.
By switching to LED lights for maintenance savings, the department budget may be slashed by that amount. That's no good.
How much does a LED light really save on your electric bill? If the LED is expected to light as much area as a conventional light, and it's efficacy is not as high as High Pressure Sodium or Metal Halide, then it will consume more electricity, which is no bargain at all.
We know the LED can use less electricity if it reduces the excessive light beneath the fixture which is wasted light anyway, but that may be only 20%, correct? Then a LED light installation must pay the purchaser back with reduced maintenance. Here is a LED ROI Payback Calculator to show when your investment is returned, and show the savings during all those years afterward.
Today many LED sales statements would have you believe that LEDs can do an equivalent lighting job for a fourth of the energy, or less. Don't be fooled. Here is an IES photometric file comparator that will help you with a comparison. Note that it must have 2 IES files in order to run.
If a light is a security or safety issue, a burned-out light must be replaced as soon as possible, so there is a call-out expense which may be overtime pay with a bucket truck. Eliminating a single repair incident may pay back the cost of a LED fixture. For a light that is costly to replace, such as on a bridge or in a tunnel requiring traffic maintenance, long-life LEDs can offer a huge advantage. These cases are ideal to justify the higher initial cost for a longer life, robust product.
Calculating the payback isn't difficult. For example, a 100 watt HID lamp will have a ballast that pulls an additional 20 watts, and replacing that with a 75 watt LED at 10-cents/kWh will save you less than $2 per month. How many years will it require to pay back on energy savings?
If routine maintenance requires re-lamping or a new ballast every 2 years, and if that costs $150 (including labor) then a $400 LED light could pay for itself in 3-years. Many agencies use a streetlight budget of $50 per year, and probably visit the light only when it's not working. So, the years they don't visit the light amounts to money used for something else within the department.
By switching to LED lights for maintenance savings, the department budget may be slashed by that amount. That's no good.
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