Mohan Kolhe

Techno-Economic Optimum Sizing of a Stand-Alone Solar Photovoltaic System

The techno-economic optimum sizing of a stand-alone photovoltaic (PV) system is a basic requirement for its proliferation. One of the primary concerns in designing a stand-alone PV system is the determination of an optimum relationship between the PV array and storage battery capacity to supply the required energy at a specified energy load fraction. In this paper, a complete analytical methodology has been presented for that. The solar radiation utilizability concept and the monthly average daily PV array efficiency have been used to estimate the performance of a stand-alone PV system and hence for the designing. The techno-economic optimization of a PV system has been done by using levelized energy cost computation based on the total number of battery replacements (brps) through battery life-cycle model by using the solar radiation utilizability concept over the life period of the system. It has been found that energy load fractions as well as the number of brps have a significant impact on the selection of optimum sizing of a stand-alone PV system.

Analytical model for predicting the performance of photovoltaic array coupled with a wind turbine in a stand-alone renewable energy system based on hydrogen

We present the results of an analysis of the performance of a photovoltaic array that complement the power output of a wind turbine generator in a stand-alone renewable energy system based on hydrogen production for long-term energy storage. The procedure for estimating hourly solar radiation, for a clear sunny day, from the daily average solar insolation is also given. The photovoltaic array power output and its effective contribution to the load as well as to the energy storage have been determined by using the solar radiation usability concept. The excess and deficit of electrical energy produced from the renewable energy sources, with respect to the load, govern the effective energy management of the system and dictate the operation of an electrolyser and a fuel cell generator. This performance analysis is necessary to determine the effective contribution from the photovoltaic array and the wind turbine generator and their contribution to the load as well as for energy storage.

Techno-economic optimum sizing of hybrid renewable energy system

Using off grid hybrid renewable energy systems for rural electrification has become an attractive solution for those areas, where grid electricity is not feasible or cost of the grid extension is relatively large. Hybrid system combines several energy systems together, therefore it can supply high reliable electricity rather than a PV/battery system or a wind/battery system. But the most important thing is that the system should be economically attractive. To achieve both of these features, each of the components in the hybrid system should be optimally sized. This requires a detailed techno-economic analysis of different possible hybrid system configurations. The objective of this study is to investigate an optimum combination of different energy systems which can supply electricity to a rural community in Sri Lanka at an affordable price with an accepted level of reliability. The analysis of the hybrid system is done using the micro grid optimization software “HOMER”. A PV/wind/battery/ generator hybrid system is selected because the selected area receives abundant of sunlight and wind power throughout the year with an annual average solar radiation of 5.32 kWh/m2/day and an annual average wind speed of 6.27 ms-1. The system with capacities, 20 kW-PV, 40 kW-wind, 20 kW-generator and a battery bank with 40 batteries is chosen as the optimal hybrid system configuration based on the HOMER optimization and sensitivity results. It can supply the electricity with a levelized cost of 0.36

Multi-agent based public key infrastructure for smart grid

/kWh, which is substantially higher than the price of the grid electricity in Sri Lanka. But due to the unavailability of the national grid, this type of system is required to supply the electricity for rural communities to improve the rural lifestyle and at the mean time these systems will help to reduce the greenhouse gas emissions as well.

Data Communication Security of Advanced Metering Infrastructure in Smart Grid

The electric power grid has been developed over last century and it is facing many problems. The electric grid lacks the ability to adapt and integrate intermittent energy sources and active customer participation. Numbers of architecture have been proposed by various agencies for smart grid. Micro-grid is the lowest node in the hierarchy of smart grid that has to be developed efficiently for optimal performance. Smart grid, which will involve multidirectional energy and information flows, may be susceptible to cyber attack due to involvement of ICT in managing the smart grid. Multiagent based public key infrastructure (PKI) is proposed for the authentication of participating devises in micro-grid. The agents utilize information exchanges from neighboring agents to construct knowledge base that can be used in making efficient decision support system. The studies suggest that multi-agent perform better under the given circumstance and pressure providing the real-time communication.

