Underground Sun Conversion

Renewable gas produced to store solar and wind power

ENGLISH Unique research project

Underground conversion and storage of wind and solar energy

For years, RAG has been dealing with the In our unique „Underground Sun Storage“ decarbonisation and transformation of energy flagship project, we have been working with systems. At the same time, with the increasing partners to test the storage of hydrogen in RAG Austria AG is expansion of energy from renewable sources, the depleted natural gas reservoirs as part of an Austria’s largest demand for large-volume and seasonal storage in-situ field trial. In the framework of this project, gas storage will increase, compensating for the seasonal we were able to gain many positive insights that company – fluctuations in energy harvest (summer sun) motivated us to continue. A key finding led to the making it the and energy demand (winter) and providing the current project „Underground Sun Conversion“, country’s biggest usual level of security which will be presented in more energy storage of supply. It is a service “The energy carrier gas can be detail in this brochure. provider – and that cannot be provided transported in large quantities Hydrogen and carbon dioxide one of Europe’s by pump storage plants safely and invisibly in existing can be converted into me­thane leading gas or batteries. Gas storage underground infrastructure and = renewable natural gas in can provide the solution. suitable natural gas reservoirs storage facility environmentally friendly stored in operators. RAG Austria AG has through a microbiological natural gas reservoirs. Due to its therefore been making process. This energy conver- good geological preconditions considerable efforts in sion as well as the increase in research and develop- for storage, Austria can make a energy density and energy ment for years to evolve significant contribution to Europe‘s storage take place invisibly in storage solutions for security of supply.“ the porous rock at depths of structuring the supply of more than 1,000 metres. renewable energy as required. We see ourselves Under the leadership of RAG Austria AG, the as a partner of renewable energies. An already Underground Sun Conversion project is being widely discussed solution for the storage carried out by an Austrian consortium and problem is the „power-to-gas“ technology. The supported as part of the energy research surplus electricity from solar and wind energy program of the Austrian Climate and Energy splits water into oxygen and hydrogen. Fund as a flagship project. The research Electricity (electrons) is then converted into project should be completed by 2021. hydrogen (storable molecules). Thus hydrogen becomes an energy carrier.

2 / UNDERGROUND SUN CONVERSION RENEWABLE GAS PRODUCED TO STORE SOLAR AND WIND POWER / 3 Sustainable Carbon Cycle

Project description Renewable natural gas Electricity Elektrolysis CO2 CH4

First, hydrogen is produced from solar or wind power Initial laboratory tests conducted as part of the fore­ H2 Water utilization and water, in an above-ground facility, and then injected runner project, Underground Sun Storage – which is also Energetic utilization with carbon dioxide into an existing (porous) natural gas supported by the Austrian Climate and Energy Fund – Electricity generated by solar reservoir. At a depth of over 1,000 metres, in a relatively show that hydrogen and carbon dioxide injected into the and wind power will be converted to hydrogen by electrolysis. short time naturally occurring microorganisms convert reservoir are converted into methane by microbiological these substances into renewable gas which can be processes. This enables the creation of a sustainable stored in the same reservoir, withdrawn as needed at carbon cycle. Laboratory tests, simulations and a ©BOKU any time, and transported to consumers via the existing scientific field test at an existing RAG reservoir will be pipeline network. carried out in collaboration with a group of project

The aim of the research project is to use existing gas partners. A further objective is to test whether the Micro-organisms convert injected (pore) reservoirs as natural bio-reactors. The methana- outcomes can also be achieved at many other reservoirs hydrogen (H2) and carbon dioxide (CO2) into renewable natural gas tion process and storage take place naturally in under- all over the world. The striven results are therefore (CH4) and water (H2O). ground pore reservoirs. This represents a huge source of outstanding importance for a successful energy by potentially providing the urgently needed flexibility transition. 4 H CO CH 2 H O which renewable energy sources currently lack. 2 2 4 2

