Application of PV on Commercial Building Facades: An Investigation into the Impact of Architectural and Structural Features

Abstract

The rapid global transition toward renewable energy necessitates innovative solar PV deployment strategies beyond conventional roof installations. In this context, commercial building facades represent an expansive yet underutilized resource for solar energy harvesting in urban areas. However, existing studies on commercial rooftop solar PV predominantly focus on European contexts, neglecting the unique design constraints and performance trade-offs present in regions such as the Middle East. This study addresses this gap by specifically investigating the impact of architectural and structural features on the utilizable facade area for PV deployment in commercial buildings within the hot desert climate of Saudi Arabia. Detailed case studies of twelve representative buildings are conducted, combining architectural drawing analysis, on-site measurements, and stakeholder surveys. The methodology identified sixteen parameters across three categories—facade functionality, orientation suitability, and surrounding obstructions—that impose technical and non-technical restrictions on photovoltaic integration 3D modeling, and irradiance simulations revealed that, on average, just 31% of the total vertical facade area remained suitable for PV systems after accounting for the diverse architectural and contextual limitations. The study considered 698 kWh/m² of solar irradiance as the minimum threshold for PV integration. Shopping malls displayed the lowest utilizability, with near-zero potential, as extensive opaque construction, brand signage, and shading diminish viability. Offices exhibited the highest utilizability of 36%, owing to glazed facades and unobstructed surroundings. Hotels and hospitals presented intermediate potential. Overall, the average facade utilizability factor across buildings was a mere 16%, highlighting the significant hurdles imposed by contemporary envelope configurations. Orientation unsuitability further eliminated 12% of the initially viable area. Surrounding shading contributed an additional 0.92% loss. The results quantify the sensitivity of facades to aspects such as material choices, geometric complexity, building form, and urban context. While posing challenges, the building facade resource holds immense untapped potential for solar-based urban renewal. The study highlights the need for early architectural integration, facade-specific PV product development, and urban planning interventions to maximize the renewable energy potential of commercial facades as our cities rapidly evolve into smart solar energy landscapes.

1. Introduction

The global energy system stands at a pivotal crossroads, confronted by an array of multifaceted challenges that threaten the sustainability and security of our energy systems. The world today is heavily dependent on fossil fuels, which meet around four-fifths of the global energy needs and are responsible for a majority of global greenhouse gas (GHG) emissions [1,2]. This high reliance on finite fossil fuels has led to several interconnected predicaments, such as resource depletion, price volatility, geopolitical tensions, and alarming environmental consequences [3,4]. This precarious dependence on fossil fuels is further exacerbated by rapid urbanization, population growth, and economic development, particularly in emerging economies. To avert catastrophic climate change and achieve sustainable development, there is an urgent imperative to decarbonize the global energy system by transitioning to renewable and low-carbon sources. Within this transformative endeavor, the building sector occupies a central role, standing as a vital nexus of energy consumption and environmental impact. Buildings account for 30–40% of total global final energy use and around 27–30% of greenhouse gas emissions, cementing their status as one of the single largest contributors to the world’s energy and environmental footprints [5,6,7,8]. Space heating and cooling, in particular, constitute a major share of building energy use, driven by population growth, rapid urbanization, rising income levels, and living standards. Consequently, the building sector offers immense potential for energy savings and emission reductions through sustainable design strategies, energy efficiency measures, and integration of renewable energy technologies.

Among renewable options, solar photovoltaic (PV) has witnessed unprecedented growth in recent years owing to plummeting costs, policy support, and technological maturation. Buildings present an especially attractive application for solar PV, as they offer an abundant surface area for deployment while allowing direct use of the generated electricity, thereby minimizing transmission and distribution losses. However, the application of PV systems in the building sector is not without its challenges. The inherent characteristics of solar PV, such as low power density and the need for unobstructed access to solar radiation, render it highly sensitive to the architectural and structural features of buildings. These features, which encompass aspects such as facade design, orientation, shading, and surrounding obstacles, can significantly impact the performance and viability of PV systems. Facade designs and geometries vary widely, from fully glazed curtain walls to opaque rain-screen systems, with each typology presenting unique opportunities and barriers for PV integration. For instance, high window-to-wall ratios limit the available surface area for PV, while irregular facade articulation and external obstructions can cause significant self-shading losses [9,10]. The diversity of contemporary architectural styles and the prevalence of curved, twisted, and free-form facade geometries further compound the complexity [11,12]. Therefore, a comprehensive understanding of the interplay between building design and PV integration is crucial for optimizing the deployment of this technology in the built environment. Commercial buildings (e.g., offices, hotels, hospitals, shopping malls, etc.), in particular, present a complex and diverse landscape for PV integration [13]. Design and architectural features of buildings may vary from place to place depending on a number of factors, including climate conditions, availability of materials, and socioeconomics. Typically, in any society, commercial buildings exhibit a wide range of architectural styles, facade materials, and functional requirements, which can pose unique challenges and opportunities for PV application [14]. The facades of commercial buildings, with their expansive surface areas and exposure to solar radiation, represent a largely untapped resource for PV integration [15]. However, the utilization of these facades for PV is influenced by a myriad of factors, including facade functionality, building orientation, and surrounding obstacles.

