An official website of the United States government
Thermochemical energy storage is promising for building applications as it offers high energy density and near-lossless storage. For example, inorganic salt hydrates that undergo reversible solid-gas thermochemical reactions can be used for thermal load shifting and/or shedding in buildings. However, this technology is still in early stages of development and drawbacks need to be addressed to make such a thermal battery viable. As salt hydrates differ in their morphology, crystal and/or particle size, and hygrothermal stability, it is critical to characterize thermochemical reactions accurately under specific operating conditions. Not only is the amount of heat delivered important, but so is the rate at which this heat is extracted for thermal end-use in buildings. However, the latter is not well reported in the literature, which is largely focused on energy storage rather than power density during the hydration reaction (battery discharge). To address this gap and the lack of standardized measurement methods, this work lays out a systematic simultaneous thermal analysis (STA) method for characterizing five different salt hydrate thermochemical materials (TCM). The effects of particle size, temperature and vapor pressure are analyzed to obtain the energy storage density and thermal power density across a full hydration-dehydration cycle under controlled conditions.
more »
« less
Carbon Foam/CaCl 2 ·6H 2 O Composite as a Phase-Change Material for Thermal Energy Storage
Inorganic salt hydrates are promising phase-change materials (PCMs) for thermal energy storage due to their high latent heat of fusion. However, their practical application is often limited by their unstable form, dehydration, large supercooling, and low thermal conductivity. Porous melamine foam and its carbonized derivatives are potential supporting porous materials to encapsulate inorganic salt hydrate PCMs to address these problems. This work investigates the effect of pyrolysis temperature on the morphology and structure of the carbonized foams and their thermal energy storage performance. Pyrolysis of melamine foam at 700−900 °C leads to the formation of crystalline sodium cyanate and sodium carbonate particles on the foam skeleton surface, which allows the spontaneous impregnation of the carbon foam with molten CaCl2·6H2O.The form-stable foam-CaCl2·6H2O composite effectively suppresses supercooling and dehydration, demonstrating the efficacy of carbon foam as a promising supporting material for inorganic salt hydrate PCMs.
more »
« less
- Award ID(s):
- 1846157
- PAR ID:
- 10508066
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- Energy & Fuels
- Volume:
- 37
- Issue:
- 16
- ISSN:
- 0887-0624
- Page Range / eLocation ID:
- 12381 to 12390
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Inorganic salt hydrates are promising materials for thermochemical energy storage as they undergo reversible solid-gas chemical reactions with water vapor to yield high energy densities with negligible self-discharge. However, material-level challenges such as structural and hygrothermal instabilities during the dehydration (charging) and hydration (discharging) reaction have limited their practical application in the buildings sector. The objective of this study is to address these irreversibilities in SrCl2 and MgCl2 by establishing a fabrication procedure that minimizes vapor diffusion resistance and lowers kinetic barriers for nucleation via particle size reduction. Furthermore, the distinct phase behavior of these two salts is leveraged to demonstrate a new binary salt mixture. Characterization of these materials was done using simultaneous thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) with a humidity generator. The results demonstrate that ball milling to particle sizes <50 μm yields a structurally stable material with improved hydration kinetics, while a 50/50 mass ratio of the binary mixture extends the range of conditions for the hydration reaction. Importantly, the salt mixture achieves a high specific energy density of 1100 J g-1 and peak thermal power output of 1.4 W g-1 under conditions at which the individual salts either deliquesce (MgCl2) or do not fully/rapidly hydrate (SrCl2). This work provides a procedure for the standardized fabrication and rational design of thermochemical salt mixtures with complementary phase behavior.more » « less
-
Nanofluids are defined as stable colloidal suspensions of nanoparticles within solvents. Over the past thirty years, they have emerged as promising candidates for various energy applications due to their unique material properties, which often exhibit anomalous behaviors, such as enhanced thermal energy storage (TES). The thermophysical properties and transport phenomena of nanofluids, including unusual mass transfer characteristics, can be complex and differ significantly from those of the base solvents. The envisioned applications of nanofluids are diverse and include their use as cooling agents in automobiles and manufacturing plants; as heat transfer fluids (HTFs) in heat exchangers for conventional thermal power plants, nuclear power plants, and renewable energy systems like concentrated solar power (CSP) plants; as materials for enhanced thermal energy storage, either in the form of sensible heat stored in molten salt nanofluids or latent heat in phase change materials (PCMs); as surfactants for cleaning purposes; as agents for mitigating radiation; and as corrosion inhibitors. This study investigates the corrosion performance of nanofluids when applied to metallic and alloy substrates for potential applications. Electrochemical experiments were conducted to assess the corrosion response and extent in aluminum and scratched brass. To evaluate the feasibility of adding nanoparticles to coolants, aluminum and brass surfaces were exposed to 0.01 M NaCl water solutions doped with silica nanoparticles at concentrations of 0.05% and 0.1% by mass, along with sodium dodecyl benzene sulfonate (SDBS) at 0.1% by mass. The results showed that the relative corrosion performance of the nanofluids is highly sensitive to the material nature of the tested substrates. Both brass and aluminum demonstrated improved corrosion resistance upon the introduction of silica SDBS additives into the fluid.more » « less
-
It is urgently desired yet challenging to synthesize porous graphitic carbon (PGC) in a bottom-up manner while circumventing the need for high-temperature pyrolysis. Here we present an effective and scalable strategy to synthesize PGC through acid-mediated aldol triple condensation followed by low-temperature graphitization. The deliberate structural design enables its graphitization in situ in solution and at low pyrolysis temperature. The resulting material features ultramicroporosity characterized by a sharp pore size distribution. In addition, the pristine homogeneous composition of the reaction mixture allows for solution-processability of the material for further characterization and applications. Thin films of this PGC exhibit several orders of magnitude higher electrical conductivity compared to analogous control materials that are carbonized at the same temperatures. The integration of low-temperature graphitization and solution-processability not only allows for an energy-efficient method for the production and fabrication of PGC, but also paves the way for its wider employment in applications such as electrocatalysis, sensing, and energy storage.more » « less
-
Nucleation of clathrate hydrates at low temperatures is constrained by very long induction (wait) times, which can range from hours to days. Electronucleation (application of an electrical potential difference across the hydrate forming solution) can significantly reduce the induction time. This work studies the use of porous open-cell foams of various materials as electronucleation electrodes. Experiments with tetrahydrofuran (THF) hydrates reveal that aluminum and carbon foam electrodes can enable voltage-dependent nucleation, with induction times dependent on the ionization tendency of the foam material. Furthermore, we observe a non-trivial dependence of the electronucleation parameters such as induction time and the recalescence temperature on the water:THF molar ratio. This study further corroborates previously developed hypotheses which associated rapid hydrate nucleation with the formation of metal-ion coordination compounds. Overall, this work studies various aspects of electronucleation with aluminum and carbon foams.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.energyfuels.3c01275
