**Capacity Calculation Region (CCR)**

# Definitions

The geographic area in which the coordinated capacity calculation is applied.

**Capacity Mechanism (CM)**

A temporary non-market measure to ensure the achievement of the necessary level of resource adequacy by remunerating resources for their availability, excluding measures relating to ancillary services or congestion management.

**Core Region (also Core Capacity Calculation Region)**

Capacity calculation region as defined in ACER’s Definition of the Capacity Calculation Regions in accordance with Article 15(1) of the Commission Regulation (EU) 2015/1222 of 24 July 2015 establishing a Guideline on Capacity Allocation and Congestion Management and which covers France, Germany, Belgium, the Netherlands, Luxembourg, Austria, Poland, the Czech Republic, Slovakia, Hungary, Romania, Slovenia and Croatia.

**Demand-Side Response (DSR)**

The change of electricity load by final customers from their normal or current consumption patterns in response to market signals.

**Energy Not Served (ENS) **[GWh/year]

– For a single node, the energy which is not supplied during a single Monte Carlo sample/simulation year due to the demand in the node exceeding the combination of available resource capacity and electricity imports. For a geographical area with multiple nodes, ENS is the total energy not surved of all its nodes. A null ENS suggests that there are no adequacy concerns.

**Expected Energy Not Served (EENS)** [GWh/year]

For a given geography, the mathematical average of the ENS calculated over the total number of Monte Carlo sample/simulation years.

**Explicitly Modelled Systems**

Electric systems which are modelled in detail, i.e. electric systems which are an integral part of the European power system and for which System Operations Guideline (SO GL) article 81 or article 106 is applicable. These systems shall be modelled by considering each element of the probabilistic model set in this methodology. Inverse of non-explicitly modelled systems.

**Flow-Based (FB) approach/model**

A capacity calculation method in which energy exchanges between bidding zones are limited by power transfer distribution factors and available margins on a critical network element.

**Flow-Based Market Coupling (FBMC)**

A mechanism to couple different electricity markets, increasing the overall economic efficiency, while taking into account the available transmission capacity between different bidding zones using the FB approach/model.

**Forced Outage (also Unplanned Outage)**

State of a resource capacity when it is unavailable in the power system and the outage was not planned in advance. These outages include breakdowns and any other unforeseen unavailabilities. Inverse of planned outage.

**Frequency Containment Reserves (FCR) (also primary reserves)**

The active power reserves available to contain system frequency after the occurrence of an imbalance.

**Frequency Restoration Reserves (FRR) (also secondary reserves)**

The active power reserves available to restore system frequency to the nominal frequency and, for a synchronous area consisting of more than one load-frequency control area, to restore power balance to the scheduled value. They can either be triggered automatically following a TSO’s signal (aFRR) or manually (mFRR).

**I-SEM**

Stands for Integrated Single Electricity Market, a wholesale electricity market where electricity is traded in bulk across the island of Ireland.

**Loss of Load Duration (LLD) **[h/year]

For a single node, the number of hours during which the node experiences ENS during a single Monte Carlo sample/simulation year. For a geographical area with multiple nodes, LLD is the number of hours during which at least one node of the area experiences ENS during a single Monte Carlo sample/simulation year. A null LLD suggests that there are no adequacy concerns.

**Loss of Load Expectation (LOLE)** [h/year]

For a given geography, the mathematical average of the Loss of Load Durations over the total number of Monte Carlo sample/simulation years.

**National Trends Scenario**

A scenario considering projected demand and supply forecasts, including best estimates on likelihood of retirement, mothballing, new-build of generation assets and measures to reach energy efficiency, and considering the state of the grid in line with the Ten-Year Network Development Plan (TYNDP) and most recent national development plans.

**Net Transmission/Transfer Capacity (NTC) approach/model**

A coordinated capacity calculation method based on the principle of assessing and defining ex ante a maximum energy exchange between adjacent bidding zones. In contrast to the FB approach, capacity allocation takes place entirely ex ante the market clearing.

**Non‑explicitly Modelled Systems (also implicitly modelled systems)**

Electric systems which are not modelled except for their import/export time series with explicitly modelled systems.

**Non-renewable Energy Sources**

Energy from non-renewable sources, namely oil, natural gas, coal, sewage treatment plant gas and nuclear energy. Inverse of renewable energy sources.

**Planned outage**

State of a resource capacity when it is not available in the power system and the outage was planned in advance. In contrast to forced or unplanned outage. These outages include maintenance, mothballing and any other unavailabilities that were planned in advance.

