NOVEL CO2-BASED ELECTROTHERMAL ENERGY AND GEOLOGICAL STORAGE SYSTEM - CEEGS

Project Information

CEEGS

Grant agreement ID: 101084376

DOI

10.3030/101084376

Project closed

EC signature date 21 October 2022

Start date 1 November 2022

End date 31 October 2025

Funded under

• Climate, Energy and Mobility

Total cost

€ 2 992 060,00

EU contribution

€ 2 992 060,00

Coordinated by

UNIVERSIDAD DE SEVILLA
Spain

Periodic Reporting for period 1 - CEEGS (NOVEL CO2-BASED ELECTROTHERMAL ENERGY AND GEOLOGICAL STORAGE SYSTEM - CEEGS)

Reporting period: 2022-11-01 to 2024-04-30

Summary of the context and overall objectives of the project

The CEEGS project (CO2-based electrothermal energy and geological storage system) develops a "high-risk/high-reward" concept aiming to bring a highly efficient, cost-effective and scalable energy storage technology by making feasible the integration of transcritical CO2 cycles with underground energy storage achieved through the simultaneous compressed CO2 storage and geothermal heat extraction.
CEEGS has exceptional characteristics regarding: i)RES integration
a. scalable and up to large-scale energy storage
b. combined CO2 geological sequestration
c. capacity for integration with large CO2 producers
d. ,heating and cooling integration
e. ,low environmental impact, and costs
The concept is based on a hybrid system for energy storage based on thermal and mechanical energy with underground compressed CO2. It evolves in a closed loop as heat transfer fluid and storage media. If successful, it will be a high-energy storage capacity technology due to underground storage with the additional benefit of partial CO2 sequestration in the terrain. It is a trigeneration system that can provide electricity, heat and cold with potential low costs and low environmental impact.
The key challenges for advancing this concept are related to the interface between the transcritical cycle and the subsurface storage, where there are knowledge and technological gaps. The main objective is to provide scientific proof of this technological feasibility, advancing in three essential challenges:
i. integration of surface and subsurface components;
ii. conceptual design of the components;
iii. analysis of techno-economic feasibility and impacts for designs

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's first half has satisfactorily fulfilled all the relevant activities planned.
Concerning geological environments, the viability conditions of the systems have been defined in terms of reservoir depth (porous media and salt cavities). The sensitivity of the plume setup phase and the charging/discharging cycles to the different parameters of the reservoir have been analysed. The numerical simulation of the CO2 production and injection cycle operations has allowed the study of the transient behaviour of the double wells. Geochemical modelling has been carried out in three scenarios. The final result is the definition of the criteria for the selection of storage in porous media and saline cavities. To this end, a tool has been designed to classify candidate reservoirs.
Numerical models covering different aspects have been successfully developed for the design of transcritical CO2 systems and components. Reference designs and main parameters of the transcritical CO2 cycle have been defined. Two power scales, 5 MW and 100 MW, have been considered. No limitations to the coupling of the processes were detected.
The integration and optimisation of renewable energy systems is progressing as planned. The digital twin (DT) of the CEEGS system has been created by developing and evaluating mathematical steady-state models that examine two distinct categories: i) EES systems without geological CO2 storage ii) EES systems with geological storage of CO2. The development and evaluation of the dynamic models include implementing advanced control designs and the development of the DT of the models.
Model validation is in progress. The evaluation of the Ketzin and Hontomín pilot sites has been carried out. The construction of the experimental installation and installation of the measurement system has been carried out, and the test facility has been approved by an independent inspection body. Preliminary tests were performed, and the main components and instrumentation system were successfully operated.
An impact assessment on the safety and sustainability of the technology was developed, identifying the main risks of CEEGS in different risk categories.

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)

Viability. CEEGS system has been successfully simulated at a range of power capacities from 1-100 MW to the stationary models. Feasibility under different operation modes, without and with the subsurface geological CO2 storage. Integrating subsurface geological CO2 storage results, in most cases, in higher round-trip efficiencies. The system can be adapted to provide heat or cold in renewable trigeneration systems from renewables. The novel concept of the energy storage cycle will be validated through experimental work and analysis of existing sites.
Integration in industries. CEEGS systems can complement energy-intensive and/or CO2-emitting industries since they can store excess electrical energy and reuse it later or provide heat/cold to industries or district heating and cooling networks. They can also be used to decarbonise CO2 emitting industries, integrate CO2 capture systems, use the captured CO2, and provide energy for the system.
Transversal intersectoral decarbonisation. CO2 sequestration and geothermal extraction. Potential to be applied in a wide range of geological environments, both in porous media reservoirs and in salt cavities. Different combinations are possible. CO2 sequestration occurs in a considerable percentage, higher than expected, essentially due to residual trapping during charge/discharge cycles. A constant flow of CO2 can be maintained from the industrial source. Under the right heat flux density conditions, the efficiency of the underground component can exceed 100% due to geothermal heat extraction.
Scalable energy storage system and flexible power production. The preliminary sizing (1-100 MW) carried out does not detect limitations in terms of the energy storage plant's scalability. The transcritical surface CO2 cycle can operate independently of geological injection/production processes, which may be limited by reservoir size, well diameter, or mass flow rate.
Environmental impact. Early results from the expert judgment dataset as part of the risk assessment procedure show low to medium risk scores for the environmental risk category.

CEEGS concept