Showing papers on "Stand-alone power system published in 2009"

Wind Energy Generation: Modelling and Control

Abstract: With increasing concern over climate change and the security of energy supplies, wind power is emerging as an important source of electrical energy throughout the world. Modern wind turbines use advanced power electronics to provide efficient generator control and to ensure compatible operation with the power system. Wind Energy Generation describes the fundamental principles and modelling of the electrical generator and power electronic systems used in large wind turbines. It also discusses how they interact with the power system and the influence of wind turbines on power system operation and stability.

Techno-economic evaluation of off-grid hybrid photovoltaic–diesel–battery power systems for rural electrification in Saudi Arabia—A way forward for sustainable development

Abstract: The burning of depleting fossil fuels for power generation has detrimental impact on human life and climate. In view of this, renewable solar energy sources are being increasingly exploited to meet the energy needs. Moreover, solar photovoltaic (PV)–diesel hybrid system technology promises lot of opportunities in remote areas which are far from utility grid and are driven by diesel generators. Integration of PV systems with the diesel plants is being disseminated worldwide to reduce diesel fuel consumption and to minimize atmospheric pollution. The Kingdom of Saudi Arabia (K.S.A.) being endowed with high intensity of solar radiation, is a prospective candidate for deployment of PV systems. Also, K.S.A. has large number of remote scattered villages. The aim of this study is to analyze solar radiation data of Rafha, K.S.A., to assess the techno-economic feasibility of hybrid PV–diesel–battery power systems to meet the load requirements of a typical remote village Rawdhat Bin Habbas (RBH) with annual electrical energy demand of 15,943 MWh. Rafha is located near RBH. The monthly average daily global solar radiation ranges from 3.04 to 7.3 kWh/m 2 . NREL's HOMER software has been used to perform the techno-economic evaluation. The simulation results indicate that for a hybrid system composed of 2.5 MWp capacity PV system together with 4.5 MW diesel system (three 1.5 MW units) and a battery storage of 1 h of autonomy (equivalent to 1 h of average load), the PV penetration is 27%. The cost of generating energy (COE, US$/kWh) from the above hybrid system has been found to be 0.170$/kWh (assuming diesel fuel price of 0.1$/l). The study exhibits that the operational hours of diesel generators decrease with increase in PV capacity. The investigation also examines the effect of PV/battery penetration on COE, operational hours of diesel gensets. Concurrently, emphasis has been placed on: un-met load, excess electricity generation, percentage fuel savings and reduction in carbon emissions (for different scenarios such as: PV–diesel without storage, PV–diesel with storage, as compared to diesel-only situation), COE of different hybrid systems, etc. The decrease in carbon emissions by using the above hybrid system is about 24% as compared to the diesel-only scenario.

Comparative analyses of seven technologies to facilitate the integration of fluctuating renewable energy sources

Abstract: An analysis of seven different technologies is presented. The technologies integrate fluctuating renewable energy sources (RES) such as wind power production into the electricity supply, and the Danish energy system is used as a case. Comprehensive hour-by-hour energy system analyses are conducted of a complete system meeting electricity, heat and transport demands, and including RES, power plants, and combined heat and power production (CHP) for district heating and transport technologies. In conclusion, the most fuel-efficient and least-cost technologies are identified through energy system and feasibility analyses. Large-scale heat pumps prove to be especially promising as they efficiently reduce the production of excess electricity. Flexible electricity demand and electric boilers are low-cost solutions, but their improvement of fuel efficiency is rather limited. Battery electric vehicles constitute the most promising transport integration technology compared with hydrogen fuel cell vehicles (HFCVs). The costs of integrating RES with electrolysers for HFCVs, CHP and micro fuel cell CHP are reduced significantly with more than 50% of RES.

