Showing papers on "Stand-alone power system published in 2012"

A review of energy storage technologies for wind power applications

Abstract: Due to the stochastic nature of wind, electric power generated by wind turbines is highly erratic and may affect both the power quality and the planning of power systems. Energy Storage Systems (ESSs) may play an important role in wind power applications by controlling wind power plant output and providing ancillary services to the power system and therefore, enabling an increased penetration of wind power in the system. This article deals with the review of several energy storage technologies for wind power applications. The main objectives of the article are the introduction of the operating principles, as well as the presentation of the main characteristics of energy storage technologies suitable for stationary applications, and the definition and discussion of potential ESS applications in wind power, according to an extensive literature review.

Battery Energy Storage for Enabling Integration of Distributed Solar Power Generation

Abstract: As solar photovoltaic power generation becomes more commonplace, the inherent intermittency of the solar resource poses one of the great challenges to those who would design and implement the next generation smart grid. Specifically, grid-tied solar power generation is a distributed resource whose output can change extremely rapidly, resulting in many issues for the distribution system operator with a large quantity of installed photovoltaic devices. Battery energy storage systems are increasingly being used to help integrate solar power into the grid. These systems are capable of absorbing and delivering both real and reactive power with sub-second response times. With these capabilities, battery energy storage systems can mitigate such issues with solar power generation as ramp rate, frequency, and voltage issues. Beyond these applications focusing on system stability, energy storage control systems can also be integrated with energy markets to make the solar resource more economical. Providing a high-level introduction to this application area, this paper presents an overview of the challenges of integrating solar power to the electricity distribution system, a technical overview of battery energy storage systems, and illustrates a variety of modes of operation for battery energy storage systems in grid-tied solar applications. The real-time control modes discussed include ramp rate control, frequency droop response, power factor correction, solar time-shifting, and output leveling.

Economic Model Predictive Control for building climate control in a Smart Grid

Abstract: Model Predictive Control (MPC) can be used to control a system of energy producers and consumers in a Smart Grid. In this paper, we use heat pumps for heating residential buildings with a floor heating system. We use the thermal capacity of the building to shift the energy consumption to periods with low electricity prices. In this way the heating system of the house becomes a flexible power consumer in the Smart Grid. This scenario is relevant for systems with a significant share of stochastic energy producers, e.g. wind turbines, where the ability to shift power consumption according to production is crucial. We present a model for a house with a ground source based heat pump used for supplying thermal energy to a water based floor heating system. The model is a linear state space model and the resulting controller is an Economic MPC formulated as a linear program. The model includes forecasts of both weather and electricity price. Simulation studies demonstrate the capabilities of the proposed model and algorithm. Compared to traditional operation of heat pumps with constant electricity prices, the optimized operating strategy saves 25–35% of the electricity cost.

Assessment of economic viability for PV/wind/diesel hybrid energy system in southern Peninsular Malaysia

Abstract: This paper analyzed the potential implementation of hybrid photovoltaic (PV)/wind turbine/diesel system in southern city of Malaysia, Johor Bahru. HOMER (hybrid optimization model for electric renewable) simulation software was used to determine the technical feasibility of the system and to perform the economical analysis of the system. There were seven different system configurations, namely stand-alone diesel system, hybrid PV–diesel system with and without battery storage element, hybrid wind–diesel system with and without battery storage element, PV–wind–diesel system with and without storage element, will be studied and analyzed. The simulations will be focused on the net present costs, cost of energy, excess electricity produced and the reduction of CO 2 emission for the given hybrid configurations. At the end of this paper, PV–diesel system with battery storage element, PV–wind–diesel system with battery storage element and the stand-alone diesel system were analyzed based on high price of diesel.

Optimal Power Management of Residential Customers in the Smart Grid

Abstract: Recently intensive efforts have been made on the transformation of the world's largest physical system, the power grid, into a “smart grid” by incorporating extensive information and communication infrastructures. Key features in such a “smart grid” include high penetration of renewable and distributed energy sources, large-scale energy storage, market-based online electricity pricing, and widespread demand response programs. From the perspective of residential customers, we can investigate how to minimize the expected electricity cost with real-time electricity pricing, which is the focus of this paper. By jointly considering energy storage, local distributed generation such as photovoltaic (PV) modules or small wind turbines, and inelastic or elastic energy demands, we mathematically formulate this problem as a stochastic optimization problem and approximately solve it by using the Lyapunov optimization approach. From the theoretical analysis, we have also found a good tradeoff between cost saving and storage capacity. A salient feature of our proposed approach is that it can operate without any future knowledge on the related stochastic models (e.g., the distribution) and is easy to implement in real time. We have also evaluated our proposed solution with practical data sets and validated its effectiveness.

