Environment and Energy

Traveling by CNG in Thailand

12 Comments

Spouse and i had planned a trip to SE Asia for late October through November of last year.  We would fly into Bangkok, spend a few days with friends then a few more in Sukhothai, on to Chiang Mai, then 2 days by boat from Chiang Kong to Luang Prabang, flight to Siem Riep, car to central Thailand, return to Bangkok for a few more days and home.  That was the plan and since we would get there at the height of the recent flooding, Lucia suggested a post. 

We had planned to spend the first 4 days of trip in Bangkok but there was continuing uncertainty about flooding along Sukhumvit Road where our friends lived so we diverted to Sukothai and returned to Bangkok at end of trip. More on boating on Mekong and flood effects in subsequent posts.

I thought it might be interesting to share a couple of things that surprised us while we were over there, to wit, widespread use of compressed natural gas (CNG) for motor-fuel.  

We took a 12 passenger Toyota public van from Wang Nam Khiao to Bangkok, a distance of 250k. It was inexpensive although we had to buy an additional seat for our two carry-ons.

We stopped for refueling 15k outside of Bangkok. Driver asked us all to disembark, said it was Thai regulation during fueling. The hood was lifted and a fueling hose connected.

Fuel was compressed natural gas. The station sold CNG at 6 pumps and business was brisk. There were other vans like ours, taxicabs, and pick-up trucks. I talked to one of the pick-up drivers who said that CNG was so cheap, he had converted his Toyota pick-up to burn it. The gauge on the dispenser read 200 bar/3,000 psi.  

Our van also burned 91 Gasoline and had automatic fall-over to gasoline if it ran through its supply of CNG. Driver said this didn’t happen very often because there were enough CNG stations on the routes he drove.

It appears that all motor-fuel is subsidized in Thailand but especially CNG. In addition to CNG, LPG (Propane), diesel (Number2), two grades of straight gasoline plus 4 more of various proportions of gasoline-ethanol, and even straight ethanol are available – but not all at every station.

CNG is sold by the kilogram at 8.5 Baht/kg. Gasoline is sold by liter and was in low Baht 30s/L when we were there. Diesel was 28 Baht/L. Figuring Baht at $0.032 shows that CNG was $0.272/kg, and gasoline over $1.0/liter.

Using CNG to Gasoline Equivalent of 2.267kgCNG=1 Gallon of gasoline, price of CNG is equivalent to paying $0.61/gallon for gasoline. At $1.00/L, Thai gasoline costs $3.80/Gal – quite a difference. Read here for Gasoline gallon equivalent

CNG is produced by a government owned refinery and there are plans to raise the retail price by 70% over the coming year to 14 Baht/kg. Producer says that cost of production is 16 Baht/kg. CNG in Thailand could be sold profitably for a bit over $1.15 per gasoline gallon equivalent.

Read Here for a more detailed discussion of fuel types in Thailand.


12 thoughts on “Traveling by CNG in Thailand”

  1. In Holland about 20 years ago there were quite a few natural gas cars. Many gas stations had tanks. They would have been far cheaper to run except that there was an extra tax on the fuel. The problem is underground car parks, from which they were banned. Performance and refueling were not much different.

  4. Natural gas is mostly methane, IIRC. So the CNG tank on board the Toyota will contain compressed methane, at high pressure in its gaseous form. By Boyle’s Law (or PV=nRT from Chem 101), double the tank’s pressure and double its capacity. A concern, then, with CNG and with gaseous hydrogen as fuel is that storing fuel in a reasonably compact volume requires a very high pressure tank.

    So it’s of note that Thailand has solved the safety issues related to this (at least to their satisfaction).

    By contrast, I have a beat-up old Weber barbeque that uses 20-pound propane tanks. I refill them at my local garden store with liquid propane. As I grill chicken, the propane liquid in the tank boils, and the gas at the top of the tank is fed to the burner. This means that the high-density storage of fuel is achieved by having a tank with a somewhat high pressure, but PV=nRT doesn’t rule — the fuel is liquid. From an online chart, the internal pressure of the 20-pound tank is 24 psi at 0F, 92 psi at 60 F, and 172 psi at 100F. Much lower than the 3,000 psi that J. Ferguson read off the gauge at the filling station!

  5. Aren’t there also problems with retaining the gas in the tank? I seem to recall that early adopters of LPG used to report that the tank would empty over time, even if the vehicle was not being used?

  6. Re: diogenes (Comment #88326)

    That would be true of LNG (liquified natural gas). It is a liquid because of it’s low temperature. As heat is absorbed from the environment (no tank is a perfect insulator) there will necessarily be some loss. As far as I know, LPG can be stored under pressure essentially forever.

  8. D Johnson…just wanted empirical evidence…I think the seals round a car’s gas tank are probably not good enough to store LPG, let alone CNG. So unless you do a regular mileage, it is a poor trade-off…jus
    t wanted to hear some fact(oids)

  9. Re: AMac (Jan 6 08:18),

    If you live far enough away from the equator, it can get cold enough that the vapor pressure of liquid propane drops so low it can’t volatilize at a sufficient rate to provide fuel without an external energy source.

    The problem with methane is that its critical temperature is -82.7C, which means it cannot exist as a liquid above that temperature. Above that temperature and corresponding pressure it probably exhibits fluid like properties, i.e. a supercritical fluid. Supercritical CO2 has interesting solvent properties and can be used as the mobile phase in ‘liquid’ chromatography.

  10. I live in northern California and drive a cng vehicle. price out here is about $2.50 per gge. In Utah cng is quite cheap.

  11. diogenes (Comment #88351)
    Automobile gasoline tanks aren’t up to carrying either LPG or CNG, due to the pressures involved. Converting a vehicle for either fuel involves, among other things, new tanks designed for appropriate pressure: approx 135 psi working for LPG and 3,000 PSI for CNG.

    buck smith (Comment #88680)
    I wrote this post mostly because I was astonished to find CNG motor fuel in everyday use in Thailand, never having seen it here except in city buses.

    Is the $2.50 per GGE subsidized or absent tax otherwise applied?

    (updated 1/17/12 Better grammar by successive approximation)

  12. I have had several trucks converted to Propane. It involves installing a pressure tank, a vapourizer which has engine coolant flowing through it to heat the propane, a mixer on top of the carburetor or fuel injector plenum air inlet, and the proper pressure lines. Expect about a 10% loss of power compared to gasoline, but the engine oil looks as clean coming out as when it went in.

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