Showing papers by "Kanzumba Kusakana published in 2020"

Optimal peer-to-peer energy management between grid-connected prosumers with battery storage and photovoltaic systems

Abstract: This paper proposes a model for the optimal Peer-to-Peer energy sharing of grid-connected Prosumers. Current models within available literature do not include the constraint which forbid small renewable energy producers to share their excess power through the national grids; this leads to prosumers dissipating their excess power generated or using costly energy storage systems. Additionally, most of these models look at the savings made by the Peer-to-Peer community, without computing the cost reduction or benefit of each prosumer taken individually. Thus, these models are not suitable or directly applicable to many countries such as South Africa. For these reasons, the main aim of this paper is to develop a Peer-to-Peer energy sharing model that considers the above mentioned gaps. The proposed system consists of two prosumers; a residential prosumer that employs a roof mounted photovoltaic system with energy storage capabilities, and commercial prosumer with a dual-tracking photovoltaic system. The prosumers are connected to each other by power lines for P2P operation. The developed model minimizes both prosumers’ operation costs by maximizing the use of the power from the renewable energy sources; optimally managing the internal power sharing between the prosumers; and minimizing the use of the electrical utility operating with the Time-of-Use rate. The study uses the dissimilarity and complementarity of the load patterns in the South African residential and commercial energy sectors as an asset to implement the Peer-to-Peer energy sharing between the prosumers operating in these two sectors. Using a case study in South Africa, the results have demonstrated that, as compare to using the grid as sole power source, the residential prosumer can achieve a total daily cost reduction of 62.71% in summer and 68.99% in winter; while the commercial can achieve 81.31% and 31.69% in winter. For a 20 years’ project, using the grid as baseline for the comparison, the lifecycle cost analysis have projected the residential prosumer to break-even after 16.35 years and save 19.5%; while the commercial prosumer can break-even after 5.3 years and save 55.2%. Moreover, this study shows the ability of the developed model to simulate systems with different components, demands, resources as well as costs. The model developed in this study may assist researchers and engineers interested in the optimal operation of prosumers in Peer-to-Peer energy sharing schemes.

Improving Energy Efficiency of Thermal Processes in Healthcare Institutions: A Review on the Latest Sustainable Energy Management Strategies

Abstract: Healthcare institutions consume large amounts of energy, ranking the second highest energy-intensive buildings in the commercial sector. Within developed countries, the energy consumption of healthcare institutions may account for up to 18% of the overall energy usage in commercial sectors. Within developing countries, such as South Africa, the energy consumption of healthcare institutions is observed to be a close second to the food service sector. Energy consumption of healthcare institutions per bed typically range from 43–92 kWh per day. In this paper, the largest energy consumers in South African healthcare institutions are identified and appropriate energy-efficiency (EE) initiatives are proposed, in terms of performance, operation, equipment and technology efficiency (POET). Two main thermal energy consumers are identified as heating, ventilation and air conditioning (HVAC) and water-heating systems. These systems are critical to patient health and may be classified as non-deferrable loads. Therefore, several initiatives are suggested to improve the energy efficiency and demand-side management capability of these systems. These initiatives are subdivided into different levels: the conceptual level, active level, technical and further improvement level, as defined in the POET framework. At each level, energy-efficiency initiatives are introduced based on potential energy savings and the effort required to achieve these savings. In addition, model predictive control (MPC) approaches are discussed and reviewed as part of the further improvement section. Average possible energy savings ranged from 50%–70% at the conceptual level, while energy savings of 15%–30% may be expected for energy-efficiency initiatives at the active level. EE activities at the technical level and the further improvement level may result in savings of 50%–70% and 5%–10%, respectively.

