Underground Thermal Energy Storage in dense urban areas

This summary outlines the Horizon Europe call HORIZON-CL5-2026-02-D3-22, which focuses on Underground Thermal Energy Storage (UTES) in dense urban areas. The program emphasizes the development and implementation of innovative technologies to enhance energy storage systems, contributing to decarbonization efforts in urban settings while ensuring community engagement.

Eligible applicants include research institutes, universities, small and medium-sized enterprises, large enterprises, and public-private partnerships based in EU and European Economic Area countries. The funding is categorized as a grant, specifically a Horizon Lump Sum Grant, with financial support exceeding 5 million euros per project, aiming for an expected budget of 18 million euros for the call. The application process is an open call with a single-stage submission.

Projects are encouraged to focus on development, validation, and demonstration stages, addressing various aspects of energy storage, including integration with existing energy grids and urban infrastructure. Specific technologies targeted encompass various forms of thermal energy storage systems, such as Aquifer Thermal Energy Storage and Borehole Thermal Energy Storage.

Key expected outcomes from funded projects include advancing knowledge in energy storage technologies, improving the security of renewable energy systems, decreasing the levelized cost of heat storage, and fostering community participation in the innovation process. Proposals should consider subsurface urban heat dynamics, regulation frameworks, and strategies for effective land use.

The call opens on September 16, 2025, and submissions are due by February 17, 2026. The expected success rates align with typical Horizon Europe program rates, often ranging from 10% to 39%. Co-funding for projects is generally a requirement under this program.

Overall, the initiative aims to foster interdisciplinary collaborations that enhance societal impacts and tackle both technical and regulatory challenges associated with underground thermal energy solutions in urban environments. Applicants are encouraged to utilize open datasets and adhere to established data quality standards, engaging local communities and stakeholders throughout the research and development phases.

This is a Horizon Europe (HORIZON) call, specifically Cluster 5 Call 02-2026 (WP 2025) (HORIZON-CL5-2026-02), focusing on Underground Thermal Energy Storage in dense urban areas, with the topic code HORIZON-CL5-2026-02-D3-22. It is a HORIZON Innovation Action (HORIZON-IA) with a HORIZON Lump Sum Grant [HORIZON-AG-LS] type of Model Grant Agreement (MGA). The deadline model is single-stage. The planned opening date is 16 September 2025, and the deadline date is 17 February 2026 at 17:00:00 Brussels time.

The expected outcomes of the projects are: Advanced European innovative knowledge base and increased technology competitiveness in the area thermal storage; Improved security of the future European renewable-based energy system; Contribution to the decarbonisation of cities and densely populated urban areas with high safety solutions; Significant reduction of LCOHS (Levelised Cost of Heat Storage); Local communities are engaged and their expectations are responded to; Technology developers practice inclusive societal engagement which is early, continuous, and sensitive to the technical specificities (e.g. local resource, subsurface uncertainties) and social challenges (e.g. low public awareness) of underground thermal energy storage technologies in the context of densely populated urban areas.

The scope includes novel technologies, interfaces, design methods, and organizational concepts for effective and sustainable use of subsurface space in dense urban areas using Underground Thermal Energy Storage (UTES) systems like ATES, CTES, and BTES. Proposals should consider integration with existing energy grids and other urban subsurface uses (e.g., subways, utilities, buildings), including energy geostructures, tunnels, slabs, and energy sheet pile walls, with potential geothermal heating, cooling, and storage opportunities. Proposals should address uncertainties in seasonal energy demand to increase predictability of subsurface space and thermal efficiency.

