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18 enough to be impacted particularly when making a particular The units should be rotated from stow away position to maneuver to a specific runway. To minimize the risk of this ready position before sunrise to limit potential inadver- impact, the CEC required a notification to pilots as a condi- tent glare. tion of its decision. Parabolic designs should consider using end caps to reduce glare that "spills" from the ends of the trough. Curtailment in facility operations can be prescribed dur- VAPOR PLUME VISUAL IMPACT ing periods when glare is expected to impact low-flying aircraft. Vapor plume is typically produced by power plants, includ- Flight procedures can be restricted during certain periods ing CSP and peaking power plants, which utilize an evapora- of the day when glare may occur. tive wet cooling system. Whereas dry cooling transfers heat to County zoning ordinances may be put into place to limit the air which rises above the system, evaporative wet cool- glare-producing structures in airport influence zones ing produces steam as heat dissipates through evaporation. (El Dorado County, California 2009; Clallam County, The mechanics of the two heat transfer systems is similar but Washington 2010). the impacts are very different primarily because a vapor plume can be seen whereas a thermal plume cannot. Visible impact from steam is not expected to occur from air-cooled con- SOLAR ENERGY IMPACT EXAMPLES densers because the heat is cooled by air convection and not water (Solar Millennium 2010). The following section describes examples of solar energy impact. Wet cooling has been the preferred cooling system owing to enhanced cooling efficiency (compared with dry cooling) and decreased cost. In the past, wet cooling was accomplished Blythe Solar Power Plant with once through cooling, but the impacts of heated dis- The Blythe Solar Power Plant is a proposed 1,000 MW CSP charge to water bodies encouraged the development of evap- facility to be located in California's inland desert on land orative wet cooling. The majority of new fossil fuel plants owned by the BLM. The project will utilize parabolic trough employ evaporative wet cooling (NREL 2010a). It has been technology that reflects sun from each trough device to a employed at hundreds of power plants across the country, receiver tube. The heat transfer fluid in the tube is raised to particularly those built in more recent years. For CSP proj- 750F and then piped through heat exchanges used to cre- ects that are challenged to compete with traditional sources ate steam that drives a traditional steam turbine generator to of electricity on price, use of wet cooling has been the con- produce electricity. The Blythe Project provides a current vention with all operating projects as of March 2010 (SEIA example of the regulatory evaluation for a CSP facility. In 2010). However, as a result of environmental concerns over September 2010, the CEC issued its Decision on the Appli- the scarcity of water, particularly in desert areas where CSP cation for Certification for the Blythe Solar Power Project. In projects are located, newer projects are being forced to exam- its review, the CEC assessed many of the potential impacts ine dry cooling (CEC 2010b). of CSPs identified in this report. The following is a list of Steam released from power plants occurs near airports in conditions in the CEC's decision to mitigate impacts: Pennsylvania. Pilots fly through a vapor plume on approach to Runway 9 at Perkiomen Valley Airport, Pennsylvania Proponents have comments or notations inserted in the (A. Tezla, Mead and Hunt, Inc., personal communication, appropriate Aeronautical Charts, Airport/Facilities Direc- 2011). The Limerick Nuclear Power Plant is also close to tories, and Notice to Airmen publication to identify poten- the Pottstown Municipal Airport (PTW). Steam rises from the tial hazard from glare and thermal turbulence. cooling towers of the Three Mile Island Nuclear Plant into the Mirrors are (1) brought out of stowage before sunrise approach path at Harrisburg International Airport (MDT). It and are aligned to catch the first rays of the morning sun, is possible that aircraft are less affected by vapor plumes (than and (2) returned to stow position after sunset. thermal plumes) because they are a recurring feature that can Mirror function is continuously monitored by operators be seen allowing pilots to make adjustments as needed. and system controllers. The system is designed to automatically turn a malfunc- tioning mirror east so there is no reflection from the sun MITIGATION OPTIONS as it moves west. The owner develops procedures to move mirrors east to The following mitigation options have been considered in min- avoid glare. imizing the impacts of concentrated solar power on aviation: Mirrors in the southern portion of Units 3 and 4 are not to be rotated off axis during daylight hours when the For parabolic trough plants, use nonreflective or diffuse azimuth angle of the sun is east or north of east. materials or coatings (e.g., paint) for bellows shields Specific procedures for documenting, investigating, eval- located every few meters at joints between heat collect- uating, and resolving (if feasible) public complaints about ing elements. glare are to be developed.

