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• Design, optimization of a solar assisted thermal air conditioning system using CO 2. • Optimization examines collector area, inclination and storage tank capacity. • EGTC C2 emerg as the optimal configuration, achieving a seasonal f of 0.649. Traditional air conditioning and refrigeration solutions rely on compressor-driven systems, leading to increased electricity consumption and intensified greenhouse gas (GHG) emissions. These systems primarily utilize synthetic refrigerants such as CFCs, HCFCs, and HFCs. Despite their advantages, these refrigerants are either banned or subject to restricted permissions under the Montreal Protocol (1987) and the Kyoto Protocol (1997) due to environmental concerns. According to the Paris Accord, ratified by 196 parties as of 2017, there is a global shift towards low global warming refrigerants and eco-friendly alternatives. COP27 reaffirmed global commitments to limit temperature rise to 1.5 °C, emphasizing urgent action and stronger climate plans to combat global warming. CO 2 envisaged by ASHRAE is resurrected as a promising natural refrigerant with the advent of high-pressure technologies the design employs a solar evacuated glass tube collector (EGTC) with U-shaped copper tubes and flat plate collector (FPC) to harness solar thermal energy. An immersed heat exchanger's (HX) based thermal storage tank is incorporated to address the intermittency of solar energy. The CO 2 refrigerant offers advantages over other natural refrigerants due to its low critical point. This research conducts a TRNSYS® simulation of a 35.2 kW absorption cooling system with synthetic building load driven by energy captured through FPC and EGTC using R-744, additionally supported by a supplementary boiler for traditional office timing. The system design comprises two solar collectors, the EGTC and FPC, integrated with two different cooling loop configurations (C1 and C2). In C1, the hot water that exits the generator of the absorption chiller is forwarded toward the immersed HX-based hot storage tank, which is connected to the solar and absorption cooling loop. In C2, the working fluid leaving the absorption chiller is diverted directly toward the auxiliary boiler/furnace, if the temperature in the storage tank falls below the necessary level (108.89 °C) and if the tank temperature is greater than this set point temperature, then the flow passes through the storage tank. Both system designs have been developed using TRNSYS, with dynamic simulations conducted throughout the summer. The solar fraction and collector efficiency are considered as key performance indicators to evaluate and compare the system's effectiveness. Then the optimization of system parameters is performed for all four cases (EGTC C1 & C2 and FPC C1 & C2) based on these key performance indicators, all configurations integrated with a fixed synthetic building cooling load. The optimum parameters are found for all four cases, and the optimum parameters for EGTC C1 & C2 are 100 m2, 4 m3, and 11° for collector area, storage tank volume, and collector slope respectively. Similarly, for FPC based configurations, these parameters are 200 m2, 32 m3 for C2 and 4 m3 for C1, and 20° respectively. The results revealed better C2 performance than C1, with EGTC outperforming FPC. The final results were computed for the EGTC based designs due to their high solar fractions, with EGTC C2 emerging as the optimal configuration, achieving a seasonal solar fraction of 0.649. [ABSTRACT FROM AUTHOR]

Summary: Static Synchronous Compensator (STATCOM) is a shunt‐connected Flexible AC Transmission System (FACTS) controller with the primary goal of power flow control on a transmission line. However, it can effectively be used for improving power system stability by incorporating a Supplementary Damping Control (SDC) for bus voltage regulation. This paper presents an SDC strategy based on the integration of Type‐2 fuzzy logic and Wavelet Neural Network (WNN) in NeuroFuzzy structure. The fuzziness in Type‐2 membership function increases the controller capability to handle uncertainties. The performance improvement has been investigated by introducing uncertainty in mean initially and then in both the mean and SD of the Gaussian Type‐2 membership function. A multi‐machine power system installed with SDC‐based STATCOM is used to test the controller performance using different fault scenarios. The comparative evaluation of proposed controllers is done with Adaptive NeuroFuzzy TSK Control (ANFTSKC) and without SDC scenarios. In results, significant performance improvement has been observed in both steady‐state and transient regions for recommended Type‐2 NeuroFuzzy Wavelet Control (NFWC) strategies. [ABSTRACT FROM AUTHOR]

