Life cycle sustainability assessment of pumped hydro energy storage

At present, pumped hydro energy storage plays the dominant role in electrical energy storage. However, its development is clearly restricted by the topography and adverse impacts on local residents. Underground pumped hydro energy storage (UPHES) using abandoned mine pits not only can effectively remedy these drawbacks but is also constructive to the management of abandoned mine pits. In this paper, we firstly conduct a comprehensive analysis of conventional pumped hydro energy storage (CPHES) and UPHES, using life cycle sustainability assessment (LCSA). Sustainability indicators in this paper include economic indicators, environmental indicators, and social indicators. Among all the indicators, blue water footprint (BWF) and ecological footprint (EF) are included for the first time to assess the social performance of CPHES and UPHES. Then, this paper employs multi-attribute value theory (MAVT) and scenario analysis to evaluate the overall performance of energy storages. The results show that CPHES has better performance in economy and environment than UPHES because of the economies of scale, while the UPHES has better performance in social sustainability impact because of the absence of stages of excavation and backfilling. When using MAVT methodology, only when the weight for social indicator is three times higher than that of economy and environment; ie, the weight for social dimension is 0.6, and the weights for environmental and social dimension are 0.2; the score of UPHES is higher than CPHES.     

基于Multi-Agent遗传算法风电-抽水蓄能联合优化运行

文章以经济和环境的综合效益最大化为目标,建立风电-抽水蓄能联合优化运行模型,考虑抽水蓄能机组和火电机组的各种运行限制,研究不同权重因子下电网效益、风电利用率和机组的出力情况,并研究了求解所建立优化模型的多Agent遗传算法,通过算例仿真验证所建模型及方法的有效性和实用性。结果表明风电场与抽水蓄能电站配合,可以降低风电对电网的影响,提高电网消纳风电的能力,还能够对火电厂机组功率起到平滑作用。     

Techno-economic review of existing and new pumped hydro energy storage plant

There has been a renewed commercial and technical interest in pumped hydro energy storage (PHES) recently with the advent of increased variable renewable energy generation and the development of liberalized electricity markets. During the next 8 years over 7 GW of PHES capacity will be added to the European network while projects are also planned in the USA and Japan. This paper provides a review of existing and proposed PHES plant and discusses the technical and economic drivers for these developments. Current trends for new PHES development generally show that developers operating in liberalized markets are tending to repower, enhance projects or build ‘pump-back’ PHES rather than traditional ‘pure pumped storage’. Capital costs per kW for proposed PHES in the review region range between €470/kW and €2170/kW, however these costs are highly site and project specific. An emergence has also been observed in recent PHES developments of the use of variable speed technology. This technology, while incurring slightly higher capital costs, offers a greater range of operational flexibility and efficiency over conventional PHES. This paper has primarily been prompted by a lack of detailed information on PHES facilities worldwide and reviews current developments in the context of market and generation mix changes. The most recent large scale review of PHES faculties was undertaken by the American Society of Civil Engineers Hydro Power Task Committee on Pumped Storage in 1996. In the absence of data in the literature on new PHES plant development, this review draws primarily on publicly available information from utilities, government bodies and electricity regulators. In the same context this study is limited to a review region of the European Union, Japan and the United States as information on developments outside these areas is difficult to procure. This paper also gives a review of locations and proposed timelines for new PHES development and provides a thorough up-to-date overview of the development trends of this technology.     

Contribution of pumped hydro storage to integration of wind power in Kenya: An optimal control approach

This paper investigates the benefit of optimally integrating wind power in Kenya with pumped hydro storage. The approach includes development of an optimal control strategy to deploy paired wind and pumped hydro storage resources, for the Lake Turkana Wind Power project. The stochastic model, which maximizes expected revenue over the planning horizon, is developed taking into the consideration the structure and running of the Kenya electricity market. The 300 MW Lake Turkana Wind Power wind farm is simulated using wind speed data from Marsabit, which is in close proximity to the Lake Turkana region. From the simulation of the wind farm, we find that the daily pattern exhibited by the wind speeds, does not match the average daily load pattern. Pumped hydro storage reduces the systems total power output shortage by 46%. This approach to operation could alleviate the significant economic burden of the take-or-pay purchase agreement that led to the removal of financial backing of the project by the World Bank. The use of pumped hydro storage in conjunction with the wind farm is also found to increase the expected daily revenue of the wind farm by over ten thousand dollars.     

