IEEE Power & Energy Magazine - November/December 2015 - 75

The Danish Solution
As shown in Figure 9, an analysis of the future Danish energy
system concluded that wind power will increase by 1.5 to
three times today's levels between now and 2035. Energy
use was investigated in detail, taking into account all sectors
including heat, transport, and industry through 2050. For the
future variant know as "wind track," in general the use of
natural gas is expected to decrease to about one third over the
2011 level by 2035, while the use of electricity (mainly produced by wind, solar, and geothermal) is expected to increase
threefold during the same period.
To evaluate flexibility needs for that future, the residual
load (i.e., load minus wind minus solar power) has been
analyzed for different time periods based on a ten-year time
series for Denmark and on neighboring countries' production and demand (see Figure 10). Results showed that flexible demand and vehicle-to-grid provide very useful service
in periods shorter than five hours but that for periods lasting longer than 12 hours, other means, e.g., exchange with
neighbors like Norway and Great Britain, play an important role because these neighbors might have spare capacity
when Denmark is under pressure.
Thus, especially for short-term periods, flexibility has to
be ensured using market means. This means that flexibility
should get a price reflecting market needs. In this context,
demand-side management and vehicle-to-grid solutions are
important. Another possibility could be to change today's
accounting system for balancing power, which is partly
being socialized, to a system where the responsible market
participant has to finance any unbalances-which might
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and activates the services at the European level. Such
a development should be justified by a solid cost-benefit
analysis. With its Network Code on Electricity Balancing,
ENTSO-E is heading in the right direction. However, at
this stage the code only deals with the integration of balancing markets and the activation of balancing and reserve
services in a different country. The definition of the reserve
requirements and the control those requirement must fulfill
remain at a national level.
Among other examples, Spain and its neighboring TSOs
have already started to cooperate on exchanging reserves
by introducing a cross-border mechanism for activation of
replacement reserves. As of June 2014, the Spanish TSO
REE is participating in BALIT, a cross-border platform
that allows TSOs to activate replacement reserves bids in
a neighboring TSO if there is available cross-border capacity and the neighboring TSO bid is cheaper than the bids
for such reserve made available by the internal replacement reserve providers. Such cross-border mechanisms can
help integrate additional VR energy, as they can be used to
exchange unexpected generation surpluses after the intraday
market has closed. This allows, for example, the export to
France of excess generation in the Spanish system if there is
still available export capacity.

Electric Cars
(Incl. Plugin Hybrid)
DH Heat Pumps

DH Heat Pump
Decoupling
Classic Decoupling

Process Heat
Individual
Heat Pumps
Classic Elec.
Consumption
Solar and Wind

Process Decoupling
Individual Heat
Pump Decoupling
Need for Controllable
Power Plant Capacity
Electric Vehicle Decoupling

Electric Vehicle V2G

figure 10. Denmark's maximum need for residual electricity production for different periods (positive: noninterruptible consumption; negative: interruptible consumption
together with RES production.)

result in unbalances being moved from the hour of operation
to intraday or even day-ahead markets.

Ancillary Services from VR
With increasing shares of VR, it becomes obvious that VR
will also have to be able to provide different ancillary services. Various pan-European and national studies and demonstration projects, such as REserviceS or MetaPV, have
analyzed the technical potential for VR to provide selected
ancillary services such as frequency control and voltage control. However, priority dispatch and market barriers limit the
participation of VR in providing ancillary services.
In some countries, however, VR is slowly starting to enter
ancillary service markets. In Denmark, for instance, negative spot prices have been introduced to the day-ahead markets to release the system during hours of surplus energy.
This is also influencing some of the VR operation. Currently, most onshore wind turbines are paid a fixed amount
on top of the spot price. In cases of negative spot prices, they
bid into the market with the negative value of the subsidy.
The older offshore wind farms are paid a fixed amount per
MWh produced, no matter the market prices, which leaves
downward regulation potential unused at times of surplus
power in the system. By contrast, for the last installed offshore wind farm (Anholt, 400 MW), this system has been
changed: in cases of negative spot prices, no compensation is
paid; instead, the owner must pay the negative spot price for
producing or, alternatively, stop electricity production. Since
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - November/December 2015