Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications

An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics

Ultrasound Technology Integration into Drinking Water Treatment Train

Fresh water is one of the main sources for drinking water production. Due to increasing contamination caused by extreme weather events such as flood and drought as well as urbanization activities, the quality of this source continues to deteriorate. In order to maintain producing high-quality water from heavily contaminated sources, more chemicals are added to water in conventional treatment plants. This practice generates serious health problems such as the formation of disinfection by-products (DBPs) and the increase of coagulants residues (e.g., Al) in the treated water. Combining chemical-free techniques with conventional treatment processes can be a potential solution for such problems. When evaluating various techniques, ultrasound appears to be a sensible choice for improving contaminants removal from surface water. This chapter sheds light on the exacerbating problem of fresh water contamination and succinctly reviews chemical-free techniques’ options for water treatment. The focus of this chapter is directed toward providing critical and insightful discussion of fundamentals, mechanisms, and reaction pathways of ultrasound technology for water treatment application. Recommendations for the best location and operating settings of ultrasound application in conventional water treatment train will be provided based on energy saving and minimal downstream impact criteria

Gasification of non-woody biomass: a literature review

Non-woody biomass, having a lower lignin content than woody materials, is a common waste material found in agricultural processing plants and fields. Non-woody biomass is often bulky and has a comparatively low energy content. However, non-woody materials sourced from agricultural waste are abundant and cheap. Experimental studies into gasification of non-woody biomass have been conducted by various researchers. This paper reviews feedstock characteristics, pre-treatments, gasification methods, and future directions of this technology. Due to the heterogeneous nature of non-woody biomass, it is critical to apply suitable pre-treatments prior to gasification. Combining non-woody biomass with a small percentage of high grade carbon sourced from biochar or coal into fuel pellets for co-gasification has the potential to improve fuel quality. Synergistic effects of non-woody biomass-coal/charcoal co-gasification can also reduce tar formation and increase the occurrence of mineral based catalytic reactions. Factors influencing these effects are often complex and require further investigation. 15–20% of the energy content of fuel pellets may be needed to power the biomass pre-treatment process. The gasification of pelletised non-woody waste provides an attractive alternative fuel source to achieve agricultural energy self-sufficiency and off-grid operation

Assessment of Densified Fuel Quality Parameters: A Case Study for Wheat Straw Pellet

An investigation was conducted to examine the impact of additive mixing with wheat straw (WS) for pellet making. This study manufactured seven types of pellets with different additive combinations to evaluate pellet quality characteristics and their relationships. A laboratory-type hammer mill and a pellet mill were used for feedstock preparation and pellet production. Experimental investigations showed that the lignin content increased from 7.0% to 13.1%, which was a primary need for pelletization. Also, the heating value rose from 17.02 to 20.36 MJ/kg. However, the ash content also increased from 7.09% to 16.2%. Results showed that dimension (length and diameter), durability, and tensile strength increased significantly with additives while the fines content decreased. The fines content had an inverse relationship with durability and strength. Wheat straw (60%), together with 10% sawdust (SD), 10% corn starch (CS), 10% bentonite clay (BC), and 10% biochar (BiC), was optimal with good pellet performance (T7). In addition, both the T5 pellets (70% WS, 10% SD, 10% BiC, and 10% BC) and the T6 pellets (70% WS, 10% SD, 10% BiC, and 10% CS) provide suitable quality according to EN plus 2015 standard requirements. The ash content of produced pellet was higher than the recommended value, which suggests that further research onto the alternative additive use for ash reduction is needed

Interactive emulator system to aid clinical practice outcomes for nurses

Clinical practice is a key element of nursing studies programmes. Amongst its aims are familiarisation with medical equipment, appropriate use of clinical reasoning in a ward setting and calculation and delivery of patient medication fluids requirements. The setting for this is typically a simulated ward environment and is structured around group training. While this is cost effective, it does not cater well for minority groups and those wishing to train at their own pace. A number of group dynamic related social issues can also lead to students dominating others within the session. This can result in less than satisfactory learning outcomes for the remainder of the group. Other factors that come into play are the wide age range, social and ethnic backgrounds of the nursing student cohort. Recent Remote Access Nursing Laboratory work has shown a marked improvement in residential school assessment results in areas such as readiness to practice and clinical reasoning levels demonstrated for those students in the trial nursing RAL project. With the aim of further enhancing the effectiveness and at the same time reducing implementation costs an interactive IV pump emulator was developed. Enhancements included guided introductions, provision of additional scaffolding and inbuilt annotated assessments. This paper discusses the techniques used and general implementation of this system and reports on positive results of the conducted trials