The economics of wind power with energy storage

We develop a nonlinear mathematical optimization program for investigating the economic and environmental implications of wind penetration in electrical grids and evaluating how hydropower storage could be used to offset wind power intermittence. When wind power is added to an electrical grid consisting of thermal and hydropower plants, it increases system variability and results in a need for additional peak-load, gas-fired generators. Our empirical application using load data for Alberta's electrical grid shows that costs of wind-generated electricity vary from $37 per MWh to $68/MWh, and depend primarily on the wind profiles of installed turbines. Costs of reducing CO₂ emissions are estimated to be $41–$56 per t CO₂. When pumped hydro storage is introduced in the system or the capacity of the water reservoirs is enhanced, the hydropower facility could provide most of the peak load requirements obviating the need to build large peak-load gas generators.     

Investment in wind power and pumped storage in a real options model

Promoting renewable energy has been a key ingredient in energy policy seeking to de-carbonize the energy mix and will continue to do so in the future given the European Union's high ambitions to further curb carbon emissions. A wide range of instruments has been suggested and implemented in various countries of the EU. A prominent policy promoting investment in renewable technologies is the use of feed-in tariffs, which has worked well at large scale in, e.g. Germany, but which has only been implemented in a very limited way in countries such as the UK.Being subject to environmental uncertainties, however, renewables cannot be seen in isolation: while renewables-based technologies such as wind and solar energy, for example, suffer from uncertain loads depending on environmental conditions, hydropower allows for the storage of water for release at peak prices, which can be treated as a premium (partially) offsetting higher upfront investment costs. In addition, electricity prices will respond to changes in electric capacity in the market, which is often neglected in standard investment models of the electricity sector.This paper contributes to the existing literature in two ways: it provides a review of a renewables-based technology in a specific policy context and provides additional insight by employing a real options approach to investigate the specific characteristics of renewables and their associated uncertainties in a stylized setting taking explicitly into account market effects of investment decisions. The prices of the model are determined endogenously by the supply of electricity in the market and by exogenous electricity price uncertainty. The inclusion of market effects allows us to capture the full impact of public incentives for companies to invest into wind power and hydro pumped storage installations.     

Operating characteristics of constant-pressure compressed air energy storage (CAES) system combined with pumped hydro storage based on energy and exergy analysis

Energy storage systems are becoming more important for load leveling, especially because of the widespread use of intermittent renewable energy. Compressed air energy storage (CAES) is a very promising method for energy storage because CAES relies on existing technologies, is less expensive, and easier to site and permit, as compared to pumped hydro storage. But, in the case of CAES employing hard rock caverns or man-made air vessels, although the smallest possible cavern volume is desirable in order to minimize the construction cost and optimize utilization of the given space, the operating pressure range in the cavern must be limited in order to reduce the deterioration in efficiency of the CAES system at off-design conditions. In this paper, a new constant-pressure CAES system combined with pumped hydro storage was studied to address the current problem associated with the conventional CAES systems. An energy and exergy analysis of the novel CAES system was performed in order to understand the operation characteristics of the system according to several different compression and expansion processes; we then examined the effects of the height of the storage cavern and heat transfer between two media (air, water) and the cavern on the performance of the novel CAES system.     

An integrated approach for optimal coordination of wind power and hydro pumping storage

The increasing wind power penetration in power systems represents a techno‐economic challenge for power producers and system operators. Because of the variability and uncertainty of wind power, system operators require new solutions to increase the controllability of wind farm output. On the other hand, producers that include wind farms in their portfolio need to find new ways to boost their profits in electricity markets. This can be done by optimizing the combination of wind farms and storage so as to make larger profits when selling power (trading) and reduce penalties from imbalances in the operation. The present work describes a new integrated approach for analysing wind‐storage solutions that make use of probabilistic forecasts and optimization techniques to aid decision making on operating such systems. The approach includes a set of three complementary functions suitable for use in current systems. A real‐life system is studied, comprising two wind farms and a large hydro station with pumping capacity. Economic profits and better operational features can be obtained from the proposed cooperation between the wind farms and storage. The revenues are function of the type of hydro storage used and the market characteristics, and several options are compared in this study. The results show that the use of a storage device can lead to a significant increase in revenue, up to 11% (2010 data, Iberian market). Also, the coordinated action improves the operational features of the integrated system. Copyright © 2013 John Wiley & Sons, Ltd.     

