Technical assessment of captive solar power plant: A case study of Senai airport, Malaysia

Renewable Energy 152 (2020) 849e866

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Technical assessment of captive solar power plant: A case study of Senai airport, Malaysia S. Sreenath a, K. Sudhakar b, c, *, A.F. Yusop b a

Renewable Energy and Energy Efficiency Research Cluster, Universiti Malaysia Pahang, Malaysia Faculty of Mechanical and Automotive Engineering Technology, Universiti Malaysia Pahang, 26600, Malaysia c Energy Centre, Maulana Azad National Institute of Technology Bhopal, India b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 6 October 2019 Received in revised form 24 December 2019 Accepted 23 January 2020 Available online 28 January 2020

Solar PV system in the airport environment is a relatively new application. Unlike land-based solar systems, the site selection for the airport-based PV power plant is a complicated process and lacks proper methodology. The objective of this work was to develop a general sitting procedure for an airport-based solar PV system and identify ideal sites for solar farms in Senai International airport, Malaysia. Feasible sites were selected with due consideration to airport and aviation compatibility constraints. Next, suitability of such selected sites is assessed based on environmental impact and proximity to electrical infrastructure. Using glare prediction software, the adherence to FAA’s solar interim policy is assessed. Eleven (11) sites which lie within the airport are chosen for the study. The duration of glare from sites 2, 3, 4, 6 were 1125, 4724, 3805, 1125 min receptively. As a result, design parameters are changed for these sites. The results of the study showed that the solar PV potential and theoretical energy generation from the selected sites of the airport were 12.50 MW and 16,745 MWh respectively. The knowledge on the suitability of sites and prior glare assessment increases the level of confidence to airport stakeholders and project developers. © 2020 Elsevier Ltd. All rights reserved.

Keywords: Airport Glare impact PV potential Site suitability Solar

1. Introduction Deployment of the solar PV power plant is increasing across the world and it can be attributed to factors such as a reduction in the cost of solar PV module, awareness on global warming, uncertainty in fossil fuel price [1]. In this regard, a variety of supporting policies such as tax reduction, accelerated depreciation, viability gap funding, schemes such as compulsory green power purchasing, renewable energy portfolio standards is implemented by governments in respective countries [2]. This solarising wave reached the airports which occupy vast vacant spaces. The intersection of solar energy applications and the aviation sector has been in limelight over the past few years. Due to the availability of vast unused open spaces on land and buildings along with intensive use of electricity, the relevance of implementation of solar PV technology is huge in the airport environment. Airport managers are keen to generate green power from their land in view of benefits from the expanding

* Corresponding author. Faculty of Mechanical and Automotive Engineering Technology, Universiti Malaysia Pahang, 26600, Malaysia. E-mail address: [email protected] (K. Sudhakar). https://doi.org/10.1016/j.renene.2020.01.111 0960-1481/© 2020 Elsevier Ltd. All rights reserved.

solar market and financial advantage such as revenue generation through lease payments, cost savings from reduced electricity cost and stabilized electricity price. These solar initiatives can also showcase the environmental stewardship of airport administration and it will be visible to millions of passengers or people who visit the airport [3]. In addition, airport solar projects are in line with carbon emission reduction programs of the state. Xu and Deng estimated that the total sunshine energy from 29.40 km2 area of the new Beijing International airport is about 40 billion kWh. It can be concluded that energy from a few percentages of the land area is enough to fully power airports, especially smaller ones [4]. In a case study on Brazilian airport, conducted by Ruther et al., it was mentioned that the Florianopolis airport can meet its 1.5MWp electricity needs through proposed building-integrated solar PV systems [5]. Airports are optimal locations for renewable energy generation such as solar PV which can contribute to at least partial supply of its energy needs. A word of caution is to ensure the safety standards of the airport [6]. The first notable solar PV project in the airport started operation in the early 2000s as per the unknown published document. Slowly, several airports adopted PV energy to meet its electrical energy requirement. Solar PV systems in airport

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Nomenclature As CUF o C ETG ft kW kV km2 MWh MW MWp Min m2 m/s Ps W/m2

Solar Area Capacity Utilisation Factor Degree Celsius Theoretical Energy generation Feet Kilowatt Kilovolt Square Kilo meter Mega Watthour Megawatt Peak Megawatt Minutes Square meters meter per second Solar PV potential Watts per Sq. metre

property can be either: ground-mounted (mainly on unused sections of the airfield), building mounted (mostly rooftop) or canopy mounted (above vehicle parking lots). Since the airport boundary covers thousands of square kilometers of land, several potential solar sites can be chosen within the perimeter of airport property. The typical location on airport premises was ground-mounted solar PV which is suitable in the areas isolated or remote from existing aviation facilities. Opportunities for solar PV installations is considerably high in the unused area around airfield. 1.1. Effect of glare on the observer’s visibility However, solar PV projects raise concern on the proper operation of airports and may dilute the primary mission to ensure safe and efficient air travel. If not properly sited and designed, such projects will usher scrutiny and comments from many administrative spheres. If sited closed to certain airport facilities, there are chances for penetration of PV into airspace, interference with communication systems and occurrence of glare hazard. Agencies and institutions related to the aviation sector such as the Federal Aviation Administration (FAA), Civil Aviation Authority (CAA) of countries such as the UK, Malaysia, International Civil Aviation Organisation (ICAO). Highway authority and military department have raised concerns about the glare impact due to reflection from solar PV installations. Reports citing National Highway Traffic Safety Administration (NHTSA) data estimate that solar glare causes nearly 200 fatalities and thousands of accidents involving motor vehicles each year [7]. The “Technical Guidance for Selected Solar Technologies at Airports” was released by FAA in November 2010 in wake of a growing number of proposals for new airport solar projects. It was based on the learning experiences from the first phase of solar projects that were built in airport property. Till that time, the reports of glare impact from airport installation was not known. Ho et al. [8] found a methodology to measure the impact of glare hazard on the basis of the magnitude of reflection and subtended angle. Subsequently, they developed a glare prediction software named as Solar Glare Hazard Analysis Tool (SGHAT). The glare analysis of the project was not hazardous [9]. The tilt and orientation of the PV module can influence the occurrence of glare. Air Traffic Control (ATC) tower is particularly at risk due to its strategic location and navigational purpose. In 2012, solar PV modules are

Abbreviations ARP Airport Reference Point ALP Airport Layout Plan ASR Airport Surveillance Radar ATC Air Traffic Control BIPV Building Integrated Photo Voltaic BAPV Building Applied Photo Voltaic CAA Civil Aviation Authority CNS Communication Navigation Surveillance FAA Federal Aviation Administration GHI Global Horizontal Irradiation IATA International Air Transport Association ICAO International Civil Aviation Organisation NAVAIDS NAVigational AIDS NHTSA National Highway Traffic Safety Administration OFA Object Free Area PV PhotoVoltaic RPZ Runway Protection Zone SGHAT Solar Glare Hazard Analysis Tool SPV Solar PhotoVoltaic

fixed on the top of a parking garage in Manchester-Boston Regional Airport created an issue. The glare occurrence was noticed on air traffic control tower (ATCT) and it was considered as the first reported observation in this scenario. Sukumaran and Sudhakar carried out the general design of the 2 MW solar PV plant proposed in the property of Raja Bhoja International airport. In this academic work, it was reported that the impact of glare on airport/aircraft operation must be analyzed round the year preferably using computer-aided software. In addition, they have assessed the performance of the proposed plant using simulation software. Since the chosen sites for solar PV power plant in Barnstable Municipal Airport (HYA) is situated near to runway, glare assessment was carried out which in turn resulted in an adjustment to a solar array so as to resolve the issue and obtained no hazard determination from FAA [10]. 1.2. PV’s penetration into the airspace In Oakland airport, the selected PV site is located close to the runways to utilize the land which is not suitable for most aviation activities. The main problems related to airport solar PV sitting in RPZs are the risk to the solar facility owner in case of aircraft derailing. As per an update to the airport design advisory circular (released in 2012), the removal of all objects from the Runway Protection Zone (RPZ) is desirable. In order to avoid physical penetration into navigational airspace, the tilt angle of the row of solar PV modules nearest to the runway can be kept horizontal (0
). The 6 MW ground-mounted solar PV system in Lakeland Regional airport is installed near the end of the runway and occupies 43 acres of airport property. Indianapolis Airport has a considerable land area that is not suitable for aviation purposes. A part of land parcel was utilized to install a 22 MW solar PV system spanning over 162 acres, thereby making it one of the largest airport solar systems in the world [11]. 1.3. Impact on CNS facilities Even for a PV project installed beside the fence of Phoenix airport, FAA was concerned about radar interference during the airspace review process [12]. A setback of 500feets and 250feets from the transmitter of communication systems are applied for

