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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 uses CO2 as a refrigerant. The performance analysis of the system is done with EES and Copeland Scroll software. Research about the solar-assisted HVAC system has advanced as some studies reveal solar-assisted system that can operate for 24 h. In this kind of system, the storage is important and takes a sizeable amount of space and cost in the design. Also, LiBr is one of the most commonly used efficient absorber in absorption refrigeration for HVAC. The details of all the findings and the performance of the system designed is given in the paper. [ABSTRACT FROM AUTHOR]

Nigeria is one of most populated countries in the world. With a population of about 170 million people, the nation is enriched with diverse renewable and non-renewable energy sources. Despite this huge energy potential, only about 50% of her population have access to electricity. The main objective of this review is to present and analyze the renewable energy potentials of Nigeria with special attention and consideration to the past, present and future of solar energy development. The country aims to achieve electricity production of 9.74%, 18% and 20% of her electricity from renewables by 2015, 2020 and 2030, respectively. Solar energy is expected to produce 1.26%, 6.92% and 15.27% of the electricity consumed by 2015, 2020 and 2030, respectively. If these targets are met, the proportion of the population with access to electricity will increase drastically. Data collected from various reputable energy sources and Journals are reviewed. Nigeria has renewable energy resources including biomass, wind, hydropower and solar energy. These resources can sufficiently meet the country's energy demands, but statistics show that Nigeria still lacks adequate supplies to meet her electricity demands. The policies put in place to meet her energy targets and the current status of the country's supply and demand for electricity are discussed in detail. [ABSTRACT FROM AUTHOR]

[Display omitted] • Development of two innovative energy systems for sustainability in agricultural farms. • Thermodynamic comparison of thermal storage and solid oxide fuel cell for energy storage. • Design of solar-based multigeneration systems for 24-hours energy production. • Overall energetic and exergetic efficiencies are 55.37% and 53.70% for MGS-TS, and 51.12% and 46.82% for MGS-SOFC. • Sensitivity analysis of system's performance considering variation in dispatch rates. 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. [ABSTRACT FROM AUTHOR]

Nanofluids are known to have immense potential for heat transfer applications because of their unique thermophysical properties when compared to the conventional heat transfer fluid. Predicting the thermophysical features like thermal conductivity has posed a challenge to their application. This article addresses some of the challenges posed in their prediction by using data sets from several experimental research on various hybrid nanofluids to train an intelligent neural network. The thermal conductivity of hybrid nanofluids is predicted using seven different input variables namely, volume concentration, temperature, the acentric factor of the base fluid, nanoparticle bulk density, mixture ratio of particles, the thermal conductivity, and size of nanoparticles. 715 experimental data points from studies using different hybrid nanoparticles are used in developing a multi-layer perceptron artificial neural network (ANN) and support vector regression (SVR) models. The performance validation of the models is computed using the mean square error (MSE) and the coefficient of determination (R 2 ). The performance result showed an R 2 value of 0.99997 and 0.99788 in the validation phase of the ANN and SVR model, respectively. This indicates that the models are capable of accurately predicting the thermal conductivity of hybrid nanofluids over a wide range of hybrid nanoparticle combinations. Finally, a universal formula using MLP-ANN for predicting the thermal conductivity of hybrid nanofluids is presented. [ABSTRACT FROM AUTHOR]

• Energy and exergy analysis a CPVT and wind turbine integrated comprehensive system. • Integration of biogas powered systems as a backup system and modelling based on four scenarios. • Overall energy efficiency considering all the case studies, ranges from 64.91% to 71.06%. • Also, overall exergy efficiency ranges from 31.80% to 53.81%. • Maximum CO2 emission reduction in comparison to coal fired system is 2680.4 kg/h. 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. [ABSTRACT FROM AUTHOR]

The age-related decline in appetite and food intake - termed "anorexia of ageing" - is implicated in undernutrition in later life and hence provides a public health challenge for our ageing population. Eating behaviour is controlled, in part, by homeostatic mechanisms which sense nutrient status and provide feedback to appetite control regions of the brain. Such feedback signals, propagated by episodic gut hormones, are dysregulated in some older adults. The secretory responses of appetite-related gut hormones to feeding are amplified, inducing a more anorexigenic signal which is associated with reduced appetite and food intake. Such an augmented response would indicate an increase in gut sensitivity to nutrients. Consequently, this review explores the role of gastrointestinal tract nutrient sensing in age-related appetite dysregulation. We review and synthesise evidence for age-related alterations in nutrient sensing which may explain the observed hormonal dysregulation. Drawing on what is known regarding elements of nutrient sensing pathways in animal models, in other tissues of the body, and in certain models of disease, we identify potential causal mechanisms including alterations in enteroendocrine cell number and distribution, dysregulation of cell signalling pathways, and changes in the gut milieu. From identified gaps in evidence, we highlight interesting and important avenues for future research., Competing Interests: Declaration of competing interest This work was supported by a Pump Priming Award from the BBSRC/MRC funded Ageing and Nutrition Sensing Network (Principal Recipient: A.H.). The authors declare no conflicts of interest., (Copyright © 2024. Published by Elsevier Ltd.)

