System operation with high wind penetration

The European Union has committed to reduce the equivalent carbon dioxide emissions by 8% of the 1990 level by the end of 2012. To meet the objective, the member states have financially encouraged the development of renewable energy especially wind power. Locally, this results in some of the highest wind power penetration levels in the world. This paper discusses the transmission challenges of Denmark, Spain, Germany and Ireland. With increasing wind capacity, the transmission system operators (TSOs) became concerned about the impact of high levels of wind generation on system stability. The integration of wind power has been hampered by the lack of suitable dynamic models for use in transient stability programs. The number of different turbine technologies used increased the complexity of the modeling problems.     

The role of hydrogen in high wind energy penetration electricity systems: The Irish case

The deployment of wind energy is constrained by wind uncontrollability, which poses operational problems on the electricity supply system at high penetration levels, lessening the value of wind-generated electricity to a significant extent. This paper studies the viability of hydrogen production via electrolysis using wind power that cannot be easily accommodated on the system. The potential benefits of hydrogen and its role in enabling a large penetration of wind energy are assessed, within the context of the enormous wind energy resource in Ireland. The exploitation of this wind resource may in the future give rise to significant amounts of surplus wind electricity, which could be used to produce hydrogen, the zero-emissions fuel that many experts believe will eventually replace fossil fuels in the transport sector. In this paper the operation of a wind powered hydrogen production system is simulated and optimised. The results reveal that, even allowing for significant cost-reductions in electrolyser and associated balance-of-plant equipment, low average surplus wind electricity cost and a high hydrogen market price are also necessary to achieve the economic viability of the technology. These conditions would facilitate the installation of electrolysis units of sufficient capacity to allow an appreciable increase in installed wind power in Ireland. The simulation model was also used to determine the CO₂ abatement potential associated with the wind energy/hydrogen production.     

Pumped storage in systems with very high wind penetration

This paper examines the operation of the Irish power system with very high levels of wind energy, with and without pumped storage. A unit commitment model which accounts for the uncertainty in wind power is used. It is shown that as wind penetration increases, the optimal operation of storage depends on wind output as well as load. The main benefit from storage is shown to be a decrease in wind curtailment. The economics of the system are examined to find the level at which storage justifies its capital costs and inefficiencies. It is shown that the uncertainty of wind makes the option of storage more attractive. The size of the energy store has an impact on results. At lower levels of installed wind (up to approximately 50% of energy from wind in Ireland), the reduction in curtailment is insufficient to justify building storage. At greater levels of wind, storage reduces curtailment sufficiently to justify the additional capital costs. It can be seen that if storage replaces OCGTs in the plant mix instead of CCGTs, then the level at which it justifies itself is lower. Storage increases the level of carbon emissions at wind penetration below 60%.     

The wind potential impact on the maximum wind energy penetration in autonomous electrical grids

According to long-term wind speed measurements the Aegean Archipelago possesses excellent wind potential, hence properly designed wind energy applications can substantially contribute to fulfill the energy requirements of the island societies. On top of this, in most islands the electricity production cost is extremely high, while significant insufficient power supply problems are often encountered, especially during the summer. Unfortunately, the stochastic behaviour of the wind and the important fluctuations of daily and seasonal electricity load pose a strict penetration limit for the contribution of wind energy in the corresponding load demand. The application of this limit is necessary in order to avoid hazardous electricity grid fluctuations and to protect the existing thermal power units from operating near or below their technical minima. In this context, the main target of the proposed study is to present an integrated methodology able to estimate the maximum wind energy penetration in autonomous electrical grids on the basis of the available wind potential existing in the Aegean Archipelago area. For this purpose a large number of representative wind potential types have been investigated and interesting conclusions have been derived.     

