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41 A primary objective of this synthesis report is to document the number and array of renew- able energy projects located on airport properties in the United States. The resulting Renewable Energy Projects Inventory serves both as a record of renewable energy projects at airports and as a snapshot of industry progress to date. The inventory is presented as Appendix A of this report and as a separate digital product on the TRB website (go to www.TRB.org and search for âACRP Synthesis 110â). The inventory includes renewable energy projects by technology and resourceâbioenergy, fuel cells, geothermal, solar photovoltaic, solar thermal, and wind powerâthat were either operating or undergoing active construction as of December 31, 2019. It also includes a list of airports that purchase renewable energy from utilities and private partners in an effort to document this alternative approach to securing renewable energy without constructing a project on site. Further research identified additional projects in various stages of early development at numerous airports; these projects are not included in the inventory because of the uncertainty of eventual completion. The Renewable Energy Projects Inventory is specific to renewable energy projects operating at U.S. airports by the end of 2019. It also includes any projects confirmed to be operating during the first quarter of 2020 (before publication of this report). Information reported in the inventory varies by technology, as dictated by the availability of data for various renewable energy projects. For example, solar PV projects recorded in the inventory include information on project design, system capacity, and power purchasing, as these details are typically part of the public record. Information on other technologies such as geothermal and biofuels is not as readily available, as these projects may have been integrated into existing building design and efficiency measures and are thus more difficult to disentangle from overall building operations. However, all inventory entries include airport by name and code, hub classification using the National Plan of Integrated Airport Systems (NPIAS), and FAA region to enable comparison of projects and technologies among airports of similar size and geography. Figure 29 shows the FAA geographic regions used to categorize the renewable energy projects. The reportâs inventory has been assembled from a variety of sources, including the following: â¢ A list of solar projects included in ACRP Report 141: Renewable Energy as an Airport Revenue Source (Barrett et al., 2015) and references found in other ACRP reports (specifically, ACRP Synthesis 69: Airport Sustainability PracticesâDrivers and Outcomes for Small Commercial and General Aviation Airports [Prather and DPrather Aviation Solutions LLC, 2016] and ACRP Synthesis 100: Lessons Learned from Airport Greenhouse Gas Reduction Efforts [Barrett, 2019]); â¢ A summary of projects funded under the AIP; â¢ FAA staff, who provided information on (1) projects reviewed for airspace safety and envi- ronmental compliance under NEPA and (2) projects constructed by FAA to provide power to air traffic control towers that it owns and operates; C H A P T E R 3 Airport Renewable Energy Projects Inventory
42 Airport Renewable Energy Projects Inventory and Case Examples â¢ Airport publications and announcements; â¢ News articles and reports appearing in established media outlets; and â¢ Google Earth. An initial list of airport renewable energy projects was emailed to more than 300 airport contacts to confirm the information cataloged in the inventory and to solicit additional projects or details that may have been omitted. Though efforts have been made to verify all information included in the inventory, there may be inaccuracies and omissions. For example, as part of verifying the current list, one solar project that had long been reported as occurring on airport property was found to be located on municipal land and was therefore removed from the list. In another example, a solar project on airport property operated for 20 years and was dismantled in 2018 by the utility when it determined the project to be at the end of its useful life. This project does not appear on the report inventory. The following sections present excerpts of the data recorded in the inventory, highlighting identifiable trends and general conclusions drawn from the data. 3.1 Data Summary The Renewable Energy Projects Inventory includes a total of 219 renewable energy projects at 146 airports in the United States. These projects are located in 41 different states and 2 U.S. territories (Puerto Rico and the Virgin Islands). Figure 30 includes the number of projects by renewable technology. Solar PV energy has been installed more than any other technology, with 158 projects identified on airport property. GHPs have been incorporated in the second-largest number of airport projects (26). The remaining technologies have significantly fewer installations: 11 for bioenergy, 10 each for solar thermal and wind power, and 4 for fuel cells. 3.2 Data by Technology The following section presents an overview of the data by technology. 3.2.1 Bioenergy Bioenergy is a category that includes several different technologies, all of which combust organic matter to generate energy. The technologies represented in this list include generators Figure 29. FAA regions used to group geographic data on renewable energy projects.
