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Research and development

Wind + sun = gas
– this is the equation behind “power to gas”, a revolutionary new technology that could hold the key to affordable transportation and storage of solar and wind energy.

Together, versatile natural gas and renewables are a dream team. Sometimes the wind does not blow or the sun goes in, while at other times surplus power is produced. For their share of the energy mix to keep on growing over the long term, renewables need a means of compensating for fluctuations in output.

Huge potential 

Intermittent renewable electricity output is not the only problem. Something will also have to be done with all the excess power generated by giant wind farms and solar parks at times when demand is low. This surplus energy needs to be stored so that it can be made available during peak periods, but the capacity of the pumped storage plants used to date is far from sufficient. The answer is gas. The gas transportation and storage infrastructure in place has all the makings of a buffer storage system for green power. 

Eco-friendly technology 

Energy companies and research institutes in Austria and Germany are working intensively on new approaches to efficient, large-scale electricity storage. Power to gas technology is particularly promising. This involves converting renewable electricity into gas and using existing gas infrastructure to transport and store it. The principle behind this new, environmentally friendly technology could hardly be simpler. Surplus solar and wind power is used to split water into oxygen and hydrogen by means of electrolysis. This is followed by the methanisation stage, in which the hydrogen is reacted with carbon dioxide (CO2). 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. Methane is the main constituent of natural gas, making up around 98% of its content. It can be injected into the gas grid and used in the same way as conventional natural gas to fuel domestic space or water heating, industrial processes, and fleets of gas-powered vehicles, or alternatively for gas-fired electricity generation. 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 big step forward in view of the fact that 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. 

Using existing gas infrastructure 

Thanks to methanisation, electricity can be converted into 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 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 and elaborate new storage technologies, the power would be transformed into synthetic natural gas and stored in depleted gas reservoirs.

„Europe is committed to renewables, but we need reliable energy supplies around the clock. Only gas can pull that off. Cutting-edge power-to-gas technology is capable of transporting and storing solar and wind energy affordably, which would make them constantly available. The infrastructure is already in place – we have the pipelines and storage facilities to do the job.”
Markus Mitteregger, Chief Executive Officer, RAG

Underground Sun Storage – stocking up on sunshine

Harvesting, storing and supplying solar energy: RAG is currently testing this groundbreaking approach to energy production and storage in a unique pilot project. Storage of hydrogen, produced using solar energy, is being trialled at a small, natural, depleted gas reservoir in Pilsbach, Upper Austria.

Thanks to their storability, renewables are the only energy forms that can act as a straight replacement for conven-tional energy – and the gas storage facilities already operating in Austria provide the necessary infrastructure. 

In terms of the strategic development of energy systems for the future, the results of the pilot will be hugely significant for companies, political decision-makers and public authorities. 

The project was selected by an international panel of experts and is being financed by Austria’s Climate and Energy Fund.

For more information visit www.underground-sun-storage.at


The successful Underground Sun Storage project, which focused on the storage of wind and solar energy in naturally formed gas reservoirs, is to be taken to the next stage.

Building on the research conducted so far, for the first time the Underground Sun Conversion project will enable production of natural gas directly within a gas reservoir using a microbiological process initiated specifically for this purpose by RAG, and to store it in the same reservoir. 

This innovative method is unique worldwide, and recreates the natural process by which gas originates, but shortens it by millions of years – geological history in fast motion.

First, hydrogen is produced from solar or wind energy and water in an above-ground facility, and then injected into an existing gas (pore) reservoir, together with carbon dioxide – creating a sustainable carbon cycle. 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. 

For more information visit www.underground-sun-conversion.at