Generation unit sizing and cost analysis for stand-alone wind,photovoltaic, and hybrid wind/PV systems

This paper presents the results of investigations on the application of wind, photovoltaic (PV), and hybrid wind/PV power generating systems for utilization as stand-alone systems. A simple numerical algorithm has been developed for generation unit sizing. It has been used to determine the optimum generation capacity and storage needed for a stand-alone, wind, PV, and hybrid wind/PV system for an experimental site in a remote area in Montana with a typical residential load. Generation and storage units for each system are properly sized in order to meet the annual load and minimize the total annual cost to the customer. In addition, an economic analysis has been performed for the above three scenarios and is used to justify the use of renewable energy versus constructing a line extension from the nearest existing power line to supply the load with conventional power. Annual average hourly values for load, wind speed, and insolation have been used     

A systems approach for sizing a stand-alone residential PEMFC power system

Polymer electrolyte membrane fuel cells (PEMFCs) show great promise in portable, automotive, and stationary applications. They have reached the test and demonstration phase in automotive and power markets today. This paper is focused on a stand-alone residential PEMFC power system that provides the electricity needs of the house. A novel stochastic sizing methodology is developed that considers both fuel cell system dynamics and residential load dynamics in overall system sizing for the stand-alone residential fuel cell power system. Understanding the nature of demand side is critical in stand-alone system sizing. Thus, experimental measurements have been completed to capture the load side dynamics in detail. No such data is found in the current literature. The Threshold Bootstrap method is used to model the residential load demand and to produce many realistic load profiles. Matlab/Simulink is used to run system simulations to determine system sizes based on parameters defined through a designed experiment. Comparison between the proposed sizing method and a possible worst case scenario sizing is given. The new sizing methodology can be used together with sophisticated demand analysis programs to obtain customized sizing for each user as stand-alone power systems become more viable.     

A mobile renewable house using PV/wind/fuel cell hybrid power system

A photovoltaic/wind/fuel cell hybrid power system for stand-alone applications is proposed and demonstrated with a mobile house. This concept shows that different renewable sources can be used simultaneously to power off-grid applications. The presented mobile house can produce sufficient power to cover the peak load. Photovoltaic and wind energy are used as primary sources and a fuel cell as backup power for the system. The power budgeting of the system is designed based on the local data of solar radiation and wind availability. Further research will focus on the development of the data acquisition system and the implementation of automatic controls for power management.     

Current status of research on optimum sizing of stand-alone hybrid solar–wind power generation systems

Solar and wind energy systems are omnipresent, freely available, environmental friendly, and they are considered as promising power generating sources due to their availability and topological advantages for local power generations. Hybrid solar–wind energy systems, uses two renewable energy sources, allow improving the system efficiency and power reliability and reduce the energy storage requirements for stand-alone applications. The hybrid solar–wind systems are becoming popular in remote area power generation applications due to advancements in renewable energy technologies and substantial rise in prices of petroleum products. This paper is to review the current state of the simulation, optimization and control technologies for the stand-alone hybrid solar–wind energy systems with battery storage. It is found that continued research and development effort in this area is still needed for improving the systems’ performance, establishing techniques for accurately predicting their output and reliably integrating them with other renewable or conventional power generation sources.     

Impact of load management on reliability assessment of grid independent PEM Fuel Cell Power Plants

In this paper, operating benefits from demand-side load management are evaluated for a Proton Exchange Membrane (PEM) Fuel Cell Power Plant (FCPP). For reliability modeling and evaluation of the PEM FCPP, a state-space generation model for a stand-alone PEM fuel cell that calculates the system availability and the expected energy not supplied (EENS) index has been developed. A systematic technique and detailed computer simulation software for a stand-alone PEM fuel cell station reliability assessment have been built. The suggested technique can be used for practical engineering applications to provide information for stand-alone FC generating station planning, design, and operation. The simulation results are obtained using the MATLAB software for a 5 kW stand-alone PEM fuel cell that supplies a typical residential house.     

Pre-feasibility study of stand-alone hybrid energy systems for applications in Newfoundland

A potential solution for stand-alone power generation is to use a hybrid energy system in parallel with some hydrogen energy storage. In this paper, a pre-feasibility study of using hybrid energy systems with hydrogen as an energy carrier for applications in Newfoundland, Canada is explained. Various renewable and non-renewable energy sources, energy storage methods and their applicability in terms of cost and performance are discussed. HOMER is used as a sizing and optimization tool. Sensitivity analysis with wind speed data, solar radiation level, diesel price and fuel cell cost was done. A remote house having an energy consumption of 25 kW h/d with a 4.73 kW peak power demand was considered as the stand-alone load. It was found that, a wind–diesel–battery hybrid system is the most suitable solution at present. However, with a reduction of fuel cell cost to 15% of its current value, a wind–fuel cell system would become a superior choice. Validity of such projection and economics against conventional power sources were identified. Sizing, performance and various cost indices were also analyzed in this paper.     

