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Airport Greenhouse Gas Reduction Efforts (2019)

Chapter: Glossary

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Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2019. Airport Greenhouse Gas Reduction Efforts. Washington, DC: The National Academies Press. doi: 10.17226/25609.
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Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2019. Airport Greenhouse Gas Reduction Efforts. Washington, DC: The National Academies Press. doi: 10.17226/25609.
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Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2019. Airport Greenhouse Gas Reduction Efforts. Washington, DC: The National Academies Press. doi: 10.17226/25609.
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Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2019. Airport Greenhouse Gas Reduction Efforts. Washington, DC: The National Academies Press. doi: 10.17226/25609.
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86 Aeronautical uses: Any activity that involves, makes possible, or is required for the operation of aircraft or that contributes to or is required for the safety of such operations. Air conditioning: Cooling and dehumidifying the air in an enclosed space by use of a refrig- eration unit powered by electricity or natural gas. Note: Fans, blowers, and evaporative cooling systems (“swamp coolers”) that are not connected to a refrigeration unit are excluded. Airport Improvement Program (AIP): The AIP is authorized by the Airport and Airway Improvement Act of 1982 (AAIA) (P.L. No. 97-248, as amended). The broad objective of the AAIA is to assist in the development of a nationwide system of public use airports adequate to meet the current and projected growth of civil aviation. The AAIA provides funding for airport planning and development projects at airports included in the National Plan of Integrated Air- port Systems. Airport master plan: A long-range plan for development of an airport, including descriptions of the data and alternative analyses on which the plan is based. Airport sponsor: A public agency or tax-supported organization, such as an airport author- ity, city, county, state, or federal government, that is authorized to own and operate an airport, to obtain property interests, to obtain funds, and to be legally, financially, and otherwise able to meet all applicable requirements of the current laws and regulations. Alternating current (AC): An electric current that reverses its direction at regularly recurring intervals. AC occurs when charge carriers in a conductor or semiconductor periodically reverse their direction of movement. The voltage of an AC power source can be easily changed by means of a power transformer. This allows the voltage to be stepped up (increased) for transmission and distribution. High-voltage transmission is more efficient than low-voltage transmission over long distances, because the loss caused by conductor resistance decreases as the voltage increases. Array (solar): Any number of solar photovoltaic modules or solar thermal collectors or reflec- tors connected to provide electrical or thermal energy. Backup power: Electric energy supplied by a utility or on-site generating unit to replace power and energy lost during an unscheduled equipment outage. Balance of system (or plant): In a renewable energy system, balance of system refers to all components other than the mechanism used to harvest the resource (such as photovoltaic panels or a wind turbine). Balance-of-system costs can include design, land, site preparation, system installation, support structures, power conditioning, operation and maintenance, and storage. Base load plant: A facility, usually housing high-efficiency steam-electric units, that is nor- mally operated to take all or part of the minimum load of a system, and which consequently Glossary