Microgrids control strategies: A survey of available literature

Abstract: The implementation of microgrid (MG) could offer significant advantages to an ever-increasing demand for energy. Microgrid control is therefore the key technology for implementing the hybrid renewable energy system (HRES) in practice. In the near future, energy system integration based on distributed resources is the most promising improved microgrid technology in islanded or grid-connected mode in the world. In addition, the stability control of the microgrid network has become more complicated due to the penetration of distributed energy sources (DESs) into the power system and the generation of electricity. The paper provides a brief overview of microgrid prototype systems, microgrid controls, operating modes and multi-DER microgrid types built into a hybrid system, which introduces a number of strategies or techniques for managing remote rural application prototypes in an isolated or grid-connected system. More research would be collected to describe recent development studies aimed at improving the optimum operating concept of microgrid controllers for stand-alone, hybrid or grid-connected systems for real-time implementation by either hierarchical control or distributed control for a reliable and optimal energy management system. However, hierarchical control was found to be more appropriate for large microgrids with multiple types of distributed energy resources (DERs) compared to distributed control, particularly when combined with energy storage systems (ESSs) in isolated mode.

Model validation and economic dispatch of a dual axis pv tracking system connected to energy storage with grid connection: A case of a healthcare institution in South Africa

Abstract: Healthcare institutions, ranks the second highest energy intensive buildings in the commercial sector, with daily energy consumption ranging from 43 to 92 kWh per bed. Energy management in this sector may prove difficult due to the demand's critical and non-deferrable nature. Therefore, in this paper, a validated optimal power dispatch model of a proposed hybrid energy system connected to a healthcare institution is developed. The healthcare institution considered in this study, which will remain anonymous, 1 is subjected to Time-of-Use (ToU) tariffs and maximum demand charges and is considering the implementation of renewable energy technologies to reduce energy costs. Consequently, given the geographical location of the building, a system consisting of a photovoltaic tracking system with a battery bank and grid connection supplying the load is proposed and modelled. The aim is to optimize the power flow between the hybrid system and battery in order to minimize the grid energy costs based on the ToU tariff while reducing the maximum demand charges from the utility. Annual potential cost savings of up to 40.9% were attained, while a projected break-even point of 7.1 years is noted with the proposed optimally controlled system as compared to the load exclusively supplied by the grid.

Optimal Power Dispatch of a Grid-Connected Photovoltaic with Groundwater Pumped-Hydro Storage System Supplying a Farmhouse

Abstract: In developing countries, electricity supply remains a challenge for commercial farmers. This is due to their geographical location or distance with reference to the grid. However, renewable energy sources may be a great alternative for onsite electricity generation. Underground pumped-hydro system is a promising innovation technology with power generation potential for remote located farms, with adequate availability of underground water resource. This paper proposes an optimal energy management model of a grid-connected solar photovoltaic (PV) underground pumped-hydro storage (UPHS) system, for commercial farming in arid areas. The model allows the optimal utilization of the proposed PV-UPHS through open wells (borehole). The objective is to reduce the grid electricity cost for farming activities under variable time-of-use (TOU) electricity prices. The optimization problem is solved using Linprog solver as available in the MATLAB toolbox. Based on the results, the proposed PV-UPHS system is effective in minimizing the grid consumption costs by 32.4 percent during high demand winter season. Hence, more savings may be achieved during summer season due to higher solar resource, low grid energy cost as well as low load demand.

POET Concept for Improving Electrical and Thermal Efficiency of Main Equipment in a Residential Energy Hub

Abstract: In this paper, the largest energy consuming processes in residential buildings are identified and a comprehensive review was conducted using an effective energy management outline to conserve energy, such as the performance, operation, equipment, technology (POET) energy efficiency concept. The two largest energy consumers are identified as space heating (SH) and space cooling (SC), and water heating (WH), where various initiatives are suggested to improve the energy efficiency of these systems. These initiatives are broken up into four levels, known as the conceptual level, active level, technical level and engineering level. At each level, initiatives are introduced based on ease of implementation related to reward. In addition, at the technical level, new supplementary renewable energy equipment such as solar photovoltaic (PV) modules, proton exchange membrane (PEM) electrolyser, hydrogen storage vessel and PEM fuel cell are selected. At the engineering the supplementary renewable energy plays a vital role with demand response, supporting DSM applied to the air to air heat pump and air to water heat pump.