Using existing natural gas reservoirs for conversion and storage of renewable energy Natural origin and current use of natural gas The formation of natural gas storage reservoir takes millions of years. In the 20th century, due to its flexibility and versatility, Geological history in fast motion: natural gas is establishing itself as one of the most important (fossil) sources of energy. Producing natural and renewable gas Underground Sun Conversion Technology makes it possible to have available large volumes of seasonally storable natural gas in a renewable energy system available. This unique method recreates the process by which natural gas originates, but shortens it by This environmentally friendly process millions of years – like geological history in fast motion. has three major advantages: The time advantage is primarily due to two factors. On impermeable High pressure layers the one hand, organic substance must first be built up % Carbon neutral in natural formation (in principle, solar energy should Renewable natural gas is carbon neutral if also be stored). These organic substances die off, are CO2 that is already present – for example, decomposed and converted to (methane) natural gas. from burning biomass – is utilised and absor- Reservoir This process is shortened in Underground Sun bed by the production process. This creates a Mud and silt Conversion technology by going straight into the process Digested sludge sustainable carbon cycle. with the starting materials of the last conversion step. Formation The formation Exploration and Underground Secondly, the use of fossil natural gas requires a % Renewable energy becomes storable of digested sludge of natural gas production Sun Conversion sedimentation process that produces porous storage Solar and wind power output fluctuates The sun provides energy Over the millennia, many layers of mud In the 20th century, the In the future, this process structures with a corresponding clayey covering layer. due to changing weather conditions, mea- for organic growth. Micro­ deposited over it. Under high pressure production of natural gas in the natural reservoir This process takes a long time and only then can gas be ning that production cannot be adjusted to organisms sink to the seabed and oxygen occlusion, microorganisms from these reservoirs will be copied and stored in the geological structures. At that time, much demand. The problem of storing renewable and are covered with sand converted the digested sludge. Natural gas begins. shortens it by millions methane was immediately returned to the carbon cycle, energy is solved by converting it into renewa- and silt. This produces was created and accumulated in deposits of years. Within a few ble natural gas. digested sludge. between impermeable layers. weeks, the Underground as is still the case in wetlands today. By using already Sun Conversion technology existing suitable reservoirs, no sedimentation process % Use of existing infrastructure will create „renewable has to be awaited, and the risk of developing suitable Infrastructure already in place can be used for natural gas“. stratigraphy is eliminated. the natural production process, as well as for In total, geological time periods can be skipped by using underground storage in natural gas reser- existing geological structures - hence „Geological history voirs, and environmentally friendly transpor- in fast motion“. tation to consumers. 250 million years 50 million years 1900 2017

4 / UNDERGROUND SUN CONVERSION RENEWABLE GAS PRODUCED TO STORE SOLAR AND WIND POWER / 5 Thematic areas

In order to map and answer the scientific questions in the best possible way, a work plan with nine work packages was created.

Work package 3:

Simulation of the microbiological process The aim of this work package is to use Work package 1: Work package 2: computer simulations to elucidate the Work package 4: Work package 5: global feedback mechanisms between microbial growth and the properties of Project management Microbial methanation in underground natural gas gas flow in storage and to identify Materials and corrosion Product gas conditioning optimal operating strategies for Among other things, the tasks of this reservoirs (sandstone formation) efficient methane production. This work package involves conducting This work package focuses on the work package are to maintain the Our primary goal in Underground Sun Conversion is to control microbial transformation Computer reconstructions of the gas laboratory and field tests to determine conditioning of the product gas from interfaces between the individual work processes in gas storages towards microbial conversion of hydrogen and carbon storage facility are combined with whether the gases hydrogen and the underground methanation. The packages, to organize public relations dioxide to methane (hydrogen trophic methanogenesis). Environmental conditions have mechanistic models of methane-pro­ carbon dioxide required for the unique main objective is the development of a and the dissemination of the results, to to be identified that favour microbiological methanation and suppress potential ducing microbes to understand the microbiological methanation process membrane system for the separation communicate with the funders and to adverse effects such as homoacetogenesis and pore clogging. Conversion processes interactions between the microorga­ will cause corrosion of the steel of hydrogen and carbon dioxide from report. will be established in laboratory experiments using specimen originating from the nisms, the gas flow and the environ­ grades used in the facility, and the withdrawn gas. Consequently, the underground gas storage and verified at field conditions as present at the test site. ment. The data obtained from the whether there is a possibility of produced gas is made compatible with Finally, an evaluation of the methane formation capacity with respect to industrial laboratory and the field trial are used changes occurring in the cementation natural gas infrastructure and can be exploitation will be accomplished. to validate these models. of the wells. injected in the gas grid.

