?? Why go thru the problem of cryogenic when propane liquefies without cryogenic?

Where would you tank up with one of these monsters? LNG terminals exist only at major ports, and they boil up their LNG into gaseous form before before distributing it through the traditional pipeline infrastructure. In fact, proposals for new LNG import facilities in the US sometimes involve putting the LNG sphere a few miles offshore and piping in only pre-vaporized gas, as a safety precaution. LNG is sometimes distributed by truck in insulated containers to regional NG facilities, but there are hardly LNG stations at every corner, and I cannot imagine the expense involved in building them. Re-liquifying NG at remote locations sounds energy intensive and kind of pointless.

Another problem is boil-off. If you fill up your car and then leave it in your garage for a week, heat will infiltrate even a well-insulated tank and encourage the NG to boil into gas. That will increase pressue on the tank walls to a dangerous extent. The tank will have to vent the gas somehow, which means either venting raw NG into the air, which is a safety hazard of untold proportions, or burning it off in a controlled flare, which is safe(r) but wasteful.

The only context in which vehicle-sized LNG tanks make sense are public transit operators. They use a lot of fuel, have a small number of fueling depots, drive predictably and daily, and have trained staff on hand to offload unused fuel in case of emergency.

This past May, a tanker truck carrying LNG overturned on the Massachusetts Turnpike a few miles west of Boston. The danger posed by a potential leak was considered so great that they had to close the entire highway *in both directions* ten miles on either side of the wreck for a ten hour period. The 'both directions' element was the unusual part, in that previous tanker accidents I've encountered usually only close the side of the road where the tanker was driving. At any rate, the traffic tie-up created by that mess was simply stunning. I was on a bus, riding from Hartford to Boston, and what is ordinarily a two hour trip turned into a seven hour one. So that's how I feel about taking LNG onto the road.

Max:
LPG, as name implies, is by-product of oil refining, comprising mostly of propane, to less degree of butane, with some ethane and higher then butane hydrocarbons. Simply put, it is gaseous fraction which could be liquefied at elevated pressure at normal temperature. However, most of LPG currently is derived from NG exploration. NG contain couple of percent (widely varies from one field to another), which should be separated at well-head before entering high-pressure gas pipeline, other vice it will liquefies on route and plug the pipeline. Also some LPG gas is recovered from oil wells as part of oil co-gases.

LPG represents premium heating fuel, as it is easy to transport, easy to handle in boilers and stoves, and its combustion is very clean even on most primitive equipment. There is hardly surplus of LPG to be used as transportation fuel on large scale. However, in some locations, where it is plentiful, it is premium, relatively cheap, clean burning high octane fuel and is used quite extensively (once again, in some locations).

Liquefaction of NG is extremely energy consuming and wasteful. Currently LNG transportation from remote gas fields is booming industry. The reason is that pipeline NG distribution system could not keep up with ever increasing demand for NG, and LNG is currently only economically viable option to bring NG from remote gas fields to the consumer. On the arrival to coastal port, most of LNG is re-evaporated by heat exchange with sea water, and pumped into existed CNG pipeline system. Currently huge LNG project is in final approval stage to bring LNG from Russian Barents sea off-shore platforms to US East Coast customers. Many other projects around the world are under way.

Personally I consider LNG transportation as waste of valuable resource and strongly favor gas-to-liquid technology, such as huge Sasol plant in Bahrain.

NBK:
You are absolutely right. LNG tank have substantial boil-off, and the smaller the tank the higher boil-off is necessary to keep remaining NG in liquid state. Huge LNG tankers use boil-off of their cargo as supplementary fuel to their dual fuel diesel engines, or even repowering ships with steam turbines, or to drive refrigerators to return at least some portion of boil-off gases back into cryogenic tank.
For private transportation LNG is absolutely unacceptable due to mentioned safety hazard and waste of LNG while vehicle is not in operation.

The only niche I see for LNG fueled vehicles is for port serving equipment (and it is huge market), limited to the ports already receiving LNG bulk.

There is no reason you could not use it for cars. With an onboard cryo and hybrid battery capacity, you could keep it cool for quite some time.

The really great opportunity for LNG arises as a result of the exponential growth in LNG world trade. Qatar has about 100 years worth of gas..it has no pipeline option, so it liquefies it, making LNG. That LNG is transported to US or Europe with minimal losses in terms of energy. The LNG is then transferred to storage facilities onshore. Normally the LNG is heated and converted back into natural gas for distribution. However, if it goes straight into vehicles as LNG fuel (converted back to gaseous to natural gas just as it enters the engione of course) then the 'Well to Wheel' efficiency is fantastic, cannot be beaten by any other fossil fuel. Further, if you compare this to 'gas to liquids' it becomes clearly the winner - about 30 - 40% net energy required, which is 30 - 40% less CO2 produced.

The UK has a national network of LNG filling stations already - see
www.chive-ltd.co.uk/chivefuels/naturalgasrefuelling.htm

Two UK companies (Clean Air Power Ltd and Hardstaff Group) are now taking 400 hp trucks (Daf, Mercedes and Volvo) and converting them into diesel - natural gas dual fuel (CNG or LNG). This gives around 25% less CO2 than 100% diesel and less NOX and particulates....great idea that is catching on as oil gets more expensive.

Final point - a UK company makes LNG from landfill waste gas. To clean up the landfill gas you end up with an LNG product - run your buses and refuse lorries on this and it has a NEGATIVE impact on greenhouse gas emissions as the landfil gas has a use and is not vented or flared. As energy becomes more expensive, LNG will come into its own.

I tend to agree with John Baldwin. Just because USA currently has only one option - gasoline - that does not necessarily apply to the rest of the world. Chine more or less has to build a new infrastructure from scratch and is thus not limited by what is already in place. And let us not forget that this post did in fact concern the Chinese market.

For the rest of the world, LNG for busses, trucks and trains that do not use tens of thousands of refueling stations would ease the pressure on oil derived fuels for transport.

In US North West and in Canada West there is wide LPG and CNG refueling infrastructure in place. Yet, very few private motorists use LPG and CNG. Considering substantial fuel and maintenance saving costs, I find it quite strange. Probably cars manufacturers to blame for not supplying CNG and LNG fueled vehicles at reasonable cost. Most private vehicles using propane and NG are driving after marked conversions, which are expensive. Really odd situation.

The energy needed to maintain the low temperature in LNG tank, where does it come from. Does it take from the NG fuel itself. And how much NG energy does it consume in 1 month. Any idea.

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