An interesting bundle of factoids arrived in my daily newsletter from the American Petroleum Institute, API. The cost of shipping LNG is disclosed. I’ll just cut and paste it for convenience. The source is Freightwaves.

From API- “Liquefied natural gas charter rates were estimated to average $313,000 per day for the most efficient LNG carriers and $276,700 per day for tri-fuel, diesel engine carriers as of Monday, according to Clarkson’s Securities, some analysts predict rates could climb as high as $500,000 per day or even $1 million in the fourth quarter amid tight ship availability on the spot market. “According to brokers, owners can now achieve three-way economics, which means they are compensated not just for a regular round voyage but also for positioning voyages,” said Clarksons Securities analyst Frode Morkedal.”

Ok, I like big boats and I cannot lie. When you look into the shipping vessels themselves you can find a wondrous horde of information on LNG carrier details, such as tri-fuel, diesel engine (TFDE) powered ships. These are ship propulsion systems that drive the propellers with electric motors that in turn are energized by generators driven by engines that can burn diesel oil or LNG.

There are many advantages to the TDFE propulsion systems. Due to the low boiling point of LNG (-161.5 C), loss of LNG to evaporation is unavoidable. Fortunately, the boil-off vapor from the LNG tanks can be piped down to the engine room and used for propulsion. This LNG boil-off can be used to generate steam or can be used directly by powering two-stroke engines. The newer TFDE system, or the DFDE (Di-Fuel Diesel Electric) engines require less space than conventional diesel engines with all of their ancillary features. This leaves more room for payload.

The Bright Hub Engineering site says that a typical TFDE electric generator system produces 8 to 12 megawatts of power from each of its 4 generators at 6600 to 11000 volts at 60 Hz. The electric propulsion motors are coupled together with a reduction gear to turn the props.

As alluded to above there are duel fuel 2-stroke marine engines in use. The duel fuel engines combine Heavy Fuel Oil (HFO), also called bunker fuel, or Marine Diesel Oil (MDO) with LNG in the Diesel cycle with a load range of 10 to 100 %. The mixture of HDO or MDO with LNG is injected directly as opposed to being premixed with air. Because the autoignition temperature of LNG is high, a small amount of pilot oil is injected as well to ensure ignition. The actual mixture used can be adjusted to best match the price and availability of the fuel oil.

The di- and tri-fuel systems have the advantage of producing considerably less pollution that conventional bunker fuels. This is especially important in port where emission controls can be very strict.