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Hydropower 2017

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A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (14 November 2017) | Viewed by 65289

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Emeritus Prof. Ånund Killingtveit

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Guest Editor

Department of Civil and Environmental Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway
Interests: hydrology applied to hydropower planning, design and operation; dam safety; flood control; environmental and social impacts of hydropower; impact of climate change on natural and man-made water systems; interaction between hydropower and other renewable energy technologies, in particular wind and solar; hydropower in cold climate
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Prof. Dr. Juan Ignacio Pérez-Díaz

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Department of Hydraulic, Energy and Environmental Engineering, Technical University of Madrid (UPM), c/ Profesor Aranguren s/n 28040 Madrid, Spain
Interests: hydropower scheduling; simulation of hydraulic transients in hydropower plants; control of hydropower plants; provision of load-frequency control by hydropower plants; pumped-storage
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Hydropower has been the main source of renewable electrical energy for more than a hundred years, and will continue to be so far into the future. Though hydropower is a mature technology, there is still need for and room for technological improvements, in particular for adaptation to many new challenges: New market conditions, new environmental policies, the water-food-energy-ecosystem nexus, adapting to a changing climate with its impacts on water resources and for storage of electrical energy. Hydropower offers significant potential for carbon emission reductions. With an annual generation of 4000 TWh, 16% of world electricity generation, hydropower remains the largest source of renewable energy in the electricity sector. Still, there is a potential to double the global hydropower generation, up to 8000 TWh or even more.

Hydropower planning and operation is also a very important element in water resources management, and is in the center of the “Water-Energy-Food-Ecosystem Nexus”. During hydropower development, one nearly always needs to consider many other users and uses of water, making both planning and operation much more challenging than for other renewables. Situated at the crossroads of two major issues for development, water and energy, hydro reservoirs are vital components that can deliver services also beyond electricity supply, such as flood control, transport, recreation, and water supply for irrigation, municipal consumption, and industry. In addition to providing energy and capacity, hydropower offers several other advantages to the grid, such as supporting frequency control, voltage control, “black start” capability, energy storage, and the capability to balance demand and generation at timescales from seconds to weeks. The rapid development of other renewables, like wind and solar, is creating an increasing demand for energy storage and load balancing. Here, hydropower is often a perfect companion. Renewables are also serving as an incentive for novel technological developments and operational practices.

In this Special Issue, which is a continuation of the successful 2016 Special Issue on “Hydropower”, we would like to pay special attention to the grid integration of variable renewable energy, and the role of hydropower in this process. In this context, we invite authors to submit papers dealing with the joint operation of hydro and other renewable generation, multi-market scheduling of hydropower systems, extension of the stable operating range of hydropower turbines, decrease of hydropower turbines start-up time, ageing, fatigue and maintenance of the various power plant elements due to a more flexible operation, dedicated design of hydropower turbines and generators for variable speed and hydraulic short-circuit operation, new control strategies and systems for a more flexible operation, introduction of peaking and pumped-storage hydropower plants in older hydropower systems and upgrading of existing hydropower units to variable speed.

The scope of this Special Issue is, of course, not limited to the above-mentioned topics. We will be pleased to receive papers from the full value-chain of hydropower, including resource-mapping, planning, design, construction, maintenance and operation, interaction and integration with other uses of water, and the effects of the uncertainty brought by climate change.

Prof. Dr. Ånund Killingtveit
Prof. Dr. Juan Ignacio Pérez-Díaz
Guest Editors

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Keywords

hydropower
pumped storage
power system ancillary services
renewable energy integration
optimal operation
environmental impacts
climate change

Published Papers (13 papers)

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Research

21 pages, 4337 KiB

Open AccessArticle

Hydropower Impacts on Electrical System Production Costs in the Southwest United States

by Dominique M. Bain and Thomas L. Acker

Energies 2018, 11(2), 368; https://doi.org/10.3390/en11020368 - 04 Feb 2018

Cited by 16 | Viewed by 6935

Abstract

The Colorado River is an important natural resource for the Southwestern United States. Predicted climate change impacts include increased temperature, decreased rainfall and increased probability of drought in this region. Given the large amount of hydropower on the Colorado River and its importance to the bulk electricity system, this purpose of this study was to quantify the value hydropower in operating the electrical system, and examined changes in hydropower value and electricity costs under different possible future drought conditions and regional generation scenarios. The goal was to better understand how these scenarios affect operating costs of the bulk electrical system, as well as the value of the hydropower produced, and proposed a method for doing so. The calculated value of the hydroelectric power was nearly double the mean locational marginal price in the study area, about $73 to $75 for most scenarios, demonstrating a high value of the hydropower. In general, it was found that reduced water availability increased operating costs, and increased the value of the hydropower. A calculated value factor showed that when less hydroelectric power is available, the hydropower is more valuable. Furthermore, the value factor showed that the value of hydro increases with the addition of solar or the retirement of thermal generating resources. Full article

