Course material

1. Answer: Introduction An increase of 48% is predicted for primary
Answer:
Introduction
An increase of 48% is predicted for primary energy use in 2040, according to latest
projections. People are increasingly turning to renewable energy sources due to the limited
availability of fossil fuels and the damage they do to the environment. In order to restore
the natural balance and fulfill the rising energy needs of the world's population, renewable
energy sources such as solar radiation, ocean waves, wind, and biogas have been important.
This means that storing all three renewable energy sources has become more important
due to the erratic nature of our weather. A new generation of long-term energy storage
technologies must be developed to meet these needs. A major component of renewable
energy systems is energy storage. Dincer, I. (2011)
To create electricity, the stored energy may be used in a variety of ways, including heating,
cooling, and even generating power itself. The construction and industrial sectors rely
heavily on TES systems. Reduced carbon dioxide (CO2) emissions and decreased
investment and operational costs may be some of the benefits of incorporating TES into an
energy system. Improved efficiency and reliability may also be achieved. An advantage of
industrially produced solar thermal systems over efficiency-focused ones is that they make
use of the Sun's thermal energy during the day. There isn't enough (thermal) reserve to
keep it going when the sun isn't shining. It is becoming increasingly important to employ
TES for energy storage in combination with concentrated solar power (CSP) plants, where
solar heat may be preserved for use when sunshine is not available. In order to keep TES
systems up and running around the clock, new materials need to be found, defined, and
enhanced in their thermo-physical properties. According to estimates, the use of heat and
cold storage in Europe's construction and industrial sectors may save around 1.43 billion
GWh/year and save 400 million metric tons of CO2 emissions. In the words of S. Fujii:
(2022)
Increasing the solar percentage, appliance efficiency (such as the efficiency of PV thermal
collectors and absorber chillers), as well as energy consumption for heating and cooling
spaces, are all dependent on storage density (the amount of energy per volume or mass).
This means that PCMs (PCMs) might be utilized in solar system applications in the future.

2. Using PCMs, the solar storage capacity of tiny water storage tanks might be reduced or
increased for a given volume, potentially enhancing their energy density. (I. Dincer) (2011)
Thermal storage might be included on either the hot and also on cold side of the plant.
When the chiller absorption is in cooling mode, the collectors' hot water may be fed directly
into the chiller's auxiliary heater or straight to the users (in heating mode).
The chiller's absorbing cold water may now be used in building's cooling terminals thanks
to the second device. Temperature ranges can categorize "hot," "warm," and "cold" storage
scenarios. Temperatures in hot tanks range from 80–90 °C to 40–50 °C, whereas those in
warm tanks range from 40–50 °C to 7–15 °C [8].
When it comes to large-scale solar power facilities, cold storage might be justified because
of heating domestic hot water (DHW) generation. It isn't only the decreased energy prices
(in the case of electric compression chillers) that make cold storages advantageous; it's also
that they lower the cooling power installed and enable the chiller to run more continuously.
At first, thermal storage was unable to offer enough backup, although it did assist in the
system's thermal stabilization. Thus, thermal storage was used in solar-aided thermal
systems. There has been a surge in the research of TES technologies, as well as the use of
sensible and latent heat storage in a variety of applications. Rather of examining the system
as a whole, these evaluations concentrated on only one side (cold or hot).
For example, (Pintaldi et al. 2011) examined solar cooling system TES and control
techniques. Solar cooling applications with greater temperatures (>100 C) were the
primary focus of this research. Solar collectors and thermal energy storages for solar
thermal applications have been the subject of several studies by (Tian and Zhao2014).
There was a comprehensive assessment of PCM for cold storage Separately, the research
done by (Oró et al 2011) included air conditioning and even ice storage. ( Elmaazouzi,
Z. (2022)
Solar heat may be exploited to reduce building energy use and costs by using TES
technology such as those described in this study. Here are the fundamentals of several
energy storage techniques, along with formulas for estimating their storage capacity. The
utilization of water, packed-bed storage systems and subterranean, as sensible heat storage
(SHS) technologies is briefly examined. Lastly, cool thermal energy storage (TES) devices
are briefly discussed, and noteworthy information on their performance and pricing is
provided. (Elmaazouzi, Z. (2022)
Literature Review
The temporary or permanent storage of thermal energy at high or low temperatures is what
is meant by the term "thermal energy storage." Due to its importance in energy