Empirical electrical modeling for a proton exchange membrane electrolyzer

Advanced Metering Infrastructure (AMI) is very critical part for wired/wireless communication in Smart Grid. It involves communication of vital smart metering data to central control center for smooth functioning of smart grid. Security and reliability of data is of paramount importance for operational reliability of smart grid. AMI network is susceptible to many cyber security threats and attacks. Therefore it is desirable to prevent the data from such vulnerabilities. The paper proposes two-phase method to provide security of data using dedicated authentication server which inhibits malicious and unauthorized nodes to gain access to AMI communication network. Secure environment is created by this method that helps in achieving better throughput and packet delivery ratio. Thus, it improves the security and performance of the network.

Review on photovoltaic based active generator

The hydrogen (H2) economy is a proposal for the distribution of energy using hydrogen as an energy carrier (due to its high mass energy density) for reducing green house gas emissions. Energy conversion from renewable energy (RE) sources with suitable energy storage can play an important role in the development and operation of RE systems. The integrated intermittent RE system, (e.g. wind, solar energy systems) based on energy storage in the form of electrolytic H2, is considered a promising alternative to overcome the intermittence of the RE sources. In comparison to commonly used battery storage, H2 is well suited for seasonal storage applications due to its inherent high mass energy density. PEM based electrolysis has many advantages as compared to conventional alkaline based electrolysis e.g. smaller dimension and mass, lower power consumption, intrinsic ability to cope with transient electrical power variations, high degree of purity of gases and possibility of getting H2 compressed at higher pressure within the unit and more safety level. In this work, PEM electrolyzer model has been developed. Input current-voltage (I–V) characteristic of electrolyzer has been modeled by using the experimental analysis under steady state conditions at room temperature. The model is developed by using electrical equivalent circuit topology by considering useful power conversion and losses. Electrolytic H2 production rates are found out with respect to the input current and power. These experimental results are verified with the theoretical results and the relative errors are < 2%. The electrolytic H2 production rate increases linearly with current, but variation of electrolytic H2 production rate with the input electrical power is nonlinear (i.e. logarithmic). These are verified through the developed model also. This model will help to analyze energy system behavior where is stored in the electrolytic H2 form.

Integration of distributed energy systems in micro-grid architecture for making a virtual power plant

An active generator has the capacity to support frequency control and instantaneous power balance. The grid operator adjusts the power dispatch of generators according to power demand fluctuations. Photovoltaic (PV) based active generators can be used as load following generators in the same manner as other power dispatch generators. This new type of distribution system, based on active generator(s), needs new innovative management and operation strategies for increasing the penetration of intermittent renewable energy systems. The considered PV based active generator has three units, i.e., PV array, battery storage and super capacitor. In this review paper, the management and operation approaches of PV based active generators are discussed.

Domestic demand predictions considering influence of external environmental parameters

This paper presents a novel concept for increasing the penetration level of distributed renewable energy systems into the main electricity grid. When increasing the renewable energy penetration, it is important to implement the frequency based power delivery in distributed generators and work as traditional synchronous generators. This can be achieved by improving the power processing unit of each renewable generation units to work as active generators. But in existing grid architecture, the grid frequency is controlled as one common variable over the electricity grid. With such a method, it is difficult to use frequency based power sharing in small distributed generators and participate in grid frequency control activities. In this proposed grid connected micro-grid architecture, the micro-grid is connected to the main-grid via back-to-back converter, which gives the facility to use distributed local frequency droop settings within the micro-grids and isolate the two AC grids via intermediate DC link. Frequency Droop control has been implemented in the micro-grid side of back to back converter. With this method, the small renewable generations in micro-grid can adjust their power level in response to the local frequency variations and sharing loads effectively while reducing the large power variations from the main-grid.

Charging management of grid integrated battery for overcoming the intermittency of RE sources

A precise prediction of domestic demand is very important for establishing home energy management system and preventing the damage caused by overloading. In this work, active and reactive power consumption prediction model based on historical power usage data and external environment parameter data (temperature and solar radiation) is presented for a typical Southern Norwegian house. In the presented model, a neural network is adopted as a main prediction technique and historical domestic load data of around 2 years are utilized for training and testing purpose. Temperature and global irradiation (which illustrates the solar radiation level quantitatively) are employed as external parameters. From the results, the efficiency of predictions are evaluated and compared. It can be observed from the numerical results that predictions using historical power data together with external data perform better than the case where only power usage data are adopted.