Search results

This paper aims to show that by using air source heat pump (ASHP) water heater in the residential sector, the energy consumption from sanitary hot water production can be reduced by more than 50 per cent. Hence, this study quantitatively and qualitatively confirms that domestic ASHP water heater is a renewable and energy efficient device for sanitary hot water production.

Design and building of a data acquisition system comprises a data logger, power meters, flow meters, temperature sensors, ambient and relative humidity sensor and an electronic input pulse adapter to monitor the ASHP water heater performance. All the sensors are accommodated by the U30-NRC data logger. The temperature sensors are installed on the inlet pipe containing a flow meter and the outlet pipe of the ASHP unit, the vicinity of both evaporator and expel cold air. An additional temperature sensor and a flow meter that cater for hot water drawn off measurements are incorporated into the data acquisition system (DAS).

The result from a specific monitoring split type ASHP water heater gives an average daily coefficient of performance (COP) of 2.36 and the total electrical energy of 4.15 kWh, and volume of hot water drawn off was 273 L. These results were influenced by ambient temperature and relative humidity.

The cost involved in purchasing the entire sensors and data logger limits the number and categories of ASHP water heaters whose performance were going to be monitored. Pressure sensors were excluded in the data acquisition system.

The data acquisition system can easily be designed and the logger can also be easily programed. Hence, no high technical or computer skills are needed to install the DAS and to be able to read out the results.

Hence, the data acquisition system can be installed on the entire domestic Eskom roll out air source heat pump water heaters to effectively determine the coefficient of performance and demand reductions.

This DAS is the first of its kind to be built in South Africa to be used to determine the performance of an ASHP water heater with high accuracy and precision. DAS is also robust.

The purpose of this paper is to develop a cyclone with an internal electric field to capture dust and fine carbon particles with less than 5 μm diameter.

The cyclone collection efficiency model described by Cooper and Alley was used to design a conventional cyclone, which was later modified by introduction of the solenoid around it to introduce an electric field. The cyclone design performance was later established using ferrosilicon powder with less than 5 μm diameter.

The cyclone was found to have a particle collection efficiency of around 25 per cent for ferrosilicon powder before the introduction of the solenoid; the introduction of the solenoid increased the particle collection efficiency to around 50 per cent and the charging of the solenoid further increased the collection efficiency to 85 per cent at 2 kV DC and 97 per cent at 3 kV DC. When the cyclone was placed back on the gasifier system and supplied with 2 kV DC, it collected up to 270 g of fine carbon particles within 150 min of operation.

The major drawback was that the highest particle collection efficiency for the cyclone could only be achieved at very high voltage (3 kV) but this could not be supplied when the cyclone was back in the gasifier system due to air ionization that results in the corona effect.

The collection of very fine particles (less than 5 μm diameter) in hot gas streams is always a challenge, particularly in biomass gasifier systems. This resulted in a high cost of gas purification or initial investments in downstream processes. The developed cyclone could cut down this expenditure since most of the particles will not go beyond the cyclone.

Electrostatics has been applied in the development of gas cleaning devices, however most of these devices tend to be too cumbersome. The developed cyclone is based on the conventional design, which is less complicated and cheap to manufacture.

The purpose of this paper is to design and implement a directly cooled photovoltaic thermal (PV/T) hybrid system.

The research design subjects, instruments and methods that were used to collect data are as detailed in the paper. Two polycrystalline photovoltaic (PV) modules were used in this study.

The directly water-cooled PV module (PV/T) was found to operate better as compared to a naturally cooled module for the first three months. The PV/T initially operated at a higher electrical efficiency for 87 per cent of the day. The monthly energy-saving efficiency of the PV/T was found to be approximately 61 per cent, while the solar utilisation of the naturally cooled PV module M1 was found to be 8.79 per cent and that of M2 was 47.93 per cent.

The major limitation was the continued drop in efficiency after the first three months of the PV/T placed outdoors. The fall in the efficiency was attributed to water ingress.

Direct water cooling of PV modules is possible, only that a better sealing is needed to prevent water ingress.

PV air cooling has been researched on. Use of water as a cooling medium has been carried out using serpentine pipes or riser tube, and no direct water cooling on the back of the module has been researched on.

As a response to the COVID-19 pandemic, both educators and students adapted to course delivery modes no longer centered on in-person interactions. Resiliency and self-regulation are key to success in online contexts, but the rapid transition to remote learning left many students without the necessary support to develop these skills. Much of the existing literature on self-regulation and resiliency focuses on cognitive processes and strategies such as goal orientation, time management, and mindset. However, the added stress and trauma of learning in the context of a global pandemic highlighted the many other factors relevant to students’ development of these skills. Drawing from the literature, the authors explore evidence-informed teaching practices to foster self-regulation and resiliency, highlight the power and privilege of being able to be resilient, advocate for the development of pedagogies of kindness, and emphasize the “how” of implementing techniques to best support students. The authors provide evidence-informed suggestions with the goal of assisting instructors and students during times of high stress, while acknowledging their limitations in addressing structural inequalities highlighted by the COVID-19 pandemic. Nonetheless, the authors argue that evidence-informed techniques and compassionate pedagogies adopted during a period of upheaval remain applicable to future in-person and online pedagogies.

