Potential Storage Capacity Research Articles

Idealized Shale Sorption Isotherm Measurements To Determine Pore Capacity, Pore Size Distribution, and Surface Area

One potential method for mitigating the impacts of anthropogenic CO2-related climate change is the sequestration of CO2 in depleted geological gas and oil formations, including shale. The accurate characterization of the heterogeneous material properties of shale, including pore capacity, surface area, pore-size distributions, and composition is needed to understand the potential storage capacities of shale formations. Powdered idealized shale samples were created to explore reduction of the complications in characterization of pore capacity that arise from the heterogeneous rock composition and pore sizes ranging over multiple orders of magnitude. The idealized shales were created by mechanically mixing incremental amounts of four essential powdered components by weight and characterized with low pressure gas adsorption/desorption isotherms. The first two components, organic carbon and phyllosilicates (such as clays, micas, and chlorite), have been shown to be the most important components for CO2 uptake...

Evaluation of Practicable Subsurface CO2 Storage Capacity and Potential CO2 Transportation Networks, Onshore North America

Carbon Capture, Utilization and Storage (CCUS) is considered to be a potentially important technology for reducing the amount of carbon dioxide (CO2) released into the atmosphere from anthropogenic emission sources. With recent progress on capture technologies, attention is increasingly turning to the identification of key challenges associated with CO2 transportation and storage at the scale being considered for the CCUS industry. Decades of oil and gas production have provided experience in application of technologies required for CO2 transportation and storage, but the challenges unique to CO2 storage still need to be evaluated. This paper describes a scoping-level assessment of practicable subsurface geologic CO2 storage capacity and a potential Carbon Capture, Utilization, and Storage (CCUS) industry in the US and Canada, leveraging publically available data/information, publications, and methodologies. Likely subsurface CO2 storage sites and distribution of storage capacity relative to major anthropogenic sources are first characterized using a probabilistic methodology previously developed by the US Geologic Survey (USGS), which was modified to account for several practical factors affecting storage capacity. Major factors considered include 1) subsurface lateral accessibility restrictions imposed by faulting and/or stratigraphic pinch-outs, 2) the proportion of net storage-quality sand comprised of thin sands unlikely to be good injection candidates, 3) surface access restrictions, and 4) dynamic injectivity/storage efficiency considerations. Potential regional CCUS networks are then modeled using a transportation cost framework to map CO2 sources to storage sinks. The USGS assessment and most other existing assessments of storage capacity are based on the premise that all engineering approaches and hardware required to achieve the highest possible storage efficiency would be employed, and that injection rate and timeframe are not issues, with perhaps hundreds to thousands of years of injection permitted to achieve full storage efficiency. We explore the impact of dynamic injectivity considerations on practical storage efficiency by using reservoir simulation models to account for subsurface pressure limitations and the impact of permeability differences and lateral accessibility on CO2 injectability, and then use the results of the modeling to derive a debiting function that reduces the range of static storage capacity estimated by the USGS. Debiting functions accounting for lateral accessibility, thin sands, and surface access restrictions were also applied to obtain practicable storage estimates. Key conclusions from the study include: 1) Although the modified storage capacity estimates are lower than previously published estimates, the estimated subsurface storage capacity in the US onshore is sufficient to sustain a large-scale CO2 storage industry. We estimate that about 500 Gt of potential US subsurface storage capacity is potentially available (excluding federal offshore capacity) even after accounting for dynamic injectibility considerations, thin sands, surface and lateral access issues. Dynamic injectability factors had the largest impact on the reduction in estimated storage capacity. 2) Significant geographic misalignment exists between current high-volume CO2 emission sources and storage availability in North America. This could affect evolution of CO2 transportation networks with time. Detailed site-specific assessments of subsurface storage capacity are required for site selection and actual project implementation. These efforts could change some of the conclusions of this study. In particular, consideration of legacy wells and geomechanical factors such as induced seismicity, ground surface deformation, and fault activation may further reduce storage capacity relative to the estimates presented here. Nevertheless, the methodology described in this paper may be useful for initial assessment of CO2 storage capacity and matching of CO2 emission sources to storage sinks in geographic locations other than those considered in this study.

