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12 The Impacted Community In other cases, the DOE has collaborated with other fed- eral agencies to conduct studies to assess potential impacts of Regulations have been developed to protect a resource (defined new energy technology. One example of this collaboration is in chapter two as airspace) and to protect a user group of the the research being undertaken by the Sandia National Labo- airspace (i.e., pilots and the customers they serve). It is logical ratories to assess the effects of glare from CSP projects. to ask about the community that is impacted by energy projects and what types of users exist. To supplement the various permitting documents and gov- ernment reports, experts in the field of assessing emerging The affected community starts with the commercial aviation energy technologies and their potential impacts on airports industry that operates from large and medium-sized airports and aviation were interviewed for this report, and their con- across the country. Airlines provide a passenger transportation tributions are discussed throughout. service for business and leisure that enhances businesses from each departure and arrival destination. Aircraft also transport As a result of a large volume of new energy proposals, a commodities, particularly perishables and express packages significant amount of analysis has been conducted on the types that require short delivery times. of impacts identified in this study. Some of these are summa- rized in the following sections. To assess impacts, these analy- Smaller general aviation (GA) airports across the country ses could be compared with regulatory performance standards. provide essential transportation between remote areas that are However, in most cases, a clear threshold of impact has not otherwise difficult to access by other means. GA airports are been promulgated. also home base for a large community of aviation enthusiasts who fly their own planes for recreational purposes. In addition, many GA airports operate flight training schools for teaching TYPES OF IMPACTS new pilots, while also supporting local airplane services from essential business activities such as crop dusting to entertain- The types of impacts identified during the preparation of ment activities such as sky diving and gliding. this report included: (1) physical penetration of airspace, (2) communications systems interference, (3) visual impacts Finally, heliports are used by helicopters serving a variety from glare, (4) wind turbine turbulence, (5) thermal plume of functions from medical flights to remote land surveying to turbulence, and (6) visual impacts of vapor plumes. metropolitan traffic reporting. Each project that is proposed that impinges on and degrades airspace has the potential to Physical Penetration of Airspace affect one or more of these user groups. Some objects exceed heights that penetrate aviation imaginary The Current Knowledge Base surfaces and thereby impact airspace. Any object that is 200 ft above ground level is determined to penetrate into airspace. Because many of the energy technologies assessed in this Objects that are less than 200 ft in height but within 20,000 ft report are being deployed primarily by private developers at of an airport runway longer than 3,200 ft (or 10,000 ft for a run- a larger scale in new geographic areas and at a more rapid way less than 3,200 ft) may still penetrate airspace depending pace, much of the existing information on potential impacts on relative distance to the airport. In addition, some structures is found in federal and state environmental permit applica- less than 200 ft above ground level, such as meteorological test tions submitted as part of regulatory approvals. Applicants towers, have been identified by local authorities as being a file EISs for projects subject to NEPA, which describe a potential hazard. variety of potential project impacts. As these reviews are distributed for broad public comment, interest groups and Airports are required to maintain vegetation, site new organizations across the social spectrum submit written airport development, and manage any temporary construc- comments about how the proposed project may cause negative tion activity to ensure that airspace around runways is clear impacts, prompting the administering agency (under NEPA of objects. Any proposed structure off-airport that is 200 ft it is the lead federal agency) to require the applicant to study in height and/or within 20,000 ft from an airport runway has the impact and report the findings. the potential to penetrate airspace. Applicants conduct a Section 14 CFR 77 (Objects Affecting Navigable Airspace) In some cases, federal authorities have recognized a poten- analysis to determine which structures are subject to airspace tially systemic problem associated with a certain technology review. Such projects are required to notify the FAA by filing and has commissioned an independent analysis to define the Form 7460, Notice of Proposed Construction or Alteration. potential impacts and assess the level of impact and potential Typical structures that impede 200 ft include large skyscrap- ameliorating circumstances. An example of this described ers, communication towers, and wind turbines (see Figure 8). later was when the U.S. Air Force expressed concern about Solar power towers and power plant exhaust stacks may also the impacts of large wind farms on the ability of the Air Force exceed 200 ft in height or may penetrate airspace with smaller to train pilots, thereby affecting "military readiness." structures if located closer to an airport.

