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About Task 25/63
Energy system impact studies are important for defining targets for wind and other variable renewable energy, and for defining future decarbonising pathways. Task 25/63 works towards commonly accepted methodologies to be applied in system impact studies for power and energy systems dominated by wind and solar energy. International collaboration is key to harvesting knowledge from both practical experience and studies in different countries, in the evolving power and energy systems of the future.
The ultimate objective of Task 25/63 is to provide information to facilitate the highest economically feasible wind energy share within electricity power systems worldwide. The task supports this goal by analyzing and further developing the methodology to assess the impact of wind power on power systems.
This information facilitates economically feasible wind energy penetration in electricity systems worldwide. Task 25/63 brings best practices from energy system study methods as well as experience and study results to member countries and a wider audience through IEA, IRENA, Global Power System Transformation (G-PST) and Energy System Integration Group (ESIG). On top of these international network stakeholders, the system operators are the main target group of Task 25/63; they are joining Task 25/63 work directly (from Denmark, Italy, France) and as observers (Germany, Finland, Spain, Japan, Sweden, the UK).
Task 25 ran from 2006 to 2024. As the work evolved from wind integration studies to cover both wind and solar energy, and both electricity and energy systems, the name of Task 25 was changed from Design and Operation of Power Systems with Large Amounts of Wind Power to Design and Operation of Energy Systems with Large Amounts of Variable Generation 2018. A new task – Task 25/63 Twenty Fifty Integration of Variable Energy (TWENTY-FIVE) – started in 2025, building on the collaboration and knowledge developed during 2006–2024.
The international forum has been formed for the exchange of experience gained and studies conducted. The case studies address different aspects of power system operation and design:
- Planning: adequacy, net zero and scenario studies, sector coupling
- Operations: short- and long-term flexibility
- Stability: stability studies, capabilities of inverter-based resources, tools and models
- Markets: long-term markets, short-term markets, system services
Participation
Task 25/63 Participants
TSO is Transmission System Operator
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Task 25/63 Sponsors
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China CWEA
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Who can participate in Task 25/63?
For the 2025-28 phase, 14 member countries and 2 sponsors are involved in Task 25/63. Most countries have participation from their TSOs (Transmission System Operators) either following their national project or participating directly in the Task 25/63 meetings.
To join a task, a member country of the IEA Wind TCP designates one or several institutions that agree to the obligations of task participation, including paying the annual fee and performing specified parts of the work plan. Institutions located outside IEA Wind TCP member countries may also join a task if they agree to the same obligations.
Researchers active (performing part of the work plan) benefit from meetings and professional exchange during the term of the task. Countries participating in the task benefit from the information developed by the task.
Participants can gain access to the Members Only portion of the website from the Operating Agent, Niina Helistö.
For more information, contact the Operating Agents (contact information below) or the IEA Wind TCP Secretariat.
Operating Agents
Please contact the Operating Agents below with any questions
Task 25/63 Publications
Find more information about our publications and results here
See also Task 25/63 in Zotero
Task 25/63 Roadmap
Task 25, Phase l
State-of-the art Comparison of studies
Task 25, Phase ll
Best practice of Methodology and Experience
Task 25, Phase lll
Recommended Practices RP16
Fact sheets
Hourly time series, smoothing impact
Higher share studies
Task 25, Phase lV
Wind/PV
RP Ed.2
Energy System Coupling
Task 25, Phase V
Instant 100% wind&solar challenges in Energy Systems
Task 25, Phase Vl
100% wind&solar events with Smart Energy Integration
Task 25/63, Phase l
Any Question at
Tel: +358 40 5187955
Recognis Oy w. VTT
VTT Technical Research Centre Ltd
Tekniikantie 21, Espoo
Finland
Monday to Friday
9 am – 17 pm Central European Time
Send your mail at
hannele.holttinen
@recognis.fi
niina.helisto
@vtt.fi















