IEEE Power & Energy Magazine - July/August 2021 - 14

Luis (Nando) Ochoa and Pierluigi Mancarella
bottom-up flexibility
flexibility from the edge of the grid
I
14
IN MANY COUNTRIES AROUND
the world, households and small businesses
are adopting technologies that
allow them to influence their energy
bills and carbon emissions. We are
talking about rooftop solar photovoltaics,
batteries, electric vehicles (EVs),
electric heat pumps, and so on. Without
a doubt, the appeal and impact of
these technologies, often referred to as
distributed energy resources (DERs),
will continue to grow in the coming
years. And what all these technologies
have in common is that they are located
at the edge of the grid-at the lowest
voltage levels of our electric distribution
networks. Most often, they reside
behind the meter.
Having a DER-rich grid brings many
challenges. At the bottom of the spectrum,
the distribution system infrastructure
has not been designed with
DERs in mind. New power flows due
to excess generation or larger demand
can lead to voltage and congestion issues.
On the transmission system side
of the spectrum, the resulting netdemand
profiles (think of the " duck
curve " ) combined with variability and
partial uncertainty of DER outputs
make the supply-demand balance harder.
Despite these challenges, the inherent
flexible operation of DERs also
brings about many opportunities for
cost-effective operation and planning
across all voltage levels, from the bottom
to the top.
Digital Object Identifier 10.1109/MPE.2021.3072785
Date of current version: 21 June 2021
ieee power & energy magazine
For instance, the coordinated discharge
of a fleet of residential batteries
can provide energy for a short time to
help the system when fast reserves are
needed. Similarly, a fleet of EVs can
stop their charging at times of extreme
system demand. The same principles
can be used to help distribution companies
avoid or defer upgrading substations
or installing new voltage regulating
devices.
The basic idea behind all these
" bottom-up flexibility " concepts is not
new. It has been implemented through
aggregators (that become " big enough "
to participate in markets) or bilateral
contracts with large customers. The
most common technologies being used
in the last decades include air-conditioning
systems, refrigeration systems,
and electric water heaters. These technologies
reduce demand by switching
off or changing settings for short periods
with little impact on the end user's
comfort or requirements. However, the
expected technological diversity and
widespread adoption of DERs in the
coming years make the corresponding
bottom-up flexibility opportunities a
different ball game.
We do not know yet the extent to
which certain DERs will be available
to provide flexibility. A third party
switching off your electric water heater
with relatively large thermal storage
capability is one thing; for most of us,
it will go unnoticed. In contrast, stopping
the charge of your EV might be a
no-go for some people. Understanding
the extent to which this type of flexibility
can help and how to quantify it
is critical. Even if thousands of residential
batteries are ready to discharge
to help the whole system, they would
need to do so in ways that ensure the
distribution network's integrity. We
need ways of incorporating distribution
network constraints when using
bottom-up flexibility. Moreover, energy
is not just about electricity. The
coupling of energy systems and energy
sectors offers further opportunities
for flexible operation. For example,
multienergy system interactions between
electricity and gas systems can
offer flexibility when applied to heating
and cooling supply.
This issue of IEEE Power & Energy
Magazine provides a taste of the
many
exciting
projects
happening
around the world involving bottomup
flexibility. The authors not only
share their technical knowledge about
the different opportunities and challenges
but also the lessons learned
from actual implementations. In each
article, the authors discuss what is
needed to move concepts forward.
No one has a crystal ball, but we trust
these articles give the power and energy
community a glimpse of what
flexibility from the edge of the grid
has to offer.
In This Issue
The articles in this issue come from
different corners of the world: Australia,
Austria, Belgium, China, France,
Italy, Sweden, the United Kingdom,
and the United States.
july/august 2021
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IEEE Power & Energy Magazine - July/August 2021

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