Coupling Effects of Supercritical CO2 Sequestration in Deep Coal Seam

CO2 sequestration in deep unminable coal seams is currently identified as a research hot spot to reduce CO2 emissions, due to the potential large-scale storage capacity and complicated physical and chemical reactions, especially for supercritical CO2 (scCO2). Hitherto, the interaction mechanisms between scCO2 and coal mass in situ conditions are still unclear. Therefore, the main objective of this study is to fully address the coupling effects of scCO2 sequestration on coal mass and provide a comprehensive evaluation of the interrelation of these variations. Five cycles of helium and scCO2 injection were replicated on a subbituminous coal sample to investigate the permeability variation with scCO2 saturation time. Meanwhile, gas chromatography–mass spectrometry (GC–MS), gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), proximate analysis, and low-pressure–temperature nitrogen (N2) isotherm analyses were employed to characterize the transformation in coal mass. The test result shows ...

Model predictive control of a hybrid heat pump system and impact of the prediction horizon on cost-saving potential and optimal storage capacity

The present paper analyses the cost-optimal sizing and hourly control strategy of a hybrid heat pump system for heating application, composed by an electrically-driven air source heat pump and a gas boiler. These hybrid systems represent a promising solution for the energy retrofit of existing buildings and new installations, being able to increase the efficiency of monovalent systems, especially at low external temperatures. The use of thermal storage can furtherly minimize both the operating cost and the primary energy consumption, shifting the operation of the heat pump to the most profitable periods. In this work, the optimal control problem has been investigated by means of mixed-integer linear programming, considering an ideal forecast of external temperature and thermal load on given horizon periods (i.e. model predictive control). Achievable cost savings with respect to a traditional rule-based control strategy with no storage are presented as a function of both prediction horizon and storage capacity in a dimensionless form. A relation between prediction horizon length and optimal storage capacity is shown. An example of application of the method is illustrated, showing cost savings up to 8%. A sensitivity analysis on the storage tank losses, climatic conditions, generators efficiency, and energy prices is also presented, showing the cost saving potential in all these different conditions.

Performing Carbon Storage Resource Assessments for Offshore Mid-Atlantic United States

The Mid-Atlantic United States Offshore Carbon Storage Resource Assessment Project (FE0026087) is part of the U.S. Department of Energy National Energy Technology Laboratory’s Carbon Storage program to improve the effectiveness and reduce the costs of carbon dioxide storage implementation. This paper presents the methods followed and preliminary results of a comprehensive examination of potential carbon storage resources for an area of the offshore not previously characterized for carbon storage. The paper discusses the deep saline formations’ geologic and hydrologic properties informed by core, well log, and seismic data, followed by a discussion of risk factors that may affect storage resource potential. The results suggest the presence of laterally continuous sandstone formations and seals that offer significant potential storage capacity.

Exploring the influence of vegetation cover, sediment storage capacity and channel dimensions on stone check dam conditions and effectiveness in a large regulated river in México

Check dams are widely used for soil conservation at the watershed scale. When structurally sound, these engineering control works retain sediment as planned. However, there is limited information describing the influence of site characteristics on post-construction condition including structural stability and sediment retention capacity. More specifically, the effects of channel morphology, check dam geometry and vegetation characteristics as potentially influencing factors on sediment retention capacity at the watershed level are poorly understood. Thus, an investigation applying field and remotely sensed measurements, multi-regression models, redundancy and sensitivity analysis, and correlation analysis was conducted in a Mexican watershed where the characteristics of 273 check dams were evaluated 3–5 years after construction. Vegetation cover and dimensions of the channel were found to be the most important factors influencing check dam fate. Taller structures experienced the greatest failure risk, in contrast to lower and wider structures and associated vegetation cover that retained long and wide sediment wedges, which helped to stabilise the check dams. The potential sediment storage capacity of the check dams mainly depends on the downstream height of the structure, but also on the vegetation cover near the structure walls; check dams constructed across a range of channel dimensions are able to effectively store sediment. Overall, this study provides a quantitative evaluation of the dominant factors influencing the post-construction conditions of check dams and their ability to store sediment, and thus provides land managers insights into the best strategies for soil conservation at the watershed scale using check dams.

