Off-grid Micro Research Articles

Modeling and Analysis of the Dynamic Response of an Off-Grid Synchronous Generator Driven Micro Hydro Power System

This paper models and analyses the dynamic response of a synchronous generator driven off-grid micro hydro power system using Simulink tool of MATLAB software. The results are assessed from various perspectives including regulation through no load to full load and overload scenarios under normal and abnormal operating conditions. The investigation under the normal conditions of no load, linearly changing load and full load divulges that the system operates in a satisfactory manner as generator voltage and frequency remain approximately constant at 1 pu. However, at full load generator voltage and frequency drop 3% and 0.5% respectively from its nominal values but remain within prescribed standard IEC limits. The results also expose that the abnormal conditions produced by abrupt changes in load, system faults and severe overload, cause the unwonted variations in the magnitude of generator parameters. Moreover, the study reveals that the system stability significantly enhances when the system is run at full load because the regulation time to fix the variations in the generator parameters; except input mechanical power; decreases, e.g. from 4.1 sec to 0.8 sec for generator voltage, with the increase in the loading from quarter to full load respectively at unity power factor. Further, it is also observed that the regulation time rises, e.g. from 0.8 sec to 1.3 sec for generator voltage, with the reduction in load power factor from unity to 0.8, respectively. Thus, proper protection, to cater for increased fault current at full load and power factor correction must be provided to improve the system stability and protection. Furthermore, it is also concluded that the over loading in any case should be strongly avoided in this type of system and it should never be allowed to exceed 20% of the full load value to avoid system failure

Modeling and Analysis of the Dynamic Response of an Off-Grid Synchronous Generator Driven Micro Hydro Power System

This paper models and analyses the dynamic response of a synchronous generator driven off-grid micro hydro power system using Simulink tool of MATLAB software. The results are assessed from various perspectives including regulation through no load to full load and overload scenarios under normal and abnormal operating conditions. The investigation under the normal conditions of no load, linearly changing load and full load divulges that the system operates in a satisfactory manner as generator voltage and frequency remain approximately constant at 1 pu. However, at full load generator voltage and frequency drop 3% and 0.5% respectively from its nominal values but remain within prescribed standard IEC limits. The results also expose that the abnormal conditions produced by abrupt changes in load, system faults and severe overload, cause the unwonted variations in the magnitude of generator parameters. Moreover, the study reveals that the system stability significantly enhances when the system is run at full load because the regulation time to fix the variations in the generator parameters; except input mechanical power; decreases, e.g. from 4.1 sec to 0.8 sec for generator voltage, with the increase in the loading from quarter to full load respectively at unity power factor. Further, it is also observed that the regulation time rises, e.g. from 0.8 sec to 1.3 sec for generator voltage, with the reduction in load power factor from unity to 0.8, respectively. Thus, proper protection, to cater for increased fault current at full load and power factor correction must be provided to improve the system stability and protection. Furthermore, it is also concluded that the over loading in any case should be strongly avoided in this type of system and it should never be allowed to exceed 20% of the full load value to avoid system failure

A Multi-period Optimization Model for the Design of an Off-Grid Micro Hydro Power Plant with Profitability and Degradation Considerations

Micro hydroelectric power is a clean and efficient source of energy that has been used for the electrification of rural off-grid communities. However, numerous micro hydro installations have failed as caused by factors such as poor site selection and uneconomical design of materials, among others. A multi-period mixed integer linear programming model for the design of an off-grid micro hydro power plant is then developed. The proposed model is able to provide technical specifications such as the penstock dimensions, turbine choice, weir height, and site choice in order to fulfill a community’s demand while simultaneously maximizing the net present value of the investment. The model may choose among different productive end uses, with each being subject to a respective investment cost as well as a set-up time and degradation rate. Computational experiments demonstrate the different capabilities of the model to address real-life scenarios such as population growth and streamflow variability. An increase in energy consumption due to population growth leads to the requirement of a more powerful turbine. Capacity limitations likewise prevent the community to invest in productive end usage. Meanwhile, streamflow variability potentially reduces the capability of the power plant to produce electricity. In these instances, batteries had to simultaneously be used in order to augment the increase in energy requirement.

Low Head Micro Hydro Systems for Rural Electrification

Off-grid micro hydro is an economical and practical approach to generate electric power to fulfil energy demand in rural areas. Large numbers of successful high head micro hydro project have been reported however the application of low head micro hydro system is scarce. Low head micro hydro system commonly recognized using complex profile blades, larger civil structure and electromechanical components to extract energy. This leads to a more complex system and higher cost with respect to similar power rating. On the other hand, the potential to exploit low head micro hydro system is enormous because there is where population is concentrated. The aim of this paper is to present the main issues and technologies encircled the application of low head micro hydro power for rural electrifications. Reviews on relevant issues on micro hydro surrounding available turbines for low head sites, civil structures and electric motor are also presented. This is followed by accentuating the importance of information dissemination using the internet to potential users. The information can be used by researchers, plant managers, individual or rural communities to understand the potential of available technologies.

