LED Street Lighting Pilot Project Reduces Energy Use by 80%
Ann Arbor, United States of America
In 2005, Ann Arbor established a moratorium on new street lighting aimed at helping keep costs under control. As part of this cost cutting initiative, the City began trialing LEDs for general lighting purposes. LEDs reduce lighting energy requirements by 50% or more, but their greatest benefit is that they last much longer than conventional bulbs, reducing labor and maintenance costs. In Ann Arbor, this will translate to annual CO2 reductions of 2,200 tonnes and annual savings of @$100 per fixture.
What is it?
A trial program using two new LED street lighting technologies —the test globe fixture, which use 50% less energy, and the new cobrahead fixture which uses up to 80% less energy. This reduces emissions of mercury from coal power plants, as well as the city's climate footprint. Full implementation of LED streetlights could cut Ann Arbor's greenhouse gas emissions by over 2,200 tonnes CO2-equivalent emissions, or 4% of emissions from our municipal operations.
How does it work?
LEDs (light-emitting diodes) have been around since the 1960s. They are used as indicator lights in consumer products and—for the last few years—in traffic and pedestrian signals. Recently, however, they have become practical for general lighting purposes. Although they cost more upfront than the bulbs they replace, LED lights use less energy and last longer than conventional bulbs, resulting in significant energy and maintenance savings. They also produce directional light, which gives us more control over what we light (i.e. the street) and what we don't (the night sky), reducing light pollution and wasted energy.
Last year, the City of Ann Arbor spent $1.39 million on streetlights and traffic signals, a 3% reduction from 1998, due to the replacement of incandescent traffic and pedestrian crossing signals with LED versions. These replacements are saving the city $49,000 annually, but the bigger savings opportunities are in street lighting, which accounts for 92% of that $1.39 million. Ann Arbor is currently investigating LED street lighting that has the potential to cut the cost, energy use, and greenhouse gas emissions of our street lighting all in half. With LED technology getting good enough for street and parking lot lighting, the City has begun testing products to see if they will meet their needs—to be safe, attractive, and save money.
The first test fixtures that the City received and installed in its City Hall parking lot in the summer of 2005 were unimpressive. They felt that LED lighting manufacturers were not quite ready to meet the public lighting needs. Over the following year, however, the test fixtures they received from manufacturers increased markedly in quality and today Ann Arbor is close to migrating to LEDs for public lighting.
The City's Field Operations staff are currently testing two classes of LED streetlights. The first is a block of replacements for the downtown pedestrian globe lights, purchased with help of the Downtown Development Authority (DDA). This retrofit globe from Lumecon houses LEDs on four panels that face down and out, directing the light toward the street and away from the sky. Each fixture draws 48 watts and is expected to last 10 years, replacing fixtures that use 100 watts and last only two years. The University of Michigan-Ann Arbor uses the same style of globe light on its campus and is currently conducting its own testing of the fixtures.
The second test installation consists of a series of overhead streetlights (called "cobraheads" because of their shape) on a residential street. These fixtures have not been purchased they are on loan from the manufacturers. Wattages vary from 50 to 80 watts for fixtures that replace 250-watt installations. Manufacturers of cobrahead replacements currently installed for testing include Holophane, IntenCity, Leotek, Lumecon, and Millenia Technologies.
To evaluate these fixtures, Ann Arbor is employing a three-pronged test process, with lights being assessed on light output, heat management (which affects lifetime), and general public input.
Light Output: The cobrahead replacements are installed on a residential street where the spacing allows for each fixture's light output to be judged independent of adjacent fixtures but where different fixtures can be easily compared. City staff are measuring light output and plans are in the works for a more involved public input process to evaluate the fixtures' aesthetics.
Heat Management: One of the most attractive characteristics of LEDs is their long lifetime, but this lifetime depends directly on the fixture's operating temperature. As a result, heat management is vital to producing fixtures that achieve our goal of a ten-year life. City staff are measuring the operating temperature of fixtures and using the chart below to project the useful life of different test fixtures.
Public Input: All the test installations have signs requesting input, and the response from the community has been overwhelmingly positive (81 of 83 responses). 97% were positive responses emphasizing the lack of light spilling out onto yards and house faces ("light trespass"). One negative response commented that the light was too harsh. The other negative comment reflects a minority opinion about the purpose of public lighting, objecting that the LED cobrahead no longer lit up their garage and yard and that the globe LEDs were creating a "dark cavern" through the downtown.
At least 50-80% energy savings = 2,200 tonnes CO2e if fully implemented in Ann Arbor
- 203 kg CO2e per downtown globe annually
- up to 781 kg CO2e annually per cobrahead
- $100/yr for each ornamental fixture, more for cobraheads
- $472 incremental cost per fixture, pays back in 4.7 years
Ann Arbor has two barriers to overcome before deploying LEDs citywide. The first is identifying a funding mechanism to pay for the upfront incremental cost of the new fixtures (which may be, in part, our Municipal Energy Fund).
The second, is that the local utility owns and operates many of our streetlights. In order to realize savings from retrofitting the utility-owned fixtures, they will need approval of a new streetlighting tariff from the Michigan Public Service Commission-which takes into account the lower energy use and maintenance requirements of the LED fixtures. Without this tariff, it will not make financial sense to upgrade these utility-owned fixtures.
Without the tariff it is still possible to upgrade the City's 1,640 city-owned fixtures and save approximately $160,000 annually, or 12% of its traffic signal and streetlight budget.
- Identify a suitable LED replacement for existing streetlights
- Identify a funding mechanism for retrofits
- If necessary, seek approval of a new tariff that reflects LEDs' lower costs