2019-089 LED Street Light Retrofit ProgramDate: April 26, 2019 Report No. 2019-089
INFORMAL STAFF REPORT
SUBJECT:
Benefits and functionality of switching to LED streetlights including the environmental
impact of LEDs once they are discarded.
PURPOSE:
The purpose of this Informal Staff Report is to provide a high-level summary of the
benefits, environmental challenges, impacts, and solutions related to the upcoming LED
retrofit of all high-pressure-sodium and other forms of older street lighting within the
City.
DISCUSSION:
During the second quarter of 2019, DME will begin a three-year process to replace all
the high-pressure-sodium street lights within the City. There are several benefits the
City of Denton will realize from an LED retrofit. These include:
LED street lights use less energy than the current high-pressure-sodium bulbs.
LED street lights have less maintenance associated with them.
LED street lights provide better illumination than high-pressure-sodium.
LED street lights have a predicted longer life span (50,000 – 100,000 hours)
compared to high-pressure-sodium (20,000 hours).
LED street lights have a smaller amount of light degradation after 50,000 hours of
use.
LED street lights are dimmable.
LED lights, with a proper control system and controller, can be managed on a per
light basis allowing greater operational control and flexibility.
LED street lights are not affected by a “warm-up” period to get to full strength and
can be turn on and off without a “cool-down” period.
LED lights have the same options, such as shields, available as do other
technologies.
During the initial LED evaluation study performed by DME, readings of actual energy
usage were taken on the products of a variety of LED luminaires. The collected data
from all samples provided an average energy used for each classification of LED (i.e.
100W equivalent, 250W equivalent, or 400W equivalent).
Date: April 26, 2019 Report No. 2019-089
High Pressure Sodium LED Energy
∆ (W)1 Energy
(W)atts Lumens2 CRI Energy Lumens3 CRI
100W 116 8,550 17 69 5,179 70 (47)
250W 298 25,600 25 161 13,170 70 (137)
400W 465 45,000 25 247 25,876 70 (218)
The table provides energy, lumen, and the Color Rendering Index (CRI) data related to
high-pressure-sodium and LED luminaires. The last column is the potential average
energy savings between high-pressure-sodium and LED luminaires. The table shows
that lumens from high-pressure-sodium are greater than the lumens from the LED
fixtures; however, it is the CRI of the light that makes the lower lumen value of LED a
much greater benefit. CRI is a measure of the ability of a light source to reveal colors
faithfully in comparison with an ideal or natural light source. The higher the CRI, the
better the eye can recognize what it is seeing. So, even though the lumens are lower,
the higher CRI produces better light to the eye. This fact, combined with less energy
used, are two of the primary benefits associated with LED street lights.
Subject to the results of an outstanding RFP, and City Council approval, DME expects
to recommend that a “smart” street light control system to be implemented in parallel
with the LED retrofit. The benefits of a smart control system include:
Automated “light-out” message for non-working lights.
Control of lighting, including dimming and/or on/off, from a central point.
Some LED light control systems offer a smart-phone based control application to be
used by field personnel.
Facilitates Denton’s qualifications for a possible “smart cities designation.
GPS monitoring of street light locations to provide accurate billing.
Revenue class metering of energy used for the street lights.
Reporting of power factor, actual hours burned, and other engineering specific data.
If installed simultaneously with the LED deployment, it will reduce overall costs,
increase efficiency and the functionality of the street lights.
Smart/remote controls could be used to help cities deal with issues such as crime,
and pedestrian and driver safety.
Denton’s street light count, as of March 2019, is 320, 400 watt; 1534, 250 watt; and
5997, 100 watt street lights. Based on these bulb counts, the City of Denton could
1 Based on medium lumen values across all lighting classifications
2 Mean lumen
3 Medium lumen
Date: April 26, 2019 Report No. 2019-089
expect to save 561.8 kW savings of energy. Based on Schedule LS (from DME Rate
Book) standard of 333 hours of usage annual usage, this is a savings of 187,079 kWh.
