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International Conference on Innovative Applied Energy    

E-Proceedings ISBN: 978-1-912532-05-6

St Cross College, University of Oxford, United Kingdom



A Model for Solar Energy Utilization in Buildings: Impact of Inclination Angle & Orientation with Shadow Patterns



Mohamad Araji

Environmental Design, University of Manitoba, Canada



Paper Abstract

This paper developed a new mathematical model to estimate the performance of building integrated photovoltaics (BIPV). Adapting a net-zero energy footprint with various form-finding typologies resulted in effective parametric design explorations for solar power. Contemporary studies in literature aimed to optimize building envelopes for better energy production, including genetic algorithms and neural networks, feasibility of vertical photovoltaics on high-rise buildings, implications of urban settings for BIPV, determination of insolation on BIPV influenced by shadow and inclination angle, methods for shading-loss analysis in BIPV systems, and building massing on net-zero achievability. However, such studies generally rely on optimizing envelope features while keeping the building form fixed. Relieving this constraint presents limitless opportunities in terms of energy production performance. In order to tap into the latent potentials of BIPV, this paper analyzed indicators of building’s consumption (C), height (h), aspect ratio (AR), surface-area-to-volume ratio (SA-V), and orientation (Or) in addition to the effect of inclination angle (β) on energy targets. The mathematical model was developed based on: 1) Impact factors in PV energy production, 2) Building form utilizations, 3) Sensitivity analysis of net-zero energy and BIPV, 4) Geometry parameters, and 5) Energy consumption and production measures. Using the Perez model, the energy production incorporated irradiance components of plane-of-array’s beam, sky diffuse and ground-reflected diffuse with view factors calculated based on non-shaded isotropic surfaces and cumulative shading factor. The time interval for which the radiation is measured plays an important role in terms of energy production. It became evident that the longer this interval, the smaller the calculated ratio between diffuse and global radiation. Applying de Bilt’s optimization model, the diffuse component relationship to the sky condition and ratio between global and extra-terrestrial radiation were utilized with a correction depending on the solar angle. At various energy production thresholds, the results established: 1) H to AR relationship for a given Or and β, 2) BIPV performance as a function of the SA-V ratio, under a set of Or, β, and C, and 3) A function of β and H for various energy targets. It was found that higher AR and H values lead to improved energy performance. At H = 0.7, a 1.26 increase in AR resulted in an extra 10% energy production close to net-zero thresholds. The unit increase of net energy with SA-V ranged in (0.21,0.36) is 4.7 kWh/m2/m-1 for β values corresponding to the tested optimal set. The impact of building height is well pronounced for net-zero energy, especially at higher consumption levels. In a specific location, a percent reduction of d units in shading is equivalent to an increase of 1.12d degrees in β for same energy production. 

Paper Keywords
Renewable energy integration in buildings; Optimal inclination angle and orientation for photovoltaics; Adverse effect of shadow on building integrated photovoltaics; Building surface-area-to-volume ratio; Net-zero energy.
Corresponding author Biography

Dr. Mohamad T. Araji is an Assistant Professor of Environmental Design at University of Manitoba, Canada. His specialty involves theoretical and numerical modelling for building integrated renewable energy, sustainable design systems, physics simulation, and form-finding optimization. Dr. Araji has contributed at numerous American and European institutes, and received wide-ranging awards/fellowships including his tenure as TÜV Süd Visiting Professor at the Technical University of Munich in 2014. As a practitioner, he has worked on the Chicago DeCarbonization Plan, the Masdar Headquarters, and the World’s tallest building Jeddah Tower. Dr. Araji is a building scientist who holds a Ph.D. in Architecture from University of Illinois at Urbana Champaign, USA.

The International Conference on Innovative Applied Energy (IAPE’18)