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Mean monthly roof heat flux contributions to cooling and heating loads for 2009. Cooling load is average load during 0800-2000 PST on cooling days. Heating load is average load over the entire heating day. Negative heating load means that the roof heat flows into the building on a heating day. Numbers in italics represent months with 2 or less days of cooling or heating. CDD: cooling degree days. HDD: heating degree days.
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Indirect benefits of rooftop photovoltaic (PV) systems for building insulation are quantified through measurements and modeling. Measurements of the thermal conditions throughout a roof profile on a building partially covered by solar photovoltaic (PV) panels were conducted in San Diego, California. Thermal infrared imagery on a clear April day dem...
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... Existing solar panels are installed within the size of building roofs with little space between the roof and PV panel, which remains insufficient for air circulation as this not only contributes to a reduction in the efficiency of solar panels but also the temperature of solar panels rises. One benefit of rooftop solar panels is using them as a secondary insulation layer to provide shade beneath it [8][9][10]. Hence, this method transfers less heat into the building through the roof. ...
This research aimed to investigate the potential for reducing building temperatures by installing photovoltaic (PV) panels at an optimal height above the roof, allowing them to cast shade while generating electricity. The panels function as artificial insulation, reducing heat transfer to the building. A scaled model made from Balsa wood (0.50 m x 0.80 m x 0.97 m) with an aluminium shading plate (2.00 m x 0.90 m) was constructed to test this. The model was placed outdoors, exposed to direct sunlight from 9 a.m. to 5 p.m., and equipped with devices such as VELOCICALC for air temperature and velocity measurements, as well as an infrared thermometer for wall, roof, and plate temperature profiling. Simulations were also conducted using SketchUp and Computational Fluid Dynamics (CFD) to assess the optimal height of PV panels for three building types: a high-rise, a terrace, and a semi-detached house—PVSYST software estimated electricity generation based on roof size. Results indicated a maximum temperature reduction of 7°C and electricity cost savings of 25% to 30% when the buildings were shaded from 11 a.m. to 3 p.m. Implementing PV panels based on roof size showed the potential to generate up to RM 34,000 monthly. These findings demonstrate that hovering PV panels can provide significant energy savings and reduce cooling loads, making this approach a viable solution for sustainable building design.
... Based on existing studies, RMS configurations for measurements can be designed to better compare the energy efficiency and thermal performance of buildings. 17,19,20,23,27,32,36,52 Summer, Transitional season 34,35 All year 42,50 Csa, Csb Summer 49 Transitional season 24 All year 18,22,48 RMSs research methods shapes, RMSs parameter settings, weather conditions in the simulations, and the oversimplification in the heat transfer of RMSs, leading to an underestimation of roofs' role in mitigating energy demand 34 . Therefore, it is urgent to address the limited availability of systematic comparative studies on the thermal performance of PV systems and cool coating RMSs, as well as to develop prediction tools for the thermal performance of such roofs. ...
The thermal behavior of roofs significantly impacts the indoor thermal environment. Rooftop mitigation strategies (RMS), as effective measures to reduce cooling load and improve indoor thermal comfort, have been extensively studied. However, the lack of comparative experimental RMS studies and the limitations of simulation software in accurately reproducing RMS thermal performance post-implementation highlight research gaps. This study utilized reduced-size models to investigate the thermal performance of RMSs - cool coating roof, photovoltaic (PV) roof, and PV cool coating roof - across summer, transition season, and winter, and further developed internal roof surface temperature prediction models through theoretical analysis and experimental data calibration. The results demonstrated that all RMSs outperformed a reference roof in reducing both interior and exterior temperatures, with cool coating roof exhibiting the best thermal performance in summer. The ranking of the internal thermal performance of RMS in summer from best to worst was as follows: cool coating roof, PV cool coating roof and PV roof. In transitional season and winter, PV roof had the lowest exterior surface temperature and PV coating roof had the lowest interior surface temperature. The maximum internal surface temperatures of the cool coating roof in summer were 1.6 °C and 1.5 °C lower than those of PV roof and PV cool coating roof, respectively. The combination of PV and cool coatings only provided better cooling effects in terms of interior surface temperature during the transitional season and winter. This study provides insights for decision-making regarding RMS in subtropical hot and humid regions.
