|
Simpler cycle (lower component count) Steam cycle
200 175 150 125 100 75 50 25 0
-25 -50
80% CO2 Tcr = 122°C - 20% C6F6
Tmin = 50°C Tcr = 31.06°C Pure CO2
Entropy [kJ/kgK] 25 MW steam turbine
Governing stage
sCO2 Brayton cycle recompression
SCARABEUS simple regenerative cycle
Smaller footprint
(3 stages) CO2 Goals of the SCARABEUS project (source SCARABEUS)
The project also aims to train “a new generation of creative, entrepreneurial and innovative early-stage researchers”, who can face future challenges and “convert knowledge and ideas into products and services for economic and social benefit.”
Project duration is from January 2023 to December 2026. Total budget is 4.45 million euro, of which 3.84 million euro comes from Horizon and 0.61 million euro from UK Research and Innovation.
Participants: University of Seville (project co- ordinator); Instituto Superior Tecnico (Portugal); University of Stuttgart; Baker-Hughes; Fives Cryo; ETN Global; Empresarios Agrupados Internacional; CiTD Engineering; SoftInWay; Technical University Wien; Técnicas Reunidas; Czech Technical University Prague; Politecnico di Milano; Siemens Energy; RPOW Consulting; City, University of London; INERCO; EASY Energy; Rosswag; Doosan- Skoda Power; Azzero CO2
; Plataforma Solar de
Almería; Aalborg CSP. Funding received from the EU’s Horizon Europe, GA No. 101073266.
operate with the new fluid.
Another objective of the project was to run the newly developed heat exchanger for 300 h in a CSP-like operating environment (employing a validation test rig at TUW).
The project participants note that the LCoE of CSP (currently about 150 €/MWh) has not attained the target level of 100 €/MWh except for a few installations in exceptionally good locations. Many ongoing research projects aiming at enhancing the efficiency of the CSP power block and reducing costs are based on sCO2
.
However, high ambient temperatures remain the Achilles heel of sCO2
cycles as their efficiency
drops dramatically in warm environments, where ambient temperatures are close to or higher than the critical temperature of CO2
(31°C), not
The SCARABEUS (Supercritical CARbon dioxide/ Alternative fluids Blends for Efficiency Upgrade of Solar power plants) project aims to demonstrate that sCO2
blends used as the working fluid in CSP plants can significantly reduce the size and increase the efficiency of the power block, potentially reducing CAPEX by 30% and OPEX by 35% relative to state of the art steam cycles, thus exceeding the reduction achievable with standard sCO2
technology. This translates into
30% lower LCoE than currently possible. The project scope included identification of the optimal additive for a new working fluid employing a supercritical CO2
Pressuriser blend and
development of tailored heat exchanger designs, particularly for the air-cooled condenser, to
14 | January/February 2024|
www.modernpowersystems.com Gear box Water cooler Power turbine sCO2-Efekt Sofia test rig (source sCO2 -Efekt) Main compressor
allowing the adoption of condensation (Rankine) cycles with their expected higher efficiencies. The SCARABEUS project aims to address this critical hurdle for the future commercialisation of CSP plants by employing a modified working fluid in which carbon dioxide is blended with additives to enable condensation at temperatures as high as 60°C. This represents a major breakthrough for CSP as it increases the thermomechanical conversion efficiency from the current 42% to above 50%. Both actions will lead to a significant
The sCO2 -Efekt project is focused on the application of supercritical CO2 in thermal energy
storage. The project scope envisages installation of a compressor and turbine test rig (called Sofia) at the Melnik heating plant, with operation scheduled for 2024.
This system is based on the P2H2P (power to heat to power) concept, also called the “Carnot battery”, employing a Brayton cycle for heat to power conversion. Sofia rig operating conditions: up to 550°C; maximum test pressure 25 MPa; flow rate about 25 kg/s; max turbine power 1.5 MWe. The project is being funded by the Czech government. Participants are: CVR (Research
Electrical heater Recuperator Starting Generator compressor
reduction of CAPEX and OPEX with respect to conventional CSP.
Duration: April 2019 to January 2024. Budget: € 4 950 266.25. Source of funding: Horizon. Participants: Politecnico di Milano (project co-ordinator); Laboratorio Energia Ambiente Piacenza; Technische Universitaet Wien; Kelvion; Exergy; University of Seville; City, University of London; Quantis; Abengoa; University of Brescia; Nuovo Pignone. Funding received from the EU’s Horizon 2020, GA No. 814985.
turbine (6 stages)
HP
turbine (9 stages)
IP
turbine (9 stages)
LP
Condensation @ high Tamb
turbine
25 MW sCO2
Temperature [°C]
~3600 mm ~9200 mm
~2900 mm
~2000 mm
~400 mm
~300 mm
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