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Storing Green Electricity
as Natural Gas
Renewable
electricity can be transformed into a substitute for natural gas.
Until now, electricity was generated from gas. Now, a German-Austrian
cooperation wants to go in the opposite direction. In the future, these
researchers and entrepreneurs would like to store surplus electricity --
such as from
wind power or
solar energy -- as climate-neutral methane, and
store it in existing gas storage facilities and the natural gas network.
Throughout the world, electricity generation is based more and more on wind
and solar energy. So far, the missing link for integrating renewable energy
into the electricity supply is a smart power storage concept. Because when
the wind is blowing powerfully, wind turbines generate more electricity than
the power grid can absorb. Now, German researchers have succeeded in storing
renewable electricity as natural gas. They convert the electricity into
synthetic natural gas with the aid of a new process. The process was
developed by the Center for Solar Energy and Hydrogen Research
Baden-Württemberg (ZSW), in cooperation with the Fraunhofer Institute for
Wind Energy and Energy System Technology IWES. Currently, Solar Fuel
Technology, the Austria-based partner company, is setting up the industrial
implementation of the process. One advantage of the technology: it can use
the existing natural gas infrastructure. A demonstration system built on
behalf of Solar Fuel in Stuttgart is already operating successfully. By
2012, a substantially larger system -- in the double-digit megawatt range --
is planned to be launched.
For the first time, the process of natural gas production combines the
technology for hydrogen-electrolysis with methanisation. "Our demonstration
system in Stuttgart separates water from surplus renewable energy using
electrolysis. The result is hydrogen and oxygen," explains Dr. Michael
Specht of ZSW. "A chemical reaction of hydrogen with carbon dioxide
generates methane -- and that is nothing other than natural gas, produced
synthetically."
With the rapid expansion of renewable energies, the need for new storage
technologies grows massively. This is of special interest for energy
utilities and power companies. "So far, we converted gas into electricity.
Now we also think in the opposite direction, and convert electricity into
'real natural' gas," explains Dr. Michael Sterner of Fraunhofer IWES, who is
investigating engineering aspects and energy system analysis of the process.
"Surplus wind and solar energy can be stored in this manner. During times of
high wind speeds, wind turbines generate more power than is currently
needed. This surplus energy is being more frequently reflected at the power
exchange market through negative electricity prices." In such cases, the new
technology could soon keep green electricity in stock as natural gas or
renewable methane.
"Within the development of this technology, ZSW has been guided by two core
issues," explains Michael Specht: "Which storage systems offer sufficient
capacity for fluctuating renewable energies that depend on the wind and
weather? And which storage systems can be integrated into the existing
infrastructure the easiest?"
The storage reservoir of the natural gas network extending through Germany
is vast: It equals more than 200 terawatt hours -- enough to satisfy
consumption for several months. The power network has only a capacity of
0.04 terawatt hours by itself. The integration into the infrastructure is
simple: The natural gas substitute can be stored like conventional natural
gas in the supply network, pipelines and storage systems, in order to drive
natural gas cars or fire natural gas heating systems.
The new technology aims at facilitating the integration of high shares of
fluctuating power generation from renewable energies into the energy system.
One goal is to structure the delivery of power from wind parks on a
scheduled and regular basis. "The new concept is a game changer and a new
significant element for the integration of renewable energies into a
sustainable energy system," adds Sterner. The efficiency of converting power
to gas equals more than 60 percent. "In our opinion, this is definitely
better than a total loss," says Michael Specht. A total loss looms if, for
instance, wind power has to be curtailed. The predominant storage facility
to date -- pumped hydro power plants -- can only be expanded to a limited
extent in Germany.
In order to push the new energy conversion technology forward, the two
German research institutes have joined together with the company
Solar Fuel Technology of Salzburg. Starting in 2012, they intend to
launch a system with a capacity of approximately 10 megawatt.
Resouce:
http://www.sciencedaily.com
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