While rooftops have been widely studied for solar PV potential [16,17,18,19,20,21,22], facade integration remains relatively less explored, especially for commercial buildings. Despite the growing body of research on building-integrated photovoltaics (BIPV), there remains a paucity of studies specifically focusing on the application of PV on commercial building facades in the context of architectural and structural features. Moreover, existing literature on building-integrated photovoltaics (BIPV) has focused more on the construction in a European context. There is a lack of scientific literature examining the facade integration potential of PV in other commercial building typologies and climatic contexts, particularly in the Middle East. Distinctive architectural styles, construction practices, urban forms, and sociocultural norms engender unique design constraints and performance trade-offs that warrant deeper investigation.

This study aims to address this critical research gap by investigating the application of PV on the facades of four archetypal commercial buildings—hotels, offices, shopping malls, and hospitals—in the hot desert climate of Saudi Arabia. The overall aim is to assess the impact of architectural and structural features on the utilizable facade area for PV deployment. Detailed case studies of 12 representative buildings, 3 from each typology, are conducted to identify and categorize the range of design obstacles and constraints. Key parameters analyzed include facade materials and construction details, geometric complexity, orientation, window-to-wall ratio, external obstructions, self-shading, and technical performance.

While this study focuses on the specific context of Saudi Arabia, the methodology and insights are broadly applicable to other urban areas in hot, sunny climates. The approach developed here can be adapted to different geographies and building typologies, providing a valuable tool for researchers and practitioners seeking to unlock the untapped potential of building facades for renewable energy production.

2. Methodology

This study investigated the potential for solar PV application on the facades of commercial buildings in the Eastern Province of Saudi Arabia. The study employed a mixed-methods approach, combining quantitative and qualitative techniques to assess the utilizability of commercial building facades for solar PV application. A systematic methodology (Figure 1) was adopted.

2.1. Selection of Case Study Buildings

Four major categories of commercial buildings were investigated in this study—office buildings, hotels, hospitals, and shopping malls. A total of 12 representative buildings, 3 of each building type, were selected for detailed analysis. The selected buildings are all located in the city of Khobar (26.2833° N, 50.2000° E), Saudi Arabia, which has a hot desert climate characterized by high solar irradiation (annual direct normal irradiation of 2000 kWh/m²), clear skies, and low precipitation [20]. Buildings were selected to provide a representative cross-section of the existing building stock in terms of architectural design, facade materials, size, height, orientation, and surroundings. Google Maps and satellite imagery were used for the initial identification of suitable buildings meeting the criteria.

2.2. Data Collection

The data collection comprised three components:

• Analysis of architectural drawings. As-built architectural drawings of the selected buildings were obtained and studied to gather details on facade dimensions, materials, openings, architectural features, and surrounding structures. This provided the base data for calculating the total facade area and solar potential.
• On-site surveys. On-site surveys of the buildings were conducted to validate and complement the drawing details. The surveys examined the current facade conditions and identified permanent hurdles or restrictions for solar PV applications. Photographic documentation was performed to record the facade features. Surveys also measured shading angles and distances to adjacent structures.
• Stakeholder surveys. Questionnaire surveys were conducted with building industry stakeholders to understand their perspectives on PV payback expectations. This provided data to determine the minimum acceptable solar irradiation level for facade PV applications.

2.3. Facade Assessment

Building facades were systematically evaluated to identify and quantify factors that constrain the utilization of the facade area for PV deployment. Sixteen restricting factors were identified and classified into three main categories:

• Facade functionality and design: material, color, signage, projections, recesses, brand identity elements, and building services (e.g., HVAC and piping).
• Building orientation: facade azimuth relative to solar path.
• Surrounding structures: shading and irradiance reduction caused by adjacent buildings and infrastructure.

The presence or absence of each restriction on the building facades was marked. These qualitative data formed the basis for quantifying the PV utilizable facade area. The total and restriction-free facade areas for the buildings were determined from the architectural drawings. Next, the acceptable minimum solar irradiation level for facade PV application was calculated based on a payback period survey. Areas not meeting this insolation threshold based on orientation were excluded. The net impact of restricting factors was quantified by calculating the facade utilizability factor (UF), defined as the fraction of the total facade area that was suitable for PV deployment after accounting for all constraints. The facade utilizability factor (UF) was calculated as:

UF = (total facade area − restricted area from functionality − area not meeting solar threshold − shaded area)/total facade area

This yielded the proportion of the total facade area that was available for solar PV application after considering all restrictions.

