Energy Storage

Gerard M Crawley

• Éditeur: WSPC
• Année: 2017
• ISBN:
  9789813208971
• Sujet: Technologie et ingénierie
• Sous-sujet: Ressources d'alimentation

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The subject of energy storage is extremely important for the increased utilization of renewable energies such as solar and wind energy in times when their sources (e.g. the sun and wind) are unavailable. The ability to store energy can also level out the demand curve for electricity and thus lead to a decrease in the peak requirements of energy production. A storage system for ground transportation is also important as a potential replacement for fossil fuel powered transportation.

Energy Storage offers a comprehensive look at the possible approaches to energy storage, which are relevant to various situations; from smoothing demand in electrical energy production, applications of energy storage, to transportation. The book covers a variety of approaches to the storage of energy. Beginning with a discussion of the critical importance of energy storage, the book discusses various possible storage options including hydro storage, compressed air energy storage, and electrical and chemical storage in batteries, capacitors and fuel cells. There is also a chapter on the mechanical storage of energy with flywheels using advanced materials. The various applications to power production and transportation are also included. The expertise and active involvement of the authors of the various chapters ensures that the information is reliable, current, and forward looking.

--> Contents:

• The Importance of Energy Storage (Anna Stoppato and Alberto Benato)
• Pumped-Storage Hydropower Plants: The New Generation (Giovanna Cavazzini, Juan I Pérez-Díaz, Francisco Blázquez, Carlos Platero, Jesús Fraile-Ardanuy, José A Sánchez and Manuel Chazarra)
• Compressed Air Energy Storage (Jihong Wang, Xing Luo, Christopher Krupke and Mark Dooner)
• Batteries for Energy Storage (Paul A Connor)
• Capacitive Energy Storage (Wentian Gu, Lu Wei and Gleb Yushin)
• Fuel Cells and the Hydrogen Economy (John T S Irvine, Gael P G Corre and Xiaoxiang Xu)
• Flywheels (Donald Bender)

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--> Readership: Graduate students, researchers and professionals in fields related to, and or dealing with issues pertaining to energy studies/research, electrical and electronic engineering. -->
Pumped Hydro Energy Storage;Compressed Air Energy Storage;Batteries;Capacitors;Fuel Cells: The Hydrogen Economy;Flywheels Key Features:

• This is a comprehensive look at the possible approaches to energy storage which are relevant to various situations including needed storage for renewable resources like solar and wind, plus smoothing demand in electrical energy production as well as applications of energy storage to transportation
• The expertise of the authors of the various chapters ensures that the information is reliable
• The information presented is current and forward looking because the authors are actively involved in the technologies discussed in the various chapters

Chapter 1

The Importance of Energy Storage

Anna Stoppato* and Alberto Benato^†

Department of Industrial Engineering, Padova University
via Venezia, 35138 Padova, Italy
*[email protected]
^†[email protected]

This chapter describes the role that energy storage can play in the present and in the short–medium term future energy scenario. Both stationary and automotive applications will be considered and the main features required by each of them for an energy storage system will be explained. A very brief description of the proven and most promising storage technologies will be given with the aim of providing an overview of the peculiarities of each one and consequently its better suited applications. Finally, the state-of-the-art, the opportunities and the barriers to the spread of energy storage systems will be summarized.

1Introduction

The energy scenario has significantly changed in the last decade for a variety of factors. The first one is the increase in the amount of electrical capacity supplied by variable and non-predictable renewable sources. In recent years, the growing awareness at both the public and institutional levels of the “energy issue” has led to a series of initiatives aimed at promoting the use of renewable energy sources (RESs).¹ Definitely, their use often results in a lower environmental impact in terms of a reduction of both resources’ consumption and emissions, with special regard to carbon dioxide, which is responsible for the greenhouse effect. Worldwide, the policy of incentives for renewable energy plants and for the reduction of greenhouse gas emissions,^2,3 and the development of less expensive and more efficient technologies has brought a significant increase in the number of such systems, especially wind power and photovoltaic plants, as shown in Fig. 1.

Fig. 1.Trend of capacity supply and energy production by wind and PV power plants.⁴

The comparison between the installed capacity and energy production allows us to evaluate the load factor of such plants, expressing the ratio between the energy actually produced and that theoretically producible if the plant would run throughout the year at its design power: the value is low and around 22% for wind power and 12% for solar. This is due to the extreme variability of the sun and of the wind over the year and even in a single day, so that the plant can operate at design load only for a limited number of hours per year. In addition, the low predictability of these variations makes the production scheduling more difficult, especially for wind power even in the very short term.

