INTRODUCTION
TO THE
FLEXIBILITY
CHALLENGE
Florence Forum
Day One, 08 October
High level conference on a new energy
market design
Since generation must balance demand at every second, generation must be able to follow the load
variations (or the load must be able to adapt to generation constraints). This ability of the system to
cope with fast variations in demand and/or generation is the system flexibility. The load curve to be
served by dispatchable thermal and main hydro generators is the residual load (RL), which is the
actual load (L) minus production of wind (W), solar (S) and must-run generation.
The ENTSO-E Scenario Outlook & Adequacy Forecast (SO&AF) 2015 report provides for the first time
information at Pan-European level about the potential lack of flexible generation in the expected
power system operation, by use of residual load (RL) assessments. Residual load is characterized
by very sharp ramps, and very diverse and unpredictable profiles for similar days. This represents a
new challenge for the power system. Residual load is a useful indicator to show the flexibility and
ramping needs for adequate power system operation.
An example from SO&AF 2015 is presented below. We have selected a typical week from the summer
season. In this case, the climate conditions are causing relatively extreme power ramps, especially
in combination with a flat daily load shape. Such conditions of power system operation with high
penetration of wind and solar installations show an extended need for flexible power or crossborder exchanges.
In SO&AF 2015, a statistical analysis of the RES penetration and hourly RES ramps was performed
for the scenarios 2016, 2020, 2025, as illustrated below. A general trend of increased RES penetration
is observed, shown by the increasing tails of the right hand side of distribution below (left figure).
ENTSO-E AISBL • +32 2 741 09 50 • [email protected] • www.entsoe.eu • @entso_e
[p %]
14%
Distribution of RES penetration
including must run (in % of load)
12%
[p %]
25%
Distribution of hourly RES ramps
(in % of load)
20%
10%
15%
8%
6%
10%
4%
5%
2%
0%
0%
20% 40% 60% 80% 100% 120% [1-RL
140%%]
B-2016
B-2020
B-2025
0%
-10%-8%-6%-4%-2% 0% 2% 4% 6% 8%10% [ramp %]
B-2016
B-2020
B-2025
These figures are representive of Denmark and Germany
SO&AF 2015 analysed the magnitude of extreme, but still likely to occur, power ramps in the
system. For each country, we calculated the 99.9% +/– percentile of the absolute residual load
ramps, simulating 14 climate years for the 2020 system scenario. This is equal to the nine worst
hourly residual load ramps (8760 × 0.1% ~ 9 hours) during the year. Countries on the graph are in
descending order of ramp size.
These charts and our analysis highlight the challenging conditions that TSOs face to keep the
system in balance with increasing shares of variable RES. The need for flexibility, in fact, is
strictly correlated with the volume of RES ramps observed.
Against this evidence, it is fundamental that the market design – and price signals in particular
- enhance system flexibility via new investments and market actors’ behaviours. Introducing
balancing responsibility for all RES generators, as well as designing cost-reflective imbalance
prices would be a decisive market factor to stimulate flexibility in a cost-efficient manner. Generators,
including RES, would be incentivised to adjust their position in day-ahead and intraday markets,
therefore reducing the need for greater TSOs reserves to deal with imbalances and uncertainty.
ENTSO-E AISBL • +32 2 741 09 50 • [email protected] • www.entsoe.eu • @entso_e