2.4. Solar Modeling

Detailed 3D models of each building and its surroundings were constructed using satellite imagery, architectural drawings, and on-site measurements as input data. These 3D models were then used to run shading and irradiance simulations in the BIMsolar software package (Version 4.0). Typical meteorological year (TMY) weather data for Khobar were used to evaluate the impact of building orientation and shading on annual irradiance received across each facade. The quantified solar potential results of the case studies were compiled and analyzed across the four commercial building categories. Average values were determined for the initial restriction-free area, final usable area, and UF by building type. Variations in restriction patterns and solar potential were examined across the cases. Key insights were derived on facade solar accessibility for different commercial typologies located in hot, sunny climates.

2.5. PV Performance and Payback Analysis

PV performance simulations were conducted using the modeled irradiance data to estimate annual energy generation for facade-mounted PV systems. The economic payback period was evaluated as the key metric for assessing PV system viability. A maximum 8-year payback period was used as the cut-off criteria based on the findings of a survey of 50 local building industry professionals and owners. Monocrystalline silicon PV modules with 8% efficiency and a 0.81 performance ratio were assumed. Payback analysis used an electricity price of USD 0.08/kWh and a total installed PV system cost of USD 0.75/W.

3. Analysis

3.1. Building Audits

Comprehensive building audits were conducted to collect detailed data on the architectural and structural features of the selected commercial building facades. The audits involved two key components—analysis of architectural drawings and on-site surveys. Before the on-site audits, as-built CAD drawings of each building were carefully studied. The drawings contained detailed plans, sections, and elevations, providing insights into the facade dimensions, materials, fenestration, architectural elements, and surrounding context. The unobstructed facade zones available for PV application were delineated. The architectural drawings provided baseline data for each building, such as total facade area, window-to-wall ratios on different orientations, areas covered by shading elements, such as overhangs and fins, locations of building services’ fixtures on facades, and details on facade materials and construction systems. This quantitative and spatial information formed the starting point for assessing the PV feasibility of the commercial building envelopes. The on-site audits consisted of thorough visual inspections and measurements of each building’s facades. The total facade area was validated, and the prevalence of different facade materials (e.g., glazing, concrete, stone cladding, and metal panels) was quantified. Architectural features and geometric complexities that could impact PV system design and performance were identified and documented, including projections, recesses, overhangs, and non-planar surfaces.

A range of potential obstructions and design constraints for facade-mounted PV were assessed, including:

• Mechanical, electrical, and plumbing services (e.g., HVAC equipment, conduits, and piping).
• Facade access and maintenance equipment (e.g., window-washing systems and swing stages).
• Signage, logos, and other brand identity elements.
• Aesthetic and design features intended to create visual interest or align with corporate identity.

Obstruction elements were classified according to their permanence (fixed vs. movable), size, and position on the facade. The prevalence and arrangement of obstruction elements were mapped using a combination of field measurements, photographs, and CAD drawings. Figure 2 provides representative examples of commercial building facades in Khobar, illustrating the range of obstruction elements and design constraints commonly encountered.

The impacts of obstructions and design constraints were analyzed in terms of the two key factors affecting PV system performance and feasibility:

• Space utilization: The physical area occupied by obstruction elements was quantified and subtracted from the total facade area to determine the net usable area for PV deployment.
• Shading: Obstructions that protrude from the facade plane can cast shadows on adjacent facade areas, reducing the incident solar irradiance available for PV conversion. The size, shape, and position of shading elements were analyzed to model their shading impacts.

In addition to the features of the buildings themselves, the surrounding built environment was carefully assessed. Adjacent buildings and infrastructure were cataloged, and their heights, setbacks, and orientations relative to the audited buildings were measured. These data enabled the modeling of shading and irradiance losses caused by the urban context.

The building audit sample was carefully selected to capture the diversity of commercial building designs in Khobar. A set of key architectural parameters was defined to characterize this diversity, including building form, height, facade type, primary facade materials, and orientation. The audit sample was structured to span a representative range of each parameter, ensuring that the results reflected the breadth of the existing building stock.

The analysis of individual building characteristics revealed clear patterns correlated with building use type. Shopping malls tended to be large low-rise structures with flat, opaque facades comprised of precast concrete or CMU walls. Hotels and office buildings were more likely to be high-rise structures featuring extensive glazed curtain wall facades, sometimes accentuated with aluminum or stone cladding. Hospitals often presented a hybrid condition, with facade designs that incorporated elements common to both the low-rise and high-rise typologies.