Design of a Cost optimized Hybrid Renewable Energy system for Impressed Current Cathodic Protection

Abstract: This paper investigates the possibility of using hybrid Photovoltaic-Wind renewable energy systems as primary sources of energy to supply Cathodic Protection systems (CP). For this purpose, Umgeni Water Reservoir 2 TRU protecting the pipeline from Hazelmere to Ndwedwe was selected as a pilot site to implement this study. The selected site has adequate solar and wind energy resources. Three different possible options including a hybrid Photovoltaic-Wind, a pure Photovoltaic and a pure Wind energy system were designed to compare and evaluate their technical performance, economics and environmental impact. Simulations using HOMER are performed to determine the Initial Capital, the Total Net Present Cost (NPC), the levilized Cost of Energy (COE) as well as the system Capacity Shortage of the different supply options. The selection criteria include the financial viability over the life period of the project. The results from simulations showed that a cost-effective hybrid of WT-PV could be implemented for supplying CP units, while proving a reasonable COE.

Energy savings configuration for a water-pumping system

Abstract: Pump theory is an interdisciplinary branch in water catchment/purification systems. The main determinant of the selling price of potable water to consumers is the amount of energy utilized when pumping the water from one area to another. These studies propose a water-pump configuration that decreases the energy consumption. The configuration involved an air-compressor that generates air-pressure; the air-pressure is used to supply a pneumatic actuator that converts chemical energy to mechanical energy. The mechanical force that exists at the pneumatic actuator piston is coupled to the piston of a hydraulic actuator to produce the mechanical stroke in the cylinder of the hydraulic actuator. Applying mechanical force at the hydraulic cylinder, the pumping of water from the water-catchment to a watertank/reservoir is achieved. Using their compress-air properties, high force realized at the actuator will allows for an optimal output of the system components. This paper highlights the benefits of fluid dynamics in water-pumping system configuration that range from better energy savings and a robust pumping arrangement.

Sizing and Operation Control of a Grid-Interactive Photovoltaic-Battery-Diesel System for Commercial Buildings

Abstract: The increasing installations of renewable hybrid energy systems in commercial buildings require system sizing to ensure that the designed hybrid system will meet the load demand of a targeted commercial building with minimum life cycle cost. In the commercial sector, photovoltaic renewable is preferred because both its generation and consumption take place during the day. Optimal sizing techniques are required for designing reliable and economical hybrid energy systems. This paper presents optimal sizing of grid-connected hybrid photovoltaic-battery-diesel energy system that meets the load demand of a targeted commercial building with minimum life cycle cost using HOMER software. For the proposed hybrid system, results indicate that 18 kW photovoltaic-6 batteries-15 kW inverter provides the economic system while load following dispatch strategy gives a life cycle cost of $85195 that is lower than $86847 using cycle charging alternative.

Qualitative Methodology for comparison of Performance of Air Source Heat Pump Water Heaters

Abstract: This paper presents a statistical comparison of the electrical energy consumed due to the operation of two residential types of air source heat pump (ASHP) water heaters. The study focused on the determination of the electrical energies consumed and coefficient of performance (COP), by a 1.2 kW split type ASHP without an electric backup and a 0.9 kW integrated type with an auxiliary resistance element of 0.5 kW and both tank size was 150 L. The COPs and the electrical energies consumed were determined from the controlled volume of hot water (150, 50 and 100 L) drawn from each tank at different time of use (morning, afternoon and evening) periods for both the summer and winter seasons. Power meters, flow meters, and temperature sensors were installed on both types of ASHP water heaters to measure the data needed to determine the electrical energies consumed, the COPs and the thermal energies gained. The results depicted that the mean month-day electrical energy consumed by the split and integrated type ASHP water heaters in summer and winter periods was 1.24 and 1.35 kWh, and 1.56 and 1.89 kWh, respectively. Lastly, the p-value from the one-way ANOVA and the Kruskal-Wallis tests for the electrical energies consumed among the four groups was 1.63 x 10-5 and 1.60 x 10-3, respectively. It can be concluded that, despite the favourable seasonal performance of both the split and integrated type ASHP water heaters, there exists a significant difference in the electrical energies consumed at 1% significance level among the four groups.

