RockStore: accessible and cost-effective thermal energy storage

Introduction

This project demonstrates the commercialisation of ‘Rockstore’, a granite-based thermal energy storage solution with the ability to store thermal energy at around 300°C. This demonstration will show that bridging the supply and demand gaps in renewable energy production and consumption provides a substantial emission avoidance. It will also demonstrate a 100% relative Greenhouse Gas (GHG) avoidance compared to the reference scenario.

Key Innovation

The key innovation of Rockstore is the provision of heat storage in the ideal range between:

• Cold storage solutions (<100°C) which are too cold for combined heat and power production
• Superhot air storage solutions (>500°C), which are too hot for conventional Combined Heat and Power (CHP) equipment

This sweet spot between the two will make it commercially available to district heating plants connected to an electricity grid with a high intermittent renewable energy mix, which is applicable to many Danish and European cities.

Technical Capabilities

Rockstore possesses the capability to deliver electricity rapidly and can offer power backup for several hours by using granite rocks in large steel tanks to store heat up to 330°C.

Charging and Discharging

Rockstore tanks are charged and discharged by using an eco-friendly oil that interfaces with the user’s heat systems through a standard heat exchanger. The system allows for an increase in capacity, displaying the ability to store and release thermal and electrical energy at a lower cost compared to existing technologies, thus facilitating greater integration of renewable energy sources.

Contribution to Energy Goals

Rockstore’s ability to charge with excess electricity and deliver heat and stored power independently from wind and solar production, particularly during periods of high energy demand, will aid European Union member states in meeting their 2050 and 2030 targets outlined in the European Climate Law.

Alignment with European Initiatives

Additionally, this technology contributes to the objectives of the European Green Deal by helping ensure affordable and consistent energy prices. By enabling a higher energy security in an electricity grid with a high mixture of renewables, the EU will be less reliant on imports of natural gas, which is a target stated in the REPowerEU initiative.

Project Goals

RockStore will produce heat to an existing 3rd party district heating grid, proving that renewable electrified heat production can be obtained at a low, stable price.

Energy Production Targets

The project also aims to displace total energy production of the system to 15.5 GWh thermal and storing heat exceeding 100°C, without putting stress on the electrical grid during peak periods in the demand curve, and paving the way for future projects.