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19 CEC's decisions incorporated the following conditions to avoid impacts on aviation. 1. Preparation of a Heliostat Positioning Plan that would avoid potential for human health and safety hazards from solar radiation exposure. The plan should identify the heliostat movements and positions (including reasonably possible mal- functions) that could result in potential exposure of observers at various locations including in air- craft, motorists, pedestrians, and hikers in the Clark Mountains to reflected solar radiation from heliostats. The plan should describe how programmed heliostat operation would avoid potential for human health and safety hazards at locations of observers as attrib- utable to momentary solar radiation exposure greater FIGURE 13 Solar PV at Oakland International Airport, California than the maximum permissible exposure of 10 kw/m2 (courtesy: HMMH). (for a period of 0.25 second or less). Preparation of a monitoring plan that would: (1) obtain field measurements in response to legitimate com- Oakland International Solar PV Project plaints; (2) verify that the Heliostat Positioning Plan would avoid the potential for human health and safety In 2007, the Port of Oakland entered into a lease agreement hazards including temporary or permanent blindness with a private solar developer to construct a solar PV proj- at locations of observers; and (3) provide require- ect on airport property. Because the project was proposed ments and procedures to document, investigate, and on airport property, the FAA was responsible for approving resolve legitimate complaints regarding glare. The the lease and evaluating potential impacts of the project on monitoring plan should be coordinated with the FAA, aviation. The Port selected a lease site close to the runways U.S. Department of the Navy, California Depart- because the land was otherwise not useable for most avia- ment of Transportation, California Highway Patrol, tion activities. To prevent a physical impingement of air- and Clark County Department of Aviation in rela- space, the angle of the row of solar panels closest to the tion to the proposed Southern Nevada Supplemen- runway were pitched close to flat (see Figure 13). To avoid tal Airport and be updated on an annual basis for the any potential interference with communication facilities, first 5 years, and at 2-year intervals thereafter for the the solar panels were required to preserve a 500-ft setback life of the project. from the aviation surveillance radar. Glare was determined 2. Preparation of a Power Tower Luminescence Moni- not to be a hazard from this project, although similar pro- toring Plan to provide procedures to conduct periodic jects at other airports have required in the field studies using monitoring and to document, investigate, and resolve solar panels at proposed project locations to assess impacts complaints regarding distraction effects to aviation, on the control tower. vehicular, and pedestrian traffic associated with the power towers: Evaluate the effects of the intensity of the luminance Ivanpah Solar Electric Generating Facility of light reflected from the power tower receivers 90 days after commencement of commercial oper- The Ivanpah Solar Electric Generating Facility is a 370 MW ations, and after 5 years, as well as after any signif- CSP facility utilizing power tower technology proposed in icant design or operational modification, or after a the Ivanpah Valley of California on land owned and man- significant complaint. aged by the BLM three miles west of the Nevada border. Coordinate monitoring protocol and results with The project will consist of three tower facilities, each with agency stakeholders. heliostat mirrors used to focus the sun's energy to boil 3. Lighting of the power towers as required by FAA under steam and drive a steam turbine. Power plant 1 is a 120 MW Part 77 Review. facility. Power plants 2 and 3 are each 125 MW. The power 4. Notification of pilots in the area about potential haz- towers will be 459 ft tall. The facility will be cooled using ards associated with thermal turbulence. Notification air-cooled condensers that are approximately 115 ft tall should indicate that a hazard could occur up to 1,350 ft (CEC 2010d). The CEC issued separate decisions on each above ground level. Request that the FAA prohibit of the three individual projects in September 2010. The flights over the facility at or below the 1,350 ft altitude.