A thermal energy storage system can be used to store thermal energy in a thermal reservoir. Storing thermal energy in a thermal reservoir is well known. There are a multitude of reasons for storing energy in a thermal reservoir, among them: If it is desired to be able to reliably draw thermal energy of a level or amount, it is normally easier and less energy consuming to store the thermal energy.
A reason for using a thermal energy storage system is that it is not always possible to control the production of thermal energy. This could be the case if the system is connected to an unreliable source, for example, a solar collector. If the sun is shining it can provide thermal energy in the form of hot fluid, but during night it cannot provide thermal energy. Storing the thermal energy makes it possible to have thermal energy available during the night.
Another reason could be that there is a need to draw a lot of thermal energy over a short period of time which is normally not possible for the thermal energy supply system to provide. A thermal energy storage system can then provide the required additional thermal energy.
Yet another reason for using a thermal energy storage system is that it is easier to control and optimize if a steady and reliable supply of thermal energy is required.
Thermal energy storage systems are, for example, used in heating systems of buildings and houses, where they supply hot fluid to radiators and other heaters to heat the building or house and supply hot tap water.
It is well known in the art to use water containers to store hot water for heating up a house and provide hot tap water. Water stratification occurs when cold and warm fluid form layers that act as barriers to water mixing because the density changes as the temperature changes. Normally it is preferred that the water container is hot in the upper part and cold in the bottom part, which will occur by natural conduction and/or natural circulation of the water in the container. Hence the thermal energy distribution in the container can be changed and thus be optimised. It is also known to have different kinds of inserted devices in the container that passively enhance the stratification process of the container. This could be plates or segments that act as separators and enhancers for the stratification process.