Uniper Energy Storage GmbH
Power to Gas
Key summary
Technical
advantages
• Integration of renewable sources into energy system
and diverse market entries
• Converting electricity into hydrogen, and in a
subsequent step the hydrogen into methane, allows
large quantities of energy to be stored even over
longer periods
• The natural gas infrastructure serves as a
transmission and storage medium
Positive
impacts
• Renewable sources will be better exploited with
Power to Gas and brought to different market
sectors
• Flexibility and ability to store the energy contributes
to a more stable energy system
• Gas production from renewable energies reduces
CO2 emissions
• Large, flexible gas storage capacities are available
for electricity storage
Uniper is developing innovative storage solutions for the
future energy system to balance increasingly intermittent
supply from renewables and demand. In the past there was
no need for large electricity storage facilities because
conventional power stations were able to supply electricity in
line with demand. For natural gas it has always been
different: with large quantities of the natural gas being
imported from remote regions, and the need to balance
seasonal (as well as daily) fluctuations in demand, there is a
well-developed gas storage and transportation
infrastructure.
The Power to Gas approach is building on the advantages of
this well established infrastructure. It is a promising
approach for storing electricity from renewable sources,
converted into hydrogen or methane, during times of
potential grid overload for subsequent use in line with
demand. Considering its flexible applications and its storage
abilities Power to Gas helps to stabilise the energy system.
Moreover, the use of green electricity provides a gas product
made from renewables, which contributes to CO2 emission
reduction.
Conversion from electricity to gas
Main applications
Technology description
Volatile power generation from renewable sources
H2
Electrolysis
H2
H2
Methanation
CH4
Storage
Industrial use
Mobility
Power generation
Heat supply
Modified after: Deutsche Energie-Agentur GmbH (dena)
Transformation of electricity from renewable energy to hydrogen via
electrolysis of water. Green hydrogen can be used for heating,
mobility, industry or power generation. An important transport option
is to feed the hydrogen into the gas grid.
The Power to Gas technology is based on the principle of
water electrolysis – the breaking down of water into its
components hydrogen and oxygen using energy, in this case
electricity from renewable energy. In a subsequent step known as methanation - the hydrogen can be allowed to react
with CO2 to produce methane. A sustainable source of CO2
could be biomethane plants.
Next to the conventional alkaline electrolysis, more efficient
and compact Proton-Exchange-Membrane (PEM) electrolyzers
are being developed to the required Megawatt scale.
In comparison to alkaline electrolyzers, PEM units show faster
load dynamics and have the capacity for temporary overload
operation. Both of these properties are advantages in Power
to Gas applications.
Technology benefits
Bottlenecks in Germany’s electricity grid
Power to Gas offers a number of technical benefits. These
include being able to store energy from wind and solar power,
when the natural occurrence does not meet the demand.
Storage systems provide the link between generation and
demand, allowing energy to be distributed when needed. In
this way, electricity can be used at anytime, anywhere.
Wind energy
Wind energy under
design
Photovoltaic
Another advantage of converting electricity into hydrogen or
methane is the ability to store large quantities of energy even
over long periods of time.
Bottleneck
Transmission grid
The hydrogen can be fed into the natural gas pipeline system
– subject to limitations including not exceeding the limits
defined for the infrastructure and for gas appliances – and in
this way be used as an energy source for gas-fired
equipment.
For methane there are no such limits. Where the hydrogen is
turned into methane by reaction with CO2 as described above,
it can be blended with natural gas at any concentration.
Positive impact on energy infrastructure
Nowadays the increasing share of fluctuating wind and solar
energy push the electricity grid beyond its limits. This is why
the economy is likely to derive the biggest benefit from
renewables if these sources can be integrated into existing
energy infrastructures.
Green hydrogen can be used for the generation of electricity
in gas-fired power plants, in the heat energy market, as a
motor fuel (hydrogen or natural gas mobility) and in industrial
applications. Industrial users are, for example, refineries,
fertilizer manufacturers or the chemical and steel industry.
The blended hydrogen or methane can be shipped to
consumers using existing buried – and hence “invisible” –
natural gas pipelines. Natural gas storage facilities allow the
energy to be stored over long periods of time.
The ability to draw on the gas infrastructure will allow Power
to Gas to ease the load on electricity grids, as more and more
renewable capacity comes on stream. Whilst new
transmission lines will still have to be built, Power to Gas
offers significant room for optimization.
Distribution grid
Conurbation
Most of Germany’s wind capacity is located in the north and north-east
of the country while photovoltaic systems are mostly installed in the
south. Electricity has to be transmitted over long distances. There are
already bottlenecks in the grid. This situation could be eased by applying
the Power to Gas concept to allow electricity from renewable sources to
be stored and transmitted to consumers.
Climate protection
Power to Gas allows renewable energies to be fully integrated
into the existing energy system.
It is a means of using renewable energy even during times of
surplus production. This means that the use of fossil fuels
(e.g. coal, oil and gas) and thus greenhouse gas emissions
will be reduced in the future, because combustion of
hydrogen does not produce any CO2 emissions. In this context,
Power to Gas is an innovative and technically mature tool for
the integration of renewable energy.
Uniper is involved in the development of Power to Gas and
other storage technologies to be able to supply cleaner and
better energy.
Technology in action
Power to Gas pilot plant Windgas Falkenhagen (Germany):
proven technology electrolysis (Alkaline electrolysis).
Power to Gas – PEM Electrolysis pilot plant Windgas Hamburg
(Germany): next generation electrolysis (PEM electrolysis).
[email protected]