Techno-Economic Feasibility Study of Autonomous Hybrid AC/DC Microgrid System

Distributed generation technology based on diesel generators often has been considered as a viable solution to providing power to remote areas, but the sky‐rocketing of diesel fuel price and the increasing cost of delivery to such remote sites have called for providing a sustainable solution that is environmentally friendly, economical, affordable, and easily accessible. To this end, the use of locally available energy resources is accepted as a sustainable solution in providing electricity for rural and remote settlements. The system cost of wind and solar energy systems is continuously decreasing because of the increase in the acceptance and deployment of the energy systems based on these renewable energy resources. A standalone hybrid AC/DC electric power system is designed, modeled, simulated, and optimized in HOMER Pro. HOMER is a Hybrid Optimization Model of Electric Renewable that enables the comparison of electric and thermal power production technologies across an extensive variety of applications. Both cycle‐charging and load‐following dispatched strategies are investigated. Plausible selected system components ratings are chosen for the simulation to ensure that there is enough search space for HOMER Pro to obtain an optimal system configuration. Net present cost (NPC) is used as an economic metric to assess the optimal configuration that is technically feasible

Development of an Energy Management System Control Algorithm for a Remote Community Microgrid System

Rural communities are often unable to access electrical energy as they are located away from the national grid. Renewable energy sources (RESs) make it possible to provide electrical energy to these isolated areas. Sustainable generation is possible at a local level and is not dependent on connection to a national power grid

STRATEGIC MODULATION OF THERMAL TO ELECTRICAL ENERGY RATIO PRODUCED FROM PV/T MODULE

Several strategies have been developed to enhance the performance of a solar photovoltaicthermal (PV/T) system in buildings. However, these systems are limited by the cost, complex structure and power consumed by the pump. This paper proposes an optimisation method conversion strategy that modulates the ratio of thermal to electrical energy from the photovoltaic (PV) cell, to increase the PV/T system’s performance. The design and modelling of a PV cell was developed in MATLAB/Simulink to validate the heat transfer occurring in the PV cell model, which converts the radiation (solar) into heat and electricity. A linear regression equation curve was used to define the ratio of thermal to electrical energy technique, and the behavioural patterns of various types of power (thermal and electrical) as a function of extrinsic cell resistance (Rse). The simulation results show an effective balance of the thermal and electrical power when adjusting the Rse. The strategy to modulate the ratio of thermal to electrical energy from the PV cell may optimise the PV/T system’s performance. A change of Rse might be an effective method of controlling the amount of thermal and electrical energy from the PV cell to support the PV/T system temporally, based on the energy need. The optimisation technique of the PV/T system using the PV cell is particularly useful for households since they require electricity, heating, and cooling. Applying this technique demonstrates the ability of the PV/T system to balance the energy ( thermal and electrical) produced based on the weather conditions and the user’s energy demands

Investigation of common-mode voltage and ground leakage current of grid-connected transformerless PV inverter topology

The problems of increasing electricity demand by the unabated population and economy growth can be solved by employing sustainable distributed generation technologies. Convectional primary energy sources such as coal, liquid hydrocarbons’ and natural gasses create environmental degradation and energy security problems. Even though the cost of solar energy is zero, the same cannot be said of a solar energy system. The system cost especially the initial capital investment has been hindering the rapid deployment of solar energy systems. One way of reducing the system cost of a solar energy system is to look into the constituent components and see where cost can be reduced without compromising the system efficiency and human safety. Eliminating the isolation transformer reduces the cost and increases the system overall efficiency. However, the galvanic connection between the PV array and the utility grid creates a safety problem for people and system equipment. We present a simplified model for the investigation of the common mode voltage and ground leakage current that can lead to electromagnetic interference. The leakage current level is used for the determination of the suitability of the investigated PV inverter topology for grid connection without isolation transformer