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solar PV systems in Oakland (OAK) and Bakersfield (BFL) respectively [13]. To prevent any potential interference with communication facilities, it is suggested to keep a 500 feet setback from the airport radars. In addition, there can be restrictions during the construction which can escalate the installation cost. It is usually associated with a small and busy airport. In wake of the implementation of a rooftop PV system (650 kW each) on the Terminal building and 2 MW solar plant on carport structures, San Diego County Regional Airport Authority built a 12 kV microgrid in San Diego airport to reduce the power transmission loss and to ease the management of electrical infrastructure in airport property. The land-based solar PV system in Denver airport was erected on deep drilled piers because of local clay soil which in turn increased the project cost. In San Diego airport, available land for lay down and storage is minimal which in turn affects the mobilization and preparation of construction operations. In addition, background checks and training were required for the construction crew due to regulated on-field access, which escalated the completion time and project costs. 1.4. Studies of PV in airport Hermawan and Karnoto [14] carried out the feasibility study for the proposed 250 kWp rooftop system in Kalimarau airport building and its energy output, economic performance and carbon mitigation estimated using mathematical formulas. Nguyen et al. [15] carried out a feasibility study of solar PV systems in a small airport. As a result of which, 3.3 MWdc solar system was sited and designed with due consideration to glare hazard and airspace regulations. It was understood that Anurag et al. [16] have carried out an in-depth study on the area of airport-based solar photovoltaic systems and have framed a generalized design procedure for such systems. Zomer et al. [17] carried out the site selection of building integrated and building applied solar PV systems (BIPV and BAPV) in the rooftop of Brazilian airports on the basis of shading analysis, solar insolation and architectural integration. Sites for the 1 MW solar PV system in Tucson airport were chosen in such a way that it receives abundant sunshine, reduces the loss of parking spaces, has an aesthetically pleasing look [18,19]. After an in-depth sitting analysis, a land parcel was selected on Illinois airport property due to its low value and unsuitability for future aeronautical or commercial activities. Since the site was close to approach area of runway, FAA was contacted in the early stages of the project to ensure that the PV project will not impact navigation in terms of glare occurrence, communication interference etc. In all these pieces of literature, the authors did not describe about proper and clear methodology. There is a lack of clarity in the significance of sitting factors especially glare assessment. 1.5. Objective of the study From the above-mentioned case studies, it can be concluded that proper site selection and prior glare assessment is important for the successful operation of a solar PV system in airport premises. The present literature lacks an in-depth study of on-site selection procedures for airport-based solar PV projects. There is a need for the development of general siting guidance for such projects which can be useful for aviation stakeholders. Since glare prediction from tracking systems is complex, fixed-tilt solar systems are only considered in the present study. This present work aims. 1. To formulate a general procedure of site selection in airport premises for the ground-mounted captive solar PV system.

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2. To estimate the solar PV power potential with due consideration of various constraints in airport and aviation regulations. 3. To analyze the technical feasibility of a sitting solar PV plant at Senai International airport located in Malaysia as a case study. 2. General site selection criteria Factors such as solar resource, shading, climate, topography, etc must be considered during site selection of solar PV plant which turns affect the energy generation and lifetime of the solar plant. Fig. 1 shows different constraints to be studied during the site selection of the solar PV system. 2.1. Solar resource availability An important factor that decides the profitability of the solar PV system is the sunshine availability which is often measured in terms of Global Horizontal Irradiation (GHI). Akash and Sudhakar described that the conversion efficiency of the solar module depends on irradiance levels and module temperature [20]. The energy yield (kWh/kWp) from solar PV plant increases with the solar insolation in that location. In the performance assessment conducted by Kumar and Sudhakar, it was mentioned that the site at Ramagundam receives good solar radiation of 4.97 kWh/m2/day [21]. The common method to assess the availability of solar resources is using solar maps which is based on long term averaged data and vast area coverage [22]. 2.2. Shading and soiling aspects PV module shading: Since the small area of shade on the PV module can significantly reduce the energy output, accurate sitting is important to reduce shading loss. Shadow mainly may occur from rows of PV array (mutual shadings), obstruction near to location such as trees, buildings or overhead cables and far horizons such as mountains or buildings. The site should be free from shading of trees or buildings especially located in the south of the PV array [20]. In addition, any shading that may occur due to future construction or growth of vegetation must be considered. If zero shading is not possible, special attention to minimize the shading is provided while assessing the suitability of the site. Partial shading and dirt accumulation lead to capture loss in SPV systems [23]. Since the sun’s path through the sky change with seasons, proper shading analysis need the use of a full sun path diagram for the location. PV array soiling: If PV modules are covered by particulates/dust, the efficiency of solar PV plants reduces. The reduction in efficiency is very high for the PV module located in the soiling condition [24]. The issue of soiling loss is severe in deserts or regions with loose sediment soil [25]. For a 20 kWp solar plant in South India, the increase in energy production after the cleaning of the PV array is about 2% [26]. Factors such as vehicular traffic, building activities, agricultural operations, dust storms, birds area must be considered during site selection. 2.3. Weather aspects The weather (climate) condition prevailing in the site can affect the energy output from solar PV plants. It was observed that the climatic condition, site location, and system design are the deciding factors for the optimum performance of 281 kWp solar plant in an International airport, Lesotho [27]. The rating of PV modules is given at standard test conditions. However, PV module performance varies with solar irradiation, temperature, shading etc experienced in the field. The main factors affecting the conversion

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Fig. 1. General sitting constraint of a land-based solar PV plant.

efficiency are module temperature, irradiation and wind velocity. In the case of crystalline silicon solar panels, a lifetime of good quality modules is more than 25 years. But a higher level of degradation may happen initially. A two-step power warranty (90% until 10 year and 80% until 25 year) has been the historical industry standard. In practice, the module degrades to 91% of its nominal power in the first year. In addition to good solar resources, the site should not experience extremes of weather conditions. The weather events that have to be considered include:  Flooding: Under this condition, damages occur to PV modules, electrical equipment placed close to ground level. Also, there are chances for the erosion of support structures and foundations depending on geotechnical conditions.  Wind speeds: The mounting structure of the solar PV plant cannot overcome stress from winds beyond a limit. Thus, the risk of high wind events exceeding the plant specifications has to be assessed. In this regard, solar PV systems located close to the airport runway need stronger mounting systems. Also, those locations that experience high wind speeds must are.  Snowfall: Snow setting can reduce the electricity generation and cause extra weight to module mounting structures. Special PV modules and support structures are needed in such areas which can cause additional expense. So a site that receives frequent snowfall may not be suitable for the installation of the solar PV plant.  Temperature: The power conversion efficiency of solar PV modules decreases with a rise in ambient temperature. Special design strategies have to be employed for solar PV plant installation in a hotter climate. For example, PV modules with

low-temperature coefficient perform better at a higher temperature. Other than these factors, air pollutants may scatter sun rays which in turn decreases resource irradiation. High humidity in the atmosphere reduces the performance of solar modules due to the fact that water vapors condense over the surface during night time [20]. Particulates from industries and transport emissions such as sulfur, nitrogen and higher levels of salt content can cause corrosion of solar plant components.