Glossary 87 produces electricity at an essentially constant rate and runs continuously. These units are operated to maximize system mechanical and thermal efficiency and minimize system operat- ing costs. Biomass: Organic nonfossil material of biological origin constituting a renewable energy source. Boiler: A device for generating steam for power, processing, or heating purposes; or a device for generating hot water for heating purposes or a hot water supply. Heat from an external com- bustion source is transmitted to a fluid contained within the tubes found in the boiler shell. This fluid is delivered to an end-use at a desired pressure, temperature, and quality. Boiler fuel: An energy source to produce heat that is transferred to the boiler vessel to gener- ate steam or hot water. Fossil fuel is the primary energy source used to produce heat for boilers. British thermal unit: The quantity of heat required to raise the temperature of 1 pound of liquid water by 1-degree Fahrenheit at the temperature at which water has its greatest density (approximately 39 degrees Fahrenheit). Capacity factor: The ratio of the electrical energy produced by a generating unit for the period considered to be the electrical energy that could have been produced at continuous full power operation during the same period. Capital cost: The cost of field development and plant construction and the equipment required for industry operations. Carbon dioxide: A colorless gas formed during the combustion of any material containing carbon; an important greenhouse gas. All energy production using combustion emits carbon dioxide, including driving vehicles, electricity production, and heating. It is also produced through the decomposition of organic matter in soils under oxidizing conditions. Carbon dioxide equivalent: A measure used to compare the emissions from various green- house gases on the basis of their global warming potential. For example, the global warming potential for methane over 100 years is 21. This means that emissions of 1 million metric tons of methane are equivalent to emissions of 21 million metric tons of carbon dioxide. Carbon offset: An action or activity (such as the planting of trees or carbon sequestration) that compensates for the emission of carbon dioxide or other greenhouse gases to the atmosphere. Carbon output rate: The amount of carbon by weight per kilowatt hour of electricity produced. Central chiller: Any centrally located air-conditioning system that produces chilled water to cool air. The chilled water or cold air is then distributed throughout the building, using pipes or air ducts or both. These systems are also commonly known as “chillers,” “centrifugal chillers,” “reciprocating chillers,” or “absorption chillers.” Chillers are generally located in or just outside the building they serve. Buildings receiving district chilled water are served by chillers located at central physical plants. Central physical plant: A plant owned by, and on the grounds of, a multibuilding facility that provides district heating, district cooling, or electricity to other buildings on the same facility. To qualify as a central plant, it must provide district heat, district chilled water, or electricity to at least one other building. The central physical plant may be by itself in a separate building or may be located in a building where other activities occur. Cogeneration: The production of electrical energy and another form of useful energy (such as heat or steam) through the sequential use of energy.

88 Airport Greenhouse Gas Reduction Efforts Combined heat and power (CHP) plant: A plant designed to produce both heat and elec- tricity from a single heat source. Note: this term is being used in place of the term “cogenerator” that was used by EIA in the past. CHP better describes the facilities because some of the plants included do not produce heat and power in a sequential fashion and, as a result, do not meet the legal definition of cogeneration specified in the Public Utility Regulatory Policies Act. Combustion: Chemical oxidation accompanied by the generation of light and heat. Compressed natural gas: Natural gas compressed to a pressure at or above 200–248 bar (i.e., 2,900–3,600 pounds per square inch) and stored in high-pressure containers. It is used as a fuel for natural gas-powered vehicles. Direct current: Direct current (DC) is the unidirectional flow or movement of electric charge carriers (which are usually electrons). The intensity of the current can vary with time, but the general direction of movement always stays the same. Direct current is produced by electro- chemical and photovoltaic cells and batteries. In contrast, the electricity available from utility mains in most countries is alternating current. Utility alternating current can be converted to DC by means of a power supply consisting of a transformer, a rectifier (which prevents the flow of current from reversing), and a filter (which eliminates current pulsations in the output of the rectifier). Electric generator: A facility that produces only electricity, commonly expressed in kilowatt- hours (kWh) or megawatt-hours (MWh). Electric generators include electric utilities and inde- pendent power producers. Electric power grid: A system of synchronized power providers and consumers connected by transmission and distribution lines and operated by one or more control centers. In the conti- nental United States, the electric power grid consists of three systems: the Eastern Interconnect, the Western Interconnect, and the Texas Interconnect. In Alaska and Hawaii, several systems encompass areas smaller than the state (e.g., the interconnect serving Anchorage, Fairbanks, and the Kenai Peninsula; individual islands). Electric power plant: A station containing prime movers, electric generators, and auxiliary equipment for converting mechanical, chemical, and/or fission energy into electric energy. Electric utility: A corporation, person, agency, authority, or other legal entity or instrumen- tality aligned with distribution facilities for delivery of electric energy for use primarily by the public. Included are investor-owned electric utilities, municipal and state utilities, federal elec- tric utilities, and rural electric cooperatives. A few entities that are tariff based and corporately aligned with companies that own distribution facilities are also included. Electricity generation: The process of producing electric energy or the amount of electric energy produced by transforming other forms of energy, commonly expressed in kilowatt-hours (kWh) or megawatt-hours (MWh). Federal Aviation Regulations (FAR) Part 77: Objects Affecting Navigable Airspace-Part 77, (a) establishes standards for determining obstructions in navigable airspace, (b) defines the requirements for notice to the FAA Administrator of certain proposed construction or altera- tion, (c) provides for aeronautical studies of obstructions to air navigation, to determine their effect on the safe and efficient use of the airspace, (d) provides for public hearings on the haz- ardous effect of proposed construction or alteration on air navigation, and (e) provides for establishing antenna farm areas. Feedstock: A raw material that can be converted to one or more products. General aviation: That portion of civil aviation that encompasses all facets of aviation, except air carriers.

