1) Why put solar at this location?
Athens-Clarke County has a commitment to generate 100% of its electricity from clean and renewable energy by 2035. As a large, high use facility, the library utilizes a significant amount of electricity. In 2022, the library spent approximately $123,000 to purchase 1,333 megawatts of electricity. Using the data provided by the U.S. Energy Information Agency, this is equivalent to the annual electricity use of approximately 100 homes in our area.
Beyond just being a high energy user, the library is well suited to be a solar energy consumer as the facility is used seven days per week and often has hours that extend into the evening. This aligns energy use in the afternoons when solar is highly productive.
2) Why don’t you just put the solar on the roof?
Initially, the project proposed to install solar on the roof, as that is the preferred location for solar in a community as small as Athens-Clarke County. Regretfully, as the project moved from the concept to design phases, ACCGov staff determined that the seams on the metal roof were not structural, so a traditional non-penetrating metal roof installation was not feasible. Instead ACCGov could either adapt non-structural roofing components to hold solar racking, install flat roof penetrations, or utilize thin-film solar that is glued to the roof.
The adaptation of non-structural roofing components for solar racking was eliminated because the equipment was not designed or rated for use in this manner. Additionally, a roofing consultant working on behalf of ACCGov recommended against this technique because it increases the chances of roof leaks in the library.
The use of flat roof penetrations was eliminated as it would void the warranty on the library roof.
The use of thin film solar was eliminated because it too would void the warrant on the library roof. Additionally, two different solar installers advised ACCGov that there is a high risk of delamination within 5-10 years of installation. Finally, it would be nearly impossible to reutilize the existing thin film solar as the library roof is upgraded and maintained in the future.
3) What about using a solar parking lot canopy?
This option was evaluated as well. Unfortunately the majority of the parking at the library is installed in a semicircular manner that is not readily adapted to the straight run installations of solar canopies. A singular linear parking area is located on the north side of the parking lot. A solar canopy installed at this location would necessitate the removal of at least four large canopy trees from the parking lot perimeter, while possibly also requiring the removal of four additional trees from parking lot islands located just south of any possible canopy. Because this canopy is fixed and does not move with the sun, it would generate just a fraction of the renewable energy produced by the proposed solar trackers.
4) What about other locations in the parking lot or along the side of the library?
The design team explored installing a solar canopy at the unloading zone south of the library entrance, but this option was eliminated because of cost and the relatively small amount of renewable energy it would generate.
The design team explored installing the solar trackers in parking lot spaces rather than the existing islands. This option was eliminated because any removal of parking lot spaces will result in the site coming out of compliance with minimum parking requirements outlined in ACCGov code. More importantly, the library has recently lost access to the overflow parking lot located to the south on property owned by the Clarke County School District. As a result, the parking pressure on the library is expected to increase, and potentially exceed available capacity during large events.
The design team considered the installation of trackers in the stormwater area located to the east of the library. Approximately three trackers could be installed in this area and an installation here would likely necessitate the removal of 3-5 maturing large canopy landscape trees. While this area had merit, representatives for the Library expressed a preference that it not be utilized, as it would obscure the views from the multipurpose rooms and patrons entering the library would only have views of the back of the tracker units.
4) Trees sequester carbon, which helps us with our climate goals. Will there be any carbon savings from this project?
Staff have modeled the trees that are proposed to be removed using the MyTree tool provided by the U.S. Forest Service. Over the next twenty years, the trees are projected to directly sequester nearly 14,000 lbs of CO2, which results in the equivalent of approximately 51,000 lbs of CO2 removed from the atmosphere. The solar trackers are proposed to generate approximately 380,000 kWh of renewable energy per year. According to the U.S. Energy Information Agency, 1.01 lbs of CO2 is generated for each kWh of electricity produced in Georgia. Thus, over the same 20 year period, the solar trackers will reduce library-associated CO2 production by more than 7,800,000 lbs. As a result, the trackers are approximately 150X more efficient at reducing CO2 than the trees in this parking lot.
6) Trees provide other benefits such as stormwater and shade. What happens to these?
