Innovative pit type LNG storage system for distributed application in
Singapore urbanized areas
Fei Xiao*
*SJ-NTU Corporate Lab, 61 Nanyang Drive, ABN B3a-04, Singapore 637335
To ensure its accessibility and availability, LNG must go through a very complex network from the
production region to the end users, involving various transportation facilities and services like
liquification/regasification plant, gas grid/truck, bunker/feeder vessel, and onshore or offshore tanks
/containers etc. Normally, after LNG regasification at the receiving terminals, natural gas would be
distributed via pipeline to customers, either industrial or residential. However, it is difficult to satisfy
substantial demand of potential users in areas with under-developed gas infrastructure, either in
remote and poor remote districts and counties (where too much infrastructure investment would be
of low profitability) or in even highly developed regions/cities, like Singapore (where island-wide
infrastructure construction would be troublesome and time consuming). Therefore, the concept of
satellite LNG terminals, with well insulated tank container placed in concrete basement, is proposed
to replace or complement the centralized production-supply networks, which aims at avoiding largescale construction, improving the security of fuel supply, and reducing energy dissipation.
According to economic and stability analysis, each basement will have two tank containers with equal
volume of 23m3, one of which acts as a backup in case of malfunction. To ensure both the workability
and economic viability of this basement-type satellite terminals, many practical factors should be
considered, including site selection, ground excavation, construction of basement concrete wall,
design of tank container and its layout in the basement, boil off rate (BOR) of LNG inside tanks,
temperature distribution inside the basement, and overall budget, existing laws and regulations in
Singapore (requirement on structure and location), etc. Many of these factors are intercorrelated, as
configuration and layout of tank containers can both affect the ground excavation (volume of soil
excavated) and the thermal and insulation properties of both tank containers (BOR) and basement
(temperature field), all of which are under constraints from both overall project budget and
requirements from local regulations and laws. Several three dimensional (3D) numerical models
regarding the mechanical properties of concrete wall and tank container, insulation capability of tank
container and the corresponding BOR, and the interactions between the existing of basement-type
terminal and the ambient environment (including the surround soil and ambient air), where both
stationary and transient models are built for more comprehensive analysis. It is found that the thermal
properties of insulation materials used by tank container are the most critical factors affecting both
BOR of LNG and the overall impact of basement-type terminal on the ambient environment. After
introducing multi-objective optimization, the cost can be reduced by 25% compared with the base
design, with BOR less than 0.1% day and the lowest temperature at the external wall of tank container
higher than -5℃ within several days when insulation material with 0.007 W/(m·K) is used. The storage
system can be made possible with the basement depth limit of 3m without introducing vacuum pump
for vacuum based insulation and compressor for liquefying boil of gas, thus not only reducing cost but
also improving the reliability of regional distribution grid.
Keywords: Basement storage; Environmental impact; Stationary and transient analysis Structure
optimization