(This article belongs to the Special Issue Hydropower 2017)

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19 pages, 7855 KiB

Open AccessArticle

Assessment of Future Whole-System Value of Large-Scale Pumped Storage Plants in Europe

by Fei Teng, Danny Pudjianto, Marko Aunedi and Goran Strbac

Energies 2018, 11(1), 246; https://doi.org/10.3390/en11010246 - 19 Jan 2018

Cited by 17 | Viewed by 4346

Abstract

This paper analyses the impacts and benefits of the pumped storage plant (PSP) and its upgrade to variable speed on generation and transmission capacity requirements, capital costs, system operating costs and carbon emissions in the future European electricity system. The combination of a deterministic system planning tool, Whole-electricity System Investment Model (WeSIM), and a stochastic system operation optimisation tool, Advanced Stochastic Unit Commitment (ASUC), is used to analyse the whole-system value of PSP technology and to quantify the impact of European balancing market integration and other competing flexible technologies on the value of the PSP. Case studies on the Pan-European system demonstrate that PSPs can reduce the total system cost by up to €13 billion per annum by 2050 in a scenario with a high share of renewables. Upgrading the PSP to variable-speed drive enhances its long-term benefits by 10–20%. On the other hand, balancing market integration across Europe may potentially reduce the overall value of the variable-speed PSP, although the effect can vary across different European regions. The results also suggest that large-scale deployment of demand-side response (DSR) leads to a significant reduction in the value of PSPs, while the value of PSPs increases by circa 18% when the total European interconnection capacity is halved. The benefit of PSPs in reducing emissions is relatively negligible by 2030 but constitutes around 6–10% of total annual carbon emissions from the European power sector by 2050. Full article

(This article belongs to the Special Issue Hydropower 2017)

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1123 KiB

Open AccessArticle

Value-Creation Potential from Multi-Market Trading for a Hydropower Producer

by Marte Fodstad, Mats Mathisen Aarlott and Kjetil Trovik Midthun

Energies 2018, 11(1), 16; https://doi.org/10.3390/en11010016 - 22 Dec 2017

Cited by 4 | Viewed by 3213

Abstract

We study a hydropower producer’s potential for value-creation from multi-market trading given the price variations in the markets and the flexibility provided through access to hydro reservoirs. We use a perfect foresight optimization model for a price-taking hydropower producer co-optimizing his trades in the day-ahead, intra-day and balancing markets. The model is used on real market data from Norway, Sweden and Germany. The study shows a theoretical potential for added value when selling energy in multiple markets relative to optimal day-ahead sale. Most of this value is achievable also when the perfect foresight is limited to the period from day-ahead bidding until operation. Flexible production plants achieve the largest relative added values for multi-market sales, and has the largest benefit from a long horizon with perfect foresight. Full article

(This article belongs to the Special Issue Hydropower 2017)

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4466 KiB

Open AccessArticle

Extension of Operating Range in Pump-Turbines. Influence of Head and Load

by Carme Valero, Mònica Egusquiza, Eduard Egusquiza, Alexandre Presas, David Valentin and Matias Bossio

Energies 2017, 10(12), 2178; https://doi.org/10.3390/en10122178 - 19 Dec 2017

Cited by 29 | Viewed by 4902

Abstract

Due to the increasing share of new renewable energies like wind and solar in the generation of electricity the need for power regulation and energy storage is becoming of paramount importance. One of the systems to store huge amounts of energy is pumped storage using reversible hydropower units. The machines used in these power plants are pump-turbines, which can operate as a pump and as a turbine. The surplus of electrical energy during low consumption hours can be converted into potential hydraulic energy by pumping water to a higher level. The stored energy can be converted into electricity again by operating the runner as a turbine. Due to new regulation requirements machines have to extend the operating range in order to match energy generation with consumption for the grid stability. In this paper the consequences of extending the operating range in existing pump-turbines have been studied. For that purpose, the data obtained after two years of condition monitoring were analyzed. Vibrations and pressure fluctuations of two pump-turbines of 85 MW each have been studied during pump and turbine operation. For turbine operation the effects of extending the operating range from the standard range of 45–85 MW to and increased range of 20–85 MW were analyzed. The change in vibration levels and signatures at very low load are presented with the identification of the phenomena that occur under these conditions. The influence of head in the vibration behavior is also presented. The appearance of fluid instabilities generated at part load that may produce power swing is also presented. Finally, the effect of head on the vibration levels for pump operation is shown and analyzed. Full article

