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Author

M. Samady

Bio: M. Samady is an academic researcher. The author has contributed to research in topics: Air conditioning & HVAC. The author has an hindex of 1, co-authored 1 publications receiving 7 citations.

Papers
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03 Aug 2010
TL;DR: In this paper, the effect of rooftop PV systems on the building roof and indoor energy balance as well as their economic impacts on building HVAC costs have been investigated, and the authors report extensive measurements of a building containing a flush mount and a tilted solar PV array.
Abstract: Building Heating, Ventilation and Air Conditioning (HVAC) is a major contributor to urban energy use. In single story buildings with large surface area such as warehouses most of the heat enters through the roof. A rooftop modification that has not been examined experimentally is solar photovoltaic (PV) arrays. In California alone, several GW in residential and commercial rooftop PV are approved or in the planning stages. With the PV solar conversion efficiency ranging from 5-20% and a typical installed PV solar reflectance of 16-27%, 53-79% of the solar energy heats the panel. Most of this heat is then either transferred to the atmosphere or the building underneath. Consequently solar PV has indirect effects on roof heat transfer. The effect of rooftop PV systems on the building roof and indoor energy balance as well as their economic impacts on building HVAC costs have not been investigated. Roof calculator models currently do not account for rooftop modifications such as PV arrays. In this study, we report extensive measurements of a building containing a flush mount and a tilted solar PV array as well as exposed reference roof. Exterior air and surface temperature, wind speed, and solar radiation were measured and thermal infrared (TIR) images of the interior ceiling were taken. We found that in daytime the ceiling surface temperature under the PV arrays was significantly cooler than under the exposed roof. The maximum difference of 2.5 C was observed at around 1800h, close to typical time of peak energy demand. Conversely at night, the ceiling temperature under the PV arrays was warmer, especially for the array mounted flat onto the roof. A one dimensional conductive heat flux model was used to calculate the temperature profile through the roof. The heat flux into the bottom layer was used as an estimate of the heat flux into the building. The mean daytime heat flux (1200-2000 PST) under the exposed roof in the model was 14.0 Watts per square meter larger than under the tilted PV array. The maximum downward heat flux was 18.7 Watts per square meters for the exposed roof and 7.0 Watts per square meters under the tilted PV array, a 63% reduction due to the PV array. This study is unique as the impact of tilted and flush PV arrays could be compared against a typical exposed roof at the same roof for a commercial uninhabited building with exposed ceiling and consisting only of the building envelope. Our results indicate a more comfortable indoor environment in PV covered buildings without HVAC both in hotter and cooler seasons.

23 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article , a novel BIPV climatic design framework for PV buildings positioning and adaptation to local climate towards the minimization of energy expenditure and use of resources is proposed.
Abstract: Despite the technical maturity and substantial potential cost reduction of BIPV technologies, there are still challenges to overcome for the expansion of BIPV applications and their wider adaptation at global level. Among these, the alignment of PV integration with particular climate and environmental conditions of the local solar architecture is crucial. This will facilitate the transition to sustainable buildings and the mitigation of climate change. In this context, this study proposes for the first time, a novel BIPV climatic design framework for PV buildings positioning and adaptation to local climate towards the minimization of energy expenditure and use of resources. With the review and analysis of a large numbers of BIPV studies globally for seventy parameters grouped in eight main categories of an open-access database, the global horizontal irradiation (GHI) value is selected as an additional index to the Köppen-Geiger classification scheme. The extension accounts for the urban suitability and vulnerability and prioritize the building integration of photovoltaics. Four zones of cold (low GHI), moderate (medium GHI), warm (high GHI) and hot (very high GHI) climatic regions are considered and applied for 127 cities globally. In this framework, the sequence of PV building component integration is proposed according to local climate of each zone and the energy performance of buildings is maximized towards their positive energy contributions and sharing in local, district and city grids. Barriers and limitations of the BIPV implementation at a larger scale are discussed and the emerging research needs are revealed.