Coastal Karst Groundwater in the Mediterranean: A Resource to Be Preferably Exploited Onshore, Not from Karst Submarine Springs

Coastal karst aquifers are common in the Mediterranean basin. With their significant potential storage capacity, they are an attractive groundwater resource in areas where the water demand is the most important. They discharge either at the coastal zone or directly into the sea at karst submarine springs (KSMS). Decision makers take an interest in this unconventional groundwater resource and are convinced by companies and research consultancies that KSMS’s should be exploited because they would discharge huge amount of fresh water. Being now well documented, the occurrence of KSMS’s along the Mediterranean coast is discussed in the light of recent geological history favourable to the development of karst. Conduit flow conditions are common, inherited from an intense phase of karstification during the Messinian Crisis of Salinity at the end of Miocene, when the sea level was 1500 to 2500 m below present sea level. From investigations carried out along the coasts of France and the Levant, compared with studies done along other Mediterranean coastlines, it appears that capturing groundwater discharged at KSMS raises different problems which make the operation dicey and expansive.

Petrographic and Petrophysical Characterization of Detrital Reservoir Rocks for CO2 Geological Storage (Utrillas and Escucha Sandstones, Northern Spain)

The aim of this article is to provide a qualitative and quantitative description of Lower–Upper Cretaceous detrital rocks (Escucha and Utrillas sandstones) in order to explore their potential use as CO2 reservoirs based on their petrographic and petrophysical characteristics. Optical microscopy (OpM) and scanning electron microscopy (SEM) aided by optical image analysis (OIA) were used to get qualitative and quantitative information about mineralogy, texture and pore network structure. Complementary analyses by X-ray fluorescence (XRF) and X-ray diffraction (XRD) were performed to refine the mineralogical information and to obtain whole rock geochemical data. Furthermore, mercury injection capillary pressure analysis (MICP), the gas permeameter test (GPT) and the hydraulic test (HT) were applied to assess the potential storage capacity and the facility of fluid flow through the rocks. Both of these factors have an outstanding importance in the determination of CO2 reservoir potential. The applied petrophysical and petrographic methods allowed an exhaustive characterization of the samples and a preliminary assessment of their potential as a CO2 reservoir. The studied conglomerates and sandstones have a porosity range of 8–26% with a dominant pore size range of 80–500 μm. The grain skeleton consists of quartz (95%), very minor potassium feldspars (orthoclase) and a small amount of mica (muscovite and chlorite). According to these preliminary results, among the studied varieties, the Escucha sandstones have the most favorable properties for CO2 geological storage at the rock matrix scale.

Dynamic monitoring the infrastructure of major ports in Sri Lanka by using multi-temporal high spatial resolution remote sensing images

Colombo port and Hambantota port in Sri Lanka play a key role in transiting and supporting the shipping trade of “the 21st-Century Maritime Silk Road”. In recent years, Chinese enterprises have made huge investments in the infrastructure construction of Colombo port and Hambantota port. The construction progress and development trend of Colombo port and Hambantota port have been attracting the attention of Chinese investment enterprises and the society. In this paper, multi-temporal high spatial resolution remote sensing images are used to monitor the infrastructure construction condition of Colombo port and Hambantota port from 2010 to 2017. According to the interpreted infrastructure information of the two ports, the international container terminal of Colombo and Hambantota port have completed their constructions. By the end of 2017, the international container terminal of Colombo built the container yards with 28.8 ha and roads with 32.6 ha. At the south of the international container terminal of Colombo, the 62.2 ha of reclamation area were built for the planned port city. In Hambantota port, 77 ha of container yards, 48 ha of roads and 2.9 ha of oil storage areas were constructed during this period. Meanwhile, the analysis of potential storage capacity of Colombo port and Hambantota port shows that the throughput of Colombo port may increase by 3 million tons per year while the throughput of Hambantota port will be over its designed 2.5 million tons per year. These analysis results are able to provide a useful reference for Chinese investment enterprises and the related research of “the Belt and Road”.

Onset of density-driven instabilities in fractured aquifers.

Linear stability analysis is conducted to study the onset of density-driven convection involved in solubility trapping of CO_{2} in fractured aquifers. The effect of physical properties of a fracture network on the stability of a diffusive boundary layer in a saturated fractured porous media is investigated using the dual porosity concept. Linear stability analysis results show that both fracture interporosity flow and fracture storativity play an important role in the stability behavior of the system. It is shown that a diffusive boundary layer under the gravity field in fractured porous media with lower fracture storativity and/or higher fracture interporosity flow coefficient is more stable. We present scaling relations for the onset of convective instability in fractured aquifers with single and variable matrix block size distribution. These findings improve our understanding of density-driven flow in fractured aquifers and are important in the estimation of potential storage capacity, risk assessment, and storage site characterization and screening.

