Investigation of a novel micro-channel, mini-channel PV/T and thermal modules based solar heat pump systems

Regarding the building energy consumption optimisation, there is a developmental trend to replace traditional fossil fuel sourced energy with, rapidly growing, clean renewable energy. The main source of energy consumption is from hot water, cooling and space heating, which is normally provided by electric heater, gas boiler and/or coal boiler. However, these existing systems have their own drawbacks, such as high operating costs (electric heater), being inconvenient to obtain (gas boiler) and causing environmental pollution (coal boiler). Therefore, it is necessary to develop a clear and convenient energy system to replace these traditional ones, i.e., solar energy, biomass energy.This research aims to investigate two kinds of novel photovoltaic thermal modules (PV/T) based heat pump systems, one with direct-expansion and the other with an indirect-expansion style, to be used for the purpose of space heating, hot water supply and power generation. Compared to existing PV/T modules, the new modules possess novel features that lead to enhanced heat transfer, improved solar efficiency and extended module lifetime. The strength and innovation of PV/T technology in this thesis are as follows: (1) a micro-channel and mini-channel tube is selected as the heat exchanger tube. This special structure improves the heat transfer rate of working fluid inside, enhancing both solar, thermal and electrical efficiencies; (2) compared to existing copper tube heat exchanger, the micro-channel has a much larger contact area, increasing the heat transfer rate; (3) the material of the micro-channel tube and header is aluminum, which has a low cost. These designs were intended to overcome some of the drawbacks and provide experimental data for the development of PV/T technology.For the solar direct-expansion heat pump system, more than one-month time testing was carried out, and according to the result on a sunny winter day, the average electrical, thermal and overall efficiencies of the micro-channel panels were 13.1%, 56.6% and 69.7% respectively, which were respectively higher by 11.0%, 11.8% and 11.4% than the similar system. The Coefficient of Performance (COP) of the system had a similar variation trend to the solar radiation, with the average COP in the testing day being 4.7.For the solar indirect-expansion heat pump system, again tested in winter, it was found that the average electrical, thermal and overall efficiencies of the mini-channel PV/T panels were 14.5%, 31.7% and 46.2% respectively, which has 9.0%, 5.8% and 6.2% higher efficiency than the existing similar systems. In addition, the mean thermal efficiency of the mini-channel thermal panels is 49.9%, which is a 5% increase compared to existing collector. The average COP of the heat pump is 4.6 during the working time. In summer, the average electrical efficiency of the PV/T panel was 11.5%, and the average thermal efficiency of the thermal panel was 46.8%. The temperature of water in the tank increased from 23oC to 60oC, therefore this water could be used for various applications.The annual economic and environmental analysis results, based on the local weather data, indicate that although the two systems have a higher initial cost, they have a much lower operating cost. Based on the weather data of Taiyuan city, the payback time of these direct and indirect expansions systems are 8.7 years and 5.8 years, respectively. Additionally, these direct and indirect expansion systems can, respectively, reduce CO2 emission by around 91.4 t and 109.1 t annually. Based on the weather data of London, the payback time of the two systems are 6.6 years and 3.5 years, while the CO2 emission reduction are 44.8 t and 76.2 t, respectively.Based on these research results, some amendments are required to improve and promote the systems in the future. These include improving the structure and material of the PV/T panel, reducing manufacturing cost, further optimisation of the system and long-term measurement under real-world conditions. Additionally, seeking policy support is needed from the government to reduce the initial and operating cost.This research shows that these two solar heat pump systems provide a reasonable alternative to the traditional heating system for space heating in rural house. Most of the existing solar energy systems are small scale and designed for producing hot water, while the large-scale solar energy system for space heating in rural houses is rarely researched. Therefore, the experimental and simulation results on these two systems provides fundamental data for developing and improving large-scale solar energy systems

Mathematical and experimental evaluation of a mini-channel PV/T and thermal panel in summer mode