(This article belongs to the Special Issue Hydropower 2017)

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926 KiB

Open AccessArticle

Hydro Power Reservoir Aggregation via Genetic Algorithms

by Markus Löschenbrand and Magnus Korpås

Energies 2017, 10(12), 2165; https://doi.org/10.3390/en10122165 - 18 Dec 2017

Cited by 13 | Viewed by 3520

Abstract

Electrical power systems with a high share of hydro power in their generation portfolio tend to display distinct behavior. Low generation cost and the possibility of peak shaving create a high amount of flexibility. However, stochastic influences such as precipitation and external market effects create uncertainty and thus establish a wide range of potential outcomes. Therefore, optimal generation scheduling is a key factor to successful operation of hydro power dominated systems. This paper aims to bridge the gap between scheduling on large-scale (e.g., national) and small scale (e.g., a single river basin) levels, by applying a multi-objective master/sub-problem framework supported by genetic algorithms. A real-life case study from southern Norway is used to assess the validity of the method and give a proof of concept. The introduced method can be applied to efficiently integrate complex stochastic sub-models into Virtual Power Plants and thus reduce the computational complexity of large-scale models whilst minimizing the loss of information. Full article

(This article belongs to the Special Issue Hydropower 2017)

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13619 KiB

Open AccessArticle

Power Swing Generated in Francis Turbines by Part Load and Overload Instabilities

by David Valentín, Alexandre Presas, Eduard Egusquiza, Carme Valero, Mònica Egusquiza and Matias Bossio

Energies 2017, 10(12), 2124; https://doi.org/10.3390/en10122124 - 13 Dec 2017

Cited by 61 | Viewed by 5147

Abstract

Hydropower plays a key role in the actual energy market due to its fast response and regulation capacity. In that way, hydraulic turbines are increasingly demanded to work at off-design conditions, where complex flow patterns and cavitation appear, especially in Francis turbines. The draft tube cavitation surge is a hydraulic phenomenon that appears in Francis turbines below and above its Best Efficiency Point (BEP). It is a low frequency phenomenon consisting of a vortex rope in the runner outlet and draft tube, which can become unstable when its frequency coincides with a natural frequency of the hydraulic circuit. At this situation, the output power can significantly swing, endangering the electrical grid stability. This study is focused on the detection of these instabilities in Francis turbines and their relationship with the output power swings. To do so, extensive experimental tests for different operating conditions have been carried out in a large prototype Francis turbine (444 MW of rated power) within the frame of the European Project Hyperbole (FP7-ENERGY-2013-1). Several sensors have been installed in the hydraulic circuit (pressure sensors in the draft tube, spiral casing, and penstock), in the rotating and static structures (vibration sensors, proximity probes, and strain gauges in the runner and in the shaft), as well as in the electrical side (output power, intensity, and voltage). Moreover, a numerical Finite Element Method (FEM) has been also used to relate the hydraulic excitation with the output power swing. Full article

(This article belongs to the Special Issue Hydropower 2017)

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24769 KiB

Open AccessArticle

Norway as a Battery for the Future European Power System—Impacts on the Hydropower System

by Ingeborg Graabak, Stefan Jaehnert, Magnus Korpås and Birger Mo

Energies 2017, 10(12), 2054; https://doi.org/10.3390/en10122054 - 04 Dec 2017

Cited by 34 | Viewed by 7911

Abstract

Future power production in Europe is expected to include large shares of variable wind and solar power production. Norway, with approximately half of the hydropower reservoir capacity in Europe, can contribute to balance the variability. The aim of this paper is to assess how such a role may impact the Norwegian hydropower system in terms of production pattern of the plants, changes in reservoir level and water values. The study uses a stochastic optimization and simulation model and analyses an eHighway2050 scenario combined with increases in the hydropower production capacities in Norway. The capacity increases from ca. 31 GW in the present system to 42 and 50 GW respectively. The study uses 75 years with stochastic wind, solar radiation, temperature and inflow data. The results show that the hydropower system is able to partly balance the variable production and significantly reduce the power prices for the analyzed case. The paper shows that some of the power plants utilize their increased capacity, while other plants do not due to hydrological constraints and model limitations. The paper discusses how the modelling can be further improved in order to quantify more of the potential impacts on the future power system. Full article

