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In this study, two wind-solar-based polygeneration systems namely CES-1 and CES-2 are developed, modeled, and analyzed thermodynamically. CES-1 hybridizes a heliostat based CSP system with wind turbines while CES-2 integrates heliostat-based CPVT with wind turbines. This study aims to compare the production and thermodynamics performance of two heliostat based concentrated solar power technologies when hybridized with wind turbines. The systems have been modeled to produce, freshwater, hot water, electricity, hydrogen, and cooling with different cycles/subsystems. While the overall objective of the study is to model two polygeneration systems with improved energy and exergy performances, the performances of two solar technologies are compared. The wind turbine system integrated with the comprehensive energy systems will produce 1.14 MW of electricity and it has 72.2% energy and exergy efficiency. Also, based on the same solar energy input, the performance of the heliostat integrated CPVT system (CES-2) is found to be better than that of the CSP based system (CES-1). The polygeneration thermal and exergy efficiencies for the two systems respectively are 48.08% and 31.67% for CES-1; 59.7% and 43.91% for CES-2. Also, the electric power produced by CES-2 is 280 kW higher in comparison to CES-1.

The growing interest in hybrid nanofluids is due to the synergistic effects of nanoparticles, which could give them better heat transfer properties as compared to base fluids, and conventional nanofluids. Several factors like temperature and volume fraction have been used in explaining the behaviours of hybrid nanofluids, however, the need to investigate comprehensively, the mixing ratios of hybrid nanofluids, remains a critical research area in the development of efficient nanofluids as heat transfer fluids. In this study, three mixture ratios of 1:1:1 (33.3% Al2O3, 33.3% ZnO, 33.3% Fe3O4), 1:2:1 (25% Al2O3, 50% ZnO, 25% Fe3O4), and 1:1:2 (25% Al2O3, 25% ZnO,50% Fe3O4) ternary hybrid nanofluid (THNF) are synthesized at volume concentrations of 0.5%, 0.75%, 1%, and 1.25%. All experiments were carried out at a temperature range between 25 °C-65 °C. The effect of temperature, volume concentration, mixture ratio, are examined, as well as the development of a machine learning model for accurate prediction. The thermal conductivity and dynamic viscosity behaviour of the THNF were investigated. The result showed that temperature and volume concentration significantly affected the thermophysical properties of the fluid. The optimum Thermal Conductivity enhancement (TCE) was retrieved for the 1:1:1 THNF, at 36.018%. The 2:1:1, and 1:2:1 mixture ratios had a 32.92%, and 31.68% TCE respectively. At 1% volume concentration, the optimum TCE (as compared with water) for the mono, hybrid, and THNF measured are 18.98%, 28.58%, and 32.45% respectively. It is seen that the least viscosity was recorded for the 1:1:1 mixture ratio (0.001 Pa.s), while the highest viscosity was measured for the 2:1:1 THNF mixture ratio (0.021 Pa. s). The Gaussian process regression (GPR) gave an excellent prediction showing an R2 value of 0.9656, and 0.934 for the thermal conductivity and dynamic viscosity prediction respectively. In terms of application to solar thermal systems, the low viscosity of 1:1:1 Al2O3–ZnO-Fe3O4 THNF makes that a low-pressure drop and pump work is required in practical applications of the 1:1:1 Al2O3–ZnO-Fe3O4 THNF.

A flat-plate collector is one of the most common solar collector systems due to its comparatively lower cost and maintenance. However, the performance of this type of collector is low; thus, research studies in the past decades have focused on improving its efficiency through various plate configurations and efficient working fluids. This study recognizes the research gap regarding the influence of nanoparticle shapes and their effects on improving the heat transfer properties in flat-plate collectors. In this study, fly ash nanofluid at 0.5% (with a range of nanoparticle sizes) was used as a working fluid to investigate the performance of a flat-plate collector. This study analyzed the behavior of the collector system via a range of Reynolds numbers in its laminar regime, between 800 and 2000. The results measured in this study showed that the maximum energy efficiency measured was 73.8%, which was recorded for the fly ash nanofluid at a nanoparticle size of 11.5 nm. At a Reynolds number of 2000, the fly ash nanofluid with a nanoparticle size of 11.5 nm showed a top heat loss coefficient of 4.78 W/m2K, while the top heat loss coefficient of a nanoparticle size (NPS) of 114 nm was 5.17 W/m2K. This study provides a framework for the significance of the nanoparticle size in the synthesis of nanofluids in both mono and hybrid composites and application in solar collector systems.

