FSRUs and LNG ships have 4 to 6 separate cargotanks inside their hull. As LNG is stored at very cold temperatures, the cargo tanks are segregated from the steel hull structure by thick insulation.
There are 2 cargo tank designs commonly in use. Membrane tanks are box shaped and LNG ships with membrane tanks look like any other liquid bulk tanker. The other design is known as ‘Moss tanks’ that are spherical.
LNG ships equipped with Moss tanks have the recognizable dome shaped tanks visible abFSRUs and LNG tankers are powered by the LNG they carry, making them one of the most environmentally friendly ships in the world, emitting less CO2, NOx, SOx and particulate matters than most other ship types that burn heavy petroleum fuels.
As such, an LNG ship will only be carrying relatively small quantities of non-LNG fuels to power non-propulsion systems. Unlike oil tankers, FSRUs are not involved in oil cargo transfer operations where there is the possibility of a spill or pollution.
LNG cargo is a clear, colourless and odourless liquid; if a small quantity is accidentally spilled it will quickly and completely evaporate leaving no footprint behind.
Advantages of FSRU
- The onshore facilities can take between 5 and 7 years to be planned, constructed and brought online, while the FSRUs are not only easier in implementing, but cheaper.
- A newly built FSRU costs close to $260 million. Some companies have even started converting old LNG carriers into FSRUs, for which the cost is more like $160 million, and can be ready in just 14 to 16 months.
- FSRUs, compared to their onshore counterparts require little construction or investment, and can therefore provide access to LNG much faster.
- FSRUs have one major drawback, its capacity limitations. Most have a peak capacity of around 4 million tons annually (about 500 million cubic feet per day), though some of the new ones are getting closer to 1 bcf/d.
- Offshore units have less scope of expansion, because of their capacity constraint. A FSRU has a maximum regasification capacity of 600-800 million standard cubic feet per day and can store between 140,000 m³ and 180,000 m³ of gas.
- Another issue with the FSRU is the lifespan. Usually the leasing arrangements of FSRUs are for 10 to 12 years.