2.4. Landscape aspects Land use pattern: Since vast areas of land are needed for solar PV plants, the type of land cover is an important criterion [28]. reported that agricultural, forest and low vegetation land is not suitable for siting solar power plants. It is advised to avoid the use of fertile agricultural land for solar energy production. Sites having low revenue value are ideally suited for solar PV plants. Previously developed sites or brownfields are the best locations for solar PV plants. Topography: Certain topography makes installation simpler and reduces the cost of technical modifications in mounting structures thus saving installation cost and time. Higher elevation areas (more than 2000m) (due to the increase in the transportation and transmission cost), as well as steep slope areas (greater than 15
), were excluded during the site assessment in Sweden [29]. Flat site or a slight south-facing sloped site in the northern hemisphere (vice versa) is desirable for solar PV plants [22]. reported that the slope thresholds for solar PV farms are 3% and 5% based on a literature

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survey. Geotechnical conditions: Certain sites possess the risk of seismic activity, landslip, ground subsidence, historical mining, clay heave etc. A geotechnical survey may be carried out to assess such risk as well as groundwater level, soil resistivity, load-bearing properties, presence of rock. This helps in the steady operation of a solar PV plant and in deciding the design for foundation and module mounting structures. 2.5. Vegetation and ecological aspects If the project site includes environment resources, it may prohibit the project development in certain sites or may make the construction costlier and time-consuming. These solar projects are subject to review under the national environmental policy, and demonstrate that environmental impact is avoided, minimized and mitigated [30]. The information on environmental resources is available on various online sources (Wetland mapping, Geographic Information Systems) and through wetland surveys. This helps to avoid depletion of land natural resource and potential permitting delays. 2.6. Electrical infrastructure accessibility The proximity of electrical infrastructure to the solar project site reduces transmission cable cost and cable losses. Thus the feasibility of interconnecting the PV system of different installation sizes to the existing electrical infrastructure network has to be studied. Detailed GIS layer showing the on-site electrical infrastructure network is available with airport authorities. The details of location and capacity of vaults, transformers and meters are looked for in this regard. A mismatch between PV production and electricity consumption cannot be fully compensated. SPV may not able to shave the peak load at certain times which makes it necessary for the use of different generation technologies. The high penetration levels of power generation may cause voltage problems at the node of grid fed at certain circumstances such as the feed-in of PV is distributed over the whole grid and the decentralized generation exceeds the total load of the distributed grid. 3. Airport specific sitting criteria Project sites for solar PV systems were chosen based on the physical characteristics of the airport (airport master plan, environmental resources, and electrical infrastructure). The airportrelated constraints depend on the regulations by the International Civil Aviation Organization (ICAO) and corresponding national aviation authority [31]. The regional regulations are often stricter than those of ICAO. In addition, a review is needed to identify areas of airport property where the non-aeronautical use (solar generation) may be acceptable either based on the existing use designations on the ALP or a reasonable update to re-classify an area currently identified as aeronautical use to non-aeronautical use. These sites are then evaluated for their glare compatibility with airport sensitive receptors [32].

ground staff or air traffic controllers. As per FAA’s Federal Aviation Regulation (FAR) part 77, an object is considered as an obstruction to safe air maneuver if its height is greater than 200 ft above the ground level or established airport elevation (whichever is higher) and located within 3 nautical miles of the established reference point of an airport. Also for each additional nautical miles from the Airport Reference Point (ARP), a 100 feet increase in height is permitted to a max height of 500 ft up to 6 miles). Fig. 2 depicts for airports having runway length more than 3200 feet. OA ¼ 3 nautical miles, OB ¼ 4. OC ¼ 5, OD ¼ 6). Concentrating solar power towers (can be over 400 ft), power plant stacks and parabolic cooling towers (usually higher than 200 ft) can be an obstruction to navigational airspace if located within the airport premises (in most cases). For other structures under 200 ft. (e.g., drill rig or transmission tower), a physical penetration will occur only when it is located relatively proximity to an airport. Unlike thermal power plants and wind turbines, solar PV systems do not cause obstruction due to its low height profile and hence can be developed within 3 nautical miles from the ARP. Apart from the height limit of 200 ft, any developments within 3 nm from ARP must not penetrate the imaginary airspace. Imaginary surfaces extend out from the runway in a manner that reflects where aircraft are likely to fly. It also accommodates unforeseen aircraft maneuvers. Imaginary surfaces in the airspace around an airport as per Part 77 is given in Table 1. The height of the imaginary surface above the ground is lowest near the runway (less than 1m) and increases as one moves away from the runway. Hence solar PV installation near runway must be done with extra caution. Solar development is concerned, imaginary surfaces closer to the runway are relevant. So the surfaces namely (1) Primary (2) Approach, (3) Horizontal, (4) Transitional are shown in Fig. 3.

3.2. Interference to CNS facilities The physical barrier, electromagnetic waves and its frequency bands from the PV energy facilities may interfere with the Communication Navigation Surveillance (CNS) systems installed in airport areas. In Chapter 6 titled “Airport Design”, FAA Advisory Circular (AC) 5300e13, the critical areas for common CNS facilities located on an airport are defined [34]. The airport sponsor is responsible for limiting the potential for inference with communication, navigation, and surveillance (CNS) facilities in siting a proposed solar energy system. The proper operation of communications systems may be affected by the emission of electromagnetic waves from metallic parts of the PV system, solar inverters or due to physical obstruction between the communicator and receiver.

3.1. Airspace protection aspects All unused or vacant land in the airport cannot be sited for the installation of solar PV modules. The visibility of air traffic controllers and pilots can be affected by the height of solar PV mounting. Any object (including structures, trees, movable objects, and even the ground itself) that penetrates into any one of the predefined airspace surfaces is considered an obstruction [33]. For example, the PV module may block the line of sight of airport

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Fig. 2. Obstructive surfaces in airport environment

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Table 1 Airport imaginary surfaces and its definition. Imaginary surfaces

Definition

Maximum height limit (m)

Primary Approach Horizontal

Aligned (longitudinally) with each runway and extends 200 ft (61m) from each runway end Longitudinally centered with the runway and extends beyond the primary surface An imaginary plane that is parallel to the runway and situated 150 ft (45.72m) above the established airport elevation. Surface connecting approach and horizontal surfaces

0 (ground level) For every 7m length, 1m height. (7:1 slope) 45.72m

Transitional

For every 50m length, 1m height. (50:1 slope)

To ensure that the airport operates a safe and efficient manner, the placement of structures is restricted in certain areas especially near runway and taxiway as per FAA’s Airport Design (AC) 150 5300-13. Some of the relevant safety zones where non aeronautical use is restricted are Object Free area, Runway safety Area, Runway Protection Zone, Taxiway Safety Area and Taxiway Object Free area (See Fig. 3).

Fig. 3. Imaginary surfaces in the airport area.