In this paper, a mini-channel PV/T and mini-channel thermal panel hot water system is presented. The thermal panels in this system use mini-channel tube as the heat exchanger, which has a small hydraulic diameter and large heat exchanger area, and this special structure can improve the heat transfer coefficient at the same flow rate than the conventional type. The performance of this system for generating hot water and electricity in summer has been tested, and a simulation model of this operating mode has been developed. Based on a typical day's weather data, the simulation model is verified, and the experimental and simulated results agree with each other very well. The results reveal that the experimental and simulated electrical efficiencies of PV/T panels are 11.5% and 12.6%, respectively. The experimental and simulated thermal efficiencies of thermal collectors are 46.8% and 48.0%, respectively. The experimental and simulated final water temperatures in the tank are 59.3 °C and 60.9 °C, respectively. Based on these results, an error analysis is carried out. The experimental and simulation results of the system in summer provide a fundamental data and method for predicting the annual performance of the system in the future

Plant Leaf Disease Detection Using Deep Learning

Plant leaf diseases pose a danger to food security, and their rapid identification is made more difficult in many areas by a lack of infrastructure. This thesis is a concentrated attempt to address this important problem by utilizing state-of-the-art deep learning techniques, with a focus on the YOLOv5 model, to offer a dependable and effective solution for plant leaf disease detection in agriculture. The introduction emphasizes the serious effects that plant diseases have on a global and financial level, underscoring the critical necessity for early detection to lessen these effects. Driven by the promise of technology to revolutionize agriculture, this work carefully investigates the complex use of deep learning techniques. YOLOv5 is trained to demonstrate its ability to distinguish between healthy and diseased plant leaves using a carefully chosen tomato dataset. The dataset contains nine different types of illnesses. The model achieves an impressive 92.6 percent average precision, indicating a high degree of disease detection accuracy. Plant leaf disease detection in agriculture faces many complicated obstacles, and the successful deployment of the trained model through the Flask framework represents a significant leap in the practical application of deep learning to address these issues. Our multimodal approach places our research at the forefront of efforts to improve agricultural technology and guarantee global food security while also making a significant contribution to the scientific understanding of disease identification and laying the foundation for future advances

Operational performance of a novel heat pump coupled with mini-channel PV/T and thermal panel in low solar radiation

Here we describe a heat pump system coupled with novel PV/T and thermal panels for space heating in low solar radiation conditions. Existing solar indirect-expansion systems connect the solar panels and evaporator of the heat pump in parallel with the heat storage tank. For our system these three components are instead connected in series, which can stabilize the temperature at the inlet of the evaporator and decrease the inlet temperature of the solar panels, leading to improved energy efficiency and the production of much more thermal energy. The experimental results of this system show that the average electrical, thermal and overall efficiency of the PV/T panels are 15.9%, 33.4% and 49.3%, respectively. The average thermal efficiency of the thermal panels is 60.4%, the COP of heat pump is 4.7 and the room temperature is constantly over 18 °C. Based on the experimental results, some improvements are analyzed. We conclude that this operating model can meet the requirement of space heating in low solar radiation environments

Experimental study and exergy analysis of photovoltaic-thermoelectric with flat plate micro-channel heat pipe

Effective cooling of the photovoltaic can enhance electrical conversion efficiency of a photovoltaic system. The combination of photovoltaic and thermoelectric generator provides unique advantages because of their complementary characteristics. In addition, hybrid photovoltaic-thermoelectric can utilize a wider solar spectrum thereby harvesting more energy from the sun. Heat pipes are passive devices that can transfer heat efficiently over a long distance. Therefore, this study presents an experimental investigation and exergy analysis of a photovoltaic-thermoelectric with flat plate micro-channel heat pipe. The experiment is performed in a laboratory using a solar simulator and water-cooling is used for the thermoelectric generator. The effect of thermoelectric load resistance, micro-channel heat pipe back insulation and solar radiation on the performance of the hybrid system is presented and a comparison with a photovoltaic only system is provided. Results show that the hybrid system provides an enhanced performance compared to the photovoltaic only system and absence of insulation behind the micro-channel heat pipe enhances electrical performance of the hybrid system. Furthermore, results show the feasibility of the hybrid system for generating electricity and small hot water. This study will provide valuable guidance for design of photovoltaic-thermoelectric systems with heat pipe and verifies the feasibility of such systems

