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Increasing energy demand in buildings in the last decade has led to more efficient usage of renewable energy. Building integrated photovoltaic/thermal systems is one of the effective ways of reducing energy consumption in buildings by providing heating, cooling, ventilation, hot water, and air. The enhancement of photovoltaic cell temperature reduces the electrical efficiency of photovoltaic panel systems. In this regard, the effects of cooling with air and phase change material layer are investigated in this study. The simulation of BIPV/T, PV, and heat pump was done in TRNSYS. As the main novelty of recent simulation, for the calculations of phase change material layer, MATLAB coupled with the TRNSYS, and Python software was used for the prediction process under the weather conditions of Sharurah, Saudi Arabia for 2022. Also, the performance of a building integrated photovoltaic/thermal system with a phase change material layer is predicted for 2024 and 2025 by the Random Forest machine learning method. The R squared, Root Mean Squared Error, and Mean Absolute Error are utilized for checking the accuracy of the model. Also, for more certainty, a validation was done on the simulated results of TRNSYS and the results showed high conformity of data. The simulated data for the first six months of 2022 showed that the maximum cooling effect happened in June with 25.47 °C and a 37.87 % reduction in photovoltaic cell temperature. Also, the best electrical efficiency improvement was 1.26 % while the thermal efficiency ranged from 29.65 % to 59.40 %, respectively. The predicted data was confirmed by R2, RMSE, and MAE equal to 96.64 %, 0.06 and 0.04. According to the simulation and predictions done, the annual electrical production of the building is achieved. The results indicate that, for the simulated system, about 29.7 %, 29.8 %, and 29.6 % of total energy utilization could be supplied by BIPV/T cooled with phase change material in 2022, 2024, and 2025, respectively. • Simulation and performance prediction done for BIPV/T system cooled with PCM layer. • Random Forest method validation with simulation results showed R2 equal to 97.91 %. • Highest cooling performance of PCM was 1.26 % in the first six months of 2022. • Total efficiency obtained for the second six months of 2022 ranged from 58 % to 61 %. • Predicted electrical efficiency for system in 2024 and 2025 were 11.20 % and 11.26 %. [ABSTRACT FROM AUTHOR]

Combined heat and power (CHP) plants are known as efficient technologies to reduce environmental emissions, balance energy costs, and increase total energy efficiency. To obtain a more efficient system, various optimization methods have been employed, based on numerical, experimental, parametric, and algorithmic optimization routes. Due to the significance of algorithmic optimization, as a systematic method for optimizing energy systems, this novel review paper is focused on the meta-heuristic optimization algorithms, implemented in CHP energy systems. By considering the applied objective functions, the main sections are divided into single-objective and multi-objective algorithms. In each case, the units' combination is briefly detailed, the objective functions are introduced, and analyses are conducted. The main aim of this paper is to gather a database for the optimization of CHPs, demonstrate the effect of the applied optimization methods on the objective functions, and finally, introduce the most efficient methods. The most significant feature of this paper is that it covers all types of CHP optimization issues including scheduling, sizing, and designing problems, finding the extent of each optimization issue in the relevant papers in the last decade. Based on the findings, in the single-objective problems the combined heat and power economic dispatch (CHPED) issue as a subcategory of the scheduling problems is introduced as the most paid topic; the designing issue is known as the lowest paid topic. In the multi-objective problems, working on various types of CHP optimization problems has been conducted with an almost similar share. The combined heat and power economic emission dispatch (CHPEED) problem with the most share, and the sizing issue with the lowest share. The CHP designing and sizing optimization issues could be introduced as topics to work on more in the future. Additionally, the numerical results of CHPED and CHPEED problems solved by various algorithms are presented and compared. In this regard, specified test systems are considered. [ABSTRACT FROM AUTHOR]