Grid integration of intermittent renewable energy sources using price-responsive plug-in electric vehicles

Abstract: Plug-in electric vehicles (PEVs) are expected to balance the fluctuation of renewable energy sources (RES). To investigate the contribution of PEVs, the availability of mobile battery storage and the control mechanism for load management are crucial. This study therefore combined the following: a stochastic model to determine mobility behavior, an optimization model to minimize vehicle charging costs and an agent-based electricity market equilibrium model to estimate variable electricity prices. The variable electricity prices are calculated based on marginal generation costs. Hence, because of the merit order effect, the electricity prices provide incentives to consume electricity when the supply of renewable generation is high. Depending on the price signals and mobility behavior, PEVs calculate a cost minimizing charging schedule and therefore balance the fluctuation of RES. The analysis shows that it is possible to limit the peak load using the applied control mechanism. The contribution of PEVs to improving the integration of intermittent renewable power generation into the grid depends on the characteristic of the RES generation profile. For the German 2030 scenario used here, the negative residual load was reduced by 15–22% and the additional consumption of negative residual load was between 34 and 52%.

Optimal Sizing of Hybrid Wind/PV/Diesel Generation in a Stand-Alone Power System Using Markov-Based Genetic Algorithm

Abstract: Owing to the Kyoto Protocol and the growing depletion of natural resources, renewable energies have attracted much attention. This paper considers 25-kW wind-turbine generator, 5-kW PV and 30-kW diesel generator as unit sizes for generation planning in a stand-alone power system. The investment cost (installation and unit costs) and fuel cost are minimized while retaining the reliability requirement and CO emission limit. First, the fuzzy-c-means (FCM) is employed to cluster the operation states for system load, wind-turbine generations (WTG), and PV in 8760 h. Then, the Markov models for the system load, WTG, and photovoltaic (PV) are established. The Markov models are embedded into the genetic algorithm to determine the optimal sizes for WTG, PV, and the diesel generator. The simulation results reveal that computation time can be reduced greatly while optimality can be still retained, compared with the traditional method using chronological data.

Standalone Hybrid Wind-Solar Power Generation System Applying Dump Power Control Without Dump Load

Abstract: This paper proposes a unique standalone hybrid power generation system, applying advanced power control techniques, fed by four power sources: wind power, solar power, storage battery, and diesel engine generator, and which is not connected to a commercial power system. Considerable effort was put into the development of active-reactive power and dump power controls. The result of laboratory experiments revealed that amplitudes and phases of ac output voltage were well regulated in the proposed hybrid system. Different power sources can be interconnected anywhere on the same power line, leading to flexible system expansion. It is anticipated that this hybrid power generation system, into which natural energy is incorporated, will contribute to global environmental protection on isolated islands and in rural locations without any dependence on commercial power systems.

Electricity storage for intermittent renewable sources

Abstract: With sufficient electricity storage capacity, any power production profile may be mapped onto any desired supply profile. We present a framework to determine the required storage power as a function of time for any power production profile, supply profile, and targeted system efficiency, given the loss characteristics of the storage system. We apply the framework to the electrochemical storage of intermittent renewable power, employing a simplifying linear response approximation that permits the entire efficiency behavior of the system to be described by a single scalar figure of merit—the discharge power capacity. We consider three exemplary grid supply scenarios: constant, grid-minus-baseload, and square wave; and two different production scenarios: wind with a capacity factor 32.5%, and solar photovoltaic (PV) with a capacity factor of 14%. For each of these six combinations of scenarios, the storage energy and discharge power capacity requirements are found for a range of system efficiencies. Significantly diminishing efficiency returns are found on increasing the discharge power capacity. Solid-electrode batteries are shown to have two orders of magnitude too little energy to power ratio to be well suited to the storage of intermittent renewable power.

Wind Power Electricity: The Bigger the Turbine, The Greener the Electricity?

Abstract: Wind energy is a fast-growing and promising renewable energy source. The investment costs of wind turbines have decreased over the years, making wind energy economically competitive to conventionally produced electricity. Size scaling in the form of a power law, experience curves and progress rates are used to estimate the cost development of ever-larger turbines. In life cycle assessment, scaling and progress rates are seldom applied to estimate the environmental impacts of wind energy. This study quantifies whether the trend toward larger turbines affects the environmental profile of the generated electricity. Previously published life cycle inventories were combined with an engineering-based scaling approach as well as European wind power statistics. The results showed that the larger the turbine is, the greener the electricity becomes. This effect was caused by pure size effects of the turbine (micro level) as well as learning and experience with the technology over time (macro level). The environment...

Planning and Operating Combined Wind-Storage System in Electricity Market

Abstract: The increasing penetration of renewable sources in power systems yields various issues in network operation. Most of them are related to uncertainties of energy production. In particular, the variability of wind source does not allow for accurate forecasting of power generation. Production plans may not be accomplished, incurring penalties for system unbalance. For this reason, the use of an energy storage system can improve integration of wind energy in production planning and dispatch. In this paper, an approach for planning and operating an energy storage system for a wind farm in the electricity market is proposed. To this purpose, electrochemical batteries are employed to compensate for generation variations in order to set up a reliable hourly delivery profile, complying with market requirements. The delivery plan can be settled according to energy prices, as well. Moreover, an economic feasibility analysis is carried out on the combined wind-storage system.