Work package 6: Work package 7: Work package 8: Work package 9:

Planning, construction and operation – Planning, construction and operation – Technical ability for upscaling Potential assessment In-situ reservoir batch experiments In-situ reservoir circulation experiments This work package aims to develop process concepts for an This work package is lead by the Energieinstitut an der JKU. In the course of this work package, a scientific field test facility As a major extension to work package 6 a second well will be industrial plant size, particularly for the required surface The work is compiled in cooperation with RAG and the for the underground sun conversion process will be planned drilled in order to further develop the reservoir. This allows infrastructures. A reasonable plant capacity is derived related Montanuniversität Leoben. It focusses on the techno-economic and built. Using an existing well, the hydrogen – carbon dioxide cycling experiments in which conclusions can be drawn on the to suitable sites in a global view whereat the influences of and ecological evaluation of the Underground Sun Conversion – natural gas mixture is injected into the test reservoir at a kinetics of the conversion reaction by continuous observation specific locations framework conditions on the process technology considering it as a systemic building block of a depth of about 1,000 metres. After a conversion phase under of the gas composition and other parametres. With the help of concept are identified. Furthermore, the potential of combining „Power-to-Gas“ system. The work package starts with a shut-in conditions, the gas mixture is removed via the same this second well, the gas mixture can be moved and monitored geomethanation with surface catalytic post-methanation is potential and site location analysis in order to estimate the well. During the test procedure, analysis samples can be taken in circulation operation through the reservoir. Subsequently, assessed. The technical aspects of upscaling are provided for global potential for establishing Underground Sun Conversion. repeatedly and trends of pressure, temperature and gas the resulting methane production can be skimmed off using the potential analysis in WP9, including costs for main plant Additionally a legal analysis is carried out aiming at determining composition can be observed. membrane technology and new hydrogen and carbon dioxide items. the challenges and hurdles in the current legal system for can be added to the process. establishing Underground Sun Conversion.

6 / UNDERGROUND SUN CONVERSION RENEWABLE GAS PRODUCED TO STORE SOLAR AND WIND POWER / 7 01. Electrolysis In the Underground Sun Conversion project, the microbiological generation of renewable natural gas Schematic representation This is where hydrogen is generated from electric will be restarted, a process that took place exactly here current. After cleaning the well water through a reverse 02 of sun storage millions of years ago. osmosis system, the water is decomposed into hydro- gen and oxygen by direct current. The hydrogen is dried 06. Withdrawal well 08 and mixed with CO2 and natural gas forwarded to the 03 compressor. The oxygen is released as a by-product to The removal of renewable natural gas takes place the atmosphere. from the cycle operation via its own well, which is also 07 01 equipped with appropriate safety features.

04 The electrolysis of water consists of two partial reactions, 10 which take place at the two electrodes (cathode and anode 07. Drying unit chambers). In a subsurface reservoir gas is absorbing moisture. Cathode space: 2 H2O + 2 e- " H2 + 2 OH 09 Therefore, before the gas is discharged into the down­ 06 Anode space: 6 H2O " O2 + 4 H3O+ + 4 e- The overall reaction scheme of this redox reaction is: stream systems and the pipeline network, a drying is required. 2 H2O(l) Electrolysis 2 H2(g) + O2 (g)

Oxygen 08. Gas conditioning 0 m The gas taken from the reservoir may still contain residual Water unreacted hydrogen and carbon dioxide. In the course of

Cathode the project, a membrane separation process is therefore being tested in order to reduce these gas components to Anode a specification-compliant level. 06 Hydrogen