Summary: In the modern world, only conventional energy resources cannot fulfil the growing energy demand. Electricity is a fundamental building block of a technological revolution. Today, most of the electricity demand is met by the burning of fossil fuels but at the cost of adverse environmental impact. In order to bridge the gap between electricity demand and supply, nonconventional and eco‐friendly means of energy generation are considered. Renewable energy systems (RESs) offer an adequate solution to mitigate the challenges originated due to greenhouse gasses (GHG). However, they have an unpredictable power generation with specific site requirements. Grid integration of RESs may lead to new challenges related to power quality, reliability, power system stability, harmonics, subsynchronous oscillations (SSOs), power quality, and reactive power compensation. The integration with energy storage systems (ESSs) can reduce these complexities that arise due to the intermittent nature of RESs. In this paper, a comprehensive review of renewable energy sources has been presented. Application of ESSs in RESs and their development phase has been discussed. Role of ESSs in increasing lifetime, efficiency, and energy density of power system having RESs has been reviewed. Moreover, different techniques to solve the critical issues like low efficiency, harmonics, and inertia reduction in photovoltaic (PV) systems have been presented. Unlike most of the available review papers, this article also investigates the impact of FACTS technology in RESs‐based power system using multitype flexible AC transmission system (FACTS) controllers. Three simulation models have been developed in MATLAB/Simulink. The results show that FACTS devices help to maintain the stability of RESs integrated power system. This review paper is believed to be of potential benefit for researchers from both the industry and academia to develop better understanding of challenges and solution techniques for REs‐based power systems and future research dimensions in this area. [ABSTRACT FROM AUTHOR]

Summary: Refrigerants bearing high global warming potential (GWP) and ozone depletion potential (ODP) were outlawed or facing time‐beared permission under the Montreal (1987), Kyoto (1997) protocols, F‐Gas law (2015), Paris Accord (2016), and recent Kigali Amendment to Montreal Protocol (2019). In order to modify followed by the paradigm shift of existing heating and cooling systems, American Society of Heating, Refrigeration, and Air‐Conditioning Engineers (ASHRAE) envisaged natural and synthetic refrigerants (Synrefs) are under investigation globally. Carbon dioxide (CO2) is a popular natural refrigerant (Natref) replacing Synrefs used in commercial heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems globally. A rampant rise is observed in markets of Asia (Japan and China), North America (the United States and Canada), the Australian continent, and Africa (South Africa) by reaching 20 000 CO2‐stores around the globe. The European markets are leading the utilization of CO2 in the heat pump, and refrigeration, CO2 based markets estimate 14% of the total food retail stores (400 m2). Japan is the second leading market of CO2 heat pump and refrigeration with more than 10 200 CO2 condensing units. CO2 transcritical systems have a share of more than 10% in only European market (large stores); however, their share is less than 10% of total stores in other major markets of the world. New pump and compressor‐driven transcritical CO2 systems integrate ejectors, condensers, and booster systems to reduce energy consumptions, enhance efficiency, efficacy, and coefficient of performance. This article reports a critical review of the CO2 based heating, cooling, and refrigeration system and presents updated literature along with barriers and challenges on commercial use of Natref‐based heating and cooling applications worldwide. [ABSTRACT FROM AUTHOR]

Energy storage and transportation are essential keys to make sure the continuity of energy to the customer. Electric power generation is changing dramatically across the world due to the environmental effects of Greenhouse gases (GHG) produced by fossil fuels. The unpredictable daily and seasonal variations in demand for electrical energy can be tackled by introducing the energy storage systems (ESSs) and hence mitigating the extra GHG emission in the atmosphere. Energy storage techniques can be mechanical, electro‐chemical, chemical, or thermal, and so on. The most popular form of energy storage is hydraulic power plants by using pumped storage and in the form of stored fuel for thermal power plants. The classification of ESSs, their current status, flaws and present trends, are presented in this article. The present state of fossil fuel reserves, their production, consumption, and as a consequence of these the CO2 emissions are also discussed. The primary energy carriers coal, oil and gas are not evenly distributed along the globe. Long distances are involved in transporting these energy carriers and transportation and delivery of these key resources to the prime customers is always necessary. The different methods to transport the energy from the source end to demand end is also discussed in this article. The assessment of various energy storage methods on the basis of several factors and present status and development of storage and transportation of energy in Pakistan is discussed. [ABSTRACT FROM AUTHOR]

