Thermochemical heat storage materials: Performance of mixed salt hydrates
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In: Solar Energy, Vol. 136, 15.10.2016, p. 571-589.
Research output: Journal contributions › Journal articles › Research › peer-review
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TY - JOUR
T1 - Thermochemical heat storage materials
T2 - Performance of mixed salt hydrates
AU - Rammelberg, Holger U.
AU - Osterland, Thomas
AU - Priehs, Boris
AU - Opel, Oliver
AU - Ruck, Wolfgang K.L.
PY - 2016/10/15
Y1 - 2016/10/15
N2 - Thermochemical heat storage is highly promising, in particularly with a view to long-term heat storage. For the implementation of heat storage in households, thermochemical reactions in the low temperature range below 120 °C are important. Especially salt hydrates such as MgCl 2, CaCl 2 or MgSO 4 were tested with micro gravimetric methods for their suitability. However, the cycle stability of consecutive charging (dehydration) and discharging (hydration) reactions of these materials was low and could be improved only by control of the water uptake (i.e. discharging time) to prevent overhydration. In contrast, mixtures of these salt hydrates showed significant improvements in cycle stability, mass and enthalpy balances. The experiments also showed that the cycleability of all investigated materials increased if hydration and dehydration reactions were performed under constant vapor pressure of 21 mbar. Contrary to other materials, the mixture of CaCl 2 and MgCl 2 showed good cycleability under all tested conditions. In addition, the mixture showed superior kinetic properties. Additionally, there is evidence of tachyhydrite (CaMg 2Cl 6⋅12H 2O) formation during cycling of the mixture by the use of XRD after the thermal analysis. Further investigations will be performed to identify further synergies, ideal mixing ratios and formed phases.
AB - Thermochemical heat storage is highly promising, in particularly with a view to long-term heat storage. For the implementation of heat storage in households, thermochemical reactions in the low temperature range below 120 °C are important. Especially salt hydrates such as MgCl 2, CaCl 2 or MgSO 4 were tested with micro gravimetric methods for their suitability. However, the cycle stability of consecutive charging (dehydration) and discharging (hydration) reactions of these materials was low and could be improved only by control of the water uptake (i.e. discharging time) to prevent overhydration. In contrast, mixtures of these salt hydrates showed significant improvements in cycle stability, mass and enthalpy balances. The experiments also showed that the cycleability of all investigated materials increased if hydration and dehydration reactions were performed under constant vapor pressure of 21 mbar. Contrary to other materials, the mixture of CaCl 2 and MgCl 2 showed good cycleability under all tested conditions. In addition, the mixture showed superior kinetic properties. Additionally, there is evidence of tachyhydrite (CaMg 2Cl 6⋅12H 2O) formation during cycling of the mixture by the use of XRD after the thermal analysis. Further investigations will be performed to identify further synergies, ideal mixing ratios and formed phases.
KW - Sustainability Science
KW - Chemistry
KW - Cycling stability
KW - Salt hydrate
KW - Thermal analysis
KW - Thermochemical energy storage
UR - http://www.scopus.com/inward/record.url?scp=84994744832&partnerID=8YFLogxK
UR - https://www.mendeley.com/catalogue/9b06d164-25f9-3eda-b981-244cd408dd04/
U2 - 10.1016/j.solener.2016.07.016
DO - 10.1016/j.solener.2016.07.016
M3 - Journal articles
VL - 136
SP - 571
EP - 589
JO - Solar Energy
JF - Solar Energy
SN - 0038-092X
ER -