In this process an alkaline electrolysis is used. KOH is added 09. Electricity grid connection Pore space in the thin section to raise the conductivity of hydrogen, which improves the The Underground Sun Conversion Project is about storing efficiency factor. renewable electricity by converting it into a storable 500 m energy source. The renewable electricity is supplied via the power grid and transformed via a transformer to the required voltage levels. 02. CO2 - Tank

For microbiological methanation in the reservoir, CO2

is added to the process. CO2 is supplied in liquid form 10. Control unit / EMSR and stored in a buffer tank on site and can be added as At this point all information comes together, measure- needed. The CO2 comes from a biogenic source. ment data is processed and forwarded for evaluation. The system operates autonomously during normal 03. Compressor station operation and is monitored by the headquarters in Grain size of approx. 0.5 mm Natural gas reservoir / rock Gampern. In the event of any fault messages, the To bring the gas mixture methane / hydrogen / CO2 to on-call service reacts. the required pressure in order to to be able to bring it into the reservoir, a compressor is needed. Here is a so-called piston compressor machine used. A maximum 05 Reservoir accumulator pressure of 60 bar is planned. Max. pressure 107 bar 04. Injection well Temperature 40 °C The injection and withdrawal in batch operation take Depth 1,027 m 1.000 m place via a well, which is equipped with appropriate Working gas volume 1.7 mn cu m safety features. In later cycle operation, this well is Reservoir volume 6.2 mn cu m only used for storage.

Elektrolysis 01 Elektrolysis 05 Gas reservoir 09 Electricity grid connection 05. Gas reservoir Installed power 500 kW Millions of years ago, natural gas reservoirs were created 100 cu m H2/h 02 CO2 - tank 06 Withdrawal well 10 Control unit / EMSR in the pores of the sandstone, which are sealed by more than 100 m thick clay layers. Here, large quantities of 03 Compressor station 07 Drying unit energy can be stored sustainably, safely and invisibly.

Injection well Gas conditioning 04 08 RENEWABLE GAS PRODUCED TO STORE SOLAR AND WIND POWER / 9 Wind + Sun = Gas Households, Industry, Mobility, CNG

This is the equation behind power to gas, an innovative technology that forms the basis for the Underground Sun Storage and Underground Sun Conversion research projects.

Gas Power Plan / electricity. The answer is gas. Besides power Future technology with CHP Unit generation, it can also be used for heating, Power Grid enormous potential in vehicles and as a raw material. The gas transportation and storage infrastructure in Gas Grid place has all the makings of a storage system Intermittent renewable electricity output is not for green power. the only problem. Something will also have to This will make it be done with all the excess power generated Environmentally friendly possible to econo- by giant wind and solar parks at times when Solar Energy mically transport demand is low. This surplus energy needs power to gas technology Wind Power and store the to be stored so that it can be made available renewable solar during peak periods. If we want 100 percent and wind energy of the electricity generated in Austria to come The principle behind this new, environmentally in large quantities from renewable sources, we will need storage friendly technology could hardly be simpler. and thus to have with capacity over 100 times greater than the Surplus solar and wind power is used to split it available at all potential offered by pumped storage. (Source: water into oxygen and hydrogen by means of times. Vienna University of Technology, ESEA/EA electrolysis. The hydrogen can then be stored (ed.): ‘Super-4-Micro-Grid’, research project for later use, for example as primary energy final report, Vienna 2011). The combined in fuel cells. But a further step is also possible: capacity of pumped storage plants and battery in methanation, the hydrogen is reacted with

storage used to date is far from sufficient. carbon dioxide (CO2). Preferably, the CO2 co-

Additionally, such facilities can only release mes from CO2-rich gas streams (e.g. biogas or industrial plants). The product of the process is Today the efficiency of the conversion process is already Using existing natural gas renewable synthetic natural gas. about approx. 60 % – a big step forward in view of the fact that surplus electricity is often not used at all owing infrastructure to the lack of storage capacity, and instead wind turbines are idled or whole wind farms taken off the grid. If the hydrogen can be used directly, the efficiency rate is even Thanks to electrolysis and methanation, electricity can higher. be converted into hydrogen and into natural gas, making large-scale power storage possible for the first time. The process solves one of the biggest problems posed by electricity storage – shortage of space. It means we can simply turn to existing natural gas infrastructure, in the shape of the pipeline grid and large storage facilities. Instead of developing and rolling out expensive and elaborate new storage technologies, the power would be transformed into synthetic natural gas and stored in depleted gas reservoirs.