12 citations

Journal ArticleDOI
TL;DR: In this paper , the authors demonstrated experimentally that the requirements imposed by a greenhouse can be provided by a DSSC using an affordable commercial yellow dye, which achieved a high absorption of UV radiation, closely by 90%, a transparency of the DSSCs preserved on the whole PAR domain and achieved a photovoltaic efficiency two times higher than the best efficiency reported for this dye so far.
Abstract: In trying to solve simultaneously the energy and food crisis, the concept proposed by Agriculture 4.0, namely a combination between the agriculture and the solar energy could provide a possible solution. The wavelength‐selective greenhouse could be a promising agrivoltaic system if the trade‐off between photovoltaic roofs and plants will be achieved. Using less studied solar cells as an electricity source for an autonomous greenhouse, this study has demonstrated experimentally that the requirements imposed by a greenhouse can be provided by a DSSC using an affordable commercial yellow dye. The successful implementation of DSSC in autonomous greenhouses is conditioned by three main requirements, and that are the transparency of the entire Photosynthetic Active Radiation (PAR) domain along with high UV absorption, high efficiency of the solar cell, and sustainability during the whole year. The best DSSC has proved a high absorption of UV radiation, closely by 90%, a transparency of the DSSCs preserved on the whole PAR domain and achieved a photovoltaic efficiency two times higher than the best efficiency reported for this dye so far. Furthermore, by preserving the maximum efficiency of almost 5% under the light intensity in the range 50 to 100 mW/cm2, the sustainability of our DSSC over the whole year has been demonstrated.

10 citations

Journal ArticleDOI
13 Jan 2022-Crystals
TL;DR: In this paper , the photoactive electrode based on TiO2 with a complex architecture for UV dyes along with water-based electrolyte has successfully allowed the dye-sensitized solar cell with 1.45 times higher than the best efficiency reported for synthetic dye and 3 times for curcumin dye so far.
Abstract: The optimization of the photoactive electrode based on TiO2 with a complex architecture for UV dyes along with water-based electrolyte has successfully allowed us (i) to obtain a photovoltaic efficiency of the dye-sensitized solar cell with 1.45 times higher than the best efficiency reported for synthetic dye and 3 times for curcumin dye so far; (ii) transparency on the entire Photosynthetic Active Radiation domain; (iii) preserving high efficiency for lighting 1 sun (summer) and shading, especially for 60 mW/cm2, which represents the maximum illumination in the rest of the seasons. Our water-based dye-sensitized solar cells loaded with synthetic and natural UV dyes have revealed that the implementation of a dye-sensitized solar cell in autonomous greenhouses is a viable and inexpensive concept.

7 citations

Journal ArticleDOI
TL;DR: In this article , the authors studied the indirect benefits of rooftop PV panels by conducting experiments in Raipur, India, and compared the results with the exposed roof, and presented a mathematical model to analyze the annual effect of PV shading in terms of thermal load saving and power generation.

6 citations

Journal ArticleDOI
TL;DR: In this article , a 3D computational fluid dynamic model is presented to evaluate the temperature distribution and energy performances of a vertical bifacial photovoltaic module for agrivoltaic applications.
Abstract: This study presents a 3D computational fluid dynamic model to evaluate the temperature distribution and energy performances of a vertical bifacial photovoltaic module for agrivoltaic applications. This last is compared to a conventionally tilted bifacial photovoltaic module for ground-mounted applications. The simulations are performed in SolidWorks Flow Simulation® and validated with measured data gathered from the first experimental agrivoltaic system in Sweden. Additionally, four more simulations scenarios were defined to compare the performances of vertically mounted and conventionally tilted bifacial photovoltaic modules under different operating conditions The validation of the computational fluid dynamic model shows that the model tends to underestimate the readings performed with the thermal camera in the order of 3°C to 4°C for the vertical bifacial PV module. The comparison of the results obtained from the computational fluid dynamic model with existing models available in literature shows a good agreement. The comparison of the heat distribution from the computational fluid dynamic model and the thermal images also shows a good agreement. In all the scenarios investigated, the vertical bifacial photovoltaic module's overall efficiency was higher than that of the ground-mounted module due to lower average operating temperatures. The use of the computational fluid dynamic approach for studying the performance of a single photovoltaic module showed promising results that can be extended to study the system performance and microclimatic conditions.

5 citations