Energy, economics and environmental impacts of renewable energy systems

Abstract: The renewable based electricity generation technologies were assessed against a range of sustainability indicators using data obtained from the literature. These indicators are cost of electricity generation, greenhouse gas emissions and energy pay-back time. All the three parameters were found to have a very wide range for each technology. For grading different renewable energy sources a new figure of merit has been proposed, linking greenhouse gas emissions, energy pay-back time and cost of electricity generated by these renewable energy sources. It has been found out that wind and small hydro are the most sustainable source for the electricity generation.

Techno-economic comparison of energy storage systems for island autonomous electrical networks

Abstract: The oil-dependent electricity generation situation met in the Aegean Archipelago Islands is in great deal determined by increased rates of fuel consumption and analogous electricity production costs, this being also the case for other island autonomous electrical networks worldwide. Meanwhile, the contribution of renewable energy sources (RES) to the constant increase recorded in both the Aegean islands’ annual electricity generation and the corresponding peak load demand is very limited. To compensate the unfavorable situation encountered, the implementation of energy storage systems (ESS) that can both utilize the excess/rejected energy produced from RES plants and improve the operation of existing thermal power units is recommended. In the present study, a techno-economic comparison of various RES-ESS configurations supported by the supplementary or back-up use of existing thermal units is undertaken. From the results obtained, the shift of direction from the existing oil-dependent status to a RES-based alternative in collaboration with certain storage technologies entails – apart from the clear environmental benefits – financial advantages as well.

Indoor power harvesting using photovoltaic cells for low power applications

Abstract: Utilization of low power indoor devices such as remote sensors, supervisory and alarm systems, distributed controls, and data transfer system are on steady rise. Due to remote and distributed nature of these systems, it is attractive to avoid using electrical wiring to supply power to them. Primary batteries have been used for this application for many years but they require regular maintenance at usually hard to access places. This paper provides a complete analysis of a PV harvesting system for indoor low power applications. The characteristics of a target load, photovoltaic (PV) cell and power conditioning circuit are discussed. Different choices of energy storage are also explained. Implementation and test results of the system are presented that highlights the practical issues and limitations of the system.

Simulation of the European Electricity Market and CCS Development with the HECTOR Model

Abstract: In this paper we introduce HECTOR, a new and advanced long-term electricity market model that simulates market behavior bottom-up through opportunistic, variable cost-based bidding of individual power plants into auction-based national markets with international interconnection capacities Unlike most other approaches, we implement the objective function on an hourly level This allows for a reduction of the solution space, and enables a higher modeling resolution, including opportunistic bidding behavior of power plants based on expected supply scarcity, and ex-post investment decisions based on NPV considerations The model simulates the electricity markets of 19 European countries, with over 400 groups of power plants, and is able to closely approximate historic electricity prices The average base load price computed by the model for 2006-2008 and across the largest regions in Europe is 545 €/MWh, compared to 548 €/MWh in reality, using 2005 as training period In a projection until 2040, we find that conventional fossil fuel-fired power plants are replaced both by renewable energy technologies and large quantities of CCS, the latter of which almost fully utilize available CO2 storage capacities in some of the regions studied

