There are currently quite mature technologies tested on industrial pilot scale to provide synthetic fuels and chemicals from renewable energy sources via a sequence of independent energy and chemical conversion steps (Power-to-X or Carbon Capture and Utilization technologies).

However, energy losses during the different steps (e.g., electricity production or thermochemical conversion) make the process highly energy intense. Also, the provision of affordable, renewable electricity at the needed scale is challenging. A potential workaround to this bottleneck is the development of devices which directly convert solar energy and abundantly available molecules (such as water or carbon oxides) into liquids and gases – within a single device.

These so-called solar-to-X technologies avoid the beforehand conversion of solar energy into electricity and reduce the complexity of the process by a complete integration of the different steps. Solar-to-X technologies, also called artificial photosynthesis or solar fuel technologies, support the vision of a decentralized, local energy and production system with a local provision of the needed resources. In this vision, communities become not only prosumers of electricity, but also of fuels, chemicals and materials.

In this Challenge, solar-to-X technologies must address societal needs not already sufficiently covered by other energy technologies. The developed technologies should demonstrate how they can be embedded in the full functional value chain from generation to use, be self-sustaining in the long-run and provide a win-win opportunity for prosumers and the environment. The objective is to make progress towards synthetic fuels and chemicals technologies which integrate all necessary conversion steps into a single device, and which are solely and directly driven by solar energy. Devices which are driven by electricity or heat are not the focus of this Challenge – except for radically new electrolyzer designs beyond incremental R&D on mature electrolyzer designs. Partially integrated systems, where the overall balance of plant is not significantly simplified (e.g., PV-assisted photoelectrochemical devices) are not within the scope of this Challenge. The use of sacrificial agents has to be avoided and the desired product has to go beyond hydrogen and carbon monoxide.

To summarize, this Challenge focuses on:

1. Novel electrolyzer designs showing a significantly simplified balance-of-plant compared to mature electrolyzer designs;
2. Fully-integrated PV-EC devices, with electrochemical conversion (EC) and photovoltaic unit (PV) combined in a single device;
3. Photosynthetic devices converting directly sunlight and simple feedstock molecules into a fuel or chemical (e.g., Photoelectrochemical devices, Particulate systems, Biohybrid photosynthetic devices, Thermally-integrated photosynthetic devices, etc.);
4. Solar-driven biological conversion devices (e.g., solar cell factories).