Technology readiness levels are levels on a scale that can be used for estimating the maturity of a given technology. There are nine levels, which each represent a state in the development of technology, from the first thoughts to the final technology.

TRL 1: Basic principles observed

• Identification of new concept and its integration, expected barriers, and applications.

• Identification of materials and technologies based on theory.

• Evaluation of potential benefits of the new concept over existing ones.

TRL 2: Technology concept formulated

• Enhanced knowledge on technologies, materials, and interfaces.

• New concept is investigated and refined.

• First evaluation about the feasibility.

• Initial numerical knowledge.

• Qualitative description of interactions between technologies.

• Prototyping approach and preliminary technical specifications for laboratory test are defined.

TRL 3: Experimental proof of concept

• First laboratory scale prototype or numerical model.

• Laboratory tests of the technological element, but not the whole integrated system.

• Identification of key parameters characterising the technology.

• Verification of the proof of concept through simulation tools and cross-validation with literature data (if applicable).

TRL 4: Technology validated in lab

• Small-scale prototype integrated with complementing subsystems at laboratory level.

• Validation of the new technology through enhanced numerical analysis (if applicable).

• Measurable Key Performance Indicators.

• Prototype shows stable performance (either TRL4 or TRL5, depending on the technology)

TRL 5: Technology validated in relevant environment

• Large scale prototype integrated with components of supporting elements and auxiliaries.

• Robustness is proven in relevant working environment.

• Prototype shows stable performance (either TRL4 or TRL5, de- pending on the technology).

• The process is reliable, and performances live up to expectations (either TRL5 or TRL6, depending on the technology).

• Other parameters concerning scale-up, environmental, regulatory, and socio-economic issues are defined and qualitatively assessed.

TRL 6: Technology pilot demonstrated in relevant environment

• Demonstration of the technology is fine-tuned to a variety of operating conditions in relevant environment.

• The process is reliable, and the performances live up to the expectations (either TRL5 or TRL6, depending on the technology).

• Demonstration of interoperability with other connected technologies.

• Manufacturing approach is defined (either TRL6 or TRL7, depending on the technology).

• Environmental, regulatory, and socio-economic issues are addressed.

TRL 7: System prototype demonstration in operational environment

• Full scale pre-commercial system is demonstrated in operational environment.

• Compliancy with relevant environment conditions, authorisation issues, local/national standards is guaranteed.

• Integration of upstream and downstream technologies are verified and validated.

• Manufacturing approach is defined (either TRL6 or TRL7, depending on the technology).

TRL 8: System complete and qualified

• Technology has been experimented in deployment conditions and proven its functioning in its final form.

• Manufacturing process is stable enough for a low-rate production.

• Training and maintenance documentation are completed.

• Integration at system level is completed.

• Full compliance with obligations, certifications, and standards of the addressed markets.

TRL 9: System proven in operational environment

• Technology proven fully operational and ready to be commercialised.

• Full production chain is in place and all materials are available.

• System optimised for full rate production.