Grid-Aware Layout of Photovoltaic Panels in Sustainable Building Energy Systems

Abstract

In the context of increasing concern for anthropogenic CO2 emissions, the residential building sector still represents a major contributor to energy demand. The integration of renewable energy sources, and particularly of photovoltaic (PV) panels, is becoming an increasingly widespread solution for reducing the carbon footprint of building energy systems (BES). However, the volatility of the energy generation and its mismatch with the typical demand patterns are cause for concern, particularly from the viewpoint of the management of the power grid. This paper aims to show the influence of the orientation of photovoltaic panels in designing new BES and to provide support to the decision making process of optimal PV placing. The subject is addressed with a mixed integer linear optimization problem, with costs as objectives and the installation, tilt, and azimuth of PV panels as the main decision variables. Compared with existing BES optimization approaches reported in literature, the contribution of PV panels is modeled in more detail, including a more accurate solar irradiation model and the shading effect among panels. Compared with existing studies in PV modeling, the interaction between the PV panels and the remaining units of the BES, including the effects of optimal, scheduling is considered. The study is based on data from a residential district with 40 buildings in western Switzerland. The results confirm the relevant influence of PV panels’ azimuth and tilt on the performance of BES. Whereas south-orientation remains the most preferred choice, west-orientationed panels better match the demand when compared with east-orientationed panels. Apart from the benefits for individual buildings, an appropriate choice of orientation was shown to benefit the grid: rotating the panels 20° westwards can, together with an appropriate scheduling of the BES, reduce the peak power of the exchange with the power grid by 50% while increasing total cost by only 8.3%. Including the more detailed modeling of the PV energy generation demonstrated that assuming horizontal surfaces can lead to inaccuracies of up to 20% when calculating operating expenses and electricity generated, particularly for high levels of PV penetration.

Potential of Photovoltaic Panels on Building Envelopes for Decentralized District Energy Systems

“…The model derives from the BES framework described by Stadler (2019), to which the reader is referred for further details. In this paper, special attention is dedicated to the further development of the oriented irradiation modeling proposed in earlier work from the authors Middelhauve et al (2021), which is modified to include the modeling of shading effects between different buildings in the districts similar to the work by Schüler (2018).…”

“…In this study, the validity range for PV installations has to be extended in comparison to previous studies (Middelhauve et al, 2021), in order to allow full installations on the building's envelope. Simply extending the interval would drastically overestimate the cost for extensive PV installations, whereas linearizing the cost function in the vicinity of higher PV sizes would penalize small rooftop installations.…”

“…The skydome discretization (Robinson and Stone, 2004) is applied using the Ladybug plug-in of the Grasshopper suite (Roudsari and Adrian Smith Gordon Gill Architecture, 2013) to include the oriented irradiation into MILP formulation. For more information about modeling-oriented irradiation in MILP problems, the reader should refer to Middelhauve et al (2021) and Schüler (2018). In the remaining part of this section, the focus is on the inclusion of facades, the main element of novelty in this work.…”

“…The sky limiting angle in each azimuth direction is then used to determine the shaded irradiation. Thereby, the method is similar to the calculation of intermodular shading of PV modules on flat roofs (Middelhauve et al, 2021).…”

“…However, in most cases, these studies rely on the use of global irradiation to model the incoming solar radiation. This corresponds to assuming horizontal panels (Duffie and Beckman, 2013), a simplification that was shown to generate a relevant error (overestimation or underestimation, depending on the case) in the calculation of how much energy is generated by solar systems (Middelhauve et al, 2021). Therefore, based on the aforementioned literature review and to the best of our knowledge, we believe that there is a gap in the academic literature related to the intersection of energy system design in buildings and the solar potential on facades.…”