IV. STUDY ON THE FORCED OUTAGE RATES BY N-SIDE

This appendix explains the methodology developed by Elia and N-SIDE for the determination of the necessary metrics regarding forced and planned outages used in this study and future adequacy studies performed by Elia. The outage metrics are used in the modelling of generation units, pumped-storage and HVDC links. It is important to note that the forced outages of nuclear units were assessed separately by Elia prior to this study (see Appendix V).

IV.1. OUTAGE RATES IN PREVIOUS ADEQUACY STUDIES

In the framework of the previous AdeqFlex’21, the forced outage parameters were calculated on a yearly basis based on historical data from 2011 to 2020 for Belgian units. The used data was a combination of ENTSO-E Transparency Platform (ETP) data, where available, and Elia’s internal database, where needed.

III.4. RESIDENTIAL BATTERIES

Regarding storage, the residential batteries do not face all limitations that heat pumps and electric vehicles face. They do not have a load profile, or an energy demand to answer to. The purpose of batteries is to provide flexibility to the consumer by definition. It can be then assumed that batteries will provide flexibility once installed. However, the flexibility could be implicit (e.g. optimising PV generation) or explicit (e.g. bid in the market, providing ancillary services).

Note that the use of batteries with PV could be seasonally dependent: their primary role can be to integrate solar PV in the residential sector in summer, and to provide ancillary services in winter. This way, consumer’s could make sure to recover their investment by maximising self-consumption when their PV produce energy and monetising their asset when they are not producing.

While it has low customer impact to optimise selfconsumption according to tariffs, some resistance and disinterest is likely while tariffs are a free choice.

The offer for grid services and potential loss of asset control can be difficult for some customers to understand and it is harder to quantify the customer benefit, therefore uptake is expected to be significantly lower.

The share of batteries participating to market flexibility is expected to grow with the penetration of smart meters in the system, as well as the presence of market players offering a simple and attractive offer to battery owners.

The method previously used to determine the outage indicators posed some limitations:

• No data is available in ETP data before 2015 and hence both databases had to be combined;

• No ETP data is available for units <100 MW while outage parameters are also required for smaller units;

• Elia’s internal database only provides daily granularity;

• The availability of data for certain technologies in Belgium is limited, which poses a challenge in terms of ensuring statistically robust data. When the number of units is small, it becomes difficult to draw accurate and reliable conclusions based on the available data. Statistical robustness relies on having a sufficiently large and diverse sample size to min- imise biases which could be driven by one specific unit or event in the past:

- CCGT: 20 units (note that some units are split in GT and ST but are part of the same plant);

- OCGT: 11 units;

- CHP: 27 units;

- TJ: 13 units;

- Pumped storage: 2 units;

- Biomass: 5 units;

- Incineration stations: 13 units.

• Due to the limited dataset, a given year in the past could have a strong impact on the unavailability indicators. Given these limitations, Elia and N-SIDE developed an improved method for estimating the outage parameters for future adequacy studies to be used as from AdeqFlex’23. A public consultation was held in November 2022, as part of the AdeqFlex’23 consultation on methodology and scenarios. In addition, the methodology was presented in a WG Adequacy on 28 October 2022 to the stakeholders.

IV.2. METHODOLOGY

To address the limitations mentioned earlier, outage indicators were calculated using a larger dataset that includes data from other countries. By expanding the dataset and using a standardised database, the analysis becomes more robust and reliable. This approach allows for a broader comparison and benchmarking of outage indicators across different regions. Furthermore, the results obtained from this analysis were compared with values reported in other studies and

IV.2.1. OUTAGE INDICATORS

There are three relevant indicators regarding planned and forced outages. These are the average rate, the average duration and the average number of events (see Figure IV-1).

literature reviews. This comparison helps validating the findings and provides additional insights into the outage parameters. By using a larger dataset and considering findings from previous studies, there is less need for frequent updates of outage parameters in future studies. This approach provides a more stable and consistent framework for assessing outage indicators, reducing the reliance on frequent parameter updates.

IV.2.2. DATA SOURCE ASSESSMENT

In this phase, a list of possible data sources was compiled, and each source was evaluated to determine the most appropriate and reliable data source. Specifically, Elia and N-SIDE assessed Elia’s internal database, ENTSO-E Trans- parency Platform (ETP) and transparency platforms from producers active in the Belgian electricity market. Table IV-1 summarises the advantages and disadvantages of the various assessed data sources.