The deployment of photovoltaic technology in global electricity generation has reduced the dependence on fossil fuels and the adverse effect of global warming climate changes. However, the variabil...

Ambitious energy efficiency goals constitute an important roadmap towards attaining a low-carbon society. Thus, various building-related stakeholders have introduced regulations targeting the energy efficiency of buildings. However, some countries still lack such policies. This paper is an effort to help bridge this gap for Northern Cyprus, a country devoid of building energy regulations that still experiences electrical energy production and distribution challenges, principally by establishing reference residential buildings which can be the cornerstone for prospective building regulations. Statistical analysis of available building stock data was performed to determine existing residential reference buildings. Five residential reference buildings with distinct configurations that constituted over 75% floor area share of the sampled data emerged, with floor areas varying from 191 to 1006 m2. EnergyPlus models were developed and calibrated for five residential reference buildings against yearly measured electricity consumption. Values of Mean Bias Error (MBE) and Cumulative Variation of Root Mean Squared Error CV(RMSE) between the models’ energy consumption and real energy consumption on monthly based analysis varied within the following ranges: (MBE)monthly from –0.12% to 2.01% and CV(RMSE)monthly from 1.35% to 2.96%. Thermal energy required to maintain the models' setpoint temperatures for cooling and heating varied from 6,134 to 11,451 kWh/year.

Hybrid nanofluids have been known to provide perceptibly increased heat transfer characteristics over conventional fluid, and so have been experimentally applied to solar collector applications. Recently, attention has grown towards three-particle hybrid nanocomposites, to investigate their increased thermophysical properties for heat transfer applications. This study numerically investigates the practical application of CuO-MgO-TiO2 ternary nanofluids in a photovoltaic thermal (PV/T) collector. The proposed model explores the effect of volume fraction, solar irradiation, and mass flow rate on the performance of the collector system. The result showed an improved electrical efficiency of 13.54%. 58.38% and 15.68% thermal efficiency and energy efficiency respectively were also gotten, calculated at an optimum volume fraction of 0.01. The maximum cell temperature drop was 8.24 °C measured at a mass flow rate of 0.1 kg s−1. The study also concludes that a maximum increase of 11.14% of the total PV/T system was achieved by the use of ternary nanofluid. The study also investigated the pressure drop and pumping power of the PV/T collector with and without nanofluid. The result showed that a lower pressure drop and pumping power for the CuO–MgO–TiO2 ternary nanofluid which makes it more desirable as compared to the Al2O3–ZnO hybrid nanofluid. Finally, it is shown that the performance of the PV/T collector depends highly on the volume fraction of the ternary nanofluid.

Unlike previous studies where models/methods used in determining the carbon emission are presented, in this paper, a detailed analysis of the causes, trends, and solutions to carbon emission in Africa is presented. Economic development plays a crucial role in the well-being of a country/continent, thereby, affecting energy consumption. The impact of economic development on Africa's carbon (CO2) emissions trend is first investigated. After which, three neural network models are developed to predict the future trend of total CO2 emission in the continent. Then, the use of renewable energy (RE) sources for power generation is analyzed/proposed as a viable solution for CO2 emission reduction in Africa. Finally, the impact of battery electric vehicles (BEVs) integration and hydrogen production in maximizing RE production in Africa's largest economy is analyzed. Secondary data of the economic indicators for twenty-five different African countries have been used to justify the effect of economic development on their carbon emission. From the results of the analyses, gross national income and carbon emissions in all sectors were found to be significantly positively correlated. That is, as national wealth across Africa increases, carbon emissions in the continent increase. Also, the predicted total annual CO2 emission showed that most countries will witness an increase in total CO2 emission by 2022 in comparison to 2018. The proposed RE-based method for power generation showed that the CO2 emission from the power industry can be reduced to zero for an African country. Nevertheless, the use of BEVs and the production of hydrogen will be integral in achieving this.