3. conservation, this notion has been around for a long time and has been refined through
time.
Intermittent nature of the energy source means that effective and efficient energy storage
devices are required for effective and efficient use. Thus, the space heating and residential
hot water uses of solar thermal technology will be limited to their potential. (Yuqi,
H. (2022)
Efficient TES systems reduce thermal energy losses and provide high energy recovery with
little temperature deterioration during extraction of the stored thermal energy. There are
huge changes in solar radiation at high latitudes, and the variable space heating loads
predominate in cold climes due to the large fluctuations in energy consumption.
It is possible to significantly lower the cost of photovoltaic systems that may provide up to
100% of a building's energy requirements by using seasonal thermal energy storage. Such
systems are meant to capture solar energy throughout the summer and store the stored
heat for usage in the winter months. Since the application calls for huge, low-cost storage
volumes, ground heat exchangers were determined to be the most viable technology. (Pan,
Changyu (2022)
Despite the fact that these systems have been built and proven, it is difficult to reduce their
cost. The use of yearly storage on a community-wide scale might cut costs and increase the
dependability of solar heating. (Yuqi, H. (2022). Heating equipment may be more efficient if
thermal energy storage devices are used to counteract the mismatch between supply and
demand. Improved energy efficiency and cost savings are possible with properly built
systems.
It is possible that energy storage devices may make a substantial contribution to society's
desire for more efficient, ecologically friendly heating and cooling, space power, and utility
application usage. Efficient energy storage also has the benefit of being flexible, even if it
was originally intended to be used for solar energy storage. Waste water from power plants,
air conditioner exhaust, industrial process waste, and so on may all be utilized to store
excess energy. It becomes an energy sink into which we may dispose of any excess energy
that is not required at the time. Smaller homes may not be able to benefit from a shared
store like this, but large-scale central heating systems may. (Dincer, I. (2011)
It is not just the temperature that TES systems vary from one another, but also the heat
carrier, or heat transfer fluid (HTF). Water, air, and thermal oil are all examples of single-
phase HTFs, whereas water/steam is a two-phase system that includes a condensation and
evaporation process. Both the storage medium and the heat carrier might be the same thing.
An extra volume of hot working fluid is employed in the direct storage concept to store heat.
As long as the pressure in the medium is low enough to avoid costly pressure vessels and
the medium itself is affordable, this notion is cost-effective (e.g. water). (Ahmadi, A. (2022)

