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A. Bhattacharya
units to large scale solar power plants. One of the major drawbacks of solar energy is
its intermittent nature. Not only the solar energy is unavailable at night, during daytime also the availability of solar insolation varies significantly depending on local
weather pattern and cloud formation. This necessitates the use of suitable energy
storage devices which can distribute the available energy evenly over the required
time period.
11.1.1 Types of Energy Storage
In the recent past, several forms of energy storage devices have been proposed. Energy
storage devices can use different mechanisms for energy storage and can store the
energy in different forms such as chemical energy, mechanical energy, thermal energy
and electrical energy. The suitability of the type of energy storage device depends
on the mechanism of solar energy collection. For example, thermal energy storage
devices may be better suited for solar thermal power plants while chemical energy
based batteries or electrical storage units may be more suitable for direct electricity
generation through the use of photovoltaic (PV) cells. Other important factors such
as safety, ease of installation and operation and maintenance costs also need to be
accounted for. Out of all the different modes of energy storage proposed, thermal
energy storage systems show a lot of potential and have been studied widely.
11.1.2 Thermal Energy Storage Systems
Thermal energy storage systems are systems which store energy in the form of heat.
Depending on the form of energy storage, thermal energy storage systems can be
classified into sensible heat based systems and latent heat based systems. Sensible
heat based systems, such as molten salt thermocline systems, store the entire energy
by temperature increase of the storage medium. Various designs have been studied
such as single medium storage where the heat transfer fluid itself acts as the storage
medium. On the other hand dual media systems have a filler material in addition to
the charging and discharging fluid which is cost effective for large systems. Latent
heat based systems store energy in terms of latent heat transfer during phase change
process. It consists of a suitable material which melts and solidifies at the required
temperature and stores energy during melting and releases it during solidification.
Compared to other forms of energy storage, latent heat energy storage (LHES)
systems have high storage densities which leads to smaller overall system sizes.
Also, as the phase change process occurs at a constant temperature or over a narrow
band of temperature, LHES systems can be designed to operate at specific required
temperatures. Various materials have been used for LHES systems ranging from
organic compounds such as fatty acids and esters to inorganic salts, collectively
called as phase change materials (PCM). A classification of different types of PCM
A. Bhattacharya
units to large scale solar power plants. One of the major drawbacks of solar energy is
its intermittent nature. Not only the solar energy is unavailable at night, during daytime also the availability of solar insolation varies significantly depending on local
weather pattern and cloud formation. This necessitates the use of suitable energy
storage devices which can distribute the available energy evenly over the required
time period.
11.1.1 Types of Energy Storage
In the recent past, several forms of energy storage devices have been proposed. Energy
storage devices can use different mechanisms for energy storage and can store the
energy in different forms such as chemical energy, mechanical energy, thermal energy
and electrical energy. The suitability of the type of energy storage device depends
on the mechanism of solar energy collection. For example, thermal energy storage
devices may be better suited for solar thermal power plants while chemical energy
based batteries or electrical storage units may be more suitable for direct electricity
generation through the use of photovoltaic (PV) cells. Other important factors such
as safety, ease of installation and operation and maintenance costs also need to be
accounted for. Out of all the different modes of energy storage proposed, thermal
energy storage systems show a lot of potential and have been studied widely.
11.1.2 Thermal Energy Storage Systems
Thermal energy storage systems are systems which store energy in the form of heat.
Depending on the form of energy storage, thermal energy storage systems can be
classified into sensible heat based systems and latent heat based systems. Sensible
heat based systems, such as molten salt thermocline systems, store the entire energy
by temperature increase of the storage medium. Various designs have been studied
such as single medium storage where the heat transfer fluid itself acts as the storage
medium. On the other hand dual media systems have a filler material in addition to
the charging and discharging fluid which is cost effective for large systems. Latent
heat based systems store energy in terms of latent heat transfer during phase change
process. It consists of a suitable material which melts and solidifies at the required
temperature and stores energy during melting and releases it during solidification.
Compared to other forms of energy storage, latent heat energy storage (LHES)
systems have high storage densities which leads to smaller overall system sizes.
Also, as the phase change process occurs at a constant temperature or over a narrow
band of temperature, LHES systems can be designed to operate at specific required
temperatures. Various materials have been used for LHES systems ranging from
organic compounds such as fatty acids and esters to inorganic salts, collectively
called as phase change materials (PCM). A classification of different types of PCM