A method for evaluating both shading and power generation effects of rooftop solar PV panels for different climate zones of China
TL;DR: In this article, three types of PV rooftops, namely, horizontally-mounted overhead PV rooftop, tilted overhead PV roof, and attached PV rooftop are studied to explore their impacts on the heat gain and heat loss of the roof and building's heating and cooling load.
About: This article is published in Solar Energy.The article was published on 2020-07-15 and is currently open access. It has received 33 citations till now. The article focuses on the topics: Photovoltaic system & Solar gain.
Summary (2 min read)
Jump to: [1. Introduction] – [3. Experimental results and model validation] – [4. Analysis and discussions of overall energy-saving performance] and [5. Conclusions]
1. Introduction
- Due to the conventional energy shortage and environmental deterioration, the development and utilization of renewable energy have become inevitable in order to overcome the current energy crisis.
- Since PV panels are most commonly installed on building rooftop (Oliver and Jackson, 2001), numerous studies on the energy-saving performance of PV rooftop have been conducted.
- By substituting the comprehensive air temperature into the Eqs. (14) and (15), the indoor heat gain (heat loss) and heating load of the roof can be obtained, respectively.
- In order to illustrate the influence factors to the overall energy-saving efficiency, the test data were analyzed using SPSS 26.0.
3. Experimental results and model validation
- Therefore, the surface temperature at night of the PV rooftop was generally higher than that of the ordinary roof, and the effect of horizontal overhead PV roof is more obvious.
- This was mainly because the upper surface of the control body of the attached PV module received all solar radiation, just like the ordinary roof.
- 3. Heating and cooling load results 8. Compared with the ordinary roof, the heat gain caused by the short-wave solar radiation of the PV roofs was sheltered, and the heat loss caused by the PV roof’s long-wave radiation was reduced.
4. Analysis and discussions of overall energy-saving performance
- The overall energy-saving efficiency of a PV roof is affected by both outdoor air temperature and solar energy resources.
- In areas with hot summer and cold winter, the daily total heat loss and the peak heating load of the firmly-attached PV roof are higher than those of the ordinary roof.
- The overall energy-saving efficiencies of the selected cities in the winter are shown in Fig. 16.
- Also, the heat insulation of the PV modules was stronger than the shading effect.
- On the other hand, in the winter, the solar radiation on the inclined surface is higher than that on the horizontal surface, compared to the horizontally-mounted overhead PV roof, the tilted overhead PV roof obtained heat more.
5. Conclusions
- In addition, 13 typical cities in 5 climatic regions of China are selected for the investigations to evaluate the overall energy-saving performance of three PV roof types.
- The roof with a horizontal PV had the highest efficiency of 0.32.
- Among the selected regions, in the cold and severely cold regions with a large temperature diurnal range and low average temperature, the energy-saving efficiency was relatively high.
- For the tilted PV roof, this paper took 30° as the inclined angle, but the specific installation and the actual energy-saving effect should be determined after detailed analysis according to the local latitude and other conditions.
- The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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TL;DR: In this article , the authors proposed a technique to prevent the reverse breakdown and mitigate the hot spot temperature of the PV cells under partial shading by reducing reverse current through automated reconfiguration of PV array.
20 citations
TL;DR: In this article , the authors explore different PhotoVoltaic (PV) array reconfiguration (PVR) methods, used to reduce the negative impacts of Partial Shading Conditions (PSCs), that could affect the performance of a PV system (i.e. hotspots, electrical mismatch, etc.).
Abstract: This paper aims at exploring different PhotoVoltaic (PV) array Reconfiguration (PVR) methods, used to reduce the negative impacts of Partial Shading Conditions (PSCs), that could affect the performance of a PV system (i.e. hotspots, electrical mismatch, etc.). The classification of different PVR techniques is formed under three main categories: physical, electrical, and physical-electrical combination. Physical PVR alters the actual locations of the panels within the array. Referred to as static reconfiguration methods, this set includes puzzle based, number based, symmetry based, distance maximizing based, and nature inspired methods. On the other hand, electrical PVR reorders the electrical interconnections between PV panels, and is composed of algorithm based, artificial intelligence based, hybrid, and basic/improved electrical configurations. A combined PVR method hybridizes the two precedent categories. Each method from the three main sets, is critically compared to the relevant others, according to a mathematical model, which includes many performance indices: Fill Factor (FF), Mismatch Power Loss (PML), Percentage Power Loss (%PLoss), Performance Ratio (PR), Execution Ratio (ER), Efficiency (η), Percentage of Power Enhancement (%PE) and DC output power (PDC). The thorough investigation of different PVR techniques, resulted that a Total Cross Tied (TCT) configured PV panels, physically relocated by means of Static Shade Dispersion Physical Array Relocation (SD-PAR) algorithm, while interfered with a switching matrix controlled by Modified Harris Hawks Optimizer (MHHO) algorithm, could be an optimum and effective solution to passively mitigate PSCs’ effects.
20 citations
TL;DR: In this paper, the authors performed an in-depth performance comparison of ground-mounted and rooftop photovoltaic (PV) systems, with the aim being to minimize the levelized cost of energy (LCoE) and maximize the energy yield.
Abstract: The aim of this research is to perform an in-depth performance comparison of ground-mounted and rooftop photovoltaic (PV) systems. The PV modules are tilted to receive maximum solar irradiance. The efficiency of the PV system decreases due to the mutual shading impact of parallel tilted PV modules. The mutual shading decreases with the increasing interrow distance of parallel PV modules, but a distance that is too large causes an increase in land cost in the case of ground-mounted configuration and a decrease in roof surface shading in the case of rooftop configuration, because larger sections of roof are exposed to sun radiation. Therefore, an optimized interrow distance for the two PV configurations is determined with the aim being to minimize the levelized cost of energy (LCoE) and maximize the energy yield. The model of the building is simulated in EnergyPlus software to determine the cooling load requirement and roof surface temperatures under different shading scenarios. The layout of the rooftop PV system is designed in Helioscope software. A detailed comparison of the two systems is carried out based on energy output, performance ratio, capacity utilization factor (CUF), energy yield, and LCoE. Compared to ground-mounted configuration, the rooftop PV configuration results in a 2.9% increase in CUF, and up to a 23.7% decrease in LCoE. The results of this research show that installing a PV system on a roof has many distinct advantages over ground-mounted PV systems such as the shading of the roof, which leads to the curtailment of the cooling energy requirements of the buildings in hot regions and land cost savings, especially for urban environments.
19 citations
TL;DR: In this paper, the energy performance of an integrated adaptive envelope system (AES) is evaluated when applied to detached houses in four US climates, and three main technologies are part of the AES including cool roofs, movable PV integrated shading devices (MPVISDs), and switchable insulation systems (SISs).
19 citations
TL;DR: In this paper, the feedback mechanisms between photovoltaic energy production and the urban environment are reviewed, with an emphasis on synthesizing what is known, while drawing attention to limitations, and indeed errors in, the literature on this topic.
17 citations
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TL;DR: In this article, the authors present an active and passive building heating system for solar thermal power systems, where the active system is designed by f--chart and the passive one by Utilizability Methods.
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TL;DR: In this article, the impact of dust on PV system performance and identifying challenges to further pertinent research are discussed. And a framework to understand the various factors that govern the settling/assimilation of dust and likely mitigation measures have been discussed in this paper.
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