Frequently asked questions

The main goal of SOLEAS is to produce ethene and ammonia in an energy efficient manner in a single Solar-to-X device as important chemicals for further material production.

In addition to developing a decentralized solar photoelectrochemical device for the climate-neutral production of ethene and ammonia, a “prosumer vision” is also being designed to promote community engagement. To this end, we are analyzing the value chain, identifying stakeholders, and integrating them into the development process in a participatory manner.

• The interaction between the photoactive materials and reactor design must be optimized and harmonized.
• The photoreactors currently being researched are still individual systems and need to be developed for further scaling.
• Stable photoactive electrodes based on materials from abundant resources need to be developed.
• Since only a certain portion of the solar spectrum can currently be used, we need further research for land-efficient deployment of solar photoreactors: optimized optical systems are required to modify solar wavelengths, focus photons and increase the solar energy hitting the photoactive sites.

This project will develop a Soar-to-X device based on a photoelectrochemical process to produce “green” and “climate-neutral” ethene and ammonia, thereby making a decisive contribution to the decarbonization of industry.

Ethene (C₂H₄), also known as ethylene, is a colorless, flammable gas. It is mainly used in plastics production, for example to manufacture polyethylene (PE), the most widely produced plastic, or in the chemical industry for ethanol, ethylene oxide, or plasticizers and solvents.

Ammonia (NH₃) is a colorless gas and toxic in higher concentrations. Ammonia is mainly used in fertilizer production and is an important industrial chemical worldwide. It is used as a refrigerant, in the chemical industry for nitric acid, plastics, cleaning and disinfecting agents, or paints and resins. In addition, ammonia is being discussed as a hydrogen-based energy source.

The SOLEAS technology process also functions as a form of carbon capture and storage (CCS) by utilizing the CO₂ produced as a waste product during biogas production as an important source. The captured CO₂ from biogas upgrading is highly concentrated and is not diluted like in flue gas (around 10%) or worse, as in air (>0.04%). Even though a few pollutants (sulphur, organic compounds) must be removed, it is relatively easy to handle and to process. The nitrogen required for the chemical conversion process can be extracted directly from the air – a readily available and abundant resource including 78 % of N₂.

Essentially, the following input materials are used:

• Biogenic Carbon dioxide (CO₂) as byproduct from biogas plants
• Nitrogen (N₂) from the air
• Water (H₂O)

Biogenic CO₂from the biogas industry is among the most promising solutions to mitigate global climate warming and therefore a promising source for SOLEAS Solar-to-X Device. Capture technology is mature, and by 2021 had already been implemented in Europe’s 1,000 biomethane production units. Further, most biogas plants are geographically widely distributed, anchored in local settings, and represent a local circular economy opportunity in partnership with CO₂ consumers.

The advantages are:

• Biogas has a high CO₂concentration and can therefore be efficiently separated during purification.
• Biogas plants come in many different sizes (50 to 2,000 NM³/h) and are geographically widespread.
• Biogas plants are usually operated locally by regional stakeholders and can thus promote a local circular economy.
• Biogas plants are rapidly gaining importance in the production of energy and heat. The direct use of CO₂emissions represents an efficient and profitable development of technology.

• Saves energy: Direct chemical conversion of the input materials in the reactor using sunlight saves energy compared to conversion steps/technologies that involve high losses.

• CO₂ storage: Used biogenic CO₂, which would otherwise be emitted into the atmosphere, can be returned to the cycle.

• Fewer emissions: Conventionally produced ethene, which is made from naphtha or akene through cracking in several process steps, emits approximately 2 t CO₂ per ton of ethene. This could be avoided through sustainable ethylene production using the SOLEAS photoreactor.

• No fossil fuels: Conventional ammonia production using the Haber-Bosch process requires large amounts of hydrogen, which is usually produced from fossil resources. The Haber-Bosch process emits around 1.9 t CO₂ per ton of NH₃. These emissions can also be avoided with ammonia from the photoreactor.

• Decentralized production: Since ammonia is usually produced centrally, it has to be transported over long distances. Local production with the SOLEAS device shortens long transport routes.

In the SOLEAS project, an interdisciplinary project team is developing a device that produces green and climate-neutral chemicals and energy carriers directly by solar energy.  By using local biogenic CO₂ and N₂ from air, and integrating the technology into existing value chains, SOLEAS empowers communities to act as prosumers, while aiming for a self-sustaining solution that creates long-term win-win benefits for both prosumers and the environment.

1. Community engagement and long-lasting value chain: Defining use cases and application scenarios where the SOLEAS device is integrated into a fully functional value chain from generation to end use.
2. Design, produce, characterize, and test new photo(electro)catalysts: Optimizing both the photoanode and photocathode—including their materials, composition, adhesion, durability, geometry, and surface area—to match the photoreactor’s design and requirements. Additionally, scale up the manufacturing processes for these electrodes to simplify and increase the efficiency of industrial-scale plants.
3. Design a novel reactor driven by solar energy, including an optimized optical unit which tunes incoming solar radiation (concentrator optics) towards specific wavelengths for maximum energy harvesting and reaction efficiency and develop a flexible and scalable reactor geometry, optimally aligning irradiation fields with flow behavior.
4. Developing a single photoelectrochemical device where the reactor is integrated with the new developed catalysts and the optical unit. The developed device will reach TRL 5-6 at the end of the project.
5. Perform a sustainability assessment of the developed technology considering its environmental, techno-economic, energetic and social potential impact.
6. Maximize the impact of the project through wide dissemination, communication, contributions to portfolio management, exploitation, and standardization actions.

1. New photo(electro)catalysts: An innovative design will be developed, optimizing both the photoanode and photocathode—including their materials, composition, adhesion, durability, geometry, and surface area—to match the photoreactor’s design and requirements. Additionally, scale up the manufacturing processes for these electrodes to simplify and increase the efficiency of industrial-scale plants.

2. Innovative optical unit and solar receiving reactor: Design a novel optical unit which tunes incoming solar radiation (concentrator optics) towards specific wavelengths (wavelength modifier) for maximum energy harvesting and reaction efficiency and develop a solar receiving reactor (reactor tubes) which is flexible and scalable.

3. Single photosynthetic device under natural sunlight: Developing a single photosynthetic device where the reactor and the new development catalysts and materials with the optical unit are integrated and perform under artificial and natural sunlight conditions.

A Solar-to-X device is the equipment to produce chemicals from low molecular substances only via the inputs of solar energy. This embraces the optical part to harness and direct solar light photons, the solar photoreactor and the essentially important photoactive material structures.

We use the energy of the sun’s photons to activate a photoactive material and subsequently induce chemical reactions. In a Solar-to-X device we harvest solar energy, focus photons to the reaction sites and ultimately produce products, solely driven by energy from the sun.