• Energy Research

Abstract The current article evaluates a method of cooling low concentration photovoltaic (CPV) through the solid-liquid phase change material (PCM) to mitigate temperature-based power losses and utilize the recovered heat. The heat stored in the melted PCM is exchanged with domestic supply water, thus developing a novel CPV-PCM thermal (CPV-PCM/T) system. The CPV-PCM/T system is evaluated outdoors in the extreme hot weather conditions of Al Ain, United Arab Emirates (UAE) for the three consecutive days. The energy performance of CPV-PCM/T system is compared to the ordinary flat plate collector (FPC) and the experiments run simultaneously at the same site. Although the CPV-PCM/T produces lesser net energy (1527 kWh/m2-day) compared to FPC (1803 kWh/m2-day) yet the cost of production is 28% lower than the FPC.

Abstract Photovoltaics (PVs) are promising sustainable energy generators, yet the higher initial cost of PV systems compared to the conventional fossil fuel based energy systems remains a barrier to their large-scale adaptability. Concentrating solar radiation onto a smaller area by replacing expensive cell materials with cheaper optical materials can be an alternative way to reduce PV cost, but concentrated photovoltaics (CPV) yield substantially higher cell temperatures reportedly detrimental for CPV life and electrical yield. Various thermal management approaches have been adopted to mitigate the adverse effect of temperature on CPV life and performance. The potential use of thermal energy discarded in CPV thermal management systems has been traditionally overlooked. The aim of this article is to briefly review the progress in PV cells, different CPV systems, and thermal issues specific to concentration techniques and propose potential uses of thermal energy recovered from the CPV. The review finds that temperature mitigation and thermal energy recovery & utilization can be a promising pathway to improve CPV performance.

The United Arab Emirates (UAE) experiences up to 50% power losses in photovoltaic (PV) panels caused by frequent dust accumulation over the panels trailed by extreme temperature. Compositional and morphological insights into dust particle can potentially help design PV cleaning mechanisms inclusive of self-cleaning explored in the current article. Five different locations were studied to discover potential differences in dust samples. The collected samples were characterised employing Optical Microscopy, Scanning Electron Microscopy (SEM), X-ray Powder Diffraction (XRD), and Elemental Composition Analysis (Energy Dispersive Spectrometry, EDS). The micrographs revealed that the majority of particles were irregularly shaped, providing interlocking for the dust to stay over the surface. The particle size ranged from 0.01 to 300 µm, and some of the collected dust exhibited cavities. XRD analyses revealed variations in the chemical composition among the samples studied. Elemental Composition Analysis via EDS revealed both consistent patterns and variations in element presence among the dust samples, highlighting specific detections of chlorine (Cl) at some sites.

A concentrated photovoltaic system is evaluated as a thermal energy source employing phase change material to meet the domestic water heating demand. A paraffin wax-based phase change material is selected with a 58 °C melting point to store enough thermal energy to match the hot water demand in the buildings. The energy performance of the concentrated photovoltaics containing phase change materials is compared to that of the reference to determine the increased energy outputs due to the heat removal by the material. The concentrated photovoltaics-phase change material achieved 30% higher energy output compared to the reference concentrated photovoltaic, thus providing a strong justification for the improved thermal management design. An enthalpy-based thermal model is developed to compare the experimental results with model predictions, confirming a reasonable agreement between the results. The model is used determine the optimum melting point and container size for different phase change materials under different radiation concentrations for the hot climate of the United Arab Emirates.

The elevated temperature and dust accumulation over the photovoltaic (PV) surface are the main causes of power loss in hot and desert climates. Traditionally, PV cleaning and cooling are addressed separately, and accordingly, solutions have been developed that require extensive energy and/or manpower to cool and clean the PV panels. However, these solutions are less effective due to a lack of synergy in the devised solution, affecting both energy use and the economics of the system. A highly synergic method to cool and clean PV panels in a singular embodiment is developed, involving flowing air conditioning condensate water over the PV front surface. The current article assesses the performance of the proposed system to cool and clean the panels efficiently. The experimental results showed an up to 14% increase in the power output of the PV panels through the proposed condensate water-based cooling and cleaning method.

Dust accumulation on the photovoltaic (PV) surface decreases the solar radiation penetration to the PV cells and, eventually, the power production from the PV system. To prevent dust-based power losses, PV systems require frequent cleaning, the frequency of which depends on the geographical location, PV integration scheme, and scale of the PV power plant. This study aims to measure the drop-in radiation intensity, as well as power output, due to dust and to determine the optimal time interval for PV cleaning in the United Arab Emirates (UAE) climate. In this research, a dusting study experiment was carried out at the Renewable Energy Laboratory, Falaj Hazza Campus, UAE University, Al Ain, UAE, for 3.5 months, from 22 April 2018 to 7 August 2018. To measure the pure radiation losses caused by the dust, four transparent glasses were used to mimic the top glass cover of the PV modules. The dusting induced power losses were measured for four selected PV cleaning frequencies (10 days, 20 days, 1 month, and 3 months). This study revealed that up to 13% of power losses occurred in PV panels that remained dusty for 3 months, compared to panels that were cleaned daily. PV cleaning after 15 days brought the losses down to 4%, which was found the most feasible time for PV cleaning in this study, considering a reasonable balance between the cleaning cost and energy wasted due to soiling.

Photovoltaic (PV) panels convert a certain amount of incident solar radiation into electricity, while the rest is converted to heat, leading to a temperature rise in the PV. This elevated temperature deteriorates the power output and induces structural degradation, resulting in reduced PV lifespan. One potential solution entails PV thermal management employing active and passive means. The traditional passive means are found to be largely ineffective, while active means are considered to be energy intensive. A passive thermal management system using phase change materials (PCMs) can effectively limit PV temperature rises. The PCM-based approach however is cost inefficient unless the stored thermal energy is recovered effectively. The current article investigates a way to utilize the thermal energy stored in the PCM behind the PV for domestic water heating applications. The system is evaluated in the winter conditions of UAE to deliver heat during water heating demand periods. The proposed system achieved a ~1.3% increase in PV electrical conversion efficiency, along with the recovery of ~41% of the thermal energy compared to the incident solar radiation.