Alternative energy facilities based on site matching and generation unit sizing for remote area power supply

This paper presents the decision support technique and influencing factors in the design of an integrated solar-wind power system for stand-alone applications. Results of investigations on application of alternative energy facility like wind, photovoltaic (PV), and Integration of wind–PV power generating systems for Remote Area Power Supply have been presented. A weather model-based site matching of equipment and a simple numerical algorithm for generation unit sizing have been presented. The program has been used to determine the optimum generation capacity and storage needs for a stand-alone Wind, PV, and integrated wind–PV system for a remote site in India (Sukhalai situated near Suktawa in Hoshangabad district of Madhya Pradesh) that satisfies a typical load. Generation and storage units for each system are properly sized in order to meet the annual load demand for the above three scenarios. Annual average hourly values for load, wind speed, and insolation have been used for analysis. The results are used to justify the use of renewable energy source as a reliable option for remote areas.     

Power quality improvement of a stand-alone power system subjected to various disturbances

In wind-diesel stand-alone power systems, the disturbances like random nature of wind power, turbulent wind, sudden changes in load demand and the wind park disconnection effect continuously the system voltage and frequency. The satisfactory operation of such a system is not an easy task and the control design has to take in to account all these subtleties. For maintaining the power quality, generally, a short-term energy storage device is used. In this paper, the performance of a wind-diesel system associated with a superconducting magnetic energy storage (SMES) system is studied. The effect of installing SMES at wind park bus/load bus, on the system performance is investigated. To control the exchange of real and reactive powers between the SMES unit and the wind-diesel system, a control strategy based on fuzzy logic is proposed. The dynamic models of the hybrid power system for most common scenarios are developed and the results presented.     

Performance characterization of an indoor air source heat pump water heater for residential applications in Canada

Air source heat pump water heater (ASHPWH) is a relatively new addition to delivering hot water at reasonably high efficiency. ASHPWH systems have achieved significant acceptance for mild to warm climate regions where space heating is minimal or none. However, limited performance mapping is available on these water heaters in extreme cold climatic conditions, such as Canada. The paper has examined the long‐term performance of this technology in Canadian context. The investigation has established the performance characteristics of ASHPWH unit through a series of pre‐defined indoor tests and theoretical simulations. The coefficient of performance and other critical parameters of ASHPWH were established and discussed in detail. A model was developed, validated, and used to show the impact of such type of water heater on the overall energy consumption in the house. The results indicate that the summer cooling decreases and the winter heating increases in the house with an indoor ASHPWH unit. Nevertheless, the net effect leads to 21.3% reduction in the total electricity consumption of the house (space heating, cooling, and water heating). Research provided an accurate performance prediction of ASHPWHs for year‐round applications in Canadian homes.     

A probabilistic method for the evaluation of the reliability ofstand alone wind energy systems

The author describes a probabilistic method for the computation of the loss of load probability and the expected unserved energy of a stand-alone wind energy system. The system consists of a wind generator and a storage battery supplying the consumer load. The statistics of the surplus generation (excess wind generation over load demand) time series are computed and used for the calculation of the desired reliability indices. It is shown, that in the probability computations, the serial correlation of the surplus generation cannot be ignored. The performance of the developed method is demonstrated with computational results. Some results useful for the design of stand-alone wind energy systems are also presented     

A current and future state of art development of hybrid energy system using wind and PV-solar: A review

The wind and solar energy are omnipresent, freely available, and environmental friendly. The wind energy systems may not be technically viable at all sites because of low wind speeds and being more unpredictable than solar energy. The combined utilization of these renewable energy sources are therefore becoming increasingly attractive and are being widely used as alternative of oil-produced energy. Economic aspects of these renewable energy technologies are sufficiently promising to include them for rising power generation capability in developing countries. A renewable hybrid energy system consists of two or more energy sources, a power conditioning equipment, a controller and an optional energy storage system. These hybrid energy systems are becoming popular in remote area power generation applications due to advancements in renewable energy technologies and substantial rise in prices of petroleum products. Research and development efforts in solar, wind, and other renewable energy technologies are required to continue for, improving their performance, establishing techniques for accurately predicting their output and reliably integrating them with other conventional generating sources. The aim of this paper is to review the current state of the design, operation and control requirement of the stand-alone PV solar–wind hybrid energy systems with conventional backup source i.e. diesel or grid. This Paper also highlights the future developments, which have the potential to increase the economic attractiveness of such systems and their acceptance by the user.     

