Energy Storage
ECINE 5
Energy Storage
An energy storage system (ESS) is a device that stores electricity
produced at one time for use at a later time to reduce imbalances
between energy demand and energy production.
ESS are valuable components in most energy systems and could be an
important tool in achieving a low-carbon future.
Energy storage deployment is competitive or near competitive in
today’s energy system.
Difficulties of storing electrical
energy
•The electrical energy vector has been highly developed over the past
150 years
•Its transport over long distances at very high voltage is possible due
to transformers, which make it possible to adjust the amplitude of
voltage and current waves at will.
•The weak point of the electricity vector is that electrical currents
cannot be stored directly.
•Electrical energy must be transformed into another form of energy to
obtain substantial storage capacities.
Difficulties of storing electrical
energy
•The difficulty of storing electrical energy explains why the
management of electrical grids has been designed according to the
principle of direct consumption of the electrical energy produced,
even when the distance between production and consumption is
several hundred kilometers.
•The energetic conversion required for storage causes very different
losses depending on the storage technologies used.
•These losses can range from 10% to 50%, or even more.
Why store electrical energy?
•The management of electrical grids is based principally on the direct
consumption of the electrical energy produced.
•As consumption is variable, this approach requires the constant
adaptation of production to this consumption.
Fig.1. Typical profiles of domestic consumers, Fig.2. Typical profiles of commercial consumers
Why store electrical energy?
•Since the development of renewable energy sources, electrical grids
have been forced to face the accommodation of highly intermittent
production, as is the case for wind, photovoltaic and marine energies,
as well as small hydraulic run-of-the-river energies
•a wind turbine’s production of 300 kW (Fig. 3) .
•Apart from high variability, fluctuations of 100 kW in 3 s have been
recorded.
Fig. 3: Example of power generated by a fixed speed wind turbine of 300 kW
Why store electrical energy?
•The production of a photovoltaic facility in the span of a day; the
presence of clouds induces a high variability of this production (Fig.4).
•Hydraulic resources also show significant fluctuations.
•Ocean waves are an abundant resource, but with large and rapid
variations (Fig. 5).
Fig. 5: Variation in wave height Fig. 4: Profiles of a sunny day with clouds
Why store electrical energy?
•These examples show that the balance between production and
consumption does not occur naturally, and has been complicated by the
increasing development of high-variability renewable energies.
•Storage of the electrical energy produced by these renewable sources
makes it possible to smooth their production, and thus to facilitate their
adaptation to consumption.
•Sources such as nuclear power plants ideally produce at constant power.
In this case, storage of overproduction during the night makes it possible
to compensate for underproduction during the peak hours of the day.
Value enhancement of storage in
electrical grids
•Energy storage systems are costly, and the additional cost they incur
in a system of production or consumption can be prohibitive to their
installation.
•The cost of storage varies greatly depending on the technologies and
the maturity level of these technologies, which are the subject of a
great deal of research and development work.
•It is necessary to make sure that the economic enhancement of
storage over its lifespan will at least compensate for the investment
and maintenance costs.
Value enhancement of storage in
electrical grids
•The value enhancement of storage in electrical grids will be
dependent on the various services it can provide, which will depend
on its positioning in the grid.
•To make storage profitable, one approach consists of mutualizing the
services that a storage system can contribute among various actors
(managers, producers and consumers).
Value enhancement of storage in
electrical grids
•These services consist of:
– local precise and dynamic voltage control;
– support of grid in degraded operation;
– reactive compensation for grid managers (and customers);
– reduction of transport losses;
– power quality;
– energy postponement and support to the production units;
– primary frequency control and frequency stability of insular grids;
– solving of congestion;
– support for participation in ancillary services; – erasure recovery;
– guarantee of a production profile;
– peak smoothing;
– consumption postponement;
– supply quality/continuity.
Value enhancement of storage in
electrical grids
•For more than a century, grid management has been based on a centralized
approach with limited means of communication, particularly in distribution
grids.
•The implementation and use of new communication technologies along with
advanced management resources will increase the intelligence level of grids
and contribute to a safe increase in the penetration rate of random
productions, while also increasing the energy efficiency of these intelligent
grids.
Value enhancement of storage in
electrical grids
•In this evolution toward smart grids, the storage of electrical energy will
play an important role in favoring the development of renewable energies
and contributing to the stability of electrical grids, as well as favoring self-
consumption in the residential sector, industry and transportation systems.
•The mechanisms of the electricity market also influence the profitability of
storage systems.
•These mechanisms differ from one country to another and, in a competitive
environment, evolve with time to favor the development of renewable
energies generated on a grid or self-consumed, some loads such as electric
vehicles, and energy storage.
Energy Storage
•Electrical energy can be converted to many different forms
for storage:
• as gravitational potential energy with water reservoirs
• as compressed air
• as electrochemical energy in batteries and flow batteries
• as chemical energy in fuel cells
• as kinetic energy in flywheels
• as magnetic fields in inductors
• as electric fields in capacitors.
Energy Storage
Energy Storage Status Worldwide
•A number of ES projects with
varying scales have been
developed globally.
•The highest number of
operational ES projects
belongs to battery ES (more
than 350).
•PHES is ranked in the second
place with approximately
300 projects. This is followed
by TES systems.
Energy Storage Status Worldwide
Global total operational energy storage project capacity (MW), 2020
Energy Storage Status Worldwide
Global operational electricity storage power capacity by technology,
Course Objectives
•Review several available energy storage technologies that can be
used in electric power systems.
•The operating principles, the main components, and the most
relevant characteristics of each technology will be detailed.
•To obtain an overview of the main characteristics of the energy
storage technologies presented in this course and the differences
between them.