3.2. Facade Restrictions Impacting PV Utilizability

The application of solar PV on building facades poses unique challenges compared to conventional rooftop installations. Architectural requirements related to aesthetics, visibility, and functionality impose multiple restrictions that limit the utilizable area on facades. The architectural characteristics and features of commercial building facades exhibit significant diversity, ranging from minimalistic plain surfaces devoid of ornamentation to intricate designs and extensively glazed envelopes, with various intermediate configurations [23,24]. These disparate attributes play a decisive role in determining the extent to which building facades can be effectively utilized for the application of solar PV systems. The concept of the facade utilizability factor (UF) denotes the proportion of total facade area that is available for integrating solar PV panels after excluding restricted zones. The restricted area comprises all parts of the facade affected by functional, orientation, or surroundings-related limitations, as discussed below. Accurately delineating the usable and restricted areas through rigorous audits is crucial for reliable UF estimation. The UF provides a realistic measure of the facade’s solar potential and guides PV system design and sizing.

In addition to the inherent features of the facade itself, the surrounding built environment also exerts a critical influence on the PV utilizability of a building’s exterior surfaces. Structures in close proximity, especially those of greater height positioned along the sun’s path, can cast shadows on the facade, thereby significantly diminishing its UF [25]. This shading effect is particularly pronounced in dense urban settings characterized by limited spacing between buildings and the prevalence of high-rise constructions [26].

Based on a detailed review of the literature and initial facade surveys, this study defined 16 parameters covering the major restriction types that were systematically evaluated for the case study buildings. These parameters were categorized under three overarching groups, as shown in

Table 1. Identified facade hurdles.

Classification	Description	Serial	Details
Facade functionality	Facade material	H1	Clear glass
		H2	Stone cladding
		H3	CMU
		H4	Precast panel
		H5	Aluminum cladding
	Facade typology	H6	Irregular facade design
		H7	Presence of projections
		H8	Presence of architectural feature
		H9	Facade design brand feature
		H10	Sign board and ads feature
	Presence of services, such as HVAC and piping	H11	HVAC duct
		H12	Piping
		H13	Chimneys
Building orientation	North orientation	H14
Building surrounding	Adjacent building heights	H15	Lower than the case building
			Same height as the case building
			Higher than the case building
	Distance from the adjacent building	H16	Equal or less than 4 m
			Between 4 m and 8 m
			Between 8 m and 15 m

: facade functionality, building orientation, and building surroundings. Facade functionality encompasses factors such as the cladding materials (e.g., glass, stone, concrete masonry units (CMU), precast panels, and aluminum), geometric complexity and regularity, presence of protrusions or recesses, distinct architectural features, branding elements, and services, such as HVAC ducts and piping. Building orientation, specifically the extent to which the facade faces north, can also affect PV suitability. Lastly, the heights of adjacent buildings relative to the studied structure and their proximity are key considerations in the building surroundings category.

To conduct a comprehensive assessment, the existence of each identified hurdle was systematically examined for the case study buildings, as indicated in

Table 2. Occurrence of a hurdle.

Building Types		H1	H2	H3	H4	H5	H6	H7	H8	H9	H10	H11	H12	H13	H14	H15	H16
Shopping mall building	M-1		1	1					1		1	1	1	1	1	1	1
	M-2			1			1	1		1	1			1	1		1
	M-3			1		1	1				1				1	1	1
Office building	O-1														1	1	1
	O-2					1	1					1			1	1	1
	O-3					1									1		1
Hotel building	HT-1					1	1	1							1
	HT-2	1			1						1				1	1	1
	HT-3			1				1							1	1	1
Hospital building	HO-1			1	1						1				1
	HO-2		1			1					1				1	1	1
	HO-3				1		1				1				1	1	1
Total		1	2	5	3	5	5	3	1	1	7	2	1	2	12	8	10

