An investigation into the logistical and economical benefits of using offshore thermal power in a future CCS scheme

Abstract

Carbon Capture and Storage (CCS) is an increasingly popular scheme to mitigate CO2 emissions from large point
sources (IPCC 2005). Thermal power plants account for a large portion of the world’s total CO2 emissions and are
therefore the most attractive target for CCS. For a typical thermal power plant; the process would involve capturing
the CO2, transporting it to a suitable location for storage and storing it in a manner that will ensure minimal leakage
over a very long period of time. Due to public concerns and protests regarding storage onshore, offshore geological
storage of CO2 is most likely to be used for future projects (Windén et al. 2011). The successful implementation of CCS thus depends on the feasibility of capturing the CO2, transporting it to an offshore site and injecting it deep beneath the seabed. Pilot projects such as the Sleipner rig in Norway have already proven the feasibility of using offshore geological storage and post combustion technology for capturing CO2 can also be considered mature. No long distance, large scale transportation solutions for CO2 has yet been proven to work with satisfactory results. Transportation of CO2 is thus identified as an area where breakthroughs could lead to forward leaps in mitigating greenhouse gas emissions. This paper presents a study on a possible future way of solving CO2 transportation issues associated with the use of CCS.

Geological storage locations are located in the sedimentary basins which is where oil and gas reserves are also found. The issue of transporting CO2 from an onshore power plant to an offshore storage site can thus be compared to the issue of transporting natural gas from an offshore extraction site to an onshore power plant or production facility. This is conventionally done using either ships or pipelines. This paper investigates the cost competitiveness of using the third alternative of Gas To Wire (GTW) where the gas is combusted offshore. This eliminates the need for transportation altogether and the concept has already been proven to be attractive for exploiting certain gas fields. It is shown here that the concept is even more attractive in a scenario where CCS is used since it eliminates two transportation issues. In this study, the transportation cost of natural gas and CO2 is compared to the costs of sub-sea High Voltage Direct Current (HVDC) electrical cables and is shown to be higher. Pipelines have a large potential to be the most economical way of transporting CO2 to most prospective storage sites in the future (Windén et al. 2011) and will therefore be used to represent a conventional method of CO2 transportation in this study. For comparison, the alternative of transporting by ship or using a pipeline-ship combination will also be presented briefly. Initial studies show that the reduction in transportation costs compared to all conventional methods would more than offset the increased costs of operating a power plant offshore. It is also shown that the gains in transportation cost will decrease the Levelised Cost Of Energy (LCOE) for an example scenario located in Western Australia. This work has been carried out as a part of the Lloyd's Register Educational Trust Collegium of 2011.

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ORCID for P.A. Wilson: orcid.org/0000-0002-6939-682X

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