Determining optimal electricity technology mix with high level of wind power penetration

Notwithstanding its variability and limited controllability, wind power is expected to contribute strongly to electricity generation from renewable energy sources in the coming decades. Treating wind power as non-dispatchable by subtracting its output from the original load profile, results in a net load profile, which must be covered by conventional power generation. The screening curve methodology is a first approximation to find the optimal generation technology mix, based on relative cost levels. However, increased variability of the net load profile, due to wind power generation, strongly influences system operation. Therefore a static linear programming investment model is developed to determine the optimal technology mix. This alternative methodology shows a reduced capacity of inflexible generation after including operational constraints to properly account for net load variability. In order to illustrate this methodology, an example is set up, showing the sensitivity with respect to ramp rates of conventional generation, transmission interconnection and energy storage. The comparison of those different sources of system flexibility suggests that energy storage facilities better facilitate the integration of wind power generation.     

考虑风速相关性的风电接入能力分析

同一地区的风电场一般建立在相互接近的地理位置上,因此其风速往往呈现出一定的相关性。采用Copula函数建立多风电场的风速相关性模型,继而生成具有相关性的风速分布样本空间。考虑风速的随机性与相关性,应用机会约束规划理论,在满足系统安全可靠运行的前提下,以系统可接入的风电机组装机容量最大化作为优化目标,建立了计算风电穿透功率极限的概率最优潮流模型,并采用一种基于随机模拟技术的粒子群优化算法进行求解。以IEEE30节点测试系统为算例,分析风速相关性、风电场接入点和机会约束置信水平对风电接入能力的影响,结果验证了所提模型与算法的合理性与可行性。     

Demand side resource operation on the Irish power system with high wind power penetration

The utilisation of demand side resources is set to increase over the coming years with the advent of advanced metering infrastructure, home area networks and the promotion of increased energy efficiency. Demand side resources are proposed as an energy resource that, through aggregation, can form part of the power system plant mix and contribute to the flexible operation of a power system. A model for demand side resources is proposed here that captures its key characteristics for commitment and dispatch calculations. The model is tested on the all island Irish power system, and the operation of the model is simulated over one year in both a stochastic and deterministic mode, to illustrate the impact of wind and load uncertainty. The results illustrate that demand side resources can contribute to the efficient, flexible operation of systems with high penetrations of wind by replacing some of the functions of conventional peaking plant. Demand side resources are also shown to be capable of improving the reliability of the system, with reserve capability identified as a key requirement in this respect.     

Modelling the existing Irish energy-system to identify future energy costs and the maximum wind penetration feasible

In this study a model of the Irish energy-system was developed using EnergyPLAN based on the year 2007, which was then used for three investigations. The first compares the model results with actual values from 2007 to validate its accuracy. The second illustrates the exposure of the existing Irish energy-system to future energy costs by considering future fuel prices, CO₂ prices, and different interest rates. The final investigation identifies the maximum wind penetration feasible on the 2007 Irish energy-system from a technical and economic perspective, as wind is the most promising fluctuating renewable resource available in Ireland. It is concluded that the reference model simulates the Irish energy-system accurately, the annual fuel costs for Ireland's energy could increase by approximately 58% from 2007 to 2020 if a business-as-usual scenario is followed, and the optimum wind penetration for the existing Irish energy-system is approximately 30% from both a technical and economic perspective based on 2020 energy prices. Future studies will use the model developed in this study to show that higher wind penetrations can be achieved if the existing energy-system is modified correctly. Finally, these results are not only applicable to Ireland, but also represent the issues facing many other countries.     

Offshore wind energy prospects

In last two years offshore wind energy is becoming a focal point of national and non national organizations particularly after the limitations of fossil fuel consumption, adopted by many developed countries after Kyoto conference at the end of 1997 on global climate change. North Europe is particularly interested in offshore for the limited land areas still available, due to the intensive use of its territory and its today high wind capacity. Really the total wind capacity in Europe could increase from the 1997 value of 4450 MW up to 40 000 MW within 2010, according the White Paper 1997 of the European Commission; a significant percentage (25%) could be sited offshore up to 10 000 MW, because of close saturation of the land sites at that time. World wind capacity could increase from the 1997 value of 7200 MW up to 60 000 MW within 2010 with a good percentage (20%) offshore 12 000 MW. In last seven years wind capacity is shallow waters of coastal areas has reached 34 MW. Five wind farms are functioning in the internal seas of Netherlands, Denmark, Sweden; however such siting is mostly to be considered as semi-offshore condition. Wind farms in real offshore sites, open seas with waves and water depth over 10 m, are now proposed in North Sea at 10–20 km off the coasts of Netherland, Denmark using large size wind turbine (1–2 MW). In 1997 an offshore proposal was supported in Netherland by Greenpeace after the OWEMES '97 seminar, held in Italy on offshore wind in the spring 1997. A review is presented in the paper of the European offshore wind programs with trends in technology, economics and siting effects.     