4. During the charging and discharging operation, the working fluid experiences a phase shift.
The energy in many working fluids must be transferred to another storage medium since it
cannot be stored directly in the fluid itself. As a heat transporter and a storage medium, two
distinct media are used.
Indirect storage is a common term for this notion. A dry pebbled bed made with air as a
heat transporter is an example of a storage media that may be directly in touch with the
HTF for indirect storage. Direct contact between a heat carrier and a storage media isn't
always an option since the carrier may be pressurized (such as steam) or incompatible with
the medium itself. An indirect contact design between the carrier and the store media may
be used in this situation. A heat exchanger inside the storage medium may be used to
achieve indirect contact. (Ahmadi, A. (2022)
Another classifying criterion is the number of tanks. The notion of a single tank is defined by
a number of distinct storage areas. A water tank or concrete block might serve as an
example of a practical heat storage system made of both hot and cold zones. Latent heat
storage systems based on a single tank filled with phase transition materials are another
example (PCM). The PCM of those storage is partially liquid and even solid in distinctive
zones during the charging and discharging procedure. Finally, when charging and
discharging, a single tank thermochemical storage system with a bed has zones containing
the reactant and the product. A tank's temperature distribution may not be even. In this
scenario, transitory heat transfer between zones with varying temperatures must be
handled. Thermal stratification is desirable for sensible heat storage in a single tank
because the value of high temperature heat is retained in one zone of the vessel with
restricted heat transfer to the cold zone. In other words, the stratification is lost over time,
even in well-insulated containers, owing to temporary internal heat conduction. Internal
losses must be minimized in order for the storage system to operate at its optimal efficiency
when parasitic transient heat conduction is present. 9 Fujii, S. (2022)
Alternatively, two tanks might be used in storage systems. As an example, a liquid-based
SHS system consists of two tanks with varying temperatures and fluid levels. If you're using
a thermochemical storage system, you may keep the result in one tank while the reactant is
in the other. Because the power needs are handled outside rather than inside the storage
volume, the two-tank idea has an advantage over single volume regenerative storage.
Thermal power needs might dictate the design of an extra heat exchanger or thermal
reactor for thermochemical heat. It is therefore possible to separate the thermal capacity
that may be kept in two tanks from the thermal power (which is stored in a single tank)
(additional external component).
The thermal power of a storage system must be distinguished. The typical discharge of the
storage system is determined by the thermal capacity over the thermal power (e.g., hours).
For example, cooling power electronics with a thermal mass in less than a second to a year

5. may be accomplished (e.g., seasonal hot water storage). CSP is now focusing on systems that
compensate for cloud transients and systems for daily charging and discharging systems
(typically up to 15 hours). It is important to keep in mind that various storage ideas result
in distinct discharge powers, temperatures, and pressures. The thermal power of a
regenerator-type store, for example, varies with time. That is to say, regenerator-type
energy storage devices provide thermal energy in discrete bursts. One such example is a
steam accumulator, which supplies saturated steam at varying pressures instead of a
continuous one. A continuous discharge procedure with minimum volatility in power,
temperature and pressure levels may be achieved using alternative storage ideas.
Alternatively (e.g. two tank molten salt concepts). (Fujii, S. (2022)
For the most part, TES systems fix the temporal mismatch between the supply and demand
of energy. TES systems may sometimes be used to adjust the local imbalance between
energy supply and demand. Examples include a thermal pack for beverage cooling and TES
systems in automobiles that might increase performance and human comfort when it is
chilly outside. An additional focus is on the transmission of thermal energy through
automobiles equipped with a TES (e.g., industrial waste heat recovery).
Major Classification Of Heat Storage
TES finds a position in thermodynamic systems due to its intermittent availability and
continual change in solar radiation. TES not only balances demand and supply by saving
energy, but also enhances the system's performance and thermal dependability. As a result,
it is critical to build efficient and cost-effective TES systems. However, only a few solar
thermal plants on a substantial scale have used TES. Additionally, research is being
conducted on the design of TES systems for different household solar applications.
Additionally, using a computational fluid dynamic technique is a widely utilized way for cost
savings, and FLUENT software seems to be effectively employed for a variety of engineering
applications.
Figure 1 major classifications of thermal storage systems
The factors capacity, power, and discharge time are all interconnected. Capacity and power
may also be interdependent in certain storage systems. Table below summarizes typical
TES system characteristics, including capacity, power, efficiency, storage duration, and cost.
Any storage system should have a high energy storage density and a high-power capacity
for charging and discharging. It is widely established that there are three techniques for TES
at temperatures between 40 and 400 degrees Celsius: sensible heat, latent heat related with
PCMs, and thermochemical heat storage associated with PCMs. (Dincer, I. (2011)
(Elmaazouzi, Z. (2022)

