Today gas turbines and combined cycle power plants play an important role in power generation and in the light of increasing energy demand, their role is expected to grow alongside renewables. In addition, the volatility of renewables in generating and dispatching power entails a new focus on electricity security. This reinforces the importance of gas turbines in guaranteeing grid reliability by compensating for the intermittency of renewables. In order to achieve the Paris Agreement’s goals, power generation must be decarbonized. This is where hydrogen produced from renewables or with CCS (Carbon Capture and Storage) comes into play, allowing totally CO2-free combustion. Hydrogen features the unique capability to store energy for medium to long storage cycles and hence could be used to alleviate seasonal variations of renewable power generation. The importance of hydrogen for future power generation is expected to increase due to several factors: the push for CO2-free energy production is calling for various options, all resulting in the necessity of a broader fuel flexibility, in particular accommodating hydrogen as a future fuel feeding gas turbines and combined cycle power plants. Hydrogen from methane reforming is pursued, with particular interest within energy scenarios linked with carbon capture and storage, while the increased share of renewables requires the storage of energy for which hydrogen is the best candidate. Compared to natural gas the main challenge of hydrogen combustion is its increased reactivity resulting in a decrease of engine performance for conventional premix combustion systems. The sequential combustion technology used within Ansaldo Energia’s GT36 and GT26 gas turbines provides for extra freedom in optimizing the operation concept. This sequential combustion technology enables low emission combustion at high temperatures with particularly high fuel flexibility thanks to the complementarity between its first stage, stabilized by flame propagation and its second (sequential) stage, stabilized by auto-ignition. With this concept, gas turbines are envisaged to be able to provide reliable, dispatchable, CO2-free electric power. In this paper, an overview of hydrogen production (grey, blue, and green hydrogen), transport and storage are presented targeting a CO2-free energy system based on gas turbines. A detailed description of the test infrastructure, handling of highly reactive fuels is given with specific aspects of the large amounts of hydrogen used for the full engine pressure tests. Based on the results discussed at last year’s Turbo Expo (Bothien et al. GT2019-90798), further high pressure test results are reported, demonstrating how sequential combustion with novel operational concepts is able to achieve the lowest emissions, highest fuel and operational flexibility, for very high combustor exit temperatures (H-class) with unprecedented hydrogen contents.

In order to minimize the footprint of human activities on the environment, technologies to reduce greenhouse gases while meeting constantly growing electricity demands are critical. Amongst the various sources of energy production, Gas Turbines (GT) are an efficient way to stabilize the grid with regards to renewable sources like wind and solar energies. The demand for higher efficiency, higher power output while reducing emission levels (especially NO and NO2) at high loads, and for higher flexibility within the H-class Gas Turbine market is thereby a natural consequence. The development and validation of a two-stage sequential combustor, so-called Constant Pressure Sequential Combustion (CPSC) system, to achieve these goals has been accomplished by Ansaldo Energia. The CPSC consists of a premix burner system (First Stage) and of a sequential burner (SB) in series within a can combustor. At the 2017 and 2019 ASME conferences, high pressure test rig validation results of the CPSC were introduced. The advantages with regards to fuel flexibility, hydrogen combustion and low emissions at high firing temperature were presented [1,2,3,4,5]. This article focuses on the validation of the combustor performance in Ansaldo Energia’s Validation Power Plant located in Birr, Switzerland, which includes detailed validation from ignition to full speed no load, part load operation and full load over various ambient and engine thermal state conditions. To allow for detailed validation, dedicated fully instrumented combustor cans were installed in the GT. Detailed validated air distribution and emission models support the results obtained on the engine. Ignition and ramps up to full speed no load have been validated with large variations of the first combustor stage firing temperature to minimize power consumption and start-up time. The potential of the CPSC with regards to turndown capability, with minimum environmental load (MEL) below 25% GT load while keeping CO levels low has been confirmed. The MEL can be kept low over a wide range of ambient temperature and fuel compositions by adjusting the inlet temperature of the sequential burner. Low NOx values were achieved at baseload and peak firing temperature. The operational flexibility and stability of the premixed first stage combustor over the load range and over a large variation of combustor inlet plenum pressures was as well validated along with the operation concept of the gas turbine.

Modvion develops modular wind turbine towers made of wood. The application requires strong and stiff connections and to achieve the desired performance, a hybrid connection with perforated steel plates slotted into LVL modules is used. The parts will be glued together on site, using a polyurethane adhesive (PUR), providing high strength and stiffness to the connection. This paper presents a preliminary screening on how temperature and relative humidity of the surrounding air during assembly and curing will influence the strength of the bond glued on-site. Static tests were performed on the hybrid connections which were glued and cured in different climates. Tests were also performed at different hardening times to evaluate strength growth in the studied climates. The test results show that at cold temperatures of 9 °C to 12 °C there is a breakpoint where the rate of strength growth starts to decline. The experiments show also that the relative humidity may influence the final strength of the bond. However, the low number of tested specimens brings uncertainties to this observation. High temperatures up to 27 ºC and dry climates down to 20% RH did not impact the strength of the tested hybrid connections.

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