The US has seen a startling reversal of its energy fortunes over the last five years. The shale gas boom, good electrical infrastructure, and ongoing concerns about CO2 emissions have driven the development of eLNG.
eLNG is the liquefied natural gas (LNG) supply chain enabled through full electric motor driven compression technology in the processing, transport and distribution network for LNG as an alternative to the traditional turbine driven devices. It is a fast emerging and efficient means of extending the reach of natural gas resources and one that GE is seeing huge interest in.
The US turnaround has been so spectacular that, from expecting to become a major natural gas importer, the country is now on the verge of becoming one of the largest LNG exporters. At the moment, the US LNG industry only delivers its product locally, and if consumption levels stay the same, the US will have sufficient gas resources for nearly 100 years. However, US lawmakers are discussing changes to its energy policy that would allow natural gas exports to countries within the World Trade Organisation. This has led to a number of plans to transform facilities originally built for LNG imports into liquefaction export facilities instead. While the first wave of US LNG exports is still a few years away, it could amount to as much as 9 billion ft3/d by 2020, contributing to a rise of between 8 – 25% of global LNG trade by 2035.
LNG plants are hugely complex and costly facilities that require major financial backing. However, introducing electrification to power LNG offers three core advantages:
Electrical variable speed drive systems (VSDS) are more economical to run in comparison to gas turbines as they offer high efficiency at a constant level, across the entire operating speed range. Gas turbines, on the other hand, can operate at their maximum efficiency at a high fixed speed, reaching an average efficiency level of around 40%. Compared to that - and depending on the installation - a typical electrical driving system can be significantly higher. Used through the compression, liquefaction and transport processes, these are a core ingredient of the eLNG promise.
Electrical system architectures enhance reliability, especially in terms of system management and maintenance. This is because multiple redundancy levels can be arranged at Variable Frequency Drive (VFD) elements to ensure full operation even in the event of a single failure, in addition to very fast repair time as a result of the modular structure of the system. This results in electrical system uptime of up to 99.9%. Typical architectures are able to run for up to 5 years without the need to stop for maintenance.
Electrifying the systems architecture also significantly improves the interaction between LNG plants and national electrical grids as it solves some of the most critical problems related to grid stability. These include issues such as the evaluation and mitigation of harmonics pollution, subsynchronous torsional interaction risk, electro-mechanical system integration and full torsional lateral analysis for project dedicated shaft line verification.
GE Power Conversion holds many milestones in terms of technology (largest VSI VFD operating) and is actively involved in a number of major eLNG projects across the US, providing the industry with an integrated eLNG system that includes leading electric high power motors, VSDS systems and compressors. While the shale gas boom has already had an immense effect on the US energy market, it is about to have broader global implications, with eLNG providing a catalyst for change.
Written by Francesco Falco, GE’s Power Conversion business. Edited by Callum O'Reilly
Read the article online at: https://www.lngindustry.com/special-reports/25042014/elng_in_the_usa_460/