Sitting of energy technologies closer to radars can cause a physical barrier and thus may modulate signals from radars [35]. An Airport Surveillance Radar (ASR) which helps in directing aircraft flying in and out of the airport, has a 1500-foot radius buffer to prevent potential obstructions. Very high frequency (VHF) Omnidirectional Range (VOR) radar needs a 1000-foot buffer. For other NAVAIDS, a 500-foot buffer is suggested to keep during the site selection process. Once the location of radars is known, the buffer zones are marked so that those area can be excluded while site selection. The effect of infrared waves emitting from solar PV modules on the operation of NAVAIDS is neglected in this study. 3.3. Consistency with airport activities Airport Layout Plan and Master Plan are helpful in assessing the consistency with aviation activities. The location, the applicable clearance and dimensional information of existing airport facilities can be obtained from ALP. Airport Master Plan showcases the longterm development of an airport. It includes drawings, data descriptions and a detailed implementation plan. Airport Layout Plan and Master Plan must be studied in order to identify areas of airport property allocated for aeronautical use, existing airport infrastructure and for future development such as the extension of the runway, new terminal building. Those sites where non aeronautical use is acceptable are found out. In certain cases, a reasonable update to reclassify an area currently identified as aeronautical use to non-aeronautical use is possible. The ALP may contain information about the revenue generation properties (specific land parcels) within the airport boundary. The proposed solar PV installation must be consistent with the airport layout and master plans which ensure that the airport facilities can be expanded without demolition. The typical locations on airport property for solar PV systems include airfield areas isolated or away from existing aviation facilities and airport infrastructure (building roofs, surface parking) provided that solar is consistent with existing aeronautical supporting uses.

 Object Free Area (OFA): No fixed object shall be in this zone (also called as runway strip) unless it supports air navigation or aircraft safety. Its area is determined by the code of the airport. Runway strip extends 60 m from the end of runway and 75 m (code 1 or 2 airports) or 150 m (code 3 or 4 airports) from each side of the runway centerline.  Runway Protection Zone (RPZ): It is a trapezoid-shaped area at the end of the runway strip which is allocated to enhance the protection of passengers, ground staff and assets. RPZ is also called as a (translational) obstacle-free zone which extends out from the edge of the runway strip (lengthwise) up to the inner horizontal surface positioned 45 m above ground level. The slope from the edge of the runway strip at ground level up is 33% for larger airports and 40% for smaller (7:1). Its dimensions depend on approach visibility and the code of the airport. Runway safety area falls within the Runway Protection Zone.  Taxiway Safety Area/Taxiway strip: Area adjacent to the taxiway and the length varies with runway code. For an airport with a runway code 4E or F, the taxiway strip should not be less than 115 m wide. No objects should be placed in the taxiway strip. The identification of areas with respect to airport constraints is shown in Fig. 4. 3.4. PV glare impact For each selected site, compliance with glare hazard standards must be evaluated as per aviation regulations with the help of a modelling tool. FAA Order 7400.2 00 Procedures for Handling Airspace Matters” discusses reflectivity concerns in airport areas. The ocular impact must be analyzed over the entire calendar year in 1-min intervals from when the sun rises above the horizon until the sun sets below the horizon. The values of direct normal irradiance, PV panel reflectivity, its optical properties, ocular parameters and orientation is needed for glare prediction [36]. If glare is observed, the position and duration of solar glare round the year from a userspecified observation point must be estimated. The project must demonstrate that glare will not impact airspace safety. Here the ocular hazard standard set by FAA is followed, which states that the FAA will object to any project that produces glare on the ATCT, as well as projects that produce a potential for a temporary after-image (yellow glare recorded by the model) or potential for permanent eye damage (red glare recorded by the model) on aircraft (Table 2). Solar plant configurations such as tilt, orientation, shape, etc can be modified so to mitigate glare and maximizing energy production at the same time.

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Fig. 4. Restricted surfaces for non-aeronautical use.

4. Methodology Site selection procedures for a solar PV project in the airport area is described in this section. ForgeSolar software is used for the assessment of glare impact from a selected PV site. The methodology for estimation of solar potential for each site is also decribed. 4.1. Description of the study area Senai International airport is situated in Johor state, Malaysia (22.95 km from Johor Bahru town). This airport can handle 4.5 million annual passengers per annum. The coordinates of the

Table 2 Colour code for glare occurrence.

Airport Reference Point (ARP) are 1.63oN and 103.66oE. The airport is situated at an elevation of 39m from sea level. The ICAO and IATA codes for Senai airport are WMKJ and JHB respectively. The airport spans over 1225 acres. The terminal floor area is 18,000 m2. A single runway 34-16 (Code 4E) is used for the landing and takeoff of the aircraft. This runway has length of 3800 m and width of 45 m [37,38]. For the runway having code 4E, the runway strip extends 60m from the runway threshold and 150m from the centreline of runway. The NAVAIDs of Runway-16 is Instrument Landin System approach (Category 1) and for Runway-34 is Non precision approach (VOR/DME/NDB). Data obtained from the airport’s website is used in the present study.

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4.2. Site selection procedure In general, the process of site selection considers the technoeconomic constraints of each site and the effect of these constraints on solar energy generation. Shukla et al. described that the BIPV system developers considered factors such as location, cost, aesthetics, etc before the project implementation [39]. The PV system cost decreases with the increase in installed capacity. Hence, the sites are chosen in such a way that the it can accommodate a solar system with minimum capacity of 100kWp. Apart from general sitting factors, airport-related constraints must be addressed during the site selection stage of airport based solar PV system. The prospective sites and the excluded area for the study with regard to the development of the ground-mounted solar PV system in airport is shown in Table 3. The built area, runways, vacant land, vegetation are identified using Google Earth. Google Earth framework is taken as it can provide quality resolution images, can be used easily and is freely available and easily accessible. It is highlighted that the availability of free resources helps in doing academic oriented research studies. However, the visual inspection of each selected PV site in the airport is recommended before finalising the project report. The site suitable characteristics such as solar resource, climatic condition, presence of trees and mountains (shaing aspect) were assessed for the entire airport land area. Since the selected sites fall within the airport boundary, the variation in factors such as temperature, solar irradiation, windspeed, geotechnical condition was assumed to be negligible. The sites in Malaysia are generally suitable for solar PV applications due to the availability of sunshine, varying from 800 W/m2 to 1000 W/m2 for a duration of 6 h [40]. Digital solar resource data provided by SolarGis for the region of East peninsular Malaysia is shown in Fig. 5. The slope variation in the airport region is obtained from the ESRI platform (Fig. 6). 4.2.1. Initial screening In this step, sites that are compatible with activities, regulations, future development of airport are identified. Information on existing as well as planned land uses and facilities at airport are needed for this purposed. This screening process involves gathering these information from Google maps, Airport’s Master Plan, Airport Layout Plan (depending on the data availability). solar PV sites that do not penetrate restricted airspace, consistent with airport & aviation activities and do not cause interference to CNS facilities are selected. If located close to the runways, these constraints on a solar project sitting are accounted accurately [41]. Solar panels, which are usually tilted to the south in the northern hemisphere, extending to a height of about 3-m above the ground makes the PV sitting close to runway. Still, certain areas (mostly lying near to runway) are not suitable for solar PV

installation. Object Free Area cannot accommodate nonaeronautical structures and hence is excluded from the consideration of site selection. The area outside Runway safety Area but within RPZ may accommodate infrastructure like solar facilities but would require special approval from the aviation authority such as FAA, CAA etc,. So, RPZ is not considered for the solar PV development in this study. The area between runway and taxiway/apron is not preferred during site selection due to possible glare impact and airspace penetration. 4.2.2. Filtering of feasible sites After the initial screening, the feasible sites are then reviewed for the presence of environmental resources. Those sites which need the removal of vegetation (to a great extent) are omitted. Thus the impact on natural resources can be minimized (thereby avoiding potential permitting delays). Electrical infrastructure available in the airport region was studied. Closness of the project site to electric grid eases the interconnection related issues. Fig. 7 depicts the electric transmission network in peninsular Malaysia as well as around the airport area. 4.2.3. Glare scrutiny The compatibility of selected sites with airport sensitive receptors is evaluated as per FAA interim solar policy. It is suggested to start with a large project footprint and then decrease the size (step by step) as needed. Detailed description on glare software and methodology is provided in section 4.3. Other factors discussed in Section 2 improves the suitability of PV sites. An unshaded area in the airport, particularly during the peak sun hours of (9 a.m.3 p.m), is suitable for solar PV installation. 4.3. Glare analysis A computational software called Forge Solar is used to determine the occurrence of glare from the selected PV array site. 4.3.1. Software inputs To check the potential impact on air traffic controllers, the location and height of ATC tower is given as input. The position as well as the height of air traffic control tower is in such a way that both ends of the runway are visible from it. At Senai airport, ATC is located at 1.63
and 103.67
. Its height is assumed to be 25m above ground level forge. For assessing the impact on pilots in cockpit during the final approach of aircraft, several points between the runway threshold and another point which is 2 miles or 3.22 km away from the runway threshold is considered (2 miles 3-degree glide path denoting the direction of the flight path as defined in FAA’s solar policy).

