Thermochemical HYDROgen production in a SOLar structured reactor:facing the challenges and beyond

Project Information

HYDROSOL-beyond

Grant agreement ID: 826379

DOI

10.3030/826379

Project closed

EC signature date 3 December 2018

Start date 1 January 2019

End date 31 March 2024

Funded under

• SOCIETAL CHALLENGES - Secure, clean and efficient energy

Total cost

€ 2 999 940,00

EU contribution

€ 2 999 940,00

Coordinated by

ETHNIKO KENTRO EREVNAS KAI TECHNOLOGIKIS ANAPTYXIS
Greece

Periodic Reporting for period 3 - HYDROSOL-beyond (Thermochemical HYDROgen production in a SOLar structured reactor:facing the challenges and beyond)

Reporting period: 2022-07-01 to 2024-03-31

Summary of the context and overall objectives of the project

The complete substitution of fossil fuels by a mixture of renewable and sustainable energy sources, assuring the production of carbon-neutral or ultimately even carbon-free energy chemical products, is one of the most persistent quests both within the EU and globally as it seems the only vital solution for the preservation of the future of mankind.
H2 has been increasingly investigated as a potential energy carrier and storage medium in the last few decades. Especially in Europe, many research programs have been focused on developing environmentally friendly H2 production routes. These efforts aim to compete the conventional H2 production process, which is methane reforming, a relatively “carbon-rich” chemical process.
HYDROSOL-beyond continued the series of HYDROSOL-related research projects targeting the production of renewable green H2 from water splitting based on the use of concentrated solar thermal power for the production of H2 from the dissociation of water via redox-pair-based thermochemical cycles on structured reactors.
Research spanned from the scale of the laboratory up to the demonstration scale of the already existing HYDROSOL platform at the SSPS-CRS solar tower at the Plataforma Solar de Almeria in Spain.
The main objectives of the project were the:
• minimization of the energy losses of the system mostly related to the high consumption of inert gas
• efficient recovery of heat at rates >60%
• development of redox materials and structures with enhanced stability (>1,000 cycles) and with production of hydrogen ~three times higher than the current state-of-the-art Ni-ferrite foams
• development of a technology with annual solar-to-fuel efficiency of ≥10%
• improvement of the reactor design and introduction of novel reactor concepts
• development of smart process control strategies and systems for the optimized operation of the plant
• demonstration of efficiency >5% in the field tests, i.e. during operation at the 750kWth HYDROSOL solar platform (PSA, Spain)

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Continuing the work that has been done in the previous project periods, the activities on the investigation, design and development of novel concepts to be integrated in the existing plant and the tasks and activities undertaken on the solar platform at Plataforma Solar de Almeria in order to be able to perform solar experiments, run in parallel.
Novel lattice structures of redox metal oxides have been manufactured and evaluated at the laboratory scale both for the water splitting as well as for the oxygen trapping concept. The long-term durability on NiFe2O4 lattice structures run until the end of the project, with the H2 yield reaching a more or less stable value after more than 1100 cycles of operation without deactivation.
The minimization of inert gas consumption was investigated with the successful implementation of an innovative concept of oxygen trapping using redox materials being tested at the laboratory scale.
Within the final phase of the project key achievements included the upscaling of the hybrid ceramic-metallic heat exchanger and its integration on the existing platform for recovery of heat from the solar platform.
Repair and restore actions took place at the reactors and associated optics (secondary concentrators and the quartz window). Solutions were provided for dealing with design drawbacks ensuring the safe and efficient operation on the platform (e.g. new window flange design and new secondary concentrator design and material).
Two reactor concepts based on NiFe2O4 redox material were investigated at the demonstration scale on the solar platform. The directly and indirectly irradiated solar reactors. Full scale experiments and analysis for both reactor types revealed the issues and limitations in their operation and the margin for improvement. Inherent characteristics of the directly heated solar cavity reactor design and materials limit the potential increase of the solar-to-fuel efficiency.
The directly irradiated reactor showed improved hydrogen production at higher temperatures but faced issues with solar flux distribution and inhomogeneous heating inside the cavity. The indirectly irradiated reactor operated up to 1300ºC but had lower hydrogen production.
During the experimental campaigns on the solar platform a heat recovery rate of 68% was achieved with the coupled operation of the heat exchanger and the directly irradiated solar reactor. The solar-to-fuel efficiency that was achieved in the field was approx. 2% under real environmental conditions .
Due to the low H2 production the techno-economic study led to a projected cost of H2 that was significantly far from competitive, highlighting the need for materials with higher yields and better reactor designs, while Life Cycle Analysis revealed that major contributor in the environmental impact were the materials used in the solar reactor, suggesting improvements in material selection/processing and pointing the importance of nitrogen recycling to reduce the environmental footprint.
Overall, the project made significant technical advancements but revealed that further improvements are necessary for commercial viability and environmental sustainability.

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)

Concentrated solar energy is mainly utilized in the production of electricity in solar thermal power plants. The possibility of exploiting such facilities for the simultaneous storage of solar energy into a high quality clean energy carrier, such as H2, would provide another pathway for the efficient and utmost exploitation of the solar potential.
The work that was conducted during the whole duration of the project led to deeper knowledge of the operation of major components of the process in the actual environment of a solar tower facility and identified strengths and weaknesses. The HYDROSOL technology of solar H2 production from water splitting based on metal oxide redox cycles is feasible, however, still immature for making the step towards commercialization.
Within the project innovative solutions for the minimization of inert gas consumption and for the heat recovery rates exceeding 60% were implemented at the laboratory and the solar platform scale respectively proving their potential towards improvement of the overall solar process efficiency.
Solar H2 production on the different structured reactor concepts that were tested on the solar platform in real environment was low, which led to discouraging technoeconomic results.
Although, theoretically solar thermochemical processes for H2 production show significant potential, substantial technical and economic challenges remain, before large-scale deployment is feasible.
Other studies in the same field lead to more optimistic scenarios that could bring the solar thermochemical production of H2 closer to a future H2 economy, provided that advancements in efficiency are achieved that are expected theoretically but still have not been achieved in the field.
The innovations that were achieved within HYDROSOL-beyond advance the European leadership and create the conditions for the active involvement of high-potential players in the fields of solar thermochemical research, technology and enterprises.
There are still challenges that have to be dealt with, however, the project highlights the promise of solar thermochemical technologies and opens new paths for European initiatives in leading technological advancements in the field of high temperature solar technologies.

Directly irradiated reactors on the solar platform

hybrid heat exchanger conceptual design

Overview of the thermochemical solar plant in Almeria, Spain

Hydrosol-beyond plant operation_ Final campaign

Indirectly heated reactor

Novel hybrid ceramic-metallic heat exchanger on integrated on the solar platform

Performance of CeO2 coated foam solar cavity reactor on solar simulator

NiFe2O4 lattice multi-cyclic testing in tube reactor