Age-related changes in gut hormones may play a role in anorexia of ageing. The aim of this study was to determine concentrations of ghrelin, PYY, and GLP-1 in older adults exhibiting an anorexia of ageing phenotype. Thirteen older adults with healthy appetite (OA-HA; 8f, 75 ± 7 years, 26.0 ± 3.2 kg m -2 ), fifteen older adults with low appetite (OA-LA; 10f, 72 ± 7 years, 23.6 ± 3.1 kg m -2 ), and twelve young adults (YA; 6f, 22 ± 2 years, 24.4 ± 2.0 kg m -2 ) completed the study. Healthy appetite and low appetite were determined based on BMI, habitual energy intake, self-reported appetite, and laboratory-assessed ad libitum lunch intake. Participants provided a fasted measure of subjective appetite and blood sample (0 min) before consuming a standardised breakfast (450 kcal). Appetite was measured and blood samples were drawn throughout a 240-min rest period. At 240 min, an ad libitum lunch meal was consumed. Relative intake at lunch (expressed as percentage of estimated total energy requirement) was lower for OA-LA (19.8 ± 7.7%) than YA (41.5 ± 9.2%, p < 0.001) and OA-HA (37.3 ± 10.0%, p < 0.001). Ghrelin suppression was greater for OA-LA (net AUC, -78719 ± 74788 pg mL -1 ·240min -1 ) than both YA (-23899 ± 27733 pg mL -1 ·240min -1 , p = 0.016) and OA-HA (-21144 ± 31161 pg mL -1 ·240min -1 , p = 0.009). There were trends for higher GLP-1 concentrations in OA-LA compared with YA at 90 min (8.85 ± 10.4 pM vs. 1.88 ± 4.63 pM, p = 0.073) and 180 min (5.00 ± 4.71 pM vs. 1.07 ± 2.83 pM, p = 0.065). There was a trend for a greater PYY response for OA-LA compared with OA-HA (net AUC p = 0.062). "Anorexigenic response score" - a composite score of gut hormone responses to feeding - showed greater anorexigenic response in OA-LA, compared with YA and OA-HA. No differences were seen in subjective appetite. These observations suggest augmented anorexigenic responses of gut hormones to feeding may be causal mechanisms of anorexia of ageing., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2024. Published by Elsevier Ltd.)

The human ileum contains a high density of enteroendocrine L-cells, which release the appetite-suppressing hormones glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) in response to food intake. Recent evidence highlighted the potential role of food structures in PYY release, but the link between food structures, ileal metabolites, and appetite hormone release remains unclear owing to limited access to intact human ileum. In a randomized crossover trial (ISRCTN11327221; isrctn.com), we investigated the role of human ileum in GLP-1 and PYY release by giving healthy volunteers diets differing in fiber and food structure: high-fiber (intact or disrupted food structures) or low-fiber disrupted food structures. We used nasoenteric tubes to sample chyme from the intact distal ileum lumina of humans in the fasted state and every 60 min for 480 min postprandially. We demonstrate the highly dynamic, wide-ranging molecular environment of the ileum over time, with a substantial decrease in ileum bacterial numbers and bacterial metabolites after food intake. We also show that high-fiber diets, independent of food structure, increased PYY release compared with a low-fiber diet during 0 to 240 min postprandially. High-fiber diets also increased ileal stachyose, and a disrupted high-fiber diet increased certain ileal amino acids. Treatment of human ileal organoids with ileal fluids or an amino acid and stachyose mixture stimulated PYY expression in a similar profile to blood PYY concentrations, confirming the role of ileal metabolites in PYY release. Our study demonstrates the diet-induced changes over time in the metabolite environment of intact human ileum, which play a role in PYY release.

The 'double burden of malnutrition' is a global health challenge that increasingly affects populations in both low- and middle-income countries (LMICs). This phenomenon refers to the coexistence of undernutrition and overweight or obesity, as well as other diet-related non-communicable diseases, in the same population, household or even individual. While noteworthy progress has been made in reducing undernutrition in some parts of the world, in many of these areas, the prevalence of overweight and obesity is increasing, particularly in urban areas, resulting in greater numbers of people who were undernourished in childhood and have overweight or obesity in adulthood. This creates a complex and challenging situation for research experts and policymakers who must simultaneously address the public health burdens of undernutrition and overweight/obesity. This review identifies key challenges and limitations in the current research on the double burden of malnutrition in individuals, including the need for a more comprehensive and nuanced understanding of the drivers of malnutrition, the importance of context-specific interventions and the need for greater attention to the food environment and food systems. We advocate for the re-evaluation of research strategies and focus, with a greater emphasis on multidisciplinary and systems approaches and greater attention to the synergistic relationship between the biological, environmental, commercial and socio-economic determinants of malnutrition. Addressing these key challenges can enable us to better comprehend and tackle the multifaceted and dynamic issues of the double burden of malnutrition, particularly in individuals and work towards more effective and sustainable solutions., (© 2024 The Authors. Nutrition Bulletin published by John Wiley & Sons Ltd on behalf of British Nutrition Foundation.)