Thermal energy is produced due to the vibration of molecules. It is also referred to as internal energy or enthalpy. In thermodynamics, heat is a form of energy transferred to or from a thermodynamic system by mechanisms that do not belong to the thermodynamic system. On the other hand, enthalpy is the form of energy that exists within the system. Thermal energy is produced due to both heat and enthalpy. This means heat is responsible for the movement of particles in a system, which results in the vibrations of particles, increasing the enthalpy.
We can store thermal energy to use up too many hours, days or even months. There are different technologies by which we can store thermal energy. The type of technology used depends upon the thermal energy production method, the reason it needs to be stored, and the amount of energy produced.
Some common uses of thermal energy storage include storing hot water in the daytime to be used in the night, storing summer heating for winter heating, etc.
We can store thermal energy in water or ice tanks, earth or bedrock, boreholes, etc. Other storage sources include heat pumps, low-cost electric power, power storage in renewable electric power plants, etc.
All types of thermal energy should be stored so that more renewable energy is produced. Furthermore, since thermal energy storage is possible in common houses, we must store it to reduce pollution and save the environment.
Thermal energy storage is a technology through which we can store heat energy, water or ice energy or cold air and transfer it whenever we want. This is used most widely in present days and complements energy produced by solar and water.
There are three types of thermal energy storage: sensible heat storage plants, latent heat storage plants and thermos-chemical heat storage plants. Each of these is used depending upon the need and budget.
In a thermal energy storage plant, the heat energy or water energy is stored in large tanks when there is no demand for electricity. Then, when there is a surge in demand, the energy is released to use from the distribution facility.
The storage tank to store thermal energy is designed very carefully. They are designed in such a way that no heat must be dissipated through the tanks. Diffusers are attached to the tanks to reduce turbulence and maintain the temperature of the stored thermal energy.
Let us study the working of thermal energy storage with an example. Do we know how we feel cool in a large building or shopping mall? Do they have so many air-conditioners? Well, certainly they did not have so many air-conditioners installed. They take the help of thermal energy storage to cool the entire building. This is how they do it:
When there is not much demand, water and 25% ethylene glycol are mixed and cooled down inside a chiller during the nighttime. This solution is circulated inside a heat exchanger that consists of lots of ice to freeze the water up to 95%.
Ice is also formed around the heat exchanger tank with the help of heat exchanging tubes. This formed ice also acts as a preventive control to safeguard the tank from damages. The heat exchanger takes a minimum of 6 hours and a maximum of 15 hours to form the ice.
During the daytime, the heat exchanger continuously circulates the glycol solution with the help of ice from the storage tank to be delivered to the required people. The glycol solution is then transferred at the desired temperature to the cooling coil present in the air.
The fan blows cool air from time to time on the coils to cool the occupant spaces. This is how people feel cold in the entire building without knowing that actual air-conditioners do not work in the large building. This also cuts down the cost of cooling and saves energy.
While some buildings may use real air-conditioners, they must adopt the thermal energy storage method as it is more eco-friendly and less harmful.
1. Thermal energy storage is widely used in concentrating solar power plants to supply power at night.
2. It is used in thermal power plants to balance rapid and excessive load fluctuations.
3. Thermal energy storage provides security to heat supply in combined power and heat plants.
4. It is used to store energy or heat that can be used at a later stage. This prevents wastage of energy.