Batteryless PV desalination system for rural areas: A case study

The use of photovoltaics (PVs) to power reverse osmosis (RO) desalination can potentially break the dependence of this desalination process on conventional energy sources (oil, coal, electricity from national grid), reduce operational costs, and improve environmental sustainability. In this paper, a methodology for the optimal sizing and performance evaluation of a stand-alone PV system to power an RO desalination unit is presented. This unit covers the water needs of inhabitants of a small isolated village called Mrair-Gabis, near the Ajdabiya city in north-eastern Libya. A photovoltaic-reverse osmosis (PV-RO) system offers good possibilities for satisfying this need. Due to the many technical problems with batteries, as well as their high cost, the system studied in this paper will not consider the use of batteries; the viability of a batterryless system is facilitated by the high solar radiation at the selected site, and long daily average insolation duration. From the water consumption records it was noticed that during some days in summer the water produced by the RO unit does not meet the water demand; on the other hand, during some days of the month there will be an excess of water production. The above considerations led to the design of a freshwater tank, to cover the potable water needs for people in cases of the desalination unit breaking down, either due to technical problems or on the cloudy days. The purpose of the water tank is therefore to store excess water when production exceeds supply. Simulations were carried out using MATLAB Software to size and assess the performance of a stand-alone PV system. The computer program can be applied to any site with different weather conditions

Batteryless PV desalination system for rural areas: A case study

The use of photovoltaics (PVs) to power reverse osmosis (RO) desalination can potentially break the dependence of this desalination process on conventional energy sources (oil, coal, electricity from national grid), reduce operational costs, and improve environmental sustainability. In this paper, a methodology for the optimal sizing and performance evaluation of a stand-alone PV system to power an RO desalination unit is presented. This unit covers the water needs of inhabitants of a small isolated village called Mrair-Gabis, near the Ajdabiya city in north-eastern Libya. A photovoltaic-reverse osmosis (PV-RO) system offers good possibilities for satisfying this need. Due to the many technical problems with batteries, as well as their high cost, the system studied in this paper will not consider the use of batteries; the viability of a batterryless system is facilitated by the high solar radiation at the selected site, and long daily average insolation duration. From the water consumption records it was noticed that during some days in summer the water produced by the RO unit does not meet the water demand; on the other hand, during some days of the month there will be an excess of water production. The above considerations led to the design of a freshwater tank, to cover the potable water needs for people in cases of the desalination unit breaking down, either due to technical problems or on the cloudy days. The purpose of the water tank is therefore to store excess water when production exceeds supply. Simulations were carried out using MATLAB Software to size and assess the performance of a stand-alone PV system. The computer program can be applied to any site with different weather conditions

A CONCEPTUAL STUDY OF A LIQUID METAL ALLOY IN A DISK-SHAPED MAGNETOHYDRODYNAMICS CONVERSION SYSTEM

The use of solar-heated liquid metal in a magnetohydrodynamics (MHD) generator provides an alternative and direct conversion method for electric power generation. This prompted the present study to conduct a three-dimensional numerical analysis for a liquid Ga68In20Sn12 flow exposed to several uniform magnetic field intensities (Bo of 0.5 T, 1T and, 1.41 T) within a disk channel geometric boundary. The aim is to study the influence of the external magnetic fields on the generator performance and the fluid flow stability at a high Reynolds number (Re) and Hartmann number (Ha) using the Ansys Fluent software. The simulation results show that at Re of ≈ 2.44e6, the fluid velocity decreases inside the generator regardless of Bo. When Bo of 1T and 1.41T are applied, the velocity magnitude decreases and spreads within the disk channel and walls due to high Ha values (5874 and 8282). The fluid pressure increases from the nozzle pipe inlet to the disk channel and decreases towards the outlet. The induced current density in the radial direction, jx, increases within the disk channel and near the inner electrode edge as Bo increases. A significant observation is that the current densities obtained for Bo of 1T and 1.41T cases are higher than in other cases. The numerical analysis obtained in this study showed that the Bo of either 1T or 1.41T is needed to achieve the required flow stability, current density, and output powers