Hydrogen emerges as a pivotal energy carrier, shaping the future of the energy landscape. This study explores the potential of utilizing solar energy for green hydrogen production, presenting a promising avenue for low-carbon energy generation. Despite its potential, uncertainties stemming from the intermittent nature of solar energy, demand fluctuations, and economic considerations pose challenges to its widespread adoption. The paper delves into the performance of a power-to-hydrogen system, employing solid oxide electrolyzers to convert electricity from solar arrays into green hydrogen. Two distinct system architectures are proposed: the dedicated configuration, where the owner of the solar array and power-to-hydrogen facilities are the same, and the non-dedicated configuration, where the power-to-hydrogen system purchases solar electricity from the owner of the solar power plant. Simulation results from the case study reveal that the non-dedicated system offers superior economic performance compared to the dedicated system. Considering different hydrogen demand levels and electrolyzer sizes, the levelized cost of hydrogen in the non-dedicated scheme is below 2 $/kg, demonstrating competitive pricing within the realm of renewable technologies. However, solar-assisted green hydrogen faces tough competition with traditional sources of hydrogen production when considering economic aspects. • The effect of component size and demand level on green hydrogen production has been analyzed. • Two scenarios, dedicated and non-dedicated configurations, have been investigated. • The component size has been optimized for various demand levels in both configurations. • Simulation results indicate superior LCOH performance in the non-dedicated configuration. • Solar hydrogen production faces tough competition from conventional technologies in final pricing. [ABSTRACT FROM AUTHOR]

Summary: In this article, the performance improvement of supercritical carbon dioxide (sCO2) Brayton cycles through heat recovery and advanced heat exchanger (HX) design is reviewed. The configuration of sCO2 cycles and the bottleneck of the design of an efficient sCO2 cycle is first evaluated. It was found that heat rejected in the precooler is a large waste that could potentially enhance the overall sCO2 system performance. Then integration of the absorption cycle, organic Rankine cycle, and thermal desalination plant to the sCO2 cycle to recover the waste thermal energy is reviewed and discussed. Results showed that these bottoming heat recovery cycles could substantially improve the overall sCO2 system efficiency. The combined system of sCO2/absorption chiller, sCO2/ORC increases the cycle efficiency to about 78% and 79%, respectively. Also, a combined system of sCO2/desalination produces about 200 000 m3/day with a cost of less than $1.0/m3. Based on the review, the evaluation criteria are proposed for decision‐makers. Another bottleneck of the design of the sCO2 system is the HXs (recuperators) used in the sCO2 cycle which are relatively large and negatively affect the cycle compactness and performance. Therefore, various types of recuperators proposed and designed for sCO2 cycles are reviewed and evaluated. This review highlights the need for further research to enhance heat recovery, reduce the cost of bottoming cycles, and improve the design of HXs. [ABSTRACT FROM AUTHOR]

Summary: Solar steam power plant is the dominant technology in the category of solar thermal power systems. In steam power cycles, there is usually a couple of steam lines, extracted from medium‐pressure and low‐pressure turbines, to preheat the working fluid before the boiler. This although leads to an increase in the energy efficiency of the cycle, reduces the contribution of the turbine proportionally. Therefore, finding an alternative method of preheating the working fluid would be effective in further enhancement of the efficiency of the system. In this study, the feasibility of using solar collectors for the preheating process in a solar steam power plant is investigated. For this, parabolic trough solar collectors and evacuated tube solar collectors based on a wide range of different scenarios and configurations are employed. The plant is designed, sized and thermodynamically analyzed for a case study in Saudi Arabia where there is a large solar irradiation potential over the year. The results of the simulations show that, among all the considered scenarios, a power cycle aided by a set of parabolic trough collectors as the preheating unit is the best choice technically. This configuration leads to about 23% increased power generation rate and 6.5% efficiency enhancement compared to the conventional design of the plant. Highlights: Performance enhancement of solar steam power plant in Saudi Arabia is investigated.Replacement of feed water heating via turbine extraction by solar thermal systems is proposed.Solar parabolic trough and evacuated tube collectors are considered as potential solutions.Six different scenarios are investigated to cover all the possibilities.The best solution among all the investigated scenario is introduced. In this study solar thermal units in different arrangements and configurations come into service to provide feedwater heating in conventional solar steam power plants. This results in a stronger effectiveness of solar energy in the system and a considerable improvement of the cycle efficiency. Comparison of different designs in terms of thermal effectiveness makes it clear which type of collector in which arrangement is the best choice. [ABSTRACT FROM AUTHOR]