Airport Renewable Energy Projects Inventory 43 that burn woody biomass, liquid biofuel, and biogas produced in an anaerobic digester. The category also includes the use of landfill gas, which at airports is primarily used as a renewable natural gas for airport vehicles. A total of 11 bioenergy projects have been identified at airports, of which 6 use landfill gas, 3 burn woody biomass, 1 burns biogas from an anaerobic digester, and 1 burns liquid biofuel for backup generation (see Figure 31). Of these 11 projects, 5 power vehicles, 3 produce heat for a building, 1 both powers vehicles and heats buildings, and 2 produce electricity. The category is weighted by the adoption of renewable natural gas (landfill gas) by large airports primarily in FAAâs Western-Pacific Region. Omitting landfill gas, both large and small airports have implemented bioenergy technologies, with the five remaining projects covering different FAA regions. Given the small sample size, however, it is difficult to draw any conclusions from the data, the exception being that the limited number of projects suggests that bioenergy is not particularly economical or easy to implement at this time. Figure 30. Number of renewable energy projects installed at airports, by technology. Figure 31. Bioenergy technologies and corresponding number of projects at airports.
44 Airport Renewable Energy Projects Inventory and Case Examples 3.2.2 Fuel Cells There are four examples of fuel cell projects at airports. Three have been funded by DOE to demonstrate the use of hydrogen fuel cells in GSE by FedEx. The fourth project was a demonstra- tion of a natural gasâcatalyzed fuel cell; this project was also funded by DOE to demonstrate the use of a fuel cell for on-airport electricity generation. The projects have been deployed at small and medium-sized airports in four different FAA regions. Because the funds were directed toward a specific use by a single operator in three of the four examples (i.e., powering GSE operated by FedEx), the similarities in airport size are indica- tive of the airports where FedEx operates. Likewise, the different regions reflect the companyâs geographical coverage. As with bioenergy, the sample size is too small to draw conclusions other than to show that fuel cells remain in use for demonstration projects and still depend on federal research funding. 3.2.3 Geothermal GHPs are the second most commonly installed renewable energy technology at airports, with 26 individual projects at 25 airports. Geothermal energy has been adopted by airports in all five hub classifications, with nonhub airports accounting for more than half (58%), as shown in Figure 32. As geothermal projects are most often developed during new construction, there may be some correlation between growth in regions of the country served by nonhubs and proposals for new terminal buildings, but there are not sufficient data to confirm such a conclusion. In addition, airport geothermal projects have been implemented in seven of the eight FAA regions, with exactly half (13) of all geothermal projects occurring in the Great Lakes Region. The distribution of projects by region is shown in Figure 33. Geothermal systems typically make sense in climates where both heating and cooling are necessary, because system performance can be optimized in cases where maximum and minimum annual temperatures are most disparate. These conditions generally occur in the north-central portion of the country represented by FAAâs Great Lakes Region, as well as in adjacent areas to the west and east. These conditions likely contribute in part to the higher number of geothermal projects in the Great Lakes because the geothermal industry is more established in the region and engineers are more familiar with the technology as an alternative to traditional building heating and cooling systems. Figure 32. Geothermal heat pump projects installed at airports, by hub size.
Airport Renewable Energy Projects Inventory 45 3.2.4 Solar Photovoltaic A total of 158 solar PV projects have been installed at 116 different airports in the United States. The combined capacity of these solar PV projects is 305 MW DC, or approximately enough energy to power 48,000 average U.S. homes. (PVWatts was used to convert DC power to AC, assuming a conversion loss of 14%. The Solar Energy Industry Association provided a number for the average amount of electricity used for a household nationwide.) Solar PV projects at airports are located in 36 different states and in one U.S. territory. The annual increase in the number of solar PV installations at airports through 2019 is shown in Figure 34. The number of projects installed at airports annually from 2007 to 2019 is shown in Figure 35. According to the figure, the highest number of individual solar projects were installed at airports in 2012. The total capacity of solar PV projects installed at airports annually from 2006 to 2019 is shown in Figure 36. According to the figure, nearly 40,000 kW of solar energy was installed in 2018 Figure 33. Number of geothermal projects installed at airports, by FAA region. Figure 34. Growth in number of solar PV projects developed at airports.
46 Airport Renewable Energy Projects Inventory and Case Examples Figure 35. Number of solar PV projects installed at airports, by year. Figure 36. Airport solar PV installed capacity in kW, by year.