Enhancing nursing education with remote access laboratories

Given the vast coverage area and dispersed population centres in which nursing professionals practice in Australia, Remote Access Laboratory (RAL) based learning activities would seem to be an ideal match. However while they are commonplace in engineering faculties; in other disciplines such activities are not widely used. This may well be due to the intricacies of these practicals not being as straightforward and readily reproducible as typical physics or science experiments. In our chosen case, the safe practice of intravenous pump driver operations and related clinical reasoning skills are important components for the training of both registered nurses and nursing students. The aim of this research project is to develop and trial remote access technologies that enable nursing students to test their knowledge, skills, and clinical reasoning with intravenous infusion pump drivers. This has been possible by extending the concept of RAL from a physical and tangible experiment, to more conceptual experimentation in any form conducted remotely. In such a context clinical reasoning becomes possible. This paper discusses a prototype system that has been built with collaborative input from the Faculty of Engineering and Surveying and the Department of Nursing and Midwifery. An initial evaluation with a group of nursing students has been completed to assess if such activities can assist with the training of student nurses. Previous work has identified the need to scaffold learning activities that rely on RAL technology; the key conclusion in this paper is that in the context of nursing this has to be taken a step further. RAL activities here require contextualisation to become an effective learning tool

Student focus groups

Benefits of collecting student feedback on courses, programs, learning experiences, and their perceptions of teaching quality, are well documented in literature. In the higher education system, this feedback is generally collected via student evaluation surveys. During the past few years, the Faculty of Engineering and Surveying (FoES), one of five faculties at USQ, has identified problems of small response rates, possible bias, general questions over data validity, relevance and wording of survey questions, and systems problems such as timeliness of official reports. Due to these problems, the data may not be reliable and the views of those who respond may not be representative of the overall student cohort. It is therefore risky to base management decisions on student satisfaction, teaching quality, and course quality on these data. Clearly, a more robust and reliable method of gathering feedback from students was needed that would provide more confidence in the data. For various reasons it was considered that structured student focus groups might provide such a vehicle

Improving clinical practice outcomes for nurses with an interactive emulator

Historically, nursing students have shown great difficulty in mastering equipment during clinical practice sessions. A typical example is the Intravenous (IV) pump infusion driver. Traditional training methods have relied upon on-campus practical group training sessions. Recent work in this area has demonstrated that Remote Access Laboratories (RAL) can be employed to enhance nursing education by providing access to an IV pump driver learning activity. The prototype closely mimicked the interface and audible feedback of a commonly used IV pump driver; and controlled a peristaltic pump to deliver the prescribed rates and volumes. This project takes this approach a step further and investigates a completely emulated interface in the same RAL environment. The aim is to target five problem areas that were previously identified. These include the screen navigation and data entry of the IV pump driver; and the correct calculation and entry of medication volumes and rates from a standard fluid chart. To address these issues the learning environment was modified to include a guided learning mode, integrated scaffolding resources and facility of self-assessment. This paper discusses implementation and results of a pilot study to evaluate the effectiveness of this approach. Initial results are promising and show a distinct improvement in the practical capability of those students who participated in the trial

Macadamia nutshell biochar for nitrate removal : Effect of biochar preparation and process parameters

Agricultural runoff is a major cause of degradation to freshwater sources. Nitrate is of particular interest, due to the abundant use of nitrogen-based fertilizers in agricultural practices globally. This study investigated the nitrate removal of biochar produced from an agricultural waste product, macadamia nutshell (MBC). Kinetic experiments and structural analyses showed that MBC pyrolsed at 900 degrees C exhibited inferior NO3- removal compared to that pyrolsed at 1000 degrees C, which was subsequently used in the column experiments. Concentrations of 5, 10 and 15 mg/L, with flowrates of 2, 5 and 10 mL/min, were examined over a 360 min treatment time. Detailed statistical analyses were applied using 2(3) factorial design. Nitrate removal was significantly affected by flowrate, concentration and their interactions. The highest nitrate removal capacity of 0.11 mg/g MBC was achieved at a NO3- concentration of 15 mg/L and flowrate of 2 mL/min. The more crystalline structure and rough texture of MBC prepared at 1000 degrees C resulted in higher NO3- removal compared to MBC prepared at 900 degrees C. The operating parameters with the highest NO3- removal were used to study the removal capacity of the column. Breakthrough and exhaustion times of the column were 25 and 330 min respectively. Approximately 92% of the column bed was saturated after exhaustion

Biochar effects on nutrients retention and release of hydroponics growth media

Applying biochar (BC) to broad acre crops is an effective way to sequester carbon while improving soil fertility and reducing nutrient leaching. Adopting a similar approach in a hydroponic environment, BC may enhance nutrient availability and reduce natural fluctuations in the nutrient solution. This study monitored the effect of BC addition to peatmoss growth media with ratios of 0%, 5%, 25% and 50% on pH, electrical conductivity (EC) and macronutrient retention cycle over 15 days using hydroponic nutrient solution controls. Deionised water was used to measure nutrient releases in the closed loop hydroponic system, showing that biochar increased pH level in both retention and release stages. As expected, the pH increased by a maximum of 1.5 units with the highest biochar to growth media ratio due to the natural liming nature of the BC. The EC was also affected, as BC increased in the media EC reduced. With regards to retention of nutrients, BC recovered nitrate, phosphate, calcium and sulphate but did not affect magnesium. Potassium levels increased in solution with increasing BC ratio. In terms of outcomes relevant to global agriculture, the results show that the same level of production can nominally be obtained with the use of around half of the nutrients