. The binary notation of 1 signifies the presence of a particular impediment, while the lack thereof is represented by a null value. This meticulous evaluation enables a holistic understanding of the site-specific constraints influencing the feasibility of PV integration on commercial building facades. Architectural and functional requirements impose significant constraints on the application of solar panels on building facades. Glazing, shading systems, irregular geometries, projections, and surface features may cover substantial parts of the facade surface [13,27,28]. Openings need to be avoided to maintain building functionality. Services fixtures and building maintenance-related aspects also limit usable areas. Architectural drawings helped in mapping functionality-related design constraints. On-site surveys further revealed permanent service fixtures and openings. The restricted zones were marked out to enable accurate estimation of PV potential. Facade orientation plays a critical role in determining solar irradiation and, thereby, PV output. North-facing vertical surfaces receive highly oblique and diffused radiation in the northern hemisphere. East and west orientations also witness variable solar access throughout the day compared to optimal south-facing exposure. To account for orientation effects, minimum irradiation thresholds were defined based on economic feasibility requirements. Facade zones not meeting the insolation levels as per orientation were designated as restricted areas. This ensured solar accessibility was objectively evaluated before estimating PV potential. Shading from neighboring structures and site features can markedly reduce solar irradiation on building facades. The impact depends on the height, distance, and geometry of the surroundings relative to the facade [29,30]. To determine shading, surrounding structures were modeled as per on-site measurements. Solar analyses mapped the incident irradiation on facades considering obstructions. Areas receiving inadequate insolation due to shading effects were excluded from PV potential calculations. After identifying all the possible hurdles, the status of presence was also checked, as stipulated in Table 2.

3.3. Buildings’ Analysis

The analysis of the selected commercial buildings focused on three key aspects that significantly influenced the utilizability of their facades for photovoltaic (PV) applications: building envelope functionality, building orientation, and building surroundings. By examining these factors in depth, the study aimed to determine the potential for PV integration on the facades of various types of commercial buildings.

3.3.1. Building Envelope Functionality

The utilizability of building facades for PV application is a complex function of various architectural, structural, and aesthetic parameters. Commercial buildings, in particular, exhibit significant variation in the facade utilizability factor (UF) due to their highly customized designs, which often incorporate unique combinations of structural details, architectural features, orientation, surroundings, and aesthetic elements. Determining the viability of PV application on commercial building envelopes necessitates a thorough assessment of the total facade area and its functional characteristics. Commercial building facades frequently feature a range of aesthetic finishes, such as glazing combinations, natural stone cladding, marble surfaces, and aluminum cladding (Figure 2). The choices of facade material and system play a crucial role in the potential integration of PV systems [31].

The analysis revealed that the PV utilizable area varied greatly depending on the type of building. The PV utilizable area for individual buildings ranged from 0% to over 48%. The average utilizable area was found to be 25% for hospitals, 12% for shopping malls, 44% for offices, and 31% for hotels. Across all studied buildings, the average utilizable area was 31%. These findings highlight the significant influence of building envelope functionality on the potential for PV integration in commercial buildings. Shopping malls were found to have the lowest potential for PV use, while office buildings exhibited the highest potential. This can be attributed to the distinct architectural designs and facade systems employed in these two building typologies. Shopping malls tend to adopt low-rise, large-span structures with predominantly opaque, solid facade materials, such as precast concrete cladding or concrete masonry units, which significantly reduce the available surface area for PV applications. In contrast, office buildings tend to have a more modern appearance with greater glazing areas, thus offering a higher potential for PV integration. Hospital buildings often exhibit a mix of these two approaches. In summary, the design characteristics of shopping malls make them more suitable for rooftop PV applications [32], while facade-integrated systems are more viable for hotels and office buildings [33].

The assessment of building functionality constraints commenced with an evaluation of the facade material and system. Integrating PV systems with solid facade systems, such as concrete, poses significant challenges and may compromise aesthetics. Moreover, replacing existing expensive marble or stone cladding with PV systems is often unfeasible from both social and financial perspectives. The presence of building services’ elements, such as HVAC ducts, plumbing, and ventilation components, such as chimneys, on the facade was also identified as a potential hurdle to PV integration. Signage and branding elements on facades present additional challenges for PV applications. In some cases, the facade design and color scheme may be a specific representation of a brand identity, which building owners are reluctant to compromise by concealing with PV panels. Considering these critical building envelope features, this study focused on the application of thin-film PV facade glazing as a potential solution. The analysis also revealed that the typology or design of the facade impacts solar accessibility. Features such as recesses, projections, overhangs, fins, louvers, and other shading elements can cast shadows and occupy significant facade space. Irregular envelope geometries are incompatible with standardized PV products. These diverse architectural and visual constraints necessitate customized BIPV designs catering to both functional and aesthetic considerations of different commercial facades. A granular analysis of facade characteristics is thus essential to identify and leverage solar potential through bespoke BIPV integration.

Based on the facade material and functionality analysis, suitable BIPV products were identified for the viable facade areas. For glazing facades, crystalline silicon and thin-film PV glazing options were suggested based on visibility needs. Prefabricated metal PV cladding systems were proposed for zones with metal facades. Flexible stick-on PV panels were indicated for flat concrete surfaces.

