Abstract
To improve the energy efficiency of dwellings, rooftop photovoltaic (PV) technology is proposed in contemporary designs; however, adopting this technology will add a new component to the roof that may affect its thermal balance. This paper studies the effect of roof shading developed by solar PV panels on dwellings’ thermal performance. The analysis in this work is performed by using two types of software packages: “AccuRate Sustainability” for rating the energy efficiency of a residential building design, and “PVSYST” for the solar PV power system design. AccuRate Sustainability is used to calculate the annual heating and cooling load, and PVSYST is used to evaluate the power production from the rooftop PV system. The analysis correlates the electrical energy generated from the PV panels to the change in the heating and cooling load due to roof shading. Different roof orientations, roof inclinations, and roof insulation, as well as PV dwelling floor areas, are considered in this study. The analysis shows that the drop in energy efficiency due to the shaded area of the roof by PV panels is very small compared to the energy generated by these panels. The analysis also shows that, with an increasing number of floors in the dwelling, the effect of shading by PV panels on thermal performance becomes negligible. The results show that insensitivity of the annual heating and cooling load to the thermal resistance of rooftop solar systems is only because the total thermal resistance is dominated by roof insulation.
Highlights
In building sustainability designs, three major assessments are considered: thermal performance, energy efficiency, and water conservation
The major factors affecting the thermal performance of buildings are basically related to the building architecture design, such as: the roof type, the roof orientation, shading from adjacent objects, building materials, insulation, and glazing
Part of the roof was covered with PV panels and a ceiling temperature measurement was conducted to verify and validate the mathematical heat transfer model
Summary
Three major assessments are considered: thermal performance, energy efficiency, and water conservation. Another work by Kotak et al [2] studied the effect of rooftop PV panels on the cooling load of a flat roof house using a computer simulation. It was found that installing a PV rooftop may reduce the cooling load by 35% for the roof design considered in that work (a gable roof without a significant insulation layer). The results showed that the contribution of solar energy to covering the demand of hot water and electricity of a building is higher in case of the flat roof than the gabled roof design. The proposed analysis correlates the electric energy generated from the PV panels to the heating and cooling load of a dwelling with a roof space design at different roof orientation angles
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