The main motivation of this study is to offer, develop, and optimize a novel solar combined technology to bring sustainability to the industrial sector via supplying 100 % green and cost-effective heating and cooling. The combination of a special type of parabolic trough collector designed to be inexpensive with low-concentration yet high-optical efficiency and a specially developed bio-driven boiler to compensate for the fluctuations of the solar energy is the heart of the proposed system. The article presents a thorough complex optimization and techno-economic-environmental analysis of the proposed solution and conducts a benchmarking analysis against cheap but unsustainable technologies of today's industries for a large case study in Northern Europe. The results prove the strong impacts of the technology in emission reduction and lower cost production of industrial heating and cooling. The solar component of the system fulfills nearly 50 % of the total demand, with the biomass heater, burning sugarcane bagasse, covering the additional demand. For the proposed system, a levelized cost of energy of 69.9 USD/MWh and an emission index of 267.7 tons/GWh are achieved, while the identical and alternative systems would necessitate 9,660, 11,600, and 3860 tons of coal, wood, or LPG, respectively, to fulfill the park's thermal requirements. • A combined solar-driven technology is proposed for the industrial sector's sustainability. • The technology may supply year-round green, and cost-effective heating and cooling. • Hybrid optimizations make a trade-off of technical, economic, and environmental impacts. • The system can supply heat and cold at a competitive LCOE of below 7 c$/kWh. • The solution can prevent annual emissions of up to 20 million kg of equivalent CO 2. [ABSTRACT FROM AUTHOR]

The aim of this study was to conduct thermodynamic and economic analyses of a concentrated solar power (CSP) plant to drive a supercritical CO2 recompression Brayton cycle. The objectives were to assess the system viability in a location of moderate-to-high-temperature solar availability to sCO2 power block during the day and to investigate the role of thermal energy storage with 4, 8, 12, and 16 h of storage to increase the solar share and the yearly energy generating capacity. A case study of system optimization and evaluation is presented in a city in Saudi Arabia (Riyadh). To achieve the highest energy production per unit cost, the heliostat geometry field design integrated with a sCO2 Brayton cycle with a molten-salt thermal energy storage (TES) dispatch system and the corresponding operating parameters are optimized. A solar power tower (SPT) is a type of CSP system that is of particular interest in this research because it can operate at relatively high temperatures. The present SPT-TES field comprises of heliostat field mirrors, a solar tower, a receiver, heat exchangers, and two molten-salt TES tanks. The main thermoeconomic indicators are the capacity factor and the levelized cost of electricity (LCOE). The research findings indicate that SPT-TES with a supercritical CO2 power cycle is economically viable with 12 h thermal storage using molten salt. The results also show that integrating 12 h-TES with an SPT has a high positive impact on the capacity factor of 60% at the optimum LCOE of $0.1078/kW h. [ABSTRACT FROM AUTHOR]

This paper aims to employ multi-agent-based energy management and optimization to design a set of interconnected micro-grids with the ability to exchange electricity with the main grid. Initially, the micro-grid components, their governing mathematical model, and the pricing mechanism are introduced. In the next step, the energy management framework is constructed based on three objective functions: minimizing electricity costs, maximizing renewable energy penetration, and providing maximum possible satisfaction. A multi-agent system composed of several operational agents is presented. To evaluate the applicability of the proposed approach case study was conducted. The proposed multi-agent-based optimization is employed to define the most promising solution for the energy system. The solution contains PV power installation, battery storage capacity, home appliances operational schedule, and the energy flow between micro-grids and the main grid. Simulation results indicated that the average annual earnings of the households from interacting with the main grid could be enhanced by 32.9% after performing the optimization procedure. Finally, variations in the distribution classes and investment costs were conducted to observe the effect of changing presumed parameters. Varying the investment costs revealed that for PV-specific investment costs greater than 1500 $/kW, employing solar power generation is not favorable from an economic point of view. However, it should be noted that the required PV installation capacity and hence the required investment strongly depends on the available solar energy. As a result, for regions with smaller annual irradiation, the configuration of the energy system may be quite different. To sum up, the study's overall results show that the proposed multi-agent optimization framework provides a powerful tool to design and operate energy systems composed of several energy sources and versatile users. • The configuration and operation of interconnected micro-grids is optimized. • Multi-agent framework surpasses the rule-based optimization. • Energy import from the main grid increases when more users prioritize the comfort. • When the initial cost of PV exceeds 1500 $/kW, using solar power is not efficient. • The minimum grid dependency must be satisfied subsequent to the other objectives. [ABSTRACT FROM AUTHOR]

