Competitive power production from industrial surplus heat

The COPRO project has made advancements in industrial waste-heat-to-power conversion on topics related to optimal design of key components and cycles for low-to-medium temperature heat sources. Through analysis and evaluation of industry-specific case studies, a better understanding has been brought forward on both cost considerations and the complex effects, practical constraints and interactions caused by integrating heat-to-power system into core processes. Industry partners Alcoa, Hydro, and Equinor represent end-user processes that the case studies were based on. GE Power Norway and FrioNordica contributed as technology providers, and SINTEF Energy Research, NTNU and KTH have been the research partners. The rationale behind the project concept was the lack of attractive options for surplus heat utilization leading to vast amounts of industrial surplus heat being dumped to the ambient. Surplus heat recovery and re-utilization is therefore of great significance, and has the potential of being a major factor in reaching national and international energy and environment goals. Direct re-use of surplus heat would be the most efficient and cost-effective alternative, but is in many cases not a feasible option, for example due to lack of appropriate heat demand within reasonable geographical proximity. This is typically the case for Norwegian energy intensive industries, and thus heat-to-power conversion becomes the remaining alternative for large scale utilization. Several commercial technologies and system concepts for waste heat to power conversion exist, but so far practical implementations have been held back by high costs compared to the electricity produced. The project has considered recovery of industrial waste heat in the range of 125-250 °C, a temperature range where profitable energy recovery currently is challenging. COPRO research efforts and results can be broadly categorized within: * Why: understand why the techno-economics for typical projects are challenging * What: identify the combination of required technology performance and industrial conditions needed for attractive cases * How: define realistic industry scenarios, explore possibilities for technology optimization, and contribute to closing the identified gaps The goal of the COPRO project has therefore been to therefore develop knowledge, tools and methods that can be used to improve the competitiveness of heat-to-power conversion in the industry, more specifically by: 1) Identifying promising industry scenarios, and understand the impact energy recovery will have on the entire system 2) Optimize system and component designs for these specific industry scenarios, while considering heat-to-power performance, overall system impact, practical constraints and costs Research topics have included power cycle layouts and configurations, working fluids and -mixtures, design optimization of heat exchangers, turbines and expanders, cost evaluations, and present and expected future industrial conditions. Focussing the research around specific case studies has been very beneficial and effective, and served two main purposes: * Ensuring that developed technology obtains the highest possible relevance to the industry who will be future end-users, by including concrete industry specific conditions and constraints * Enabling technology evaluation under realistic conditions and system boundaries, on a format that is familiar and relatable to the target industry Key project results include final case evaluations for "Aluminium electrolysis off-gas energy recovery" and "Offshore export gas compression energy recovery" cases. The aluminium case study included cost evaluations and -optimization, while system weight was minimized in the offshore case. Proposed optimized concepts for both cases indicated cost-benefit interesting for further development. New topics has been identified for future work, within further competence building, industrial integration and validation of methodology, and practical demonstration of new technology concept. The project's PhD candidate at NTNU is on track to finish within 2020. His work on turbine modelling and development has led to broad international cooperation that includes research stays at the Technical University of Delft (2018), and Queen Mary University of London (2019). There has also been collaboration with Politecnico de Milano, Technical university of Munich, and London Imperial College. In addition, 5 MSc students, 5 project students, and 3 summer-research internships have worked directly linked to the project.

Partnerne i COPRO har fått en utvidet forståelse av kraftproduksjon fra overskuddsvarme i egne industriprosesser. Denne forståelsen muliggjør å vurdere utnyttelse av overskuddsvarme i samspill med påvirkningen på kjerneprosessen, noe som gjør at potensial og gevinster kan maksimaliseres og mulighetene for praktisk implementering øker. Industripartnerne rapporterer at prosjektet har synliggjort forbedringspotensialet på egne anlegg og prosesser, og gitt innsikt i potensielle muligheter, begrensninger og effekter ved implementering av de undersøkte konseptene. Bidraget til å utdanne en rekke studenter og yngre forskere på den konkrete tematikken trekkes også frem som en viktig effekt - nye eksperter utgjør et rekrutteringsgrunnlag til industrien og er et svært kraftig virkemiddel for kunnskapsoverføring.

Profitable industrial waste heat recovery is key to reducing industrial energy consumption while also reducing operating costs. COPRO addresses this through the development of heat-recovery power cycles with mixed working fluids (hydrocarbons, CO2, N2). These working fluids have non-isothermal evaporation, meaning that they are well suited for heat recovery from industrial liquids and gases. The target is to optimize the mixture so that the heating curve of the working fluid follows the cooling curve of the industrial heat source. This phenomenon in combination with adapted heat-exchanger and turbomachinery design will result in higher heat recovery efficiency. Cost can be reduced provided that working fluid mixture, components and process design are optimized together. Efficient numerical algorithms for multivariate optimization will be integrated in the heat-to-power process simulations, for simultaneous optimization of components and power process when using most suitable working fluid mixtures. Also, part-load performance and transient behaviour will be simulated. COPRO primarily targets recovery of industrial waste heat in the range of 125-250°C, which is a temperature range where profitable energy recovery currently is challenging. Promising heat-to-power cases for plants owned by the COPRO partners Alcoa and Hydro will be investigated in detail (both prototype and full-scale waste heat-to-power). Corresponding scenarios for the partners' future-technology energy-intensive plants will be evaluated. The potential for specific investment cost reduction compared to present technologies will be documented. This will enable quantification of the fulfillment of the overall COPRO objective, which is to develop superior cycle and component concepts that improve the attractiveness and competitiveness of moderate (125-250°C) heat to power conversion in industry.