Airport Renewable Energy Projects Inventory 47 Figure 37. Percentage of solar PV projects installed at airports, by hub size. Figure 38. Number of solar PV projects installed, by FAA region. up from 22,000 kW in 2017. A comparison of Figures 36 and 37 shows that, initially, smaller capacity installations were predominant, but in recent years the size of individual installations has increased. In 2018, for example, two installationsâ28,000 kW at Tallahassee International Airport and 6,000 kW at Eastern Oregon Regional Airportâmade up 86% of the total energy of nine projects installed. In 2017, the year with the second-most capacity (22,000 kW) and the second-highest number of projects (16) installed, 9 projects were over 1,000 kW (or at least 5 acres in size). These numbers demonstrate a move toward larger, utility-scale projects. Projects installed in 2020 are not presented in the data because they do not represent a complete year; however, it is important to note that the largest airport solar project, Phase II at Tallahassee, a 55,000-kW project, was energized in January 2020. Another large project currently under construction is a 50,000-kW project at Sanford Seacoast Regional Airport in Maine: it is antici- pated to be operational by the end of 2020. The data show that solar projects are being developed by airports of all sizes with relatively equitable distribution, from a low of 15% of solar projects at medium hub airports to a high of 26% at general aviation airports. The percentage of projects installed for each hub classification is provided in Figure 37. Solar projects have also been installed across all FAA regions, with the exception of the Alaskan Region. The greatest number of projects (42) have been installed at airports in the Western-Pacific Region, as shown in Figure 38.
48 Airport Renewable Energy Projects Inventory and Case Examples More than half of the solar projects installed at airports are owned by the airport (58%), while approximately one quarter (28%) of projects are owned and operated by private developers. Other owners of solar projects at airports include tenants, utilities, and FAA. Power generated by solar projects at airports is used by a variety of entities. The data reveal that 61% of these solar projects channel energy directly to the airport where they are located, providing power for on-site energy needs. Utilities buy the power from 20% of airport solar projects, adding the energy to the regional utility grid for residential and commercial use. In 12% of the projects, airports purchase the power generated at the facility through an agreement with private project developers. The remaining 7% of users include various airport tenants and FAA, who use the power for their on-site energy. Solar projects come in three primary designs: roof-mounted, ground-mounted, and canopy- mounted. The number of projects of each design is shown in Figure 39. The implementation of different solar PV project designs has changed over time, as shown in Figure 40. The highest number of rooftop installations occurred between 2010 and 2014, with a peak in 2012. Ground-mounted projects have been less volatile, with a steady number of projects annually since 2008 and a peak in 2017. The number of canopy projects has increased over time, with four of the five most prolific years occurring since 2015. 3.2.5 Solar Thermal Solar thermal has been implemented at 10 U.S. airports. Eight of the 10 projects have occurred at small and nonhub airports, and half of the projects have been installed at airports in the Great Lakes Region. In addition, eight of these 10 projects provide hot water heating for domestic use, building heating, or both. The remaining two solar thermal projects produce building heating through forced hot air systems. Half of the systems were installed in 2010 or 2011 (likely the result of federal grants available through ARRA). 3.2.6 Wind Power Ten wind power projects have been installed at nine airports in the United States. Six of the 10 projects have been installed at large hub airports, and half are located at airports in the Great Lakes Region. Five of the 10 projects are building-mounted wind turbines; four of these are small- scale, ground-mounted wind turbines; and one is a three-bladed design typical of commercial wind farms. Seven of the 10 wind power projects were installed in 2011 or before. The energy generated from each of these projects is used on site. Figure 39. Number of solar PV projects installed at airports, by design type.
Airport Renewable Energy Projects Inventory 49 3.3 Conclusions from the Data The data show that a variety of renewable energy technologies have been installed at airports, with solar PV and geothermal the most widely adoptedâand therefore the most impactfulâ to date. Other renewable energy technologies (bioenergy, fuel cells, solar thermal, and wind power) have been installed primarily as demonstration projects, with many relying on federal grants. For solar PV, the data show an emerging trend toward larger, third-party owned projects that generate power and revenue for airports, while lessening the operational and maintenance demands of airport-owned and -operated projects. Additionally, more ground-mounted and canopy-mounted solar PV projects are being constructed than are roof-mounted projects, suggesting that ease of installation (for ground-mounted) and airport co-benefits (for canopy- mounted) are factors in the design process. Geothermal projects have been installed primarily in concert with new construction, with a majority of projects located in the north-central part of the country. The climate in this region makes geothermal systems more efficient, and the geothermal industry appears to be responsive to airport opportunities. Though the remaining renewable energy technologies examined in this report do not currently present a significant opportunity for generating renewable energy at airports, they may meet individual airport needs and may represent success for an airport in its achievement of energy and environmental objectives. Note: Key and bars in figure correspond, left to right. Figure 40. Number of solar PV projects installed at airports, by design type and year.