Abstract
Lithium hydroxide monohydrate based thermochemical heat storage materials were modified with in situ formed 3D-nickel-carbon nanotubes (Ni-CNTs). The nanoscale (5–15 nm) LiOH·H2O particles were well dispersed in the composite formed with Ni-CNTs. These composite materials exhibited improved heat storage capacity, thermal conductivity, and hydration rate owing to hydrogen bonding between H2O and hydrophilic groups on the surface of Ni-CNTs, as concluded from combined results of in situ DRIFT spectroscopy and heat storage performance test. The introduction of 3D-carbon nanomaterials leads to a considerable decrease in the activation energy for the thermochemical reaction process. This phenomenon is probably due to Ni-CNTs providing an efficient hydrophilic reaction interface and exhibiting a surface effect on the hydration reaction. Among the thermochemical materials, Ni-CNTs–LiOH·H2O-1 showed the lowest activation energy (23.3 kJ mol−1), the highest thermal conductivity (3.78 W m−1 K−1) and the highest heat storage density (3935 kJ kg−1), which is 5.9 times higher than that of pure lithium hydroxide after the same hydration time. The heat storage density and the thermal conductivity of Ni-CNTs–LiOH·H2O are much higher than 1D MWCNTs and 2D graphene oxide modified LiOH·H2O. The selection of 3D carbon nanoadditives that formed part of the chemical heat storage materials is a very efficient way to enhance comprehensive performance of heat storage activity components.
Highlights
As an important part of clean and efficient utilization of alternative energy, the development of thermal energy storage technology has become increasingly important in recent years owing to the incremental consumption of fossil energy and the emission of greenhouse gases.[1,2] These technologies are divided into three main types: sensible heat storage,[3,4] latent heat storage,[5,6] and thermochemical heat storage.[7,8] All of these technologies participate in solving the supply and demand mismatch of thermal energy, and improve energy efficiency.[9]
It could be clearly seen that the diffraction peaks of LiOH$H2O were sharp and strong in the LiOH$H2O sample, but the diffraction peaks of LiOH$H2O became weaker and more diffused when 3D carbon nanomaterial nickel-carbon nanotubes (Ni-CNTs) were added
The composites of NiCNTs and LiOH$H2O were successfully synthesized, and the addition of Ni-CNTs resulted in the extensive dispersion of LiOH$H2O particles in the composite materials
Summary
As an important part of clean and efficient utilization of alternative energy, the development of thermal energy storage technology has become increasingly important in recent years owing to the incremental consumption of fossil energy and the emission of greenhouse gases.[1,2] These technologies are divided into three main types: sensible heat storage,[3,4] latent heat storage,[5,6] and thermochemical heat storage.[7,8] All of these technologies participate in solving the supply and demand mismatch of thermal energy, and improve energy efficiency.[9]. To simultaneously improve the performance of heat storage density, hydration rate, and thermal conductivity, we synthesized a novel TCM composite of in situ formed 3D-nickelcarbon nanotubes (Ni-CNTs) and LiOH$H2O.
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