Planning for variable renewable energy and electric vehicle integration under varying degrees of decentralization: A case study in Lusaka, Zambia

High urbanization rates, decentralized solar photovoltaic growth, and transportation electrification are changing the electricity planning landscape across Sub-Saharan Africa. This paper explores the operational implications of variable renewable energy and electric vehicle integration at the city scale. A production cost dispatch model is applied to Lusaka, Zambia's capital, whose largely hydro-based electricity system is currently facing shortfalls due to population and economic growth and climate change. The results demonstrate that variable renewable energy penetration and decentralization are important levers for managing greenhouse gas emissions, while the choice of electric vehicle charging policy has significant cost implications. Due to Zambia's flexible hydro assets and potential pumped hydro storage capacity, large penetrations of centralized solar photovoltaic energy can be integrated with low curtailment rates, regardless of electric vehicle charging policy. The high curtailment rates (>10%) and increased greenhouse gas emissions associated with non-export solar PV penetrations greater than 35% can be mitigated with flexible loads, such as electric vehicle charging, that is strategically shifted to coincide with high-resource periods of the day. Without active electric vehicle charging management, large peaking capacity is required to satisfy demand spikes. Conversely, system-optimized vehicle-to-grid charging eliminates the need for additional storage infrastructure thereby mitigating system costs.

Silica–Ceria sandwiched Ni core–shell catalyst for low temperature dry reforming of biogas: Coke resistance and mechanistic insights

In this paper, a novel sandwiched core–shell structured Ni-SiO2@CeO2 catalyst, with nickel nanoparticles encapsulated between silica and ceria, was developed and applied for dry reforming of biogas (CH4 / CO2 = 3/2) under low temperature conditions to test its coke inhibition properties. Ni-phyllosilicate was used as the Ni precursor in order to produce highly dispersed Ni nanoparticles on SiO2. Cerium oxide was chosen as the shell due to its high redox potential and oxygen storage capacity, that can reduce coke formation under severe dry reforming conditions. The core shell Ni-SiO2@CeO2 catalyst showed excellent coke inhibition property under low temperature (600 °C) reforming of biogas, with no coke detected after a 72 h catalytic run. Under the same conditions, Ni-SiO2 catalyst deactivated within 22 h due to heavy coke formation and reactor blockage, while Ni-CeO2 catalyst showed very low activity. The higher activity of the core–shell catalyst is attributed to its higher Ni dispersion and reducibility. TEM and XRD results show that the core–shell catalyst shows higher resistance to Ni particle sintering and agglomeration during the reaction than the Ni-SiO2 and Ni-CeO2 catalysts. In-situ DRIFTS on the Ni-SiO2@CeO2 catalyst indicate a change in the reaction mechanism from a mono-functional pathway on the Ni-SiO2 catalysts to a bi-functional route on the Ni-SiO2@CeO2 catalyst with active participation of oxygen species from CeO2 in carbon gasification. The confinement effect of the sandwich structure and the bifunctional mechanism of dry reforming are the primary reasons for the excellent coke resistance of the Ni-SiO2@CeO2 catalyst.

Estimating restorable wetland water storage at landscape scales.

Globally, hydrologic modifications such as ditching and subsurface drainage have significantly reduced wetland water storage capacity (i.e., volume of surface water a wetland can retain) and consequent wetland functions. While wetland area has been well documented across many landscapes and used to guide restoration efforts, few studies have directly quantified the associated wetland storage capacity. Here, we present a novel raster-based approach to quantify both contemporary and potential (i.e., restorable) storage capacities of individual depressional basins across landscapes. We demonstrate the utility of this method by applying it to the Delmarva Peninsula, a region punctuated by both depressional wetlands and drainage ditches. Across the entire peninsula, we estimated that restoration (i.e., plugging ditches) could increase storage capacity by 80%. Focusing on an individual watershed, we found that over 59% of restorable storage capacity occurs within 20 m of the drainage network, and that 93% occurs within 1 m elevation of the drainage network. Our demonstration highlights widespread ditching in this landscape, spatial patterns of both contemporary and potential storage capacities, and clear opportunities for hydrologic restoration. In Delmarva and more broadly, our novel approach can inform targeted landscape-scale conservation and restoration efforts to optimize hydrologically mediated wetland functions.

Impacts of integrated nutrient management on methane emission, global warming potential and carbon storage capacity in rice grown in a northeast India soil.