Unlike steam and gas cycles, the Kalina cycle system can utilize low-grade heat to produce electricity with water-ammonia solution and other mixed working fluids with similar thermal properties. Concentrated photovoltaic thermal systems have proven to be a technology that can be used to maximize solar energy conversion and utilization. In this study, the integration of Kalina cycle with a concentrated photovoltaic thermal system for multigeneration and hydrogen production is investigated. The purpose of this research is to develop a system that can generate more electricity from a solar photovoltaic thermal/Kalina system hybridization while multigeneration and producing hydrogen. With this aim, two different system configurations are modeled and presented in this study to compare the performance of a concentrated photovoltaic thermal integrated multigeneration system with and without a Kalina system. The modeled systems will generate hot water, hydrogen, hot air, electricity, and cooling effect with photovoltaic cells, a Kalina cycle, a hot water tank, a proton exchange membrane electrolyzer, a single effect absorption system, and a hot air tank. The environmental benefit of two multigeneration systems modeled in terms of carbon emission reduction and fossil fuel savings is also studied. The energy and exergy efficiencies of the heliostat used in concentrating solar radiation onto the photovoltaic thermal system are 90% and 89.5% respectively, while the hydrogen production from the two multigeneration system configurations is 10.6 L/s. The concentrated photovoltaic thermal system has a 74% energy efficiency and 45.75% exergy efficiency, while the hot air production chamber has an 85% and 62.3% energy and exergy efficiencies, respectively. Results from this study showed that the overall energy efficiency of the multigeneration system increases from 68.73% to 70.08% with the integration of the Kalina system. Also, an additional 417 kW of electricity is produced with the integration of the Kalina system and this justifies the importance of the configuration. The production of hot air at the condensing stage of the photovoltaic thermal/Kalina hybrid system is integral to the overall performance of the system.

The performance analysis of a novel multi-generation (MG) system that is developed for electricity, cooling, hot water and hydrogen production is presented in this study. MG systems in literature are predominantly built on a gas cycle, integrated with other thermodynamic cycles. The aim of this study is to achieve better thermodynamic (energy and exergy) performance using a MG system (without a gas cycle) that produces hydrogen. A proton exchange membrane (PEM) utilizes some of the electricity generated by the MG system to produce hydrogen. Two Rankine cycles with regeneration and reheat principles are used in the MG configuration. Double effect and single effect absorption cycles are also used to produce cooling. The electricity, hot water, cooling effect, and hydrogen production from the multi-generation are 1027 kW, 188.5 kW, 11.23 kg/s and 0.9785 kg/h respectively. An overall energy and exergy efficiency of 71.6% and 24.5% respectively is achieved considering the solar parabolic trough collector (PTC) input and this can increase to 93.3% and 31.9% if the input source is 100% efficient. The greenhouse gas emission reduction of this MG system is also analyzed.

The main aim of this study is to review researches that have been carried out on solar assisted HVAC systems. The objective is to design a basic solar assisted air conditioning system that ...

The prediction accuracy of support vector regression (SVR) is highly influenced by a kernel function. However, its performance suffers on large datasets, and this could be attributed to the computational limitations of kernel learning. To tackle this problem, this paper combines SVR with the emerging Harris hawks optimization (HHO) and particle swarm optimization (PSO) algorithms to form two hybrid SVR algorithms, SVR-HHO and SVR-PSO. Both the two proposed algorithms and traditional SVR were applied to load forecasting in four different states of Nigeria. The correlation coefficient (R), coefficient of determination (R2), mean square error (MSE), root mean square error (RMSE), and mean absolute percentage error (MAPE) were used as indicators to evaluate the prediction accuracy of the algorithms. The results reveal that there is an increase in performance for both SVR-HHO and SVR-PSO over traditional SVR. SVR-HHO has the highest R2 values of 0.9951, 0.8963, 0.9951, and 0.9313, the lowest MSE values of 0.0002, 0.0070, 0.0002, and 0.0080, and the lowest MAPE values of 0.1311, 0.1452, 0.0599, and 0.1817, respectively, for Kano, Abuja, Niger, and Lagos State. The results of SVR-HHO also prove more advantageous over SVR-PSO in all the states concerning load forecasting skills. This paper also designed a hybrid renewable energy system (HRES) that consists of solar photovoltaic (PV) panels, wind turbines, and batteries. As inputs, the system used solar radiation, temperature, wind speed, and the predicted load demands by SVR-HHO in all the states. The system was optimized by using the PSO algorithm to obtain the optimal configuration of the HRES that will satisfy all constraints at the minimum cost.