Present status of pumped hydro storage operations to mitigate renewable energy fluctuations in Japan

This paper focuses on pumped hydro energy storage (PHES) plants’ current operations after electricity system reforms and variable renewable energy (VRE) installations in Japan. PHES plants have historically been developed to create electricity demand at night in order to operate base load power plants, such as nuclear power plants, in stable conditions. Therefore, many PHES plants are located midway between nuclear power plants and large demand areas. However, all nuclear power plants had to - at least temporarily - shut down after the Great East Japan Earthquake followed by a nuclear accident at Fukushima Daiichi in 2011, and renewable energy power plants have been deployed rapidly after the introduction of a feed-in-tariff (FIT) scheme. Therefore, PHES plants are being used to mitigate fluctuations of VRE, especially in areas where renewable energy has been significantly installed. The daily highest capacity ratio of PHES plants in Kyushu area has recorded three times higher than it in the other areas where the past operating mode is still conducted. But those operations on PHES plants are simply followed as a dispatch rule of the Organization for Cross- regional Coordination of Transmission Operators (OCCTO), market-based operations have not been conducted enough yet. The market design shall be changed to harmonize VRE installation and PHES plants’ operations are necessary to make the transition from the past operating mode of PHES plants across Japan.     

Integrating energy storage with wind power in weak electricity grids

Energy storage is required to match wind generation to consumption. This time shifting can be accomplished with several hours of storage, but studies have shown that the economic value of such storage systems is unlikely to support their widespread use. This does not mean that the outlook is uniformly bleak for storage with wind power. This paper discusses storage systems ranging from a few seconds of run time to several hours, and provides a rationale for the use of systems with several minutes of run time to support a high penetration of wind power into weak electricity grids.     

A combined wind and hydro power system

A high degree of coverage of electricity demand by wind energy conversion is possible only with access to energy storage. For regions with both hydro and wind resources, the hydro power system and the wind power system may complement each other and alleviate the need for any other energy storage. Scandinavia is such a region, and this article uses a simulation model to assess the conditions under which all the electricity needs of Norway and Denmark could be satisfied by a combination of the existing Norwegian hydro power system with a hypothetical all wind-based Danish power system.     

Evaluating energy storage technologies for wind power integration

In this paper we perform a cost analysis of different types of energy storage technologies. We evaluate eleven storage technologies, including lead-acid, sodium–sulfur, nickel–cadmium, and lithium-ion batteries, superconducting magnetic energy storage, electrochemical capacitors, flywheels, flow batteries, pumped hydro and compressed air energy storage systems. We perform economic analysis for key applications associated with a wind farm integrated into the electric grid, including load shifting, frequency support, and power quality. We identify the key characteristics that affect the economic viability for these technologies, perform sensitivity analyses based on key performance criteria and find improvement areas that could make them more competitive in the near future.     

Utilization of cross-regional interconnector and pumped hydro energy storage for further introduction of solar PV in Japan

The amount of solar PV installed capacity has steadily increased to 44.5 GW at the end of FY2017, since the introduction of the Feed in Tariff (FiT) to Japan in 2012. On the other hand, since the first curtailment of solar PV was conducted on October 13th, 2018 in the Kyushu area, the curtailment has been frequently executed including wind power after that. In this study, cross-regional interconnector and pumped hydro energy storage (PHES) are focused on mitigating curtailment.In Japan, there are 9 electric power areas which connected each other by cross-regional interconnectors. According to the historical operation, cross-regional interconnectors were secured as emergency flexible measures, but after the implicit auction was started from October 2018, it is used on merit order. Regarding a PHES in Japan, they have been built with nuclear power plants for several decades. Because the output of nuclear power generation is constant, so the PHES is used to absorb the surplus at nighttime when the demand declines. All nuclear power plants in Japan have been shut down after the accident at the Fukushima Daiichi Nuclear Power Plant following the Great East Japan Earthquake that occurred on March 11th, 2011. There are several nuclear power plants that have been restarted (9 reactors, as of August 2019).In this study, the amount of curtailment for solar PV in the Kyushu area is sent to the Chugoku area using the cross-regional interconnector (Kanmon line). Then, the PHES in the Chugoku area is pumping with low price. Because the spot price in the market is low when the curtailment is executed. After that, the PHES is generating at night with high price when the solar PV is not generating. It makes a profit by the deference for the cost of pumping and the revenue of generating by the PHES. As a calculation result, for one week from May 2nd to 8th, 2019, a profit becomes 152.2 million JPY (about 1.22 million EUR). For this purpose, it is necessary to raise the operation capacity of the cross-regional interconnector up to the rated capacity with the frequency control function of solar PV instead of the capacity to keep frequency in the event of an accident. This will allow the further introduction of solar PV in Japan.     