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13 FIGURE 8 Physical penetration of airspace schematic (courtesy: HMMH). Communication Systems Interference determine locations that would not be suitable for structures based on their potential to either block, reflect, or disrupt Communication systems interference includes negative im- radar signals. pacts on radar, navigational aids (NAVAIDS), and infrared instruments. Although Global Positioning Systems that com- Off-airport solar projects are unlikely to cause radar inter- municate with satellites and limit the need for traditional ference compared with those proposed on-airport unless surveillance radar are being employed more widely and are located close to airport property and within the vicinity of expected to be the fundamental component of future navi- radar equipment and transmission pathways. However, when gational systems, the integrity of traditional radar facilities located near a radar installation, CSP projects can reflect radar remains central to the current operational environment. transmissions because of their metallic components. Radar interference occurs when objects are placed too close to a radar sail (or antenna) and reflect or block the transmission Visual Impacts of Glare of signals between the radar antenna and the receiver (either a plane or a remote location). Although it is possible for interfer- Glare occurs when sunlight causes a temporary visual impair- ence to be caused by other communication signals, more com- ment to an observer. Glare can be produced when looking monly it is caused by a physical structure placed between the directly at the sun, such as when driving in its direction after transmitter and receiver. NAVAIDS can be impacted similarly sunrise or sunset, or at any time of day when sunlight is returned to radar, but they include passive systems with no transmit- to the observer from a reflective surface. Surfaces that pro- ting signals. Impacts on infrared communications can occur duce glare include mirrors, metal roofs, still waters, and glass. because the solar collectors and receivers can retain and emit Smooth polished surfaces, such as glass, can cause a specu- lar reflection that is more direct and intense (see Figure 9). heat, and the heat they release can be picked up by infrared Reflections from rough surfaces become diffuse and result in communications in aircraft causing an unexpected signal. less of an impact. Solar PV, although designed to be absorp- tive of sunlight, can produce glare in certain instances because Communications interference can result from any of the of its glass surface. CSP projects that use mirrors have a energy technologies discussed in this report. Potential impacts greater propensity to produce glare. The concern here is that, increase with larger structure size (and cross section) and depending on the location of the solar project, glare could shorter distance to radar facilities. Large wind farms have gen- cause a momentary visual impairment to air traffic controllers erated the most problems and as a result have been studied the or pilots. most. Transmission lines can also cause interference resulting from electrical signals irradiating from the lines. Impacts from other technologies are primarily from the structure's mass and Wind Turbine Turbulence physical location blocking radar signals. Studies conducted during project siting may identify the location of radar trans- Turbulence occurs when air flow becomes chaotic and irreg- mission and receiving facilities and other NAVAIDS and ular. Although turbulence is typically caused by changing

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14 FIGURE 9 Specular and diffuse reflection schematic (courtesy: HMMH). weather patterns or by dramatic topographic variations, turbu- thermal plume rises causing upward moving turbulence. An lence can also be caused by man-made activities. The potential aircraft might pass well above the structure of an air-cooled effects of turbulence are of greatest concern when there is a condenser and become subject to the invisible turbulence sudden and unforeseen turbulence on a small aircraft caused without warning. by some great force. Turbulence associated with wind turbines is less an issue Visual Impacts of a Vapor Plume of predictability, as the turbulence potential can be visualized Vapor plumes produce a vapor cloud that can result in localized by the presence of the wind turbines and whether or not they visual impairment. Plumes are produced by large-scale emis- are spinning. The issue is more about understanding the dis- sions of heated water vapor typically from an evaporative wet tance that rotor-induced turbulence may occur from a wind cooling system associated with a power plant. Wet cooling turbine and what the degree of turbulence might be compared towers reject heat into the atmosphere by releasing water vapor. with other sources of existing natural and man-made turbu- The air leaving the tower is saturated with moisture and warmer lence. What is a safe distance for aircraft to travel downwind than ambient air producing a wet exhaust plume. The saturated of a wind turbine? exhaust plume may or may not be visible. During cool morn- ings in the fall or spring when the ambient air is moist cooling Thermal Plume Turbulence towers can add more water to the air, thereby saturating the air and adding water droplets resulting in fog. If the ambient tem- Thermal plume turbulence is caused by the release of hot air peratures are below freezing, the resulting water droplets could from a power plant equipped with a dry cooling system. The cause icing on nearby roadways and bridges surfaces.