3.3.2. Building Orientation

Building orientation is a crucial factor that significantly influences the amount of solar radiation incident on building facades and, consequently, the energy output of building-integrated photovoltaic (BIPV) systems [34]. Facade orientation affects the angle of incidence of solar radiation as well as diurnal and seasonal variation in insolation [29]. North-facing vertical surfaces in the northern hemisphere receive highly oblique incident radiation, leading to significant reductions in energy yield. East- and west-facing facades exhibit large differences in solar access throughout the day. The optimal orientation for maximizing PV output is location-specific based on latitude and climate, but south-facing orientations are preferable for maximizing annual energy yields in most regions. The solar energy potential of a BIPV system is determined by the combination of the PV utilizable area and the building orientation [35].

To investigate the impact of building orientation on the applicability of BIPV in the studied commercial buildings, the orientations of the 12 selected buildings were determined, and 3D models of each building were developed using Google SketchUp^® Version 4.0. The incident solar radiation on the building facades was then simulated based on their respective orientations using BIMsolar^® software. Determining the minimum threshold of solar radiation required for economically viable BIPV application is essential for assessing the suitability of building facades. This threshold is influenced by various factors, including the desired payback period of the BIPV system, which is a reflection of the client’s financial expectations and affordability.

To gain insights into the preferred payback period for BIPV systems in the local context, a questionnaire-based survey was conducted among building industry professionals and owners. The survey aimed to capture the broader socioeconomic factors influencing the adoption of BIPV in commercial buildings, with a specific focus on the acceptable payback period. The survey employed a web-based questionnaire to collect responses from architects, engineers, building owners, and contractors. A pilot study was conducted to ensure the clarity, brevity, and user-friendliness of the survey, minimizing potential issues associated with web-based surveys, such as low response rates and technical difficulties. The questionnaire primarily consisted of closed-ended questions to guide respondents and save time, with an option to provide additional comments if desired. Respondents were asked about their professional background, familiarity with PV systems, expectations from BIPV, and the payback period that would persuade them to install BIPV in their buildings. Respondents’ feedback on their professional job/trade and familiarity with the PV system is highlighted in

Table 3. Breakdown of respondents by job/trade.

Profession/Trade	No. of Respondents
Contractors	17
Designers	19
Developers/Owners	14
Total	50

and

Table 4. Respondents’ familiarity with PV technology.

	Designer	Developer	Contractor	Overall
Highly familiar	2	1	1	4
Fairly familiar	9	2	2	13
Slightly familiar	6	5	10	21
Not familiar at all	2	6	4	12

. The maximum preferred payback period is described in

Table 5. Maximum acceptable payback period.

Period (Years)	No. of Responses
10	13
8	21
5	16

. The survey results revealed that nearly 75% of the respondents considered a payback period of eight years or less as acceptable for BIPV systems. This finding aligns with the preferences reported in the international PV market and research literature [31,36,37]. Consequently, the present study adopted an eight-year payback period as the benchmark for determining the minimum acceptable level of solar radiation for economically viable BIPV applications.

To estimate the annual energy production of a BIPV system, the following equation was used:

$$E=A\times r\times H\times PR$$

(1)

where:

E = energy output (kWh),

A = area of PV modules (m²),

r = solar panel yield (%),

H = annual average irradiation on tilted panels, excluding shading effects (kWh/m²/year),

PR = performance ratio, accounting for system losses.

In order to calculate the performance ratio, the losses listed in

Table 6. Modeled PV characteristics.

Dimensions (mm)	2009 × 1232
Pmax (W)	100
Module efficiency (%)	8

were considered. The performance ratio was calculated by considering various system losses, including inverter losses (6%), temperature losses (9%), DC cable losses (2%), AC cable losses (2%), and losses due to dust and humidity (2%) [38,39]. The characteristics of the modeled PV modules and the BIPV system losses are presented in Table 6 and

Table 7. PV output losses.

Type of Loss	%
Inverter losses	6%
Temperature losses	9%
DC cable losses	2%
AC cable losses	2%
Losses due to dust and humidity	2%

, respectively.

Considering the annual average daily solar radiation of 2000 kWh/m²/year in the eastern part of Saudi Arabia [40] and the current electricity tariff for commercial buildings of approximately USD 8 cents/kWh [41], the payback period for any BIPV system can be readily computed. For the modeled BIPV system with an estimated cost of USD 0.75/watt, the minimum annual solar radiation required to achieve an eight-year payback period was calculated to be 698 kWh/m² (

Table 8. PV system characteristics.

Parameter	Normal Radiation Case	Min. Radiation Case
E = Energy (kWh)	335	117
A = Total solar panel area (m2)	2.5	2.5
Module efficiency (%)	8%	8%
H = Annual average irradiation on tilted panels (kWh/m2/year)	2000	698
PR = Performance ratio, coefficient for losses	0.81	0.81

). Consequently, this study considered only those facade surfaces that annually receive a minimum radiation level of 698 kWh/m² as suitable for BIPV application.

