Scielo RSS <![CDATA[Journal of Energy in Southern Africa]]> vol. 33 num. 1 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Monitoring the natural recovery of potential induced degradation in poly-crystalline photovoltaic modules</b>]]> Potential induced degradation (PID) is a defect that has a severe effect on the performance of photovoltaic (PV) modules in field conditions. It is caused by leakage currents and the accumulation of sodium ions (Na+) between the anti-reflective coating and the encapsulation. In the experiment reported on here, PID was artificially induced through a PID stress test, where the surface of a poly-crystalline p-ttype module was covered with an aluminium sheet connected to the positive terminal of a high voltage power supply (1000 V), while the short-circuited module terminals was biased to the negative terminal. This stress test was applied to two similar poly-crystalline p-type modules, A and B, for 48 hours and 20 hours respectively. The duration of the stress test determines the degree of PID severity induced. The length of the test resulted in Module A's power decreasing by 88% and Module B's by 40%. Electroluminescence and current-voltage measurements were taken at regular intervals over a period of more than a year to monitor the natural recovery of the modules. These measurements show that the natural recovery of severe PID modules is possible, but slow. After the test period, the maximum power of Module A and Module B had recovered to 63% and 96% of the original level. PID experienced in the field is generally less severe than for the modules in this study, so PID recovery could be achieved by adopting a process of setting affected strings at open-circuit in turns.HIGHLIGHTS: • Natural recovery of PID-affected modules is possible. • Susceptibility of a module to PID is dependent on the bill of materials. • Modules adversely affected by PID may only recover to a limited extent. <![CDATA[<b>Socio-economic factors affecting smallholder farmers' willingness to adopt biodigester technology in South Africa</b>]]> Being energy-autonomous has been suggested as a means of having sustainable energy in South Africa, where about 98% of electricity is derived from coal. Research has shown that biogas produced from animal wastes using a biodigester can be used as a source of renewable energy with the added benefits of a by-product called digestate, which can replace inorganic fertiliser. This study analyses the factors that influence smallholder farmers' willingness to adopt a biodigester technology. It uses a structured questionnaire to acquire data from 80 respondents in Ngaka Modiri Molema District in North West Province, South Africa. The respondents were 30 livestock farmers and 29 farmers practising mixed farming. Five extension officers were also interviewed to establish their level of knowledge about the technology. Descriptive statistics and Fisher's exact test were used to analyse the data. Factors such as gender, years of experience and family size were significant to willingness to adopt a biodigester. Farmers who were male and those with more years of experience were open to the idea, while those with larger families were less open to it, due to financial constraint. Overall, respondents practising mixed farming were more willing to adopt a biodigester than livestock farmers. <![CDATA[<b>Cost-benefit analysis of wind power integration in distribution networks</b>]]> The capacity of power generation note needs to be increased globally, owing to population growth and industrial revolution. The conventional power plant across the world is inadequate to satisfy growing power demand. By optimally sizing and designing the clusters of renewable energy sources such as wind, microgrid operators can economically and environmentally sustainably provide a clean power solution that can increase the supply of electricity. Wind power (WP) generation can be utilised to reduce the stress on the power plants by minimising the peak demands in constrained distribution networks. Benefits of WP include increased energy revenue, increased system reliability, investment deferment, power loss reduction, and environmental pollution reduction. These will strengthen the performance of the power system and bring economic value to society. Moreover, many challenges are considered when integrating WP into the distribution system. These include protection device miscoordination, fundamental changes in the network topology, transmission congestion, bidirectional power flow, and harmonic current injections. In this paper, the economic cost and benefit analysis of optimal integration of WP into the distribution networks is investigated through a multi-objective analytical method. The aim is to see whether investment in the WP project is economically profitable and technically viable in the distribution system. The results obtained from the study can be utilised by power system operators, planners and designers as criteria to use WP for stimulating economic development and industrial revolution and can allow independent power producers to make appropriate investment decisions.HIGHLIGHTS: • The cost-effectiveness of using wind power is proposed. • The cost-benefit of wind power is analysed. • Strategic grid planning can be achieved with the results obtained. • Wind power can be used to improve electricity access. <![CDATA[<b>Using statistical tests to compare the coefficient of performance of air source heat pump water heaters</b>]]> The study compared the coefficient of performance (COP) of two residential types of air source heat pump (ASHP) water heaters using statistical tests. The COPs were determined from the controlled volume of hot water (150, 50 and 