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- PublicationApplication of wind generation capacity credits in the Great Britain and Irish systemsThe concept of capacity credit is widely used to quantify the contribution of renewable technologies to securing demand. This may be quantified in a number of ways; this paper recommends the use of Effective Load Carrying Capability (ELCC, the additional demand which the new generation can support without increasing system risk), with system risk being measured using Loss of Load Expectation (LOLE, this is calculated through direct use of historic time series for demand and wind load factor). The key benefit of this approach is that it automatically incorporates the available statistical information on the relationship between wind availability and demand during the hours of very high demand which are most relevant in assessing system adequacy risk. The underlying assumptions are discussed in detail, and a comparison is made with alternative calculation approaches; a theme running through the paper is the need to consider the assumptions carefully when presenting or interpreting risk assessment results. A range of applications of capacity credits from Great Britain and Ireland are presented; this includes presentation of effective plant margin, ensuring that the optimal plant mix secures peak demand in economic projection models, and the Irish capacity payments system. Finally, new results comparing capacity credit results from the Great Britain and Irish systems using the same wind data are presented. This allows the various factors which influence capacity credit results to be identified clearly. It is well known that increasing the wind load factor or demand level typically increases the calculated capacity credit, while increasing the installed wind capacity typically decreases its capacity credit (as a percentage of rated capacity). The new results also show that the width of the probability distribution for available conventional generating capacity, relative to the peak demand level, also has a strong influence on the results. This emphasises further that detailed understanding of risk model structures is vitally important in practical application.
- PublicationStochastic Optimization Model to Study the Operational Impacts of High Wind Penetrations in IrelandA stochastic mixed integer linear optimization scheduling model minimizing system operation costs and treating load and wind power production as stochastic inputs is presented. The schedules are updated in a rolling manner as more up-to-date information becomes available. This is a fundamental change relative to day-ahead unit commitment approaches. The need for reserves dependent on forecast horizon and share of wind power has been estimated with a statistical model combining load and wind power forecast errors with scenarios of forced outages. The model is used to study operational impacts of future high wind penetrations for the island of Ireland. Results show that at least 6000 MW of wind (34% of energy demand) can be integrated into the island of Ireland without significant curtailment and reliability problems.
2351Scopus© Citations 265
- PublicationCapacity value of wind power, calculation, and data requirements : the Irish power system caseThe capacity value of wind power indicates the extent to which wind power contributes to the generation system adequacy of a power system. The related data requirements may be subject to difficulties due to the temporal variability and spatial distribution of wind power in connection with the limited databases currently available. This paper presents a methodology to identify the minimal amount of data required for reliable studies. Based on wind power data of 74 stations in Ireland, covering up to ten years, the effects of different numbers of stations and different time periods of data on the capacity value are analyzed. The calculations are performed by means of a fast calculation code. The results show that at least four to five years of data in an hourly resolution are necessary for reliable studies and that 40 to 50 evenly distributed stations give an acceptable representation of the total wind power generation in Ireland.
1284Scopus© Citations 94
- PublicationCapacity value of wind powerPower systems are planned such that they have adequate generation capacity to meet the load, according to a defined reliability target. The increase in the penetration of wind generation in recent years has led to a number of challenges for the planning and operation of power systems. A key metric for generation system adequacy is the capacity value of generation. The capacity value of a generator is the contribution that a given generator makes to generation system adequacy. The variable and stochastic nature of wind sets it apart from conventional energy sources. As a result, the modeling of wind generation in the same manner as conventional generation for capacity value calculations is inappropriate. In this paper a preferred method for calculation of the capacity value of wind is described and a discussion of the pertinent issues surrounding it is given. Approximate methods for the calculation are also described with their limitations highlighted. The outcome of recent wind capacity value analyses in Europe and North America, along with some new analysis are highlighted with a discussion of relevant issues also given.
1931Scopus© Citations 268