6. Figure 2 TES parameters
Figure 3 (a) sensible heat (b) latent heat (c) thermal-chemical reaction
The storage media used is determined by the nature of the procedure. Energy storage as
sensible heat in stored water is rational for water heating. If air-heating collectors are
utilized, it is recommended to store particulate matter via sensible or latent heat effects,
such as sensible heat in a pebble-bed heat exchanger. Passive heating utilizes storage as
sensible heat in the components of the structure. When photovoltaic or photochemical
methods are used, thermochemical storage makes sense. (Dincer, I. (2011)
Classifications Of Solution Thermal Storage Technologies
Classification of storage solutions technologies may be accomplished using a variety of
criteria. The picture depicts a categorization of energy storage methods depending on the
condition of the energy storage material.
The main technological concepts for thermal energy storage (heat/cold) are presented in
figure
Figure 4 thermal storage technological concept
With the exception of phase transition materials and thermochemical storage, the majority
of heat storage approaches share one fundamental difficulty. When heat or cold is charged
into or discharged from a store, temperature differentials between various regions of the
storage volume will occur. It is also critical that the storage medium maintains a structured
layer, with the hottest water on top and the coldest water at the bottom. If mixing happens
and the total temperature reaches some type of average value throughout the whole
volume, the effective storage capacity will be significantly decreased.
Water is the most often utilised liquid for sensible heat storage. Nowadays, due to its low
cost and ease of application, water storage technology is extensively employed in the area of
solar thermal engineering. (Pan, Changyu (2022)
Water has a reasonably high specific heat capacity and essentially little degradation during

7. thermal cycling. • Water is chemically compatible with the majority of confinement
materials (stable, mild, and non-corrosive chemical characteristics).
Due to the reasonably established theoretical and practical technology, sensible water
thermal storage has been employed for both short-term (diurnal) and long-term (seasonal)
thermal storage. Seasonal thermal storage provides a longer duration of thermal storage,
often three or more months. Thus, seasonal energy storage may completely exploit the
temperature differentials between summer and winter, satisfying or complementing both
seasons' heating/cooling needs. In comparison to short term thermal storage, seasonal
thermal storage maintains the storage material at a lower temperature than short term
thermal storage does in order to minimise thermal losses throughout the extended storage
period. The following are the benefits of water storage technology:
Water is a low-cost, easy-to-handle substance that is nontoxic, noncombustible, and
abundant.
Water has a relatively high specific heat and a dense structure.
Heat exchangers may be omitted if water is employed as the collector's heat carrier.
When pumping energy is limited, natural convection fluxes may be used.
It is possible to charge and discharge the storage tank concurrently.
A water system's adjustment and control are changeable and adaptable.
The Following Are The Downsides Of Water Storage Technology:
Water has the potential to freeze or boil; • Water is very caustic.
Working temperatures are restricted to less than 100°C and often must be much lower than
this boiling point.
Stratification of water is difficult.
Chemical additives may be used to combat freezing and corrosion. Despite the need for
pressure confinement, water may sometimes stay economically competitive at higher
temperatures, particularly when stored in aquifers. While organic oils, molten salts, and
liquid metals avoid the vapor pressure issue, they have significant drawbacks in terms of
handling, containment, cost, storage capacity, and practical temperature range. The
challenges and limits associated with liquids may be overcome by storing thermal energy as
sensible heat in solid materials. (Fang, G. (2022)
Storage Systems
Sensible Heat Storage
SHS (Figure 2a) is the simplest approach, since it relies on heating or chilling a liquid or
solid storage medium (e.g., water, sand, molten salts, or rocks), with water being the least
expensive choice. Water is the most widely used and commercially available heat storage
medium, with a variety of domestic and industrial uses. Underground heat storage in both
liquid and solid medium is also employed for large-scale applications. SHS offers two
primary advantages: it is inexpensive and eliminates the hazards connected with harmful

