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Direct air capture (DAC) is a key component in the transition to net-zero society. However, its giga-tonne deployment faces daunting challenges in terms of availability of both financial resources and, most of all, large quantities of low-carbon energy. Within this context, small modular nuclear reactors (SMRs) might potentially facilitate the deployment of DAC. In the present study, we present a detailed thermodynamic analysis of integrating an SMR with solid sorbent DAC. We propose different integration designs and find that coupling the SMR with DAC significantly increases the use of thermal energy produced in the nuclear reactor: from 32% in a stand-alone SMR to 76%-85% in the SMR-DAC system. Moreover, we find that a 50-MW SMR module equipped with DAC could remove around 0.3 MtCO2 every year, while still producing electricity at 24%-42% of the rated power output. Performing a techno-economic analysis of the system, we estimate a net removal cost of around 250 €/tCO2. When benchmarking it to other low-carbon energy supply solutions, we find that the SMR-DAC system is potentially more cost-effective than a DAC powered by high-temperature heat pumps or dedicated geothermal systems. Finally, we evaluate the potential of future deployment of SMR-DAC in China, Europe, India, South Africa and the USA, finding that it could enable up to around 96 MtCO2/year by 2035 if SMRs prove to be cost-competitive. The impact of regional differences on the removal cost is also assessed.

The electrification of naphtha cracking for ethylene production could reduce the associated CO2 emissions but would require significantly larger electricity consumption. Within this context, the flexible operation of electric crackers opens opportunities for improved integration with the future electricity system. In this work, we developed a computationally efficient mixed-integer linear programming model to investigate flexibility in electric crackers, exploring the effect of operational parameters, such as operating envelope, ramping time, and start-up/shut-down time, on costs and emissions. We optimized three electric cracker systems: two with grid electricity consumption (with/without batteries) and one with electricity supply from dedicated renewable technologies. We find that the operating envelope of the cracker has the strongest impact on cost savings, enabling up to 5.5% reduction when using flexible electricity from the grid and 58% for systems with direct coupling to renewables. Moreover, the flexible operation of electric crackers relying on the electricity grid enhances the CO2 emission savings, achieving a 90.4% emission reduction against 54.6% of the constant operation case. Finally, we find that for direct coupling with renewables, electric crackers need to be flexible to avoid suboptimal oversizing of renewable technologies and especially unrealistic battery capacities.

In light of climate change and energy security issues, ambitious decarbonisation targets have been set across Europe. A cornerstone of realising these goals is a massive expansion of offshore wind power located in the North Sea. This area is one of the most favourable locations for successful wind projects in the world, due to a reliable wind resource and shallow waters. Considering announced plans to build upwards of 300 GW of offshore wind in the North Sea, how to best integrate this into the existing onshore energy system remains uncertain. A possible solution that has gained momentum in recent years is the build-out of an integrated transmission network placed offshore. This could transport the energy generated from offshore wind farms via a hub-based system to several nations. The hub-based network can comprise both power and hydrogen transmission infrastructure, as well as electrolysers placed offshore. This project investigated potential configurations of such a hub-based offshore network in the North Sea by 2050, using a linear optimisation model. 2030 and 2040 were set as intermediate simulation years to monitor developments across the time horizon. The results indicate substantial build-out of both power and hydrogen transmission infrastructure, across all modelling runs. It predominantly consists of electricity connections, but hydrogen connections are also present. The electricity network displays both hub-to-hub as well as hub-to-shore connectivity. Major connection points across the offshore power network were found to be the areas around offshore wind farms (OWF) East Anglia, Nederwiek, Dogger Bank, and German search areas N 17-20. The 2050 offshore hydrogen network exhibits hub-to-hub connections between OWFs East Anglia and Nederwiek, and far-from-shore German OWF search areas N 17-20 and British Dogger Bank respectively. All other offshore nodes display the build-out of hydrogen pipelines which are radially connected to the shore.

This study investigates the decarbonization of ammonia production in the Netherlands, which currently accounts for roughly a quarter of the country’s chemical sector emissions. The primary objective is to determine the most cost-effective production route for decar- bonizing the Dutch ammonia industry while taking into account site limitations. The study begins with a comprehensive literature review, providing an overview of vari- ous production technologies for ammonia. Among the alternatives considered, conventional steam methane reforming (SMR) with carbon capture and storage (CCUS), electrified SMR (eSMR) with CCUS and proton exchange membrane (PEM) electrolyzers emerge as the most promising low-carbon routes for ammonia production. To evaluate the viability of these processes, the study collects and standardizes techno- economic data, including information on auxiliary systems. A multi-energy systems (MES) approach combined with mixed-integer linear programming (MILP) optimization is em- ployed to analyze ammonia production at two specific sites: Sluiskil and Chemelot. The research explores four distinct cases to assess the feasibility, capacity, and associated costs of the alternative routes for decarbonizing ammonia production. The first two cases assume unlimited availability of current grid electricity and an imaginary future low-carbon grid electricity, respectively. The third case incorporates the impact of renewable energy re- sources (RES), such as offshore wind (OSW) and solar photovoltaic (PV), while considering limitations in grid electricity imports. The fourth case further incorporates the expansion of electricity networks to examine how the geographical location of ammonia production sites affects decarbonization efforts. The findings indicate that SMR-based ammonia with CCUS can potentially eliminate up to 84% of current emissions. However, achieving further reductions relies on reducing the carbon intensity of the Dutch electricity grid. Further