Thermal energy storage (TES) is achieved with widely differing technologies. Depending on the specific technology, it is possible to increase the temperature of the energy supply, and to increase the energy consumption of the building, multiuser-building, district, town, or region. Use examples are the balancing of energy demand between daytime and nighttime, seasonal heating for winter heating, or seasonal winter heat storage. Storage media include water or ice-slush tanks, masses of native earth or bedrock with heat exchangers by means of boreholes, deep aquifers contained between impermeable strata; shallow, lined pits filled with gravel and water and insulated at the top, as well as eutectic solutions and phase-change materials. Other sources of thermal energy for storage include heat or cold production with heat pumps from off-peak, a cost called peak shaving; heat of combined heat and power (CHP) power plants; heat produced by renewable electrical energy that exceeds grid demand and waste heat from industrial processes. Heat storage, are considered to be important sources of energy, and they are considered to be highly profitable. heat produced by renewable electrical energy that exceeds grid demand and waste heat from industrial processes. Heat storage, are considered to be important sources of energy, and they are considered to be highly profitable. heat produced by renewable electrical energy that exceeds grid demand and waste heat from industrial processes. Heat storage, are considered to be important sources of energy, and they are considered to be highly profitable.

Most practical active solar heating systems provide storage from a few hours to a day’s worth of energy collected. However, there is a growing number of seasonal energy storage facilities (STES), which is used for winter storage. The Drake Landing Solar Community in Alberta, Canada, has now achieved a year-round 97% solar heating fraction, a world record made possible only by incorporating STES. The use of heat and heat is also possible with high temperature solar thermal input. Various eutectic mixtures of metals, such as Aluminum and Silicon (AlSi12) offer a high melting point for efficient steam generation, while high alumina cement-based materials offer good thermal storage capabilities.

Sensible heat of molten salt is also used for storing solar energy at a high temperature. Molten salts can be used as a thermal energy storage method to retain thermal energy. Presently, this is a commercially used technology to store the heat collected by concentrated solar power (eg, from a solar tower or solar trough). The heat can be steamed into the power of steam turbines and generate electricity in bad weather or at night. It was demonstrated in the Solar Two project from 1995-1999. Estimates in 2006 predicted an annual efficiency of 99%, with reference to the energy saved by storing heat before turning it into electricity, versus converting heat directly into electricity. Various eutectic mixtures of different salts are used (eg, sodium nitrate, potassium nitrate and calcium nitrate). Experience with such systems exists in non-solar applications in the chemical and metals industries as a heat-transport fluid. The salt melts at. It is kept in an insulated “cold” storage tank. The liquid salt is pumped through solar collectors where the focused sun heats it to. It is then sent to a hot storage tank. With proper insulation of the tank the thermal energy can be usedfully stored for up to a week. When electricity is needed, the hot molten-salt is pumped to a conventional steam-generator to produce superheated steam for driving a conventional turbine / generator set as used in any coal or oil or nuclear power plant. A 100-megawatt turbine would have a tank of this type. Single tank with hot and cold molten salt is under development. It is more economical by achieving 100% more heat storage in the body of the body than in the body of the body. It is also used in molten-salt energy storage (PCMs). Several parabolic trough power plants SolarReserve uses this thermal energy storage concept. The Solana Generating Station in the US can store 6 hours worth of generating capacity in molten salt. During the summer of 2013 the Gemasolar Thermosolar solar power-tower / molten-salt plant in Spain achieved 24 hours a day for 36 days. It is more economical by achieving 100% more heat storage in the body of the body than in the body of the body. It is also used in molten-salt energy storage (PCMs). Several parabolic trough power plants SolarReserve uses this thermal energy storage concept. The Solana Generating Station in the US can store 6 hours worth of generating capacity in molten salt. During the summer of 2013 the Gemasolar Thermosolar solar power-tower / molten-salt plant in Spain achieved 24 hours a day for 36 days. It is more economical by achieving 100% more heat storage in the body of the body than in the body of the body. It is also used in molten-salt energy storage (PCMs). Several parabolic trough power plants SolarReserve uses this thermal energy storage concept. The Solana Generating Station in the US can store 6 hours worth of generating capacity in molten salt. During the summer of 2013 the Gemasolar Thermosolar solar power-tower / molten-salt plant in Spain achieved 24 hours a day for 36 days. Several parabolic trough power plants SolarReserve uses this thermal energy storage concept. The Solana Generating Station in the US can store 6 hours worth of generating capacity in molten salt. During the summer of 2013 the Gemasolar Thermosolar solar power-tower / molten-salt plant in Spain achieved 24 hours a day for 36 days. Several parabolic trough power plants SolarReserve uses this thermal energy storage concept. The Solana Generating Station in the US can store 6 hours worth of generating capacity in molten salt. During the summer of 2013 the Gemasolar Thermosolar solar power-tower / molten-salt plant in Spain achieved 24 hours a day for 36 days.

