Thermal storage uses heat to store energy so that when demand peaks, the heat can produce electricity directly by initialising a steam turbine. There are different ways to store this energy. One is to use large-scale volcanic rocks that can contain a large amount of heat. This solution allows the energy to be held for up to one week, and therefore assists with adequacy and sometimes congestion management. Another way is to store heated fluids in insulated tanks. This storage system can respond very quickly, and can provide anything from short term frequency response up to longer cycles over several days. It there-fore helps with frequency balancing, adequacy and congestion management. Moreover, district heating and cooling is an energy solution for satisfying urban heat and cooling demand. District energy systems which pipe steam, and hot or cold water, around a district from a central location are being used in a variety of cities worldwide because of their higher energy efficiency, which can significantly reduce the greenhouse gas emissions of cooling and heating.
Components & enablers
- Highly flexible digital control system platforms for virtual power plants that enable renewable energy to be stored optimally.
State of the art in application and research
A pilot plant in Hamburg can store 130 MWh for up to one week, and has a goal of reaching over 1 GWh in the near future. The heat storage facility contains approximately 1,000 tons of volcanic rock as an energy storage medium. It is fed with electrical energy converted into hot air by means of a resistance heater and a blower that heats the rock to 750 °C. EnergyNest are looking at a faster storage solution. The thermal storage unit could be used for thermal power plants by directly being integrated into existing steam cycles, effectively providing a steam storage buffer between the boiler and the turbine.
This allows plant operators to run their boiler continuously while boosting or reducing the electric output on demand. Depending on the case, the system reaction time for EnergyNest can be less than 7 seconds. This means it is a solution for providing thermal power plants with the flexibility required to provide primary frequency response. It can be designed to provide a short or long response time, depending on what provides most value in electricity markets. It can also provide both adequacy and congestion management.
In EnergyNest, heat at high temperature is transferred to the thermal storage device using a heat transfer fluid (HTF) inside pipes cast into the thermal storage elements. There is no direct contact between the HTF and storage material, and the thermal elements with steel piping are compatible with common HTFs such as thermal oil, water / steam or compressed gas etc.
Eco-Stock is a heat storage made from refractory ceramics and works by heating the ceramics directly via hot fumes from the chimney.
E2District is a three year European Commission Horizon 2020 Research and Innovation project formally entitled ‘Energy Efficient Optimised District Heating and Cooling (DHC)’.
In NETfficient, UC 5, the storage system is thermal and split into a day and a night deposit. The temperature of the Thermal Storage System is regulated by two cooling / heating units.
In PUMPHEAT, WP3, advanced solutions for warm / cold storage are proposed.
The REACT project deploys high-capacity and environmental friendly conventional batteries and power-to-gas solutions, such as innovative heat pumps.
REnnovates proposes a compact energy module installed near a house which includes a heat pump and a hot water boiler; the aim is to significantly extend the life of such homes and improve the energy efficiency to such an extent that a ‘zero on the meter’ scenario is possible.
In the SENSIBLE demo in Nuremburg, Germany the integration of electrical and thermal storage together with heat pumps, CHP and different energy vectors is done by means of a Building Energy Management System that minimises the building’s energy procurement costs.
Based on the results of the preliminary research project ‘StoreITup-IF!’, polymer-based-PCM storages are constructed and tested in laboratory and operational environment. The storages are expected to be industrially producable and economically viable (< 50 € / kWh).
In the STORY project, system thermal energy storage based on hot water storage tanks is considered. The innovative aspects of the Beneens demo in the STORY project are:
› Efficiency enhancement and active control of ORC through the use of thermal storage.
› State of charge estimation of thermal energy storage with limited sensors.
› Potential optimisation of the thermal grid through double use in intervals.
Furthermore, in Lecale, Northern Ireland, the STORY demonstration unit takes electricity from the grid to drive a compressor for storing com-pressed air in air storage cylinders. It is the first time such a system has been tested outside of a lab environment. The heat released in this process is recovered and stored in molten salt tanks.
In WiseGRID, the integration of the renewable energy storage systems in the network, such as heat accumulators, is tested. Similar pilots are the Lisboa-Portugal pilot of the InteGRIDy project and the Samsø-Denmark pilot of the SMILE project.
The energy storage projects in the Canary Islands serve as tools for the system operator to guarantee supply, improve system security and optimise the integration of renewable energy in the Canary Islands. The construction of the pumped-storage hydropower station between the Soria and Chira reservoirs, which responds to these objectives, will be an essential element to progress towards the sustainability of the new energy model in the Canary Islands.
A pilot plant in Hamburg can store 130 MWh for up to one week and has a goal of reaching over 1 GWh in the near future. The heat storage facility contains approximately 1,000 tons of volcanic rock as an energy storage medium. It is fed with electrical energy converted into hot air by means of a resistance heater and a blower that heats the rock to 750 °C. EnergyNest are investigating a faster storage solution. The thermal storage unit could be used for thermal power plants by directly being integrated into existing steam cycles, effectively providing a steam storage buffer between the boiler and the turbine. This allows plant operators to run their boiler continuously while boosting or reducing the electric output on demand. Depending on the case, the system reaction time for EnergyNest can be less than 7 seconds. This means it is a solution for providing thermal power plants with the flexibility required to provide primary frequency response.
Technology Readiness Level
Large-scale volcanic rock: TRL 7 – Demonstration
New 4.0 has a pilot plant in Hamburg that can store 130 MWh for up to one week; the next step is to use its storage technology in commercial pro-jects and scale up the storage capacity and power to reach the goal of over 1 GWh in the near future.
Heated fluid in insulated containers: TRL 9 – Implementation
EnergyNest and Eco-stock are already commercial.
Current focus of R&D and research gaps
See State of the Art.
 New 4.0: Simens Gamesa [Link]
 EnergyNest [Link]
 Eco-Stock [Link]
 STORY – pilot 6 [Link]
 E2District [Link]
 InteGRIDy [Link]
 NETfficient, UC 5 [Link]
 PUMPHEAT [Link]
 REACT [Link]
 REnnovates [Link]
 SENSIBLE [Link]
 SMILE [Link]
 StoreITup-IF [Link]
 STORENET [Link]
 STORY [Link]
 WiseGRID [Link]
 Energy Storage in the Canary Islands [Link]