Modeling of a vanadium redox flow battery electricity storage system

Abstract: Today, the electricity industries are facing new challenges as the market is being liberalized and deregulated in many countries. Electricity storage is undoubtedly a disruptive technology that will play, in the near future, a major role in the fast developing distributed generations network. Indeed, electricity storage has many potential applications: management of the supply and demand of electricity, power quality, integration of renewable sources, improvement of the level of use of the transport and distribution network, etc. Over the years, many storage technologies have been investigated and developed, some have reached the demonstrator level and only a few have become commercially available. The pumped hydro facilities have been successfully storing electricity for more than a century; but today, appropriate locations are seldom found. Electrochemical storage is also an effective means to accumulate electrical energy; among the emerging technologies, the flow batteries are excellent candidates for large stationary storage applications where the vanadium redox flow battery (VRB) distinguishes itself thanks to its competitive cost and simplicity. In this ambitious work that encompasses the domains of electricity, electrochemistry and fluid mechanics, we have proposed a novel multiphysics model of the VRB. This model describes the principles and relations that govern the behaviour of the VRB under any set of operating conditions. Furthermore, this multiphysics model is a powerful means to identify and quantify the sources of losses within the VRB storage system; indeed, one of the purposes of this study is to propose strategies of control and operation for a greater effectiveness of the overall storage system. The electrochemical model is based on the electrochemical principles and the study of the VRB chemistry; this model determines the equilibrium voltage from the vanadium concentrations, and the associated activation, concentration, ohmic and ionic overpotentials. Furthermore, the vanadium concentrations within the tank and the stack are constantly determined as a function of the current and the electrolyte flowrate. A simplified model of the internal loss is also proposed. The electrochemical performance was then established through the simulation of a stand alone system composed of a solar source, a VRB and a load. The model determines the stack voltage, the power flows and the vanadium concentrations over a 24 h period. Furthermore, the model was successfully compared with experimental data through a series of charge and discharge cycles at constant currents. Thereafter, the properties of the electrolyte are briefly investigated: in particular their dependence upon the electrolyte composition. Indeed, the viscosity and the density are important parameters of the mechanical model. In order to analyse the battery performance, a mechanical model has been proposed to determine the mechanical power required to flow the electrolytes. This model based on fluid mechanics has an analytical part that predicts the pressure drop within the pipes and the tanks, and a numerical part. Indeed, the stack geometry is so complex that it can not be described analytically; therefore, a numerical model based on finite element method (FEM) is proposed. Hence, the mechanical power necessary to the battery operation is obtained at any operating conditions. The electrochemical and the mechanical models are finally assembled to form the original multiphysics model of the VRB. This model provides a good insight of the battery operation and offers a powerful means to enhance the battery performance. Indeed, there is at constant current an optimal flowrate that maximizes the efficiency. A second series of charge and discharge cycles has determined the efficiency of different control strategies. Finally, the battery operations at constant power were also discussed in details and an optimal operating point has been highlighted.

Modeling and control of an integrated wind power generation and energy storage system

Abstract: Wind energy is gaining the most interest among a variety of renewable energy resources, but the disadvantage is that wind power generation is intermittent, depending on weather conditions. Energy storage is necessary to get a smooth output from a wind turbine. This paper presents a new integrated power generation and energy storage system for doubly-fed induction generator based wind turbine systems. A battery energy storage system is connected to the DC link of the back-to-back power converters of the doubly-fed induction generator through a bi-directional DC/DC power converter. The energy storage device is controlled so as to smooth out the total output power as the wind speed varies. Control algorithms are developed for the grid-side converter, rotor-side converter and battery converter, and are tested on a simulation model developed in MATLAB/Simulink. The model contains a DFIG wind turbine, three PWM power converters and associated controllers, a DC-link capacitor, a battery, and an equivalent power grid. Simulation studies are carried out on a 2MW DFIG wind turbine and the results suggest that the integrated power generation and energy storage system can supply steady output power as the wind speed changes.

Solar power generation with multiple energy conversion modes

Abstract: A multi-mode solar power generation system can include a first energy conversion system that generates electricity from a working fluid heated by a portion of solar radiation focused by a plurality of heliostats. The multi-mode solar power generation system can also include a second energy conversion system that generates electricity from an unused portion of the focused solar radiation using a different energy conversion mode than that of the first energy conversion system. The second energy conversion system can include one or more photovoltaic converters, which directly convert solar radiation to electricity. The unused radiation from the first energy conversion system can include radiation spillage or dumped radiation from a thermal receiver of the first energy conversion system.