Hybrid Renewable Energy Systems (HRESs) have been touted as an appropriate way for supplying electricity to remote and off-grid areas in developing countries, especially in sub-Saharan Africa (SSA), where rural electrification challenges are the most pronounced. This study proposes a two-step methodology for optimizing and analyzing a stand-alone photovoltaic/wind/battery/diesel hybrid system to meet the electricity needs of Fanisua, an off-grid and remote village of northern Nigeria. In the first step, the MATLAB environment was used to run simulations and optimize the system via the genetic algorithm. Then, techno-economic and emissions analysis was carried out in the second step to compare the proposed system to the existing traditional modes of rural electrification in sub-Saharan Africa, namely, the grid-extension and diesel generator. The break-even distance parameter was adopted in the comparison with grid-extension. Besides, the hypothetical project of replacing the diesel generator by the optimal system was analyzed using the Simple Payback Period (SPP) and Net Present Value (NPV) parameters. The resulting optimal design architecture included an 89.271-kW photovoltaic array, a 100.31-W diesel generator, and 148 batteries with a total annualized cost (TAC) and cost of energy (COE) of USD 43,807 and USD 0.25/kWh, respectively. The break-even distance found was 16.2 km, while the NPV and SPP of the hypothetical project were USD 572,382 and 2.8 years, respectively. The savings in carbon dioxide (CO2) emissions of the proposed system compared to the grid extension and the diesel generator were found to be 85,401.08 kg/year and 122,062.85 kg/year, respectively. This study highlighted the role that solar PV-based HRESs could play in the sustainable electricity supply in rural areas of sub-Saharan Africa.

This research designed a multigeneration system that meets the energy requirement of a rural community in Nigeria. This system is powered by the biogas produced from maize silage and chicke...

A novel multi-generation system (MGS) that comprises two absorption cycles, two Rankine cycles (RCs), and a hot water (HW) production chamber is studied in this research. It is designed to utilize the waste heat from the first Rankine cycle as a thermal energy input for the second Rankine cycle and a double-effect absorption cycle (DEAC). The waste heat from the second Rankine cycle serves as heat input to a single-effect Rankine cycle. Regeneration and reheat principles are also applied to the Rankine cycles. The objective of the study is to develop an MGS without a gas cycle that can achieve higher energy and exergy efficiencies. Two concentrated solar technologies, namely, parabolic trough collectors (PTCs) and heliostats are used to power the designed system. The environmental benefit of the system is also analyzed. The energy and exergy efficiencies of the novel MGS presented in this study are 73.11% and 50.72%, respectively. The application of solar thermal technologies to power the system reduces the overall energy and exergy efficiencies, respectively, to 56.12% and 38.39% for the solar PTC and 41.89% and 29.06% for heliostats. The energy and exergy coefficient of performances (COPs) are 0.754 and 0.349 for the single-effect absorption cycle (SEAC), respectively. As much as 752.7 kg/h of CO2, 2.13 kg/h of NOx, and 4.21 kg/h of SOx will be saved from being emitted to the atmosphere.

Ternary nanofluids are a new type of fluids with three nanoparticles dispersed in a base fluid, and they have been experimentally shown to have improved thermophysical and rheological properties as compared to conventional or hybrid nanofluids. This study presents a numerical computation of investigating the performance of Photovoltaic/thermal collectors by utilizing Al2O3-ZnO-Fe3O4/water ternary nanofluid. The preparation of the nanofluid was done using a two-step method and analyzed for stability using Zeta potential analysis. The effect of the mixture ratio of the nanofluid on the thermal and electrical efficiency of the Photovoltaic/thermal system is investigated. The price-performance factor of the ternary nanofluid is firstly computed to determine the optimum volume concentration for practical application. This study also investigates the effect of nanofluid mass flow rate, volume fraction, mixture ratio and solar irradiation on the Photovoltaic/thermal system. From an economic standpoint, the system was estimated using the Price-performance factor and results showed that the 0.5 vol% Al2O3-ZnO-Fe3O4 ternary hybrid nanofluid was most suitable for laminar flow and turbulent flow regimes. The optimum electrical and thermal efficiency measured in this study was 13.75% and 59.38% respectively. This study also recorded an optimum cell temperature reduction of 8.81 °C. The mixture ratio measured for optimum PV/T performance was 0.33. The maximum exergy efficiency and PV/T total exergy efficiency recorded are 1.53% and 14.77%. The ternary nanofluid based PV/T system saved 19948.04 kgCO2 annually, as compared to 18719.88 kgCO2 when water was used as heat transfer fluid. The payback period was calculated to be 2.63 years for the ternary hybrid nanofluid based PV/T system.