A steam accumulator consists of an insulated steel pressure tank containing hot water and steam under pressure. As a heat storage device, it is used to generate heat by a variable or steady source from a variable demand for heat. Steam accumulators can be used for solar thermal energy projects. Large blinds are widely used in Scandinavia to store heat for several days, to meet the demand for heat and power. Interseasonal storage in caverns has been investigated and appears to be economical.

Heat capacity – 4.2 J / (cm³ · K). On the other hand, it can be heated to a much higher temperature. Thus, in the example below, an insulated cube of about 2.8m would appear to provide sufficient storage for a single house to meet 50% of heating demand. This could, in principle, be used to store surplus wind or heat to the ability of electrical heating to reach high temperatures. At the neighborhood level, the Wiggenhausen-Süd solar development at Friedrichshafen has received international attention. This features has 12,000 m³ (420,000 cu ft) of 4,000 m² (46,000 sq ft) of solar collectors, which will supply the 570 houses with around 50% of their heating and hot water. Siemens builds at 36 MWh thermal storage near Hamburg with 600 ° C basalt and 1.5 MW electric output. A similar system is scheduled for Sørø, Denmark, with 41-58% of the stored 18 MWh heat returned for the town heating district, and 30-41% returned as electricity.

Miscibility gap alloys de la phase de change de la metallic material (see: latent heat). Rather than pumping the liquid metal between tanks in a molten-salt system, the metal is encapsulated in another metallic material that it can not alloy with (immiscible). Depending on the two materials selected, the storage densities can be between 0.2 and 2 MJ / L. A working fluid, typically water or steam, is used to transfer heat and out of the MGA. Thermal conductivity of MGAs is often higher (up to 400 W / m K) than competing technologies which means quicker “charge” and “discharge” of thermal storage is possible. The technology has not yet been implemented on a large scale.

Storage heaters are commonplace in European homes with time-of-use metering. They consist of high-density ceramic bricks or heat-treated blocks with high temperature and electrical heat.

Several applications are being made during off-peak periods and used for cooling at later time. For example, air conditioning can be provided more economically by using low-cost electricity at the expense of water, then using the cooling capacity. Thermal energy storage using ice makes use of the large heat of fusion of water. Historically, ice is transported from mountains to cities for use as a coolant. One metric ton of water can store 334 million joules (MJ) or 317,000 BTUs (93kWh). A relatively small storage facility can hold up a large building for a day or a week. In addition to using direct cooling applications, it is also used in heat pump based heating systems. In these applications the phase changes energy can be used in a very large scale. This allows the system to increase the temperature and load the timeframe by which the source energy elements can contribute heat back into the system.

This uses as an energy store. A pilot cryogenic energy system that uses liquid air as the energy store, and low-grade waste heat to drive the thermal re-expansion of the air, has been operating at a power station in Slough, UK since 2010.