**Renewable Energy Sources (RES) (also energy from renewable sources or renewable energy)**

Energy from renewable non-fossil sources, namely wind, solar (solar thermal and solar photovoltaic) and geothermal energy, ambient energy, tide, wave and other ocean energy, hydropower, biomass, landfill gas, and biogas.

**Replacement Reserves (also tertiary reserves)**

Active power reserves available to restore or support the required level of FRR to be prepared for additional system imbalances, including generation reserves.

**Reserve Capacity**

The frequency containment reserves, frequency restoration reserves or replacement reserves that need to be available to the transmission system operator.

**Target Year (TY)**

A specific year analysed in MAF constituting a dependency of resource capacities, grid capacities and demand levels.

**Thermal Generation**

Production of electricity from thermal energy obtained from the conversion of primary energy sources, namely oil, natural gas, coal, nuclear energy, solar thermal, geothermal energy, biomass, landfill gas, sewage treatment plant gas, and biogas.

**Unit Commitment and Economic Dispatch (UCED)**

A mathematical optimisation problem which determines the commitment schedule of generation units and their level of generation in order to meet demand for every time step of the modelling horizon. The objective of the problem is to minimize operational cost while satisfying the operational constraints of the power system.

**Unplanned Outage**

See Forced Outage.

**Value of Lost Load (VoLL) **[€/MWh]

An estimation of the maximum electricity price that each end user type is willing to pay to avoid an outage.

## Abbrevations

**AD**

Annual Demand

**AHC**

Advanced Hybrid Coupling

**AYD**

Average Yearly Demand

**CCR**

Capacity Calculation Region

**CEE**

Central-East Europe

**CEP**

Clean Energy Package

**CHP**

Combined Heat and Power

**CM**

Capacity Mechanism

**CNEC**

Critical Network Element and Contingency

**CONE**

Cost of New Entry

**CWE**

Central-Western Europe

**DSR**

Demand-Side Response

**EENS**

Expected Energy Not Served

**EF**

External Flow

**ENS**

Energy Not Served

**EENS**

Expected Energy Not Served

**ENTSO-E**

European Network for Transmission System Operators for Electricity

**ERAA**

European Resource Adequacy Assessment

**ETRI**

Energy Technology Reference Indicator

**EUE**

Expected Unserved Energy

**EUPHEMIA**

Pan-European Hybrid Electricity Market Integration Algorithm

**EVA**

Economic Viability Assessment

**FB**

Flow-Based

**FBMC**

Flow-Based Market Coupling

**FO&M**

Facilities, Operation and Management

**FCR**

Frequency Containment Reserve

**FRR**

Frequency Restoration Reserve

**GSK**

Generation Shift Key

**HVAC**

High-Voltage Alternating Current

**HVDC**

High-Voltage Direct Current

**IEA**

International Energy Agency

**I-SEM**

Integrated Single Electricity Market

**LDC**

Load Duration Curve

**LLD**

Loss of Load Duration

**LOLE**

Loss of Load Expectation

**LOLP**

Loss of Load Probability

**LT**

Long-Term

**MAF**

Mid-Term Adequacy Forecast

**MC**

Monte Carlo

**MILP**

Mixed Integer Linear Programming

**MPD**

Maximum Peak Demand

**NGC**

Net Generating Capacity

**NTC**

Net Transfer Capacity

**OM**

Outage Minutes

**P2G**

Power-to-Gas

**P2H**

Power-to-Hydrogen

**P2X**

Power-to-X

**P50**

50th Percentile

**P95**

95th Percentile

**PECD**

Pan-European Climate Database

**PEMMDB**

Pan-European Market Modelling Database

**PRIMES**

Price-Induced Market Equilibrium System

**PST**

Phase Shifting Transformer

**PTDF**

Power Transfer Distribution Factor

**PV**

Photovoltaics

**RAM**

Remaining Available Margin

**RES**

Renewable Energy Source

**SAI**

System Adequacy Indicator

**SHC**

Standard Hybrid Coupling

**SVD**

Singular Value Decomposition

**TFEU**

Treaty on the Functioning of the European Union

**TSO**

Transmission System Operator

**TY**

Target Year

**TYNDP**

Ten-Year Network Development Plan

**UCED**

Unit Commitment and Economic Dispatch

**VoLL**

Value of Lost Load

**WACC**

Weighted Average Cost of Capital