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Research and development

New technology

The future belongs to green gas. For some time now, RAG has been working hard on new approaches to making large amounts of renewable energy conveniently accessible for consumers. Wind + sun = green gas – this is the equation behind power-to-gas. Together with natural gas, this could be the key to the success of the energy transformation. It can make the transportation and storage of large amounts of solar and wind power economically viable. It can mean that climate friendly energy is always available whenever it is needed.

Together, versatile natural gas and renewables are already a dream team. Sometimes the wind does not blow or the sun goes in, while at other times surplus power is produced. To meet ambitious climate goals, and for renewable energy sources to increase their share of the energy mix over the long term, renewables need a means of compensating for fluctuations in output.
Variable green power supplies are not the only problem. How can we draw on energy produced in summer during the winter? What is to be done with all the excess power generated by wind and solar farms at times of low consumption?
This surplus energy needs large amounts of storage so that it can be made available during peak periods. The pump storages used up to now do not have sufficient capacity. The solution is obvious. Gas infrastructure in the shape of pipelines and subterranean storage facilities – which can store more gas than is consumed in Austria in a year – already fulfil all the requirements for future use as a storage system for green gas.A number of German studies indicate that using existing gas infrastructure and power-to-gas technology can slash the cost of the energy transformation. This approach would both remove the need to build new power transmission lines and spare consumers the expense of replacing efficient gas central heating systems and appliances.

Green gas not only has immense potential, it is sustainable, affordable and hence available round the clock. In other words, it is the enabler of the energy transformation.

Its flexibility means that gas – and increasingly renewable green gas, thanks to power-to-gas technology – offers a secure, sustainable and climate-friendly supply of energy.

Energy storehouses

Most of the renewable electricity produced in Austria is generated in spring and summer – outside the heating season. Run-of-river power stations produce twice as much energy in summer as they do in winter, and seven out of every ten kilowatt hours (kWh) of solar power are generated in the summer months. But this energy cannot be stored for extended periods because the electricity storage that would be needed is lacking. Existing gas storage facilities are the answer.


The principle behind power-to-gas could hardly be simpler: Surplus solar and wind power is used to split water into oxygen and hydrogen by means of electrolysis. The hydrogen can then be stored for later use, for example as primary energy in fuel cells. A further process stage is also possible: in methanation, the hydrogen reacts with carbon dioxide (CO2) to form methane, the main component of natural gas (typically making up 98 %). The CO2 can be drawn from the atmosphere or it can come from a biogas or industrial plant. The product of the process is renewable synthetic natural gas.
This means that electricity can be converted into gas, making it storable in large quantities for the first time. The process solves one of the biggest problems posed by electricity storage – shortage of space. It can simply fall back on existing natural gas infrastructure, in the shape of the pipeline grid and the gigantic storage facilities. Instead of developing and rolling out expensive, high-tech storage solutions, power can be transformed into synthetic natural gas and stored in depleted gas reservoirs.The process gives rise to no emissions apart from the oxygen released when the water is split. Today the efficiency of the conversion process is already about 60 % – a lot when one thinks that today surplus electricity is often not used at all owing to the lack of storage capacity, and instead wind turbines are idled or whole wind farms taken off the grid.

Underground Sun Storage 

Harvesting, storing and supplying solar energy: RAG tested this groundbreaking approach to energy production and storage in a unique research project, Underground Sun Storage.

The storability of hydrogen produced using solar energy was demonstrated at a small depleted gas reservoir in Upper Austria. Energy from renewable sources that can be retained thanks to storage offers the only straight replacement for conventional energy – and Austria’s gas storage facilities provide the necessary infrastructure. The project is being financed by Austria’s Climate and Energy Fund.

RAG’s constant ability to innovate and commitment to research and development are among its key success factors.

The challenge

In most cases renewable energy sources are difficult to manage. Neither the wind nor the sun obey energy demand. But the electricity grid cannot store energy, so grid operators have to adjust generation precisely to demand. If it were possible to store large amounts of power and inject it back into the grid when needed, generation would no longer be tied to demand. That is why huge energy storage facilities are essential in a world that relies on renewables. In nature, carbon and hydrogen have evolved as primary sources of energy, and the main substances in which energy is stored.