Financing for wind energy

This paper outlines the method used in Northern Ireland to finance the generation of electricity from renewable sources in general and wind power in particular.     

趣谈风能利用

一帆风顺、风调雨顺、风和日丽、狂风暴雨、风雨同舟、微风荡漾……人们每天都在谈论风。风是我们最常见的自然现象之一。那么,风是怎样产生的呢?太阳和风     

风 风能 风力发电——21世纪新型清洁能源

一风的一般属性１风的形成风是人们非常熟悉的一种自然现象，人人都能感觉到它的存在。春风和煦，给万物带来生机；夏风吹拂，使人心旷神怡；秋风送爽，带来丰收的喜悦；冬风呼啸，迎来漫天飞雪。那么风是怎样形成的呢？众所周知，人类生活的地球表面被大气所包围，来自太阳的辐射不断传送到地球表面，因太阳辐射受热情况不同，地球表面各处的气温不同。在影响气压高低的因素中，气温起着最重要的作用。温度高的地区空气受热上升，气压减小；温度低的地方，空气下降，气压增大，于是产生了气压差。和水往低处流一样，空气也从气压高处向气压…     

Assessing the lifecycle greenhouse gas emissions from solar PV and wind energy: A critical meta-survey

This paper critically screens 153 lifecycle studies covering a broad range of wind and solar photovoltaic (PV) electricity generation technologies to identify 41 of the most relevant, recent, rigorous, original, and complete assessments so that the dynamics of their greenhouse gas (GHG) emissions profiles can be determined. When viewed in a holistic manner, including initial materials extraction, manufacturing, use and disposal/decommissioning, these 41 studies show that both wind and solar systems are directly tied to and responsible for GHG emissions. They are thus not actually emissions free technologies. Moreover, by spotlighting the lifecycle stages and physical characteristics of these technologies that are most responsible for emissions, improvements can be made to lower their carbon footprint. As such, through in-depth examination of the results of these studies and the variations therein, this article uncovers best practices in wind and solar design and deployment that can better inform climate change mitigation efforts in the electricity sector.     

Exploring the impact on cost and electricity production of high penetration levels of intermittent electricity in OECD Europe and the USA,results for wind energy

In this study we explore for the USA and OECD Europe (OECD Europe includes the countries that participate in the Organisation of Economic Cooperation and Development, among which Western Europe, USA and Japan) dynamic changes in electricity production, cost and CO₂ emissions when intermittent electricity sources are used with increasing penetration levels. The methodology developed can be applied for both solar photovoltaic (PV) and wind energy. Here the focus of the results is on penetration of wind electricity in the electricity system as simulated in a long-term model experiment in which the electricity demand is kept constant over time. All important parameter are included in a sensitivity analysis. With increasing penetration levels the cost reduction of wind electricity caused by upscaling and technological learning is counteracted by the cost increase due to (1) the need for additional back-up capacity, (2) the need to generate wind electricity at less favourable sites, and (3) discarded wind electricity because of supply–demand mismatch. This occurs after about 20% wind electricity production as percentage of current electricity production. At this level about 500 (OECD Europe) and 750 (USA) TWh yr⁻¹ wind electricity is absorbed in the system with the electricity demand of the year 2000. Wind electricity is found to be discarded when the production is about 55 (USA) to 10 times (OECD Europe) the present electricity produced from wind power. Beyond 30% of present electricity production, cost increases most significantly because of discarded wind electricity, excluding storage. In both regions the use of wind electricity would mainly avoid use of natural gas. The CO₂ emissions abatement costs range from 14 (OECD Europe) to 33 (USA) $ per ton CO₂ differ in both regions due to a faster wind electricity cost increase in OECD Europe.     

