IEEE Power & Energy Magazine - March/April 2021 - 54

Power (kW)

Frequency (Hz)

On the economic side, the provision of primary frequency control is attractive, but network tariffs/taxes and
hardware performance (mainly losses) may negatively affect
the business case. Particular emphasis is given to battery
degradation, which is a topic of concern for vehicle owners.
Measurements on the vehicles' health are ongoing, and early
results show limited degradation despite a rather intense
duty cycle for the provision of the service.
EcoGrid 2.0 was a large and pivotal project in the system integration of demand-side flexibility use on both distribution and transmission levels. It proposed, implemented,
and tested a local flexibility market for the procurement of
DSO services. Such a local flexibility market can be easily
integrated into power markets and system operation, as it

50.06
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49.98

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Time (min)
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Time (min)

Requested Power

Provided Power

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Delivered Load Reduction (kW)

figure 6. The provision of frequency containment reserve
for normal operation from 21 EVs located on the island of
Bornholm. (Data courtesy of NUVVE.)

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Requested Load Reduction (kW)

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figure 7. The requested versus delivered flexibility from
households with heat pumps or direct electric heating on
the island of Bornholm. Each point represents a response
from an average of 100 households.
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ieee power & energy magazine

operates in parallel to the existing markets. The demonstrations involved 800 flexible residential customers with controllable heating loads on the island of Bornholm.
The developed local flexibility market in the EcoGrid 2.0
project was designed such that DSOs can acquire flexibility
services from aggregators in a market-based environment.
The potential use of flexibility from the DSO side could
be to reduce consumption during periods of exceptionally
high demand. Another use of aggregator flexibility could be
avoidance of the disconnection of customers during periods
of planned maintenance of the distribution network.
A particularly attractive feature of such a market is that
potential conflicts from the use of flexibility at both DSO
and TSO levels can be resolved without the need for explicit
DSO-TSO coordination. For example, in the case of overloading distribution network components due to the aggregator activation of flexibility at the TSO level, the DSO
can activate acquired services and alleviate the congestion.
These services have been offered by aggregators, and potential DSO service activations are incorporated into the aggregator's operational planning so that the consequences on the
delivery of other services to the TSO will be to the aggregator's knowledge.
EcoGrid 2.0 operated the developed market with two
competing aggregators. These two aggregators virtually
participated in the Danish balancing market while, at the
same time, offering DSO services through the local flexibility market. One of the main goals of the project was the provision of DSO flexibility at low aggregation levels, even at a
low-voltage level. The results from a series of tests, typically
involving around 100 households, are illustrated in Figure 7.
Although relying on a proven technology with limited functionality and flexible loads could not be metered separately
(each house was equipped with one smart meter, measuring
the total net demand), DSO load-reduction services could be
delivered with appropriate accuracy.

Conclusion and Future Perspectives
Flexibility is becoming more abundant in power systems as
more DERs are being installed and technological barriers are
gradually eliminated. Numerous research projects and experiences from power market participation have demonstrated
that flexible resources can offer power system services while
meeting the technical requirements of system operators.
However, it is challenging to unlock this large potential and
use it to enhance the energy security of the power system.
Demand-side flexibility needs to be utilized on multiple
market levels to fully realize its potential and broaden the
spectrum of commercial opportunities for asset owners
and aggregators. There are currently many parallel developments that lead to an emerging multilayered landscape.
Energy communities are promoted by several stakeholders, including the EU, as a means of the democratization
of energy procurement, which empowers and engages end
users. Denmark is very active in this field, with several
march/april 2021

IEEE Power & Energy Magazine - March/April 2021

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