©
Natural gas generated naturally underground for seasonal storage
Following the first ‘Underground Sun Storage’ project, which demonstrated the production and storage of hydrogen from or wind energy (power-to-gas technology), further findings emerged during the course of the research that could be utilized in the ‘Underground Sun Conversion’ project. Together with a proportion of CO₂, part of the injected hydrogen was converted at a depth of over 1,000 metres, with the help of naturally occurring microorganisms, into renewable natural gas, which was then stored directly in this natural gas reservoir. When required, it was extracted and transported via the existing pipeline networks.
A further aim of the project was to assess the transferability of the results obtained to many other storage sites worldwide. The field trial was successfully completed by 2021.
©
„USC-FlexStore" - Follow-up project with an international partnership: storing renewable energy seasonally on a large scale and making it available all year round
This international and innovative follow-up project was carried out with Swiss partners under the leadership of Energie 360° and aimed to provide a seasonal, large-scale conversion and storage solution for volatile renewable energy sources. The project involved implementing further cycles and drilling a second well into the reservoir. The investigations focused on exploring the possibilities of injecting hydrogen and CO₂ via one injection probe and withdrawing them at different times via a second probe. The permeability of the rock and the behavior in underground storage facilities at depths of over 1,000 meters yielded very valuable insights. Another aim of the project was to further develop the ‘Underground Sun Conversion’ (USC) technology (methanation of CO₂ and green H₂) patented by RAG Austria AG and to design services based on this technology.
Advantages
Renewable natural gas is CO₂-neutral when used, as the same amount of CO₂ is sequestered beforehand during the production process. This creates a sustainable carbon cycle.
Electricity generation from solar and wind power is subject to weather-related and seasonal fluctuations. Demand-driven production is therefore not possible. The problem of storing large volumes of renewable energy is solved by converting it into natural, renewable natural gas.
Existing infrastructure was utilized for the natural production process, for underground storage in natural gas reservoirs, and for environmentally friendly transport to the end consumer.
Production of renewable natural gas using microorganisms
At a depth of over 1,000 meters – where natural natural gas was formed millions of years ago – the production of renewable natural gas using microorganisms was investigated. The aim of the research project initiated by RAG was to produce renewable natural gas through a CO₂-sequestration process. This involved both the methanation process and storage in underground porous reservoirs.
The technology’s great potential lies in providing the flexibility – which has been lacking until now but is urgently needed – in managing renewable energies and CO₂. The method replicated the natural formation process of natural gas. Having successfully achieved this conversion in the laboratory in just a few days and weeks, it was important to replicate the natural production of natural gas in a shortened timeframe directly within the reservoir.