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The waste heat potentially available from a wide range of industrial processes still represents a significant fraction of the primary energy consumption related to the processes. Some of the most energy intensive processes can be categorized in the iron, steel and glass production, the fine chemical industry, and the production of non-ferrous materials such as cement, polymers, paper or in the textile industry. Of the overall thermal energy rejected in the environment, a part of it is feasibly exploitable from a technical and economical point of view in waste heat recovery plants. This work proposes innovative solutions for waste heat recovery cycles working with sCO2 cycles and transcritical cycles adopting CO2-mixtures. As the heat rejection from these cycles is non-isothermal, these power plants are particularly suitable to be used in CHP configuration, therefore transferring heat to a stream of pressurized water at high temperature, up to 200°C. When a waste heat source available at 450°C is considered, assuming a stack temperature of 125°C, the proposed sCO2 power cycle can convert around 12% of the thermal input in electricity and 87% in useful heat above 60°C, while a cycle working with the CO2+Acetonitrile mixture can deliver 15.5% of the thermal input in electricity while still recovering the remaining more than 80% in useful heat above 60°C. CO2 based mixtures are therefore suggested for power cycles in CHP configuration to reach nominal electric efficiencies higher than sCO2, avoiding the consumptions of natural gas to produce the same amount of electricity and heat with separated systems., Conference Proceedings of the European sCO2 Conference5th European sCO2 Conference for Energy Systems: March 14-16, 2023, Prague, Czech Republic, p. 169

The present work investigates the part-load performance of a MW-scale sCO2 power plant designed as heat recovery unit for an existing cement plant located in Czech Republic, in the framework of the H2020 funded project CO2OLHEAT. The study firstly presents the selected power plant configuration and then focuses on the evaluation of its part load operation due to variation of flue gas mass flow rate and temperature. The range of flue gas conditions at the outlet of the upstream process is retrieved from a preliminary statistical analysis of historical trends obtained through the cement plant monitoring. The numerical model developed for this study aims at providing realistic results thanks to the adoption of turbomachinery performance maps provided by the project partners. Moreover, heat exchangers have been modelled through a discretized approach which has been validated against manufacturer data, while piping inventory and pressure losses have been assessed through a preliminary sizing that considers the actual distances to be covered in the cement plant. Performance decay is estimated for the whole range of flue gas conditions, reporting the most significant power cycle parameters, and identifying the main causes of efficiency loss. The part-load analysis is carried out considering a constant CO2 inventory, in order to reduce the system complexity and capital cost and simplify plant operation. Results show that the operation entails minor variation of the compressors operative points in the whole range of operating conditions of the cement plant, avoiding the risk of anti-surge bypass activation. Moreover, the plant is able to work at nearly constant thermodynamic cycle efficiency (20.5%-23.0%) for most of the year and benefits from part-load operation in terms of overall performance. These predictions will be used, in next steps of the project, to guide the definition of power plant control during transients related to changes of upstream process conditions or specific needs of power output control, Conference Proceedings of the European sCO2 Conference5th European sCO2 Conference for Energy Systems: March 14-16, 2023, Prague, Czech Republic, p. 179

Small-scale Organic Rankine Cycles (ORCs) represent a promising technology for waste heat recovery (WHR) from internal combustion engines (ICEs) for transport applications, due to their remarkable potential, especially on��board of innovative long-haul trucks. Despite market leader companies have already proved its effectiveness, detailed system design procedures are scarcely available in the open literature and proposed solutions are often more simplified with respect to current industrial state��of��art. The present work describes a methodology to include within the ORC design and optimization procedure an efficiency map of the turbo��expander, retrieved exploiting a mean line reduced��order method developed in��house. The developed ORC optimization algorithm allows to consider any working fluid in available thermodynamic databases and can investigate multiple cycle architectures. The approach proposed allows to design the thermodynamic cycle considering a realistic performance of the expander and to retrieve the best cycle architectures and turbine geometry depending on the heat source characteristic and active constraints. Methodology is applied to two WHR applications of different sizes highlighting the impact of adopting efficiency maps for the turbine within the cycle optimization procedure rather than assuming fixed efficiency values.

The present work focuses on the analysis of a novel coal fired sCO2 power plant concept developed in the frame of sCO2-Flex H2020 EU funded project. Fossil fuel fired power plants are expected to improve their flexibility in the future energy scenario characterized by a large share of non-predictable and non-dispatchable renewable energy sources. This upcoming context requires a new generation of coal fired power plants with a smaller size, a high flexibility and minor requirements for the installation site like no need of water consumption. Carbon dioxide in supercritical cycles is recognized to be a possible solution for this technology shift and could replace in the future common steam Rankine cycles. This paper focuses on the impact of ambient temperature variation on a small size coal fired sCO2 power plants equipped with a dry cooling heat rejection unit, with the aim of understanding the effect on plant operability and system performance. A dedicate tool is implemented for off-design behavior assessment and different control strategies are investigated. Results show that without a proper design of the heat rejection unit a small increase of ambient temperature may drastically limit the maximum attainable power output of the plant. This penalizing effect is more pronounced in hot locations, but this issue can be limited by adopting a sufficient over-sizing of the cycle heat rejection unit (HRU) or wet-and-dry solutions., Conference Proceedings of the European sCO2 Conference4th European sCO2 Conference for Energy Systems: March 23-24, 2021, Online Conference, p. 379

The Organic Rankine Cycle (ORC) is a thermal driven power cycle operated with an organic working fluid. It is especially suitable to exploit low to medium temperature heat sources at small to medium size capacity ranges. For these conditions, it outperforms the standard Clausius Rankine Cycles. Suitable heat sources can be either renewable in nature (i.e. biomass, solar, geothermal) or waste heat (i.e. mobile, stationary). The size of these power units ranges from very few kW to several dozen MW. It is the intention of this report to present an up-to-date overview on the recent developments in the ORC industry. This publication provides insights on the number and capacity of most of the installed ORC plants worldwide as well as the current and future market expectations from ORC manufacturer���s perspective. Information from 30 manufacturers, representing a total of more than 2600 projects have been collected and analyzed providing information on trends in the past and the market evolution during the last four years in terms of installed capacity and installed plants divided by application, macro region and manufacturer. At the end of 2020, the cumulated ORC installed capacity was 4.07 GW. Since 2016, the overall ORC market increased by 40 % (+1.18 GW) in terms of installed capacity and by 46 % (+851) in terms of installed plants. Regarding the capacity increase between 2016 and 2020, the largest increase is due to geothermal application (+970 MW, +45 %), while waste heat systems have the largest growth concerning the number of installed systems (628 plants, + 207 %). For the market survey, ten established ORC manufactures contributed their current and future perspective on the ORC market. The results highlight that, despite the impact of the COVID-19 situation, the current market situation is in good shape and that the majority of the manufacturers have positive expectations concerning the short-term development of both the ORC market and number of employment. Central and Eastern Europe as well as the ASEAN region are rated as the regions with the highest growth potential. Geothermal energy and small waste heat sources are seen as the most relevant heat sources for the coming years.

Conference Proceedings of the European sCO2 Conference3rd European Conference on Supercritical CO2 (sCO2) Power Systems 2019: 19th-20th September 2019, p. 68