Design optimisation of pressure vessel bundles for offshore hydro-pneumatic energy storage using a smart design software

With the gradual shift towards renewable energy sources (RES), the ocean is now being recognised as an enormous natural source of clean energy which can supply power ranging from ocean thermal energy conversion (OTEC) to tidal and wave energy. Wind turbines have also been taken out at sea to benefit from the more favourable wind conditions offshore. In fact, offshore wind energy has now become the most technically advanced marine-based technology. The total global installed offshore wind capacity reached 29 Giga-Watts (GW) by the end of 2019, which has been reported to be the best year for the offshore wind industry to date.peer-reviewe

Numerical Modeling of the Thermal Behavior of Subsea Hydro-Pneumatic Energy Storage Accumulators Using Air and CO₂

This paper numerically models the thermal performance of offshore hydro-pneumatic energy storage (HPES) systems composed of a subsea accumulator pre-charged with a compressed gas. A time-marching numerical approach combining the first law of thermodynamics with heat transfer equations is used to investigate the influence of replacing air within an HPES system with carbon dioxide (CO2). The latter is able to experience a phase change (gas–liquid–gas) during the storage cycle in typical subsea temperatures when limiting the peak operating pressure below the critical point. The influences of integrating a piston and an inner liner within the accumulator to mitigate issues related to gas dissolution in seawater and corrosion are explored. It is found that the energy storage capacity of subsea HPES accumulators increases substantially when CO2 is used as the compressible fluid in lieu of air, irrespective of the accumulator set up. It is also noted that the length-to-diameter ratio of the accumulator has a considerable influence on the round-trip thermal efficiency for both air- and CO2-based accumulators. Another factor influencing the round-trip thermal efficiency is the presence of the inner liner. Moreover, the CO2-based HPES system yields a lower round-trip thermal efficiency over that of air

Analysis of the Wave Attenuating and Dynamic Behaviour of a Floating Breakwater Integrating a Hydro-Pneumatic Energy Storage System

Floating breakwaters have recently been generating increasing interest as a vital means to provide shelter and protect the ever-increasing number of structures deployed at sea. Notwithstanding the novel ideas being put forward, to date, floating breakwater deployment has been limited to inshore and shallow water areas. The scale of such structures has been restricted to the smaller spectrum. Furthermore, whilst some concepts to integrate floating breakwaters with other offshore systems have been proposed to benefit from cost-sharing strategies, studies related to floating breakwaters integrating energy storage are lacking in the open literature. The present research investigates the wave attenuating and dynamic performance of a large-scale floating breakwater in deep seas with a hydro-pneumatic energy storage system also integrated within the structure. This article highlights the arising need for floating breakwaters and sheds light on the present-day technological status of floating wave breakers. It then lays the ground for the proposed, novel floating breakwater concept that aims to address the current knowledge gaps in this field of study. The simulation results generated from numerical modelling via the potential flow solver ANSYS® AQWA™ have been promising, connoting that the addition of hydro-pneumatic energy storage to a floating breakwater will not lead to a degradation in the dynamic performance or wave breaking efficiency of the floating structure

Numerical Modeling of the Thermal Behavior of Subsea Hydro-Pneumatic Energy Storage Accumulators Using Air and CO2

This paper numerically models the thermal performance of offshore hydro-pneumatic energy storage (HPES) systems composed of a subsea accumulator pre-charged with a compressed gas. A time-marching numerical approach combining the first law of thermodynamics with heat transfer equations is used to investigate the influence of replacing air within an HPES system with carbon dioxide (CO2). The latter is able to experience a phase change (gas–liquid–gas) during the storage cycle in typical subsea temperatures when limiting the peak operating pressure below the critical point. The influences of integrating a piston and an inner liner within the accumulator to mitigate issues related to gas dissolution in seawater and corrosion are explored. It is found that the energy storage capacity of subsea HPES accumulators increases substantially when CO2 is used as the compressible fluid in lieu of air, irrespective of the accumulator set up. It is also noted that the length-to-diameter ratio of the accumulator has a considerable influence on the round-trip thermal efficiency for both air- and CO2-based accumulators. Another factor influencing the round-trip thermal efficiency is the presence of the inner liner. Moreover, the CO2-based HPES system yields a lower round-trip thermal efficiency over that of air