The trackers will produce shade, offsetting the shade and associated energy savings expected from the parking lot trees. While the parking lot islands will remain pervious and be revegetated, the combination of the solar trackers and parking lot islands will not be as efficient in generating the approximately 1,000 gallons per year of stormwater runoff reduced by these trees. To offset this, plus the other ancillary social and environmental benefits provided by trees, ACCGov staff propose to replant at least 9 large canopy trees to account for the loss of trees at this location. As a result, this project will result in net environmental benefits to our community.
7) Can you replant the trees somewhere else on site?
Some, but likely not all of them. The library property is highly constrained and most available planting spaces are utilized. Once all available onsite spaces have been utilized, staff will evaluate additional locations such as Rocksprings Homes, Rocksprings Park, or along streets in adjacent neighborhoods. The goal of any replanting will be to select trees and locations that result in the replanted trees outperforming the growth and resulting environmental benefits of what we would anticipate if the parking lot trees were retained.
8) Does this project comply with the tree ordinance?
Yes, but also no. Section 8-7-19 (I)(2)(i) of the Community Tree Management Ordinance permits the removal of a protected tree that has an unresolvable conflict with infrastructure that is creating an unsafe condition or poses a hazard to public health, safety, and welfare. Section 8-7-16 (d) further identifies that the Landscape Management Division Administrator of the Central Services Department has the authority to approve the removal of an ACCGov tree. Lastly, section 8-7-16 (e) requires the replacement of removed trees if such removal results in the decrease of the tree canopy cover on the site or lot less than that required.
Using the canopy calculation methodology of the tree ordinance, the library site has credit for 47% future canopy coverage where 40% is required. After the trees in question are removed, the site will have credit for 42% future canopy coverage. As such replanting is not required, but will be facilitated where possible.
Bigger challenges exist when parking lot trees are considered. Section 8-7-15 (J) outlines the requirement for one parking lot tree per seven spaces, with no more than fourteen contiguous spaces without a tree. While 8-7-16 (e) does not necessitate the perpetual protection and replacement of parking lot trees, ACCGov has a track record of ensuring parking lot tree survival for a period of 3-5 years, with the assumption that after five years the trees are likely to remain in place. Should this project or any future development trigger the reapplication of the Community Tree Management Ordinance, additional parking lot islands and trees would have to be established, resulting in a net loss of parking spaces at the library. In short, it is legal to remove the trees today, but doing so may create substantial design challenges in the future.
The library is not the only location where solar canopies/trackers and parking lot trees will come into conflict. As energy costs increase, solar costs steady, and businesses continue to adopt climate goals, it will be increasingly likely that businesses seek to incorporate solar into their properties, including within and above parking lots. This challenge is already occurring across the nation. As such, staff will review the subject to determine what, if any, modifications to local ordinances should be considered to address this issue. If modifications to the tree ordinance are recommended, they will be presented to the Community Tree Council and Planning Commission for recommendation, before being brought to the Mayor and Commission for consideration. If modifications to local ordinances are not recommended or no action is taken, the library will continue have to address this challenge in the future as this site is modified or expanded.
9) If this is such a difficult location, why even move forward with solar here?
The library was able to secure a commitment for $140,000 in matching funding for the installation of solar at this facility. This creates the financial incentive to make this project a priority over other public sites. Without this incentive, staff would recommend the funding be deployed elsewhere where fewer challenges exist.
This external funding is a dollar-for-dollar match, so a total of $280,000 must be invested if ACCGov is to maximize outside funding. This can be achieved with the implementation of Option 1 from the agenda report, where a total of four solar trackers are installed to supply approximately 11.6% of the facility’s energy from renewable sources. The implementation of Option 1 would necessitate the removal of 3-4 parking lot trees. Ultimately, the SPLOST 2020 User Group recommends the implementation of Option 2 to install ten trackers supplying approximately 28.9% of the facility’s energy from renewable sources, because it works more aggressively to meet ACCGov’s climate goals while maximizing financial savings for the library. Option 2 necessitates the removal of 9-10 trees. Option 1 has a simple rate of return on local investment of 10.3 years, while Option 2 has a simple rate of return on local investment of 15.8 years. If the Mayor and Commission would like to maximize the use of outside funding while minimizing impacts to the parking lot trees, they may want to reconsider Option 1.