Heat storage in smallest volume
Thermochemical heat storage can achieve low cost because of its higher specific energy density as compared with conventional heat storage materials. However, the thermal conductivity of the material is limited. Therefore, scientists at the Fraunhofer UMSICHT developed new thermochemical storage materials. The researchers intend to increase the thermal conductivity of solids, specifically through the addition of special additives.
|Project status||Project completed|
|Temperatur type||low temperature|
|Storage time||short (hours to days)|
|Number of cycles||General proof by execution of 20 cycles|
|Charging temperature||Depending on the material 150-300 °C|
|Discharge temperature||Depending on the material 100-250 °C|
|Storage capacity||This depends on the heat accumulator size|
|Energy storage density||up to 1.000 kJ/m³|
|Project duration||August 2012 until January 2016|
Thermochemical heat materials utilize the reaction enthalpy of chemical reactions for energy storage. Therefore specific volumetric heat densities of such materials can significantly exceed values of conventional heat storage materials. Typically solid storage materials do have low material costs, but the low heat conductivity of the materials limits the performance of the heat accumulators.
The overall goal of the project is therefore to develop new thermochemical heat storage materials, in which the heat conductivity is enhanced by the addition of selected components. The practical applicability of the materials will be assessed by mathematic modelling.
Store heat between 150 and 300 degrees Celsius
The project aims at the development of new heat storage materials with high volumetric heat storage capacities for a temperature range between 150 and 300 °C. Adding specific components to the material shall enhance the heat input into the material, which enables a fast charging and decharging of the heat accumluator. The process of heat accumulation in geometries relevant to practice will be determined by mathematical modelling. Moreover resulting primary energy savings for possible applications are estimated.
Within the project new thermochemical heat storage materials with optimized heat conductivity properties shall be developed. For this different reversible organic reaction systems will be tested regarding their applicability by identification of their reaction enthalpy and kinetics. Promising reaction systems will be developed further by enhancing their heat conductivity through adding specific components and a scale-up of the synthesis. Additionally a mathematical modelling of the heat storage processes will be executed.
Determine primary energy for different applications
In the first phase the project the research work concentrates on the identification of suitable organic reaction schemes, which are characterized in regard to reaction enthalpy and reaction kinetics. Simultaneously their applicability as a thermochemical heat storage material is assessed in principle. The second project phase, which will start nearly 1,5 years after project start, aims at the enhancement of the heat conductivity of promosing reaction systems by adding specific components. Special emphasis will be given to anisotropic material properties and a possible material scale-up. The completition of this work is planned after 2,5 years project duration. In parallel work on a third topic will start about 1,5 years project duration concentrating on the possible application of the material. Supported by mathematic modelling, promising concepts for the heat storage and release of the new material will be elaborated and the resulting primary energy savings will be estimated.
The new thermochemical heat storage materials shall rest upon a thermoreversible organic reaction system, which can be executed either as a Polymeraufbaureaktion or as a polymer analogous reaction. The aim is to reach specific energy densities per volume, which are higher than in conventional heat storage materials. As a consequence the heat accumulator size can be reduced and the investments costs can be decreaces. Additionally the heat input shall be enhanced, which will lead to higher charging and decharging loads.