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Homework 6: Electric Grid

ENE 505

Due Thursday, October 19, 2023

In this homework you will be exploring data from the California Independent System Operator (CAISO), which oversees the operation of California’s electric power grid. You will need the following two files, downloaded for you from CAISO.com:

- CAISO-supply-20230526.csv – a dataset of the resources making up California’s electricity supply curve in units of MW at 5-minute intervals, for 05/26/2023.

- CAISO-co2-per-resource-20230526.csv – a dataset of the CO2 emissions by resource of California’s electricity supply in units of mTCO₂/h (metric tonnes of CO₂ per hour) at 5-minute intervals, for 05/26/2023.

You will need to hand in your excel sheet, Jupyter Notebook, or whatever else you use to complete the assignment, along with the answers to questions in this Word document for full credit.

1) Download both data files included as part of the HW.

2) Plot a time series of the supply dataset showing each resource as a curve with a different color on the same plot. Include the following elements: [25 pt.]

a. A descriptive title

b. Axis labels (don’t forget units where appropriate!)

c. A legend. Make sure your legend is not overlapping with the curves (you may need to make the plot larger or specify a location for the legend).

d. 1-hour increments for the x-ticks

3) From your supply dataset, calculate and plot a time series of “Average CAISO Emissions” in units of metric tons of CO₂ versus time for the 24-hour period. You should have an emissions calculation for each 5-minute period for your plotted data. Use the following emissions factors: [25 pt.]

a. Coal: 1051 kg CO₂ per MWh

b. Natural gas: 441.5 kg CO₂ per MWh

c. Petroleum: 726.1 kg CO₂ per MWh

Assume 0 kg CO₂ per MWh for all other resources, and that Imports are made up of 10% coal, 20% natural gas, and 70% renewable generation. Make a plot in the same style as the graph in question 2, reporting emissions as metric tons of CO₂. To get full credit, each chart should have a title, y-axis label, and x-axis label. Pay attention to your units!

4) At what time on May 26^th were the emissions the lowest? What were the emissions at this time? Why were the emissions so low? [5pts]

5) At what time on May 26^th were the emissions the highest? What were the emissions at this time? Why were the emissions so high? [5pts]

6) You may have noticed that on both the supply and emissions graphs you have plotted, some curves become negative during certain hours. Comment on what this represents both in terms of supply and of emissions. What is causing this trend? [10 pt.]

7) From the last plot, it is apparent that only two sources have emissions curves that show any emissions during this period. Compare this to the emissions data estimated by CAISO (from the second dataset provided) by creating a line plot where you show calculated vs CAISO emissions curves for both resources. Make sure your plot contains: [10 pt.]

a. 2 dashed lines representing the calculated emissions (found in question 3)

b. 2 continuous lines representing the CAISO estimated emissions (from the second .csv)

c. Appropriate labels, titles and legend

Also, note that the lines for each resource should both have the same color!

8) Based upon your plot above, comment on whether the assumption regarding the emissions of imports from question 3) was accurate. Are imports less or more emission-intensive than was assumed? [5 pt.]

9) Notice that, in the CAISO estimated emissions data, there are other sources of emissions other than the two sources you have calculated. Calculate the total emissions at each timestep and create a scatter plot of total calculated emissions (y-axis) versus total CAISO estimated emissions (x-axis). In addition to including a title and axis legends, make sure you: [10 pt.]

a. Use ‘x’ as the markers for the scatter plot

b. Add line of best fit in a color of your choice

10) Calculate the correlation between CAISO estimated total emissions and the calculated emissions. What does this value suggest? Why is the value not 1? (email TA for a hint) [5 pt.]