18010

NG Transmission and Distribution

This process is representing a single pipeline of 500 statute miles in GREET1_2011. The fuels used by the pipeline to power to compressors are : - Electricity - Natural Gas

The fuel usage is calculated using the regular Pipeline Mode calculations.

Losses

This process assumes some losses, as for most of the transportation processes, the losses does not have an impact on the process fuels usage. So we can imagine that as being lost at once before entering the pipeline instead of being integrated over the length of the pipeline.

The data collected presented in Burnham and al. 2011 is given per 600miles. Here, 0.387%vol CH4 leakage is assumed in NG Transmission and Storage and 0.278%vol leakage in distribution for a distance of 600miles. It is a volume ratio which means that for each unit of volume of Natural Gas throughput, we have 0.00655 unit of volume of CH4 vented for a pipeline of 600 miles. Hovever Natural Gas is not made of CH4 only, the mass ratio of CH4 in Natural Gas of 92.28718 %mass

What we want to know is what is the mass amount of Natural Gas vented per mass unit of Natural Gas throughput :

${\frac {VolumeCH4Leaked}{VolumeNGThough}}=0.00665$

${\frac {MassCH4Leaked}{MassNGThough}}=0.00665\cdot {\frac {\rho (CH4)}{\rho (NG)}}=$

${\frac {MassNGLeaked}{MassNGThough}}={\frac {MassCH4Leaked}{MassNGThough}}\cdot {\frac {\rho (CH4)}{\rho (NG)}}$

In GREET now we can define losses per an amount of distance : ${\frac {0.00665}{600}}\left[{\frac {\%}{miles}}\right]$

As we are working in SI units in GREET, we need to convert that in %/meter which gives us : ${\frac {0.00665}{600}}\left[{\frac {\%}{miles}}\right]=>6.886864047\cdot 10^{-9}\left[{\frac {\%}{meter}}\right]$

Modeling

The real pipeline is using energy for compressing and control over the whole length, and losses are happening over the whole length. The amount of $NG_{In}$ and $NG_{Out}$ are related by the losses : $NG_{In}=NG_{out}+Losses$

The fuel used for compressors energy is given per amount of $NG_{out}$

We are not modeling losses over the length of the pipeline. Therefore the amount of Nature Gas passing though the compressors is assumed to be $G_{out}$, this is how we are modeling the process into GREET :

We assume the losses to happen just before the carried material passes thought the transportation mode, and this is common to all step losses.

References

• U.S. EPA. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009; EPA 430-R-11-005; U.S. EPA: Washington, DC, 2011.