Glossary 89 Generator nameplate capacity (installed): The maximum rated output of a generator, prime mover, or other electric power production equipment under specific conditions designated by the manufacturer. Installed generator nameplate capacity is commonly expressed in megawatts (MW) and is usually indicated on a nameplate physically attached to the generator. Geothermal energy: Hot water or steam extracted from geothermal reservoirs in the earth’s crust. Water or steam extracted from geothermal reservoirs can be used for geothermal heat pumps, water heating, or electricity generation. Greenhouse gases: Those gases, such as water vapor, carbon dioxide, nitrous oxide, methane, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, that are transparent to solar (short-wave) radiation but opaque to long-wave (infrared) radiation, thus preventing long-wave radiant energy from leaving Earth’s atmosphere. The net effect is a trapping of absorbed radia- tion and a tendency to warm the planet’s surface. Green pricing: In the case of renewable electricity, green pricing represents a market solu- tion to the various problems associated with regulatory valuation of the nonmarket benefits of renewables. Green pricing programs allow electricity customers to express their willingness to pay for renewable energy development through direct payments on their monthly utility bills. Ground loop: In geothermal heat pump systems, a series of fluid-filled plastic pipes buried in the shallow ground, or placed in a body of water, near a building. The fluid within the pipes is used to transfer heat between the building and the shallow ground (or water) to heat and cool the building. Ground power unit frequency converter: An electronic or electromechanical device that converts electrical current of one frequency to electrical current of another frequency. Com- mercial aircraft use 400 Hz power; therefore, a 50 Hz or 60 Hz to 400 Hz frequency converter is needed for use in the ground power unit used to power the airplane while it is on the ground. Ground support equipment (GSE): This equipment is typically associated with the servicing of aircraft during the airport turnaround process while the aircraft is parked at the gate. During this period, there are a number of tasks that are performed, including loading and unloading passengers and baggage, aircraft cleaning and maintenance, refueling and replenishment of pro- visions, and other similar services. Other common GSE functions pertain to the servicing and maintenance of the airside infrastructure and airfield of the airport. Heat pump (geothermal): A heat pump in which the refrigerant exchanges heat (in a heat exchanger) with a fluid circulating through an earth connection medium (ground or ground water). The fluid is contained in a variety of loop (pipe) configurations depending on the tem- perature of the ground and the ground area available. Loops may be installed horizontally or vertically in the ground or submersed in a body of water. HVAC: Heating, ventilation, and air-conditioning system; the system or systems that condi- tion air in a building. Installed cost: The up-front cost paid by the system owner to construct a generating system. Internal rate of return: A widely used rate of return for performing economic analysis. This method solves for the interest rate that equates the equivalent worth of an alternative’s cash receipts or savings to the equivalent worth of cash expenditures, including investments. The resultant interest rate is termed the internal rate of return. Inverter: A device that converts direct current electricity (for example, from a solar photo- voltaic module or array) to alternating current for use directly to operate appliances or to supply power to an electricity grid.