10 / UNDERGROUND SUN CONVERSION RENEWABLE GAS PRODUCED TO STORE SOLAR AND WIND POWER / 11 Energy storage Review:

Energy consumption in Austria / Central Europe is significantly higher in winter than in summer. Natural gas storage systems that are located near consumption provide the essential service of Underground Sun seasonal compensation in the energy system. Storage In simple terms, gas is stored in summer and removed in Another service in the energy system is provided by winter. The storage has an annual cycle, as can be seen pumped hydro storages and in future by the much from the graph below. This involves very large amounts smaller battery storage. These storage systems ensure Harvesting, storing and supplying solar energy: RAG tested this of energy – in the case of RAG Austria AG by up to a day-night balance and stability of the power grid in groundbreaking approach to energy production and storage in a unique 66 TWh. This service ensures that the energy supply is the electricity system. Therefore these storages are filled research project, Underground Sun Storage. provided at all times of the year and even during supply and emptied up to 365 times a year. In addition they interruptions (security of supply). The importance of are much smaller. The overall storage volume of the the seasonal balance between supply and demand will Austrian pumped hydro storages is only 0.14 TWh increase significantly in the future if we gradually switch (Source: Vienna University of Technology, ESEA / EA The main purpose of this pioneering project Results to solar and wind energy. (ed.): „Super 4 Micro Grid“, final report on the research was to investigate the hydrogen tolerance project, Vienna 2011), sufficient for this service but The storability of underground gas storage reservoirs. The of hydrogen project demonstrated that gas storage facilities unsuitable for the needs of seasonal storage. • Underground storage of renewable energy produced using can tolerate hydrogen content of up to 10 %. via hydrogen is possible solar energy was This means that naturally formed gas storage • Existing gas storage infrastructure has been demonstrated at reservoirs are not a limiting factor within the successfully tested for the applicability of a small depleted gas system as a whole, and with their vast hydrogen Energy storage during the year gas reservoir in storage capacity (more than 8 billion cubic Upper Austria/ metres in Austria, equivalent to 92 terawatt • There is no negative impact on the existing Pilsbach. hours), their role in the energy system of the storage Spring Summer Autumn Winter future could change significantly, since they • The integrity of porous gas storage is not can be used to store and balance supplies of compromised renewable energy. • No migration from the reservoir Based on these results further research at • No change in the storage rock many other storage formations can now be • Microbial processes can be controlled undertaken. • Sustainable use of the existing infrastructure for the renewable energy future Storage of regenerative • Synergies of storage and production of Seasonal storage hydrogen in porous gas renewable gas (gas storage) storage tanks • Positive response from national and inter­ 1 x seasonal balance national storage operators and stakeholders

• Electricity can not be stored, but hydrogen Future development can • Large amounts of solar and wind energy opportunities require seasonal and large-scale storage

• Sustainable use of the gas infrastructure is • Sun Conversion Project - Production and possible storage of renewable gas in an existing • Renewable energy becomes baseloadable underground infrastructure Daily storage • Test the storage capacity of up to 100 % (pump storage, batteries) hydrogen in the underground storage 365 x daily balance

