The Great Silence
Unless you’ve been living under a rock, you know that Enemalta ran into… a slight hitch, when a wayward anchor severed a cable it was using to import around 200MW of electricity. In the candlelit silence that followed, attention shifted to the Electrogas operated Delimara 4 powerstation. Enemalta’s initial refusal to comment didn’t help, and as so often happens, facts die in a vacuum, and wild conspiracies take hold.
Some shared ominous insider information of out of order turbines that would take months to repair. Others said the tanker was nothing more than a prop, afloat and empty. The inherent complexities of power generation and distribution add to the noise and confusion. Save for a handful of engineers who work in the industry and rarely comment, it’s often one unfounded opinion versus another, so unless you have an impartial source, the truth might remain elusive. But this being 2020, data probably exists somewhere if we look hard enough.
To Thy Emissions Stay True
Electrogas have a pretty informative and interesting website. One page that particularly caught my eye was about emissions monitoring, probably to comply with some environmental directive. The Continuous Emissions Monitoring System keeps track of four emissions types across three chimneys. The Delimara 4 site is nothing more than three Siemens jet engines mounted horizontally. Each turbine provides 50MW of electricity. It’s the emissions of these turbines that we’ll be examining.
The assumption I’m making is that emissions are directly indicative of power generation when it comes to these three gas turbines. Another part of the system is a 60MW steam turbine powered by steam that’s generated from the heat of the first three turbines – this we have no way of gauging using this approach.
Now, Electrogas’s turbines burn LNG, which is relatively clean. In fact, according to General Electric, which manufactures its fair share of turbines: “particulate matter is generally considered negligible when burning natural gas. Thus, NOx and possibly CO are the only emissions of significance when combusting natural gas in combustion turbines.”
So now that we know for what to look, let’s import the data!
The data consists of hourly observations of milligrams of nitrogen oxide at each of the three chimneys. Each row is an hour. I added a fifth logical column called status, which codes “Off” if emissions are missing or 0 or “On” otherwise.
I imported two years of data, spanning from 4th of January 2018 to 23rd December 2019. Plotted out simply over time, we end up with the below time series.