90 Airport Greenhouse Gas Reduction Efforts Irradiance: A measure of the intensity of the solar power recorded in W/m2. Kilowatt (kW): One thousand watts. Kilowatt-electric (kWe): One thousand watts of electric capacity. Kilowatt-hour (kWh): A measure of electricity defined as a unit of work or energy, measured as 1 kilowatt (1,000 watts) of power expended for 1 hour. One kWh is equivalent to 3,412 BTU. Landfill gas: Gas that is generated by decomposition of organic material at landfill disposal sites. The average composition of landfill gas is approximately 50% methane and 50% carbon dioxide and water vapor by volume. The methane percentage, however, can vary from 40% to 60%, depending on several factors including waste composition (e.g., carbohydrate and cellulose content). The methane in landfill gas may be vented, flared, combusted to generate electricity or useful thermal energy on-site, or injected into a pipeline for combustion off-site. Land lease: A long-term land lease, generally for the purpose of erecting a building or build- ings, or for constructing improvements to the land to be used by lessee. At the end of a lease, the land and all structures and enhancements revert to the owner. Land leases should follow the basic format of the hangar lease and include all of the same references to the airport’s rules, regulations, and minimum standards. The land lease price per square foot could vary by loca- tion, and possibly by the length of the term, and also may be connected to a business permit or a fixed-base operator lease. Large hub: Publicly owned airport providing scheduled passenger service with at least 10,000 passenger boardings in a calendar year, and which accounts for 1% or more of annual passenger boardings in the country. Lease: An agreement in which the owner of real property (landlord or lessor) gives the right of possession to another (tenant or lessee) for a specified period (term) and for a specified con- sideration (rent). Load shedding: The deliberate shutdown of electric power in a part or parts of a power- distribution system, generally to prevent the failure of the entire system when the demand strains the capacity of the system. Medium hub: Publicly owned airport providing scheduled passenger service with at least 10,000 passenger boardings in a calendar year and which accounts for between 0.25% and 1% of annual passenger boardings in the country. Megawatt (MW): One million watts of electricity. Megawatt electric (MWe): One million watts of electric capacity. Megawatt-hour (MWh): One thousand kilowatt hours or 1 million watt-hours. MMBTU: One million (106) British thermal units. Modules: Photovoltaic cells or an assembly of cells into panels (modules) intended for and shipped for final consumption or to another organization for resale. When exported, incomplete modules and unencapsulated cells are also included. Modules used for space applications are not included. Navigational aids (NAVAIDs): Any sort of marker that aids the traveler in navigation. In aviation, NAVAIDs include both visible markers and those identified with radar. Net metering: The practice of using a single meter to measure consumption and generation of electricity by a small generation facility (such as a house with a wind or solar photovoltaic system). The net energy produced or consumed is purchased from or sold to the power provider, respectively.