Optimal energy management and economic analysis of a grid-interactive PV with battery storage system in Cape Town

Abstract: In this paper, an optimal energy control of a 2 kW residential grid-interactive solar PV system, operating with a battery storage, is presented. A typical household within the city of Cape town, South Africa, is considered as a case study. The aim of the study is to determine the potential of energy cost saving the system could achieve under the new residential time-of-use and feed-in tariff available in South Africa. The simulation results show that the consumer can substantially reduce the energy acquired from the grid and realise a cost saving of 84 % in the summer and 58 % in the winter.

Techno-Economic Analysis of A Grid-Connected Photovoltaic with Groundwater Pumped Hydro Storage for Commercial Farming Activities

Abstract: Underground pump hydro system is a promising innovation technology with power generation potential for remote located farms with adequate availability of underground water resource. In this paper, the techno-economic analysis of a gridconnected solar photovoltaic with groundwater pumped hydro storage for commercial farming activities in arid areas is discussed. The main objective is to reduce the grid electricity cost for farming activities under variable time-of-use electricity tariff. The results of this study indicate that the proposed system is effective in minimizing the grid consumption costs by 95% and 32.4% in winter and summer seasons, respectively. This led to a break-even point of 7 years as compared to the grid.

Economic Power Dispatch for Energy Cost Reduction of a Hybrid Energy System Considering Maximum Demand Charges and Time-based Pricing in a Healthcare Institution

Abstract: This paper presents a model of a hybrid energy system connected to a healthcare institution. The hybrid system proposed for the case study consists of a dual axis PV tracking system and electrical energy storage device supplying power to a critical load in conjunction with an existing grid connection. The healthcare entity is subjected to time-based pricing and maximum demand charges. A medical facility in the city of Bloemfontein in South Africa is chosen as a case study, where solar irradiance is in abundance. The developed model and presented algorithm aim to economically dispatch power between the hybrid energy systems and energy storage scheme in order to minimize the energy usage from the grid and associated costs. The energy usage is subjected to Time-of-Use tariffs and maximum demand charges. The results from simulating the operation of the developed economic dispatch model revealed significant potential energy and associated cost savings. Employing the proposed economic dispatch strategy may potentially reduce the entity’s monthly operation cost by approximately 55%, while maximizing the localized renewable energy production and use of the energy storage scheme.

Techno-economic analysis of hydro aeropower systems for energy cost reduction in farming activities

Abstract: The main aim of this paper is to develop an optimal power dispatch model for grid-connected consumers who are also able to generate electricity using the innovative hydro aeropower systems. The proposed system consists of a wind pump with a hydro generator using groundwater in pumped hydro storage configuration. The developed model minimizes the consumer’s energy costs by maximizing the use of the variable wind power converted and stored into potential hydropower; optimally managing the pumped hydro storage system; and minimizing the use of the electrical utility operating with the Time-of-Use rate. Through a case study in South Africa, the results have demonstrated that, as compare to using the grid as sole power source, the selected consumer can achieve a total daily cost reduction of 49.49% and 53.5% for typical summer and winter days, respectively. The lifecycle cost analysis has projected the system to break-even after 2.6 years as compared to using the grid power exclusively. For a 20 years’ project, using the grid as baseline for the comparison, the lifecycle cost analysis have projected the system to break-even after 2.6 years and save 48.4%. This model can be used to optimally dispatch the power flow in small farming activities with grid connection and where groundwater and wind pumps can be implemented.

