Creating Optimal LNG Storage Solutions
Liquefied natural gas (LNG) has taken a firm foothold as the marine fuel of the future, a fact that is clear to many stakeholders in the shipping industry. Despite this positive sentiment, the high investment cost for LNG storage systems is commonly cited as one of the major challenges in switching to gas. Wärtsilä continues to develop ways to combine technologies to create cost-efficient storage systems for gas-fuelled vessels of any size and installed volume of LNG.
Shipping is a truly global market, where competition is continuously increasing. The pressure from customers to reduce costs is further amplified by public demand to reduce the sector’s environmental footprint. Implementing innovative new solutions or adopting already existing technologies from other areas can be used as means to reduce costs and stay ahead of the competition. The latter option is typically more straightforward, with lower risks and a shorter time to market. Therefore, comparing the available technologies and their cost drivers can aid in devising methods to overcome implementation barriers. As a matter of course, every Wärtsilä solution takes into account each customer’s unique needs, but this review showcases a few of the ways that Wärtsilä can help more customers take advantage of LNG’s environmentally and economically sustainable benefits.
Established LNG storage systems
Large LNG carriers have been designed with prismatic membrane tanks for several decades. Today, this design is the most popular LNG containment system for volumes over 100 000 m3. However, the high degree of sophistication required during onsite manufacturing, combined with the complex cargo handling system, has limited the success of the design as an LNG fuel tank.
At the other end of the scale, the most successful concept for gas-fuelled vessels has been vacuum insulated tanks. Vacuum insulation is the best insulation technology available, and is likely to remain so. A vacuum is maintained in the annular space between the two inner and outer tanks in order to reduce the convective heat transfer. In addition, the annular space is filled with an absorptive material to reduce the heat transfer due to radiation. With very low boil-off rates, the tank pressure can be easily maintained below the opening pressure of the safety valves for very small storage volumes. Therefore, vacuum insulated tanks will continue to be the preferred alternative for small LNG storage tanks below 240 m3.
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