Supercapacitors Energy Storage System for Power Quality Improvement: An Overview

Abstract: Power quality problem causes a misoperation or failure of end user equipments. Distribution network, sensitive industrial loads and critical commercial operations suffer from outages and service interruptions which can cost financial losses to both utility and consumers. In India the use of electronic loads is increasing very fast and the gap between demand and the supply have made the reliability and power quality a critical issue. Further there is continuous thrust on optimal utilization of the non-conventional energy sources along with the central power station. In this paper a critical review have been presented chronologically various work to improve quality of power with the help of energy storage device i.e. Supercapacitors energy storage systems for ASD, elevators, UPS, and power distribution system, ride through capability, real power injection and reactive power injection for stabilization of the system.

Power system operation with large-scale wind power in liberalised environments

Abstract: Our society revolves around electricity. Most electricity is produced from fossil fuels, such as coal and natural gas. The disadvantages are that their supply is finite and unevenly distributed across the earth. Conventional power stations also emit greenhouse gases. Therefore, sustainable alternativees must be developed, such as wind power. The disadvantages of wind are that it may or may not blow and that it is unpredictable. Th generation of electricity must however always equal the consumption. This makes the integration of wind power in the electricity system more difficult. This Ph.D.-theis investigates the integration of wind power into the existing power system. Simulation models are developed and used to explore the operation of power systems with a lot of wind power. The simulations provide a picture of the reliability, cost and emission of CO2 of the generation of electricity, with and without wind power. The research also takes into account electricity exchange on international markets. Possible solutions for integrating wind power, such as flexible power plants and energy storage, are investigated as well.

Forecasting electric power generation in a photovoltaic power system for an energy network

Abstract: Recently, there has been an increase in concern about the global environment Interest is growing in developing an energy network by which new energy systems such as photovoltaic and fuel cells generate power locally and electrical power and heat are controlled with a communication network We developed the power generation forecast method for photovoltaic power systems in an energy network The method makes use of weather information and regression analysis We carried out forecasting power output of the photovoltaic power system installed in Expo 2005, Aichi Japan As a result of comparing measurements with prediction values, the average prediction error per day was about 26% of the measured power © 2009 Wiley Periodicals, Inc Electr Eng Jpn, 167(4): 16–23, 2009; Published online in Wiley InterScience (wwwintersciencewileycom) DOI 101002/eej20755

A novel power management control strategy for stand-alone photovoltaic power system

Abstract: The solar photovoltaic power has received great attention and experienced impressive progress in the countries all over the world in recent years because of more and more serious energy crisis and environmental pollution. This paper proposes a novel power management control strategy for stand-alone photovoltaic power system, which consists of a solar cell array, a battery, a uni-directional DC-DC converter, and a bi-directional DC-DC converter. The solar cell array powers the steady state energy and the battery compensates the dynamic energy. The goal of the power management control strategy is to control the un-directional DC-DC converter and bi-direction DC-DC converter to operate in suitable modes according to the condition of solar cell and battery, so as to coordinate the two sources of solar cell and battery supplying power and ensure the system operates with high efficiency and behaviors with good dynamic performance. A 500W experimental prototype of stand-alone photovoltaic power system was built in the lab. Experimental results are shown to verify the effectiveness of the proposed power management strategy.

Fuzzy neural control of a hybrid fuel cell/battery distributed power generation system

Abstract: An innovative control strategy is proposed of hybrid distributed generation (HDG) systems, including solid oxide fuel cell (SOFC) as the main energy source and battery energy storage as the auxiliary power source. The overall configuration of the HDG system is given, and dynamic models for the SOFC power plant, battery bank and its power electronic interfacing are briefly described, and controller design methodologies for the power conditioning units and fuel cell to control the power flow from the hybrid power plant to the utility grid are presented. To distribute the power between power sources, the fuzzy switching controller has been developed. Then, a Lyapunov based-neuro fuzzy algorithm is presented for designing the controllers of fuel cell power plant, DC/DC and DC/AC converters; to regulate the input fuel flow and meet a desirable output power demand. Simulation results are given to show the overall system performance including load-following and power management of the system.