The ocean plays a key role in sustaining life on our planet and is inextricably linked to biodiversity, climate, human well-being, and health. However, the governance of the ocean is primarily pursued through sectoral-based legal and institutional frameworks that falls short in ensuring the long-term protection of the marine environment and the sustainability of marine resources. This is especially concerning in areas beyond the limits of national jurisdiction (ABNJ) where human activities continue to expand. The existence of two distinct regimes in ABNJ, namely the High Seas (applicable to the water column, which is a global common) and the Area (applicable to the international seabed and its mineral resources, which are the common heritage of mankind), that have been largely regulated separately, impede the development and implementation of integrated marine environmental governance and biodiversity conservation in ABNJ. On the one hand, the International Seabed Authority (ISA), which is mandated to administer the mineral resources of the Area, is currently discussing a set of regulations to enable future exploitation activities. On the other hand, multilateral negotiations are taking place for the development of an internationally legally binding instrument for the conservation and sustainable use of marine biodiversity in areas beyond national jurisdiction (referred to as the proposed ‘BBNJ’ Instrument). Both processes offer a unique opportunity to foster an ecosystem approach to management (EAM) in ABNJ. In this article, we elaborate on options for stronger governance integration and the development of a coherent and collaborative interplay between these two processes. To this end, we explore the potential of Regional Environmental Management Plans (REMPs) established by the ISA as a case study to contribute to global biodiversity conservation, and the opportunity for the proposed BBNJ Instrument to promote overarching coherence to biodiversity conservation in ABNJ, premised on EAM. We conclude that the proposed BBNJ Instrument could have a pivotal role to streamline multilateral action for the conservation of biodiversity in ABNJ by adopting an ambitious, overarching environmental vision and strategic goals, accompanied by strong implementation and enforcement mechanisms.

We studied the heat transfer of finned heat exchanger configurations with a novel design. These novel fin designs use integrated pins to enhance the heat conduction from the fin base to the fin tip as well as the air-side heat transfer on the fin surface. Oval tubes with conventional circular plain fins (CPF) as well as novel circular integrated pin fins (CIPF) and serrated integrated pin fins (SIPF) were additively generated by a Selective Laser Melting (SLM) process and installed at the bottom of a 6.5 m long chimney. All heat exchanger designs were tested in a 2-row and 3-row configuration with Rayleigh numbers between 25,000 and 120,000. We found the average Nusselt number of SIPF to be higher and the Nusselt number of the CIPF to be lower than for the CPF. Moreover, the 2-row configuration achieved a higher Nusselt number compared to the 3-row configuration for all heat exchanger designs. The analysis of the individual tube rows showed the highest Nusselt numbers at the first tube row and the lowest one at the last tube row for both configurations. However, for the SIPF the difference between the first and second tube row is smaller compared to the CPF and CIPF. In order to evaluate the compactness of the heat exchanger, the volumetric heat flux density was considered. Similar to Nusselt number the volumetric heat flux density enhanced for the SIPF and reduced for the CIPF compared to the conventional design. Also the 2-row configuration reached greater thermal performance compared to the 3-row configuration. Additionally, the volume and the surface area of the heat exchanger are 6.9% and 30.7% lower for the SIPF compared to the CPF. The experimental data were used to develop an empirical heat transfer correlation between Nusselt number, Rayleigh number, fin design and tube row number.

Power-to-gas-to-power technologies incorporating electrolysis, methanation, SNG-fired Allam cycles and subsurface storages allow for a confined and circular use of CO ₂ /CH ₄ and thus an emission-free seasonal storage of intermittent renewable energy.