Natural gas powered motorhomes

Lee Litchfield · 01-20-2010, 12:43 PM

I've posted some info on alternative fuels and going green on my blog that some of you might find interesting. Here's a link: Lee Litchfield Blog

Lee

Batman_777 · 01-20-2010, 01:58 PM

I would like a Nuke powered MH please

GaryKD · 01-20-2010, 02:43 PM

How about a coach that runs on air! There is a car, in Europe, that runs on compressed air.

RustyJC · 01-20-2010, 02:59 PM

Quote:

Originally Posted by GaryKD

How about a coach that runs on air! There is a car, in Europe, that runs on compressed air.

Compressed air is only an energy storage medium, not a fuel, and air motors have been around for many decades. It took energy somewhere to drive the air compressor to fill the tank - unfortunately, there's no free lunch here.

It's sorta like plug-in electric cars - unless the electricity is "clean" (e.g., solar, wind, nuclear, hydro, etc.), then the electric car just moves the pollution from the freeway to the stacks of the coal, oil or natural gas fueled generating plant.

By the way, CNG (compressed natural gas) has been used as a vehicle fuel for a long time in countries that don't have significant crude oil resources to refine into gasoline - New Zealand is one example. It's actually an excellent fuel - very clean burning with a high octane equivalence. The problems are (1.) there's really a minimal supporting infrastructure (which exit do you take off the Interstate to fuel up your CNG-fueled rig?) and (2.) storage tanks for the pressures required are heavy and bulky. Energy density isn't that great, either. At 1000 BTU/standard cubic foot, it would take (depending on whose BTU content numbers you use for #2 diesel) 130 to 147 standard cubic feet of natural gas to provide the same BTU content as 1 gallon of #2 diesel fuel - the range implications are pretty obvious.

Rusty

idenphones · 01-20-2010, 04:01 PM

A long lost buddy of mine from many years ago had a motor home that was dual fueled with propane and gasoline.

If I remember right he had enough propane on board as a motor fuel to equal about 3/4 of a tank of gasoline plus the gasoline, plus propane for heat etc.

I remember that he drove it several times from Toronto to Vancouver and back for his business and I am quite sure it was a class A.

I do remember that it had a "Hat" affair over the carb. to "inject" the propane, and it was a GM chassis.

Other than that, the memory cells are straining right now!

edgray · 01-20-2010, 04:34 PM

Quote:

Originally Posted by RustyJC

By the way, CNG (compressed natural gas) has been used as a vehicle fuel for a long time in countries that don't have significant crude oil resources to refine into gasoline - New Zealand is one example. It's actually an excellent fuel - very clean burning with a high octane equivalence. The problems are (1.) there's really a minimal supporting infrastructure (which exit do you take off the Interstate to fuel up your CNG-fueled rig?) and (2.) storage tanks for the pressures required are heavy and bulky. Energy density isn't that great, either. At 1000 BTU/standard cubic foot, it would take (depending on whose BTU content numbers you use for #2 diesel) 130 to 147 standard cubic feet of natural gas to provide the same BTU content as 1 gallon of #2 diesel fuel - the range implications are pretty obvious. Rusty

Rusty: thanks for shedding some additional light on the subject. However, your last comment only applies to people smarter than me.

Will you please elaborate about the "obvious" because I don't know how to relate the BTU values a SCF of NG vs. a gallon of CNG or how to compare those values to a gallon of diesel (or gasoline). How big a tank does the compressed NG require to equal the motive power in a 100 gallon diesel tank? Thanks, ED

Lee Litchfield · 01-20-2010, 05:09 PM

I do remember the propane powered motorhomes. We sold a few after the energy crisis in 1979. Propane was dirt cheap at that time. Back then, the problem was not only cost, but availability of gasoline. When that was solved, the propane vehicles sort of went away. We did convert our shop truck to propane and drove it for several years without any problems. Lee

69RoadRunner · 01-20-2010, 06:05 PM

The government has this car that runs on water, man!

(Sorry, That 70s Show reference)

RustyJC · 01-20-2010, 06:15 PM

Quote:

Originally Posted by edgray

Will you please elaborate about the "obvious" because I don't know how to relate the BTU values a SCF of NG vs. a gallon of CNG or how to compare those values to a gallon of diesel (or gasoline). How big a tank does the compressed NG require to equal the motive power in a 100 gallon diesel tank? Thanks, ED

First, CNG is stored as a gas. LNG (liquified natural gas) is the liquid form and requires lots of refrigeration.

Just to make the math easy, let's pick a number within the range I quoted earlier and say that 1 gallon of #2 diesel contains 140,000 BTU. Assuming 1000 BTU/scf (standard cubic foot) natural gas, then 140 scf of natural gas would be required to equate to 1 gallon of #2 diesel. Since 1 gallon = 0.1336806 cubic feet, then the volume of natural gas at atmospheric pressure would be 140 / 0.1336806 = 1047.3 times the volume of #2 diesel.

Rather than get into the intricacies of the ideal gas law, let's say that a 1:1 relationship exists between pressure and volume (that's fairly close, actually.) This means that we would have to compress the 140 scf of natural gas 1047.3 times to fit it into the volume occupied by a gallon of diesel. To use the same size tank, we would have to store the compressed natural gas at 1047.3 x 14.7 psia = 15395.31 psia, which isn't very realistic. If we stored the natural gas at 2500 psig, it would occupy 15395.31 psia / 2514.7 psia = 6.122 times the volume occupied by the #2 diesel.

Said another way, if we had to use the same size tank for CNG as we do for diesel and stored the CNG at 2500 psig, then our range would be only 1 / 6.122 = 16.334% that of the same motorhome on #2 diesel. Thus, my comment about limited range.

Rusty