Incorporation of a new wind turbine generating system model into distribution systems load flow analysis

This paper describes a new model for wind turbine generating systems (WTGSs) that is widely used as distributed generation sources. The model is developed by using the bi‐quadratic equation, which is generally used for the calculation of the line voltages in distribution systems' load flow analysis, and facilitates computation of real and reactive power outputs of the WTGSs for a specified wind speed and terminal voltage. The developed model is validated with an experimental setup composed by an induction generator coupled with an induction motor as a prime mover. In addition to that, measured values are also compared with the calculated values, obtained by using the turbine models found in the literature. The incorporation of the developed model into some well‐known distribution systems' load flow algorithms is detailed. The effect of WTGSs on the power losses, voltage profile of radial distribution systems are evaluated for the sample test systems. Additionally, the performance of the load flow algorithms with the new model are examined and found to be robust and reliable. Copyright © 2008 John Wiley & Sons, Ltd.     

Utility scale hybrid wind–solar thermal electrical generation: A case study for Minnesota

The performance of a hybrid wind–solar power plant in southwestern Minnesota is modeled for a 2-yr period using hourly wind and solar insolation data. The wind portion of the plant consists of four interconnected wind farms within a radius of 90 km. The solar component of the plant is a parabolic trough solar thermal electric generating system using a heat transfer fluid that drives a steam turbine. The market value of energy produced, retail value of energy produced, and levelized cost of energy of the hybrid plant are compared to those of an energy equivalent wind-only plant. Results show that adding solar thermal electric generating capacity to a wind farm rather than expanding with additional wind capacity provides cost–benefit trade-offs that will continue to change as the two technologies evolve. At the present time, we find that capital cost and levelized cost of energy favor a wind-only plant while electric load matching favors a hybrid wind–solar plant. Regional differences in the solar resource in the US influence the economic viability of the hybrid plant, and a comparison using the present model is made with one location in the Southwest. The hourly data analysis presented here is a possible tool for evaluating the overall economic feasibility and generating characteristics for a hybrid wind–solar thermal electric power plant for any location with available wind, solar, electric load, and price data.     

基于改进型运行策略的独立微电网容量优化配置

建立独立微电网对于解决离岸岛屿等传统供电不便地区的可靠自主供用电问题具有非常显著的实用性。针对风/光/蓄/柴独立微电网,提出了一种考虑系统净负荷大小的改进型运行控制策略,通过权重法将系统经济性和环保性指标整合并加入可靠性经济惩罚共同作为优化目标,考虑多种约束条件,建立基于改进型运行策略的风/光/蓄/柴独立微电网容量优化配置模型,并采用混合量子遗传算法(HQGA)对我国沿海某岛地区独立微网实施优化配置。结果表明,与采用常规运行策略的配置结果相比,所提运行策略具有正确性和优越性。     

An analytical study of a hybrid wind-passive solar system

This paper presents the results of an analytical performance and economic evaluation of a combined passive solar and wind powered residential heating and electrical energy system. Simulated in a New England wind and weather environment, the modeled system is based on the coupling of a vertical axis wind turbine with a super-insulated passive solar house. The analytical model is composed of four major sections: (1) residential heating and energy load; (2) wind turbine generator system; (3) energy system performance model; and (4) life-cycle costing economic analysis. Results for the heating, electrical supply and economic performance of the system are presented, varying such key parameters as residence window area, insulation, storage size, wind turbine size, and site average wind speed. These results show that when sited in adequate wind regimes (average wind speed greater than 5.4 m/sec (12 mph)) and coupled with super-insulated passive structures, wind turbines can provide significant fractions of the electrical and heating requirements in the New England environment.     

Design of a cost-effective on-grid hybrid wind–hydrogen based CHP system using a modified heuristic approach

An economic model and optimization procedure is developed in this paper for grid-connected hybrid wind–hydrogen combined heat and power systems for residential applications in northeastern Iran. The model considers various significant factors: energy production cost, electrical trade with local grid, electrical power generation from the wind/hydrogen energy system, thermal recovery from the fuel cell, and maintenance. Also, various tariffs for purchasing and selling electrical energy from the local grid are considered for the hybrid system operation. The optimization objective is to minimize the system total cost subject to relevant constraints for residential applications. To achieve this aim, an efficient optimization method is proposed based on particle swarm optimization. The proposed algorithm performance is compared with that for the imperialist competition algorithm. The results show that the hybrid system is the most cost-effective for the residential load, and the results of the proposed algorithm are more promising than those for the alternative algorithm.     

