Performance comparison of the residential types of air source heat pump water heaters in South Africa due to the refrigerant thermo-physical properties
- Authors: Sikhonza, Mandlenkosi
- Date: 2018
- Subjects: Heat pumps Water heaters
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/9275 , vital:34317
- Description: Globally hot water heating contributes enormously to the increase in energy consumption in the residential sector. Coal being a fossil fuel and non-renewable source of energy remains the major source used for electricity generation. The burning of coal is the primary cause of CO2 emission into the environment which causes climate change and global warming. Energy efficiency and renewable energy technologies were employed as one of the alternative ways of reducing global warming. In most residential areas in South Africa, the water heating generates 30 -50percent of the monthly electricity bill (Zhang and Huan, 2013). In this light, residential load management (RLM) is a significant part of the load management programme of Eskom’s overall demand side management strategy. Through RLM, the electricity load is being transferred from peak times to off times by switching the geysers during peak hours because geysers consume more electricity and contribute significantly to the national grid constraint problem (Eskom, 2012).
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- Authors: Sikhonza, Mandlenkosi
- Date: 2018
- Subjects: Heat pumps Water heaters
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/9275 , vital:34317
- Description: Globally hot water heating contributes enormously to the increase in energy consumption in the residential sector. Coal being a fossil fuel and non-renewable source of energy remains the major source used for electricity generation. The burning of coal is the primary cause of CO2 emission into the environment which causes climate change and global warming. Energy efficiency and renewable energy technologies were employed as one of the alternative ways of reducing global warming. In most residential areas in South Africa, the water heating generates 30 -50percent of the monthly electricity bill (Zhang and Huan, 2013). In this light, residential load management (RLM) is a significant part of the load management programme of Eskom’s overall demand side management strategy. Through RLM, the electricity load is being transferred from peak times to off times by switching the geysers during peak hours because geysers consume more electricity and contribute significantly to the national grid constraint problem (Eskom, 2012).
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Computational design of a smart and efficient control system for a residential air source heat pump water heater
- Authors: Yongoua Nana Joel
- Date: 2017
- Subjects: Heat pumps -- Specifications Water heaters Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/4582 , vital:28435
- Description: An air source heat pump (ASHP) water heater is a renewable and energy efficient hot water heating technology. ASHP water heaters are fast gaining maturity in the South African market and in Africa at large due to their low energy consumption (about 67 percent lower than conventional geysers), relatively low installation and operation cost, their environmental friendly nature and possibly the ease to retrofit with the old inefficient technologies. Furthermore, ASHP water heaters make use of some of the most recent advancement in refrigeration technologies enhancing their performance through a wide range of weather conditions. However, residential ASHP water heaters which come at the tail of a series of highly sophisticated models still harbour primitive control designs. One of such control system is the intermittent (on/off) control whereby the ASHP unit responds to a temperature differential threshold rather than instantaneous temperature fluctuations. Unfortunately, this control method contributes to a rapid deterioration of the compressor and other actuators due to high starting current during transient states and partial loading. Capacity control is a better alterative as it offers a more reliable system’s performance as well as a better protection for the system components. However, the drawbacks of implementing such a technology on residential ASHP water heaters is the initial purchasing cost. We use a systematic approach in this research to circumvent the purchasing cost and complete redesign hysteresis. The first step was centered around a hypothetical analysis of the performance of the heat exchangers in a bid to uncover the weakness during the operation of a residential ASHP water heater. It was observed that at ambient temperatures above 22°C notably during summer and winter afternoons, water only harnesses about 75 percent of the total heat rejected. Furthermore, the actuators keep doing work for about 15-20 minutes even after the heat transfer process has ceased completely. Following these observations, a sequential flow algorithm was developed aimed at matching the consumption point to weather variables like ambient temperature and secondly to most efficiently synchronize actuator components for a better energy management. This novel control method can save up to 58 percent of energy compared to the conventional on/off method during summer afternoons and averagely 20 percent during the rest of the day. It also has the merit to be cost effective as it barely requires no component retrofitting.