Glossary 91 Nonhub primary: Publicly owned airport providing scheduled passenger service with at least 10,000 passenger boardings in a calendar year and which accounts for less than 0.05% of annual passenger boardings in the country. Nonhub nonprimary: Publicly owned airport providing scheduled passenger service with between 2,500 and 10,000 passenger boardings in a calendar year. Nonprimary/general aviation: Public-use airports that do not have scheduled service or have less than 2,500 annual passenger boardings. Nonprimary/reliever: Designated by the FAA to relieve congestion at commercial service air- ports and to provide improved general aviation access to the overall community. These facilities may be publicly or privately owned. Obstruction: Any object or natural growth, terrain, or permanent or temporary construction or alteration, including equipment or materials used therein, the height of which exceeds the standards established in Subpart C of Federal Aviation Regulations Part 77, Objects Affecting Navigable Airspace. Off-peak: Period of relatively low system demand. These periods often occur in daily, weekly, and seasonal patterns; these off-peak periods differ for each individual electric utility. Operations and maintenance: A set of activities, most of them technical in nature, which enable power generation facilities to perform their task of producing energy in compliance with applicable rules and regulations. Payback period: The amount of time required before the savings resulting from your system equal the system cost. Peak demand: The maximum load during a specified period. Peak shaving: The process of implementing measures to reduce peak power demands on a system. Photovoltaic and solar thermal energy (as used at electric utilities): Energy radiated by the sun as electromagnetic waves (electromagnetic radiation) that is converted at electric utilities into electricity by means of solar (photovoltaic) cells or concentrating (focusing) collectors. Power purchase agreement (PPA): A contract between a buyer and seller of energy that obli- gates the party to deliver and pay for energy for a predetermined price and term. PPAs guaran- tee a future revenue stream and therefore can be an important component to securing project financing. Pre-conditioned air: Provides parked aircraft with air conditioning from a ground-based system, using outside filtered, cooled or heated air. Rebate program: A utility company-sponsored conservation program whereby the utility company returns a portion of the purchase price cost when a more energy-efficient refrigerator, water heater, air conditioner, or other appliance is purchased. Reliability (electric system): A measure of the ability of the system to continue operation while some lines or generators are out of service. Reliability deals with the performance of the system under stress. Renewable Energy Certificate (REC): REC represents the environmental attributes of elec- tricity generated through a qualifying renewable energy resource. One REC is issued for every 1 MWh of electricity produced by the qualifying source. Because renewable electricity fed into the electric grid is distributed according to physical laws rather than contractual agreements, RECs help account for who can claim the use of renewable electricity. A state renewable portfolio

92 Airport Greenhouse Gas Reduction Efforts standard (RPS) typically requires the utilities to procure a certain number of RECs to demonstrate compliance with their renewable energy requirement. RECs can be bought and sold as commod- ities in the market and are issued and tracked by various generation information systems (GIS) that operate within the U.S. electric grid. RECs are also known as green tags, green certificates, or tradable renewable certificates. Renewable energy resources: Energy resources that are naturally replenishing but flow- limited. They are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time. Renewable energy resources include biomass, hydro, geothermal, solar, wind, ocean thermal, wave action, and tidal action. Renewable Fuel Standard (RFS): Established by the U.S. Congress in laws enacted in 2005 and 2007 and administered by the EPA to increase the amount of biofuels in gasoline. Renewable natural gas (RNG): Also known as biomethane, a pipeline-quality gas that is fully interchangeable with conventional natural gas and thus can be used in natural gas vehicles. RNG is essentially biogas (the gaseous product of the decomposition of organic matter) that has been processed to purity standards. Like conventional natural gas, RNG can be used as a transporta- tion fuel in the form of compressed natural gas (CNG) or liquefied natural gas (LNG). RNG qualifies as an advanced biofuel under the Renewable Fuel Standard. Renewable Portfolio Standard (RPS): Requires utilities to use or procure renewable energy or renewable energy certificates (RECs) to account for a certain percentage of their retail elec- tricity sales—or a certain amount of generating capacity—according to a specified schedule. (Renewable portfolio goals are similar to RPS policies, but goals are not legally binding.) Most U.S. states have established an RPS. The term “set-aside” or “carve-out” refers to a provision within an RPS that requires utilities to use a specific renewable resource (usually solar energy) to account for a certain percentage of their retail electricity sales (or a certain amount of generating capacity) according to a set schedule. Return on investment (ROI): A performance measure used to evaluate the efficiency of an investment or to compare the efficiency of a number of different investments. To calculate ROI, the benefit (return) of an investment is divided by the cost of the investment; the result is expressed as a percentage or a ratio. Scope 1 emissions: Direct emissions from airport-owned or controlled sources. Scope 2 emissions: Indirect emissions from purchased electricity, heat, or steam. Scope 3 emissions: Indirect emissions from other sources related to the activities of the airport. Small hub: Publicly owned airport providing scheduled passenger service with at least 10,000 passenger boardings in a calendar year and which accounts for between 0.05% and 0.25% of annual passenger boardings in the country. Solar energy: The radiant energy of the sun, which can be converted into other forms of energy, such as heat or electricity. Solar thermal panels: A system that actively concentrates thermal energy from the sun by means of solar collector panels. The panels typically consist of flat, sun-oriented boxes with transparent covers, containing water tubes or air baffles under a blackened heat absorbent panel. The energy is usually used for space heating, for water heating, and for heating swimming pools. Tariff: A published volume of rate schedules and general terms and conditions under which a product or service will be supplied.

