By Dr. Thomas Gallinger and Pierre Huck, TÜV SÜD Industrie Service GmbH
Hydrogen plays an increasingly important role in energy storage and production. One example is power-to-X (P2X) concepts such as the electrolysis of water, where energy from renewable sources is used to produce (green) hydrogen. Apart from the above, (grey) hydrogen is a by-product of many industrial processes, including the production of ethylene or chlorine. Hydrogen thus produced can be injected into natural gas pipelines or fed into a dedicated hydrogen network and stored.
Production of low-carbon hydrogen is advocated by national hydrogen strategies and other actions to combat climate change. And in view of rising prices for natural gas (NG) and emission certificates, power-station operators and energy producers are likewise starting to consider new solutions. As a result, the first combined-cycle power plants (CCPPs) that start off being powered by natural gas but offer the option of subsequent conversion to hydrogen co-firing or firing of pure hydrogen are being realised. The NG-fired CCPPs that are currently being planned or built typically have a design life of over 25 years and can thus be expected to be transitioned to hydrogen firing during their lifetime.
Roadmap to a hydrogen economy
However, not every power station or plant is suitable for firing hydrogen instead of natural gas – in other words, H2-ready. Firing hydrogen in power stations that are not H2-ready can adversely affect their performance and safety. As a result of the change, these power stations may lose their insurance coverage or become what are known as ‘stranded assets’. Power station operators should obtain third-party H2-readiness certification of their plants right from the conceptual design to future-proof their plants and to ensure that the reliability and profitability of their electricity production extends to firing hydrogen.
So far, no clear definitions of H2-readiness have been available to create transparency for all market players, spanning original equipment manufacturers (OEMs), engineering, procurement and construction companies (EPCs), plant operators, investors and insurance companies. In addition, there is still no standard that addresses a CCPP as a complete system instead of only dealing with individual aspects such as the gas-supply system.
Given this, TÜV SÜD has developed the world’s first guideline that sets out the essential requirements for the H2-readiness of gas-fired power stations. Conducting a peer review that included operators, manufacturers, and insurance companies, the hydrogen experts additionally gathered input from further parties and integrated it into the guideline.
A critical first step is to lay out the configuration of the CCPP in a sensible manner to identify all impacts of the transition to co-/firing hydrogen. In a next step, high-level aspects such as explosion-protection and fire-safety concepts, hazard and risk analyses, and conformity and approvals must be evaluated for the entire plant.
To ensure safe and successful conversion to hydrogen co-/firing, operators must specify their requirements for power stations while clarifying some essential questions, including:
- Overall plant performance: How will conversion impact on the electricity output of the plant, component efficiency and lifetime, and maintenance concept?
- Gas supply after conversion: What hydrogen quality grade will be used for firing? What is to be fired? Hydrogen blended in natural gas, or pure hydrogen? What mixing ratio is intended? Do fluctuations need to be considered? Which specific limit values need to be observed (pressure, temperature, volumetric flow, and calorific value)?
The H2-readiness requirements for all systems, components and the complete plant are derived from these framework conditions. A suitable concept must set out a clear path for conversion of all of the affected systems and components in the plant, starting from their condition at the time when the plant goes into service firing NG. Certification serves as proof of H2-readiness for insurers, operators, and investors.
Certification inspires trust
The certification scheme developed by TÜV SÜD covers three stages, each of which can be assessed separately in third-party certification: the Concept Certificate for the conceptual design of the plant; the Project Certificate covering successful realisation of the NG-fired plant; and, finally, the ‘Transition Certificate’ which assesses the retrofitting and upgrading necessary for transitioning to hydrogen firing.
The Concept Certificate covers the bidding phase for a new CCPP. It verifies that the underlying concept covers all relevant issues and includes feasible solutions. The certificate-holder is the concept owner – typically the OEM as plant manufacturer, or the EPC. Although certification is process- and not project-specific, it will also assess an exemplary project-specific application of the processes. Future expansion plans provide for the certificate to be offered for the upgrading of existing plants in addition.
The Project Certificate covers the realisation phase. It verifies correct implementation of the H2-readiness concept and checks that the plant is designed and constructed in conformity with the criteria defined in the guideline. Potential certificate holders may be the plant manufacturer or EPC seeking to demonstrate the successful implementation of the concept to the plant operator, or the plant operators themselves, seeking confirmation by commissioning third-party certification. As the certificate refers to a specific plant and the systems and components that it requires, it is project specific.
For the Transition Certificate, the experts will scrutinise the conversion process when the firing gas supply is switched from natural gas to pure hydrogen or a gas mixture. They will verify that the defined retrofitting and upgrading measures have been appropriately implemented and that the plant’s overall performance and safety is in conformity with regulatory requirements. The certificate holder can be the manufacturer or EPC in charge of the upgrading and retrofitting measures, seeking to demonstrate successful implementation of the upgrade to the owner. Plant owners, too, may commission third-party certification of the implementation of retrofit measures.
The H2-readiness guideline developed by TÜV SÜD provides the various stakeholders in a power station project with clarity and transparency of how power stations can be retrofitted from the firing of natural gas to the firing of hydrogen blended in natural gas or pure hydrogen. The guideline addresses the framework conditions to be clarified and the relevant components and systems. The certification scheme comprises three stages, covers all processes up to the conversion to hydrogen and can be applied by independent third parties.
The world’s first TÜV SÜD H2-Readiness Concept Certificate was awarded to Siemens Energy for its ‘H2-ready’ power stations. This pilot certification triggered a flood of enquiries from various market players, thus demonstrating the relevance of the topic and the high demand for independent assessment and certification of the solutions on offer.