Inter-seasonal compressed-air energy storage using saline aquifers (original) (raw)
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Renewable energy storage in geological formations
Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2017
With the transition to renewable energies and, above all, strongly fluctuating electricity from wind and solar energy, there will be a need for energy storage in the future. For central grid-scale storages, underground geological storage, similar to those already used for fossil fuels, is in the first place under review. Compressed Air Energy Storages have already been successfully used to provide minutes to hours reserve. For storage capacities in the day to week range, storage is required on a chemical rather than a mechanical basis, through either the conversion of electricity into pure hydrogen (H2) or the generation of mixtures of natural gas and synthetic methane. The latter – the so-called power-to-gas option – allows the use of the existing gas infrastructure. A likely first choice for the storage of H2 or H2-SNG mixtures are man-made salt caverns. The suitability of porous rock storage (depleted hydrocarbon reservoirs or water-bearing reservoirs – aquifers) is still under i...
Environmental Earth Sciences, 2016
New techniques and methods for energy storage are required for the transition to a renewable power supply, termed ''Energiewende'' in Germany. Energy storage in the geological subsurface provides large potential capacities to bridge temporal gaps between periods of production of solar or wind power and consumer demand and may also help to relieve the power grids. Storage options include storage of synthetic methane, hydrogen or compressed air in salt caverns or porous formations as well as heat storage in porous formations. In the ANGUS? project, heat and gas storage in porous media and salt caverns and aspects of their use on subsurface spatial planning concepts are investigated. The optimal dimensioning of storage sites, the achievable charging and discharging rates and the effective storage capacity as well as the induced thermal, hydraulic, mechanical, geochemical and microbial effects are studied. The geological structures, the surface energy infrastructure and the governing processes are parameterized, using either literature data or own experimental studies. Numerical modeling tools are developed for the simulation of realistically defined synthetic storage scenarios. The feasible dimensioning of storage applications is assessed in sitespecific numerical scenario analyses, and the related spatial extents and time scales of induced effects connected with the respective storage application are quantified. Additionally, geophysical monitoring methods, which allow for a better spatial resolution of the storage operation, induced effects or leakages, are evaluated based on these scenario simulations. Methods for the assessment of such subsurface geological storage sites are thus developed, which account for the spatial extension of the subsurface operation itself as well as its induced effects and the spatial requirements of adequate monitoring methods.
Evaluation of the subsurface compressed air energy storage (CAES) potential on Gotland, Sweden
Environmental Earth Sciences
Wind energy is an important field of development for the island of Gotland, Sweden, especially since the island has set targets to generate 100% of its energy from renewable sources by 2025. Due to the variability of wind conditions, energy storage will be an important technology to facilitate the continued development of wind energy on Gotland and ensure a stable and secure supply of electricity. In this study, the feasibility of utilizing the Middle Cambrian Faludden sandstone reservoir on Gotland for Compressed Air Energy Storage (CAES) is assessed. Firstly, a characterization of the sandstone beneath Gotland is presented, which includes detailed maps of reservoir thickness and top reservoir structure. Analysis of this information shows that the properties of the Faludden sandstone and associated cap rock appear favorable for the application of CAES. Seven structural closures are identified below the eastern and southern parts of Gotland, which could potentially be utilized for CAES. Scoping estimates of the energy storage capacity and flow rate for these closures within the Faludden sandstone show that industrial scale CAES could be possible on Gotland.
Energy Conversion and Management, 2015
Economic, large-scale energy storage technology plays a key role in enabling the utility industry to integrate more renewable energy sources into the grid. Compressed air energy storage in porous geological formations has the potential to become one of the principal energy storage technologies in the future. Storing pressurized air in aquifers has several advantages, including large storage capacity, geologically widespread availability, relatively constant pressure, and relatively low construction cost. The performance of a compressed air energy storage plant is influenced by the subsurface reservoir properties. In this paper, the design criteria, calculation procedure, and exergy analysis approach to quantify the influence of aquifer permeability on compressed air energy storage plants are proposed. A case-study model was built to simulate a compressed air energy storage plant using aquifers with porosities of 30% and different permeabilities (0.01-1.0 darcies). The exergy destruction rates and exergy and thermal efficiencies were calculated. The results indicated that as the permeability increased, the exergy destruction due to a pressure drop of working fluid in an aquifer decreased; as the permeability increased, both thermal and exergy efficiencies increased, and the net output of the plant increased. The benefits are more obvious when the permeability increased from low (60.05 darcies) to medium-high values (P0.25 darcies).
