Linking geological and infrastructural requirements for large-scale underground hydrogen storage in Germany

Abstract

Hydrogen storage might be key to the success of the hydrogen economy, and hence the energy transition in Germany. One option for cost-effective storage of large quantities of hydrogen is the geological subsurface. However, previous experience with underground hydrogen storage is restricted to salt caverns, which are limited in size and space. In contrast, pore storage facilities in aquifers -and/or depleted hydrocarbon reservoirs- could play a vital role in meeting base load needs due to their wide availability and large storage capacity, but experiences are limited to past operations with hydrogen-bearing town gas. To overcome this barrier, here we investigate hydrogen storage in porous storage systems in a two-step process: 1) First, we investigate positive and cautionary indicators for safe operations of hydrogen storage in pore storage systems. 2) Second, we estimate hydrogen storage capacities of pore storage systems in (current and decommissioned) underground natural gas storage systems and saline aquifers. Our systematic review highlights that optimal storage conditions in terms of energy content and hydrogen quality are found in sandstone reservoirs in absence of carbonate and iron bearing accessory minerals at a depth of approx. 1,100 m and a temperature of at least 40°C. Porosity and permeability of the reservoir formation should be at least 20% and 5 × 10−13 m2 (∼500 mD), respectively. In addition, the pH of the brine should fall below 6 and the salinity should exceed 100 mg/L. Based on these estimates, the total hydrogen storage capacity in underground natural gas storages is estimated to be up to 8 billion cubic meters or (0.72 Mt at STP) corresponding to 29 TWh of energy equivalent of hydrogen. Saline aquifers may offer additional storage capacities of 81.6–691.8 Mt of hydrogen, which amounts to 3.2 to 27.3 PWh of energy equivalent of hydrogen, the majority of which is located in the North German basin. Pore storage systems could therefore become a crucial element of the future German hydrogen infrastructure, especially in regions with large industrial hydrogen (storage) demand and likely hydrogen imports via pipelines and ships.

Underground Gas Storage in Saline Aquifers: Geological Aspects

“…Experience from CO 2 storage has been used in hydrogen storage capacity assessments, which in porous rock have been made using static or dynamic methods. Static assessments are based on determining the volume of pore space that can be filled with stored hydrogen [15]. Static capacity can be assessed on a regional scale or for individual geological structures, e.g., [124].…”

“…Salt caverns, depleted gas fields, and aquifers are considered as potential sites for underground hydrogen storage (UHS) [13][14][15][16]. However, the previous experience with underground hydrogen storage on an industrial scale is limited to salt caverns [17][18][19].…”

“…Positive and negative UGSs, CCS, and UHS indicators for underground gas storage in aquifers and depleted gas deposits[15,40,91,103,105].…”

Hydrogen Storage in Deep Saline Aquifers: Non-Recoverable Cushion Gas after Storage

“…Preparation of underground storage for the cyclic operation. Simulations of hydrogen injection into deep saline aquifers show that the cushion gas can effectively displace the water present in formation from injection and withdrawal wells, creating conditions for the subsequent injection and withdrawal of hydrogen [60,61]. In relation to the numerical simulation of seasonal hydrogen storage in an anticline aquifer, Chai et al [62] indicate that multiple cycles of hydrogen storage in an aquifer are helpful.…”

Future bioenergy source by microalgae–bacteria consortia: a circular economy approach

“…Geological storage is one of the cost-effective options in which biohydrogen is restricted to salt caverns. 101 A company that stores biohydrogen using such a technique is Mitsubishi Power, where the salt caverns are constructed deep underground with a diameter of 67 m and a height of 580 m. 102 In the case of storing in pressurized containers, biohydrogen has to be compressed or liquefied or can be both compressed and liquefied (to achieve a significant reduction in hydrogen volume after compression). However, the storage cost for storing in containers is high due to the complex process, in which the gas has to be cooled to −253 °C and maintained at such a low temperature for liquefied biohydrogen.…”