High temperature underground thermal energy storage system for solar energy

The activities feasibility of high temperature underground thermal storage of energy was investigated. Results indicate that salt cavern storage of hot oil is both technically and economically feasible as a method of storing huge quantities of heat at relatively low cost. One particular system identified utilizes a gravel filled cavern leached within a salt dome. Thermal losses are shown to be less than one percent of cyclically transferred heat. A system like this having a 40 MW sub t transfer rate capability and over eight hours of storage capacity is shown to cost about $13.50 per KWh sub t

Opportunities for large-scale energy storage in geological formations in mainland Portugal

This article presents the methodology and results of the first screening conducted in Portugal to identify geological formations suitable for large-scale storage of energy from renewable sources. The screening focused on the identification of adequate porous media rocks, salt formations and igneous host rocks that could act as reservoirs for gas (hydrogen or methane) storage, Compressed Air Energy Storage, Underground Pumped Hydro and Underground Thermal Energy Storage. Public access geological information was collected, compiled in a database and spatially referenced in a GIS environment. The GIS and database were cross-checked with criteria for selecting geological reservoirs and with existing or anticipated spatial, environmental and social constraints. In a third step the feasibility of deploying each large-scale energy storage technology in each prospective reservoir was assessed and classified according to confidence, ranging from unlikely to proven, and to proximity to areas with wind or solar energy potential, accessibility to power transmission lines and natural gas networks. The outcome is a first screening of priority sites to be studied at the local scale in future projects. Early target for detailed studies are the existing salt caverns and an abandoned salt mine in the Lusitanian Basin. Natural gas storage in salt formations is being carried in the region for decades, proving the adequacy of the salt formations and demonstrating the social acceptance. Porous media aquifers in the same Lusitanian basin may also hold an interesting potential, although there is considerable uncertainty due to the scarcity of geological data about deep aquifers. The Sines industrial cluster, in SW Portugal, is another interesting target area, due to the existence of a host rock with proven containment capacity. The technologies with the best potential for application in the Portuguese geologic context seem to be CAES and Underground Gas Storage linked to Power-to-gas projects

Rapid Depresurizations: Can they lead to irreversible damage?

International audienceRapid gas depressurization leads to gas cooling that is followed by slow gas warming when the cavern is kept idle. The decrease in the temperature of gas depends upon the relative withdrawal rate (in %/day), and cavern size and shape. Gas cooling may result in the onset of tensile stresses at cavern walls and roofs that may generate fractures or cracks. However, in most cases, the depth of penetration of these fractures is small, and they are perpendicular to the cavern wall. The distance between two parallel fractures becomes larger when fractures penetrate deeper into the rock mass, as some fractures stop growing. Fractures form a polygonal pattern. Salt slabs are created, with boundaries formed by the opened fractures. As long as the depth of penetration of the fracture remains small, these slabs remain strongly bonded to the rock mass, and it is believed that, in many cases, their weights are not large enough to allow them to break off the cavern wall

CREEP CLOSURE RATE OF A SHALLOW CAVERN

International audienceCavern creep closure rate was recorded in the SG13-SG14 salt cavern of the Gellenoncourt brine field operated by CSME at Gellenoncourt in Lorraine, France. Cavern compressibility and the evolution of cavern brine temperature first were measured. In this shallow cavern (250-m, or 800-ft, deep), which had been kept idle for 30 years, cavern-brine thermal expansion can be disregarded. To assess cavern closure rate, a 10-month brine-outflow test was performed, followed by a 6-month shut-in test. During the tests, brine outflow or pressure evolution is influenced by atmospheric pressure changes, ground temperature changes and Earth tides. From the average pressure-evolution rate, it can be inferred that the steady-state cavern closure rate is slower than 10-5/yr (0.001%/yr, or 3×10-13 /s.) A part of the material used to write this paper was already included in a paper presented during the Grand Junction SMRI Meeting. The update includes the analyses of atmospheric pressure effects, dynamic oscillations of the brine column, column temperature changes and brine crystallization

Simulations of neutron background in a time projection chamber relevant to dark matter searches

Presented here are results of simulations of neutron background performed for a time projection chamber acting as a particle dark matter detector in an underground laboratory. The investigated background includes neutrons from rock and detector components, generated via spontaneous fission and (alpha, n) reactions, as well as those due to cosmic-ray muons. Neutrons were propagated to the sensitive volume of the detector and the nuclear recoil spectra were calculated. Methods of neutron background suppression were also examined and limitations to the sensitivity of a gaseous dark matter detector are discussed. Results indicate that neutrons should not limit sensitivity to WIMP-nucleon interactions down to a level of (1 - 3) x 10^{-8} pb in a 10 kg detector.Comment: 27 pages (total, including 3 tables and 11 figures). Accepted for publication in Nuclear Instruments and Methods in Physics Research - Section

Some numerical methods for solving stochastic impulse control in natural gas storage facilities

The valuation of gas storage facilities is characterized as a stochastic impulse control problem with finite horizon resulting in Hamilton-Jacobi-Bellman (HJB) equations for the value function. In this context the two catagories of solving schemes for optimal switching are discussed in a stochastic control framework. We reviewed some numerical methods which include approaches related to partial differential equations (PDEs), Markov chain approximation, nonparametric regression, quantization method and some practitioners’ methods. This paper considers optimal switching problem arising in valuation of gas storage contracts for leasing the storage facilities, and investigates the recent developments as well as their advantages and disadvantages of each scheme based on dynamic programming principle (DPP

Conceptual design of thermal energy storage systems for near term electric utility applications. Volume 2: Appendices - screening of concepts

Volume 2 of this 2 volume report is represented. This volume contains three appendices: (1) bibliography and cross references; (2) taxonomy - proponents and sources; and (3) concept definitions