Optimization is more and more significant due to its application in the real engineering problems. The recently proposed imperialist competitive algorithm (ICA) is a successful method in mono-objective optimization. Nevertheless, ICA cannot handle simultaneously the conflicting objectives in multi-objective design problem. In addition, the ICA has the drawback of trapping in local optimum solutions when used for high-dimensional or complex multimodal functions. In order to deal with these situations, in this work, an improved ICA, named modified multi-objective imperialist competitive algorithm (MOMICA) is proposed. In MOMICA, an attraction and repulsion (AR) concept is implemented in the assimilation phase to improve the performances of the algorithm to reach the global optimal position. Moreover, in contrast to ICA, the proposed algorithm integrates the sorting non-dominated strategy (SND) to store the Pareto optimal solutions of multiple conflicting functions. Three performance metrics are used to evaluate the performance of the proposed algorithm: (a) convergence to the true Pareto-optimal set, (b) solutions diversity and (c) robustness, characterized by the variance over 10 runs. The results presented in this paper show that the MOMICA algorithm outperforms the other popular techniques in terms of convergence characteristics and global search ability, for both benchmark functions optimization and multi-objective engineering optimization problems. • A MOMICA algorithm is proposed to improve the basic ICA. • The attraction and repulsion concept is implemented in MOMICA. • MOMICA is tested on many engineering problems and high dimensions test functions. • The results are favorable compared to other well-known methods found in literature. [ABSTRACT FROM AUTHOR]

An ultralow-temperature district heating system that uses neighborhood-scale heat pumps was recently proposed and investigated. Although the system was found more efficient than any existing solution, there is still potential in this concept for achieving better efficiency and cost-effectiveness. One of the main origins of losses here is through the enlarged pipes. In this work, triple-pipes are proposed to be used instead of twin-pipes to have individual domestic hot water and space heating pipes, reducing the size of heat pumps and decreasing thermal loss rates. The proposed concept is designed, sized and thermodynamically analyzed for a case study in Denmark. The performance is compared with the previous version of this concept as well as the low-temperature district heating system, which is another important competitor to the proposed solution. The results prove that the proposed system outperforms both of the competitors in terms of energy efficiency. For three consecutive days in typical warm/moderate/cold weather in the case study, the proposed solution results in the rates of heat loss of 4.5/10.9/16.5%, respectively. The heat loss rates, for the conventional configuration and the low-temperature design, are 4.9/13.8/19.6% and 5.6/17.8/33.1%, respectively. • Triple-pipes and shared power heat pumps are proposed for district heating systems. • The system is designed and analyzed thermodynamically for a case study in Denmark. • Performance of the system is compared to other district heating systems. • The proposed system shows better efficiency and cost-effectiveness than others. [ABSTRACT FROM AUTHOR]

District heating (DH) systems are one of the main components of future energy systems as they can significantly contribute to the transition towards a 100% renewable-based supply. Employing heat pumps in the substation of DH end-users has already been investigated, finding the periodic use of heat pumps an economic challenge. This work proposes neighborhood-scale heat pumps in an ultralow-temperature DH system to increase their utilization factor and thereby, improving the cost-effectiveness. As such, triple-pipes (TPs) are used instead of conventional twin-pipes (TwPs) to separate hot water (HW) line from space heating (SH) line, decreasing the size of heat pumps and the rate of losses. Heat pumps only increase the temperature of the HW supply line. The suggested DH system is designed and analyzed thermodynamically for a sample network, and the results are compared with a low-temperature DH system, as the most important competitor to the proposed solution. The results show that the proposed system is better than the competing solution in terms of an overall efficiency point of view. For three typical hot/medium/cold days in the network, the daily thermal losses of the proposed and low-temperature systems are 155.2/557.5/913.4 kWh and 182.3/692.8/1053.2 kWh, respectively. • Triple-pipes and decentralized heat pumps are analyzed in district heating systems. • Performance of this system is compared to low-temperature district heating system. • Proposed solution offers a lower rate of heat loss and better energy efficiency. • Effectiveness is larger when the operation load is higher, e.g. a winter day. [ABSTRACT FROM AUTHOR]

