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. However the data collected presented in Burnham and al. 2011 is given per 600miles. The losses considered over the whole distance of the same kind of pipeline is CH4 leakage is a function of pipeline transmission distance. 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.

In GREET now we can define losses per an amount of distance : ${\frac {(0.387+0.278)}{600}}={\frac {0.665}{600}}\left[{\frac {\%}{miles}}\right]$

As we are working in SI units in GREET, we need to convert that in %/meter which gives us : ${\frac {0.665}{600}}\left[{\frac {\%}{miles}}\right]=>6.88686404\cdot 10^{-7}\left[{\frac {\%}{meter}}\right]$ represented as 6.88686404E-09 in ratio/meter in the GREET database

What is ambiguous is this report and GREET1_2011 is what this percentage really is. We can assume that NG after processing contains approximately 92% of CH4, so are we loosing 0.665%/600miles of Natural Gas or CH4 in the natural gas. If we assume that we are loosing 0.665%/600miles of Natural Gas it Resutlts in an emission of 114.459 Grams of CH4 and a loss of 5541Btus of Natual Gas for each 1mmBtu transported thought the pipeline. However if we assume that the emission of CH4 is right in GREET1_2011 we have to update our percentage lost to 0.72058%/600miles. This will result in a loss of 124.025 Grams of CH4 and 6013 Btus of Natural Gas.

In the current version of GREET we will assume that the percentage 0.665%/600miles is right and therefore get 114.459 Grams of CH4 and 5541Btus of Natural Gas lost per mmBtu transported.

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.