Methodology for optimal sizing of stand-alone photovoltaic/wind-generator systems using genetic algorithms

A methodology for optimal sizing of stand-alone PV/WG systems is presented. The purpose of the proposed methodology is to suggest, among a list of commercially available system devices, the optimal number and type of units ensuring that the 20-year round total system cost is minimized subject to the constraint that the load energy requirements are completely covered, resulting in zero load rejection. The 20-year round total system cost is equal to the sum of the respective components capital and maintenance costs. The cost (objective) function minimization is implemented using genetic algorithms, which, compared to conventional optimization methods such as dynamic programming and gradient techniques, have the ability to attain the global optimum with relative computational simplicity. The proposed method has been applied for the design of a power generation system which supplies a residential household. The simulation results verify that hybrid PV/WG systems feature lower system cost compared to the cases where either exclusively WG or exclusively PV sources are used.     

SIZING AND TECHNO-ECONOMICAL OPTIMIZATION FOR HYBRID SOLAR PHOTOVOLTAIC/WIND POWER SYSTEMS WITH BATTERY STORAGE

A general methodology is presented for the sizing and optimization of renewable power supply systems, including hybrids such as those with solar photovoltaic and wind power components. The technical and economic optimum configurations are found by reference to periods over which the average resource (e.g. wind/solar) is least or the average load demand is greatest. For stand-alone systems, the annual autonomy is an important further design factor. This is the fraction of time for which the specified load can be met. The optimization seeks the least expensive system configuration which achieves the required autonomy level. It is the autonomy level which largely determines the size of battery storage capacity required. A system performance simulation procedure, with an hourly time-step, is used to obtain the autonomy levels of potentially optimum arrangements as the battery size is varied. Illustrative examples of the use of the method employ annual and monthly averaging periods, although any other period may be used. Data refer to the particular location and load pattern for an existing hybrid system, but the method is quite generally applicable. © 1997 by John Wiley & Sons, Ltd.     

Optimal dispatch strategy in remote hybrid power systems

For small villages in developing countries, local stand-alone power systems are often more cost-effective than utility grid extension. Various combinations of wind turbine generators, photovoltaic arrays, diesel gensets, and batteries—remote hybrid power systems—may be preferred to diesel-only systems. Dispatch strategy is the aspect of control strategy that pertains to energy flows among components. In systems with both batteries and diesel genset(s), dispatch affects the life-cycle cost through both the fuel usage and the battery life. In this study, dispatch strategies are compared using (1) an analysis of cost trade-offs, (2) a simple, quasi-steady-state time-series model, and finally (3) HYBRID2, a more sophisticated stochastic time-series model. An idealized predictive dispatch strategy, based on assumed perfect knowledge of future load and wind conditions, is developed and used as a benchmark in evaluating simple, non-predictive strategies. The results illustrate the nature of the optimal strategy and indicate that one of two simple diesel dispatch strategies—either load-following or full power for a minimum run time—can, in conjunction with the frugal use of stored energy (the Frugal Discharge Strategy), be virtually as cost-effective as the Ideal Predictive Strategy. The optimal choice of these two simple charging strategies is correlated to three dimensionless parameters, yielding a generalized dispatch design chart for an important class of systems.     

Model for energy conversion in renewable energy system with hydrogen storage

A dynamic model for a stand-alone renewable energy system with hydrogen storage (RESHS) is developed. In this system, surplus energy available from a photovoltaic array and a wind turbine generator is stored in the form of hydrogen, produced via an electrolyzer. When the energy production from the wind turbine and the photovoltaic array is not enough to meet the load demand, the stored hydrogen can then be converted by a fuel cell to produce electricity. In this system, batteries are used as energy buffers or for short time storage. To study the behavior of such a system, a complete model is developed by integrating individual sub-models of the fuel cell, the electrolyzer, the power conditioning units, the hydrogen storage system, and the batteries (used as an energy buffer). The sub-models are valid for transient and steady state analysis as a function of voltage, current, and temperature. A comparison between experimental measurements and simulation results is given. The model is useful for building effective algorithms for the management, control and optimization of stand-alone RESHSs.