Table 3 Characteristics of different areas in the airport with respect to solar sitting. Prospective sites

Excluded sites/areas Airside

Landside

e

Area between runway & taxiway Aircraft stands and Apron Hangars & maintenance unit Meteorological station General aviation terminal

Terminal buildings Vehicle parking and access roads Commercial buildings Cargo terminala e

e

Natural and artificial grassland Barren & wasteland Land for future developmentb Area outside height restriction

Fire and rescue buildings

e

e

Helicopter standa

e

e

Fuel depot

e

a b

If present. To be unused up to 25 years.

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Fig. 5. Average value of yield of solar PV in Peninsular Malaysia.

Fig. 6. Topography of area in and around Senai airport (Source: Esri).

Here fixed-tilt solar systems are considered due to technical as well as its less possibility for glare hazard. The position of PV modules which is tilted at latitude angle and oriented true south

(180
) is taken as the optimum value at which theoretical energy generation is maximum. Hence crystalline silicon-based PV modules that are fixed at 10
and oriented true south are considered for

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Fig. 7. Electric transmission lines in the airport area [42].

the proposed solar PV system. A slightly higher tilt angle than latitude helps in the self-cleaning of PV modules during rain thereby helps in reduction of soiling loss. Nowadays, smooth glass with anti-reflective (AR) coating is present with the PV modules and hence it is chosen for the analysis. As per Federal Aviation Administration (FAA) Interim Policy 78 FR 63276, glare analysis parameters and observer eye characteristics are taken as. 1. 2. 3. 4.

Analysis time interval: 1 min Ocular transmission coefficient: 0.5 Pupil diameter: 0.002 m Sun subtended angle: 9.3 milliradians Step 1: The site is located using an interactive Google map integrated with the glare software. The user can draw an outline of the proposed solar energy system (footprint). Latitude, longitude, and elevation are automatically retrieved by the software and used for estimating the sun’s position and vector calculation. Step 2: The observer locations (ATC tower cab) and the final approach path are specified. Along with these data, orientation and tilt angle of solar PV panel are entered. For other parameters such as module reflectance and ocular factors, default values in the software are considered. Step 3: If non-compliant glare was detected for the preferred design, design parameters are varied to identify a design that would comply. The tilt angle has only a slight effect on glare results. So the changes were primarily made to the azimuth followed at times by slight adjustments to the tilt angle. In the case of excessive glare results, other material remedial options are considered.

4.4. Solar PV potential and theoretical energy generation The land footprint of a solar PV plants depends on factors such as PV technology, PV module power rating, tilt and orientation angle and distribution of PV modules within the selected site. Due

to better power output per unit area and 25 years of lifetime, monocrystalline silicon panels are mostly preferred in MW scale solar power plants. In terms of performance and efficiency, solar PV modules with a power output rating of 300 W or above (efficiency of 16.2% or more) are much better than lower power rated modules which leads to ease of installation, cost reduction and effective utilization of land area. The project area or land footprint of ground-mounted solar PV power plants equal to the cumulative PV module area and other spacing factors such as interrow spacing, accessibility [44]. As an approximate estimate, the land area required for installing 1 MWp (c-Si technology-based) solar power plant is 3.31 acres (average) in the Malaysian condition [43]. If thin-film technology is employed, 30% more area is needed for the 1 MW solar plant. This area calculation accounts for adequate spacing between solar panels, space for inverter rooms and other balance of system. This is estimation may vary to a small extent during the project implementation phase. The plant capacity/solar PV potential for each zone can be calculated based on the project area (As) using equation (1). The project area was estimated using the measuring tool provided in Google Earth.

Ps ¼

As 3:31

(1)

4.4.1. Theoretical Energy generation (ETG). The energy generation potential of the solar PV power plants can be predicted from the known CUF (Capacity Utilisation Factor) value. The average CUF value for large scale solar PV power plants in Malaysia is 16% [45,46]. The amount of energy production plays a significant role in cost-benefit analysis. The expected energy production can be estimated using equation (2).

ETG ¼ Ps 

CUF  8760 100

(2)

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The flowchart for the proposed siting of a solar PV plant and solar potential estimation is depicted in Fig. 8. 5. Results The site selection and potential assessment of solar PV plant is carried out for Senai International Airport, Malaysia. The amount of energy generation depends on the installed capacity which in turn is associated with the land area coverage. Land-based solar PV systems are cost-effective when built on a larger scale. 5.1. Solar resource and climatic conditions It was observed that the Senai airport location receives an ample amount of solar irradiation (1606 kWh/m2/year). With daily irradiation of above 4 kWh/m2, solar resource in this region is considered as suitable for solar PV energy systems. It must be remembered that the energy yield from solar PV plants increases with solar insolation present in that location. Energy output from solar PV plant is also influenced by ambient temperature, wind speed, and rain. The climatic condition in Senai airport can be termed as Hot and humid with an average temperature of 26.7
C and wind speed of 1.71 m/s (Ground-based and NASA measurements). The power conversion efficiency of solar PV modules decreases with rise in ambient temperature. The maximum and minimum temperature is observed in the month of June (27.4
C) and December (25.7
C). Since ambient temperature is below 30
C for all months, temperature losses are expected to be minimum and hence cooling strategies do not have a significant impact on energy generation. It was found that the airport location experiences low wind speed with a variation of 1.2 m/s to 2.7 m/s across the year. However, considering the wind due to aircraft movement, the mounting structure of the solar PV plants must be strong enough to overcome wind stress. As per NASA metrological data, this region received rainfall throughout the year with an average value of 208.65 mm. Maximum rainfall is obtained in the month of December (365 mm) and thus there is a need for a floodwater management system. This location lies near to the equator and thus has a tropical (hot and humid) climate. So snowfall is not observed in the Senai airport region. It was concluded that the sites do not experience extreme weather conditions. Other than these factors, air pollutants are present due to vehicular movements in airport area. This scatter sun rays and may decrease solar irradiation. Due to the presence of industries in Senai airport area, particulates such as sulfur, nitrogen and higher levels of salt content can cause corrosion of solar plant components. Fig. 9 decipts the variation of climatic parameters for the airport location. 5.2. Desing and sitting factors PV module shading: Shading from obstructions near to selected sites such as trees, buildings or overhead cables and far horizons such as mountains or buildings is observed to be negligible. The airport manager has to take care about any shading that could occur from future construction or growth of vegetation. Land use pattern: It was observed that land parcel in airport has buildings and facilities that aid aviation and passenger activities. Also, commercial activities such as shopping malls, industrial units are seen near to the entrance of the airport. The sites in Senai airport that are unused for aviation and commercial activities are selected for the proposed solar PV plant. Topography: From altitude map for Senai airport, it was found that airport is situated in a low altitude region and the height changes from 60m to 90m. So the altitude variation is small and

