“Waste-to-Wheels: Building for Success”

Columbus Ohio--Dec. 1, 2010

CNG Station Design Primer

Presented by:Marathon Technical Services

Presented by:

Rob Adams, P.Eng., CMA, MBAMarathon Technical Services

MARATHON TECHNICAL SERVICESMARATHON TECHNICAL SERVICES

Slide 2

It is critical to accurately project fill time and quantityof fuel required initially and as the fleet grows:

• Collect number, type and fuel consumption by vehicle—cardlock data will be useful.

• Review data to determine the highest demand fuel window—this will govern sizing.

• (Usually) Use average fuel consumption per vehicle not maximum since maximum will oversize the station

• Gasoline gallons x 120 = standard cubic feet (SCF).• Diesel gallons x 137 = SCF. (possibly add 10% for

diesel efficiency)

Design Parameters-FleetDesign Parameters-Fleet

Slide 3

Type of station required will influence the size and cost of equipment:

• Time Fill—fill entire fleet directly from the compressor over a period of hours.

• Cascade Fast Fill—fill each vehicle in 5 to 20 minutes primarily from stored gas.

• Buffer Fast Fill—fill each (large) vehicle in 5 to 20 minutes primarily from the compressor(s)

Design Parameters-Station TypeDesign Parameters-Station Type

Slide 4

Time Fill—useful for fleets that return to base.• Fill entire fleet directly from the compressor over a

period of hours. • Simple, reliable technology and very good fills.

Design Parameters-Time FillDesign Parameters-Time Fill

Slide 5

Cascade—used where the fleet needs fueling in short (1 to 2 hour) peak periods.

• Fill each vehicle in 5 to 20 minutes primarily from stored gas.

Design Parameters-CascadeDesign Parameters-Cascade

Slide 6

Buffer—used where many large vehicles must be fast filled back to back for several hours.

• Fill each (large) vehicle in 5 to 20 minutes primarily from the compressor(s)

• Most common transit station design• Typically requires very large equipment

Design Parameters-BufferDesign Parameters-Buffer

Slide 7

Meet with the Gas Utility to determine available gas:

• Minimum, maximum and typical pressure in service line with new station load imposed.

• (Medium to large scale) CNG stations can be designed to accept (higher) floating gas service pressure rather than (lower) regulated gas pressure.

• Floating service pressure can significantly reduce size, complexity, initial and operating cost of the station.

• It may be necessary to discuss this need with the Utility as they may have policies to supply only (low) regulated pressures.

• Gas composition and moisture content is required.

Design Parameters-Gas SupplyDesign Parameters-Gas Supply

Slide 8

Remove moisture from the gas:

• Inlet drying recommended

• Regeneration equipment recommended.

• Virtually all stations will require a dryer to be code compliant.

Station Equipment-DryerStation Equipment-Dryer

Slide 9

Raise gas pressure from utility service pressure to 4500 psig:

• Reciprocating compressor—usually electric motor powered.

• Redundancy through multiple compressors or portable standby compressor required if vehicles are dedicated CNG.

Station Equipment-CompressorStation Equipment-Compressor

Slide 10

Required for Cascade and Buffer Stations:

• ASME design Code.• 5500 psig design—4500

psig operating pressure.• Tubes or spheres.

Station Equipment-StorageStation Equipment-Storage

Slide 11

Dispense gas to the vehicles:

• Time fill or fast fill• Measurement (usually

only with fast fill-exception shown)

• Cardlock interface (fast fill)

Station Equipment-DispenserStation Equipment-Dispenser

Slide 12

Most garages will require some upgrade:

• No open flame or heaters >750F.

• Continuous exhaust and makeup air and ventilation to prevent pocketing.

• Electrical upgrades may be required—not necessarily a hazardous location.

• Gas detection system with interlocks to alarms, exhaust fans, doors…

Building ModificationsBuilding Modifications

Slide 13

Meet early and often with Authorities Having Jurisdiction

Partial List of Codes:• NFPA 52-Vehicular Gaseous Fuel Systems Code• NFPA 70-National Electrical Code• ASME B31.3-Process Piping• ASME Section VIII, Division 1-Unfired Pressure Vessels• NFPA 30A-Code for Motor Fuel Dispensing Facilities….• International Building Code• International Fire Code• International Mechanical Code• State and Local Codes

Good Engineering / Industry Best Practices

Permitting, Codes and ApprovalsPermitting, Codes and Approvals

Slide 14

Several common contracting approaches:

• Conventional Split Contract—Purchase equipment and construction under separate contracts.

• Design Build—Purchase of Design, Equipment, Permitting and Installation under a single contract.

• Throughput Contract—Design Build with payment on a per Therm charge (Lease to own)

• Maintenance can be combined or bid separately from the station construction.

• Have parts inventory before the station is commissioned —warranty is not (usually) a maintenance contract.

Contracting ApproachesContracting Approaches

Slide 15

Thank You!

Questions??

MARATHON TECHNICAL SERVICESMARATHON TECHNICAL SERVICES

Slide 16

Marathon Technical Services (519) 699-9250

radams@marathontech.ca

WWW.MARATHONTECH.CA

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