(This article belongs to the Special Issue Hydropower 2017)

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1020 KiB

Open AccessArticle

Hydropower Bidding Using Linearized Start-Ups

by Ellen Krohn Aasgård

Energies 2017, 10(12), 1975; https://doi.org/10.3390/en10121975 - 28 Nov 2017

Cited by 4 | Viewed by 3420

Abstract

Hydropower producers must submit bids to electricity market auctions where they state their willingness to produce power. These bids may be determined using a mixed-integer linear stochastic program. However, for large interconnected river systems, this program may be too complex to be solved within the time limits set by current market rules. This paper investigates whether a linear approximation to start-ups can be used to reduce the computational burden without significantly degrading the solution quality. In order to investigate the trade-off of time versus solution quality, linear approximation is compared to a formulation that uses binary variables in a case study that simulates the operation of a reservoir system over time. Full article

(This article belongs to the Special Issue Hydropower 2017)

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2334 KiB

Open AccessArticle

Aggregation Methods for Modelling Hydropower and Its Implications for a Highly Decarbonised Energy System in Europe

by Philipp Härtel and Magnus Korpås

Energies 2017, 10(11), 1841; https://doi.org/10.3390/en10111841 - 11 Nov 2017

Cited by 34 | Viewed by 4994

Abstract

Given the pursuit of long-term decarbonisation targets, future power systems face the task of integrating the renewable power and providing flexible backup production capacity. Due to its general ability to be dispatched, hydropower offers unique features and a backup production option not to be neglected, especially when taking the flexibility potential of multireservoir systems into account. Adequate hydropower representations are a necessity when analysing future power markets and aggregation methods are crucial for overcoming computational challenges. However, a major issue is that the aggregation must not be a too flexible representation. In a first step, a novel equivalent hydro system model implementation including a possibility to integrate pumping capacity and appropriate handling of multiple water paths (hydraulic coupling) by making use of an ex-ante optimisation is proposed. In a second step, a clustered equivalent hydro system model implementation employing k-means clustering is presented. A comparison of both aggregation approaches against the detailed reference system shows that both aggregated model variants yield significant reductions in computation time while keeping an adequate level of accuracy for a highly decarbonised power system scenario in Europe. The aggregation methods can easily be applied in different model types and may also be helpful in the stochastic case. Full article

(This article belongs to the Special Issue Hydropower 2017)

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4760 KiB

Open AccessArticle

A Computed River Flow-Based Turbine Controller on a Programmable Logic Controller for Run-Off River Hydroelectric Systems

by Razali Jidin and Abdul Bahari Othman

Energies 2017, 10(11), 1717; https://doi.org/10.3390/en10111717 - 27 Oct 2017

Cited by 2 | Viewed by 6583

Abstract

The main feature of a run-off river hydroelectric system is a small size intake pond that overspills when river flow is more than turbines’ intake. As river flow fluctuates, a large proportion of the potential energy is wasted due to the spillages which can occur when turbines are operated manually. Manual operation is often adopted due to unreliability of water level-based controllers at many remote and unmanned run-off river hydropower plants. In order to overcome these issues, this paper proposes a novel method by developing a controller that derives turbine output set points from computed mass flow rate of rivers that feed the hydroelectric system. The computed flow is derived by summation of pond volume difference with numerical integration of both turbine discharge flows and spillages. This approach of estimating river flow allows the use of existing sensors rather than requiring the installation of new ones. All computations, including the numerical integration, have been realized as ladder logics on a programmable logic controller. The implemented controller manages the dynamic changes in the flow rate of the river better than the old point-level based controller, with the aid of a newly installed water level sensor. The computed mass flow rate of the river also allows the controller to straightforwardly determine the number of turbines to be in service with considerations of turbine efficiencies and auxiliary power conservation. Full article

(This article belongs to the Special Issue Hydropower 2017)

