• Energy Research

This research investigates the use of phase change materials (PCMs) in thermal energy storage (TES) unit-based cooling systems to increase the efficiency of air conditioners (ACs) by reducing the air inlet temperature. This study aims to evaluate different configurations of PCM enclosures, and different PCMs (paraffin and salt hydrate), by changing the speed of inlet air to achieve heat reduction of inlet air. The study includes experimental and simulation investigations. Every configuration simulates the hot-season atmospheric conditions of the UAE. A duct containing enclosures of paraffin RT-31 and salt hydrate (calcium chloride hexahydrate) was used for the simulation study using ANSYS/Fluent. A conjugate heat transfer model employing an enthalpy-based formulation is developed to predict the optimized PCM number of series and optimum airflow rate. Four designs of the AC duct were modelled and evaluated that contained one to four series of PCM containers subjected to different levels of supplied air velocities ranging from 1 m/s–4 m/s. The simulation study revealed that employing four series (Design 4) of PCM enclosures at a low air velocity of 1 m/s enhanced the pre-cooling performance and reduced the outlet air temperature to 33 °C, yielding a temperature drop up to 13 °C. The performance of salt hydrate (calcium chloride hexahydrate) was observed to be better than paraffin (RT-31) in terms of the cooling effect. Characterization of paraffin wax (RT-31) and salt hydrate was performed to establish the thermophysical properties. The experimental setup based on a duct with integrated PCM enclosures was studied. The experiment was repeated for three days as the repeatability test incorporating RT-31 as the PCM and a 3 °C maximum temperature drop was observed. The drop in the outlet air temperature of the duct system quantifies the cooling effect. Net heat reduction was around 16%.

The share of photovoltaic (PV) power generation in the energy mix is increasing at a rapid pace with dramatically increasing capacity addition through utility-scale PV power plants globally. As PV plants are forecasted to be a major energy generator in the future, their reliable operation remains of primary concern due to a possibility of faults in a tremendously huge number of PV panels involved in power generation in larger plants. The precise detection of nature and the location of the faults along with a prompt remedial mechanism is deemed crucial for smoother power plant operation. The existing fault diagnostic methodologies based on thermal imaging of the panels as well as electrical parameters through inverter possess certain limitations. The current article deals with a novel fault diagnostic technique based on PV panel electrical parameters and junction temperatures that can precisely locate and categorize the faults. The proposed scheme has been tested on a 1.6 kW photovoltaic system for short circuit, open circuit, grounding, and partial shading faults. The proposed method showed improved accuracy compared to thermal imaging on panel scale fault detection, offering a possibility to adapt to the PV plant scale.

Building applied solar thermal systems are considered by different stakeholders an attractive alternative to traditional space and water heating systems. However, their performance depends largely on climatic conditions, water heating needs and operational parameters which, in turn, offer opportunities for performance optimization. The present research attempts to provide architects with a design decision tool that integrates solar thermal collectors efficiently to meet hot water demand for various building types inclusive of residential, commercial and industrial in a hot climate. The analysis is conducted numerically through a thermal model developed and executed in TRNSYS and validated experimentally. The parameters investigated include the collector tilt angle, azimuth angle and collector inlet fluid flow rate. Finally, the collector aperture area required per building foot print area is determined. The research revealed that for a 1000 m2 footprint building area of schools, offices, residential, factories and hospitals would require respectively 8 m2, 10 m2, 14 m2, 24 m2 and 38 m2 of the static collector installed at 24° tilt angle with optimal water flow rate. Additional operational aspects of collector tracking, and solar radiation concentration were investigated and further reduce the required collector area. A simple payback period analysis reveals a return on investment of 2 years applying subsidized tariff rates under the climatic conditions of, or similar to Dubai, in the United Arab Emirates.

This paper evaluates the effect of dynamic thermal conductivity (λ) change of expanded polystyrene insulation (EPS) on temperature change through a conventional wall assembly at varying positions of the insulation within the assembly in question. According to the findings, in the case of the application of the variable λ-value of the insulation, compared to that obtained when the constant λ-value for polystyrene (EPS) insulation is adopted in the same conditions, the temperature profile through the wall assembly during the daytime is greater. In the event of applying the constant and variable λ-values, the temperature shift on the inside is seen to decline as the location of the insulation material is positioned towards the surface of the inner wall. The highest level of time lag between position 1 to 2 is over 1.3 h and around 3.47 h between position 1 and 3, and as the density level of the insulation materials rises, it leads to better transient thermal performance due to a lower temperature rise on the inside wall surface. These results suggest that considering betterment in the insulation's thermal conductivity would provide the most performant wall configuration by placing the material in the middle of the wall assembly, taking into account the change in the thermal conductivity of the insulation.