Maximizing energy efficiency of islanded micro water-energy nexus using co-optimization of water demand and energy consumption

Water and energy systems are interdependent. However, at national and international levels, energy and water systems have been designed individually. To optimize the use of energy resources and have a more sustainable energy processes, a new formulation is proposed in this paper to optimize the energy consumption of water-energy systems at a community scale. More specifically, single-objective, bi-level, and co-optimization models are developed to minimize the energy consumption of a micro water distribution network concerning three scenarios: (1) standalone operation; (2) integrated with a grid-connected micro energy system with no storage unit; and (3) integrated with an off-grid micro energy system with storage units. In all conditions, a mixed integer nonlinear programming formulation is used to solve the optimization problems. Pump operations with varying statuses, flow rates, and speeds are contemplated to formulate the energy consumption of the micro water, considering a quadratic function for the pump’s energy head changing with flow rate. The micro water network is designed based on a diurnal pattern of water demand for a network including 1 reservoir, 1 water tank, 6 nodes, and 2 pumps. The micro energy system includes a microgrid with a combined heat and power plant (CHP), diesel (DS) generator, natural gas (NG) generator, renewable sources (solar and wind), and energy storage units. Several case studies are carried out to compare the performance of developed optimization models.

Optimal sizing of battery energy storage systems in off-grid micro grids using convex optimization

Abstract Battery as an energy storage system is a key element in Microgrids (MGs). Therefore, determining the optimal size of battery energy storage systems (BESS) can reduce the operational costs of MGs. The goal of this paper is to calculate the optimal size of a BESS in an off-grid MG while minimizing the total cost using convex optimization methods. This paper proposes a new two-step cost-based method to determine the optimal size of a BESS in an MG. In the first step, in order to optimize the operation of the MG, a unit commitment (UC) problem is solved. In the next step, the optimal size of the BESS is determined using convex optimization considering several physical and operational constraints. The resulting problem is a non-convex non-linear problem. However, the problem can be transformed into a convex problem using convex relaxation methods. In the next step, the convexity and feasibility of the optimization problem is proved. The CVX toolbox package integrated with MATLAB is used to solve the problem. To assess the effects of BESS on operational and total costs of the MG, four scenarios are studied. Additionally, the results have been compared with PSO and GA algorithms and effectiveness of the proposed method has been shown.

Estimating the price (in)elasticity of off-grid electricity demand

Community-scale power infrastructure may be the only electrification option for tens of millions households that remain out of reach from centralized power grids. The responsiveness of household electricity demand to price is a crucial design input for off-grid systems. While the price elasticity of electricity demand of grid-connected consumers has been abundantly studied, few studies focus on off-grid communities where substantial econometric challenges arise, including the absence of metered consumption data and electricity prices that are simultaneously determined by cost and demand considerations. This study attempts to address these challenges for the case of off-grid micro hydropower consumers. It makes two core contributions: First, we propose the surface area of the contributing hydrologic catchment as a new instrumental variable to estimate elasticity using a cross sectional dataset of existing micro hydropower infrastructure. Second, we provide a first price-elasticity estimate (−0.15) for off-grid electricity demand in Nepal. We surmise that the small (in absolute value) elasticity value found in this study arises from the low levels of consumption observed off-the-grid. We use a Monte Carlo analysis to show that failing to account for this disparity can lead to substantial financial losses caused by suboptimal power infrastructure design.

Bridging the information gap: A webGIS tool for rural electrification in data-scarce regions

Rural electrification in developing countries is often hampered by major information gaps between local communities and urban centers, where technical expertise and funding are concentrated. The tool presented in this paper addresses these gaps to support the implementation of off-grid micro hydropower infrastructure. Specifically, we present a method to site, size and evaluate the potential for micro hydropower based on remote sensing data. The method improves on previous approaches by (i) incorporating the effect of hillslope topography on the optimal layout of the infrastructure, and (ii) accounting for the constraints imposed by streamflow variability and local electricity demand on the optimal size of the plants.An assessment of the method’s performance against 148 existing schemes indicates that it correctly identifies the most promising locations for hydropower in Nepal, but does not generally reproduce the specific design features of constructed plants, which are affected by site-specific constraints. We develop a proof-of-concept computer tool to explore the potential of webGIS technology to account for these constraints by collecting site-specific information from local users.