The results showed that for an annual radiation level of 2000 kWh/m², the PV system would generate 117 kWh of energy annually, equating to a value of USD 26.8 (Table 8). To achieve a payback period of eight years, the minimum level of annual solar radiation was determined to be 698 kWh/m² (

Table 9. Payback period calculation.

PV system cost	USD 75
PV production value	USD 9.36
Payback period	8 Years

). Based on these findings, our study considered only those facade surfaces that annually receive a minimum radiation level of 698 kWh/m² for PV application.

3.3.3. Building Surrounding Obstacles

To assess the incident radiation on each building’s facade orientation, we utilized BIMsolar^® simulation software. The meteorological data file for Dhahran city was imported into the software to ensure accurate results. Any facade areas that were suitable for PV application but did not receive sufficient radiation were excluded from further analysis. The surroundings of a building significantly influence the solar potential of facades, especially in urban contexts, as nearby structures and terrain can obstruct access to direct irradiation. Structures in close proximity with greater heights can cast extensive shadows on a subject building’s facade. The shading impacts vary based on the geometry, orientation, and positioning of the neighboring elements in relation to the facade. To accurately assess the potential of building facades for PV application, it is crucial to consider the shading effects caused by the local built environment.

This study adopted a systematic approach to evaluate and quantify the shading impacts of neighboring structures on commercial building case studies. The first step involved on-site surveys of the buildings’ surroundings. Data were gathered on the heights, distances, and orientations of adjacent structures using laser meter measurements. The positions of terrain features causing horizon shading were also recorded. The geometry data were used to create detailed 3D models of the objects surrounding each building using building information modeling software. This setup accurately modeled the real-world context to enable shading simulations.

To perform the shading analysis of the surrounding structures, first, the meteorological data file for Dhahran was imported into BIMsolar^® to ensure accurate simulation of local solar irradiation conditions. The 3D models of the case study buildings and their surroundings were then simulated to assess the impact of shading on the incident radiation levels on building facades. Figure 3a,b illustrate the modeled buildings with their surrounding structures. The shading analysis considered factors such as the sun’s position, atmospheric conditions, and the reflectivity of surrounding surfaces.

Significant variations were observed in shading effects across commercial building categories based on their urban contexts. Office buildings generally showed minimal shading owing to spacious surroundings and comparable building heights. Hotels and hospitals exhibited moderate shading losses with average neighborhood densities. Extensive shading was seen for shopping malls, which are frequently surrounded by much taller structures in commercial complexes. The results of the shading analysis were used to refine the assessment of the utilizable facade area for PV application. Facade surfaces that received insufficient solar radiation due to shading from surrounding obstacles were excluded from the PV potential calculations. This approach ensured that only viable facade surfaces were considered for PV installation, leading to more accurate estimates of the potential energy generation and economic feasibility of BIPV systems.

3.4. Utilization Factor

The utilization factor (UF) is a key parameter that quantifies the proportion of a building’s facade area that can be effectively used for solar PV applications. It is influenced by various factors, such as the facade functionality, building orientation, and the surrounding environment. The utilizability factor (UF) was defined in this work as the ratio of the facade area suitable for PV application to the total facade area. It was determined by subtracting the facade area affected by restrictions from the total facade area. The UF values computed for the commercial buildings in this study are summarized in

Table 10. Utilization factors of the case study buildings.

Building No.	Category	Building Name	Total Facade Area (m2)	Building Facade Functionality (m2)	Building Orientation (m2)	Building Surrounding Factor (m2)	UF
1	Hospital	H-1	3616	892	494	494	0.14
2		H-2	5616	1521	1375	813	0.14
3		H-3	6781	1566	493	404	0.06
Total for hospitals			16,013.02	3979	2362	1711	0.11
4	Shopping mall	M-1	4130	1956	0	0	-
5		M-2	2946	0	0	0	-
6		M-3	8947	0	0	0	-
Total for shopping malls			16,023	1956	0	0	-
7	Office	O-1	13,913	5870	5870	5870	0.42
8		O-2	5760	858	682	506	0.09
9		O-3	11,355	6852	4859	4859	0.43
Total for offices			31,028	13,580	11,411	11,235	0.36
10	Hotel	T-1	35,422	7891	1955	1955	0.06
11		T-2	21,044	10,046	6193	6193	0.29
12		T-3	5976	1125	836	506	0.08
Total for hotels			62,442	19,062	8984	8654	0.14
Overall Total			125,506	38,577	22,757	21,600	0.172

. Significant variations were observed across categories, with shopping malls exhibiting extremely low UF, while office buildings displayed the highest solar accessibility.