The Environment Protection Agency provides a Greenhouse Gas Equivalencies
Calculator4 that gives equivalency results for several environmental factors. Input of
the kWh savings for the City of Denton’s LED retrofit provides the following
equivalencies:
Greenhouse gas emissions from
o 28.1 passenger vehicles driven for one year, or
o 323,455 miles driven by an average passenger vehicle
CO2 emissions from
o 14,886 gallons of gasoline consumed, or
o 12,995 gallons of diesel consumed, or
o 144,626 pounds of coal burned, or
o 1.8 tanker trucks’ worth of gasoline, or
o 15.8 homes’ energy use for one year, or
o 23.1 homes’ electricity use for one year, or
o 0.722 railcars’ worth of coal burned, or
o 306 barrels of oil consumed, or
o 5,408 propane cylinders used for home barbeques, or
o 0 coal-fired power plants in one year, or
o 16,869,000 number of smartphones charged
Greenhouse gas emissions avoided by
o 46.1 tons of waste recycled instead of landfilled, or
o 6.6 garbage trucks of waste recycled instead of landfilled, or
o 5,772 trash bags of waste recycled instead of landfilled, or
o 0.028 wind turbines running for one year, or
o 5,025 incandescent lamps switched to LEDs
Carbon sequestered by
o 2,187 tree seedlings grown for 10 years, or
o 156 acres of U.S. forests in one year, or
o 1.1 acres of forests preserved from conversion to cropland in one year
With over 7800 luminaries included in the LED retrofit program, DME recognizes that
a significant amount of waste would be produced from the disposal of the replaced HPS
street light fixtures. To minimize the environmental consequences for the retrofit, DME
researched companies to determine their interest in recycling the old luminaires and
4 https://www.epa.gov/energy/greenhouse‐gas‐equivalencies‐calculator
Date: April 26, 2019 Report No. 2019-089
bulbs connected with the high-pressure-sodium fixture. Four of these companies were
contacted regarding their interest in recycling the old light fixtures -- Pratt Materials (at
the City of Denton landfill), Fulton Supply and Recycling (current scrap service
provider for Denton Municipal Electric), Stubbs Iron & Metal, and Geep Recycling.
Three provided a similar response by stating they would accept the waste but separating
the metals from the glass was not cost effective for them so there might be a charge
associated with “breakage.” Geep Recycling had no interest.
The high-pressure-sodium bulbs, currently used by DME, do contain a trace amount of
mercury and the bulb manufacturer recommends disposal in accordance with current
law. DME has identified a company in Ft. Worth, Lighting Resources, LLC., who can
provide the necessary recycling, documentation, and certificates needed to legally
dispose of the bulbs. Recycling is accomplished by crushing the bulbs, then using tort
ovens, the mercury is separated from the phosphorus powder. The mercury is distilled
until it is back to its virgin state. There will be a cost of $1.25 per light bulb plus a
transportation/pick-up fee of $45 and a fuel surcharge of $28 per each scheduled pickup
completed by Lighting Resource, LLC. The City of Denton Solid Waste department
has used this company for the limited instances that such a service was needed. Based
on the projected cost, it is anticipated that recycling the bulbs will add less than $20,000
to the total project cost.
Conversations with the DME Superintendent in charge of street light maintenance (who
will be leading the retrofit project from the DME crew perspective) mentioned his staff
normally separates the glass from the metals. The metals go to Fulton Supply for
recycling and the glass will go into the solid waste receptacles – which eventually ends
up at the landfill.
CONCLUDING REMARKS:
Upon completion of the retrofit program, along with the implementation of a control
system, the City of Denton will be poised to be a leader in the electric utility industry to
both reduce energy and maintenance cost associated with the City’s street lights; and,
provide control to manage this critical infrastructure while providing service and future
enhancement capabilities.
DME is aware of the environmental impacts, both positive and negative, the LED
retrofit program will provide the citizens of Denton. It is our goal to assure that any
environmental impact is a minimal as possible.
STAFF CONTACT:
George Morrow
DME General Manager
940-349-8487
George.morrow@cityofdenton.com
Date: April 26, 2019 Report No. 2019-089
Jerry Fielder, P.E.
Division Engineering Manager - Distribution -- DME
940-349-7173
jerry.fielder@cityofdenton.com