The world's challenge is to determine a more efficient, economical and environmental-friendly energy source to compete and replace the ongoing conventional energy resources. Solid oxide fuel cells (SOFCs) provide a highly efficient system to use divergent energy resources and have proved to provide the cleanest energy, least energy use, and lowest emissions. A techno-economic study is required to investigate the model design for SOFC-based micro-combined heat and power (m-CHP) systems for applications in terms of educational and commercial buildings. This work models and explores the optimized application of hydrogen gas-fueled SOFC-based m-CHP systems in educational buildings. Two educational departments' loads are presented and model of SOFC-based m-CHP system against the different electric power demands is performed, in order to provide a techno-economic assessment of the technology. For successful development of the technology, results are related to system rightsizing, operating strategies, thermal to electric ratios, and match between end-use, with an aim towards classifying the overall feasibility and essential application requirements. [ABSTRACT FROM AUTHOR]

Abstract The structural and electrochemical properties of zinc based nano-composites anode materials with a composition of X 0.25 Ti 0.05 Zn 0.70 (where X = Cu, Mn, Ag) have been investigated in this present study. The proposed X 0.25 Ti 0.05 Zn 0.70 oxide materials have been synthesized through sol-gel method. The doping effect of Cu, Mn, and Ag on TiZn oxides were analyzed in terms of electronic conduction and power density in hydrogen atmosphere at comparatively low temperature in the range of 650 °C. The crystal structure and surface morphology were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis techniques. The XRD patterns of composites depict that the average crystalline sizes lie in the range of 20–100 nm. Four-probe DC conductivity technique was used to measure the conductivity of the materials and maximum electrical conductivity of Ag 0.25 Ti 0.05 Zn 0.70 oxide was found to be 7.81 S/cm at 650 °C. The band gap and absorption spectra were determined by ultra-violet visible (UV–Vis) and Fourier Transform Infrared spectroscopy (FTIR) techniques respectively. The maximum power density was achieved to be 354 mW/cm2 at 650 °C by Ag 0.25 Ti 0.05 Zn 0.70 oxide anode with SDC (electrolyte) and BSCF (conventional cathode) materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Water heating without greenhouse gas emissions is indispensable for sustainable development in low sun regions. The integration of solar energy in domestic water and space heating systems is a sustainable pathway. Kyoto and Montreal protocols have already banned the use of chlorofluorocarbons and hydrofluorocarbons and granted a time limited permission to hydrochlorofluorocarbons. Synthetic refrigerants outperform natural refrigerants, yet 196 countries agreed on phasing out these refrigerants under Paris Accord in 2015. Industries, researchers and policy makers are retrofitting existing heating and cooling systems to integrate natural refrigerants worldwide. In this regard, an evacuated glass tube solar water heating system is simulated in Transient Systems Simulation Program (TRNSYS®) using low global warming potential (GWP) refrigerants. Parametric analysis is carried out to determine optimal sizes and configurations of solar collectors, heat exchangers, tank volumes and heights for annual performance assessment of solar water heaters. The optimized model was dynamically simulated under diverse weather conditions of Pakistan (Karachi), Australia (Melbourne) and China (Beijing). Our results show an optimal selection of solar water heating system parameters using 6 m2 collector area, 0.42 m3 tank volume, and 1.2 m tank height fulfil single family dwelling heating demands. Moreover, use of low global warming potential hydrofluoroolefins (HFOs) R-1234yz and R-1234yf refrigerants shows even superior thermal performance. The highest annual solar fraction values were recorded for CO 2 (0.720289) and R-410a (0.723428) under various weather conditions. Our findings show that use of synthetic refrigerants slightly improves the performance of system, however, giving weightage to environmental benefits the natural refrigerants take precedence over synthetic refrigerants. This research work recommends an adoption of natural refrigerants as an environmentally superior and sustainable option. [ABSTRACT FROM AUTHOR]