Use Case 1: RESTORE Integration

At the Brønderslev hybrid district-energy plant in Northern Jutland, the RESTORE system is virtually integrated to capture and store solar heat that would otherwise go unused. The site already combines a 16.6 MWₜₕ parabolic-trough collector (PTC) field with high-efficiency biomass boilers and a 3.9 MWₑₗ Organic Rankine Cycle (ORC), supplying heat and power to a 160 km district-heating network with ~4,800 customers. While biomass heat is fully utilized, solar production can exceed immediate needs—especially in summer—creating an opportunity for seasonal, dispatchable storage.

The virtual pilot integrats a specifically optimized RESTORE energy storage unit. The existing parabolic trough solar collector field can then charge the TCES system during summer months. Residual heat from industry or excess low-temperature heat from solar collectors in the district is used to efficiently store off-peak cheap electricity.

uc1 restore proposed solution 

RESTORE proposed solution Brønderslev

The RESTORE system connects exclusively to the solar thermal loop (thermal oil at ~150–270 °C). When district-heating demand or ORC inlet conditions limit direct solar use, surplus heat is diverted to the TCES charging reactor. The storage medium is copper-sulfate hydrate (CuSO₄·5H₂O), which stores energy via reversible dehydration/hydration reactions. Charged material is held in sealed vessels for hours to months without losses associated with sensible heat tanks.

Operation

Charging (solar-rich periods): Hot oil from the PTC field drives an endothermic dehydration in a continuously stirred reactor, converting the hydrate to lower-hydrate/anhydrous forms and locking in solar energy chemically.

Discharging (on demand): The material is rehydrated in a dedicated reactor, releasing heat exothermically. That heat is routed either to the ORC (for electricity generation) and/or directly to the district-heating heat exchanger, depending on system needs. The TCES loop operates as a standalone, dispatchable module, without altering biomass or heat-pump operation.

Why here?

In 2020 the solar field delivered 11.3 GWhₜₕ (≈9.5% of Brønderslev’s heat), yet seasonal demand swings and operational constraints mean not all potential solar heat can be valorized in real time. The central plant already has an 8,000 m³ hot-water tank for short-term balancing; TCES complements this by enabling medium-to-long-duration (seasonal) shifting at higher temperature levels and without standby losses.

Benefits

  • Higher solar utilization: Converts curtailed/unused solar output into useful heat and power later.
  • Seasonal flexibility & resilience: Decouples solar availability from demand and electricity-price signals.
  • No impact on biomass performance: Integration is solar-side only; biomass remains the primary dispatchable heat source.
  • System efficiency & value: Heat can feed the ORC and/or district heating, maximizing energy valorization across operating modes.
  • Scalable concept: Uses commercially available components (PTC field, ORC) with a thermochemical storage add-on tailored to medium-temperature solar heat.