Fuzzy Rule-Based and Particle Swarm Optimisation MPPT Techniques for a Fuel Cell Stack

The negative environmental impact and the rapidly declining reserve of fossil fuel-based energy sources for electricity generation is a big challenge to finding sustainable alternatives. This scenario is complicated by the ever-increasing world population growth demanding a higher standard of living. A fuel cell system is able to generate electricity and water with higher energy efficiency while producing near-zero emissions. A common fuel cell stack displays a nonlinear power characteristic as a result of internal limitations and operating parameters such as temperature, hydrogen and oxygen partial pressures and humidity levels, leading to a reduced overall system performance. It is therefore important to extract as much power as possible from the stack, thus hindering excessive fuel use. This study considers and compares two Maximum Power Point Tracking (MPPT) approaches; one based on the Mamdani Fuzzy Inference System and the other on the Particle Swarm Optimisation (PSO) algorithm to maintain the output power of a fuel cell stack extremely close to its maximum. To ensure that, the power converter interfaced to the fuel cell unit must be able to continuously self-modify its parameters, hence changing its voltage and current depending upon the Maximum Power Point position. While various methods exist for Maximum Power Point tracker design, this paper analyses the response characteristics of a Mamdani Fuzzy Inference Engine and the Particle Swarm Optimisation technique. The investigation was conducted on a 53 kW Proton Exchange Membrane Fuel Cell interfaced to a DC-to-DC boost converter supplying 1.2 kV from a 625 V input DC voltage. The modelling was accomplished using a Matlab/Simulink environment. The results showed that the MPPT controller based on the PSO algorithm presented better tracking efficiency as compared to the Mamdani controller. Furthermore, the rise time of the PSO controller was slightly shorter than the Mamdani controller and the overshoot of the PSO controller was 2% lower than that of the Mamdani controller

Operating Voltage and Frequency Regime Validation of Grid Code Requirements in South Africa

South Africa first implemented rolling blackouts known as load shedding to protect the integrity and maintain stability of their ailing electrical grid over a decade ago. Since then, load shedding has become a daily occurrence, which South Africa plans to alleviate through the addition of grid-connected renewable generation. Significant renewable energy (RE) additions can however negatively affect a grid, prompting South Africa to develop RE-specific grid code requirements as mitigation. Given this strategy to address the country’s supply challenges using RE, and the still unknown effects of the country’s aggressive RE integration planned, South Africa must perform the necessary simulations tailored to the country’s unique grid conditions, and local RE-specific grid code requirements to ensure a RE-driven solution are indeed viable. Prompted by the lack of a suitably tailorable simulation platform, this paper proceeds to discuss the development of a tailorable grid code-guided renewable power plant (RPP) behavioral studies testbed. The testing methodology involves feeding grid disturbance event data to an RPP modeled after Eskom’s Sere wind farm in South Africa, which is operated in line with local RPP-specific grid code voltage and frequency requirements to assess the testbed’s grid code-guided RPP operating approach. Results show the testbed to effectively distinguish between grid code-specified no-fault, fault ride-through, and trip conditions, operating the simulated RPP accordingly. Consequently, as compared to comparable RE integration simulation platforms, the reviewed testbed has the potential of producing individualized results, owing to its tailorable grid, RPP, and incorporated grid code guiding specifications

Design of low voltage DC microgrid system for rural electrification in South Africa

2013 Joint International Conference on Engineering Education and Research and International Conference on Information Technology (ICEE/ICIT-2013)This project entails the design of a low voltage DC microgrid system for rural electrification in South Africa. Solar energy is freely available, environmental friendly and it is considered as a promising power generating source due to its availability and topological advantages for local power generation. Off-grid solar systems are perceived to be a viable means of power delivery to households in rural outlying areas in South Africa as solar panels can be used almost anywhere in the country. The design presented in this paper is based on the power demand estimation, photovoltaic panel selection, battery sizing and wire selection for the distribution system