... Photovoltaic (PV) roofs and thermal coating solutions are becoming increasingly popular as strategies for energy efficiency and comfort enhancement in buildings. Photovoltaic roofs offer numerous advantages, such as local electricity production and shading for various surfaces [17][18][19]. Studies have shown that the success of energy reduction strategies with photovoltaic panels depends on the size of the PV panel system and the availability of roof space. ...
... In warm climates, roofs contribute significantly to the cooling load of buildings, making cool roofs and coating solutions particularly valuable. Research in regions like the Colombian Caribbean, the Mediterranean climate zone of Algeria, and other locations has demonstrated the potential of coating solutions in reducing cooling requirements [17][18][19]. ...
Thermal coating paints offer a passive strategy to reduce heat gain in buildings, improve ventilation, and lower energy consumption. This study investigates the effectiveness of these technologies by comparing different housing structures and environmental conditions. Specifically, it examines thermal envelope solutions for cool roofs in homes along the Colombian Caribbean Coast. We quantify the thermal impacts using experimental data collected from 120 houses across eight municipalities in the Magdalena Department, Colombia. The research details the technology and analytical methods employed, focusing on thermal reductions achieved through thermal coatings to potentially reduce energy demand. A comprehensive measurement system, incorporating temperature and humidity sensors, is developed to assess the impact of the coatings. Thermal comfort is evaluated according to the ASHRAE 55 standard, with temperature reductions calculated for each house treated with thermal coatings. A methodology is applied to evaluate the thermal reduction between a house with a coating solution versus a house without it. The results show a temperature reduction on a house-by-house basis, from 1.5% to 16%. On average, the results yield a significant 7% reduction in thermal load. Additionally, a mobile application is developed to disseminate the results of this research, promoting the social appropriation of science among the involved communities.
... They also have an indirect effect on the energy performance of the building by providing shade under the panels and absorbing solar radiation. This contributes to reducing heat gain on the roof (Dominguez et al., 2011). Utilizing solar energy, green roofs are the addition of a garden on top of a ground slab, which can include various layers such as planting, soil, waterproofing and drainage (Abuseif and Gou 2018). ...
In recent years, increasing interest in environmental sustainability and energy efficiency has made the combined use of renewable energy sources in landscape design an important agenda item. Landscaping not only fulfills aesthetic and functional needs, but also serves the purpose of reducing energy consumption and conserving natural resources through environmentally friendly practices. Renewable energy sources such as solar, wind and biomass are used in various ways in landscaping projects, allowing solutions to be developed in harmony with the natural environment. The use of renewable energy sources in landscaping offers important opportunities to increase environmental sustainability and energy efficiency. In these studies, various renewable energy sources such as solar energy, wind energy, biomass and geothermal energy can be integrated without harming the aesthetic and functional characteristics of the natural landscape. Technologies such as solar panels and wind turbines support energy production in landscapes, while the use of biomass enables waste recycling and organic energy production. In addition, geothermal energy can be used for environmental heating and cooling, providing indirect benefits to landscape design. This study aims to provide innovative solutions in landscape design by examining how renewable energy sources can be integrated into landscape projects, their environmental benefits and their contribution to sustainable development goals.
... Comparing those two roof types, the BR + PV shows its highest heat gain during summer season of 2.5 kWh/m 2 in July and exhibits during the entire summer months a smaller heat gain through the roof compared to the BR, which has its highest heat gain of 7 kWh/m 2 during the summer months in July as well. The lower convective heat flux of the BR + PV compared to the BR is ascribed to the shade provided by the panels which reduce the short-wave incident on the roofs surface, resulting in lower surface temperatures [14,24,92]. Consequently, the BR is the less appropriate option for reducing heat gain through the roof during the summer season. ...
The European Union has emphasized policies promoting photovoltaic (PV) energy generation to achieve the United Nations' Sustainable Development Goals 7 and 13. Notably, building roofs suitable for PV panels also present opportunities for passive energy-saving methods, such as green roofs. Both approaches impact beyond buildings to the urban level; PV panels intensify the urban heat island (UHI) effect, while well-irrigated green roofs mitigate it. In the Mediterranean region, where cities face challenges from extreme weather events and droughts leading to water restrictions, a comprehensive analysis of the influence of these approaches at both the building and urban levels becomes crucial. This work addresses this gap by employing dynamic simulations of a typical Mediterranean roof, an extensive green roof and a summer-irrigated green roof, all with and without PV panels, under Mediterranean climate. While both green roofs and PV systems prove beneficial at the building level, only irrigated green roofs effectively reduce the UHI impact. Unirrigated green roofs show no benefit on the UHI, whereas PV panels consistently amplify it. Combining an unirrigated green roof with PV panels has the highest UHI impact among all analyzed roof types. Summer irrigation of the extensive green roof can compensate the additional convective heat flux by PV panels, and moreover enhancing heat loss through the roof-a beneficial aspect at the building level during summer. The findings underscore the complexity of defining strategies that meet goals for renewable energy and UHI mitigation, highlighting the need for further research in this area.