Excessive amount of ammonia slows down exoelectrogenic bacteria activities in microbial fuel cells (MFCs). The aim of this study is to analyze the impact of wastewater concentration and fee...

Decade research on nanofluids have solidified the claim that they have excellent heat transfer properties. The properties of mono nanofluids can be optimized by varying the volume concentration of the nanoparticle, however, there is a limit to this due to the challenge of the trade-off of the net negative of viscosity increase. In resolving this limitation, hybrid nanofluids have been synthesized by researchers to maximize the unique properties of different types of nanoparticles. The early days of hybrid nanofluid experimentations consisted of two-particle nanofluids, however, in recent years, a new class of working fluids has been discovered and extensively explored, consisting of three solid nanoparticles dispersed in a conventional fluid. These fluids are referred to as ‘ternary nanofluid, 'ternary hybrid nanofluid’ or ‘trihybrid nanofluids’. This paper gives a comprehensive review of all studies that have synthesized this new class of nanofluids. The major focus in this study was given to their synthesis methods, characterizations, stability tests, thermophysical properties (thermal conductivity, specific heat capacity, and viscosity). This study also reviews the heat transfer applications of ternary nanofluids. The ternary nanofluids are shown to significantly increase the thermal conductivity and heat transfer properties of base fluids. The type and sizes, as well as mixture ratio of nanoparticles are important factors that determine the effectiveness of ternary nanofluids. Several areas still need to be covered for proper understanding of the hybridization effects of three particle nanofluids, like the effect of combining different nanoparticle types, particle sizes, nanoparticle shape, and base fluids.

Nanofluids have gained tremendous research interests in diverse fields of study due to their improved properties, especially as heat transfer fluids. Numerous studies have revealed the characteristics, limitations, and applicability of single type nanoparticles and the attributes of their colloidal mixtures. The discovery of the synergistic effect of nanoparticles, as relating to their improved thermophysical properties have been further explored in experimental and numerical studies of hybrid nanofluids. While the major focus has been on thermal conductivity, and viscosity, another extremely important property that gets little study attention is the specific heat capacity, which is a key thermal property in energy systems. Proper understanding of the specific heat capacity (SHC) of hybrid nanofluids is a sine qua non for proper decisions for heat transfer and heat storage applications. The crux of this review study is to give a detailed and comprehensive review of the specific heat capacity of hybrid nanofluids. The synthesis, characterization, and stability of hybrid nanofluids are presented. Furthermore, the different effects like temperature, volume concentration, mixture ratio, and particle size that influence the SHC behaviour of hybrid nanofluids are analyzed in this study. A compilation and discussion on correlation and machine learning models developed for hybrid nanofluids are also presented. Results suggest that volume concentration have an inverse relationship with the SHC of hybrid nanofluids, an increase in temperature improves the SHC of hybrid nanofluids, and this is more significant at temperatures above 50 ℃. Finally, although scarcely researched, the SHC is also affected by the size of the nanoparticles.

The utilization of solar thermal collectors has increased significantly in the last decade. The heat transfer fluids that is used in the design of these systems has notable effects on their performance. The recent discoveries of hybridized nanofluids, give a promising approach for investigating the performance of parabolic trough collectors (PTC), especially at different design conditions and environmental parameters. This study investigates the thermodynamic performance of a Kalina cycle incorporated with a parabolic trough collector that utilizes ternary nanofluid as a heat transfer fluid. The use of mono, hybrid and ternary nanofluids (THNF) in the parabolic trough collector is examined based on their impact on the efficiency of thermal system. The nanofluids considered are Al2O3, Al2O3–Fe, Al2O3–ZnO, and CuO–MgO–TiO2. The performance of integrated cycle based on the effect of solar irradiation and volume fraction of the nanofluids are studied and compared with conventional fluids namely: thermal VP1 oil, DowThermal oil, and Salt (7NaNO3, 40NaNO2, 53KNO2). In addition, an optimization study is conducted using genetic algorithm to maximize the net power output of the Kalina cycle and the exergetic efficiency of overall system. The results showed that performance of the system which uses nanofluids as a working fluid was higher than the systems using conventional fluids. Furthermore, the results demonstrate that maximum net power output of the system is recorded when Al2O3, Al2O3–Fe, Al2O3–ZnO, and CuO–MgO–TiO2 nanoparticles are used. The power outputs were evaluated as 59.72 kW, 56.64 kW, 54.54 kW, and 61.21 kW respectively. The optimization study reveals that the optimum exergetic efficiency when Al2O3, Al2O3–Fe, Al2O3–ZnO, and CuO–MgO–TiO2 nanofluids are used can reach up to 21.0%, 17.2%, 10.8%, and 25.1% respectively.