Analytical investigation of the heat-transfer limits of a novel solar loop-heat pipe employing a mini-channel evaporator

© 2018 by the authors. This paper presents an analytical investigation of heat-transfer limits of a novel solar loop-heat pipe developed for space heating and domestic hot water use. In the loop-heat pipe, the condensate liquid returns to the evaporator via small specially designed holes, using a mini-channel evaporator. The study considered the commonly known heat-transfer limits of loop-heat pipes, namely, the viscous, sonic, entrainment, boiling and heat-transfer limits due to the two-phase pressure drop in the loop. The analysis considered the main factors that affect the limits in the mini-channel evaporator: the operating temperature, mini-channel aspect ratio, evaporator length, evaporator inclination angle, evaporator-to-condenser height difference and the dimension of the holes. It was found that the entrainment is the main governing limit of the system operation. With the specified loop design and operational conditions, the solar loop-heat pipe can achieve a heat-transport capacity of 725 W. The analytical model presented in this study can be used to optimise the heat-transfer capacity of the novel solar loop-heat pipe

Energy performance analysis of a novel solar PVT loop heat pipe employing a microchannel heat pipe evaporator and a PCM triple heat exchanger

This study presents a numerical analysis of the energy efficiency for a novel solar PVT Loop Heat Pipe (PVT-LHP) employing a novel Micro-channel evaporator and a novel PCM heat storage exchanger. It presents a description of the different sub-models in the PVT-LHP system (the PVT model, the microchannel heat collector model and the novel PCM triple heat exchanger model) and the integrated model of the system. The integrated model of the system was solved by ensuring a heat balance at the condenser and the evaporator. A parametric analysis has been performed in order to assess the influence of the environmental parameters (i.e. solar radiation, air temperature, wind velocity), structural parameters (i.e. glazing cover, the number of absorbing microchannel heat pipes, PV cell packing factor), the circulating fluid variables (i.e. cold-water inlet temperature and water mass flow rate) on the energy performance of the system. The novel PVT-LHP has been compared with a onventional Solar PVT-LHP system. It was found that lower solar radiation, lower ambient air temperature, higher wind speed, higher packing factor, lower cold-water inlet temperature and a smaller cover number led to an enhanced electrical efficiency, but a reduced thermal efficiency of the module; whereas a higher coldwater mass flow rate and a greater number of microchannel heat pipes gave rise to both thermal and electrical efficiencies of the module. It was also found that an increase of solar radiation, ambienttemperature, cover number, microchannel heat pipe number and packing factor are favourable factors for the overall COP (Coefficient Of Performance) of the system, whereas an increase of wind velocity and cold water mass flow rate are unfavourable. The study indicated the existence of an optimal cover number, number of microchannel heat pipes and mass flowrate. Under the given design conditions, the electrical, thermal and overall efficiency of the PV/LHP module were 12.2%, 55.6% and 67.8% respectively and the novel system can achieve 28% higher overall energy efficiency and 2.2 times higher COP compared to a conventional system. The integrated computer model developed in this study can be used to design and optimize the novel PVT-LHP heating system

Characterization and comparative genomics analysis of RepA_N multi-resistance plasmids carrying optrA from Enterococcus faecalis