Energy Monitoring for Potential Cost Saving in Electricity Bills in a Microbrewery in South Africa

Abstract: The aim of this study is to analyse the present pattern of energy consumption and identify the possible areas where the consumer could reduce energy usage in order to reduce the monthly electricity bills at a selected brewery in Bloemfontein. To achieve this, a real-time monitoring device Power Quality analyser “PEL 103” was installed in the distribution box of a microbrewery in Bloemfontein. The benefits may include the hourly/per second load data analysis that can provide the detailed characteristics of the load profile, outline the energy consumption patterns in order to identify areas where the consumer could reduce the electricity bill. The analysis of the results shows that a substantial amount of electrical energy is consumed during peak billing periods of the day under the time-of-use (ToU) tariff. Based on these results, energy efficiency initiatives may be implemented through demand-side management from peak demand to off-peak or standard time, while maintaining the quality of the beer.

Lifecycle Analysis of A Grid-Interactive Photovoltaic with Battery Storage: Case of South African Residential Loads

Abstract: In this paper, the lifecycle cost analysis of a residential grid-interactive photovoltaic system with a battery storage system is conducted. The proposed grid interactive system operates under the Time of Use (TOU) and Feed-in tariff (FIT) in the South African context. The main objective is to minimize the net electricity cost under a given period which is defined as the difference between the electricity cost, due to the power imported from the grid, and the electricity revenue, due to the power exported to the grid. Based on the simulation results relaying on the lifecycle cost analysis, it is found that the proposed system would break-even in 11.5 years as compared to the grid, with an approximate saving of 35%, translating into savings of R 270 022.83 for a 20 years’ operation life.

A Novel Improvement of the Performance Coefficient of a Residential Air Source Heat Pump Water Heater

Abstract: Air Source Heat Pump (ASHP) water heaters are energy efficient and renewable energy devices employed for sanitary hot heating. The study focused on demonstrating that the Coefficient Of Performance (COP) of an ASHP unit are often higher than the COP of the ASHP water heater. The setup involved the design and installation of a 1.2 kW, 150 L ASHP water heater and a Data Acquisition System (DAS). The DAS consist of a power meter, flow meters, temperature sensors, pressure sensors, ambient temperature and relative humidity sensor and were installed at precise locations of the ASHP water heater. Specific controlled volume of 150, 50 and 100 L were drawn off from the ASHP water heater during the morning, afternoon and evening for a full year. The results depicted that during the summer and winter periods, the average COP of the ASHP water heater was 3.04 and 2.32, respectively. On the contrary, the COP of the ASHP unit was 3.53 and 2.99, respectively. The implementation of electric motors in the prime movers (fan, pump and compressor) with better energy efficiency to replace the existing electric motors, can enhanced the COPs of the ASHP unit and the ASHP water heater.

Managing residential demand uncertainty in a smart grid-interactive hydrokinetic river system

Abstract: The aim of this paper is to provide an integrated optimization and control algorithm in order to solve the residential load demand uncertainty problem as encountered in a grid-interactive hydrokinetic river (GHR) system. The proposed GHR system is incorporated with a pumped hydro-storage system (PHS) to store excess energy. The proposed algorithm aims to resolve the load demand uncertainty in order to minimize the electricity bills of the consumer and to maximize the energy sales into the grid, under time-of-use (TOU) tariff scheme. Therefore, the maximization of load demand satisfaction is not compromised. The traditional open loop optimization approach cannot cater for load demand uncertainty. It becomes more challenging to adequately meet the uncertain load demand. Within this context, the rule-based control algorithm is developed to manage power flow during uncertain load demand. The obtained results demonstrated that the load demand is adequately met at a reduced grid consumption cost, through the application of the rule-based control algorithm. This confirmed that the proposed algorithm benefits the user, by reliably and economically satisfying the load demand at a minimal grid energy cost.