Rice soil is a source of emission of two major greenhouse gases (methane (CH4) and nitrous oxide (N2O)) and a sink of carbon dioxide (CO2). The effect of inorganic fertilizers in combination with various organics (cow dung, green manure (Sesbania aculeata) Azolla compost, rice husk) on CH4 emission, global warming potential, and soil carbon storage along with crop productivity were studied at university farm under field conditions. The experiment was conducted in a randomized block design for 2years in a monsoon rice (cv. Ranjit) ecosystem (June-November, 2014 and 2015). Combined application of inorganic (NPK) with Sesbania aculeata resulted in high global warming potential (GWP) of 887.4kg CO2 ha-1 and low GWP of 540.6kg CO2 ha-1 was recordedfrom inorganic fertilizer applied field. Irrespective of the type of organic amendments, flag leaf photosynthesis of the rice crop increased over NPK application (control). There was an increase in CH4 emission from the organic amended fields compared to NPK alone. The combined application of NPK and Azolla compost was effective in the buildup of soil carbon (16.93gkg-1) and capacity of soil carbon storage (28.1Mg C ha-1) with high carbon efficiency ratio (16.9). Azolla compost application along with NPK recorded 15.66% higher CH4 emission with 27.43% yield increment over control. Azolla compost application significantly enhanced carbon storage of soil and improved the yielding ability of grain (6.55Mgha-1) over other treatments.

Nitrogen doping of TiO2 nanosheets greatly enhances bioelectricity generation of S. loihica PV-4

The performance of TiO2 nanosheets (TiO2-NSs) modified carbon paper anode (TiO2-NSs/CP) in S. loihica PV-4 inoculated MFCs is greatly improved by intentional N doping of TiO2-NSs to modulate its electronic properties. TiO2-NSs/CP is calcined in NH3 atmosphere at different temperatures (T = 400, 500, 600 and 700 °C) to obtain N doped anodes (T-NTiO2-NSs/CP, T represents temperature), in which 600-NTiO2-NSs/CP electrode show best performance with the maximum output power density increased by 196% and 50% compared to that from the bare CP and TiO2-NSs/CP electrodes respectively. The surface morphology, structure and electrochemical activity are characterized by FESEM, XRD, Raman, XPS, CVs and EIS. The results show that heating in NH3 atmosphere keep surface morphology and bio-affinity of the electrode. The midpoint potential Em (−0.29 V) of outer membrane c-type cytochromes (OMCs) at 600-NTiO2-NSs/CP anode is in accordance with that at TiO2-NSs/CP. However, 600-NTiO2-NSs/CP electrode had smaller charge transfer resistance, more positive flat-band potential and larger transient charge storage capacity than untreated electrode due to modulation of the electronic structure via N doping, which all are favorable to interfacial electron transfer from OMCs to underlying electrode. The method is simply and efficient, and could be extended to other nano-semiconductor modified electrodes for superior MFC anodes.

Application case study of enhanced coal bed methane recovery process in thar coal fields

Enhanced coal bed methane recovery (ECBM) process is an important developing technology because of its dual advantage, i.e., producing methane gas and sequestering CO2 at the same time. CO2 have been used for enhanced oil recovery (EOR) for more than five decades but available storage sites for EOR are only limited to oil rich countries. Pakistan has one of the largest coal reserves in the world accounting to more than 185 billion tons. In this study, CO2 sequestration in the coalbeds of Thar coal field located in the South of Pakistan is explored from the technical and economical point of view. Potential CO2 storage capacity and methane gas‐in‐place has been calculated for the Thar coal fields. Next, an economic analysis has been performed to evaluate the cost of CO2 storage and to explore any economic benefit from the methane production. Usually, coal reservoirs are saturated with water, hence water production along with methane is inevitable. This study analyzed various water treatment methods and recommended shallow re‐injection technology to be the most suitable for the Thar coal ECBM process. In addition, carbon balance has been investigated to calculate the CO2 avoided during the ECBM process. Finally, a sensitivity analysis has been performed on some of the important design variables in order to analyze their effect on the cost of CO2 storage. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 900–911, 2018