859

suitable for installation of solar PV module. Conversely, a steep slope terrain increases the chance for soil erosion and hence weakens the basement of PV modules. Also, it was inferred that the unevenness present in the airport areas levelised as a part of construction of the airport. The risk of seismic activity, landslip, ground subsidence, historical mining, clay heave etc, has not been reported yet. Environmental factors: It was found that certain patches of land have vegetations (trees and shrubs). Such sites are dodged to avoid depletion of ecology and potential delay in permission. The PV module soiling due to vehicular traffic, building activities and dust storms during landing and take-off may occur. It was optimistic that the soiling loss do not cause a huge loss in energy production. Proximity to electrical infrastructure: The exact data showing the on-site electrical infrastructure network in the airport was not available. From the map showing the grid system in peninsular Malaysia, it was found that 275 kV overhead transmission line from the northern part reaches tills Johor Bahru crossing Senai airport. All the selected sites lie at almost equal distance from the transmission line. A supplementary study is needed to learn the effect of penetration levels of power generation from PV on grid stability. It is suggested to interconnect the PV system installed at different sites with the existing electrical infrastructure network/switchyard of the airport. The summary of the general siting factors for site selection of solar PV plants in Senai airport is given in Table 4. Airport specific factors: Apart from general sitting constraints, airport-based solar PV systems make sure that the solar project will not cause a negative effect on exist airport and aviation activities.  Airspace penetration: All unused or vacant land cannot be sited for the installation of solar PV modules. Here FAR part 77 surfaces which restrict the installation of solar PV modules in airport premises is considered. PV modules must be located in such a way that it does not penetrates into the airspace surfaces. Solar PV installation near the runway must be done with extra caution. It was observed that the selected sites (site 1 to site 11) do not fall in under object free area or runway strip or the Runway protection zone. None of the site lies in the area between runway and taxiway/apron is not chosen during site selection.  Interference to the operation of NAVAIDS: It was realised that the identification of correct location and the radial distance from radar and communication systems is difficult. Usually radars and navigational facilities are located along the sides of the runway. Site selected in this study are situated away from the runway.  Consistency with airport activities: The selected sites lies on airport property such as areas isolated or away from existing aviation facilities and airport infrastructure. Hence these sites are consistent with the existing airport layout plan. It was studied that the future development plans of the airport include an extension of taxiways on both sides of the runway. Eleven (11) potential sites were identified for the proposed solar PV system in Senai airport based on the presented methodology. The sites are named as Site 1, Site 2, Site 3 etc as shown in Fig. 10. The boundary of the airport is shown in red color. The exact location and approximate area of each site is provided in Table 5. Subsequently, these sites were evaluated for its adherence to Federal Aviation Administration Interim Policy (78 FR 63276) on glare occurrence.

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Fig. 8. Flowchart for site selection and solar potential assessment in airport.

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861

Fig. 9. Monthly variation of Irradiation, Temperature, Wind speed and Rainfall.

Table 4 Summary of general siting constraints for solar PV plant. Name of the Constraint

Information

Value

Remarks

Solar resource Climatic Condition

4.40 kWh/m2/day hot and humid with medium temperature and low wind speed

Typical solar irradiation level for Malaysia Normal power conversion loss is expected

PV module shading Land use pattern

Low or no shading Aviation related infrastructure and commercial buildings present Airport is situated in low altitude (60me90m) flat region Presence of trees and shrubs Stable land area and suitable for solar PV installation Dust and particulates due to flight and vehicular movements Presence of switchyard in airport premise

4.5 26.7
C, 1.71 m/ s, 208.65 mm 3% (assumed) No settlements

Topography Vegetation Geotechnical conditions PV array soiling Proximity to electrical infrastructure

60e90 m Little Safe 2% (assumed)

Shading loss is negligible Selection of unused and low revenue sites is important Suitable for construction of solar PV plant Must be taken care off during site selection Assumption Low level soiling losses expected

4 km (assumed) Energy generated is fed to nearby grid

Fig. 10. Sites selection for solar PV plant installation in Senai airport.

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Table 5 Details of various sites selected in airport premises. PV site

Location

Area (acres)

Area (m2)

Remarks

Site Site Site Site Site Site Site Site Site Site Site

Right side of entry to airport Near to passenger terminal Near to passenger terminal Near to passenger terminal Adjacent to airport cargo warehouse Near to cargo buildings Near to aircraft parking zone Close to Elite flying club Near to cargo buildings Near to Dept. of Civil Aviation Adjacent to Jalan Jumbo

8.036 0.459 0.447 0.641 3.249 7.449 1.836 4.669 9.840 2.794 4.035

32,520.57 1857.50 1856.47 2594.035 13148.24 30145.03 7430.03 18894.77 39821.07 11306.92 16329.07

Presence of vehicles Presence of passenergs and vehicles Presence of passenergs and vehicles Nil Plants and shrubs are present Nil Little vegetation is present Little vegetation is present Nil Nil Little vegetation is present

1 2 3 4 7 11 9 8 10 5 6

5.3. Glare assessment Out of the eleven selected sites, glare occurrence was predicted from six sites. For Site 7 (1224 min) and Site 9 (200 min), the green glare on flight path was expected which adheres to FAA’s interim solar policy. But the glare impact on sites 2, 3, 4 and 6 is in such a manner that it will affect the flight movement because of the occurrence of yellow glare on ATC. Sites 2 (1125 min), 3 (4724 min), 4 (3805 min), 6 (1125 min) do not adhere to FAA’s interim solar policy. As seen in Table 6, the tilt angle and orientation of PV array for these sites (2, 3, 4,6) is changed. At tilt angle of 15
and orientation angle of 200
, the site 2 became compactible as per glare policy with 97.4% theoretical energy generation. Similarly, the system design which complys the glare policy and has maximum relative energy production is marked in blue colour. Glare occurrence final status of selected sites is shown in Table 6. The total peak solar power from all the selected sites equal to 12.50 MW. At 16% CUF, the cumulative energy production is 16,745 MWh. Sites 10, 11 and 1 has the highest energy generation which can be attributed to its installed capacity. Since the installation area of site 2 and 3 is low, the PV potential as well as the energy production is less from these sites. The solar PV potential and expected energy generation from selected sites are shown in Fig. 11. 6. Discussions The present study scrutinizes the land area in Senai airport for the siting of the solar PV system. Various constraints including airport-specific factors were considered in this assessment. Based on these factors, elevan sites were chosen. The influence of selection criteria in energy yield and the relevance of these criterion over the other is discussed in this section. 6.1. Impact on energy generation In a few cases, the design of the solar plant is altered to accommodate the issues of visibility impairment from glare. The tilt angle of solar PV modules is changed from the default value (latitude) to alleviate glare hazards from a certain solar installation at the airport. These changes affect the energy generation from the solar system. Similarly, the PV modules positioned at default orientation angle of 180
may cause the glare. Special manufactured PV modules with the least surface reflectivity can reduce the possibility of glare occurrence. These changes deviate from the usual design procedures followed for land-based system and hence affect the performance of system. The tilt angle is chosen as 0
if the solar PV modules are to be fixed close to the boundary of restricted airspaces. Hence the adjustments in system design to accommodate airport related sitting constraints can affect the energy yield