The green building rating system within the sustainability framework of the United Arab Emirates (UAE), the Pearl Rating System (PRS), similar to most international rating systems such as LEED, considers several strategies, regulations, and policies to improve the energy and water performance in buildings. However, the applicability of considering water as part of energy or the fact that the utilization of energy mandates the usage of water seems unexplored and is not yet included in any of the existing building rating systems. A unified approach of water and energy resources is thus vital for future considerations in energy policy, planning, and the inclusion of the same in the sustainability rating systems. This paper investigated, as a case study, the prospects of water–energy nexus in the prevailing UAE green building rating system—PRS—to uncover whether any water conservation strategy has an adverse effect on energy and vice versa. The review revealed that the major shortcomings of the PRS in terms of water–energy nexus strategy are the usage of reference codes that are not suitable for the UAE’s climate and geographical conditions, inexistent synergy between some credit categories, the oversight of rebound effects, and a need for credit reassessment. The paper also recommends that any proposed strategy to realign credit categories in terms of the water–energy nexus with the potential risk to also have a hidden negative rebound effect that researchers and practitioners should identify lest the water–energy tradeoff brings unprecedented repercussions. The theoretical analysis establishes that the bifurcating management of water and energy in the sustainability rating system and energy policy needs to be revisited in order to reap more sustainable and optimum results that are environmentally, ecologically, and financially consistent.

Phase change materials (PCMs) have been identified as potential candidates for building energy optimization by increasing the thermal mass of buildings. The increased thermal mass results in a drop in the cooling/heating loads, thus decreasing the energy demand in buildings. However, direct incorporation of PCMs into building elements undermines their structural performance, thereby posing a challenge for building integrity. In order to retain/improve building structural performance, as well as improving energy performance, micro-encapsulated PCMs are integrated into building materials. The integration of microencapsulation PCMs into building materials solves the PCM leakage problem and assures a good bond with building materials to achieve better structural performance. The aim of this article is to identify the optimum micro-encapsulation methods and materials for improving the energy, structural and safety performance of buildings. The article reviews the characteristics of micro-encapsulated PCMs relevant to building integration, focusing on safety rating, structural implications, and energy performance. The article uncovers the optimum combinations of the shell (encapsulant) and core (PCM) materials along with encapsulation methods by evaluating their merits and demerits.

Global interest in Building Integrated Photovoltaics (BIPV) has grown following forecasts of a compound annual growth rate of 18.7% and a total of 5.4 GW installed worldwide from 2013 to 2019. Although the BIPV technology has been in the public domain for the last three decades, its adoption has been hindered. Existing literature asserts that proper information and education at the proposal or early design stage is an important way of addressing adoption barriers. However, there is a lack of BIPV communication approaches for research, and market proposals that focus on clear information about its benefits. This has limited the adoption of BIPV.. Based on this, the present study aims to develop a conceptual framework for an educative-communication approach for presenting BIPV proposals to encourage its adoption. This is aimed at developing holistic research and market proposals which justify scholarly investigation and financial investment. Using a multiple case study investigation and Design Research Methodology (DRM) principles, the study developed an approach which combines core communication requirements, the pillars of sustainability and a hierarchical description of BIPV alongside its unique advantages. A two-step evaluation strategy involving an online pilot survey and a literature-based checklist, was used to validate the effectiveness of the developed approach. Our results show that understanding environmental and economic benefits was found to be significantly important to people who are likely adopters of BIPV (p < 0.05), making these benefits crucial drivers of adoption. Statistical significance was also found between those who do not know the benefits of using solar energy for electricity, and interest in knowing these benefits (p < 0.05). We thus conclude that proper communication of these benefits can safely be advanced as important facilitators of BIPV adoption. In general, this study elaborates the need and strategies for appropriate dissemination of innovative ideas to encourage and promote adoption of technological advancement for a sustainable global future.

The current research seeks to maintain high photovoltaic (PV) efficiency and increased operating PV life by maintaining them at a lower temperature. Solid-liquid phase change materials (PCM) are integrated into PV panels to absorb excess heat by latent heat absorption mechanism and regulate PV temperature. Electrical and thermal energy efficiency analysis of PV-PCM systems is conducted to evaluate their effectiveness in two different climates. Finally costs incurred due to inclusion of PCM into PV system and the resulting benefits are discussed in this paper. The results show that such systems are financially viable in higher temperature and higher solar radiation environment.