Projects are expected to deploy one or more demonstrators and can address areas such as: Optimal utilization of geothermal resources and thermal energy storage in urban settings, addressing high (above 70 degrees Celsius), medium (30-70 degrees Celsius) and/or low temperatures (10-30 degrees Celsius) and possible requirements for retrofitting of the building stock; Subsurface models for sustainable underground thermal storage and geothermal use in cities; The integration of heat pumps, advanced thermal storage, and interface with district heating infrastructures to contribute to the thermal and power grid flexibility; Studying the impact of subsurface urban heat islands (SUHI) on the potential of shallow geothermal energy use in cities, using, for instance, long-term subsurface monitoring networks, satellite monitoring and models; Best practices strategies for subsurface land-use plans in European cities; well/borehole placement strategies; Mutual interaction of existing and future neighboring UTES systems from geotechnical, energy, and regulatory point of view; Management of energy grids on an urban scale and system optimisation thorough digital twins predicting operational, environmental and economic response, as well as the interaction between the storage system and the local grids, under different scenarios; Creation of large (time and scale-wise) open multisensory datasets to foster heat energy storage at the European scale which should adhere to the FAIR data principles, adopt data quality standards, data integration operating procedures and GDPR-compliant data sharing/access good practices developed by the European research infrastructures, where relevant. Use of advanced monitoring systems such as fibre optic sensors, satellite imagery, etc. for monitoring and early detection of adverse impact of UTES at a district scale level and providing measures to mitigate such effects.

Consideration should be given to de-risking solutions and support schemes for innovative energy storage technologies. The consortium should assess the current regulatory context and provide recommendations for shaping future needs (e.g., regulatory, standardisation, permitting). Local community engagement initiatives and expectations of underground thermal storage infrastructures should be explored.

This topic requires citizens engagement and dialogue and the effective contribution of SSH disciplines and the involvement of SSH experts, institutions as well as the inclusion of relevant SSH expertise, in order to produce meaningful and significant effects enhancing the societal impact of the related research activities and ensure the translation of innovation into real-life outputs.

General conditions for admissibility, eligible countries, financial and operational capacity, evaluation, award, and legal/financial setup are described in the annexes of the Horizon Europe Work Programme and the Online Manual. Eligible costs will take the form of a lump sum as defined in the Decision of 7 July 2021 authorising the use of lump sum contributions under the Horizon Europe Programme.

Application and evaluation forms, model grant agreements, guidance documents, and additional resources such as the Horizon Europe Work Programme, Framework Programme, Specific Programme Decision, EU Financial Regulation, and Funding & Tenders Portal manuals are available on the Funding & Tenders Portal.

The budget overview for the call in 2025 includes various topics with different budget allocations and indicative numbers of grants. For HORIZON-CL5-2026-02-D3-01, the budget is 33,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D3-02, the budget is 8,000,000 EUR with around 2 grants. For HORIZON-CL5-2026-02-D3-05, the budget is 15,000,000 EUR with around 2 grants. For HORIZON-CL5-2026-02-D3-07, the budget is 15,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D3-08, the budget is 15,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D3-10, the budget is 24,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D3-12, the budget is 8,000,000 EUR with around 2 grants. For HORIZON-CL5-2026-02-D3-13, the budget is 20,000,000 EUR with around 1 grant. For HORIZON-CL5-2026-02-D3-14, the budget is 6,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D3-18, the budget is 18,000,000 EUR with around 2 grants. For HORIZON-CL5-2026-02-D3-19, the budget is 16,000,000 EUR with around 2 grants. For HORIZON-CL5-2026-02-D3-20, the budget is 20,000,000 EUR with around 2 grants. For HORIZON-CL5-2026-02-D3-22, the budget is 18,000,000 EUR with around 2 grants. For HORIZON-CL5-2026-02-D3-24, the budget is 18,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D4-01, the budget is 15,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D4-02, the budget is 12,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D4-03, the budget is 15,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D4-04, the budget is 15,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D4-05, the budget is 12,000,000 EUR with around 3 grants. For HORIZON-CL5-2026-02-D4-06, the budget is 15,000,000 EUR with around 2 grants.

Partner search announcements are available for users with active profiles on the Funding & Tenders Portal.

This Horizon Europe call aims to foster innovation and research in underground thermal energy storage within dense urban environments. It seeks to improve the efficiency, sustainability, and integration of UTES systems, contributing to decarbonization goals and enhancing the security of renewable energy systems. The call encourages projects that deploy demonstrators, engage local communities, and address regulatory and societal aspects of UTES technologies. The funding is provided as a lump sum, and the call is open to a wide range of participants, including research organizations, businesses, and public authorities, with a focus on collaborative projects that involve interdisciplinary expertise and citizen engagement.

