The project aims at moving technological frontiers for low-emission combustion of hydrogen to fuel modern gas turbines at high firing temperatures and pressures, beyond the latest state-of-the-art. This will be achieved whilst maintaining high engine performance, efficiency, fuel and load flexibility, without diluents. At the same time, all emission targets set by the Clean Hydrogen JU Strategic Research and Innovation Agenda (SRIA) will be met. The idea is based on a proprietary combustion technology, designated constant pressure sequential combustion (CPSC) already deployed into the GT36 H-class engine (760 MW in combined cycle). The CPSC concept, based on a unique longitudinally staged combustion system, yields the best fuel flexibility and has the greatest potential to achieve the project target of demonstrating stable and clean combustor operation with concentrations of hydrogen admixed with natural gas, up to 100%, at firing temperatures typical of modern H-Class engines. The new, improved combustor design will be fully retrofittable to existing gas turbines, thereby providing opportunities for refurbishing existing assets. The primary objective is to demonstrate the CPSC technology in engine relevant environment (TRL6) in three steps (70, 90 and 100 vol% H2). In this pursuit, a subset of specific performance data (KPIs) will be met within the project timeline and with the planned resources and allocated budget. The project uses state-of-the-art computational tools, analytical modelling, and diagnostic techniques to investigate static and dynamic flame stabilisation. Testing is performed at world-class laboratories in test campaigns at reduced scale and in full size (at atmospheric and pressurised conditions). In preparation for commercialisation, the project will also develop a roadmap towards deployment of the developed system into operation and demonstration into a power plant environment quantifying the valuable contributions to the EU Green Deal.

Combustion of hydrogen from renewable sources is an emerging technology that can replace fossil fuels and so provide carbon-neutral energy. The goal of POLKA is to solve serious technical problems, which are unique to hydrogen combustion: thermoacoustic instabilities and flashback. Thermoacoustic instabilities are large-amplitude pressure oscillations caused by an escalating interaction between the flame and acoustic waves; they tend to occur unexpectedly and cause major hardware damage. Flashback is the dangerous phenomenon of the flame propagating backwards into components not designed for high temperatures. The ultimate vision of POLKA is to create new physical insight and advanced simulation tools, so as to underpin the development of hydrogen-fuelled combustion systems (gas turbines, aero-engines, boilers furnaces, etc). The methods to be used are a combination of experiments, numerical simulations and analytical techniques. Experimental validation of numerical and analytical results is a high priority. POLKA will train a cohort of 15 ESRs, each enrolled in a 3-year doctoral programme. The research project is divided into 15 interlinked sub-projects, each forming an individual PhD project for an ESR. The ESRs will be equipped with a wide portfolio of skills, including traditional academic research, and also transferable skills in outreach and gender issues. This will be supplemented by a unique integrated training programme in innovation, exploitation and entrepreneurship. Secondments are an important part of the training programme. The ESRs will develop an innovation-oriented mind-set and have excellent career perspectives in the renewable energy sector. The POLKA website will feature an extensive range of open-access training resources, which will be maintained beyond the formal end of the project. POLKA has a balanced consortium, both in terms of gender (5 female and 6 male main supervisors), and in terms of sector (6 academic and 4 industrial beneficiaries)

Natural gas fired Combined Cycle (CC) power plants are currently the backbone of EU electrical grid, providing most of regulation services necessary to increase the share of non-programmable renewable sources into the electrical grid. As a consequence, Original Equipment Manufacturers (OEMs) and Utilities are investigating new strategies and technologies for power flexibility. On the other hand, existing cogenerative CCs are usually constrained by thermal user demand, hence can provide limited services to the grid. At the same time, CHP plants are highly promoted for their high rate of energy efficiency (> 90%) and combined with district heating network are a pillar of the EU energy strategy. To un-tap such unexploited reserve of flexibility, and to further enhance turn-down ratio and power ramp capabilities of power oriented CCs, this project proposes the demonstration of an innovative concept based on the coupling of a fast-cycling highly efficient heat pump (HP) with CCs. The integrated system features thermal storage and advanced control concept for smart scheduling. The HP will include an innovative expander to increase the overall efficiency of the HP. In such an integrated concept, the following advantages are obtained: - the HP is controlled to modulate power in order to cope with the CC primary reserve market constraints; - the high temperature heat can be exploited in the district heating network, when available; low temperature cooling power can be used for gas turbine inlet cooling or for steam condenser cooling, thus reducing the water consumption; - in both options, the original CC operational envelope is significantly expanded and additional power flexibility is achieved. In general, the CC integration with a HP and a cold/hot thermal storage brings to a reduction of the Minimum Environmental Load (MEL) and to an increase in power ramp rates, while enabling power augmentation at full load and increasing electrical grid resilience and flexibility.