IEEE Power & Energy Magazine - November/December 2019 - 71

While the electricity sector enters new markets via electrification, gas and heat systems get a new role as a fuel-integration
and storage system. The gas system must cover extreme weeks,
integrate green gas, and adapt to the control of power-to-gas
units to facilitate its participation in different markets (electricity, district heating, and RES gas). The heat system can also
be used for energy system stabilization by combining several
heat resources and leveraging thermal storage. The following
sections provide examples for sector coupling in different parts
of the world.

Sector Coupling Results in Europe
The EU Commission's 2018 "Clean Planet for All" report
provides a comprehensive picture of what compliance with
the Paris Agreement would look like in electricity, heating,
transport, industry, and agriculture (Figure 3). As heating,
transport, and industry demands are electrified, the share of
electricity in final energy consumption will rise from just more
than 20% in 2015 to 50% in 2050. Gross electricity generation
doubles from 2015 to 2050 and is even higher in scenarios with
a large share of power-to-fuel technologies. At the same time
that electricity demand rises, it is also decarbonized, with the
share of renewables ranging from 81 to 85%. The total share
of wind and solar generation alone increases from 65 to 72%.
This means that total wind and solar generation in 2050 would
be greater than all electricity generation today.
In 2050, in the heating sector, the share of residential space
heating demand met by electricity (primarily heat pumps) rises
to 30%. In the transport sector, 80% of vehicles are completely
electric, while just more than 15% have hydrogen FCs.
When analyzing future EU scenarios, it is important to
represent the full continental weather variability and events
that unfold over several days, such as cold weather that coincides with a continent-wide lull in wind and solar generation.
Such events are particularly challenging for power systems
with wide-scale electrification of heating. The flexibility provided by long-term storage, such as thermal energy storage
or synthetic fuels, can help to bridge these difficult periods
and keep costs low.
A doubling of electricity generation, with the majority coming from VREs, requires detailed grid modeling to assess the
impact on the energy system's behavior and costs. As a first
step, as well as answering the legal request for interlinked
modeling of the electricity and gas sectors, the EU Network
Transmission System Operators for Electricity (ENTSO-E) and

EU Network Transmission System Operators for Gas (ENTSOG) applied jointly developed scenarios that elaborate on the
infrastructure-development plans for electricity and gas. This
enabled the investigation of several possible futures to deliver
a more consistent picture than before, while also allowing the
quantification of developments in other sectors.

Sector Coupling Results in the United States
The United States Mid-Century Strategy for Deep Decarbonization was produced in 2016 and calls for the nearelimination of GHG emissions by 2050. This strategy
focuses on the decarbonization of the electric power sector and electrification of transportation, buildings, and the
industrial sector, as well as development of carbon capture,
utilization, and storage technologies. The result of this
transition is estimated to nearly double end-use electricity
demand, with half of the increase coming from transportation. The potential for end-use efficiency measures has been
shown to mitigate the increase in electricity demand significantly or even entirely.
However, much of the action on renewable energy integration has taken place at the state level. Currently, 29 U.S. states
and the District of Columbia have adopted renewable portfolio
standards (RPSs), with the most ambitious goals in Vermont
(75% by 2032), California (60% by 2030), and New York
(50% by 2030). While RPS policies have existed for more than
a decade, nearly all have been updated and revised to increase
targets under improving performance and economics around
renewables. Most states have managed to attain RPSs and, in
some states and regions, RES development has even outpaced
RPS targets, such as in Texas and the Midwest.
In pursuit of these goals, the share of renewable sources in
the U.S. energy sector continues to grow, reaching 18% of total
energy consumption in 2017, including 7% hydro generation
and 11% in total from wind, solar, geothermal, and biomass.
To fully realize any decarbonization strategy and the statelevel RPSs, the penetration of variable renewable resources
will have to increase significantly, to nearly 80% by 2050.
Recent studies by the National Renewable Energy Laboratory
have explored the efficacy of leveraging geographic diversity
to provide resource and operational flexibility. One example is
the Interconnections Seams project, a partnership with several
other national laboratories, universities, and industry partners.
This effort is exploring cost-effective options to upgrade the
North American electric grid to leverage geographic diversity

table 1. Time horizons for flexibility in the energy sector.
Instantaneous

Hour/Day

Month/Year

Long-Term Disruptors

Security of the
supply during
system faults and
actions

Balancing
variable wind
and PV

* Dry/wet year
* Wind year variation
* Extreme years
* Change of market prices for the
fuel-shifting primary resource

* Breakthrough for new technologies (FCs, hydrogen)
* Price setting and requirements for emissions
* Focus on bioresources and sustainability
* Focus on balance food versus fuel
* New fuel types (DME, methanol, hydrogen)
* Digitalization

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IEEE Power & Energy Magazine - November/December 2019

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