Energy, exergy, economic and environmental analysis of a regasification system integrating simple ORC and LNG open power cycle in floating storage regasification units

Abstract

A thermodynamic, economic and environmental analysis of a regasification system including a simple Organic Rankine Cycle (ORC) and an Open Organic Rankine Cycle (OC) to utilise the liquefied natural gas (LNG) cold energy is carried out in the present paper. The proposed system, called ORC-OC, uses ambient seawater as heat source (open loop) and is implemented on board a Floating Storage Regasification Unit (FSRU) in order to reduce the greenhouse gas (GHG) emissions associated with the electricity generation plant, i.e., dual fuel (DF) engines. Regarding the ORC working fluids analysed, an ethane/propane zeotropic mixture is applied. The ORC-OC is compared with the simple ORC architecture, giving the first one better energy (lower specific energy consumption), exergy (higher exergy efficiency) and environmental (lower CO2e emissions) results. When compared to the regasification systems installed on board, the ORC-OC system reduces the specific energy consumption by 86.99 % and increases the exergy efficiency by 17.82 % with respect to the most efficient conventional system installed on FSRUs (direct seawater regasification system), leading to a reduction of CO2e emissions of more than 80 %. In addition, the ORC-OC system is more cost-effective than conventional regasification systems when the LNG price is above 6,508 USD/MMBtu.

The decarbonisation of the maritime sector: Horizon 2050

“…This type of fuel, which a few years ago seemed to be overtaken by LNG as the fuel par excellence to lead the energy transition in the maritime sector, has re-emerged due to the rise in gas prices, geopolitical tensions derived from the Ukraine war conflict and changes in alliances between exporting countries. Proof of this is that Alphaliner, with the year 2022 still to close, has already noted a 28% increase over 2021 in dual methanol-gasoil engine vessels [24].…”

“…The main advantages and disadvantages of marine fuels are summarised in Table 2 [20][21][22][23][24][25][26][27][28][29][30]64,68].…”