From prototype testing to pilot-scale solar-fuel production

By combining photovoltaic power, electrochemical conversion and locally available industrial resources, the project is investigating new ways to produce valuable fuels while supporting a more circular, lower-carbon industrial sector.

Energy-intensive industries face the challenge of reducing their reliance on fossil fuels while maintaining access to the energy and chemical feedstocks their operations require. PHOTOSINT addresses this challenge through two complementary pathways: renewable hydrogen production through water splitting and methanol production using carbon dioxide and water. The project is preparing two pilot systems designed to test these technologies under outdoor and industrially relevant conditions.

Two pilot systems for hydrogen and methanol

The project’s pilot demonstrations are being prepared at two industrial sites in Europe, each focusing on a different solar-fuel production pathway.

The methanol pilot at Torrecid in Alcora, Spain, comprises a nine-cell electrochemical system designed to convert carbon dioxide and water into methanol. Initial tests use high-purity carbon dioxide, with subsequent trials planned using a carbon dioxide-containing gas stream recovered from the company’s furnace process. This staged approach will help assess how the technology responds to a more complex industrial feedstock.

The hydrogen pilot at Steklarna Hrastnik in Slovenia comprises 16 electrochemical cells that split water into hydrogen and oxygen. The system is planned for installation on a flat roof with suitable solar exposure. In a later testing stage, the project will also assess the use of purified wastewater, exploring opportunities to incorporate secondary water resources into the process.

These installations are demonstration platforms rather than commercial production plants. Their purpose is to establish how the technologies perform under outdoor conditions, where sunlight intensity, temperature and other operating parameters can fluctuate.

From prototype testing to robust system design

Moving from laboratory research towards pilot demonstrations requires more than effective catalysts and electrochemical materials. The performance and reliability of the complete system depend on how its components work together, including fluid delivery, electrical connections, sealing, pressure control and corrosion resistance.

Prototype testing has helped PHOTOSINT identify practical challenges and refine the electrochemical configurations. For the methanol pathway, targeted optimisation improved conversion performance. One improved catalyst configuration increased methanol production efficiency from approximately 9.5% to 13%. Further changes involving polytetrafluoroethylene (PTFE) and operating pressure contributed to an increase from approximately 1% to 14.5% under specific test conditions. These figures relate to different test configurations and should not be interpreted as a direct comparison of identical operating conditions.

For the hydrogen pathway, extended operation under alkaline conditions demonstrated encouraging durability. The testing programme also highlighted the importance of addressing potential issues such as corrosion, leakage and clogging before progressing to more integrated operation.

The findings have informed practical design changes. In the methanol pilot, the original parallel liquid-flow arrangement was reconfigured after testing identified uneven distribution across its branches. The revised layout routes the mixture through all nine cells in series. Other improvements included additional springs to strengthen catalyst–electrode contact, redesigned bolt insulation to reduce the risk of electrical short circuits, and a dual-channel pump to circulate liquid through both sides of the hydrogen system.

The photovoltaic modules were also selected with operational stability in mind. Encapsulated perovskite modules were chosen to support the requirements of pilot operation rather than prioritising initial performance alone. Together, these refinements show how iterative testing and engineering optimisation are helping prepare the systems for more demanding operating conditions.

Integrating sunlight with electrochemical processes

Each pilot combines photovoltaic modules, which convert sunlight into electricity, with electrochemical cells that use this electricity to drive the required chemical reactions.

The designs incorporate several features intended to make effective use of solar energy. Fresnel lenses concentrate sunlight onto individual photovoltaic modules, while dual-axis solar trackers orient the panels towards the Sun. Thermal coupling transfers heat from the photovoltaic modules to the electrochemical system, potentially reducing the energy needed to maintain suitable operating temperatures. Direct electrical coupling between the photovoltaic modules and electrochemical cells also avoids DC–DC converters, reducing equipment requirements and associated conversion losses.

In the methanol system, carbon dioxide and deionised water are supplied to the cathode side of the cell, while an electrolyte circulates on the anode side. The methanol is expected to collect primarily in the liquid stream, where it can be recovered and analysed.