A second aspect is due to the progressive deregulation of the energy market carried out in many developed countries,^5,6 which aims to separate the activities of generation, transmission and distribution of electricity and where for every hour of the year the price of energy is determined by the intersection between supply and demand curves. The main goal of deregulation is the promotion of fair competition in the production and sale of electricity in order to reduce energy costs and increase the efficiency of the system. A first consequence has been the significant and rapid growth of the installed generation capacity⁴: in OECD countries in 2000, the power plants had a total installed capacity of 2,080 GW, of which 1,311 GW was from thermal power plants; in 2012, this installed capacity had become 2,777 GW (of which 1677.0 GW was from thermal plants) with a growth in 12 years of 33% (28% for the thermal segment only). But in some countries, this expansion has been even greater (in Italy, +65% and +37%, in the USA, +31% and +30%, respectively).

In many countries, the installed capacity increment was matched by a reduction in energy consumption mainly due to the global economic crisis of 2008 followed by a very slow recovery: for example, in Italy, the electricity demand in 2012 was equal to that in 2004, while in the USA, it was similar to that of 2006.

In almost all the developed countries, in a more or less marked way, the combined effects of the aforementioned factors has created a situation where the installed capacity is overabundant with respect to the users’ peak demand, and where quite a high fraction of power is made available by variable and difficult to predict renewable sources. This condition definitely implies a significant saving of fossil fuels and the reduction of emissions, but introduces some critical elements into the market. In addition, the advent of generators powered by renewable sources has drastically changed the structure of the electricity network with the presence of a large number of small power production facilities spread over the country in the vicinity of the users and of the available sources, instead of a classic structure with “a few” large facilities concentrated in the industrial zones of the country.

It is important to remember that the power grid is a very complex system which transmits and distributes electricity generated from the production plants to users through a set of power lines, transformer stations, isolation and protection systems, and is subject to very stringent technical constraints, in particular:

•An instantaneous and continuous balance between the amount of energy released and that required by the network is necessary, taking into account the losses due to transformers, transport and distribution.

•The frequency and voltage must be kept within a very narrow range of values (60 Hz in USA and some other countries in America, 50 Hz in Europe and in many countries of the world), which is essential to protect the safety of the generation and end-user facilities.

•It must always be ensured that the energy flow in each power line does not exceed the maximum permissible load on the power line itself.

The change of any one of the abovementioned parameters, even if minor and/or of very short duration, can rapidly induce a state of crisis into the entire local electrical system and subsequently, because of a “domino” effect, to a possible blackout of the entire network. For example, the sudden drop in power available from wind turbines caused by an unexpected reduction of the wind speed can cause stability problems to the network when the share of energy provided by these systems is significant.

But even in the absence of extreme events, during the normal hours when the wind is blowing or the sun is shining, a significant fraction of energy use is met by renewable energy and so thermal power plants are forced to stand idle or to work at partial load with low efficiency. Therefore, when thermal plants are called upon to operate, sometimes suddenly, they impose a high price on the market, which partly offsets the higher costs associated with frequent stops and part load operation. As an example, the quantity and the price of electricity sold on the Italian day-ahead market in two days of May 2013 are reported in Fig. 2,⁷ showing two very different trends and average values. This great variability on the supply side has enhanced the role and the value of the markets for ancillary services, and has led to a major diffusion and increased importance of the capacity markets which have to ensure that supply will be available when it is needed.

This provides an additional incentive for owners of generating capacity (i.e. power plants or demand response providers) to make their capacity available to electricity markets where price signals alone would not.

Besides the great complexity of the electricity market itself, the general increase in fossil fuel costs plus the high variability and unpredictability of their trend is a further source of concern in the scheduling of thermal plant operation.

As a final issue, the transport sector is also undergoing many changes. The most important driver is the requirement to reduce pollutants, mainly particulates, in urban areas. This issue demands new transportation solutions: one of the most promising and studied is that of pure electric and hybrid vehicles, combining a traditional fossil fueled engine with an electric propulsion system (see Fig. 3, Ref. 8). These vehicles are powered by the energy stored in an on-board battery, which will be recharged at the so-called “charging-points” usually connected to the grid. With a proper operation strategy, these charging stations can be managed as users with flexible demand and are able to dampen the peaks and the gaps of energy supply.

Fig. 2.Trend of electricity sold in the market and of its price on two different days of May 2013: Sunday 12 and Thursday 16.⁷

The combination of all these elements has led therefore to the need to rethink the arrangements for managing both the electricity network as a whole, as well as individual plants. The main target is to supply energy with high efficiency, low cost, high reliability, and low environmental impact.

As a last point, it is important to note that in developing countries or for communities looking for energy self-sufficiency, the exploitation of renewable sources is an opportunity to increase the n...

Table des matières

• Cover Page
• Title
• Copyright
• Foreword to the World Scientific Series on Current Energy Issues
• About the Editor
• Contents
• Chapter 1. The Importance of Energy Storage
• Chapter 2. Pumped-Storage Hydropower Plants: The New Generation
• Chapter 3. Compressed Air Energy Storage
• Chapter 4. Batteries for Energy Storage
• Chapter 5. Capacitive Energy Storage
• Chapter 6. Fuel Cells and the Hydrogen Economy
• Chapter 7. Flywheels
• About the Contributors
• Index