Elsevier

Ocean Engineering

Volume 76, 15 January 2014, Pages 152-162
Ocean Engineering

Investigation of offshore thermal power plant with carbon capture as an alternative to carbon dioxide transport

https://doi.org/10.1016/j.oceaneng.2013.07.016Get rights and content

Highlights

  • Concepts for the offshore thermal power plant with CCS (OTPPC) are introduced.

  • General design selection process is established.

  • Cost analysis with case study also performed.

Abstract

Carbon Capture and Storage (CCS) technology is considered as one option to reduce CO2 emissions in order to mitigate climate change. The conventional CCS technology has its own complications including high costs and risks for storing CO2. This paper introduces the concept of Offshore Thermal Power Plant with CCS (OTPPC), which eliminates the needs for transporting CO2 and therefore reduces the complications of the whole system. A general design selection process for the OTPPC is established. A case study is carried out to demonstrate the application of OTPPC and the cost-effectiveness of this concept is evaluated by calculating the Levelised Cost Of Energy (LCOE) for both the OTPPC and conventional CCS technology for an onshore power plant with assumption that CCS is necessary.

Introduction

Carbon Capture and Storage (CCS) is considered as one option in the portfolio for mitigating climate change that is mainly caused by the large anthropogenic emissions of CO2 from burning fossil fuels (IPCC, 2005, IPCC, 2007a, IPCC, 2007b, IPCC, 2007c, IPCC, 2007d). According to the International Energy Agency (IEA), fossil fueled power generation accounts for 41% of the total emissions of CO2 (IEA, 2011). Therefore, many researches focus on the capture of CO2 emitted from power generation and the subsequent transport and storage of CO2.

However, the conventional CCS technology has its own complications, such as high energy penalty, high costs, technology immaturity, the complexity of transporting CO2 and uncertainties in the long-term storage of CO2 (IPPC, 2005). Although transportation of CO2 does not contribute to the largest part of the total costs, it increases the complexity of the whole system and therefore increases risks for leakage. In addition, the current CCS technologies mainly focus on the pursuit of CO2 storage in onshore geological formations, which may lead to the concerns from the public towards the safety of storing CO2 underground. However, the concept of Offshore Thermal Power Plant with CCS (OTPPC) may eliminate the above problems, which moves the power plant offshore to facilitate storing CO2 into offshore geological formations.

The concept of offshore thermal power plant is not really new in the literature. Many companies have shown interest in developing this concept in order to reduce the need for lengthy permitting applications that are needed for conventional land based power plants (Waller Marine, 2011). In addition, the Gas to Wire (GTW) concept provides an attractive solution for marginal gas fields and stranded gas. Instead of transporting the natural gas from marginal gas fields to an onshore terminal, it generates electricity offshore and then transmits the electricity via subsea power cables to onshore electricity grids, which generates a higher thermal efficiency compared with the conventional approaches (HITACHI, 2011). The concept of combining an offshore power plant with CCS has been addressed previously when considering power generation for offshore installations since the 1990s (Bjerve and Bolland, 1994). A more recent concept is by Hetland et al. (2008). The SEVAN GTW concept, developed by SEVAN MARINE and Siemens is a cylindrical platform equipped with a combined cycle power plants with four blocks, each consisting of two gas turbines and one steam turbine. These are connected to an amine based carbon capture system (Hetland et al., 2009). However, the cost benefits of this concept have not been investigated before. This raises the question whether OTPPC is cheaper than the conventional CCS technology for power plants.

Hence, the main purpose of this paper is to illustrate the concept of offshore thermal power plant with CCS, establish the corresponding design selection process and evaluate this concept in terms of availability for application and cost-effectiveness.

The concept of an OTPPC involves integrating power generation equipment, gas processing equipment, carbon capture systems and electricity transmission modules onto one offshore platform (Windén et al., 2011). As with the GTW concept, OTPPC can be applied in marginal gas fields where the high costs of production and transportation of gas make such developments non-viable. Compared to onshore power plants, offshore power plants have the advantages of shorter construction periods (Waller Marine, 2011) and ease of mobility. In addition, the cost of natural gas may be significantly reduced since natural gas can be directly supplied from the existing offshore gas fields as shown in Fig. 1.

Different from conventional CCS technology for power plants, this concept eliminates the need for long distance transportation of CO2 via pipelines or ships by directly capturing CO2 from fuel gases and injecting it into offshore geological formations. The generated electricity can either be transmitted to onshore electricity grids via subsea power cables or be used to support other offshore operations (Hetland et al., 2009).

This section has introduced the concept and features of an OTPPC, the design process of which is discussed in Section 2. A case study, discussing the cost-effectiveness of an OTPPC is given in Section 3. Finally, concluding remarks are given in Section 4.

Section snippets

Design selection process

Like the other offshore platforms, the OTPPC has to be capable of operating and surviving in the offshore location for a long period. Therefore, it is important to evaluate the environmental load effects based upon a given site in the design stage. Design codes and regulations that are applicable for offshore platforms may also be adapted to guide the design of the OTPPC. However, the OTPPC has its own complications and limitations. By integrating different systems onto one platform, the

Application of the OTPPC

This section introduces the application of an OTPPC in terms of complexity and cost-effectiveness. A case study was performed in this section by following the design selection process as shown in the previous section. The costs for both the OTPPC and the conventional onshore power plant were calculated and compared under the assumption that CCS is necessary and offshore geological storage of CO2 is pursued for both offshore and onshore power plants.

Concluding remarks

This paper mainly introduced the concept of offshore thermal power plant with CCS (OTPPC) and established the general design selection process and design considerations. A case study based in Western Australia was carried out by following the design selection process in order to demonstrate the application of the OTPPC. In the case study, some aspects of the design had to be based on assumed values of cost and size since no data was available. In such cases, buffers have been added so the final

Acknowledgments

The work presented in this paper was funded by Lloyd's Register Foundation (LRF). Lloyd's Register Foundation supports the advancement of engineering related education, and funds research and development that enhances safety of life at sea, on land and in the air. Special thanks give to Mr. Michael Franklin, the director of The LRF. Also, especially thanks are given to Mr. Simon Reeve and Mr. Magnus Melin for giving us a very useful overview of CCS in the initial stages that has followed us

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