CNG STATION DESIGN – HOW TO DESIGN A CNG STATION FOR VEHICLE REFUELING
The following is a CNG Station Design overview for those that are in the beginning stages of considering installing a CNG Station for Fleet Refueling.
There are some key pieces of information needed to properly size an NGV refueling station. As with any project, the more information you have; the more accurate an estimate can be given.
Following is a list of questions that will help us size a NGV refueling station to meet your needs:
PLANNING YOUR NGV REFUELING STATION
1. Determine what type of vehicles will be refueled. Light duty vehicles? Forklifts? School Buses? Municipal Vehicles?
The type of vehicles you plan to fill will help us determine the best station design for your specific fleet. For example, if you have a school bus fleet you will probably refuel these in a different manner than say a taxi fleet based upon the vehicle operating times.
2. How many vehicles will be refueling at this site?
This is a critical piece of information since this will help determine the station loading or how much natural gas must be delivered.
3. Determine the amount of gasoline each vehicle requires.
Again, another crucial piece of information needed. We use a conversion factor of 125 scf per equivalent gallon of gasoline. So, if you have a pick-up truck that takes 10 gallons of gasoline every day we know that it will require 1,250 scf of natural gas every time it fills up. Try to get as accurate a number as you can since this will again determine station load.
4. What time frame will the vehicles refuel in?
Sizing an NGV refueling station is like sizing a water heater for your home. If you have a lot of children taking showers before they leave for school in the morning you will need a large storage tank.
NGV refueling stations are sized based upon how many vehicles will fuel, how much fuel they will take and in what time frame. Will all the vehicles arrive early in the morning to fuel? Will 2 or 3 vehicles fuel every 3 hours or will they all fill over night?
5. Determine if the vehicles need to be fast filled or if they can be time filled.
This further defines the amount of time available to fuel the fleet. For example school bus fleets typically are refueled over an 8 hour period during the evening. If they were to be fast filled in the morning before they go out on their routes, the NGV refueling station would have a much different design.
6. Will the amount of CNG transferred into each vehicle be accounted for?
In some instances, fleet managers need to know how much fuel is used in each individual vehicle. In other case, like school bus fleets, they only need to know the total amount of fuel used by the entire fleet. If each vehicle must be accounted for a dispenser will be needed along with a card lock system to assign the amount of fuel transferred to a particular vehicle. This is an important point since it will impact the overall cost of a station.
7. Will the station be used for a private fleet or for public refueling?
This ties into accounting for individual vehicle accountability. Certainly in a public refueling station you will need to know how much fuel is transferred in order to bill the customer.
8. Will the station demand grow in the future and, if so, by how much?
We have found many customers that wish to start with a portion of their fleet and then, as they prove the benefits of natural gas, add more NGVs. If this is the case, it helps to know from the beginning of the project. The number and size of conduit can be sized accordingly along with the addition of compression modules and/or storage.
9. What utilities are available at the location that you wish to install your station?
We will need to know what the available gas pressure is at the site and what the gas quality. This can be secured from your local gas utility. Of particular interest is the moisture content of the gas. All natural gas contains a certain amount of water. Pipeline quality gas is measured at 7#/MMSCF, this means 7 pounds of water in 1,000,000 cubic feet of natural gas. This works fine for the burner tip but might be a problem for NGV refueling, so we will need to know this amount in order to properly size an inlet dryer.
We will also need to know what electrical service is available at the site. Ingersoll Rand CNG packages use 460V/3Phase power. If 208Volt is available, we will need to know this to provide the correct motor.
10. At what pressure will your vehicles operate?
Typically, NGVs store gas onboard at 3,600 psi. Older vehicles had operated at 3,000 psi but we find this to be a rare occurrence. Confirm what fill pressure is required.
Once you have gathered all of the above information contact P. C. McKenzie Company to discuss your particular application. We can size your station based upon your unique requirements and offer suggestions to improve performance or reduce station costs.
CNG PRE-CONSTRUCTION CONSIDERATIONS
- Secure and review the current NFPA-52 guidelines for Compressed Natural Gas Vehicular Fuel Systems Code. This code is published by the National Fire Prevention Association and applies to all the design and installation requirements of CNG refueling facilities.
- Contact your local Fire Marshall and Building Inspector who can help guide you through local code requirements and the permitting process.
- Contact your natural gas provider to determine the following –
a) Gas pressure available at your location.
b) Gas quality including moisture content
c) That the existing gas service can support the gas flow required by the station.
- Contact your electric company to determine the following –
a) Electrical service available at the site.
b) Can the existing service support the electrical demand for the station
- Contact a local contractor that is qualified to install an NGV Refueling Station.
P.C. McKenzie Company has many contacts throughout the USA to help with providing station installation.