100 L) drawn off from each tank at different time of use (morning, afternoon and evening) periods during summer and winter. Power meters, flow meters, and temperature sensors were installed on both types of ASHP water heater to measure the data needed to determine the COPs. The results showed that the mean COPs of the split and integrated type ASHP water heaters were 2.965 and 2.652 for summer and 2.657 and 2.202 for winter. In addition, the p-values of the groups COPs for the split and integrated type ASHP water heaters during winter and summer were 7.09 x 10-24 and 1.01 x 10(11), based on the one-way ANOVA and the Kruskal-Wallis tests. It can be concluded that, despite the year-round performance of both the split and integrated type ASHP water heaters, there is a significant difference in COP at 1% significance level among the four groups. Furthermore, both statistical tests confirmed these outcomes in the comparisons of the mean COPs among the four groups based on the multiple comparison algorithm.HIGHLIGHTS: • One-way ANOVA multiple comparison test was used to verify any significant difference in the COPs among the four groups (classified by season and type of ASHP water heater). • The Kruskal-Wallis multiple comparison test was used to see if any significant difference exists in the COPs among the four groups. • The results demonstrated significant differences in the mean COPs amongst the four groups. • The one-way ANOVA tests and the Kruskal-Wallis tests gave the same statistical outcomes. <![CDATA[<b>Absorbed power density approach for optimal design of heaving point absorber wave energy converter: A case study of Durban sea characteristics</b>]]> This work proposes an approach for the optimal sizing of a cylindrical heaving wave energy converter (WEC). The approach is based on maximising the absorbed power density (APD) of the buoy, with the diameter being the decision variable. Furthermore, two types of buoy shapes were compared to get the best option. The two buoy shapes are the cone cylinder buoy (CCB) and the hemisphere cylinder buoy (HCB). The aim was therefore to determine the best shape and as well as the optimal size of the cylindrical point absorber. To validate the approach, the simulation was performed under Durban (South Africa) sea characteristics of 3.6 m wave significant height and 8.5 s peak period, using the openWECsimulator. The buoy diameter range considered was from 0.5 m to 10 m for both shapes. Simulation results revealed that a diameter of 1 m was the optimal solution for both buoy shapes. Furthermore, the APD method revealed that the HCB was more efficient than the CCB. The power density of the HCB was 1070 W/m², which was almost double the power density of the CCB, while the two shapes present almost the same absorbed power. <![CDATA[<b>Integration of waste heat in thermal desalination technologies: A review</b>]]> Desalination is increasingly becoming a crucial method for providing fresh water globally. However, most of the desalination technologies are energy-intensive and driven by fossil fuels that are contributing to climate change and other environmental problems. In this vein, renewable energy and energy efficiency are promising pillars of sustainable energy production and consumption, and the recovery of waste heat helps to augment the energy efficiency of a system. Based on the temperature (T) of the heat source, waste heat can be classified into three categories: low temperature (T<100°C), medium temperature (100°C<T<300°Q and high temperature (T&gt;300°C). There is scarcity of review work on the integration of waste heat in desalination technologies. In this study, the progress in the utilisation of waste heat to drive thermal desalination processes has been investigated. It is found that 63% of waste heat streams are of low grade, which is still satisfactory for thermal desalination technologies that run on low-temperature heat sources. As of 2018, there was only one known thermal desalination plant driven by waste heat. Lack of data on waste heat, especially in developing countries, has been identified as a major challenge to the advancement of desalination technologies driven by this source of thermal energy. Other constraints are presented and discussed in this paper. <![CDATA[<b>An empirical analysis of the co-benefits of integrating climate change adaptation and mitigation in the Namibian energy sector</b>]]> The Namibian energy sector and other energy sectors across the globe are currently in a rapid transformation era that must respond to climate change, which directly affects energy infrastructure's resilience to the effects of resource scarcities or extreme weather conditions. The energy sector must implement adaptation to guarantee the resilience of vital infrastructure to fulfil its regulatory commitments, which cover the elements of resilience and safety. Through investigating climate change adaptation and mitigation implementation in Namibia, this study validates the existence of these co-benefits where integration is fully observed. It employed a meta-analysis and content analysis to link the observed variables to the most recognised co-benefits. The findings suggest that integration is an efficient way to generate co-benefits that contribute positively to the climate change project. Effective leadership support is one way of realising such integration, either via public-private partnership or energy policy. Namibian energy policy, it is suggested, through voluntary tools and incentives, should create key public-private partnerships and promote management. These recommendations have application beyond the Namibian energy sector, and the lessons learned here could be implemented in scenarios outside of it.