- Full Text:
- Authors: Yongoua Nana Joel
- Date: 2017
- Subjects: Heat pumps -- Specifications Water heaters Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/4582 , vital:28435
- Description: An air source heat pump (ASHP) water heater is a renewable and energy efficient hot water heating technology. ASHP water heaters are fast gaining maturity in the South African market and in Africa at large due to their low energy consumption (about 67 percent lower than conventional geysers), relatively low installation and operation cost, their environmental friendly nature and possibly the ease to retrofit with the old inefficient technologies. Furthermore, ASHP water heaters make use of some of the most recent advancement in refrigeration technologies enhancing their performance through a wide range of weather conditions. However, residential ASHP water heaters which come at the tail of a series of highly sophisticated models still harbour primitive control designs. One of such control system is the intermittent (on/off) control whereby the ASHP unit responds to a temperature differential threshold rather than instantaneous temperature fluctuations. Unfortunately, this control method contributes to a rapid deterioration of the compressor and other actuators due to high starting current during transient states and partial loading. Capacity control is a better alterative as it offers a more reliable system’s performance as well as a better protection for the system components. However, the drawbacks of implementing such a technology on residential ASHP water heaters is the initial purchasing cost. We use a systematic approach in this research to circumvent the purchasing cost and complete redesign hysteresis. The first step was centered around a hypothetical analysis of the performance of the heat exchangers in a bid to uncover the weakness during the operation of a residential ASHP water heater. It was observed that at ambient temperatures above 22°C notably during summer and winter afternoons, water only harnesses about 75 percent of the total heat rejected. Furthermore, the actuators keep doing work for about 15-20 minutes even after the heat transfer process has ceased completely. Following these observations, a sequential flow algorithm was developed aimed at matching the consumption point to weather variables like ambient temperature and secondly to most efficiently synchronize actuator components for a better energy management. This novel control method can save up to 58 percent of energy compared to the conventional on/off method during summer afternoons and averagely 20 percent during the rest of the day. It also has the merit to be cost effective as it barely requires no component retrofitting.
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Thermodynamic and electrical performance monitoring of a domestic split-type air conditioner and development of a simulation based R22 permanent replacement
- Authors: Bantan, Mafor Glory
- Date: 2017
- Subjects: Air conditioning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/4857 , vital:28537
- Description: The difficulty that exists in accurately monitoring the performance of air conditioners has made performance prediction an arduous task. Nevertheless, the performance still needs to be monitored and predicted as it helps solve a lot of problems resulting from this technology like effect of the technology on the grid, energy consumption, water utilisation and GHGs emission. With the introduction of regression modelling as a means of system monitoring and prediction some years ago, the accuracy was still a call for concern. It is worth realising that increasing the number of predictors will enhance this method’s accuracy. As such, this document intends to increase the accuracy of this method’s monitoring and predicting ability by increasing the number of predictors to cut across system thermal, environmental and human behavioural variation. These predictors experimentally gotten are used to build an environ-behavioural model that monitors the coefficient of performance and energy consumption of a domestic split-type air conditioner with higher accuracy. Refrigerants have undergone evolution in the past decades in a bid to come up with a refrigerant that has zero ODP, lower – than – R22 GWP and much better than R22 thermodynamic performance. No pure refrigerant has been found to possess these qualities as such mixtures or blends are the best shot at the moment. R410A could stand the test of time to be the long term R22 replacement but for the fact that besides R410A’s higher GWP than that of R22, the former’s system performance is lower than that of the latter’s due to the lower thermodynamic performance of the former. This means the search continues. In this document, a combination of carefully chosen refrigerant components are carefully blended to come up with a simulation based R22 long term replacement, which will be referred to in this document as BTEP.
