Background: Research & Innovation (R&I) in Concentrating Solar Thermal (CST) technologies promises global impacts through new and sustainable solutions to societal challenges. CST technologies include 1) Solar Thermal Electricity (STE/CSP), 2) Solar Heat for Industrial Processes (SHIP), 3) Solar Fuels, and 4) Clean and Fresh Water. Europe is currently a global technology leader in CST, and SolarTwins is designed to strengthen this leadership position. SolarTwins builds on several EU CST R&I networks and activities including EU-SOLARIS, HORIZON-STE, SFERA-III, and INSHIP.Goal: The Goal of SolarTwins is to Step-Up the Scientific Excellence and Innovation Capacity of the Promising Institution METU-GÜNAM's CST research laboratory through Twinning with the Leading Institutions CIEMAT-PSA (Spain) and DLR (Germany). SolarTwins is specifically formulated to lead to Joint Research Proposals that target large joint funding opportunities to increase competitive research funds to all partners, and result in more effective use of public research funds.Project: SolarTwins contains 3 Twinning Work Packages (WPs 1-3). WP1 contains cross-cutting activities including Joint Kick-Off Activities targeting Key Stakeholders, and External Training to strengthen local, regional and national R&I capacities. WP2 is dedicated to Early Stage Researchers (ESRs) and contains 2 summer schools at METU taught by experts from CIEMAT-PSA and DLR, and exchange of METU ESRs to CIEMAT-PSA and DLR for training and research mentoring. WP3 is dedicated to developing joint research lines between METU-GÜNAM and each of CIEMAT-PSA and DLR. WP3 includes activities for METU-GÜNAM personnel at each of CIEMAT- PSA and DLR to formulate joint research lines, and METU-GÜNAM staff exchange to each of CIEMAT-PSA and DLR to develop joint research proposals. WP4 is dedicated to maximising the Impacts of SolarTwins and includes Communication, Dissemination, and Exploitation tasks, and a Final Conference.