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Storing excess power in the gas grid

Power-to-gas

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Power (GW) Excess power

140

120

100

80

60

40

20

0

0 8 /0 5 0 9 /0 5 1 0 /0 5 1 1 /0 5 1 2 /0 5 1 3 /0 5 1 4 /0 5 1 5 /0 5 1 6 /0 5 1 7 /0 5 1 8 /0 5 1 9 /0 5 2 0 /0 5 21/05

(Two week period)

OH

H+

Anode Cathode

Current

+

Power-to-gas

Excess power is converted into

methane using electrolysis and CO2.

The methane can be transported and

stored in the gas grid, and can be

converted into power as required.

Offshore wind energy

Onshore wind energy

Excess power from

renewables

Photovoltaics

Electrolysis

Combined heat and power units

Methanisation

Methane (CH4)

Transfer station

Natural gas grid

Heating

network

Power grid

CO2

H2Microorganisms

Geothermal

Hydroelectric

Photovoltaics

Offshore wind

Onshore wind

Load

Producing hydrogen from

excess power

Microorganisms and CO2act

on the hydrogen, converting

it into synthetic methane.

Methane is injected directly

into the natural gas grid.

Power-to-gas: Storing excess power in the gas grid

Excess power Electrolysis Methanisation Power / gas grids

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The expanding use of renewables creates

new challenges for the power supply sector.

Weather-dependant renewable energy

sources, such as wind and the sun, inevitably

lead to peaks in power generation. Currently,

these can still be balanced out by reducing

the output of conventional power stations. As

the proportion of renewable energy grows,

innovative storage technologies will become of

real importance.

The German natural gas grid has immense

storage capacities. This means that the

production of synthetic methane from

excess wind or solar power with the help of

power-to-gas technology now presents real

opportunities.

MicrobEnergy GmbH specialists in methanisation

MicrobEnergy GmbH, which is part of

the Viessmann Group, develops and sells

microbiological products and technical system

components. The company, furthermore, also

specialises in process control and optimising

biological systems.

Electrolysis as intermediate step

The basic principles behind power-to-gas

can be described as follows: Excess power

is converted into hydrogen by means of

electrolysis. This is followed by what is known

as the methanisation stage, in which synthetic

methane is obtained from hydrogen and

carbon dioxide (CO2). The required CO2can

be sourced from industrial processes, the

surrounding air or biogas plants.

The methanisation of excess power makes

conventional power stations redundant

Microorganisms convert

power into methane

MicrobEnergy uses highly specialised

microorganisms, which convert hydrogen and

carbon into pure methane. The microorganisms

function at ambient pressure and temperature,

and there are no special requirements

regarding the purity of the source gases.

The synthetic methane obtained in this way

can either be held in a gas storage facility and

converted into electricity with a CHP unit as

required, or can be injected directly into the

natural gas grid.

Linking the power and natural gas grids

Power thus becomes the primary energy

and can be used nationwide to generate

heat, or can be converted back to electricityas required, via combined heat and power

stations.

This link between the electricity grid and

natural gas grids is an important condition for

the successful transition from conventional to

renewable fuels.

Microorganisms directly convert

hydrogen and carbon into methane.

The chart shows the power from

renewables that is fed into the grid

over a typical two week period.

Geothermal

Hydroelectric

Photovoltaics

Offshore wind

Onshore wind

Load

Power generated from renewables

Source: FhG IWES

Output[GW]

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9440 790 GB 03/2013

Copyright Viessmann.

Duplication and alternative use only with prior written consent.

Subject to technical modifications.

Viessmann Werke GmbH & Co. KG

35107 Allendorf (Eder)

Telephone +49 (0)6452 70-0Fax +49 (0)6452 70-2780

www.viessmann.com