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- Authors: Bantan, Mafor Glory
- Date: 2017
- Subjects: Air conditioning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/4857 , vital:28537
- Description: The difficulty that exists in accurately monitoring the performance of air conditioners has made performance prediction an arduous task. Nevertheless, the performance still needs to be monitored and predicted as it helps solve a lot of problems resulting from this technology like effect of the technology on the grid, energy consumption, water utilisation and GHGs emission. With the introduction of regression modelling as a means of system monitoring and prediction some years ago, the accuracy was still a call for concern. It is worth realising that increasing the number of predictors will enhance this method’s accuracy. As such, this document intends to increase the accuracy of this method’s monitoring and predicting ability by increasing the number of predictors to cut across system thermal, environmental and human behavioural variation. These predictors experimentally gotten are used to build an environ-behavioural model that monitors the coefficient of performance and energy consumption of a domestic split-type air conditioner with higher accuracy. Refrigerants have undergone evolution in the past decades in a bid to come up with a refrigerant that has zero ODP, lower – than – R22 GWP and much better than R22 thermodynamic performance. No pure refrigerant has been found to possess these qualities as such mixtures or blends are the best shot at the moment. R410A could stand the test of time to be the long term R22 replacement but for the fact that besides R410A’s higher GWP than that of R22, the former’s system performance is lower than that of the latter’s due to the lower thermodynamic performance of the former. This means the search continues. In this document, a combination of carefully chosen refrigerant components are carefully blended to come up with a simulation based R22 long term replacement, which will be referred to in this document as BTEP.
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Multi linear regression-based modeling and performance monitoring of flat plate solar collector outlet temperature in Alice, South Africa
- Authors: Ndlovu, Nothando
- Date: 2015
- Subjects: Solar collectors Solar water heaters
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12676 , vital:39298
- Description: In a period of rapidly increasing energy demand, the exploitation of abundantly available solar energy is imperative. Temperate climates like South Africa show good potential for utilizing solar-driven technologies such as solar water heaters. These systems offer an attractive alternative over conventional water geysers as a means to supply hot water for residential use. In South Africa, the solar water heater industry is growing rapidly as the government offers incentives manufactures and consumers. This necessitates the determination of performance of these systems through experimental analysis as well as performance prediction. This study evaluated the summer and winter performance of a flat plate, thermosyphon solar water heater under climatic conditions encountered in Alice, South Africa by considering the collector outlet temperature. The performance and weather data obtained were used to develop a multi linear regression (MLR) model for each season. MLR is a simple and easily applicable modelling approach which uses a set of input and output data to determine the model coefficients of a linear relation of two or more variables. The collector outlet temperature was correlated with solar radiation, ambient temperature, relative humidity, and collector inlet temperature since these variables have a direct impact on the collector temperature rise. Results from the performance showed that the collector performs well, attaining temperatures up to 87.2oC during the summer season and 70oC during winter season. The summer and winter percentage mean absolute error for the whole monitoring period were 4.07 percent and 6.2 percent respectively which indicate that MLR can be successfully applied to predict collector outlet temperatures in both seasons.
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- Authors: Ndlovu, Nothando
- Date: 2015
- Subjects: Solar collectors Solar water heaters
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12676 , vital:39298
- Description: In a period of rapidly increasing energy demand, the exploitation of abundantly available solar energy is imperative. Temperate climates like South Africa show good potential for utilizing solar-driven technologies such as solar water heaters. These systems offer an attractive alternative over conventional water geysers as a means to supply hot water for residential use. In South Africa, the solar water heater industry is growing rapidly as the government offers incentives manufactures and consumers. This necessitates the determination of performance of these systems through experimental analysis as well as performance prediction. This study evaluated the summer and winter performance of a flat plate, thermosyphon solar water heater under climatic conditions encountered in Alice, South Africa by considering the collector outlet temperature. The performance and weather data obtained were used to develop a multi linear regression (MLR) model for each season. MLR is a simple and easily applicable modelling approach which uses a set of input and output data to determine the model coefficients of a linear relation of two or more variables. The collector outlet temperature was correlated with solar radiation, ambient temperature, relative humidity, and collector inlet temperature since these variables have a direct impact on the collector temperature rise. Results from the performance showed that the collector performs well, attaining temperatures up to 87.2oC during the summer season and 70oC during winter season. The summer and winter percentage mean absolute error for the whole monitoring period were 4.07 percent and 6.2 percent respectively which indicate that MLR can be successfully applied to predict collector outlet temperatures in both seasons.
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