Showing papers by "Kanzumba Kusakana published in 2022"

Optimal planning of Renewable energy generators in modern power grid for enhanced system inertia

Abstract: In recent times renewable energy sources have become an integral part of the modern power grid. As a result, the overall system inertia of the grid has been reduced, thus leading to frequency instability issues such as fast rate of change of frequency. Thus, to compensate for the declining inertia, it is important to carefully select renewable energy generators (REGs) and energy storage systems (ESS) in order to ensure the stability of the power grid, while also controlling greenhouse gases emissions in line with environmental standards. Therefore, this paper proposes an optimal planning model of REGs and ESS, considering the inertia requirement of the grid. The objective function is formulated to minimize the cost of operation, emissions, and investment in new REGs and energy storage units while maximizing the system inertia. The model was developed as a mixed integer linear programming problem and solved using CPLEX solver in GAMS. Finally, the model was validated using a modified IEEE 9-bus system and compared under three scenarios. The results show that in scenario 3 where system inertia is considered in the presence of REGs and ESS, higher system inertia of 8.776 s was achieved at minimal emission and cost, which justifies the aim of the study.

Optimal energy management of a solar-assisted heat pump water heating system with a storage system

Abstract: Water heating is the fourth largest energy consumer in the commercial building sector, accounting for >40 % of the energy consumed in South Africa. Traditional electric storage tank water heaters (ESTWHs) have been the most frequently used systems in the past, owing to their low electricity costs and implementation. It was low enough at that time that energy costs were not considered. These systems have grown increasingly hostile to consumers as power prices have risen, particularly to the undesirable high morning and afternoon peaks. The indirect-expansion solar-assisted heat pump water heater (IDX-SAHPWH), for the commercial sector, to reduce energy consumption of hot water production while maintaining the users' thermal comfort level, has been proposed in this paper. The system is operated under an optimal energy control scheme, integrated with the load shifting by time-of-use (TOU) pricing plan. The comparison of the performance of the proposed optimally controlled system and the electric storage tank water heater (ESTWH) was performed through the simulation approach using the Solving Constraint Integer Programs (SCIP) solver, in the MATLAB interface optimization toolbox. The simulations reveal that the proposed system operates during off-peak hours, when power prices are lower, as compared to ESTWH system. The techno-economic analysis was conducted and presented for a project lifespan of 20 years. The proposed optimally controlled system demonstrates the cost savings obtained from the winter and summer seasons, as well as annual, as 76.0 %, 75.6 % and 75.8 %, respectively. The break-even point of the project is during the 9th month of the first year of the project, with a possible savings of 71.5 % at the end of the project's lifetime.

Using statistical tests to compare the coefficient of performance of air source heat pump water heaters

Abstract: 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.

Energy cost minimization of a multifarious water heating system with energy recovery: A case of a healthcare institution

Abstract: The energy usage intensity of healthcare institutions is extensive. The recorded relative typical energy consumption of hospitals has been noted to be in the range of 43 to 93 kWh/bed/day. Currently, with the global COVID 19 pandemic, the overall energy consumption of these hospitals has proportionally increased with these higher patient occupancy rates. The demand for hot water is directly proportional to occupancy rates and contributes to a large proportion of the energy consumed. Reducing the energy and associated costs of water heating processes may prove highly beneficial to the currently severely overstrained healthcare sector. In this paper the operation of a multifarious water heating system with energy recovery was optimized in order to minimize the grid energy costs based on the ToU tariff and maximum demand charges from the utility, while the required hot water temperature was maintained. A life cycle cost analysis between two baseline systems, consisting of the multifarious water heating system with and without energy recovery was compared to the optimal control approach. The results indicate that the energy recovery system with optimal control in 5.3 years. Retrospectively, the proposed initiatives may result in a potential saving of 68.23%, over a 20 year project lifetime.

Techno-economic analysis of marine outfalls wastewater discharge for electricity generation

Abstract: In this study, the use of pumping pressure from wastewater marine outfall installations is investigated for electricity generation purposes through a hydropower system. The components of the system are mathematically modelled and simulated using Matlab for the of Green Point marine outfall in Cape Town, South Africa. A techno-economic analysis is performed to assess the performance of the system using indicators such as the simple payback period, the lifecycle cost, and the Breakeven point analysis. For the proposed case study, the result show that a 16kW hydropower system can adequacy generate electricity. The proposed system can save 14,39 % if this energy is compared to the pumping energy requirements of the selected marine outfall. This will lead to a Breakeven point of 5,3 years when using the system without hydropower as baseline.