IntroductionThis research aimed to investigate the antibiotic resistance of Enterococcus faecalis from swine farms in Zhejiang Province and the prevalence and transmission mechanism of oxazolidone resistance gene optrA.MethodA total of 226 Enterococcus faecalis were isolated and their resistance to 14 antibiotics was detected by broth microdilution. The resistance genes were detected by PCR.ResultsThe antibiotic resistance rate of 226 isolates to nearly 57% (8/14) of commonly used antibiotics was higher than 50%. The resistance rate of tiamulin was highest (98.23%), that of tilmicosin, erythromycin, tetracycline and florfenicol was higher than 80%, and that of oxazolidone antibiotic linezolid was 38.49%. The overall antibiotics resistance in Hangzhou, Quzhou and Jinhua was more serious than that in the coastal cities of Ningbo and Wenzhou. The result of PCR showed that optrA was the main oxazolidinone and phenicols resistance gene, with a detection rate of 71.68%, and optrA often coexisted with fexA in the isolates. Through multi-locus sequence typing, conjugation transfer, and replicon typing experiments, it was found that the horizontal transmission mediated by RepA_N plasmid was the main mechanism of optrA resistance gene transmission in E. faecalis from Zhejiang Province. Two conjugative multi-resistance plasmids carrying optrA, RepA_N plasmid pHZ318-optrA from Hangzhou and Rep3 plasmid from Ningbo, were sequenced and analyzed. pHZ318-optrA contain two multidrug resistance regions (MDR), which contributed to the MDR profile of the strains. optrA and fexA resistance genes coexisted in IS1216E-fexA-optrA-ferr-erm(A)-IS1216E complex transposon, and there was a partial sequence of Tn554 transposon downstream. However, pNB304-optrA only contain optrA, fexA and an insertion sequence ISVlu1. The presence of mobile genetic elements at the boundaries can possibly facilitate transfer among Enterococcus through inter-replicon gene transfer.DiscussionThis study can provide theoretical basis for ensuring the quality and safety of food of animal origin, and provide scientific guidance for slowing down the development of multi-antibiotic resistant Enterococcus

RNA-Seq Reveals Enhanced Sugar Metabolism in Streptococcus mutans Co-cultured with Candida albicans within Mixed-Species Biofilms

Early childhood caries (ECC), which can lead to rampant tooth-decay that is painful and costly to treat, is one of the most prevalent infectious diseases affecting children worldwide. Previous studies support that interactions between Streptococcus mutans and Candida albicans are associated with the pathogenesis of ECC. The presence of Candida enhances S. mutans growth, fitness and accumulation within biofilms in vitro, although the molecular basis for these behaviors is undefined. Using an established co-cultivation biofilm model and RNA-Seq, we investigated how C. albicans influences the transcriptome of S. mutans. The presence of C. albicans dramatically altered gene expression in S. mutans in the dual-species biofilm, resulting in 393 genes differentially expressed, compared to mono-species biofilms of S. mutans. By Gene Ontology analysis, the majority of up-regulated genes were related to carbohydrate transport and metabolic/catabolic processes. KEGG pathway impact analysis showed elevated pyruvate and galactose metabolism, suggesting that co-cultivation with C. albicans influences carbohydrate utilization by S. mutans. Analysis of metabolites confirmed the increases in carbohydrate metabolism, with elevated amounts of formate in the culture medium of co-cultured biofilms. Moreover, co-cultivation with C. albicans altered transcription of S. mutans signal transduction (comC and ciaRH) genes associated with fitness and virulence. Interestingly, the expression of genes for mutacins (bacteriocins) and CRISPR were down-regulated. Collectively, the data provide a comprehensive insight into S. mutans transcriptomic changes induced by C. albicans, and offer novel insights into how bacterial–fungal interactions may enhance the severity of dental caries

Biochemical and biophysical analyses of tight junction permeability made of claudin-16 and claudin-19 dimerization

The molecular nature of tight junction architecture and permeability is a long-standing mystery. Here, by comprehensive biochemical, biophysical, genetic, and electron microscopic analyses of claudin-16 and -19 interactions—two claudins that play key polygenic roles in fatal human renal disease, FHHNC—we found that 1) claudin-16 and -19 form a stable dimer through cis association of transmembrane domains 3 and 4; 2) mutations disrupting the claudin-16 and -19 cis interaction increase tight junction ultrastructural complexity but reduce tight junction permeability; and 3) no claudin hemichannel or heterotypic channel made of claudin-16 and -19 trans interaction can exist. These principles can be used to artificially alter tight junction permeabilities in various epithelia by manipulating selective claudin interactions. Our study also emphasizes the use of a novel recording approach based on scanning ion conductance microscopy to resolve tight junction permeabilities with submicrometer precision