I guess that some of you noticed I have been blogging on Green Energy without ever writing anything about CNG. Well here goes. I like green energy, I have found it difficult to find snapping turtle facts about CNG. It seems that everyone has an angle or something to sell. I just want the facts so that I can make up my own mind. I don't need someone to tell me how to think. This will be short because I do not have many repeatable facts.
I found one study by Edmund's, the car company, that did seem to have some facts. Like most of these, I had to do more research to clarify them. Edmund's converted a standard production car and ran an equivalent of 51.9 gal of CNG thru it. Since, by definition, the CNG was equivalent, they got the same gas mileage. Follow that one? They did the test in San Diego, Ca and got the CNG from a local source. They did get some details about the cost of the CNG. To produce the 51.9 gal equivalent, it required $40.29 of electricity to run the compressor and the natural gas was $91.69. Based on these two numbers, the CNG would cost $2.55. Sounds good so far, but. They did not say how much they actually paid for the CNG.
I looked up what the cost would be for a compressor unit rated at 3,000 psi and I think that I could buy a home unit for about $3,000. If I used 1,000 gal per year and wanted to pay the thing off in 5 years, it would cost me $0.60 per gallon. Now, that brings the cost of CNG up to $3.15/gal. Not looking so good. I still have to work on getting even better numbers.
If you noticed, electricity to run the compressor turned out to be 25% of my total $3.15/gal. If a group went together on the compressor, that could reduce the $0.60 capital cost, but the number would not go to zero. The fact that the electricity cost is so high tells you that it must take a big electric motor to produce a lot of CNG and you would be right. We know that 1 hp is equal to 0.75 kwh. Now if we pay $0.15/kwh and the gallon of CNG required $0.78 of electricity, then to make one gallon of CNG per hour you would need a compressor with a 6.9 hp. Well now, that is a very big unit. Most of the home units that I found on the Internet only had a 2 hp motor and could only make about a quart of CNG per hour.
AS you are starting to see, it is a little more complex than people have been letting on on. I is much the same when you ask how long it takes to recharge a big car battery or how big of an electrical service you need. Because Americans are so dumb when it comes to anything technical, they have to go on "faith" and you all know how far that has gotten the human race. I'll have more when I get some more facts.
