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Why do we want to store thermal energy? Thermal energy storage makes it possible to:
- use alternative energy sources which
are available at times when energy is not needed. For example, solar energy can be saved
for night use.
- reduce the size of energy production
equipment. Energy can be produced and stored during off-peak hours.
How can thermal energy be stored?
Thermal energy can be stored in
several different ways:
- Traditionally as sensible heat,
i.e. by heating and cooling a material such as water. The material is heated to a higher
temperature at loading and cooled down at deloading. Water is a common material for
sensible heat storage at temperatures between 5 and 100 °C. An every day example is the
warm water accumulator.
- In Phase Change Materials (PCMs)
utilising the latent heat of a material. Every time a material changes phase (e.g
from solid to liquid, liquid to vapour etc.) heat is given off or taken up. For example,
when an ice cube melts in a drink heat is required and is taken form the liquid which is
cooled. The heat of melting is 80 to 100 times larger than the heat required for heating a
material one degree. The use of liquid-vapor phase change further increases the energy
density.
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SOLID |
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HEAT |
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LIQUID |
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- Using the heat of reaction,
i.e. the heat released or required during a chemical reaction. The reaction must be
reversible, i.e. possible in both directions. The chemicals can be stored separately and
mixed when heat is needed. The use of chemical reactions for thermal energy storage
expands the temperature range for storage and also increases the possible energy density
in the storage.
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From PhD thesis by J. Millette from
University of Sherbrooke - Mechanical Engineering |
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Where can PCMs and chemical
reactions be used for thermal energy storage? PCMs and chemical reactions for thermal
energy storage are, for example, possible to use in the following areas:
- Residential heating and cooling
- Green houses
- Office heating and cooling
- Industrial District heating and
cooling
- Telecom and computers
- Cold storage in food stores
- Cold bags, warm keeping, medical
wraps etc.
- Cold transport
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Source: Chemical
Engineering and Technology, Royal Institute of Technology
Last updated:
2000-06-15 webmaster@ket.kth.se |
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