Solar and Shading Potential of Different Configurations of Building

sustainability Article Solar and Shading Potential of Different Configurations of Building Integrated Photovoltaics Used as Shading Devices Considering Hot Climatic Conditions Omar S. Asfour Department of Architecture, King Fahd University of Petroleum and Minerals, P.O. Box 2483, Dhahran 31261, Saudi Arabia; [email protected] or [email protected]; Tel.: +966-13-860-3594; Fax: +966-13-860-3210 Received: 23 October 2018; Accepted: 21 November 2018; Published: 23 November 2018 Abstract: This study investigates the use of building-integrated photovoltaics (BIPVs) as shading devices in hot climates, with reference to the conditions of Saudi Arabia. It used parametric numerical modelling to critically appraise the potential of eight design configurations in this regard, including vertical and horizontal shading devices with different inclination angles. The study assumed that the examined shading devices could be entirely horizontal or vertical on the three exposed facades, which is common practice in architecture. The study found that the examined configurations offered different solar and shading potentials. However, the case of horizontal BIPV shading devices with a 45◦ tilt angle received the highest amount of annual total insolation (104 kWh/m2) and offered effective window shading of 96% of the total window area on average in summer. The study concluded that, unlike the common recommendation of avoiding horizontal shading devices on eastern and western facades, it is possible in countries characterised with high solar altitudes such as Saudi Arabia to use them effectively to generate electricity and provide the required window shading. Keywords: building-integrated photovoltaics (BIPVs); solar energy; shading devices; architecture; Saudi Arabia 1. Introduction In recent decades, researchers have been actively engaged in studying renewable energy technologies, including their potential applications in buildings. These efforts are driven by the insecurity of fossil fuel supplies and the associated negative environmental impacts. One important renewable energy source in this regard is solar energy, which could be effectively used in buildings for water heating and electricity generation. This is even more effective in hot climates due to the abundant availability of solar radiation. One of the most promising technologies in this field is the use of building-integrated photovoltaics (BIPVs) to generate electricity in buildings. The following sections of this literature review provide some details in this regard. The main attention in this context is paid to the potential use of BIPV as shading devices in hot climatic areas such as Saudi Arabia. 1.1. BIPVs Concept and Applications Building-integrated photovoltaics (BIPVs), as opposed to building-applied photovoltaics (BAPVs), are simply photovoltaic (PV) systems that are used as integral parts of the building envelope. In this capacity, BIPV systems share the well-known advantages of BAPV systems such as providing an on-site renewable energy source that is silent, produces no hazardous emissions during operation, and requires relatively little maintenance during its expected lifetime of 20–25 years [1,2]. However, Sustainability 2018, 10, 4373; doi:10.3390/su10124373 www.mdpi.com/journal/sustainability Sustainability 2018, 10, x FOR PEER REVIEW 2 of 15 Sustainability 2018, 10, 4373 2 of 15 providing an on-site renewable energy source that is silent, produces no hazardous emissions during operation, and requires relatively little maintenance during its expected lifetime of 20–25 years [1,2]. BIPVHowever, modules BIPV develop modules the develop PV system’s the PV role system’s from arole mere from electrical a mere deviceelectrical to device a construction to a construction element thatelement could that be could used tobe enrichused to the enrich architectural the architectu designral instead design ofinstead disturbing of disturbing it [3]. BIPV it [3]. may BIPV replace may conventionalreplace conventional construction construction materials materials in parts of in the part buildings of the envelopebuilding usingenvelope different using forms, different including forms, panels,including foils, panels, tiles, foils, and glazing.tiles, and However, glazing. However, this should this be should done without be done compromising without compromising the required the functionalrequired functional qualities qualities of these of elements, these elements, including including structural structural rigidity rigidity and thermaland thermal insulation insulation [4]. One[4]. One of the of mostthe most common common forms forms of BIPVs of BIPVs is PV is PV integration integration into into building building roofs, roofs, see see Figure Figure1. This 1. This is possibleis