12 Nov 03 12:33
1969grad and jsummerfield
Thank you for your replies
As a follow-up I consulted a midwest based natural gas pipeline company. A helpful gentleman provided this example of natural gas transmission.
Length of pipe: 100 miles
Inside diameter: 29 inches
Pressure: 1000 psi starting, once dropping to 750 psi a compressor station is needed, therefore compressor station at 50 mile mark.
Compressor station size: 11,000 horsepower
Pipeline Throughput: 747 mmscf/day
Using this info and the following relations and assumptions:
1 horsepower = 0.746 kilowatt
then 11,000 horsepower motor = 8,206 kW
Heat Rate of natural gas fired Combustion Turbine to run compressor station (typical):11,000 Btu/kWH
Natural Gas heat content: 1.029 MBtu/mscf
8,206 kW * (1/1.029 mscf/MBtu)* (11,000 Btu/kWH) * (24 hr/day) =
Therefore the losses in transmission from compressor are:
2.105/747 = 0.3% per 100 miles
If one assumes it really requires 2 compressor stations per 100 mile it would be 0.6 % I would request anyone in the gas business to verify, please.
Also the 747 mmscf/day is enough natural gas (rate of flow) to continously operate, approx., a 2,900 MW power plant. This is a lot of power, enough to meet the electrical energy reqirements of a city, say, with population of 0.5 - 0.75 million.
Also this shows me I must increase my transmission voltage if I want to match the efficiency of transporting energy via natural gas. An expensive proposition.