Renewable Energy based seasonal Storage Technology in Order to Raise Economic and environmental sustainability of DHC

Project Information

RESTORE

Grant agreement ID: 101036766

DOI

10.3030/101036766

Project closed

EC signature date 30 August 2021

Start date 1 October 2021

End date 30 September 2025

Funded under

• SOCIETAL CHALLENGES - Secure, clean and efficient energy

Total cost

€ 5 667 736,25

EU contribution

€ 5 667 736,25

Coordinated by

FUNDACION CENER
Spain

Periodic Reporting for period 3 - RESTORE (Renewable Energy based seasonal Storage Technology in Order to Raise Economic and environmental sustainability of DHC)

Reporting period: 2024-10-01 to 2025-09-30

Summary of the context and overall objectives of the project

The project proposes an innovative solution to decarbonise the heating and cooling sector and support climate-change mitigation. The concept is based on combining two key technologies that enable the integration of diverse Renewable Energy Sources (RES) and industrial waste heat, together with seasonal storage, into District Heating and Cooling (DHC) networks to enhance their environmental sustainability.
The first technology developed in the project is an advanced Thermochemical Energy Storage (TCES) system, which stores heat through reversible chemical reactions. Owing to its high energy density and minimal thermal losses, TCES enables both daily and seasonal storage, addressing the mismatch between energy demand and energy generation from intermittent renewable sources or waste heat, particularly across seasons.
The second technology is a reversible Heat Pump (HP) / Organic Rankine Cycle (ORC), designed to be coupled with the TCES unit. This system adapts energy from various RES and waste-heat sources to charge the storage system efficiently. Its integration allows the entire solution to handle a broad spectrum of renewable and waste-heat inputs and deliver energy according to the specific operating conditions of each DHC network.
This innovative combined system addresses key barriers that currently limit the large-scale deployment of renewable energy and waste heat in existing and future DHC infrastructures. The project includes the experimental validation of the RESTORE concept, as well as an assessment of its replicability through virtual use-cases reflecting different real network configurations, available renewable technologies, and local boundary conditions across the EU.
Conclusions of the action: The project successfully completed a laboratory-scale validation of the integrated TCES and reversible HP/ORC system, demonstrating its technical feasibility under controlled operating conditions and achieving TRL 4. The experiments confirmed the high-density storage capability, low losses, and stable cyclic behaviour of the TCES reactor, together with the reliable operation of the reversible HP/ORC unit. These results provide strong evidence of the robustness of the proposed concept and its potential for further development. Regarding the virtual use-cases, the analysis shows that the competitiveness of the RESTORE concept is maximised in scenarios with favourable conditions for its integration, particularly where nearby consumers can effectively use the excess heat supplied by the system.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The project defined the overall requirements of the RESTORE concept, including specifications for the reversible ORC prototype, the scaled TCES reactors, and the numerical models used in simulations and virtual use-cases. Continuous monitoring, risk analysis, and environmental, social, and economic assessments supported proper implementation.
In thermochemical storage, conducted experimental campaigns on several materials, developed a small continuous reactor, tested a 5 kW intermediate reactor, and built and validated a 30 kW unit. These steps enabled system optimisation and scale-up. Thermodynamic cycle models were developed, and simulations were carried out for small- and large-scale organic cycles, including off-design analysis.
A reversible ORC prototype was designed, manufactured, and tested, followed by modifications to improve performance. Additional models were created for the RESTORE library, and an online simulation platform was developed and populated with six virtual use-cases, showing competitiveness where integration conditions are favourable.
Moreover, several models have been developed in the RESTORE library. A web platform for simulating cases online has been developed, tested and optimized. Six different virtual use-cases have been implemented in the platform, to analyze the impact of the RESTORE solution in different scenarios. The results suggest that the system is competitive in those scenarios that present good conditions for the integration of the system.
Exploitation activities produced the final strategy, roadmap, Key Exploitable Results, and technology watch document, covering relevant patents, competing technologies, and regulatory requirements. The advisory board and stakeholder network were expanded.
Regarding dissemination and communication, the final plan was delivered, the website and social media were regularly updated, and several videos, workshops, and webinars were released. Partners attended EU and international events and contributed multiple open-access scientific publications.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

RESTORE project proposes to develop a technical solution able to overcome the current technological barriers that limit the penetration of RES in the DHC sector. Proposed technology allows to significantly increase the RES share and the reuse of energy waste from industry in DHC networks improving their competitiveness and environmental sustainability and promoting the involvement of stakeholder, consumers and industries eventually meeting the targets of the EU strategy for Heating and Cooling and the EU’s climate and energy goals.
The restore concept, named as Pumped Thermal Storage (PTS) is based on the combination of two innovative technologies: a Thermo-Chemical Energy Storage (TCES) and a non- conventional power system based on Heat Pumps and Organic Rankine Cycles (HP/ORC).
● A competitive solution for energy storage to tackle mismatch between energy demand and energy availability from renewable technologies or waste excess heat on seasonal base. RESTORE adopts high energy density TC storage which allows dispatching large amounts of thermal energy from summer to winter by means of storing solids at ambient temperature with no heat losses and low investment cost. The expected outcome is to nearly double the amount of energy provided for district heating with the same RES availability with market positive effects on equipment capacity factors and system economics.
● A combination of different RES and WEH maximizing synergies to supply the energy demand. RESTORE adopts a non-conventional power cycle based on pumped heat concept for charging and discharging the TCES able to integrate any kind of available RES (both electrical and thermal based) and WEH, limiting the waste of useful energy during hot season, and thus improving current and future DHC networks environmental sustainability, facilitating the integration of energy sources non-based on the use of-fossil fuels.
The project plans to demonstrate the technology at lab scale, carried out its assessment in environmental, economic and social aspects as well as develop a simulation platform where 6 different use cases will be implemented and simulation in order to study and analyze the impact of the RESTORE solution under several scenarios.

RESTORE technology in a nutshell

Overall RESTORE concept overview