Sun-To-X · Project

Turning Sunlight Into Storable Liquid Fuel for Transport and Energy

energyPrototypeTRL 4

Imagine if you could bottle sunlight the way you bottle water — and then pour it into a truck or a power plant whenever you need energy. That's essentially what Sun-To-X figured out. They built a device that uses sunlight and humidity from the air to first make hydrogen, then converts it into a special liquid fuel called Hydrosil that's non-toxic, energy-dense, and can sit on a shelf without degrading. As a bonus, the same fuel can be used to break down waste plastics, closing the loop on two problems at once.

By the numbers

100 cm²

Prototype PEM-PEC cell and photoanode assembly size

10%

Target solar-to-hydrogen (STH) efficiency for tandem cell

8.2 mA/cm²

Target water splitting photocurrent under standard solar illumination

Consortium partners across 6 countries

56%

Industry participation ratio in consortium

The business problem

What needed solving

Transport and energy companies face mounting pressure to decarbonize, but current options like battery electric or compressed hydrogen come with major infrastructure costs and practical limitations for heavy-duty and long-distance applications. There is no widely available carbon-free liquid fuel that can use existing fuel distribution infrastructure while offering long-term storage stability. Companies need a drop-in renewable fuel that doesn't require rebuilding their entire logistics chain.

The solution

What was built

The team built a 100 cm² prototype photoelectrochemical cell (PEM-PEC) that converts sunlight and ambient humidity into hydrogen, plus thermochemical reactors that convert that hydrogen into Hydrosil — a storable, non-toxic, carbon-free liquid fuel. They also demonstrated large-area membrane photoanode assemblies targeting 10% solar-to-hydrogen efficiency.

Audience

Who needs this

Heavy-duty fleet operators seeking carbon-free liquid fuel alternativesSolar energy companies looking for long-duration energy storage solutionsChemical companies interested in renewable fuel production technologyWaste management firms exploring chemical recycling of plasticsFuel distributors wanting to add carbon-free products to their portfolio

Business applications

Who can put this to work

Transport & Logistics

enterprise

Target: Fleet operators and fuel distributors looking for drop-in renewable fuel alternatives

If you are a logistics company struggling with decarbonization mandates for your heavy-duty fleet — this project developed Hydrosil, a carbon-free liquid fuel with long-term stability that works in transport applications. Unlike hydrogen gas, it doesn't need pressurized tanks or new infrastructure. The 100 cm² prototype device was demonstrated, and Toyota Motor Europe led the consortium, signaling serious automotive industry interest.

Renewable Energy Storage

mid-size

Target: Solar farm operators and grid-scale energy storage providers

If you are an energy company that loses revenue when solar generation exceeds grid demand — this project built a photoelectrochemical system that converts excess solar energy into Hydrosil, a stable liquid fuel that stores energy long-term without degradation. The membrane photoelectrode assemblies target 10% solar-to-hydrogen efficiency and operate using only ambient humidity as water supply. This means energy storage without water infrastructure costs.

Plastics Recycling & Waste Management

any

Target: Waste management companies and chemical recyclers dealing with hard-to-recycle plastic streams

If you are a waste management company facing tightening regulations on plastic waste — this project demonstrated that Hydrosil can be used for the valorization of waste plastics as part of a circular economy cycle. The consortium of 9 partners across 6 countries, with 56% industry participation, validated this dual-use application. This opens a second revenue stream from the same fuel production process.

Frequently asked

Quick answers

What does this technology cost compared to conventional fuels?

The project data does not include specific cost-per-liter or production cost figures for Hydrosil. The project objective acknowledges that solar-to-chemical fuel technology has historically been limited by economic viability, and Sun-To-X aimed to address scalability challenges. Cost competitiveness would depend on further scale-up beyond the 100 cm² prototype stage.

Can this scale to industrial fuel production volumes?

The project demonstrated a 100 cm² PEM-PEC prototype cell and developed large-area membrane photoanode assemblies at that same scale. The deliverables describe this as a 'medium size upscaled device' used as a 'guiding example for the final upscaling step.' Industrial-scale production would require significant further development beyond this prototype size.

Who owns the intellectual property and can I license it?

The consortium is led by Toyota Motor Europe (Belgium) and includes 9 partners across 6 countries with 5 industry partners and 3 SMEs. IP ownership follows Horizon 2020 grant agreement rules, typically staying with the partner who generated it. Licensing discussions would need to go through the relevant consortium members.

How does Hydrosil compare to green hydrogen as a fuel?

Based on the project data, Hydrosil is described as carbon-free, non-toxic, energy-dense, and a liquid fuel with very good long-term stability. Unlike compressed or liquefied hydrogen, it's a liquid at normal conditions, which eliminates the need for high-pressure storage tanks. Hydrogen is produced as a chemical intermediate and then converted to Hydrosil through a thermochemical reaction.

What regulatory approvals would be needed to use Hydrosil commercially?

The project data does not specify regulatory status or approvals for Hydrosil as a commercial fuel. Given it is described as non-toxic and carbon-free, it may face fewer safety hurdles than some alternatives. However, any new fuel for transport would need to go through national and EU fuel certification processes before commercial use.

What's the timeline before this could be available commercially?

The project ran from September 2020 to February 2024 and reached the 100 cm² prototype demonstration stage. Based on available project data, significant engineering work remains for industrial scale-up. A realistic commercial timeline would depend on follow-on development projects and industry investment beyond the prototype.

Does the system need a dedicated water supply?

No. One of the key technical achievements is that the membrane photoelectrode assemblies operate using only ambient humidity as the water supply. This eliminates the need for water infrastructure, purification systems, or connection to water networks — a major advantage for deployment in arid, sunny regions where solar fuel production is most viable.

Consortium

Who built it

The Sun-To-X consortium is notably industry-heavy at 56% — 5 out of 9 partners are industrial, including 3 SMEs. It's led by Toyota Motor Europe, one of the world's largest automakers, which signals genuine commercial interest in this fuel technology beyond academic curiosity. The consortium spans 6 countries (Belgium, Switzerland, Germany, France, Netherlands, USA), combining European research strength with global automotive industry backing. With only 1 university partner versus 3 research organizations and 5 industry players, the balance tilts heavily toward applied development rather than fundamental research.

TOYOTA MOTOR EUROPE NVCoordinator · BE
COMMISSARIAT A L ENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVESparticipant · FR
HYSILABSparticipant · FR
ENGIEparticipant · FR
LGI SUSTAINABLE INNOVATIONparticipant · FR
ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNEparticipant · CH
HELMHOLTZ-ZENTRUM BERLIN FUR MATERIALIEN UND ENERGIE GMBHparticipant · DE
STICHTING NEDERLANDSE WETENSCHAPPELIJK ONDERZOEK INSTITUTENparticipant · NL

How to reach the team

Toyota Motor Europe NV, Belgium — reach out to their advanced research or sustainable fuels division

Order a report on this consortium See TOYOTA MOTOR EUROPE NV profile →

Next steps

Talk to the team behind this work.

Want to explore how Hydrosil solar fuel technology could fit your energy or transport decarbonization strategy? SciTransfer can arrange a direct introduction to the Sun-To-X research team and help you evaluate licensing or partnership options.

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