Switch: a planning tool for power systems with large shares of intermittent renewable energy.

Abstract: Wind and solar power are highly variable, so it is it unclear how large a role they can play in future power systems. This work introduces a new open-source electricity planning model—Switch—that i...

Potential of Heat Pumps for Demand Side Management and Wind Power Integration in the German Electricity Market

Abstract: Increasing power system flexibility by responsive demand is a central issue for the incorporation of higher levels of variable wind generation in future power systems. The electrification of the heat sector, except from energy efficiency gains, may offer a vast potential of new forms of flexible demand, by time-shifting of heat production in buildings. The assessment of this potential can, however, be performed only when the limitations imposed by the primary operation of the equipment (space heating) are realistically taken into account. In this paper, a methodology is presented for the quantification of the flexibility offered by the thermal storage of building stock equipped with heat pumps, to power systems with significant penetration of wind power. A model is proposed for the incorporation of the building stock thermal behavior as equivalent energy storage in electricity market models. At the same time, the model allows the coupling to a detailed dynamic thermal model of buildings for the assessment of the respective operational restrictions. The case study presents the results of a project for the evaluation of the flexibility offered by portfolios of high heat pump deployment in conjunction with high wind penetration scenarios for the future German electricity system.

Standalone Operation of Wind Turbine-Based Variable Speed Generators With Maximum Power Extraction Capability

Abstract: The application of variable speed wind generators in hybrid remote area power supply (RAPS) systems provides opportunities for improved voltage and frequency control together with maximum power point tracking (MPPT), where limited research outcomes exist. The study presented in this paper covers two such hybrid systems: 1) permanent magnet synchronous generator (PMSG) and 2) doubly fed induction generator (DFIG) as wind turbine technologies together with a battery storage and a dump load. The battery storage system and dump load are able to assist in maintaining the active power balance during over and under generation conditions as well as sudden load changes. Through simulation studies, it has been demonstrated that both RAPS systems are able to regulate the load side voltage and frequency within the acceptable limits while extracting the maximum power from wind, which is an inherent capability of variable speed generators. The two RAPS systems and their associated control strategies have been developed and their performance is investigated using SimPowerSystems blocksets in MATLAB.

Overview of energy storage systems for storing electricity from renewable energy sources in Saudi Arabia

Abstract: Renewable power (photovoltaic, solar thermal or wind) is inherently intermittent and fluctuating. If renewable power has to become a major source of base-load dispatchable power, electricity storage systems of multi-MW capacity and multi-hours duration are indispensable. An overview of the advanced energy storage systems to store electrical energy generated by renewable energy sources is presented along with climatic conditions and supply demand situation of power in Saudi Arabia. Based on the review, battery features needed for the storage of electricity generated from renewable energy sources are: low cost, high efficiency, long cycle life, mature technology, withstand high ambient temperatures, large power and energy capacities and environmentally benign. Although there are various commercially available electrical energy storage systems (EESS), no single storage system meets all the requirements for an ideal EESS. Each EESS has a suitable application range.

SmartCharge: cutting the electricity bill in smart homes with energy storage

Abstract: Market-based electricity pricing provides consumers an opportunity to lower their electric bill by shifting consumption to low price periods. In this paper, we explore how to lower electric bills without requiring consumer involvement using an intelligent charging system, called SmartCharge, and an on-site battery array to store low-cost energy for use during high-cost periods. SmartCharge's algorithm reduces electricity costs by determining when to switch the home's power supply between the grid and the battery array. The algorithm leverages a prediction model we develop, which forecasts future demand using statistical machine learning techniques. We evaluate SmartCharge in simulation using data from real homes to quantify its potential to lower bills in a range of scenarios. We show that typical savings today are 10-15%, but increase linearly with rising electricity prices. We also find that SmartCharge deployed at only 22% of 435 homes reduces the aggregate demand peak by 20%. Finally, we analyze SmartCharge's installation and maintenance costs. Our analysis shows that battery advancements, combined with an expected rise in electricity prices, have the potential to make the return on investment positive for the average home within the next few years.

Demand-Side Management in the Smart Grid: Information Processing for the Power Switch

Abstract: Over the course of several decades after their introduction, power systems merged into large interconnected grids to introduce redundancy and to leverage on a wider pool of generation resources and reserves. As the system grew in size and complexity, a cyberphysical infrastructure was progressively developed to manage it. Traditionally, general-purpose computing and communication resources have been used in power systems, specifically to serve two needs: 1) that of monitoring the safe operation of the grid and logistics of power delivery, and 2) that of gathering information required to dispatch the generation optimally and, later on, to operate the energy market.