Storing hydrogen

We have taken these processes as a model and imitated them with power-to-gas technology. Using electrolysis, excess energy generated from renewables is transformed into hydrogen, which can be stored in the natural gas network. A range of tests are being conducted to investigate how far the natural gas infrastructure tolerates hydrogen. These have already demonstrated that the existing infrastructure copes well with hydrogen content of up to 10 %.
Finding a solution to the question of storing renewable energy is the key to maximising its contribution to the energy mix and thereby achieving a substantial reduction in CO2 emissions. In terms of the strategic development of energy systems for the future, the research project led by RAG is hugely significant for companies, political decision-makers and public authorities.

“Power-to-gas technology enables conversion of surplus electricity into hydrogen or rather synthetic methane. The Underground Sun Storage project is investigating the storability of hydrogen as an additive to natural gas / synthetic methane in pore reservoirs.“

The research project

The main purpose of this pioneering project was to investigate the hydrogen tolerance of underground gas storage reservoirs. The project demonstrated that gas storage facilities can tolerate hydrogen content of up to 10 %. This means that naturally formed gas storage reservoirs are not a limiting factor within the gas system as a whole, and with their vast storage capacity (more than 8 billion cubic metres in Austria, equivalent to 92 terawatt hours), their role in the energy system of the future could change significantly, since they can be used to store and balance supplies of renewable energy.The project comprised laboratory experiments, simulations and a field trial conducted on an industrial scale at an existing reservoir with similar characteristics to Austria’s large developed storage facilities. The tests were accompanied by a risk assessment, a life cycle assessment, and an analysis of the legal and economic environment. Simulation tools developed in the course of the project were calibrated by comparing the results of the laboratory tests, simulations and the field trial. They will make it possible to investigate many other structures around the world in the same way.

Underground Sun Conversion

Geological history fast forward: over 1,000 metres below ground, where natural gas formed millions of years ago, a microbiological process for producing renewable natural gas is being tested for the first time. It will permit the organic, renewable production of natural gas.

This unique method recreates the process by which natural gas originates, but shortens it by millions of years – like geological history in fast motion. A microbiological process can transform hydrogen and CO2 into methane – renewable natural gas – in suitable gas reservoirs. Converting the energy, increasing the energy density and storing it take place out of sight, in porous rock formations at depths of over 1,000 m.

Manufacturing natural gas

First, hydrogen is produced from solar or wind energy and water (using power-to-gas technology) in an above-ground facility, and then injected into an existing gas (pore) reservoir. At a depth of over 1,000 metres, in a relatively short time naturally occurring microorganisms convert these substances into renewable natural gas – which can be stored in the same reservoir, withdrawn as needed at any time, and transported to consumers via the existing pipeline network.
The aim of the research project is to use existing gas (pore) reservoirs as natural geological “reactors”. The methanation process and storage take place naturally in an underground pore reservoir. This is the key to the project’s huge potential as it promises to provide the urgently needed flexibility that renewable energy currently lacks. It holds out the promise of achieving the creation of a sustainable carbon cycle.
Laboratory tests, simulations and scientific field tests are being carried out at an existing RAG reservoir in collaboration with a group of project partners. A further objective is to test whether the research results can be repeated in other formations around the world. The striven findings are of great importance as they could extend Austria’s lead position in energy storage, and associated research and development. The goal is to apply the methods developed by the project – both the technology and the expertise – on a global scale.

Austrian Climate and Energy Fund lead project

Initial laboratory tests conducted in the Underground Sun Storage project showed that hydrogen injected into the reservoir with CO2 is converted into methane by microbiological processes. The Underground Sun Conversion project was 
initiated on the basis of these findings, and is being implemented by an Austrian consortium led by RAG. The project is being financed by Austria’s Climate and Energy Fund as part of its energy research programme.


Carbon neutral
Renewable natural gas is carbon neutral if CO2 that is already present – for example, from burning biomass – is utilised and absorbed by the production process. This creates a sustainable carbon cycle.

Renewable energy becomes storable
Solar and wind power output fluctuates due to changing weather conditions, meaning that production cannot be adjusted to demand.
The problem of storing renewable energy is solved by converting it into renewable natural gas.

Use of existing infrastructure
Infrastructure already in place can be used for the natural production process, as well as for underground storage in natural gas reservoirs, and environmentally friendly transportation to consumers.