The purpose of this study was to build and develop mathematical models correlating ambient conditions and electrical energy to the coefficient of performance (COP) of an air-source heat pump (ASHP) water heater. This study also aimed to design a simulation application to compute the COP under different heating up scenarios, and to calculate the mean significant difference under the specified scenarios by using a statistical method.

A data acquisition system was designed with respect to the required sensors and data loggers on the basis of the experimental setup. The two critical scenarios (with hot water draws and without hot water draws) during the heating up cycles were analyzed. Both mathematical models and the simulation application were developed using the analyzed data.

The predictors showed a direct linear relationship to the COP under the no successive hot water draws scenario, while they exhibited a linear relationship with a negative gradient to the COP under the simultaneous draws scenario. Both scenarios showed the ambient conditions to be the primary factor, and the weight of importance of the contribution to the COP was five times more in the scenario of simultaneous hot water draws than in the other scenario. The average COP of the ASHP water heater was better during a heating cycle with simultaneous hot water draws but demonstrated no mean significant difference from the other scenario.

There was a need to include other prediction parameters such as air speed, difference in condenser temperature and difference in compressor temperature, which could help improve model accuracy. However, these were excluded because of insufficient funding for the purchase of additional temperature sensors and an air speed transducer.

The research was conducted in a normal middle-income family home, and all the results were obtained from the collected data from the data acquisition system. Moreover, the experiment was very feasible because the conduction of the study did not interfere with the activities of the house, as occupants were able to carry out their activities as usual.

This paper attempts to justify the system efficiency under different heating up scenarios. Based on the mathematical model, the performance of the system could be determined all year round and the payback period could be easily evaluated. Finally, from the study, homeowners could see the value of the efficiency of the technology, as they could easily compute its performance on the basis of the ambient conditions at their location.

This is the first research on the mathematical modeling of the COP of an ASHP water heater using ambient conditions and electrical energy as the predictors and by using surface fitting multi-linear regression. Further, the novelty is the design of the simulation application for a Simulink environment to compute the performance from real-time data.

The aim of this research is to build a low‐cost gas and temperature profiling system for data acquisition at a biomass gasifier.

A gas and temperature profiling system was developed from NDIR sensors, Pd/Ni sensor, a number of type K thermocouples and a data logger interfaced to a computer.

The results obtained using the system were in agreement with the results obtained using a gas chromatograph for gasses. The temperature recorded during the testing also followed the expected temperature of the gasifier used.

The lifetime of the developed system depends on the lifetime of the sensors used. NDIR sensors have a lifetime of three years working on a continuous basis and the Pd/Ni sensor has a lifetime of ten years. Replacement of the Pd/Ni sensor after ten years is not a problem as the payback period of biomass gasifier systems is around eight to ten years.

The major implication for this research was that low‐cost gas and temperature measuring systems could be developed. These could be useful particularly for PhD students and other researchers who need to get onsite data on gas and temperature profiles at a gasifier system for a period of three years.

Biomass gasifier technologies can be used to provide power in rural areas that are outside the national utility grid but endowed with biomass resources. The provision of electricity to these communities could solve social challenges such as exposure to smoke in open fire normally used by rural women for cooking. The developed data acquisition system is therefore necessary to conduct research on gasification.

The findings of this paper are of importance to researchers who need online data but do not have funding to purchase bulky and expensive equipment's for gas analysis at biomass gasifier systems.

The alternative food markets are growing and despite the evidences of heterogeneity and of organic food consumers’ special features, little has been done to develop a scale to measure loyalty to this market. The purpose of this paper is to propose and validate a scale based on consumers’ loyalty literature and on the particular features of the organic market.

Data from 604 consumers were obtained through a web-based survey, which was used to analyze the structural equation in the AMOS software, in order to validate the proposed scale model.

A one-dimensional validated scale consisting of eight questions and showing high composite reliability level (0.95) was used to measure consumer loyalty to organic food. The herein used sample presented mean True Organic Loyal (4.36) and standard deviation (0.62); these values depict Brazilians high loyalty to this food type.

The research was conducted and validated in Brazil and it can be replicated within the country as well as be transculturally validated.

The main contribution of the current study is the development and validation of a scale named scale of consumer loyalty for organic food. The suggested interpretation ranges from non-loyal to true organic loyal consumers and it helps understanding organic food consumers’ behavior. This research took under consideration consumers of any sort of organic food as well as consumers of regular food markets (farmer’s markets, supermarkets, collective groups, shops and internet).