Modelling of energy systems with a high percentage of CHP and wind power

This paper presents the energy system analysis model EnergyPLAN, which has been used to analyse the integration of large scale wind power into the national Danish electricity system. The main purpose of the EnergyPLAN model is to design suitable national energy planning strategies by analysing the consequences of different national energy investments. The model emphasises the analysis of different regulation strategies and different market economic optimisation strategies.At present wind power supply 15% of the Danish electricity demand and ca 50% is produced in CHP (combined heat and power production). The model has been used in the work of an expert group conducted by the Danish Energy Agency for the Danish Parliament. Results are included in the paper in terms of strategies, in order to manage the integration of CHP and wind power in the future Danish energy supply in which more than 40% of the supply is expected to come from wind power.     

Production price of hydrogen from grid connected electrolysis in a power market with high wind penetration.

In liberalized power markets, there are significant power price fluctuations due to independently varying changes in demand and supply, the latter being substantial in systems with high wind power penetration. In such systems, hydrogen production by grid connected electrolysis can be cost optimized by operating an electrolyzer part time. This paper presents a study on the minimization of the hydrogen production price and its dependence on estimated power price fluctuations. The calculation of power price fluctuations is based on a parameterization of existing data on wind power production, power consumption and power price evolution in the West Danish power market area. The price for hydrogen is derived as a function of the optimal electrolyzer operation hours per year for four different wind penetration scenarios. It is found to amount to 0.41–0.45 €/Nm³. The study further discusses the hydrogen price sensitivity towards investment costs and the contribution from non-wind power sources.     

Assessing wind uncertainty impact on short term operation scheduling of coordinated energy storage systems and thermal units

Renewable resources, especially wind power, are widely integrated into the power systems nowadays. Managing uncertainty of the large scale wind power is often known as one of the most challenging issues in the power system operation scheduling. Additionally, energy storage systems (ESSs) have been widely investigated in the power systems owing to their valuable applications, especially renewable energy smoothing and time shift. In this paper, a stochastic unit commitment (UC) model is proposed to assess the impact of the wind uncertainty impact on ESSs and thermal units schedule in UC problem. Wind uncertainty is modeled based on the two measures. First, the wind penetration level is changed with respect to the basic level. Second, the wind forecasting error is modeled through a normal probability distribution function with different variances. The ESSs are modeled based on several technical characteristics and optimally scheduled considering different levels of the wind penetration and forecasting accuracies. The proposed formulation is a stochastic mixed integer linear programming (SMILP) and solved using GAMS software. Simulation results demonstrate that the wind uncertainty have a considerable impact on operation cost and ESSs schedule while proposed optimum storage scheduling through the stochastic programming will reduce the daily operational cost considerably.     

The economics of wind energy

This article presents the outcomes of a recent study carried out among wind energy manufacturers and developers regarding the current generation costs of wind energy projects in Europe, the factors that most influence them, as well as the reasons behind their recent increase and their expected future evolution. The research finds that the generation costs of an onshore wind farm are between 4.5 and 8.7 €cent/kWh; 6–11.1 €cent/kWh when located offshore, with the number of full hours and the level of capital cost being the most influencing elements. Generation costs have increased by more than 20% over the last 3 years mainly due to a rise of the price of certain strategic raw materials at a time when the global demand has boomed. However, the competitive position of wind energy investments vis-à-vis other technologies has not been altered. In the long-term, one would expect production costs go down; whether this will be enough to offset the higher price of inputs will largely depend on the application of correct policies, like R&D in new materials, O&M with remote-control devices, offshore wind turbines and substructures; introduction of advanced siting and forecasting techniques; access to adequate funding; and long-term legal stability.