Dear Colleagues,

We invite you to contribute original manuscripts to the special issue of Sustainability on “Power System Flexibility in High Renewable Energy Systems”.

A broad range of economic, environmental, technical, and socio-political forces have driven the deployment of renewable energy to unprecedented levels in many countries and regions. In the past two years, the United States, Germany, and China installed more new wind and solar capacity than all new conventional capacities combined. As of February 2019, the United Kingdom, Denmark, Sweden, Switzerland, and nine U.S. states (district and territory) have committed to 100 percent renewable or zero-carbon electricity. Many countries are already operating the grid at high penetration of renewable energy. For example, Scotland met 88% of its demand with renewables in the first quarter of 2019; similar or higher percentages have been observed during certain periods in Germany and Denmark.

Such high renewable penetration challenges the flexibility of the electric power system – often defined as the ability to cope with variability and uncertainty. While a rich body of literature exist on flexibility strategies such as using grid extension, thermal storage, electric storage, and demand side management, implementation of these strategies in large-scale systems still face operational, regulatory, economic, and market barriers. Moreover, meeting the flexibility challenges of high penetration renewable systems may be facilitated by appropriately designed and operated cross-sector solutions such as the electrification of the end- use sectors, particularly transportation, and power-to-gas or to-hydrogen development. These trends call for an interdisciplinary approach to investigate the flexibility topic.

This special issue in Sustainability will cover this promising and dynamic area of research and development, and emphasize the broad array of considerations and state-of-art approaches in effectively planning and managing bulk power systems with high variable renewable energy as the foundation for broader clean energy economies.

The topics of interest include, but are not limited to:

Transmission-level integration study of renewable energy considering flexibility, e.g. methodology and tools for transmission planning, interconnection studies, unit commitment and production cost studies, flexibility planning methods and tools.

Market design, market integration, and real-time market simulation of renewable energy and flexibility-enabling technologies, including pumped hydro, electric storage, demand response, electric vehicles, power-to-hydrogen.

Inter-disciplinary study of power system flexibility coupled with the transportation, building, agricultural, or other sectors.

Technical, economic, regulatory, and policy aspects of flexibility implementation in large-scale power systems with high penetration renewable energy and associated broader energy sectors.

Case studies of country- or regional- scale implementation of measures to enhance power system flexibility in high renewable energy systems.

Advanced coordination and management of grid operations considering flexibility-enabling resources.

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• Renewable energy systems
• Cross Sector Coupling
• Power system flexibility
• Renewable integration
• Power system planning
• Power system operation
• Power market design