TABLE IV-1 — OVERVIEW OF THE ASSESSED DATA SOURCES

Description ENTSO-E Transparency Platform (ETP) [ENT-4] Elia’s internal database

Advantages Legal obligation for units larger than 100 MW to report outages

FIGURE IV-1 — OVERVIEW OF INDICATORS FOR PLANNED AND FORCED OUTAGES

Disadvantages

Large sample size: outage data for all ENTSO-E bidding zones Reporting of partial outages 15-minutes time granularity Public information

No data for units <100 MW

Only data available as from 2015

Following the assessment, it was determined that, when feasible, the ENTSO-E Transparency Platform (ETP) would be utilised, supplemented by Elia’s internal data in the absence of ETP data (for units below 100 MW). While transparency platforms offered by electricity market producers in Belgium

• Outage data on all unit sizes

Producers’ transparency platforms such as NordPool [REM-1], EDF [EDF-1], TotalEnergies [TOT-1], Engie Transparency [ENG-1]

• Data available for more than 10 historic years Reporting of partial outages 15 minutes time granularity Public information

• Only data for Belgium

• Only daily granularity

• Not public information

Mainly data for units >100 MW Different platforms per producer Limited number of years generally provided similar data to that available on ETP, they only covered a limited number of years and increased the complexity of aggregating multiple data sources. Furthermore, not all producers maintain a data platform, and data on smaller units was scarce.

IV.2.3. DEFINITION OF THE DATA SAMPLE

The indicators from Figure IV-1 should be understood as:

• The planned outage rate is the amount of planned unavailability to the total energy that could have been produced. The total energy that could have been produced is the unplanned unavailable energy + the planned unavailable energy + the available energy (referred as 'Total energy');

• The forced outage rate is the ratio of unplanned unavailable energy to the sum of the available energy and the unplanned unavailable energy;

• Average duration of forced or planned outages;

• Average amount of outages (forced or planned) per year.

Only a limited number of units for each technology exists in Belgium and for some technologies (e.g. CHP) most units are smaller than 100 MW and little ETP data is therefore available. The number of Belgian units considered per data source for each technology is presented on Table IV-2. TABLE

To obtain a larger and more representative sample, the data for Belgium is combined with ETP data for a list of representative other countries for all technologies considered. The outage indicators are calculated on this combined dataset. The other countries considered are:

• France;

• Netherlands;

• Germany;

• United Kingdom;

• Italy.

Since data in ETP is only available as from 2015, the outage metrics are calculated on the time horizon 2015-2021 for the whole dataset, for each data source and each country.

IV.2.4. DATA QUALITY AND PRE-PROCESSING

Both ETP and Elia’s internal database were found to contain some data quality issues which were corrected by applying 3 pre-processing steps:

1. Removing duplicate outages: some outages are reported twice for the same period and should therefore only be considered once;

2. Cleaning of overlapping outages: some outages were found to be overlapping with other outages. This would cause outages to be counted twice for some periods.

IV.2.5. LITERATURE REVIEW

The forced outage rates calculated for Belgium and other representative countries were compared with results from other studies on outage rates and the outage rates given by ENTSO-E in the common data for thermal units.

The sources considered in the literature review are:

• The annual system report by Red Eléctrica [REE-1];

• 2021 State of the Market Report for PJM by Monitoring Analytics [MAN-1];

IV.2.6. METHODOLOGY OVERVIEW

Following the analysis steps described in the previous paragraphs, the approach to obtain the final outage indicators is summarised on Figure IV-2.

First, the relevant data was collected from the chosen sources. After applying the pre-processing steps, the data was compared to producers’ transparency platforms. This robust dataset was then used to calculate the necessary indicators for Belgium and other countries. After a comparison

Overlapping outages were therefore split and overlapping periods removed;

3. In case a forced outage is immediately followed by a planned outage, the planned outage is converted to a forced outage. It is assumed that an unexpected forced outage cannot change to a planned outage after a short period of being in forced outage. In the opposite case where a planned outage is followed by a forced outage, no adaptations are made.