Energy Storage - Review and Discussion

Running Head: Energy Storage – Review and Discussion
Title: Energy Storage – Review and Discussion
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Date of submission: 27/05/2019
Authors Note
The current report is presented as part of the requirements to complete the course work.

Energy storage - Review and Discussion 2
Introduction:
Contemporary developments in the technology applications have created need for
complex and more effective energy storage requirements. As of now energy applications are
utilizing diverse energy sources viz., mechanical, electrical, chemical, thermal etc. The
selection of particular type of energy source and storage means depends on the specific
energy application and will depend on the environment in which the energy storage device is
working in. The key objectives of the energy storage systems consists in general developing a
more resilient energy storage technology as well developing technologies those are cost
effective too. New energy storage requirements like renewable energy applications called for
development of different energy storage systems(Guney and Tepe 2017,P,1190).
Technological advancements coupled with the invention of more advanced materials is
enabling these objectives getting fulfilled. The following part of the discussion is focussed
on the evaluation of diverse energy storage applications and will critically discuss the
technologies in usage, the status quo of each of these technologies. Further the future
prospects and the possible developments in the energy storage technologies are discussed in
detail.
Overview of Energy storage devices and Technologies in use:
Mechanical Energy storage systems: Mechanical energy storage systems will utilize the
principles of mechanical energy generation and storage to save energy in this form. Typically
in the scenarios, like when off-peak electrical energy is available, the energy generated will
be stored in mechanical energy format and it will be re-tapped back in the peak times when
electrical energy is not sufficient to meet the demands. Some of the strategies being
employed at present for mechanical energy storage means is flywheel energy storage (FES)
where in the flywheel will receive the energy and will store it in the form of rotational energy
in that(Arani et al 2017,P.16). Typically Flywheel will function as a reservoir of energy in
this condition. Pumped hydropower storage (PHS) contained in employing the excess energy
to pump the hydro fluid to higher potentials, from where at the times of energy needs, the
fluid at higher potential will be utilized back into kinetic energy forms. Compressed-air
energy storage is contained in compressing air when cheaper off peak power is available, the
compressed air will then get transported into the chambers specially created for the storage of
the compressed air and subsequently this will be employed back to generate power, when

Energy storage - Review and Discussion 3
electrical energy is not available as per the energy demands. The efficiency of operation of
PHS systems is about 75 to 80%. CAES system advantage lies in the fact that the energy that
can be employed for power generation can be reduced by about 40% when CAES based
compressed air storage systems is employed. However the availability of underground
storage means like abandoned mines etc needed for such storage means. It is feasible to
employ this technology when supporting geographical systems are available for energy
storage. Carbon reinforced fibre materials and nano carbon tube based materials are some of
the materials that are being employed for Flywheels at present to enable more strength and
subsequent higher energy storage. Hydro-energy systems can be employed for convenient
energy retrieval for convenient time gradient. Flywheel energy storage is cheaper and can be
employed for energy flows without interruption. However the limitations include frictional
losses in the FES, material limitations for high intense energy storage. For hydro pumped
energy storage applications, need for large space and investments for large reservoirs makes
up the limitations. Further for compressed air energy storage requirements the key limitations
include topological requirements that the air storage requires. In any case the mechanical
energy storage is one of the pioneer energy storage technology and is much simpler.
Thermal energy storage systems: Thermal energy storage (TES) systems comprise usage
of thermal energy conversion and phase change principles(Alva et al 2017,P.699) The excess
energy available at different process operations can be tapped, like in the case of waste heat
recovery applications, solar energy utilization applications and energy saving in the buildings
etc. Energy available at each of these channels will be utilized later for the sake of either
heating up the temperature of the storage material or the energy available can be employed
for the sake of melting the phase change material employed for the thermal energy storage
system(Amrouche et al 2016,P.369). In the first case, the thermal energy storage systems is
termed as sensible heat storage system and in the second case it is called as latent energy
storage system(Sarbu and Dorca 2019, P,60). In any case in the later times when there is need
for energy tapping the heat contained in the storage material will be retrieved back either by
cooling it down to room temperature or alternatively it can be solidified by letting it to
liberate the energy contained in it. The key detriment in the adoption of the particular
sensible heat storage system is the cost of the material employed for thermal storage as well
as the physical properties of the same. At low temperature range of applications like in the
case of 100 degree Celsius and below, water can be used as cheapest energy storage
application. It has low cost and has capacity to take up sufficient thermal capacity to store

Energy storage - Review and Discussion 4
higher energy contents. For higher temperature range variety of materials are available at
present, combination of oils and hydraulic substances are being employed for higher
temperature heat storage applications. Even materials like clay, sand etc are feasible to get
employed as thermal energy storage means. Phase change materials (PCM) like molten
metals(Fernandez et al 2017,p.276). Eutectic Aluminium- Silicon Alloy Al-Si12 can storage
energies beyond 560 degree Celsius and more. Other important group of TES is Thermo-
chemical energy storage systems. In these systems the thermal energy received by the
material will be employed to store energy in the form of chemical bonds. Energy will enable
dissociation and again rebonding facilitates energy release in these materials. Hydration of
salts is a good example for energy storage and retrieval in this category of thermo-chemical
energy storage systems. Solar pond is a special group of thermal energy storage system which
can be employed for low range temperature energy storage. The solar pond is cheaper in cost
and will also work on to tap the energy and will provide the same for energy utility
applications(Aneka and wang 2016,P.367). Any quantity of thermal energy storage can be
done employing the solar pond technologies. However the application is limited to solar
energy storage. The recent developments in the technology include using different
combination of salts to improve the overall performance of the pond performance. Both
sensible thermal energy storage as well as latent heat thermal energy storage
principles(Geissbuhler et al 2016,P.660) are being employed in this technology(Aydin, casey
and Riffat 2015,P.359).
Figure 1 Principle of PCM based energy storage
Electrical energy storage systems: Electrical energy storage systems gained prominence
with wide spread usage of renewable energy generation systems like photovoltaic devices as
well as wind energy generation systems. Electrical energy storage systems employed in this
connection will have capacity to store energy and supply them back at times of instable