12 / UNDERGROUND SUN CONVERSION RENEWABLE GAS PRODUCED TO STORE SOLAR AND WIND POWER / 13 Project partner

RAG Austria AG Montanuniversität Leoben Energieinstitut an der Johannes Kepler Universität Linz acib (Austrian Centre of Industrial Biotechnology) RAG is an innovative and traditional energy company The Montanuniversitaet Leoben (MU Leoben), established The Energy Institute at the JKU Linz is responsible for The Austrian Centre of Industrial Biotechnology (acib) focused on its core business of gas storage, developing in 1840, is unique in its high degree of specialization: the techno-economic, ecological and legal analyzes as is an international non-profit competence and research innovative and sustainable energy solutions using its the major research areas and degree programs are well as for the survey of the technology potential in the centre with more than 140 partners around the world. extensive underground expertise. In particular, the embedded in in the value chain from raw materials to project Underground Sun.Conversion: Through the acib’s research focus is in the field of industrial biotech- development of new energy technologies, through recycling: the portfolio ranges from extraction and techno-economic evaluation of the system, the process nology. acib adopts tools and methods of nature for research and production of renewable gas. With the mining to the processing of resources and basic materials, costs can be analyzed and predicted and compared with new production processes and products with improved operation of a storage capacity of now approx. 6 billion metallurgy, high-performance materials, process and relevant benchmarks ; this is a comprehensive analysis ecological efficiency and higher economic efficiency. cubic metres, RAG makes a significant contribution to product engineering, environmental technology and involving learning curves and economies of scale of the acib’s major fields of research are bioinformatics/ the security of supply in Austria and Central Europe, recycling, complemented by power engineering and system. In addition, national and international locations modeling, biocatalysis, systems and synthetic biology, making it one of the largest gas storage operators in production logistics. MU Leoben contributes as scientific for the potential implementation of the technology are process engineering, and cell biology. Europe. partner to this project with its expertise in material identified. Furthermore, Life Cycle Assessments (LCAs) The focus of the company is clearly on the promising science, particularly corrosion, as well as with process are used to investigate the environmental impact. and versatile energy carrier „gas“. The classic, natural technological aspects of the plant scale-up. Moreover, as explained above, screening and analysis gas, which will make an indispensable contribution to of the legal dimensions of the system are performed. the energy supply in the future, is only one aspect. The other is called „green gas“ - such as synthetic gas using power-to-gas technology. RAG is consortium leader and biggest investor within the flagship project „Under- ground Sun Conversion“. In addition to its many years of experience in the development, construction and commissioning of storage facilities, RAG brings with it the acquired expertise and insights from the project „Underground Sun Storage“. University of Natural Resources and Life Sciences Axiom GmbH ­ Vienna / Department of Agrobiotechnology, IFA Tulln / was founded in 1992 as a company specializing in Institute of Environmental Biotechnology industrial applications of membrane technology. The institute’s Geobiotechnology and Chemodynamics Besides employing reverse osmosis technology in water group (Andreas P. Loibner) adds biotechnological purification projects, Axiom carries out intensive research expertise to the project, offering comprehensive in gas permeation technology and has secured numerous experience in the scientific description of microbial patents. In a joint research cooperation with Vienna consortia and their metabolic capabilities. Research University of Technology’s Institute of Chemical comprises microbial subsurface processes, which are Engineering, Axiom developed new applications for then evaluated regarding their potential commercial use. membrane gas separation. These include the recovery As part of the Underground Sun Conversion project, of helium and hydrogen, the separation of carbon the group investigates techniques that allow for a control dioxide from natural gas and the biogas purification. of microbial processes in natural gas storage facilities Axiom has steadily extended this area of its expertise, with the focus being put on the microbial formation of and Has applied it with great commercial success, methane from hydrogen and carbon dioxide. Insights becoming a major supplier for the membrane gas gained from laboratory experiments (WP2) will feed into separation process and a leading innovator in the field. The project will receive funding from the Austrian implementation of the in-situ reservoir experiments Axiom sees membrane separation processes as one of Climate and Energy Fund established by the Ministry (WP6 and WP7). tomorrow’s key technologies. for Transport, Innovation and Technology, as part of its energy research programme.

14 / UNDERGROUND SUN CONVERSION RENEWABLE GAS PRODUCED TO STORE SOLAR AND WIND POWER / 15 Contact

Stephan Bauer Head of Green Gas Technology, Project manager [email protected] www.underground-sun-conversion.at

RAG Austria AG Schwarzenbergplatz 16 1015 Vienna, Austria [email protected] www.rag-austria.at

Legal information: Published by RAG Austria AG, Schwarzenbergplatz 16, 1015 Vienna Pictures: RAG archives, steve.haider.com, Karin Lohberger Photography, fotolia.de Last updated: September 2018