Glossary 93 Tax incentives: Tax incentives include tax credits, deductions, and exemptions. They can be applied to corporate, personal, property, and sales tax liability. These incentives are available in some states to individuals and organizations that purchase and install eligible renewable energy or energy efficiency equipment, or to construct green buildings. In a few cases, the incentive is based on the amount of energy produced by an eligible facility. Some states allow the tax credit only if a corporation has invested a minimum amount in an eligible project. Typically, there is a maximum limit on the dollar amount of the credit or deduction. In recent years, the U.S. federal government has offered corporate tax incentives for renewables and energy efficiency. Third party: Third-party transactions are arms-length transactions between nonaffiliated firms. Transmission line (electric): A system of structures, wires, insulators, and associated hard- ware that carry electric energy from one point to another in an electric power system. Lines are operated at relatively high voltages varying from 69 kV up to 765 kV and are capable of transmit- ting large quantities of electricity over long distances. Useful life: An estimate of how long one can expect to use an income-producing item in a trade or business setting. Useful life usually refers to the duration for which the item will be use- ful (to the business), and not how long the property will actually last. Waste materials: Otherwise discarded combustible materials that, when burned, produce energy for such purposes as space heating and electric power generation. The size of the waste may be reduced by shredders, grinders, or hammermills. Noncombustible materials, if any, may be removed. The waste may be dried and then burned, either alone or in combination with fossil fuels. Wood pellets: Saw dust compressed into uniform diameter pellets to be burned in a heating stove. Zero net energy (ZNE) building: An energy-efficient building in which, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy [Definitions were taken from the following sources: U.S. Energy Information Administration, National Renewable Energy Laboratory, Database of State Incentives for Renewable Energy, and several other Department of Energy and FAA documents and sources.]

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Airports in the United States are responding to the demand for increased air travel with sustainable development that incorporates more energy-efficient and lower-emission technologies. Funding for greenhouse gas (GHG) emissions-reducing technologies, such as electrification, alternative fuels, and renewable energy, has also become more accessible as technologies are proven to be safe, reliable, and cost-effective.

Newer strategies and programs to reduce GHG emissions reach beyond airport operations to incorporate the traveling public. These are among the findings in the TRB Airport Cooperative Research Program's ACRP Synthesis 100: Airport Greenhouse Gas Reduction Efforts. The report assesses (1) the state of practice of GHG emissions reduction initiatives at airports, and (2) the lessons learned to support the successful implementation of future GHG reduction projects.

The report also finds that large airports are taking the lead in moving beyond reduction strategies for their own emissions and tackling those produced by tenants and the traveling public by supporting the use of alternative fuels and directing passengers to airport carbon offset platforms.

It is clear that airports regard energy-efficiency measures to be the most effective practice to reducing GHG emissions. Smaller airports, in particular, are adopting new technologies associated with more efficient heating and cooling infrastructure and lighting systems because they decrease energy consumption and make economic sense. GHG reduction projects are being implemented by different types of airports across the industry because of the cost savings and the environmental benefits of the new technology.

Airports are actively benchmarking emission-reduction progress in comparison with similar efforts at airports around the world by using frameworks employed by the industry globally, such as the Airport Carbon Accreditation Program and the airport carbon emissions reporting tool (ACERT), to measure their GHG emissions.

Innovative approaches are allowing airports to address rapidly changing consumer behaviors, like those presented in recent years by transportation network companies (TNCs) such as Uber and Lyft. These policy-based solutions offer the potential for wider adoption as they enable airports to act without significant capital expenditures.

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