possible in in a varietya variety of of forms forms such such as as roof roof cladding cladding [5 [5],], roof roof tiling tiling [ 6[6],], and and in in thethe roofingroofing ofof atriaatria andand skylightsskylights [[7].7]. BIPVs integrated into roofs have a great potentialpotential for harvestingharvesting solar radiation. However,However, therethere areare somesome designdesign challengeschallenges suchsuch asas partialpartial shading,shading, whichwhich requiresrequires aa detaileddetailed shadingshading analysisanalysis duringduring thethe designdesign phasephase [[8].8]. InIn hothot climates,climates, BIPVsBIPVs inin roofsroofs maymay experienceexperience excessiveexcessive heat, whichwhich reducesreduces theirtheir efficiency.efficiency. InIn thisthis case,case, aa properproper PVPV coolingcooling mechanismmechanism shouldshould bebe consideredconsidered atat earlyearly designdesign stagesstages [[5].5]. There isis alsoalso thethe challengechallenge ofof dustdust depositiondeposition overover PVPV panels,panels, especiallyespecially ifif dustdust isis coupledcoupled withwith highhigh humidity. ThisThis necessitatesnecessitates the use of regular dust-cleaning techniques [[9].9]. TheThe useuse ofof BIPVBIPV systemssystems inin buildingbuilding facadesfacades isis alsoalso commoncommon andand couldcould bebe implementedimplemented inin aa varietyvariety ofof forms. This This includes includes window window glazing glazing [10], [10 shading], shading devices devices [11], [ 11cladding], cladding and construction and construction of walls of walls[12], double-skin [12], double-skin facades facades [13], Trombe [13], Trombe walls walls [14], [et14c.], Some etc. Some examples examples are presented are presented in Figure in Figure 1. The1. Themain main advantage advantage of facade of facade integration integration is that is that PV PV panels panels are are made made visible visible for for people, people, which may bebe consideredconsidered asas aa visualvisual addedadded value.value. However,However, oneone ofof thethe mainmain challenges,challenges, inin thisthis case,case, isis thethe issueissue ofof shading,shading, whichwhich significantly significantly depends depends on on building building massing. massing. This This issue issue has tohas be to considered be considered in the in early the designearly design stage. stage. Further Furthe detailsr details on the on use the of use BIPVs of BIPVs as shading as shad devicesing devices is provided is provided in Section in Section 1.3 of this 1.3 literatureof this literature review. review. Pitched Roofs Flat Roofs Shading Devices Curtain Walls FigureFigure 1.1. SomeSome integrationintegration formsforms ofof photovoltaicsphotovoltaics intointo buildingbuilding facadesfacades [[15].15]. 1.2.1.2. BIPVsBIPVs Status in Saudi Arabia TheThe useuse of of BIPV BIPV systems systems is greatly is greatly related related to the localto the culture, local architecture,culture, architecture, and climatic and conditions climatic ofconditions each country. of each Several country. studies Several could studies be found could inbe thisfound context in this for context some for specific somecountries, specific countries, such as Bahrainsuch as Bahrain [9], Egypt [9], [16 Egypt], India [16], [17 India], Malaysia [17], Malaysia [18], Italy [18], [19 ],Italy and [19], Canada and [Canada20]. Saudi [20]. Arabia Saudi is Arabia an Arab is countryan Arab thatcountry has thethat largest has the oil largest reserves oil inreserves the world in the (about world 25%). (about It is 25%). considered It is considered the fastest the growing fastest electricitygrowing electricity consumer consumer in the Middle in the East. Middle In 2005, East. it In was 2005, the it world’s was the 15th world’s largest 15th consumer largest consumer of primary of energy,primary of energy, which overof which 60% over was petroleum-based60% was petroleum-bas [21]. Despiteed [21]. the Despite fact that the oil fact availability that oil availability is the main is drivingthe main power driving of power the Saudi of the economy Saudi economy so far, its so sustainability far, its sustainability is questioned is questioned considering considering the global the Sustainability 2018, 10, 4373 3 of 15 concern over fossil fuel supplies [22]. Saudi Arabia has considered this issue through the adoption of Saudi Vision 2030. One of the main objectives of this vision is to reduce Saudi Arabia’s dependence on oil and to diversify its economy in a more sustainable way. The Vision has set an initial target of generating 9.5 gigawatts of renewable energy in this regard. It also aims to localise a significant portion of the renewable energy value chain in the Saudi economy, including research and development and manufacturing

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