Marathon Technical Services - CNG Station Primer


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A primer to building compressed natural gas (CNG) stations for vehicle refueling. Very good!

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Marathon Technical Services - CNG Station Primer

  1. 1. “Waste-to-Wheels: Building for Success” Columbus Ohio--Dec. 1, 2010 CNG Station Design Primer Presented by: Marathon Technical Services
  2. 2. Presented by: Rob Adams, P.Eng., CMA, MBA Marathon Technical Services MARATHON TECHNICAL SERVICESMARATHON TECHNICAL SERVICES Slide 2
  3. 3. It is critical to accurately project fill time and quantity of 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
  4. 4. 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
  5. 5. 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
  6. 6. 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
  7. 7. 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
  8. 8. 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
  9. 9. 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
  10. 10. 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
  11. 11. 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
  12. 12. 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
  13. 13. 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
  14. 14. 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
  15. 15. 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
  17. 17. Marathon Technical Services (519) 699-9250 WWW.MARATHONTECH.CA Research CNG Station Support Accident Investigation CNG Station Design Building Upgrade Design Training MARATHON TECHNICAL SERVICESMARATHON TECHNICAL SERVICES