Entropy
As the number of renewable energy sources connected to the grid has increased, the need to address the intermittency of these sources becomes essential. One solution to this problem is to install energy storage technologies on the grid to provide a buffer between supply and demand. One such energy storage technology is Compressed Air Energy Storage (CAES), which is suited to large-scale, long-term energy storage. Large scale CAES requires underground storage caverns, such as the salt caverns situated in the Cheshire Basin, UK. This study uses cavern data from the Cheshire Basin as a basis for performing an energy and exergy analysis of 10 simulated CAES systems to determine the exergy storage potential of the caverns in the Cheshire Basin and the associated work and power input and output. The analysis revealed that a full charge of all 10 caverns could store 25.32 GWh of exergy, which can be converted to 23.19 GWh of work, which requires 43.27 GWh of work to produce, giving a round...
Environmental Engineering Science
Compressed energy storage (CES) of air, CO 2 , or H 2 in porous formations is a promising means of energy storage to abate the intermittency of renewable energy production. During operation, gas is injected during times of excess energy production and extracted during excess demands to drive turbines. Storage in saline aquifers using CO 2 as a cushion or working gas has numerous advantages over typical air storage in caverns. However, interactions between CO 2 and saline aquifers may result in potential operational limitations and have not been considered. This work utilizes reactive transport simulations to evaluate the geochemical reactions that occur during injection and extraction operational cycles for CES in a porous formation using CO 2 as a cushion gas. Simulation results are compared with similar simulations considering an injection-only flow regime of geologic CO 2 storage. Once injected, CO 2 creates conditions favorable for dissolution of carbonate and aluminosilicate minerals. However, the dissolution extent is limited in the cyclic flow regime where significantly smaller dissolution occurs after the first cycle such that CO 2 is a viable choice of cushion gas. In the injection-only flow regime, larger extents of dissolution occur as the fluid continues to be undersaturated with respect to formation minerals throughout the study period and porosity increased uniformly from 24.84% to 33.6% throughout the simulation domain. For the cyclic flow conditions, porosity increases nonuniformly to 31.1% and 25.8% closest and furthest from the injection well, respectively.
Electrical energy storage using compressed gas in depleted hydraulically fractured wells
iScience, 2021
Renewable forms of electricity generation like solar and wind require low-cost energy storage solutions to meet climate change deployment goals. Here, we explore the use of depleted hydraulically fractured (''fracked'') oil and gas wells to store electrical energy in the form of compressed natural gas to be released to spin an expander/generator when electrical demand is high. Our reservoir model indicates that the same dual-porosity geological environment of fracked wells used to liberate hydrocarbons is also suitable for storing and releasing gas in a diurnal or seasonal cycle. Round-trip storage efficiency is calculated to be 40%-70% depending on the natural reservoir temperature. Levelized cost of storage is estimated to be $70-270/MWh, on par with pumped hydro storage. This study indicates that repurposed ''fracked'' wells could provide a muchneeded low-cost seasonal energy storage solution at the TWh scale.
Impacts of the use of the geological subsurface for energy storage: an investigation concept
Environmental Earth Sciences, 2013
New methods and technologies for energy storage are required to make a transition to renewable energy sources; in Germany this transition is termed ''Energiewende''. Subsurface georeservoirs, such as salt caverns for hydrogen, compressed air, and methane storage or porous formations for heat and gas storage, offer the possibility of hosting large amounts of energy. When employing these geological storage facilities, an adequate system and process understanding is essential in order to characterize and to predict the complex and interacting effects on other types of subsurface use and on protected entities. In order to make optimal use of georeservoirs, a comprehensive use planning of the subsurface is required that allocates specific uses to appropriate subsurface locations. This paper presents a generic methodology on how subsurface use planning can be conducted and how its scientific basis can be developed. Although synthetic, realistic scenarios for the use of the geological underground for energy storage are parameterized and numerically simulated, accounting for other kinds of subsurface use already in place. From these scenario analyses, the imposed coupled hydraulic, thermal, mechanical and chemical processes, as well as mutual effects and influences on protected entities are assessed and generalized. Based on these, a first methodology for large-scale planning of the geological subsurface considering different surface and subsurface usage scenarios may also be derived.