Options for CO2 Sequestration in Kuwait

In preparation for future requirements to abate CO2 emission levels, a CO2 storage feasibility study was carried out for the country of Kuwait. At present, no definite plans exist to install capture facilities at the larger emission points in the country; the study presented is one of the first steps to prepare the country for a low-carbon future. The first step was to investigate formations for potential CO2 storage capacity in a country-wide screening. Two regions within Kuwait were shortlisted for subsequent evaluation; one site was selected for detailed characterization and assessment. The main result of the study was that the Kra Al-Maru Trend is likely to be a first-class CO2 storage site. Pending verification of the findings we conclude that the Kra Al-Maru Trend provides the storage capacity of at least 440 Mt, which is equivalent to the CO2 produced in a period of 40 years by the Doha East and Doha West power plants combined. The subsurface of the Kra Al-Maru Trend can store this CO2 at the rate that is currently emitted to the atmosphere by the two power plants. No showstoppers were discovered to safe and secure storage of CO2. Storing CO2 in the subsurface of the Kra Al-Maru Trend offers the possibility of future back-production of the CO2 stored. Verification of these conclusions is required, through a dedicated appraisal well that targets the Cretaceous interval at depths between about 2000 m and 3000 m (6000 - 9000ft).

Effects of short-term invasion of Spartina alterniflora and the subsequent restoration of native mangroves on the soil organic carbon, nitrogen and phosphorus stock

The exotic cordgrass Spartina alterniflora has severely invaded the mangrove wetlands in southern China and ecological restoration using native mangroves was conducted in an attempt to control this invasive species. In this study, the contents and pools of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) were quantified to investigate the invasive effects of S. alterniflora and then to evaluate whether the ecological restoration of native mangrove could reverse those effects. S. alterniflora only showed significantly higher organic carbon content in the surface 0–10 cm of soil than in the uninvaded mudflat. The high δ13C values in the surface soil of the invaded habitat demonstrated that S. alterniflora contributed 42.6–62.2% of the organic carbon. The SOC for invasive S. alterniflora and newly restored mangroves (4 years and 14 years) was not enhanced in comparison to the unvegetated mudflat. S. alterniflora significantly increased the surface soil TN content, but decreased the available phosphorus content and TP density. The TN densities increased gradually with the mangrove restoration, while the TP densities were only slightly influenced. The results suggested that short-term invasion of S. alterniflora and subsequent mangrove restoration did not alter SOC or TN pool sizes, but S. alterniflora was shown to affect the potential carbon storage capacity produced by the mangroves in the Zhangjiang Estuary.

Potential capacity of gas storage caverns in rock salt bedded deposits in Poland

The subject of this article is an estimation of the initial capacity of a gas storage cavern, depending on the thickness and the depth of a bedded salt deposit, and the cavern's capacity decrease in time due to its convergence. It was assumed that the relative rate of convergence depends on the depth, the range of the storage pressure and the cavern diameter to height ratio. The discussion will consider the shape of the cavern and the pressure range of natural gas storage. Also, potential locations in Poland for natural gas storage in bedded rock salt deposits in terms of geological and mining criteria are presented in this article. Based on Zechstein isopach maps, as well as maps of its top depth, potential storage capacity maps per unit area were developed. Presented examples will cover two potential regions i.e., bedded salt deposit in the Zatoka Gdańska region and Fore-Sudetic Monocline. These maps will be the basis for the analysis of the suitability of the bedded rock salt Zechstein deposit for natural gas storage.

Thermochemical Storage of Middle Temperature Wasted Heat by Functionalized C/Mg(OH)2 Hybrid Materials

For the thermochemical performance implementation of Mg(OH)2 as a heat storage medium, several hybrid materials have been investigated. For this study, high-performance hybrid materials have been developed by exploiting the authors’ previous findings. Expanded graphite (EG)/carbon nanotubes (CNTs)-Mg(OH)2 hybrid materials have been prepared through Mg(OH)2 deposition-precipitation over functionalized, i.e., oxidized, or un-functionalized EG or CNTs. The heat storage performances of the carbon-based hybrid materials have been investigated through a laboratory-scale experimental simulation of the heat storage/release cycles, carried out by a thermogravimetric apparatus. This study offers a critical evaluation of the thermochemical performances of developed materials through their comparison in terms of heat storage and output capacities per mass and volume unit. It was demonstrated that both EG and CNTs improves the thermochemical performances of the storage medium in terms of reaction rate and conversion with respect to pure Mg(OH)2. With functionalized EG/CNTs-Mg(OH)2, (i) the potential heat storage and output capacities per mass unit of Mg(OH)2 have been completely exploited; and (ii) higher heat storage and output capacities per volume unit were obtained. That means, for technological applications, as smaller volume at equal stored/released heat.