Solid or molten silicon offers much higher storage temperatures than those with greater capacity and efficiency. It is being researched as a possible more efficient energy storage technology. Silicon is able to store more than 1MWh of energy per cubic meter at 1400 ° C.

In pumped-heat electricity storage (PHES), a reversible heat-pump system is used to store energy at a temperature difference between two heat stores.

The company Isentropic operates as follows. It includes two insulated containers filled with crushed rock or gravel; a hot vessel storing thermal energy at high temperature and high pressure, and a cold vessel storing thermal energy at low temperature and low pressure. The vessels are connected to the bottom of the pipe and the entire system is filled with inert gas argon. During the charging cycle the system uses a power pump. Argon at room temperature and pressure is compressed to a pressure of 12 bar, heating it to around. The compressed gas is transferred to the top of the room where it flows through the gravel, transferring its heat to the rock and cooling to ambient temperature. The cooled, but still pressurized, gas is then expanded (again adiabatically) back down to 1 bar, which lowers its temperature to -150 ° C. The cold gas is then passed through the cold vessel where it cools the rock while being warmed back to its initial condition. The energy is recovered by reversing the cycle. The hot gas is hot and cold. The cooled gas retrieved from the bottom of the cold store is heats the temperature. The gas is then transferred to the bottom of the hot vessel to be reheated. The compression and expansion processes are provided by a specially designed reciprocating machine using sliding valves. Surplus heat generated by inefficiencies in the process of heat exchangers during the exhaust cycle. The developer claims that a round trip efficiency of 72-80% is achievable. This compares to> 80% achievable with pumped hydro energy storage. Another proposed system uses turbomachinery and is capable of operating at much higher power levels. Use of Phase Change Material (PCMs) would enhance the performance further.

One example of an experimental storage system based on chemical reaction is the salt hydrate technology. The system is used when hydrated or dehydrated. Containing 50% sodium hydroxide (NaOH) solution. Heat (eg, using a solar collector) is stored by an endothermic reaction. When water is added again, heat is released in an exothermic reaction at 50 ° C (120 ° F). Current systems operate at 60% efficiency. The system is especially advantageous for the storage of thermal energy, because it can be stored at room temperature for prolonged times, without energy loss. The containers with the dehydrated salt can be transported to a different location. The system has a higher energy density than the stored energy and the capacity of the system can be designed to store energy from a few months to years. In 2013 the Dutch technology developer TNO presented the results of the MERITS project to store heat in a salt container. The heat, which can be derived from a solar collector on a rooftop, expels the water contained in the salt. When the water is added again, the heat is released, with almost no energy losses. A container with a few cubic meters of salt could store this thermochemical energy to heat a house throughout the winter. In GJ / winter, an average low-energy rate of 6.7 GJ / winter. To store this energy in water (at a temperature difference of 70 ° C), 23 m 3 insulated water storage would be needed, beyond the storage abilities of most households. Using salt hydrate technology with a storage density of about 1 GJ / m 3, 4-8 m 3 could be sufficient. MERITS project Compact Heat Storage. <! original quote: “An average low-energy household has an energy demand of about 6.7 GJ / year. (For comparison: An average 4 person household in Germany uses on average rather 67 GJ / year.) For the storage of this energy of 6.7GJ in water (? T = 70 K) a volume of 23 m 3 GJ / m 3 (depending on operating salt hydrates, a storage volume of 4 – 8 m 3 would ideally be sufficient. The energy density of the thermochemical material will determine the volume of the storage system, the cost and the storage capacity. Especially for the long term, compact thermal storage is of utmost importance. In 2050, over 70% of the current dwellings will still be present! This means that the existing houses today will have to be retrofitted with thermal storage facilities in 2050. “-> As of 2016, or salt mixture.

Storing energy in molecular bonds is being investigated. Energy densities equivalent to lithium ion batteries have been achieved.