significantly. The location of the electricity grid and the presence of trees may cause energy loss from solar plant. Sites that lie close to electrical infrastructure is preferred. The reduction in length of cable decreases AC cabling loss and the cost of cabling. In case, a chosen site is far from an electricity fed point, the AC cables with high cross section and low resistivity are chosen. The presence of trees, bushes (and buildings) cause the shadow on PV modules. Therefore, sites are selected in such a way that the shadow falling on that area is nil or negligibly small. Other sites are avoided as the plant output reduces to a big extent even with less amount of shadow. By taking some mitigation measures, the reduction in energy generation can be reduced to a great extent. Since the chosen sites lie within the airport location. the variation in solar resource availability, climatic conditions, geotechnical conditions among the sites were negligibly small. Hence these factors of site selection do not affect the solar energy output to great extent. Apart from that, the airport region experiences different weather due to pollutants, aircraft emissions, heat island effect. etc. In the airport, vast areas of land cover are concrete and asphalted surface which in turn lead to urban heat effect, thereby increasing the temperature [47]. The atmosphere temperature in the areas in and around Mumbai Airport raised by 12% from April 1999 to 2013 [48]. Hence the influence of this micro weather condition in solar energy output can be studied. 6.2. Priority of selections constraints Among these constraints, glare hazard is perceived as the most significant one from past experiences as well as works of literature. Glare affects the visibility of pilots as well as staff in the air traffic controller. Any wrong decision from these professionals may lead to causalities, economic loss even death. In this regard, aviation authorities such as the FAA, CAA instructed the solar project developer has to obtain no hazard approval from them. The interference to the operation of CNS facilities in the airport by the PV modules disturbance is expected to be low and is not considered seriously by the airport authorities. However, as a word of caution, a setback of 250e500 feet from the radar system is followed in solar installations. Also, it is suggested to avoid sitting of solar PV in the areas around the runway where the CNS facilities are installed. Since the restricted imaginary airspace is well quantified, the selection of sites without intrusion into the imaginary airspace can be done accurately. General siting suitability factors such as good solar resource, favourable climate, slope, topography influences the energy yield from solar PV plant. Wang et al. selected potential sites in QinghaiTibet Plateau, Tibet based on the abundance of solar energy, land

S. Sreenath et al. / Renewable Energy 152 (2020) 849e866 Table 6 Glare occurrence status of selected sites in Senai airport.

Selected

Solar

sites

poten angle

Tilt

Orient- Glare

System

Energy

Adherence to

ation

output

generation

FAA policy

Status

tial

( relative (MWh)

(kW

to

dc)

theoretic al max.)

Site 1

2500

10o

180o

No

100%

Site 2

140

10o

180o

Yellow

Yes 3504

glare 100%

No

glare of 1125

196.224

mins on ATC 15o

200o

No

97.4%

glare 30o

200o

No

88.7%

glare 45o

140o

No

77.4%

glare Site 3

140

10o

180o

4724

191.122 169.52 151.88

100%

Yes. Yes Yes No

mins of yellow

196.224

glare on ATC 45o

140o

No

77.40%

45o

50o

No

76.7%

200o

No glare

Yes 150.50

glare 45o

Yes 151.88

glare

74.70%

Yes 146.58

863

864

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use pattern and topography, followed by other factors such as distance to the nearest substation [49]. The effect of these constraints in energy generation is expected to be the same for all the chosen sites within airport. Hence it is not given high priority in the present airport scenario. In a few cases, it was observed that sites are unsuitable due to shading on PV modules, longer distance to the electricity grid, loss of vegetation. Also, presence of trees, shrubs or buildings causes a shadow in the chosen site. In most of the cases, the effect of shading cannot be mitigated. The removal of green cover for the solar plant requires approval from multifaced authorities and it sets a wrong example. The cabling loss increases with the farness between site and electrical infrastructure. These factors are given medium

priority during site selection. The airport-specific constraints vary significantly with the location of the site. The suitability of the site in the airport environment is mainly determined by factors such as glare occurrence, interference to communication systems, airspace penetration. The airport-related constraints are the significant ones as many sites were identified with southerly exposure to sunlight. Among them, glare impact study has a significant role in selection criteria. 6.3. Limitations and scope of the future work The boundary of the airport was identified and chosen sites lie within it. The selection criteria were based on 6 general siting

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865

Fig. 11. Solar PV potential and expected energy generation from selected PV sites.

aspects and 4 airport-specific constraints. If proper data is not available, relevant assumptions are made. Fixed tilt solar PV systems with an installed capacity of more than 100kWp is considered for each site. Mapping tools were used to analyze the topography and green cover of the selected airport sites. The penetration of the site into imaginary airspace was decided based as per FAR part 77. Also, sites around the runways are avoided in the wake of possible exostance of CNS facilities. The future development plan is studied using ALP, airport website, documents etc. The compatibility of the site to glare is assessed based on FAA interim solar policy which states that any glare impact on air traffic controller and potential for after image on flight path must not occur. This study lacks in taking expert opinions from airport staff, pilots and consultants in addition to information gathered from previous pieces of literature and airport data. Air safety is of paramount importance. A site visit to airport can give more insights and conclusions. The effect of PV systems on the interference to CNS facilities has not studied in detail. The possibility of siting solar PV between the runway and taxiway area is not explored.

7. Conclusions Since the airport spans over several acres of land, many potential sites can be located for the development of solar PV system within the boundary of airport area. In this research work, the main directives of the work include identification of potential sites for solar PV system complying aviation regulations, followed by the estimation of solar PV potential in airport.  Out of the solar PV siting constraints, the significant ones are the possible glare occurrence, penetration into restricted airspace and interference to CNS facilities, loss of vegetation and access to electrical network. These factors have the potential to cause threat to safe air navigation and to affect energy generation.  Due to the absence of regional guidance on evaluating the potential impacts of solar PV system, this general sitting procedure for airport-based solar PV system is prepared on the lines of rules, policy and regulation by FAA such as FAR part 77, Advisory Circular (AC) 1500-13 and Airport Planning Manual.  Out of eleven selected sites, glare occurrence was predicted from six sites. For Site 7 (1224 min) and Site 9 (200 min), the green









glare on flight path was projected which adheres to FAA’s interim solar policy. Yellow glare on ATC is a matter of concern. Since sites 2 (1125 min), 3 (4724 min), 4 (3805 min), 6 (1125 min) do not adhere to FAA’s interim solar policy, design parameters are modified. Though these sites became suitable for the installation of solar PV plant, the variation in tilt and orientation angle resulted in the reduction in the energy generation. The cumulative solar potential from these sites equals to 12.50 MW with an annual energy yield of 30941.20 MWh. Among the selected sites, the top solar potential sites are Site 10 (3 MW), Site 1 (2.5 MW), and Site 11 (2.2 MW). Airport solar projects are expected to be executed in many airports in the wake of climate change and cost factors. Furthermore, developments of new knowledge and tools are needed for quantifying and mitigating the impacts of solar energy technologies in an airport. To sum up, a special case of site selection is presented where airport-related constraints are accounted for. The success of the solar PV project depends on close coordination between airport administrators, financial managers, local aviation regulators, construction engineering companies, planners.

Declaration of competing interest Authors hereby declare that there is no conflict of interest for the research work reported in this manuscript. CRediT authorship contribution statement S. Sreenath: Writing - original draft, Software, Investigation, Data curation. K. Sudhakar: Conceptualization, Supervision, Writing - review & editing, Methodology. A.F. Yusop: Supervision. Acknowledgment The authors are grateful to the Universiti of Malaysia Pahang (UMP) for financial support through the Doctoral Research Scheme (DRS), RDU1803100 and PGRS1903172. Also, the authors are grateful to ForgeSolar software for providing educational access.