8. material usage.
The SHS system makes use of the heat capacity and temperature change of the storage
media during charging and discharging. The amount of heat stored is determined by the
medium's specific heat, the temperature change, and the quantity of storage material.
where Qs is the quantity of heat stored, in Joules; m is the mass of heat storage medium, in
kg; cp is the
specific heat, in J/(kg_K); ti is the initial temperature, in _C; tf is the final temperature, in _C.
Sensible Heat Storage In Liquids
Liquids have the benefit of being able to be used as a storage medium as well as a heat
transmission fluid.
Water and thermal oil are the most often used media in this regard. The liquid storage
technique may be implemented as a single tank or as a two-tank design. The two-tank
approach utilizes two distinct tanks with varying temperatures and fluid levels. Thermal
stratification is desirable in a single heat storage vessel because it preserves the value of
high temperature heat in one portion of the vessel while allowing low-temperature fluid
(like backflow from a heat consumer) to be kept in another. The solid filler components may
inhibit free convection inside the liquid, hence enhancing thermal stratification.
Stratification is broken over time, even in extremely well insulated containers, due to
parasitic transitory internal heat conduction. For media other than water, the liquid storage
medium often accounts for the majority of the total cost of the storage system. In certain
instances, inexpensive solid filler materials may be used in lieu of more costly liquid storage
materials (e.g. cast iron in oil or molten salt thermocline designs). Due to the fact that the
liquid and solid filler come into close touch, their compatibility must be assured. (Dincer, I.
(2011)
Table below summarizes many distinctive liquids and their thermophysical characteristics
at atmospheric pressure. Molten alkali metals such as sodium (Tm = 98o C) and sodium-
potassium might be employed in high-temperature storage systems. These metals have
been used in the design of nuclear reactors. The excellent thermal stability and thermal
conductivity of these metals are significant benefits. However, at extreme temperatures,
alkali metals exhibit a high degree of reactivity with air and water, necessitating the use of a
well-built containment.
Table 1 thermal storage properties of different liquid materials

9. High Temperature Water Systems
The steam accumulator technique is state-of-the-art for thermal storage in direct heat
applications (also called the Ruths storage systems). Thermal energy is stored in pressured,
saturated liquid water in steam accumulators. They take use of the large volumetric storage
capacity of liquid water for sensible heat. During discharge, the saturated liquid's pressure
is reduced, resulting in the generation of steam. The pressure vessel's volume limits its
capacity since water is employed as both a storage medium and a working medium. This
results in high discharge rates. The critical point of saturated water (374°C, 221 bar) limits
the maximum temperature. The pressure vessel accounts for the bulk of the expenses.
The amount of energy storage now used in the process sector is still small, but steam
accumulator technology accounts for the vast majority of that capacity. Liquid water's
exceptional capacity to store energy is used by utilizing pressure vessels for tanks (Figure
5). Condensation of steam delivered into the pressured liquid volume charges steam
accumulators (Goldstern 1970, Steinmann 2006). Because the pressure vessel is filled with
saturated liquid water, the pressure rises as the charging procedure is completed. –
Excessive pressure is reduced during discharge, and saturated steam is recovered. Liquid
volume change in sensible energy when discharging is what determines storage capacity.
Saturated steam may be discharged only at a certain pressure, and a change in temperature
correlates to a change in this pressure. (Fang, G. (2022)
While volumetric storage capacity may benefit from a bigger fall in pressure, the
permissible pressure fluctuation may be limited by efficiency concerns. When operating at
greater pressures, the pressure drop during the discharge process is increased to supply the
same amount of energy because the logarithmic relationship between saturation pressure
and saturation temperature increases the absolute pressure drop. The size of the pressure
vessel determines the cost-effective steam accumulator capacity. It is possible to employ
this idea as buffer storage to compensate for cloud passage or to support other storage
concepts that exhibit a greater storage capacity but need a lengthier startup process
because of the low response time. (Fang, G. (2022)
Figure 5 steam accumulator
Molten Salt Systems
Molten salts are good candidates for sensible heat storage in liquids when temperatures
rise over 100°C. Molten salts have inexpensive prices, great thermal stability, and low vapor
pressure as their main benefits. There is no need for a pressurized tank because of the low