Our main objective in the present work is to elaborate the characteristics of heat transport and magneto-hydrodynamics (MHD) finite film flow of human blood with Carbon Nanotubes (CNTs) nanofluids over a stretchable upright cylinder. Two kinds of CNTs nanoparticles, namely (i) SWCNTs (single walled carbon nanotubes) and (ii) MWCNTs (multi walled carbon nanotubes), are used with human blood as a base liquid. In addition, a uniform magnetic field (B) has been conducted perpendicularly to the motion of nanoliquid. The transformation of the partial differential structure into a non-linear ordinary differential structure is made by using appropriate dimensionless quantities. The controlling approach of the Homotopy analysis method (HAM) has been executed for the result of the velocity and temperature. The thickness of the coating film has been kept variable. The pressure distribution under the variable thickness of the liquid film has been calculated. The impacts of different variables and rate of spray during coating have been graphically plotted. The coefficient of skin friction and Nusselt number have been presented numerically. In addition, it is noticed that the thermal field of a nanoliquid elevates with rising values of ϕ and this increase is more in SWCNTs nanofluid than MWCNTs nanofluid. [ABSTRACT FROM AUTHOR]

There is no doubt that the determination of a smart charging-discharging pattern can be very effective in increasing the cost-effectiveness and overall energy efficiency of an energy storage system. For finding the optimal operation strategy of the energy storage unit of a renewable power plant, the electricity spot price, the forecast data of energy availability, and the regulations of the local power market should all be taken into account. In addition to these economic considerations, the effect of deviation from the nominal load (partial-load operation) on the performance of the energy storage system is a critical parameter that directly affects the optimal operation pattern of the system in real-life energy markets. In this study, the effects of partial-load work of a low-temperature compressed air energy storage system on its overall performance are investigated thermodynamically employing real performance maps of all the components of the system. The results of the study indicate that the energy storage system needs to operate around nominal design conditions if it is expected to perform efficiently. The round-trip efficiency of the unit approaches 68% at a nominal load while it offers the low efficiencies of 52% and 28% if working at 50% and 10% loads, respectively. • A comprehensive off-design performance analysis of a LTA-CAES system is carried out. • The effects of partial load operation of the system components on the whole system are evaluated. • The LTA-CAES shows an overall energy efficiency of 68% at nominal load. • The efficiency will fall to 51% and 28% for 50% and 10% loads, respectively. • The efficiency will not be destroyed if the operational load is kept above 70% all the time. [ABSTRACT FROM AUTHOR]

In this study, techno-economic comparison of three different biodiesel production scenarios integrated with glycerol supercritical water reforming (SCWR) process to produce electricity is conducted. In the first scenario, biodiesel is synthesized from acid-pretreated waste cooking oil (WCO) in the presence of alkali catalyst. In the second scenario, biodiesel is obtained from WCO by acid catalyst. In the third scenario, biodiesel is derived from WCO using acid catalyst, followed by hexane extraction of the produced methyl esters. The glycerol evolved from all the above-mentioned pathways is then subjected to the SCWR process in order to produce hydrogen. The produced hydrogen is then combusted to provide thermal energy required by biodiesel production and purification processes as well as to generate electricity. All the developed scenarios are modeled and simulated in Aspen HYSYS software environment. In order to simplify the simulation process, canola-based WCO is considered as triolein with 6 wt% oleic acid (free fatty acid) and, accordingly, the prepared biodiesel is taken into account as methyl oleate. In order to compare the economic profitability of the developed approaches, several economic indicators including net present value (NPV), internal rate of return (IRR), payback period (PBP), discounted payback period (DPBP), and return on investment (ROI) are used. A sensitivity analysis is also carried out to show how variations in feedstock, biodiesel, and electricity prices can affect the NPV of the developed scenarios. According to the results obtained, the highest IRR and ROI values as decision-making parameters are obtained for the first scenario, manifesting its suitability from the techno-economic viewpoint. The economic indicators of the second scenario are also acceptable and very close to the first approach. Overall, upgrading glycerol into hydrogen using SCWR process appears to be an attractive strategy for enhancing the economic viability of biodiesel production plants. Image 1 • Glycerol supercritical water reforming process is annexed to three biodiesel plants. • The developed biodiesel production pathways are techno-economically compared. • Alkali catalyst biodiesel production from acid-treated WCO is economically optimal. • Glycerol valorization into hydrogen can economize biodiesel production process. [ABSTRACT FROM AUTHOR]