In my article Rebalancing of the US Coal and Natural Gas Industry, I show a chart which shows that the natural has storage low point, and subsequent net gas injection volume before the peak is reached, has an inverse linear correlation relationship, such that of the storage low is lower, more gas will be injected to bring the storage peak up, vise versa, if the storage season begins from a high point, less gas will be injected to maintain the storage peak at roughly the same level.
That correlation does exist, but the first chart in that article does not show the correlation well, because the total storage capacity has expanded over the years, therefore the target storage peak is not a fixed number, but one that gradually goes up over the years. Once this effect is taken into account, the linear correlation looks perfect.
See the revised chart below:
I am publishing the second part of the sequel article, Rebalancing of the US Coal and Natural Gas Industry. Please check back and read it on Monday or Tuesday. It explains the correlation in details. Enjoy!
Another question to ask: Is natural gas usage really displaying coal in electricity production? Let's look at the actual data from EIA, for the past 12 years, for an answer. The data table is below:
From row 2 of the table, it is evident that coal generation is essentially flat and only dent slightly in the most recent three years, due to the financial crisis.
Natural gas usage did go up significantly, but it did not display coal, it just brings up the total electricity generated. More over, usage of natural gas goes up in proportion to the NG capacity going up. The NG turbines' usage rate, defined as percentage of hours of running, remains some where around 28% and does not go up. Neither is usage rate of coal units going down much.
This debunks the notion of Paul Santos that utilities are trying to run NG units more often and coal units less often in an effort to switch more coal usage to natural gas. That did NOT happen.
What happened is over the years more NG units are installed expanding the ability to burn more natural gas. However that is a long term slow process, and expanded natural gas usage does not displace coal. The existing coal units are still used, not sit idled.