Agriculture and its corresponding farms are an integral part of every society/country. In recent years, the energy consumption by farms has risen as sophisticated technologies (that require a high amount of energy) are used for the pre-processing/storage of farm produce. In a bid to advance the transition toward cleaner energy consumption in farms, the thermodynamic assessment of two innovative high-performance solar-based multigeneration systems is presented in this study. Based on the identified most crucial energy needs in farms, the multigeneration systems are designed to produce electrical power, cooling/refrigeration effect, hydrogen, and domestic hot water. In comparison to existing literature, this study is novel as it analyzes the daily performance of the multigeneration systems based on the integration/comparison of two storage techniques. While thermal storage is integrated with one multigeneration system (MGS-TS), the power-to-hydrogen conversion and use of the hydrogen in a solid oxide fuel cell is considered as the storage mechanism in the second system (MGS-SOFC). To analyze the daily performance of the systems, solar parabolic trough collectors are used to produce the input thermal energy based on a 6-hour availability timeframe per day, and the storage systems are designed to power the system for the remaining 18 h. The multigeneration systems developed are analyzed using the energy/exergy approach while the economic costs of the systems are also compared. The effect of different crucial parameters including, ambient temperature, discharge periods, dispatch rates, etc. on key variables related to the systems is investigated. Based on the performance assessment of the two high-performance systems modeled in this study, the overall energetic and exergetic efficiencies are 55.37% and 53.70% for MGS-TS, and 51.12% and 46.82% for MGS-SOFC. The total daily electricity, cooling/refrigeration effect, and hot water useful outputs from the two multigeneration systems are 61,630 kWh/day, 7,939.1 kWh/day, and 125,178 Liters/day for MGS-TS; and 34,597 kWh/day, 15,504 kWh/day, and 129,686 L/day for MGS-SOFC respectively. While the performances of the two systems differ slightly, the unique advantages of each are embedded in their useful energy products.

In this experimental study, the specific heat capacity of water-based Fe3O4-Al2O3-ZnO was fabricated. Three mixture ratios of 1:1:1 (33.33%% Fe3O4, 33.33%% Al2O3, 33.33%% ZnO), 1:2:1 (25% Fe3O4, 50% Al2O3, 25% ZnO,) and 1:1:2 (25% Fe3O4, 25% Al2O3, 50% ZnO,) were synthesized at volume fraction of 0.5%, 0.75%, 1% and 1.25%. All the experiments were carried out at a temperature range of 25°C and 65°C. Zeta potential test and particle size analyzer were used in examining the dispersal stability of the nanofluids, and nanoparticle size, respectively. Also, a high-resolution scanning electron microscope was used in describing the morphological structure of the nanocomposites. The result of the study showed that there exists a linear effect of temperature on the specific heat capacity of the ternary hybrid nanofluid. Also, when the volume concentration increases, it causes the specific heat capacity to decrease. At the mixture ratio of 1:1:1(Fe3O4-Al2O3-ZnO), 1:2:1 (Fe3O4-Al2O3-ZnO) and 1:1:2 (Fe3O4-Al2O3-ZnO), the maximum specific heat capacity increment of 11.9399%, 14.6491% and 13.5572% respectively was recorded at 1.25% volume concentration and 25°C temperature, as compared to the base fluid. The experimental result showed a `peaking effect` in the specific heat capacity, which was measured at a mixture ratio of 1:1:1. The least specific heat capacity values recorded are for the mixture ratio of 1:2:1. Correlation and machine learning models were developed in this study, and the result showed that the most accurate prediction of the experimental data was obtained using the support vector regression model. When the support vector regression and correlation models were compared to the experimental results, the maximum deviation recorded was 0.2% and 12.467% respectively.

