Near zero emission energy export and electric power supply based on natural gas
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In this study, a techno-economic analysis of value chains/cases for near zero emission energy export and power supply to Continental Europe, based on natural gas extracted in Norway and integration of carbon capture and storage (CCS) technology, is done. The objective of the study is to, based on a technical and an economic analysis, evaluate optimal value chains for near zero emission energy export and power supply based on natural gas. Norway possesses vast energy resources, and export of natural gas is essential for the country´s economy. An increased focus on reducing CO2 emissions is however forcing the fossil energy industry to pursue new solutions. The results of this study indicate that some of the value chains evaluated, represent viable and carbon-lean opportunities for energy export from Norway based on natural gas. Each of the value chains/cases evaluated in this study consist of systems for energy conversion with CO2 capture, energy transport, CO2 transport and CO2 storage. The energy conversion systems with CO2 capture evaluated are: Natural gas combined cycle (NGCC) power plant with post-combustion CO2 capture. Steam reforming of natural gas to hydrogen with pre-combustion CO2 capture/separation, and power generation in a hydrogen-fired combined cycle power plant. Oxy-fuel combustion of natural gas in NGCC power plant with post-combustion CO2 capture/separation. Transport of natural gas by subsea pipeline, transport of H2 gas by subsea pipeline or in liquid state by ship, transport of H2 as ammonia in liquid state by ship, transport of H2 by a liquid organic hydrogen carrier (LOHC), and transport of electric power by subsea high voltage direct current (HVDC) cable, are the energy transport methods considered in this study, to transport energy from Norway to Europe. Transport of liquid CO2 by ship and transport of CO2 by subsea pipeline are the methods for CO2 transport evaluated. It is assumed that CO2 is to be geologically stored in an offshore aquifer in Norway. The cases have been evaluated based on energy efficiency, CO2 emissions, costs, technical maturity, risks, complexity and political factors. Aspen HYSYS is used to analyse various sub-processes in the cases evaluated to find the respective energy needs, and the CO2 production rates. Eight cases, including a reference case without CCS, and four sensitivity cases have been analysed in this study. From the results of the analysis, it is clear that all the cases evaluated have pros and cons. The evaluation therefore depends on how the different criteria evaluated are emphasized. If environmental impact, hence low CO2 emissions, are emphasized, some of the cases that utilize pre-combustion CO2 capture technology are favourable. The cases that utilize pre-combustion CO2 capture are however considered to have a high level of risk and complexity, low technical maturity and low energy efficiency. This is due to energy intensive processes, many energy conversion steps, need for new/untested technology, and safety risks related to H2-, NH3- and LOHC- handling.If energy efficiency, technical maturity, risks, complexity and costs are emphasized, the cases that utilize post-combustion CO2 capture are favourable. These cases have high energy efficiencies and few energy conversion steps compared to the other cases evaluated. The technology that is utilized for energy conversion, CO2 capture and energy transport in these cases is also relatively mature. The cases that utilize oxy-fuel combustion are in the mid-range between the post-combustion- and the pre-combustion cases in terms of energy efficiency, complexity and risk. Upscaling of gas turbines for oxy-fuel combustion, and facilitating for production and use of concentrated O2, are important challenges that needs to be addressed for the further development of the oxy-fuel configuration. The case where natural gas is transported to Europe by subsea pipeline, a NGCC power plant with post-combustion CO2 capture is used for power generation, and liquid CO2 is transported to Norway by ship, is a favourable case both technically and economically. Pipeline transport of CO2 from Europe to Norway is however more energy efficient, and better for the environment in terms of CO2 emissions, than ship transport of liquid CO2. The post-combustion CO2 capture case where a NGCC power plant is used for power generation, and energy is transported by HVDC cable to Europe, is the most favourable case evaluated in this study. This case has lower CO2 emissions than the other cases with post-combustion CO2 capture evaluated, because no ship transport is required and no electric power is imported from the European power grid. This case also has the lowest cost of CO2 avoidance of all the cases evaluated. Downsides are however the amount of CO2 emitted compared to the cases with pre-combustion CO2 capture, the upscaling of the HVDC cable required, and the cost of the HVDC cable.