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References [1] A.K. Shukla, K. Sudhakar, P. Baredar, Renewable energy resources in South Asian countries: challenges, policy and recommendations, Resour. Effic. Technol. (2017). [2] A.K. Shukla, K. Sudhakar, P. Baredar, R. Mamat, BIPV based sustainable building in South Asian countries, Sol. Energy 170 (2018) 1162e1170. January 2017. [3] P. Ruther, Ricardo Braun, “Solar Airports,”, Refocus, August, 2005, pp. 30e34. [4] Y.D. Jun-ku Xu1, J. Xu, Y. Deng, Research on application of renewable and clean energy in Beijing new airport, in: International Conference on Power, Energy and Environmental Engineering (ICPEEE 2018), Icpeee 2018, 2018, pp. 22e25. [5] C. Rüther, R. Braun, P. Zomer, The potential of photovoltaics on airports, in: 21st European Photovoltaic Solar Energy Conference, 2006, pp. 4e7. September. [6] S.O. Alba, M. Manana, Energy Research in Airports : A Review, 2016, pp. 1e19. [7] M. Costantinou, Glaring Danger-Bright Sun, Deadly Collisions, 1998. San Francisco Examiner. [8] R. D. Ho, C., C. Ghanbari, “Hazard analysis of glint and glare from concentrating solar power plants,” in SolarPACES 2009, Berlin, Germany, Sandia National Laboratories,. [9] J. Gotcher, Airport Manager, Meadows Field, 2010. [10] Barnstable municipal airport [Online]. Available, www.town.barnstable.ma.us. Accessed: 13-Sep-2018. [11] Indianapolis Airport [Online]. Available, http://www.cleanenergyauthority. com/solar-energy-news/indianapolis-airport-solarfarm- proposed-092211/. Accessed: 08-Sep-2018. [12] J. Decastro, FAA Western-Pacific Region, 2010. [13] A. Kekakeuwela, Oakland Port Authority, 2010 personal communication. [14] K. Hermawan, Design analysis of photovoltaic systems as renewable energy resource in airport, in: 4th Int. Conf. On Information Tech., Computer, and Electrical Engineering, ICITACEE), 2017, pp. 113e116. [15] I. C, Troy V. Nguyen, Aldo Fabregas Ariza, Nicholas W. Miller, A framework for the development of technical requirement for renewable energy systems at a small scale Airport facility, in: Proceedings of the ASME 2015 9th International Conference on Energy Sustainability, California, San Diego, 2015, pp. 1e8. [16] A. Anurag, J. Zhang, J. Gwamuri, General Design Procedures for Airport-Based Solar Photovoltaic Systems, 2017, pp. 1e19. [17] C.D. Zomer, M.R. Costa, A. Nobre, R. Rüther, Performance compromises of building-integrated and building-applied photovoltaics (BIPV and BAPV) in Brazilian airports, Energy Build. 66 (2013) 607e615. [18] Tucson airport [Online]. Available, https://tucson.com/business/tucsonairport-marks-completion-of-iconic-solar-array/article_65e6659d-84555100-8b1e-f2c5a6c84280.html. Accessed: 10-Nov-2018. [19] San Diego county regional airport authority [Online]. Available, www.san.org, 2019. Accessed: 20-Jan-2019. [20] A.K. Shukla, K. Sudhakar, P. Baredar, Design , simulation and economic analysis of standalone roof top solar PV system in India, Sol. Energy 136 (2016) 437e449. July. [21] B.S. Kumar, K. Sudhakar, Performance evaluation of 10 MW grid connected solar photovoltaic power plant in India, Energy Rep. 1 (2015) 184e192. [22] A. Alami Merrouni, F. Elwali Elalaoui, A. Mezrhab, A. Mezrhab, A. Ghennioui, Large scale PV sites selection by combining GIS and Analytical Hierarchy Process. Case study: eastern Morocco, Renew. Energy 119 (2018) 863e873. [23] S. Wittkopf, S. Valliappan, L. Liu, K. Seng, S. Chye, J. Cheng, Analytical performance monitoring of a 142 . 5 kW p grid-connected rooftop BIPV system in Singapore, Renew. Energy 47 (2012) 9e20. October 2009. [24] K. Rajput, Dayal Sudhkar, Effect of Dust on the Performance of Solar PV Panel,

2014. May. [25] N. Manoj, K. Sudhakar, M. Samykano, S. Sukumaran, Dust cleaning robots (DCR) for BIPV and BAPV solar power plants-A conceptual framework and research challenges, Procedia Comput. Sci. 133 (2018) 746e754. [26] K.A. Kumar, K. Sundareswaran, P.R. Venkateswaran, Performance study on a grid connected 20 kWp solar photovoltaic installation in an industry in Tiruchirappalli (India), Energy Sustain. Dev. 23 (2014) 294e304. [27] M. Mpholo, T. Nchaba, M. Monese, Yield and performance analysis of the fi rst grid-connected solar farm at Moshoeshoe I International Airport , Lesotho,, Renew. Energy 81 (2015) 845e852, 2014. [28] M. Giamalaki, T. Tsoutsos, Sustainable siting of solar power installations in Mediterranean using a GIS/AHP approach, Renew. Energy 141 (2019) 64e75. € rtberg, D. Mentis, M. Welsch, I. Babelon, M. Howells, Wind [29] S.H. Siyal, U. Mo energy assessment considering geographic and environmental restrictions in Sweden: a GIS-based approach, Energy 83 (2015) 447e461, 2015. [30] G. Baxter, G. Wild, R. Sabatini, G, S. Baxter, G. Wild, A sustainable approach to airport design and operations: case study of Munich airport’, in: Proceedings of Practical Responses to Climate Change, Engineers Australia Convention, 2014, pp. 227e237. [31] L. Cuadra, E. Alexandre, in: A Study on the Impact of Easements in the Deployment of Wind Farms Near Airport Facilities vol. 135, 2019, pp. 566e588. [32] S. Sukumaran, K. Sudhakar, Fully solar powered airport: a case study of Cochin International airport, J. Air Transport. Manag. 62 (2017) 176e188. [33] ACRP, “Understanding Airspace, Objects and its Effect on Airports.” [34] R. Thompson, I. Ave, D. Anne, M. Jan, S. David, C. Robert, Interim Policy, FAA Review of Solar Energy System Projects on Federally Obligated Airports, 2013. [35] FAA, Technical Guidance for Evaluating Selected Solar Technologies at Airports, 2018. [36] C. Ho, C. Sims, Solar Glare Hazard Analysis Tool (SGHAT) User’s Manual V. 1.0, Sandia National Laboratories, 2012. [37] Senai airport. [Online]. Available, www.senaiairport.com. Accessed: 12-Oct2019. [38] A.M. Bagher, M. Mahmoud, A. Vahid, M. Mohsen, Types of Solar Cells and Application, vol. 3, 2015, pp. 94e113, 5. [39] A. Kumar, K. Sudhakar, P. Baredar, R. Mamat, “Solar PV and BIPV system : barrier , challenges and policy recommendation in India, Renew. Sustain. Energy Rev. 82 (August 2017) 3314e3322, 2017. [40] M.E. Ya, H. Hizam, T. Khatib, M.A.M. Radzi, A Comparative Study of Three Types of Grid Connected Photovoltaic Systems Based on Actual Performance, vol. 78, 2014, pp. 8e13. [41] FAA, “Part 77 Objections Affecting Navigable Airspace.” [42] GENI, “Grid System in Peninsular Malaysia.” . [43] Solar power plant installations in Malaysia [Online]. Available, http://aer. global/topic-13-solar-power-plant-installations-in-malaysia/. Accessed: 16Dec-2018. €berlin, Photovoltaics System Design and Practice, John Wiley & Sons., [44] H. Ha 2012. [45] K. Moorthy, Talking Malaysia Renewable Energy, Khor-Reports, 2019. [46] N.M. Kumar, K. Sudhakar, M. Samykano, Techno-economic Analysis of 1 MWp Grid Connected Solar PV Plant in Malaysia, vol. 750, 2017. December. [47] P.T. Akbari, Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas, Sol. Energy 70 (3) (2001) 295e310. [48] A. Dwivedi, Macro- and micro-level studies using Urban Heat Islands to simulate effects of greening, building materials and other mitigating factors in Mumbai city, Architect. Sci. Rev. 62 (2) (2019) 126e144. [49] S. Wang, L. Zhang, D. Fu, X. Lu, T. Wu, Q. Tong, Selecting photovoltaic generation sites in Tibet using remote sensing and geographic analysis, Sol. Energy 133 (2016) 85e93.