
There are several types of STES technology, covering a range of applications from single small buildings to community district heating networks. Generally, efficiency increases and the specific construction cost decreases with size. UTES (underground thermal energy storage), in which the storage medium may be geological strata ranging from earth or sand to solid bedrock, or aquifers. UTES technologies include: [pdf]
Image showing heat loss from a house. New research on thermal energy storage could lead to summer heat being stored for use in winter. Credit: Active Building Centre, Swansea University Funding to research thermal energy storage that could cut bills and boost renewables.
Generally speaking, seasonal thermal energy storage can be used by storing summer heat for winter use or storing winter cold for summer use, i.e., summer heat for winter use and winter cold for summer use. Common seasonal heat storage includes seasonal sensible heat storage, seasonal latent heat storage, and seasonal thermochemical heat storage.
Revelation of economic competitiveness of STES against existing heating options. Seasonal thermal energy storage (STES) holds great promise for storing summer heat for winter use. It allows renewable resources to meet the seasonal heat demand without resorting to fossil-based back up. This paper presents a techno-economic literature review of STES.
Direct seasonal thermal energy storage is more complicated because of the large number of PCMs storage units installed inside the tank and the high cost of heat insulation. Therefore, most of the current direct latent heat storage is based on short-term heat storage, and very few studies are aimed at long-term heat storage. Fig. 2.
Common seasonal heat storage includes seasonal sensible heat storage, seasonal latent heat storage, and seasonal thermochemical heat storage. Among them, both sensible and latent heat are used to store solar energy directly in the material.
Warm-temperature seasonal heat stores can be created using borehole fields to store surplus heat captured in summer to actively raise the temperature of large thermal banks of soil so that heat can be extracted more easily (and more cheaply) in winter.

The different kinds of thermal energy storage can be divided into three separate categories: sensible heat, latent heat, and thermo-chemical heat storage. Each of these has different advantages and disadvantages that determine their applications. Sensible heat storage (SHS) is the most straightforward method. It simply means the temperature of some medium is either increased or decreased. This type of storage is the most commerciall. Other sources of thermal energy for storage include heat or cold produced with heat pumps from off-peak, lower cost electric power, a practice called peak shaving; heat from combined heat and power (CHP) power plants; heat produced by renewable electrical energy that exceeds grid demand and waste heat from industrial processes. [pdf]
Heat storage, both seasonal and short term, is considered an important means for cheaply balancing high shares of variable renewable electricity production and integration of electricity and heating sectors in energy systems almost or completely fed by renewable energy.
Thermal energy can generally be stored in two ways: sensible heat storage and latent heat storage. It is also possible to store thermal energy in a combination of sensible and latent, which is called hybrid thermal energy storage. Figure 2.8 shows the branch of thermal energy storage methods.
As thermal energy storage is performed based on the heat changes in an energy storage medium, first, we need to define the branch of heat. There are two types of heat change in a material: sensible and latent heat. When energy is released from a material, the temperature of that material decreases.
It is possible to store any type of energy in heat storage systems. For instance, solar energy can be stored in the form of sensible heat in solar domestic hot water systems or solar ponds. In the cold thermal energy storage systems, electricity load can be stored. Also, heat storage can be used in the organic Rankine cycle to store electricity.
Chemical heat storage systems use reversible reactions which involve absorption and release of heat for the purpose of thermal energy storage. They have a middle range operating temperature between 200 °C and 400 °C. Below equation represents a generic chemical equation for TES function .
There are several applications for heat storage systems in residential and industrial settings. It is possible to store any type of energy in heat storage systems. For instance, solar energy can be stored in the form of sensible heat in solar domestic hot water systems or solar ponds.

Electric energy storage for heat can be achieved through electric storage heaters1and electric thermal storage heaters2:Electric storage heaters use electricity to generate heat and store it inside their core, often made from heavy clay blocks.Electric thermal storage heaters are stand-alone, off-peak heating systems that store heat in specially designed, high-density ceramic bricks for extended periods. [pdf]
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