10. vapor pressures.
A variety of industrial processes including heat treatment, electrochemical reactions, and
heat transmission have all used molten salts in the past. The melting point of salts must be
taken into account while applying them.
Unwanted freezing of molten salts during operation is a severe problem. The pipeline, heat
exchanger, and storage tanks must be protected against freezing. As a result, additional
heating systems may be necessary. High prices of storage medium, corrosion danger, and
difficulty in managing hygroscopic salts are among possible drawbacks of molten salt
storage. The salts' maximum operating temperature is determined by their thermal
stability. A lower melting temperature is achieved by using salt combinations, rather than
single salts alone. It is possible for these mixes to have the same thermal stability as the
individual salts in them. This means that eutectic salt mixes have a greater temperature
range than single salts. (Dincer, I. (2011)
Alkali nitrate salt combinations, and to a lesser extent alkali nitrite salts, are the preferred
fluids for TES in solar thermal power plants. When using non-eutectic salts, it is common
practice to use 60wt%/40wt% sodium/potassium salts respectively. Solar salt is the
popular name given to this combination. When heated to 550 degrees Celsius, the eutectic
mixture will no longer be stable because of its high melting point.
Figure 6 molten salt thermal storage plant
Latent Heat Storage
Phase change materials (PCM) are also known as materials for the storage of latent heat
because they can change their physical state from solid to liquid and back again. When a
solid melts, heat is absorbed, and when a liquid solidifies, heat is released. This is known as
phase transition. Tm is the melting point at which phase shift occurs. When heated to this
degree, certain materials begin to melt, but their temperature does not increase. In this way,
the heat that has been injected seems to be latent and undetectable. (Luo, C. (2022)
The most significant benefit of latent heat storage is the ability to store energy in a small
temperature range close to the phase transition temperature.
The storage of latent heat may also be addressed when a crystalline structure changes from
one form to another without undergoing a physical phase shift. Heat of solid-solid phase
shifts is often lower than that of melting and solidification, however this is not a universal
rule.

11. In spite of its high enthalpies, the liquid-to-gas phase shift cannot be used to store latent
heat because of the gas phase's massive volume As a result, the heat generated during the
solid-to-liquid phase transition is often used.
When a material is heated from an initial temperature T1 to the melting temperature Tm
and the melt is further heated to T2,
Latent Heat Storage System
Overflow steam from solar heaters is used to warm large tanks of water during the hottest
parts of the day. Steam may be bled from these tanks when the power grid needs a rapid
rush of electricity. Short response times to turbine demand are achieved by using water as
both a working media and a heat storage medium. The sooner the superheated water boils,
the greater the reduction in turbine steam pressure. In the lexicon, they are known as buffer
systems. When pressure is lowered, superheated water becomes unstable and quickly boils
over. In the case of a tank burst, it is exceedingly hazardous. Water at 200 °C will be
transformed into water at 100 °C and a big amount of steam at one atmosphere of pressure
if it ruptures . Boiler explosions have regularly resulted in the demolition of big structures
as a consequence of this quick change. ( Pan, Changyu (2022)
Materials
Properties
The ideal temperature for a phase transition
A high enthalpy of phase transition
Thermal stability and vapor pressure at the highest operating temperature that is adequate
for the application
There is little or no subcooling during freezing, no supersaturation, and no segregation (e.g.,
like Glauber's salt) if sensible heat is also employed.
When designing a latent heat storage system, the first step is to choose the PCM. There
should be a temperature range that corresponds to the intended use. Using organic PCMs in
the range of temperatures below 120 °C is possible. Organic PCMs' long-term thermal
stability, oxygen reactivity, and high vapor pressure are all crucial at temperatures
exceeding 120 °C. Hermetically sealed storage solutions may help mitigate some of the

