Electro-Thermal Energy Storage for Sector CouplingCopyright: © MAN ES
Decarbonization of the heating sector is imperative for effective reduction of CO2 emissions. As of today, heating accounts for around 50 % of the worldwide carbon dioxide emissions and only a small share of renewable energy is used. A prospective technology for the thermodynamically efficient use of renewably generated electricity to produce heat are heat pumps. This technology provides a manifold of the invested electrical energy in the form of usable heat. Although this technology is successively used for heating purposes in the residential sector, so far other sectors still lack the application of such technologies. However, high-temperature heat pumps would enable new and previously untapped possibilities for integrating renewable electrical energy into other areas such as industrial heating.
The good local storage capacity of heat also enables a temporal decoupling of consumer-dependent heat use from the volatile renewable electricity generation from wind and solar resources. Moreover there is the option to convert the stored heat back into electricity when needed, creating an electro-thermal electricity storage system with high power output and high capacity.
Therefore, electro-thermal electricity storage systems with high-temperature heat pumps can play an important role in ensuring grid stability and security of supply in the future. Another advantage of electro-thermal energy systems is that they can be integrated promptly into the power plant sites available today, making the best possible use of existing resources and interfaces.
The group „Process Analysis and Systems“ of the Institute of Power Plant Technology, Steam and Gas Turbines is working on a feasibility study of an electro-thermal electricity storage system in the Aachen area in cooperation with a machine manufacturer and a utility company. The system is to be researched and developed in its entirety and transferred to an application on a demonstration scale.
In a first step, a research-scale CO2 heat pump (upper process temperature 120-150 °C, electric power of around 2 MW) for emission-free heat and cold supply is to be conceptually developed and set up. Moreover, the investigations include the integration of different heat and cold capacities as well as additional turbo components (CO2 pump and CO2 turbine). Therefore, the system could be operated as an electro-thermal energy storage with an electricity-to-electricity efficiency of up to 50 %.
To increase the efficiency of the heat pump as well as the roundtrip efficiency of the electro-thermal energy storage in the medium turn, both the development of the main components (compressor, turbine, heat exchangers) as well as the investigation of novel cycle concepts will be pursued. Therefore, the development of software-based optimization tools aids to understand the design of the entire systems, its operating modes and the interaction with the electricity and heating grids.
This project is being carried out as part of the progres.nrw program and is financially supported by the Ministry of Economic Affairs, Innovation, Digitalization and Energy (MWIDE) of the State of NRW for a period of 1.5 years.