In light of the popular gain of renewable energy sources and solar energy technologies in particular, photovoltaic thermal systems present an interesting approach towards cogeneration of electricity and heat. The extraction of heat from the photovoltaic array for use also serves the purpose of reducing the operating temperature of the solar cells to improve their power conversion efficiency. This study analyzes the possibility of incorporating a PV/T system with an absorption system. Three different systems are considered; the single effect, double effect & triple effect absorption systems driven by heat from the PV/T. It is evident that the triple effect absorption cooling system has the highest coefficient of performance thus giving a greater cooling benefit for the same input energy from the PV/T.

In this research, a novel trigeneration powered by a renewable energy (RE) source is developed and analyzed. The trigeneration system is designed to produce electricity, hot water, and cooling using two steam cycles, a gas cycle, hot water chamber, and an absorption cycle. The RE source considered in the scope of this study is biogas generated from chicken manure and maize silage. The energy and exergy analysis of the trigeneration system is performed with the aim to achieve higher efficiencies. The efficiencies are presented based on power generation, cogeneration (electricity and cooling) and trigeneration. The overall trigeneration energy and exergy efficiency for the system developed is 64% and 34.51%. The exergy destruction within the system is greatest in the combustion chamber.

The amelioration of photovoltaic (PV) and photovoltaic/thermal (PV/T) systems have garnered increased research interest lately, more so due to the discovery of the thermal property augmentation of nanofluids. The overarching goal of this study is to conduct a comparative analysis of mono, hybrid, and ternary hybrid nanofluids utilized as fluids for heat transfer applications and particularly as cooling mediums in PV/T applications. Al2O3, ZnO, Al2O3-ZnO, and Al2O3-ZnO-Fe3O4 nanofluids are synthesized at 1% volume concentration using the two-step method. The zeta potential tests carried out showed that the fluids have high stability. The numerical model developed in this study was validated using real data culled from Cyprus International University. The findings in this study showed that the Al2O3-ZnO-Fe3O4 ternary hybrid nanofluid and ZnO mono nanofluid were more efficient heat transfer fluids for the PV/T system. The optimum relative electrical PV/T efficiency against that of the PV is 8.13% while the electrical and thermal enhancement recorded in this study was 1.79% and 19.06%, respectively, measured for the ternary hybrid nanofluid based PV/T system. This present study shows that despite the limitation of pumping power and pressure drop associated with nanofluid in thermal systems, the close performance evaluation criterion values as compared with water is positive for practical utilization of nanofluid in PV/T systems.

This paper provides a theoretical comparative analysis for the thermodynamic performance of a cascade refrigeration system using different refrigerants paired with carbon dioxide (CO2). The cascade refrigeration system consists of a low-temperature loop and a high-temperature loop. The former loop uses CO2 as working fluid while the later loop uses four different refrigerants namely HFE7000, HFE7100, NH3 and R134a. HFE7000 and HFE7100 are new refrigerants called hydrofluroethers. A code is developed in engineering equation solver for the basic energy and exergy balance equations of the system. For the reference conditions; 223 K evaporator temperature and 308 K condenser temperature, the coefficient of performance was obtained as 1.398, 1.3363, 1.309, and 1.221 for refrigerant couples NH3/CO2, R134a/CO2, HFE7000/CO2, and HFE7100/CO2 respectively. The exergy efficiencies for the reference conditions were calculated as 47.01%, 45.84%, 44.30%, and 41.06% respectively for NH3, R134a, HFE7000, and HFE7100 refrigerants paired with CO2. The condenser and evaporator temperatures and heat exchanger effectiveness were varied to determine their effect on the cooling coefficient of performance and the exergy efficiency. The evaporator has been identified as the component having the highest rate of exergy destruction, whereas the expansion valve in the low temperature loop has the lowest rate of exergy destruction. The total equivalent warming impact (TEWI) values of the refrigerant pairs of the system are calculated and contrasted for the reference operating conditions for a cooling load of 175 kW. The HFE7000 is considered as a promising refrigerant according to the COP, exergy efficiency, and TEWI results for the proposed cascade refrigeration system, as it can be used as a substitute to R134a.