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852 KiB

Open AccessFeature PaperArticle

Application of Dynamic Non-Linear Programming Technique to Non-Convex Short-Term Hydrothermal Scheduling Problem

by Omid Hoseynpour, Behnam Mohammadi-ivatloo, Morteza Nazari-Heris and Somayeh Asadi

Energies 2017, 10(9), 1440; https://doi.org/10.3390/en10091440 - 19 Sep 2017

Cited by 30 | Viewed by 4798

Abstract

Short-term hydro-thermal scheduling aims to obtain optimal generation scheduling of hydro and thermal units for a one-day or a one-week scheduling time horizon. The main goal of the problem is to minimize total operational cost considering a series of equality and inequality constraints. The problem is considered as a non-linear and complex problem involving the valve-point loading effect of conventional thermal units, the water transport delay between connected reservoirs, and transmission loss with a set of equality and inequality constraints such as power balance, water dynamic balance, water discharge, initial and end reservoir storage volume, reservoir volume limits and the operation limits of hydro and thermal plants. A solution methodology to the short-term hydro-thermal scheduling problem with continuous and non-smooth/non-convex cost function is introduced in this research applying dynamic non-linear programming. In this study, the proposed approach is applied to two test systems with different characteristics. The simulation results obtained in this paper are compared with those reported in recent research studies, which show the effectiveness of the presented technique in terms of total operational cost. In addition, the obtained results ensure the capability of the proposed optimization procedure for solving short-term hydro-thermal scheduling problem with transmission losses and valve-point effects. Full article

(This article belongs to the Special Issue Hydropower 2017)

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3112 KiB

Open AccessArticle

Deriving Optimal End of Day Storage for Pumped-Storage Power Plants in the Joint Energy and Reserve Day-Ahead Scheduling

by Manuel Chazarra, Juan I. Pérez-Díaz and Javier García-González

Energies 2017, 10(6), 813; https://doi.org/10.3390/en10060813 - 15 Jun 2017

Cited by 8 | Viewed by 4023

Abstract

This paper presents a new methodology to maximise the income and derive the optimal end of day storage of closed-loop and daily-cycle pumped-storage hydropower plants. The plants participate in the day-ahead energy market as a price-taker and in the secondary regulation reserve market as a price-maker, in the context of the Iberian electricity system. The real-time use of the committed reserves is considered in the model formulation. The operation of the plants with the proposed methodology is compared to the ones that use an end of day storage of an empty reservoir or half of the storage capacity. Results show that the proposed methodology increases the maximum theoretical income in all the plants analysed both if they only participate in the day-ahead energy market and if they also participate in the secondary regulation service. It is also shown that the increase in the maximum theoretical income strongly depends on the size of the plant. In addition, it is proven that the end of day storages change notably in the new reserve-driven strategies of pumped-storage hydropower plants and that the proposed methodology is even more recommended if the secondary regulation service is considered. Full article

(This article belongs to the Special Issue Hydropower 2017)

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4736 KiB

Open AccessArticle

Frequency-Adaptive Modified Comb-Filter-Based Phase-Locked Loop for a Doubly-Fed Adjustable-Speed Pumped-Storage Hydropower Plant under Distorted Grid Conditions

by Wei Luo, Jianguo Jiang and He Liu

Energies 2017, 10(6), 737; https://doi.org/10.3390/en10060737 - 23 May 2017

Cited by 5 | Viewed by 4523

Abstract

The control system of a doubly-fed adjustable-speed pumped-storage hydropower plant needs phase-locked loops (PLLs) to obtain the phase angle of grid voltage. The main drawback of a comb-filter-based phase-locked loop (CF-PLL) is the slow dynamic response. This paper presents a modified comb-filter-based phase-locked loop (MCF-PLL) by improving the pole-zero pattern of the comb filter, and gives the parameters’ setting method of the controller, based on the discrete model of MCF-PLL. In order to improve the disturbance resistibility of MCF-PLL when the power grid’s frequency changes, this paper proposes a frequency-adaptive modified, comb-filter-based, phase-locked loop (FAMCF-PLL) and its digital implementation scheme. Experimental results show that FAMCF-PLL has good steady-state and dynamic performance under distorted grid conditions. Furthermore, FAMCF-PLL can determine the phase angle of the grid voltage, which is locked when it is applied to a doubly-fed adjustable-speed pumped-storage hydropower experimental platform. Full article

(This article belongs to the Special Issue Hydropower 2017)

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