Eligible Applicant Types: The eligible applicant types are not explicitly stated in the provided text. However, given that the funding is part of Horizon Europe and includes Research and Innovation Actions (RIA), Innovation Actions (IA), Pre-commercial Procurement (PCP), and Coordination and Support Actions (CSA), the eligible applicants could include universities, research institutes, SMEs, large enterprises, and other organizations capable of conducting research and innovation activities. The mention of LEAR (Legal Entity Appointed Representative) also suggests that any legal entity validated by the EU is eligible.

Funding Type: The primary financial mechanism is a grant, specifically a HORIZON Lump Sum Grant, as indicated by the "Type of MGA: HORIZON Lump Sum Grant [HORIZON-AG-LS]" designation. There are also Pre-commercial Procurement actions.

Consortium Requirement: The text does not explicitly state whether a single applicant or a consortium is required. However, the presence of a "Partner Search" section and the nature of the projects suggest that consortia are likely preferred, if not required, especially for Innovation Actions and Research and Innovation Actions.

Beneficiary Scope (Geographic Eligibility): The eligible countries are described in Annex B of the Work Programme General Annexes. The text also mentions that "A number of non-EU/non-Associated Countries that are not automatically eligible for funding have made specific provisions for making funding available for their participants in Horizon Europe projects," suggesting that the primary geographic eligibility is EU and associated countries, with possibilities for third-country participation under specific conditions.

Target Sector: The program targets the energy sector, specifically focusing on Underground Thermal Energy Storage (UTES) systems in dense urban areas. This includes technologies like ATES (Aquifer Thermal Energy Storage), CTES (Cavern Thermal Energy Storage), and BTES (Borehole Thermal Energy Storage). The program also touches on climate, energy, mobility, and urban development.

Mentioned Countries: The text does not explicitly mention any specific countries. However, it refers to "EU and non-Associated Countries" and "third-countries," indicating a focus on the European Union and associated countries, with some provisions for other countries.

Project Stage: The project stages vary depending on the type of action. Research and Innovation Actions (RIA) focus on research and development, while Innovation Actions (IA) focus on demonstration and deployment. Pre-commercial Procurement (PCP) focuses on the procurement of research and development services. The call encourages projects to deploy demonstrators, suggesting a focus on validation and demonstration stages.

Funding Amount: The funding amounts vary widely depending on the specific topic. The budget overview lists topics with budgets ranging from €6,000,000 to €33,000,000. The indicative number of grants per topic ranges from 1 to 3. Therefore, the funding range is variable, from under €5M to over €5M depending on the action.

Application Type: The application type is an open call, with a single-stage submission process.

Nature of Support: The beneficiaries will receive money in the form of a lump sum grant.

Application Stages: The application process is single-stage.

Success Rates: The success rates are not explicitly mentioned.

Co-funding Requirement: The text does not explicitly mention a co-funding requirement. However, given that these are Innovation Actions and Research and Innovation Actions, co-funding may be required, especially for Innovation Actions which are closer to market.

Summary:

This Horizon Europe Cluster 5 call focuses on "Underground Thermal Energy Storage in dense urban areas." The call aims to advance European innovative knowledge, improve energy security, decarbonize cities, reduce the cost of heat storage, and engage local communities. The scope includes novel technologies, interfaces, design methods, and organizational concepts for UTES systems like ATES, CTES, and BTES. Projects should consider integrating with existing energy grids and other urban subsurface uses. The call encourages the deployment of demonstrators and addresses various aspects such as geothermal resource utilization, subsurface modeling, integration of heat pumps, impact of subsurface urban heat islands, best practices for subsurface land-use plans, management of energy grids, and creation of open multisensory datasets. The call also emphasizes de-risking solutions, regulatory context assessment, and community engagement. The eligible applicants can include universities, research institutes, SMEs, and large enterprises. The funding type is primarily a lump sum grant, and the application process is a single-stage open call. The geographic eligibility is mainly EU and associated countries, with some provisions for third-country participation. The call includes various types of actions, such as Innovation Actions (IA), Research and Innovation Actions (RIA), Pre-commercial Procurement (PCP), and Coordination and Support Actions (CSA), each with different funding amounts and objectives. The call opens on 16 September 2025 and closes on 17 February 2026.