From concept to bankability: how to de-risk thermal energy storage for solar systems in HORIZON-CL5-2026-02-D3-05
1st December 2025 at 12:34 pm
Thermal energy storage (TES) is becoming essential for Europe’s renewable energy resilience. As solar deployment accelerates, dispatchability remains a key challenge for energy providers and grid operators. The Innovation Action (IA) call HORIZON-CL5-2026-02-D3-05 supports large-scale demonstration of innovative TES solutions for concentrated solar power (CSP) and solar thermal heat and/or cold. The call also contributes directly to the execution of the solar thermal implementation plan under the Strategic Energy Technology Plan (SET Plan) and supports the solar energy joint research and innovation agenda, strengthening the EU’s long-term solar deployment strategy. With a budget of € 15.00 million for two projects and a deadline on 17 February 2026, the call emphasises bankability, cost reduction, improved performance and sustainability, requiring applicants to deliver demonstrations that significantly outperform the state of the art. Below, we outline what strong proposals must deliver to meet the expectations of the European Commission (EC).
1. Demonstrating TES performance improvements: beyond incremental innovation
The EC expects substantial advances in performance, cost-effectiveness and lifespan compared to existing TES technologies. Demonstrations should clearly validate thermal efficiency, storage capacity, cycling durability and integration reliability.
• Benchmark your solution against state-of-the-art TES systems.
• Quantify expected improvements in cycle stability, storage density and thermal losses.
• Present credible pathways to reducing Levelised Cost of Heat Storage (LCOHS) or Levelised Cost of Energy (LCOE).
• Use real operational conditions to demonstrate durability and reliability.
2. From engineering design to go/no-go readiness: a critical milestone for 2026
One of the strongest requirements of this call is a clear go/no-go milestone before entering the demonstration phase. By this milestone, the project must deliver detailed engineering plans, a techno-economic assessment and all necessary permits.
• Provide a realistic and well-structured permitting plan.
• Offer detailed engineering documentation demonstrating technology readiness.
• Include risk assessment criteria directly linked to the go/no-go decision.
• Present a viable timeline for permits, engineering validation and site preparation.
3. Improving dispatchability and reducing curtailment: TES as a system enabler
TES has system-wide impacts. The EC wants solutions that improve solar dispatchability, allow flexible operation and reduce curtailment, which are benefits that directly support electricity grid operators.
• Quantify improvements in dispatchability and flexibility.
• Illustrate reductions in curtailment through system modelling.
• Show how TES integrates with CSP, industrial heat, district heating or cooling.
• Use system-level analysis to demonstrate benefits for grid operators and energy providers.
4. Bankability and financing: demonstrating a credible investment case
Projects should strengthen financing pathways to improve investor confidence and enable access to sources such as the Innovation Fund.
• Provide cost analyses including CAPEX, OPEX, IRR and sensitivity scenarios.
• Outline how the demonstration de-risks the technology for investors.
• Engage financial or industrial partners early to validate bankability claims.
• Clarify the business model and potential commercialisation routes.
5. Sustainability and Safe and Sustainable by Design: essential for TES materials
The EC requires a comprehensive sustainability assessment covering environmental and socio-economic aspects, aligned with the Safe and Sustainable by Design (SSbD) framework for materials and chemicals.
• Conduct a lifecycle assessment (LCA) to assess environmental impacts across the value chain.
• Include socio-economic indicators such as job effects or community benefits.
• Apply SSbD principles to material selection, safety and lifecycle planning.
• Integrate circularity approaches, including recyclability of storage media.
6. Strong exploitation and deployment strategy: planning beyond the demonstration
Proposals need to outline scalability, commercialisation pathways and identification of future funding sources.
• Define target markets and deployment pathways for your TES solution.
• Present a realistic plan for scaling manufacturing or implementation.
• Align exploitation strategies with Innovation Fund or national funding opportunities.
• Clarify IP management and strategies to support market uptake.
Looking for support in preparing your thermal storage proposal?
At accelopment, we have a strong track record in supporting Horizon Europe projects that advance renewable energy integration, system flexibility and large-scale demonstration. Our collaboration in H-DisNet and HEAT-INSYDE highlights our experience with thermal networks, intelligent heat storage and the optimisation of decentralised energy infrastructures. Through projects such as PEPPERONI and SOLARX, we also contribute to accelerating innovative solar technologies and strengthening Europe’s clean energy manufacturing capacity. Together, these initiatives reflect our commitment to enabling solutions that improve energy system resilience, enhance technology readiness and support commercial deployment. With our expertise in proposal writing, consortium coordination and impact-focused communication, we help research teams prepare competitive and strategically aligned applications under Horizon Europe’s Cluster 5.
Dr. Johannes Ripperger
Research & Innovation Manager
Andreia Cruz
Research & Innovation Project Manager