Quote of the Day
Always do sober what you said you'd do drunk. That will teach you to keep your mouth shut.
— Ernest Hemingway
Introduction
Figure 1: Sherco Coal-Fired Power Plant in Minnesota (Wikipedia).
Because of where I work and live, I regularly wait at train-road crossings while coal trains pass in front of me. I get bored while sitting there and I start to think about the amount of coal that is being consumed by one of our local coal-fired power plant known as Sherburne County Generating Station or Sherco for short. I will present my estimates here and show that they agree with the numbers our local power producer is stating for this plant.
Background
Sherco Power Plant Trivia
We need to know two things about the Sherco plant to obtain some useful results:
- Nameplate capacity of 2,129 MW (source).
The nameplate capacity is the intended, sustained full-load capacity. No plants run at full capacity all the time.
- The plant uses over 9 million tons of coal per year (source).
I will assume an average daily consumption based 9 million tons divided by 365 days.
Coal Energy Density
The Sherco plant uses coal from the Powder River Basin, which straddles Montana and Wyoming. The coal from this region is referred to as sub-bituminous coal. On average, this coal generates 8500 BTU/lb of coal. This form of coal does not have have the energy density of other forms of coal (e.g. anthracite has an energy density of ~14000 BTU/lb). Sub-bituminous coal has the advantage of being plentiful, cheap, and relatively near.
Train Characteristics
Figure 2: Steel Coal Car (source).
Figure 2 shows the typical coal car that I seepass by me nearly every day. According to BNSF, each of these cars carries 102 tons of coal – I will assume that all of them are full.
A coal train typically has 115 of these coal cars – I have been so bored as to count these cars. If you want more details, see this document.
Analysis
Figure 3 shows my analysis of the number of train cars and trains needed per day to fuel the Sherco power plant. It needs between two and three trains of 115 cars each to supply enough coal to meet their stated specifications. My calculated range of daily train arrivals agrees with their written documentation.
Figure 3: My Estimate of the Number of Trains Per Day Into the Sherco Power Plant.
Conclusion
I can easily believe that between 2 and 3 coal trains service this power plant every day – I seem to wait for a train every five or six trips over the tracks.