Cost-efficient CO2 capture, transport and storage

Munich / Amsterdam. Innovative carbon capture and storage (CCS) technologies aim to make coal-fired power stations more climate-friendly. At the Power-Gen Europe conference and exhibition in Amsterdam, TÜV SÜD presents an integrated service package for safe and cost-efficient CCS strategies. From 8 to 10 June 2010, manufacturers and owners/operators of technical plants can inform themselves about the optimum approach to carbon dioxide capture, measurement and storage (Hall 1, Stand F 70).

TÜV SÜD supports plant manufacturers and owners/operators throughout the process chain of CCS implementation and provides a host of services, from integrated life cycle and risk assessments to ensure cost-efficient CCS retrofitting to assistance with measurement during CO2 transport. Further services include support and assistance during approval of the overall systems from carbon capture to transport and storage.

CCS systems: integration into the overall power station

"While capture and storage of the carbon dioxide contained in the flue gas of power stations (CCS) offers the potential of a clear cut in direct greenhouse gases, it also presents plant owners/operators with special challenges in ensuring its technologically safe and cost-efficient implementation", explains Hans Christian Schröder, Power Station Sector Manager at TÜV SÜD Industrie Service GmbH. The costs of retrofitting an existing 800 MW power station with post-combustion CCS, for example, add up to between EUR 300 and 400 million – almost half of the investment costs spent on the power station itself. According to Schröder, integrated assessment of the life-cycle costs and the risks involved in retrofitting are therefore indispensable for the cost-efficient integration of CCS. Assessment also includes aspects such as servicing and maintenance, plant availability, transport system and suitable storage facilities – including their technical components such as absorbers, heat exchangers or carbon compressors. The power station expert points out that the technology also involves higher operating costs, in addition to the special investment costs. At present, the chemical processes required for a flue-gas volume of three million cubic metres, for example, may cause costs of up to 3,000 euros per hour. The majority of these costs are associated with the periodic replacement of the "CO2 scrubbing agent".

Transport pipelines: Measuring the CO2 mass flow rate and purity

"The capture and long-term storage of carbon dioxide only makes good economic sense if combined with a suitable transport system", explains Walter Pfundt, expert for construction monitoring at TÜV SÜD Industrie Service. Storage reservoirs are only very rarely located in the vicinity of the power stations. "Pipelines are among the safest and most-efficient industry-scale solutions for CO2 transport", continues Pfundt. For transport, CO2 is liquefied under high pressure. Currently existing pipeline systems are unsuitable for this application. As the pressure may be as high as 200 bar, the pipes need to have other dimensions and thicker walls than those used in the natural gas grid (where the pressure reaches between 60 – 100 bar). In addition, the pipeline systems need to have several injection points.
One of the key challenges in the pipeline transport of CO2 lies in the exact determination of the mass or volume flows, the concentration, and the purity of the highly compressed gas. Constant monitoring of the captured, transported and compressed volume of CO2 is indispensable to ensure the rapid detection of leakage, but also for emissions trading. In a study commissioned by the German Environment Agency, TÜV SÜD Industrie Service assessed the state of the art in measurement systems and described the challenges still to be solved. The European monitoring and reporting guidelines for emissions trading, for example, require measurement uncertainty of less than 1.5 per cent. The measurement instruments used must therefore offer excellent measurement accuracy and corrosion resistance and cause only minor pressure loss. "The example of a typical German coal-fired power station with average output shows that uncertainties may significantly impact on emissions trading", notes Kathrin Petrat, head of the CCS innovation project at TÜV SÜD Industrie Service. "At the current rate of around 15 euros per tonne of carbon dioxide, measurement uncertainty of one per cent would add up to as much as 1.2 million euros in certificates in a power station emitting eight million tonnes of CO2 annually."

Storage: Monitoring using satellites and combined technologies

After the CO2 is captured from the flue gas and transported, it is to be sequestered in deep geological formations such as depleted oil and gas fields or saline aquifers (porous layers of rock containing salt water deep underground).
"Reliable monitoring of underground CO2 storage requires the correct combination of a host of different technologies, including monitoring instruments underground but also near-surface and atmospheric monitoring systems", emphasizes Petrat. "A sufficient number of intelligently positioned measuring systems that are activated at suitable intervals is critical."

In line with the European CCS Directive, monitoring of the storage sites must cover the injection points and provide information concerning the underground migration paths and pressure behaviour of the carbon dioxide. The cost-efficient extensive monitoring of underground CO2 storage may be realized with radar satellites, for example. Within the scope of a research project of the European Space Agency (ESA) under the management of the EADS subsidiary Infoterra and with the participation of a leading German energy supplier, TÜV SÜD evaluated this method and compared it with other possible monitoring techniques. Benchmarking criteria included informative value, costs and technological maturity. Experience so far has shown that CO2 compression and the pressure in the underground storage area cause minimal surface elevations. Under ideal conditions, radar interferometry of radar satellite images taken at different times can show these elevations in a three-dimensional perspective to the millimetre, demonstrating lateral areas where pressure is increased due to CO2 migration. This technique enables better targeting and improved cost-efficiency of complementary geophysical near-surface or underground analysis.

TÜV SÜD supports CCS projects by providing integrated system analyses and combined technical, business, geological and legal expertise. Interdisciplinary teams of experts support the construction of future CO2 pipelines as technical mediators providing third-party consultancy, or assist with quality assurance during construction. Further services include the evaluation of suitable measurement procedures to ensure implementation of an ideal CO2 infrastructure. The operators of future CO2 storage sites benefit from technologically feasible and cost-efficient monitoring strategies, the intelligent combination of geophysical monitoring methods and support during the approval procedure for the overall system.

In addition to its services in CCS technology, TÜV SÜD also presents an integrated service package for the owners/operators of solar thermal power stations, wind farms and 700-degree power stations at the Power-Gen 2010.