The total facade area of the studied buildings ranged from 1616 m² to 13,905 m², with the shopping malls generally having the largest facade areas. However, the utilizability of these facades for PV applications varied significantly across the different building categories. The hospital buildings had an average UF of 11%, with individual buildings ranging from 6% to 14%. This relatively low UF can be attributed to the complex facade designs, the presence of architectural features, and the influence of surrounding structures. Shopping malls exhibited the lowest average UF of 0%, with all three studied buildings having no usable facade area for PV applications. This can be primarily attributed to the presence of large signage, brand-specific design features, and the extensive use of opaque materials, such as precast panels and concrete masonry units (CMU). In contrast, office buildings demonstrated the highest average UF of 36%, with individual buildings ranging from 25% to 48%. The modern architectural designs, extensive use of glazing systems, and the relatively unobstructed surroundings contributed to the higher utilizability of office building facades for PV applications. Hotels showed an intermediate average UF of 12%, with individual buildings ranging from 5% to 25%. The varied facade designs, the presence of balconies and projections, and the influence of surrounding structures resulted in a moderate utilizability of hotel facades for PV applications. The overall average UF for all the studied buildings was found to be 16%, highlighting the significant impact of architectural features, building orientation, and surrounding factors on the potential for PV application on commercial building facades. These findings are consistent with previous studies that have reported UF values ranging from 10% to 40% for various building types. The low utilization factors observed in this study underscore the challenges in applying PV on commercial building facades. The diverse and often unique combination of architectural features, materials, and functional requirements in these buildings poses significant hurdles for PV integration. However, it is important to recognize that even with low utilization factors, the vast facade areas of commercial buildings still present significant opportunities for PV application.

These results underscore the importance of considering the utilization factor when assessing the potential for PV application on commercial building facades. The significant variation in UF across different building categories emphasizes the need for a case-specific approach in evaluating the feasibility of PV systems. Architects, engineers, and building owners should take into account the facade functionality, building orientation, and surrounding factors during the early stages of building design to optimize the utilizability of facades for PV applications.

4. Conclusions

This study presented an assessment of the utilizability of commercial building facades for solar PV applications in the hot desert climate of Saudi Arabia. The research employed a multifaceted approach, considering various architectural, technical, and economic factors that influence the feasibility of facade-integrated PV systems. The methodology combined detailed building audits, stakeholder surveys, solar modeling, and PV performance simulations to provide a robust and context-specific evaluation of facade PV potential.

The findings highlighted the significant influence of architectural design, facade characteristics, building orientation, and urban context on the utilizability of facades for PV applications. The study revealed that the average facade area suitable for PV deployment varied considerably across different commercial building typologies, ranging from 0% for shopping malls to 36% for office buildings. Hotels and hospitals showed intermediate UF values of 14% and 11%, respectively. Overall, the average UF for all buildings was found to be just 16%, underlining the substantial limitations posed by contemporary commercial facade configurations. The study revealed that, on average, 31% of the total facade area of the investigated commercial buildings was free from physical restrictions, such as obstructions, geometric complexities, and material constraints, making it potentially suitable for PV deployment. However, the actual utilizable area was further reduced by factors related to solar access and economic viability. A key finding of the study was the minimum solar irradiation threshold of 698 kWh/m² required for a facade PV system to achieve a payback period of eight years, as determined by a survey of local building stakeholders. Facade zones receiving less than this threshold level due to orientation effects constituted an additional 12.1% reduction in the utilizable area. Shading from surrounding structures accounted for a further 0.92% decrease in the suitable facade surface. These results underscore the importance of considering building-specific factors when assessing the viability of facade-integrated PV systems. The study emphasized the importance of a comprehensive, multi-criteria assessment approach that goes beyond simple geometric considerations to determine the true potential for PV deployment on building envelopes. Building design and architecture, construction materials, and weather conditions are quite similar across the GCC region. The findings of the study are, therefore, applicable to other countries in the region. The identified hurdles and the analysis approach can be helpful for facade BIPV analysis in other parts of the world.

Future research should expand the scale of analysis to neighborhood and city levels, exploring the aggregate PV potential of commercial building facades and the implications for urban energy systems. Detailed case studies of successful facade PV installations can provide valuable lessons on design integration, construction processes, and operational performance. Techno-economic analysis of emerging facade PV technologies, such as semi-transparent and colored PV modules, can help identify cost-effective solutions that balance energy production and architectural aesthetics. The UF methodology could be enhanced by incorporating user preferences, economic factors, thermal performance, and structural suitability. Detailed BIPV performance modeling and lifecycle assessment can provide more nuanced projections of energy, emissions, and cost outcomes. The urban-scale implications of widespread BIPV deployment also warrant investigation.