IEEE Power & Energy Magazine - November/December 2021 - 74

response needed over extended durations
and different seasons and the
need to recover any fixed costs
with the same challenge of low
utilization that exists for generation
resources.
Many seasonal storage concepts
focus on producing storable
chemical fuel. This typically
involves electrolytic hydrogen. This
fuel is either used directly or converted
to liquid or gaseous fuels
with higher volumetric energy
density and greater ease of storage
and transport. Examples include
synthetic methane, which requires
a source of renewably sourced carbon,
or ammonia. An alternative to
the hydrogen pathway is the use of
biofuels, which have the advantage
of nearer-term availably. However,
there is a significant disadvantage
of limited ultimate availability and
competition from the transport sector.
Figure 5 illustrates possible fuel
production pathways for seasonal
electricity storage.
Renewably derived fuels can be
used in a variety of combustion generators
or potentially in fuel cells.
There are retrofit possibilities of existing
combustion-turbine and combined-cycle
generators, which could
repurpose the existing infrastructure
and a trained workforce. Using these
units can provide frequency-responsive
services including physical inertia,
system strength, and opportunities
to use generators as synchronous
condensers via clutches. This could
help avoid the challenges associated
with 100% inverter-based resource
systems. The role of seasonal electricity
storage in this pathway could
be greatly enhanced by its role in
economy-wide decarbonization as
these carbon-neutral or carbon-free
fuels could be used for heating, industrial
processes, chemicals, and
transportation fuels.
A View From Europe
Renewable energy will play a major
role in establishing a carbon-neutral
energy system for Europe. The
74
ieee power & energy magazine
november/december 2021
700
800
900
400
500
600
100
200
300
Consumption Generation
figure 6. Electricity demand and generation at a 95% renewable scenario in Germany for 2050. BEV: battery electric vehicle; PHEV: plug-in hybrid electric vehicle;
REEV: range-extended electric vehicle; CCGT: combined-cycle gas turbine; ROTR: run of the river; CHS: classic hydro storage; PHS: pumped hydro storage.
Power Demand
Increases Due to
New Consumption
From Heat and
Transport Sectors
Heat Pumps (Decentralized)
Air Conditioning
BEV/PHEV/REEV
Electric Trucks
Other
Curtailment
Net Import
Combined Heat and Power
(Cogeneration CCGT)
Hydro (ROTR, CHS, PHS)
Waste and Sewage
140 GW
Power-to-Heat
Centralized/Industry Heat Pumps
Conventional
40 GW
Offshore Wind
Renewable Energy Generation is
the Main Source of Energy
With Only Limited Generation From
Conventional Power Plants
Onshore Wind
(Strong + Low Wind Turbines)
Germany
North Sea Offshore
Network 2050
Target Scenario
200 GW
Solar PV
(Rooftop + Utility Scale)
Annual Energy (TWh)
Additional Power Demand

IEEE Power & Energy Magazine - November/December 2021

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