12. drawbacks. Inorganic materials have a better thermal stability by definition. Solid-liquid
phase transitions of inorganic anhydrous salts are mostly studied at temperatures ranging
from 120 to 1000 degrees Celsius. Anhydrous salts' solid-solid phase transitions have
received less attention (e.g. Na2SO4). Table below lists a variety of solid-liquid phase
transition materials and their thermo-physical characteristics.
Table 2 PCMs properties
Chemical Heat Energy Storage
The enthalpy change of a reversible chemical process is used to store chemical energy.
Because of its ability to store energy at densities up to four times greater than those of other
TES, these devices are attracting attention. Thermal losses may be avoided by storing the
product and the reactants at room temperature.
Thermochemical storage, unlike sensible and latent heat systems, may be charged and
discharged at various temperatures. As a result, heat may be upgraded and downgraded,
and it can be supplied at an appropriate temperature. Heat transformers and chemical heat
pumps are examples of systems without storage capacity. Low-temperature heat is
absorbed by heat transformers, which in turn deliver heat at a higher temperature. In
chemical heat pumps, the heat is absorbed at a higher temperature and dissipated at a
lower one (Garg 1985). Heat transformation/chemical heat pumps and thermochemical
storage are linked even though these systems do not aim for heat storage.
An endothermic process produces chemical molecules A and B, which are then recombined
in an exothermic reaction to release the stored energy (Equation below). It's possible to
physically separate the components A and B at high enough temperatures to make this
happen.
The enthalpy of the reaction is equal to the heat stored and emitted. Latent heat storage
enthalpies and sensible heat stored over a suitable temperature range are substantially less
in comparison to the enthalpy of reaction ?Hr. Thus, thermochemical storage materials have
a substantially higher storage density than latent or perceptible heat storage materials
(Wenthworth 2013, Mar 2011, Sizmann 2010). Compared to sensible and latent heat
systems, thermochemical energy storage technologies are at an early stage of development.
Low-temperature sorption systems are an exception to this general rule.
One of the most common types of thermochemical storage systems is a two-tier system.
Open-type systems allow gases to be exchanged with the outside world. Gases are emitted
into the atmosphere during the charging process. Discharging uses gas from the
surrounding environment.

13. As a result, these systems may run without the need for gas compression and storage, which
reduces system complexity and lowers operating costs. Oxygen, nitrogen, water vapor, and
maybe carbon dioxide are among the gases.
Unwanted contaminants from the environment may enter open systems. Dust, sulfur
dioxide, carbon dioxide, and organic molecules are only a few examples of impurities.
Substances like these have the potential to degrade system performance. Filter-based
system designs may alleviate these issues. Because of the unacceptably huge gas volume, it
is typically not possible to store the unpressurized gas phase in a closed type system. The
gas is often compressed or condensed in closed systems. It is then possible to store the
compressed gas or liquid with ease. By way of a second chemical process, the gas may be
reabsorbed
Figure 7 simple chemical heating system
Thermochemical Energy Storage Types
Figure 8 Thermochemical energy storage types
Solid-Gas Reaction
When heated, several solid compounds may undergo dissociation. While the depleted solid
is still in the reactor, a gas is released (this is known as an endothermic reaction, or
charging of the store). If the equilibrium is disturbed by a fall in temperature or a rise in
pressure, the parasitic reverse reaction will take place on its own. As a result, the
dissociation products must be kept in different containers. The solid and gas are
recombined in the exothermic process for discharge. For thermochemical energy storage,
there are many different kinds of gas-solid reaction systems.
Liquid-Gas Reactions
The interaction between NaOH and water is being studied for use in seasonal household
heating. Concentration of NaOH is used to charge storage devices (water release). Water is
absorbed by the concentrated NaOH for emptying storage tanks (Weber 2008). In
automobiles, the similar reaction has been used since 1880. Trains between (Jülich and
Aachen in 1882) ran on the "caustic soda locomotive" or "Honigmann locomotive"
(Beckmann 1984).