The world has not been able to achieve minimum greenhouse gas emissions in buildings’ energy consumptions because the energy and emissions optimization techniques have not been fully utilized. Thermal comfort is one of the most important issues for both residential and commercial buildings. Out of the 40% of global energy consumed by buildings, a large fraction is used to maintain their thermal comfort. In this study, a comprehensive review of the recent advancements in building energy conservation and efficiency application is presented based on existing high-quality research papers. Additionally, the retrofit of the heating/cooling and hot water system for an entire community in Cyprus is presented. This study aims to analyze the technical and environmental benefits of replacing existing electric heaters for hot water with heat pump water heating systems and the use of heat pump air conditioners for thermal comfort in place of the existing ordinary air conditioners for space heating and cooling. One administrative building, 86 apartments (including residential and commercial) buildings, and a restaurant building is retrofitted, and the feasibility of the project is determined based on three economic indicators, namely; simple payback period (SPP), internal rate of return (IRR), and net present value (NPV). The electrical energy required by the hot water systems and the heating/cooling system is reduced by 263,564 kWh/yr and 144,825 kWh/yr, respectively. Additionally, the retrofit project will reduce Cyprus’ CO2 emission by 121,592.8 kg yearly. The SPP, IRR, and NPV for the project show that the retrofit is economically feasible.

One of the main challenges in renewable energy integrated multigeneration and comprehensive system researches is the inability to study the transient performance analysis of the system. In this study, a novel wind-biomass comprehensive energy system for power, cogeneration, trigeneration, and multigeneration is proposed. This system is analyzed in both steady-state and transient conditions using energy and exergy approaches. Rice husk is considered as the raw material for biomass fuel. The comprehensive system is modeled to produce electricity, freshwater, hot water, and hydrogen with a steam cycle, an organic Rankine cycle, a double stage refrigeration system, a proton exchange membrane electrolyzer, and a hot water chamber. Electric vehicles are integrated with the system in time-based process modeling to ensure load stability and maximize electricity production. The overall exergy and energy efficiencies of the proposed comprehensive system increase from 24.91% and 27.42% while producing electricity to, 26.08% and 35.22% when multigenerating. Based on the transient analysis, this system is capable of meeting the energy demand of a rice-producing factory, campus, and its surrounding community. The process modeling also shows the hourly performance of the system and its load stability.

One of the challenges faced by renewable energy (RE) powered multigeneration system is the unavailability of RE resources at different times. In this research, a novel comprehensive energy system powered with wind turbines, concentrated photovoltaic/thermal and biogas is modelled and analyzed using energy and exergy approach. Multiple useful products such as electricity, hot air, hydrogen, fresh water, cooling effect and hot water will be produced by the system. Four different operational scenarios namely; CPVT/wind, wind/biogas, CPVT/biogas, and biogas only are considered for this comprehensive energy system. Thermal energy storage is incorporated with the system, in order to save thermal energy that will be used during hours without solar radiation. Furthermore, the CO2 emissions saved, in comparison with the use of different fossil fuel sources is analyzed. The maximum productions from the comprehensive system are: 3.4 MW of electricity; 12.41 L/sec of Hydrogen; 279.4 kW of cooling effect; 17.546 kg/s of hot air; 144.18 L/min of hot water and 10.31 L/min of fresh water. The overall energetic efficiency of the system considering all the case studies ranges from 64.91% to 71.06% while the exergetic efficiencies ranges from 31.80% to 53.81%. The CO2 emission analysis results show that the system is environmentally friendly.

This study presents an experimental nanoparticle synthesis and the numerical analysis of a parabolic trough collector (PTC) operating with olive leaf synthesized TiO2/water nanofluid. The PTC is modeled after the LS-2 collector for various operating conditions. An analysis of the heat transfer and entropy generation in the PTC is carried out based on the first and second laws of thermodynamics for various parameters of nanoparticle volumetric concentration (0 ≤ φ ≤ 8%), mass flow rate (0.1 ≤ m˙ ≤ 1.1 kg/s), and inlet temperatures (350–450 K) under turbulent flow regime. The effect of these parameters is evaluated on the Nusselt number, thermal losses, heat convection coefficient, outlet temperature, pressure drop, entropy generation rate, and Bejan number. The results show that the values of the Nusselt number decrease with higher concentrations of the nanoparticles. Also, the addition of nanoparticles increases the heat convection coefficient of the nanofluid compared to water. The thermal efficiency of the system is improved with the use of the new nanofluid by 0.27% at flow rates of 0.1 kg/s. The entropy generation study shows that increasing the concentration of nanoparticles considerably decreases the rate of entropy generation in the system. It is also observed that increasing the volumetric concentration of nanoparticles at low mass flow rates has minimal effect on the rate of entropy generation. Finally, a correlation that provides a value of mass flow rate that minimizes the entropy generation rate is also presented for each values of inlet temperature and nanoparticle volumetric concentration.