... Recent studies suggest that cityscale RPVSP deployment might either decrease or increase urban temperatures [5][6][7] . For example, it has been observed that the deployment of RPVSP on a building not only curtailed greenhouse gas emissions but also reduced annual cooling loads 8 . Similar results have been observed in simulation-based studies and in the case of medium-to-large-scale RPVSP deployment [9][10][11][12] . ...
... As a result, air temperatures around RPVSPs tend to remain higher during the day, particularly in urban building environments. Moreover, higher air temperature was also observed in the gap between the RPVSPs and roof (~0.3 m) compared with the ambient air temperature 8,26 . This increase of 3.2 °C is indicative of the overall impact of the RPVSPs on urban temperature during peak hours at the city scale. ...
... Wang et al. 2020) which resonates with the 71.5% reduction observed in the current study for opaque shaded roof. Additionally, the peak surface temperatures of opaque shading materials (TSR) and exposed roof surfaces (TPR), observed in this study at around 60°C and 56-58°C respectively, closely align with similar findings from other studies on roofs shaded by horizontal PV panels (Dominguez, Kleissl, and Luvall 2011). The alignment of surface temperature measurements in this study with those from previous research on PV-shaded roofs supports the use of BPS tools for simulating solar PV as a shading material. ...
... Many residential and business buildings are increasingly equipped with rooftop solar panels to generate clean electricity. According to a study, using solar cells on residential and commercial roofs can reduce heat absorption and cooling demand by up to 38 % (or 5.9 kW h/m 2 ) [17]. Studies by Kapsalis and Karamanis [18] further confirm this benefit, finding that while solar cells on a Mediterranean roof may slightly increase winter heating needs (by 6.7 %), the summer cooling load reduction is significantly higher at 17.8 %. ...
Global warming and increased airconditioning demand drive up energy use. A passive cooling system for the building's roofs is one solution to this problem. The current study intends to provide a unique evaporative cooling concept for cooling building roofs that use significantly less water than prior approaches. To reduce room temperature, saturated-activated alumina beds with 2, 4, and 6 cm thicknesses were put over the roof. Pure and 35 PPT saline water were utilised to evaluate system performance and sustainability. The device successfully reduced rooftop temperatures by 84 % and 70.9 % after 24 h of testing (6 h during daytime and 18 h at night) under heat loads of 800 and 1000 W/m 2. The findings show that salt water is a feasible alternative to freshwater that does not sacrifice cooling efficiency. From an environmental standpoint , compared to a bare roof, a 6-cm layer of saturated activated alumina tables can reduce annual carbon dioxide emissions by 71.3 tCO 2 /m 2 and 92 tCO 2 /m 2 for roof areas subjected to daily solar radiation of 6000 W h/day and 4800 W h/day, respectively.
... The basic layers of an external wall are shown below: 22 Anna SZYMCZAK-GRACZYK, Julia KALKA, Barbara KSIT For all assumed roof cases, a bisolar green roof was adopted [28]. It is a green roof integrated with a photovoltaic panel installation system, where the green roof serves as ballast. ...
In contemporary literature, there are not many analyses taking into account changing heat transfer coefficients over the years and examining and comparing the variability of insulation thickness in different thermal standards. The article presents the evolution of energy demand taking into account the requirements of the Green Deal. The analysis was carried out using two materials, showing how their thickness changed in relation to the evolving energy requirements. The research was illustrated with an example of thermal modernization for a building in specific time periods. The analysis was carried out using a numerical program, comparing warming variants for individual years using the Index of annual primary energy demand. Following the requirements contained in the EPDB directive, a comprehensive reduction of the penetration coefficients for building partitions was proposed and requirements for the mandatory use of mechanical ventilation and photovoltaics were introduced.
... Studies suggest that strategically locating PVSPs on low reflective rooftops could mitigate UHI [5]. However, there are contrasting studies reporting a warming [6,7,8] or cooling effect [9,10,11]. For this reason, it is required comprehensive research using in situ measurements. ...