14. Gas-Gas Reaction
The use of a catalyst in gas-gas reactions is often necessary to achieve high rates of reaction.
Example gas-gas reactions with the reaction temperature and the reaction heat as a
function of the educt reactant.
Modern Trending Technologies In Thermal Heat Storage
A project under development, termed Adsorb (Advanced Distributed Storage for Grid
Benefit), the goal is to show an energy-efficient, modular system that might also alleviate
the strain on national energy infrastructure. The system may either be installed in new
construction or retrofitted into existing buildings..
Loughborough University has pioneered two forms of innovative thermal energy storage
technologies that the team will be testing. You can store for weeks or months without losing
any heat with Thermochemical Storage (TCS). A heat pump, electrical heating element, or
solar thermal collector are all examples of thermal sources that may be used to dehydrate
an active material, which then charges the thermal storage. System cooling and energy
storage are both possible once the system has been charged. Moisture is reintroduced as
necessary, which subsequently releases heat for usage in the house.
Phase Change Material (PCM) is the second technology (PCM). Thermal energy may be
stored in this way on a daily basis at densities that are hundreds of times higher than those
now available. Heating a chemical storage to make it liquid is another use for a thermal
source in the PCM system. Latent heat may be stored in this way for days. By flowing lower-
temperature water through the system, the heat held may be released and used for hot
water or space heating.
They may drastically lower customer costs and solve the intermittent issue by combining
sophisticated control systems with these technologies. This would increase the use of
renewable energy sources and minimize the carbon footprint of the United Kingdom's
energy supply. (Kalbande, V. P. (2022)
Heat Pump
In a nutshell, what a heat pump does is transport heat from one location to another. We can
see this in our refrigerators, where a liquid is evaporated and cooled to reduce the
temperature of our food compartments. It is now possible to utilize this technology to
harvest the potential thermal energy in the air outdoors, or even from the ground, sending
it straight into your house where it is compressed, and the heat is transmitted via a series of
coils. It may seem as though it's a work of magic, but the physics behind it is really rather
straightforward.

15. When it comes to efficiency and cleanliness, heat pumps are regarded to be among of the
most effective and environmentally friendly devices on the market today. They are most
suited to temperate regions like the UK, where they can offer warmth even in temperatures
as low as -20°C. It's becoming more and more common for heat pumps to be used in
contemporary construction because of its ability to collect heat from either air or
ground/water.
To keep our homes and workplaces cozy, heat has the ability to naturally transition from a
high to a low temperature. When you utilize a heat pump, you reverse this process by
employing some basic science that pulls outside air, heats it, and then feeds it into your
home.
Taking an example that a reversible heat pump has a COP =3.0 (coefficient of performance),
assuming that the compressor will be consuming 1500 W,
The amount of heat that the heat pump can add to a room can be calculated as,
From this, it shows that the it consumes 1500W of electricity and converts it to 4500W of
heat in a room.
An impeller or fan draws outside air over a set of coils containing refrigerant on the exterior
of an air source heat pump. Coils of refrigerant heat up and begin to evaporate as a result of
the heat they absorb. The temperature of this gas rises considerably once it is compressed
by a compressor.
The heat is then disbursed via a series of inner coils throughout the structure. In the
meanwhile, the refrigerant returns to the atmosphere, where it is heated more and the cycle
is repeated. Heating water for radiators or dispersing it around the structure is another
option for using the beneficial heat generated by the boiler.
In contrast to air source heat pumps, which get their energy from the air, ground source
heat pumps draw their energy from a body of water. Closed loop systems for the earth and
open loop systems for water are used in these systems. Refrigerant flow in closed loops
mimics that of air source pumps, while water flow in open loops mimics that of a well or
lake. (Kalbande, V. P. (2022)
Absorption heat pumps, which function in the same manner as air-source heat pumps, but
utilize ammonia instead of a refrigerant, are an option for bigger installations. With recent
advancements, they are becoming increasingly commonplace in large commercial and

16. residential establishments.
The ductwork used to transport heat from the heat source to individual rooms in the home
is another important part of any heat pump. If you're remodeling a home, ductwork may be
a major headache since it's intrusive and costly. Mini-split heat pumps, which are easier to
install, are becoming more popular in residential settings.
Thermodynamic panels, which use both air and solar radiation to heat water and rooms, are
one of the most recent developments in heat pump technology. These are often installed on
the side of a home, but they may also be seen on the roof, resembling solar panels.
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