In the hydrogen system, an alkaline electrolyte circulates through the cells. Hydrogen generated at the cathode is separated from the liquid, dried and measured, while oxygen is produced on the other side of the cell and handled in accordance with the system’s safety requirements.

By integrating photovoltaic power, electrochemical cells and fluid-handling equipment, PHOTOSINT aims to assess how these components perform as part of a complete solar-fuel production system.

Assessing industrial gas and water resources

For these technologies to become relevant to industrial applications, the project must also establish how real industrial resources can be incorporated into the process. PHOTOSINT is therefore assessing the availability, composition and suitability of carbon-containing gas streams and secondary water resources provided by its industrial partners.

Industrial gases can vary in composition, temperature and moisture content, and may contain trace compounds that affect equipment performance or process stability. The project is examining the requirements for feedstock conditioning, monitoring and safe operation to help protect the equipment and support reliable performance.

At Torrecid, the planned progression from pure carbon dioxide to furnace-derived gas will provide an opportunity to assess the methanol system with a more representative industrial input. The characteristics of the gas stream and any necessary conditioning measures will be important considerations in determining its suitability.

Water resources are being assessed alongside the gas streams. Understanding the availability and quality of purified wastewater and other secondary water inputs will help establish whether they can be used in the process and what treatment may be required. This could create opportunities to reduce reliance on virgin resources and make better use of locally available inputs, provided that the resources meet the relevant technical and operational requirements.

Assessing feedstocks alongside system design is essential to preparing realistic pilot demonstrations. It allows PHOTOSINT to consider not only whether the electrochemical process works, but also how it can be adapted to the resources and constraints of different industrial environments.

Validation, monitoring and safety

Before shipment and installation, the pilot systems underwent checks covering mechanical stability, leakage, hydraulic performance and monitoring equipment. The electrochemical cells were tested at water flow rates of 800 mL per minute and pressures above 2 bar, exceeding the intended normal operating conditions. The assembled panels also underwent leak testing for more than 100 hours, including operation with water at 57–60°C, with no leaks observed during those tests.

The solar trackers were tested under the weight of the panels, while electrical and temperature-monitoring equipment was checked before deployment. The hydrogen flow meter was also checked against its factory calibration across the relevant measurement range.

During operation, temperature, voltage and current will be monitored to help evaluate system behaviour and the conversion of electrical charge into the desired products. Hydrogen flow will be measured after drying, and gas chromatography can be used to assess sample purity. Because the expected methanol output is small, it will be collected and measured by weight rather than through continuous liquid-flow monitoring.

Safety remains central to preparing the systems for industrial environments. The installations must address the applicable requirements for machinery, electrical systems, worker protection and risk assessment. The hydrogen demonstration also requires appropriate assessment of explosion and fire hazards, given the flammability of hydrogen and the presence of oxygen.

Neither pilot is intended to supply fuel directly to industrial production during the demonstrations. At Steklarna Hrastnik, for example, hydrogen will be used for performance and purity measurements rather than fed into the glass furnace. This allows the project to focus on validating the technology and its safe operation before considering larger-scale process integration.

What comes next?

The pilot systems are designed to generate evidence on performance, reliability, safety and the practical requirements for future scale-up. Under initial assumptions, the methanol system is expected to produce approximately 0.22 mL per hour, while the hydrogen system is expected to generate around 37 mL per minute. These are projected production rates for demonstration purposes, not confirmed results from outdoor operation.

The next stages will assess how the systems perform under real sunlight and, progressively, with the industrial gas and secondary water resources being evaluated by the project. The resulting data will inform further modelling, technical optimisation and assessment of the technologies’ potential for wider application.

By connecting prototype testing with pilot-system integration and industrial resource assessment, PHOTOSINT is building the technical evidence needed to evaluate solar-driven hydrogen and methanol production in realistic operating environments. The work explores how renewable energy, carbon dioxide and secondary resources could be brought together to produce valuable fuels, contributing to the longer-term development of more resource-efficient and lower-carbon industrial processes.