Complementarity of hydro and wind power: Improving the risk profile of energy inflows

The complementarity of two renewable energy sources, namely hydro and wind, is investigated. We consider the diversification effect of wind power to reduce the risk of water inflow shortages, an important energy security concern for hydropower-based economic zones (e.g. Québec and Norway). Our risk measure is based on the probability of a production deficit, in a manner akin to the value-at-risk, simulation analysis of financial portfolios. We examine whether the risk level of a mixed hydro-and-wind portfolio of generating assets improves on the risk of an all-hydro portfolio, by relaxing the dependence on water inflows and attenuating the impact of droughts. Copulas are used to model the dependence between the two sources of energy. The data considered, over the period 1958–2003, are for the province of Québec, which possesses large hydro and wind resources.     

Effect of energy storage on variations in wind power

Irregularities in power output are characteristic of intermittent energy, sources such as wind energy, affecting both the power quality and planning of the energy system. In this work the effects of energy storage to reduce wind power fluctuations are investigated. Integration of the energy storage with wind power is modelled using a filter approach in which a time constant corresponds to the energy storage capacity. The analyses show that already a relatively small energy storage capacity of 3 kWh (storage) per MW wind would reduce the short‐term power fluctuations of an individual wind turbine by 10%. Smoothing out the power fluctuation of the wind turbine on a yearly level would necessitate large storage, e.g. a 10% reduction requires 2–3 MWh per MW wind. Copyright © 2005 John Wiley & Sons, Ltd.     

Review on combined wind power generation and energy storage systems

储能系统由于能够实现电能的时空平移,具有响应速度快,规模化等优点,是改善风电波动性,提高其并网能力的有效手段,构建风储联合发电系统成为目前研究重点.简单介绍了风电并网对电力系统的影响及不同类型电池储能技术的发展现状,给出了部分国内外风储联合发电系统的示范工程,并分析了平滑风电功率波动,跟踪计划出力曲线和削峰填谷3种主要运行方式,重点阐述了目前风储联合发电系统控制策略和储能容量配置研究现状,对进一步开展风储联合发电系统的研究进行了展望,指出经济性仍然是制约储能技术应用的关键问题之一,提高包含储能单元的风储联合发电系统的经济性是今后的研究重点.     

储能技术在风力发电中应用研究的发展

介绍了各种储能方式在风电系统中应用的原理、优缺点和发展前景,提出了发展趋势,并指出了最有前景的储能方式.     

A review of energy storage technologies for wind power applications

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.     

Review of flywheel energy storage systems for wind power applications

风力发电可以解决能源短缺和环境污染等问题,但由于风速随机性和间歇性的特点导致风电输出电压、功率和频率存在较大波动,因此风电的大规模并网会对现有电网的稳定运行造成不利影响。飞轮储能是一种高效无污染的储能技术,而且通过合理的控制策略和控制设备可实现电网调频及短时间调峰以解决大规模风电并网带来的问题。本文主要介绍了飞轮储能在风力发电领域的应用背景、飞轮储能的结构原理和目前国内外在飞轮储能控制策略方向的研究进展。     

Concept study of wind power utilizing direct thermal energy conversion and thermal energy storage

Present wind power is intermittent and cannot be used as the baseload energy source. Concept study of wind power utilizing direct thermal energy conversion and thermal energy storage named Wind powered Thermal Energy System (WTES) is conducted. The thermal energy is generated from the rotating energy directly at the top of the tower by the heat generator, which is a kind of simple and light electric brake. The rest of the system is the same as the tower type concentrated solar power (CSP). The cost estimation suggests that the energy cost of WTES is less than that of the conventional wind power, which must be supported by the backup thermal plants and grid enhancement. The light heat generator reduces some issues of wind power such as noise and vibration.